WEBVTT 00:00:09.050 --> 00:00:16.010 There were a couple of areas that have been discussed a little bit, which I wanted to 00:00:16.010 --> 00:00:22.480 elaborate on because I think it is significant. 00:00:22.480 --> 00:00:27.119 One of them relates to intact aborts. 00:00:27.119 --> 00:00:33.320 The question of a crew escape system and whether that should be automated, whether the crew 00:00:33.320 --> 00:00:38.460 should have control and what is required if you actually have the crew take control. 00:00:38.460 --> 00:00:45.460 I think Chris Kraft gave an interesting perspective with the idea that because of the difficulties, 00:00:49.690 --> 00:00:56.690 or given the requirements, really, the impossibility of incorporating a capsule escape system for 00:00:57.960 --> 00:01:04.959 the Shuttle, the project basically took the point of view that the Shuttle itself was 00:01:06.280 --> 00:01:12.400 the escape pod, which means that you have to recover the Shuttle intact regardless of 00:01:12.400 --> 00:01:13.840 any engine failures. 00:01:13.840 --> 00:01:20.370 Now that, of course, requires 100% reliability of the solid rocket boosters which we never 00:01:20.370 --> 00:01:24.980 did achieve with Challenger. 00:01:24.980 --> 00:01:30.020 Although, of course, had we operated it within its spec limits it might be another story. 00:01:30.020 --> 00:01:36.520 But, in any case, I want to go through some of the details of a return to launch site 00:01:36.520 --> 00:01:43.520 abort and then I will describe an incident which occurred on our last flight to give 00:01:45.380 --> 00:01:52.289 you an idea of what is involved in the actual operation of abort modes. 00:01:52.289 --> 00:01:59.180 The idea is you have the two solid rocket boosters which have to light. 00:01:59.180 --> 00:02:00.690 And they are going to perform no matter what. 00:02:00.690 --> 00:02:06.460 If one of those boosters doesn't light and the other does it is a bad day. 00:02:06.460 --> 00:02:07.290 What can you say? 00:02:07.290 --> 00:02:13.030 And, obviously, if one of them fails during flight it is a bad day. 00:02:13.030 --> 00:02:20.030 And, which was more of a design problem, if they don't tail off at just the identical 00:02:21.530 --> 00:02:28.530 rate so that you get asymmetric thrust greater than a certain capability of the Shuttle to 00:02:28.560 --> 00:02:30.810 control, you have had a bad day. 00:02:30.810 --> 00:02:37.810 And because of the requirement to have symmetric thrust, I don't think if this was discussed 00:02:38.420 --> 00:02:44.760 before, when the solid rocket boosters are poured, they mix a batch of propellant sort 00:02:44.760 --> 00:02:47.720 of like you mix bread dough. 00:02:47.720 --> 00:02:54.720 And then they pour the propellant into both the left and the right booster segments at 00:02:54.829 --> 00:03:01.510 the same time so each booster segment has the identical batch of propellant in it. 00:03:01.510 --> 00:03:05.990 It may not be the same from the bottom to the top, but it is the same from the left 00:03:05.990 --> 00:03:06.810 to the right. 00:03:06.810 --> 00:03:08.850 And that is critical. 00:03:08.850 --> 00:03:13.950 And then they always reserve a certain proportion of the propellant. 00:03:13.950 --> 00:03:20.950 And they do tests on that to make sure that there are no process control problems. 00:03:23.209 --> 00:03:26.220 OK. 00:03:26.220 --> 00:03:31.410 You still need the three main engines to have enough thrust. 00:03:31.410 --> 00:03:38.180 The boosters each give you about 2.5 million pounds thrust, so that is about five million 00:03:38.180 --> 00:03:40.310 pounds to get off the ground. 00:03:40.310 --> 00:03:45.680 These give you about a half a million pound thrust at vacuum, four hundred and some odd 00:03:45.680 --> 00:03:49.230 thousand pounds thrust, so still over a million pounds thrust. 00:03:49.230 --> 00:03:55.880 And, of course, the problem you have during first stage is you have big gravity losses. 00:03:55.880 --> 00:04:02.880 The Shuttle on the pad weighs about 5.5 million pounds with all the propellant. 00:04:03.130 --> 00:04:08.709 If you don't fire your main engines you are barely going to lift off the ground. 00:04:08.709 --> 00:04:12.620 Actually, I guess it is a little bit less than five million pounds. 00:04:12.620 --> 00:04:19.620 But, in any case, without the three main engines firing you don't have enough thrust to get 00:04:21.349 --> 00:04:21.728 into orbit. 00:04:21.728 --> 00:04:28.729 Now, remember we talked about for deorbit burn, normally we fire both OMS engines. 00:04:30.599 --> 00:04:35.900 If one of the OMS engines is out you can fire one engine for twice as long. 00:04:35.900 --> 00:04:41.710 Or, if they are both out, you can fire the four RCS thrusters for twice as long again. 00:04:41.710 --> 00:04:48.110 Because you are in orbit, you are weightless, you don't have gravity losses, so firing half 00:04:48.110 --> 00:04:52.169 as many engines for twice as long is completely equivalent. 00:04:52.169 --> 00:04:54.499 When you are taking off against gravity that is not true. 00:04:54.499 --> 00:04:59.949 I mean if you only have five million pounds of thrust for a five million pound payload 00:04:59.949 --> 00:05:02.979 you are just going to sit on the pad and burn all your fuel. 00:05:02.979 --> 00:05:03.449 OK. 00:05:03.449 --> 00:05:07.139 You need your three engines. 00:05:07.139 --> 00:05:14.139 And, in fact, another interesting point, the attachment between the external tank and the 00:05:14.610 --> 00:05:21.610 Shuttle, that is stressed to assume that you have at least one engine burning. 00:05:23.289 --> 00:05:29.990 They tell me that if the Shuttle took off with just the solid boosters and you didn't 00:05:29.990 --> 00:05:36.710 have any thrust, sort of keeping the Shuttle up with the external tank, that the structural 00:05:36.710 --> 00:05:37.979 attachment points would fail. 00:05:37.979 --> 00:05:41.249 Anyway, you need your engines. 00:05:41.249 --> 00:05:47.569 What happens if you lose an engine early on? 00:05:47.569 --> 00:05:54.569 If you are far enough into the launch, you are over the main gravity loss segment usually 00:05:54.740 --> 00:05:58.659 starting at about 3.5 to 4 minutes into launch. 00:05:58.659 --> 00:06:05.339 If you lose one engine you can make it over the ocean, And that is called a Trans-Atlantic 00:06:05.339 --> 00:06:05.830 Abort. 00:06:05.830 --> 00:06:10.779 And, when you do that, you are basically flying upside down. 00:06:10.779 --> 00:06:16.639 You will do a roll maneuver, drop your external tank and come in and land. 00:06:16.639 --> 00:06:23.639 And you are basically going in the same direction which is nice when you are flying a rocket. 00:06:24.369 --> 00:06:26.119 These things are hard to turn around. 00:06:26.119 --> 00:06:30.259 But if you are going to do a return to launch site abort that is exactly what you have to 00:06:30.259 --> 00:06:31.219 do. 00:06:31.219 --> 00:06:38.219 So, this is a procedure that has been analyzed to death in many, many computer simulations. 00:06:39.949 --> 00:06:45.099 The basic procedure is you take off and you lose an engine. 00:06:45.099 --> 00:06:52.099 Now, it doesn't matter when you lose an engine in the first 2.5 minutes. 00:06:52.889 --> 00:06:56.909 You don't do anything while the solid rocket boosters are firing. 00:06:56.909 --> 00:07:00.779 They basically have open loop guidance. 00:07:00.779 --> 00:07:07.149 There is a certain projector programmed in and you cannot readjust that trajectory with 00:07:07.149 --> 00:07:12.389 a closed loop guidance solution to accommodate for any sort of a malfunction. 00:07:12.389 --> 00:07:14.969 So, you don't even declare an RTLS abort. 00:07:14.969 --> 00:07:21.969 And that, by the way, is done by the crew punching a button which essentially is a protected 00:07:22.710 --> 00:07:24.389 button. 00:07:24.389 --> 00:07:25.490 You punch that. 00:07:25.490 --> 00:07:31.069 And you can also do it via a computer input if something goes wrong with the button. 00:07:31.069 --> 00:07:34.569 You declare an RTLS abort after SRB separation. 00:07:34.569 --> 00:07:41.249 Immediately what happens is your trajectory increases because you want to gain altitude, 00:07:41.249 --> 00:07:42.899 and you will see why in a minute. 00:07:42.899 --> 00:07:49.899 But what happens now is you've got a pretty hefty downrange velocity already and you have 00:07:51.550 --> 00:07:54.879 got to turn around and come back. 00:07:54.879 --> 00:08:01.879 You have also got to worry about the disposal of your external tank. 00:08:02.179 --> 00:08:07.300 If you turn around and you come back, you are still burning your engines, you are still 00:08:07.300 --> 00:08:12.399 riding your tank, and you don't want the tank coming down on Melbourne or Disney World or 00:08:12.399 --> 00:08:13.860 anything like that. 00:08:13.860 --> 00:08:15.679 The basic procedure is as follows. 00:08:15.679 --> 00:08:22.679 You are going out, you loft your trajectory a bit, once you get far enough out now what 00:08:26.339 --> 00:08:28.969 you do is you do a powered pitch around. 00:08:28.969 --> 00:08:32.029 A very sporty maneuver. 00:08:32.029 --> 00:08:34.210 The external tank is here. 00:08:34.210 --> 00:08:41.210 Now you are flying backwards into your plume and everybody has speculated on what that 00:08:41.299 --> 00:08:44.049 would actually look like. 00:08:44.049 --> 00:08:47.930 Now you are flying backwards decelerating. 00:08:47.930 --> 00:08:51.440 And, as you decelerate, of course, gravity is starting to push you down so you've got 00:08:51.440 --> 00:08:58.440 to increase your pitch velocity until finally you basically have no more horizontal velocity 00:08:59.750 --> 00:09:05.730 and are just sitting statically on top of your exhaust. 00:09:05.730 --> 00:09:12.459 And now you gradually pitch forward and you start to fly back. 00:09:12.459 --> 00:09:18.810 Again, you have got to plan your trajectory so that when you drop the tank it is going 00:09:18.810 --> 00:09:20.649 to come down in the ocean. 00:09:20.649 --> 00:09:26.220 And then, if all that goes well, now you enter the heading alignment circle. 00:09:26.220 --> 00:09:33.180 And, of course, you are a heavy weight vehicle because you also, in the process of the RTLS, 00:09:33.180 --> 00:09:39.130 dump your OMS tanks and your RCS propellant so that you want to make sure you are as light 00:09:39.130 --> 00:09:39.829 as possible. 00:09:39.829 --> 00:09:46.829 Plus, in case you have any problem with landing you don't want your hypergolic propellant 00:09:47.649 --> 00:09:49.190 tanks to rupture. 00:09:49.190 --> 00:09:54.769 If all that goes well, now you enter the heading alignment circle and you have hopefully a 00:09:54.769 --> 00:09:56.209 nominal landing. 00:09:56.209 --> 00:10:03.209 As I say, this has been analyzed in high-fidelity dynamic simulations. 00:10:04.399 --> 00:10:07.180 The crew practices it over and over again. 00:10:07.180 --> 00:10:09.690 Everybody knows the procedures. 00:10:09.690 --> 00:10:16.370 Nobody wants to be the first crew to try this out. 00:10:16.370 --> 00:10:22.750 Before STS-1, you remember we talked about how there were lots of problems with the tiles 00:10:22.750 --> 00:10:24.459 falling off. 00:10:24.459 --> 00:10:30.209 I remember one of the people very high up in NASA, I don't remember if it was the administrator 00:10:30.209 --> 00:10:36.879 or one of the deputies, suggested that maybe the safest thing to do would be to do a planned 00:10:36.879 --> 00:10:43.250 RTLS because an RTLS, of course, you don't get up to those high velocities. 00:10:43.250 --> 00:10:44.870 And so you don't have any thermal problems. 00:10:44.870 --> 00:10:50.360 And so if a whole bunch of tiles had fallen off on the launch pad you could safely do 00:10:50.360 --> 00:10:51.579 an RTLS. 00:10:51.579 --> 00:10:58.000 Well, obviously, they did not appreciate the difficulties of doing an RTLS and that suggestion 00:10:58.000 --> 00:10:59.100 was not taken up. 00:10:59.100 --> 00:11:06.100 We basically decided we were not going to fly until we had confidence that the tiles 00:11:07.639 --> 00:11:10.069 were going to stay on. 00:11:10.069 --> 00:11:17.069 Cut forward to February of 1996, which was my fifth and final Shuttle flight. 00:11:17.379 --> 00:11:22.779 I was the second flight engineer so I was sitting right behind the pilot who is responsible 00:11:22.779 --> 00:11:24.170 for the main engine performance. 00:11:24.170 --> 00:11:31.170 Now, I should tell you, we have had, in the course of the 114 Shuttle flights we have 00:11:31.399 --> 00:11:35.899 had four pad shutdowns, pad aborts. 00:11:35.899 --> 00:11:38.430 And I think we talked about that briefly. 00:11:38.430 --> 00:11:45.430 The main engines turn on six seconds before the solids. 00:11:45.500 --> 00:11:47.420 Just reviewing that does two things. 00:11:47.420 --> 00:11:53.860 It gives the engines time to come up to full thrust and then you can perform checks on 00:11:53.860 --> 00:11:59.430 them to make sure that they are operating properly before you commit yourself to flight. 00:11:59.430 --> 00:12:05.689 And, of course, it gives time, because of the asymmetric thrust, for what we call the 00:12:05.689 --> 00:12:10.040 "twang" that the whole Shuttle stack goes forward and then back. 00:12:10.040 --> 00:12:12.589 And then, when you get to the vertical, you light the boosters. 00:12:12.589 --> 00:12:17.980 In fact, when they had the first test firing on the pad before STS-1, one of the reasons 00:12:17.980 --> 00:12:24.009 that they wanted to do that, in addition to just confirming that everything was working 00:12:24.009 --> 00:12:27.399 right, is they really wanted precise timing on the twang. 00:12:27.399 --> 00:12:31.089 People had calculated it, but that is not something you want to get wrong. 00:12:31.089 --> 00:12:37.709 So, they wanted an experimental verification. 00:12:37.709 --> 00:12:44.709 Of the four pad shutdowns, two of them were caused by instrumentation and two of them 00:12:45.139 --> 00:12:46.899 were real engine problems. 00:12:46.899 --> 00:12:52.230 I remember the first one was the last flight before what would have been my first flight 00:12:52.230 --> 00:12:56.720 back in 1984. 00:12:56.720 --> 00:13:01.050 And the main engine cutoff is called MECO. 00:13:01.050 --> 00:13:07.170 So, 8.5 minutes into the flight. 00:13:07.170 --> 00:13:14.170 After they had a pad abort the flight engineer called to Mission Control we have MECO, somehow 00:13:16.800 --> 00:13:18.529 I thought we would be a little bit higher. 00:13:18.529 --> 00:13:25.319 And, of course, when that happens now you've got to pull all the engines out, take them 00:13:25.319 --> 00:13:30.779 back to the shop, bring in new engines and it is about a two or three week stand down. 00:13:30.779 --> 00:13:32.149 And the crew has to go back to Houston. 00:13:32.149 --> 00:13:36.160 And, of course, all of your friends and family are there and they have to go home. 00:13:36.160 --> 00:13:38.670 It is no fun. 00:13:38.670 --> 00:13:40.939 I mean nobody complains if it is safe. 00:13:40.939 --> 00:13:47.939 We're sitting on the pad, we're counting down and everything was on schedule. 00:13:49.379 --> 00:13:54.139 In fact, the first of my five flights it had zero problems, zero delays. 00:13:54.139 --> 00:13:58.240 We were going on the day that was predicted on the time. 00:13:58.240 --> 00:14:02.949 Countdown to six seconds. 00:14:02.949 --> 00:14:04.220 You can feel the engines. 00:14:04.220 --> 00:14:05.339 Everything starts to rumble. 00:14:05.339 --> 00:14:07.800 The engines start up. 00:14:07.800 --> 00:14:14.800 There is what we call a steam gage, a vertical bar which shows the engine power. 00:14:17.579 --> 00:14:19.319 Center and right engines come up to 100%. 00:14:19.319 --> 00:14:22.850 The left engine comes up to 40%. 00:14:22.850 --> 00:14:24.699 The pilot calls out left engine at 40%. 00:14:24.699 --> 00:14:30.220 In times like this, your mind is working pretty fast. 00:14:30.220 --> 00:14:37.220 I remember thinking to myself oh, damn, we are going to have a pad shutdown, we have 00:14:38.629 --> 00:14:43.800 got to go back to Houston and back to the simulators. 00:14:43.800 --> 00:14:47.800 I mean stupid things to be thinking about at that time, but that is sort of the way 00:14:47.800 --> 00:14:48.310 it works. 00:14:48.310 --> 00:14:51.689 And all of a sudden kaboom. 00:14:51.689 --> 00:14:54.730 I feel this big kick in my back. 00:14:54.730 --> 00:14:56.269 The solids have lit. 00:14:56.269 --> 00:14:57.699 What in the hell is going on? 00:14:57.699 --> 00:14:59.589 We were supposed to have a pad abort. 00:14:59.589 --> 00:15:04.490 Now we are going with an engine. 00:15:04.490 --> 00:15:11.490 And, actually, when you are going through maximum dynamic pressure, max q, the engines 00:15:12.470 --> 00:15:15.310 throttle down to about 65%. 00:15:15.310 --> 00:15:19.480 And there is a malfunction if one of your engines gets stuck it is called getting stuck 00:15:19.480 --> 00:15:21.019 in the thrust bucket. 00:15:21.019 --> 00:15:25.199 If it doesn't come back to full power you are RTLS abort. 00:15:25.199 --> 00:15:29.180 Well, we were taking off with one engine at 40%. 00:15:29.180 --> 00:15:36.180 It sort of dawned on me that we were going to be the first crew to do an RTLS, so at 00:15:39.829 --> 00:15:42.249 that point I start going through my checklists. 00:15:42.249 --> 00:15:49.249 And the pilot calls to the ground we have ignition, left engine at 40%. 00:15:50.550 --> 00:15:57.550 And so, for about the first 15 seconds or so, I just had barely time to get out the 00:15:57.829 --> 00:16:01.029 RTLS checklist and start getting ready to read the procedures. 00:16:01.029 --> 00:16:06.459 And then it turns out that the ground has more insight than the crew does. 00:16:06.459 --> 00:16:12.670 And it turns out that there are several sensors, one of which feeds that gauge. 00:16:12.670 --> 00:16:15.670 But, in fact, that sensor had gone bad. 00:16:15.670 --> 00:16:20.899 And, in fact, the left engine was performing nominally and the ground was able to confirm 00:16:20.899 --> 00:16:26.209 that both by the other sensors and by looking at the acceleration. 00:16:26.209 --> 00:16:29.470 And so, everything was OK, I put away the checklist and enjoyed the ride. 00:16:29.470 --> 00:16:34.300 But, first of all, it was kind of a scary situation. 00:16:34.300 --> 00:16:36.029 But it also shows the difficulty. 00:16:36.029 --> 00:16:43.029 Now, suppose we, as the crew, had been responsible for declaring an abort. 00:16:44.069 --> 00:16:50.990 If you are going to build in a system where this is the crew's responsibility then you 00:16:50.990 --> 00:16:57.850 better design your instrumentation so that the crew has all the instrumentation required 00:16:57.850 --> 00:17:01.059 to make that decision correctly. 00:17:01.059 --> 00:17:08.059 Similarly, if this were to be an automatic abort, you've got to have failure detection, 00:17:12.069 --> 00:17:17.109 identification, reconfiguration. 00:17:17.109 --> 00:17:24.050 The last thing you want is to go into an abort situation when you don't have to because there 00:17:24.050 --> 00:17:31.050 is no way that an abort is going to be anywhere near as safe as a nominal mission. 00:17:38.090 --> 00:17:40.740 Obviously, it's just a good story now. 00:17:40.740 --> 00:17:47.740 But I think it does have something to inform about how you are going to have to design 00:17:48.680 --> 00:17:49.840 abort systems. 00:17:49.840 --> 00:17:56.840 And, as both Aaron Cohen and Chris Kraft said, although the astronauts always felt comfortable 00:17:59.440 --> 00:18:04.340 with their abort system but I am not sure that all the people in Mission Control were 00:18:04.340 --> 00:18:08.510 quite so comfortable knowing the things that might go wrong with it. 00:18:08.510 --> 00:18:15.510 And, in fact, as he said, they always breathe a sigh of relief after first stage when the 00:18:15.920 --> 00:18:20.290 abort rocket would detach and fire itself away. 00:18:20.290 --> 00:18:20.750 Yeah. 00:18:20.750 --> 00:18:27.750 If one of the engines is not working or not working properly, I guess the other two engines 00:18:28.880 --> 00:18:32.240 try to do the work [NOISE OBSCURES]. 00:18:32.240 --> 00:18:38.060 Well, they certainly will throttle up to 109% if they need to, but they cannot make up for 00:18:38.060 --> 00:18:42.540 the first engine when you're in the first stage and you have lots of gravity losses. 00:18:42.540 --> 00:18:49.540 In fact, when you get, like I said, to about 3.5, 4 minutes then you have enough altitude 00:18:52.390 --> 00:18:54.670 and downrange velocity to make it across. 00:18:54.670 --> 00:19:01.670 And then at some point you get to the situation where you basically gained your altitude. 00:19:02.440 --> 00:19:07.630 And, although you are not at orbital velocity yet so you still have some gravity losses, 00:19:07.630 --> 00:19:14.630 the gravity losses are small enough that if you have a loss of an engine you can still 00:19:15.260 --> 00:19:17.280 make it to a lower orbit. 00:19:17.280 --> 00:19:21.250 That is called abort to orbit, ATO. 00:19:21.250 --> 00:19:28.250 And you will hear the call press to ATO means that you can now make it to a lower orbit 00:19:30.630 --> 00:19:33.520 which is the safest thing to do with two engines. 00:19:33.520 --> 00:19:39.120 And then a little bit later on you will hear like single engine TAL which means if you 00:19:39.120 --> 00:19:43.120 lose two engines with only one engine you can make it across the Atlantic. 00:19:43.120 --> 00:19:48.140 And then later on you will hear single engine ATO and then finally single engine. 00:19:48.140 --> 00:19:52.300 Then you will also hear press to MECO which means at this point if you lose an engine 00:19:52.300 --> 00:19:54.230 you can make it through your nominal orbit. 00:19:54.230 --> 00:19:59.560 And usually about the last call a single engine press to MECO which means even if you lose 00:19:59.560 --> 00:20:02.880 two engines you can still make it to MECO. 00:20:02.880 --> 00:20:09.880 What happens then if there 00:20:21.110 --> 00:20:23.520 is an instrumentation problem [NOISE OBSCURES]? 00:20:23.520 --> 00:20:30.520 The crew will never declare an abort on their own because it is just realized that the ground 00:20:31.910 --> 00:20:33.140 has so much more information. 00:20:33.140 --> 00:20:36.330 The only exception is if you lose comm. 00:20:36.330 --> 00:20:41.210 If we had lost comm. 00:20:41.210 --> 00:20:48.210 and we saw our engine at 40%, I mean there were a few other displays which the pilot 00:20:48.390 --> 00:20:50.180 was starting to call up. 00:20:50.180 --> 00:20:56.110 And it could be that he would have figured it out perhaps, perhaps not, but that is the 00:20:56.110 --> 00:21:00.840 only circumstance under which the crew would make that call. 00:21:00.840 --> 00:21:04.230 There was abort at some stage. 00:21:04.230 --> 00:21:06.120 What happened to that? 00:21:06.120 --> 00:21:08.180 Did they manage to make it [OVERLAPPING VOICES]? 00:21:08.180 --> 00:21:09.490 I was trying to remember. 00:21:09.490 --> 00:21:12.840 Did I talk about that in class? 00:21:12.840 --> 00:21:19.840 Well, all right, I will run through that because it was, again, a very interesting story. 00:21:19.950 --> 00:21:25.790 The things that you are afraid about is that if things go back in a hurry in an engine 00:21:25.790 --> 00:21:27.580 that an engine can actually blow up. 00:21:27.580 --> 00:21:30.930 And it is one thing if an engine gets shutdown. 00:21:30.930 --> 00:21:32.690 Now you are just flying on two engines. 00:21:32.690 --> 00:21:38.950 But if an engine blows up and takes out your whole rear section you have had a bad day. 00:21:38.950 --> 00:21:45.950 The instrumentation is biased towards an early shutdown. 00:21:46.220 --> 00:21:50.070 If you sense that something has gone wrong shut it down. 00:21:50.070 --> 00:21:53.660 We have got intact aborts. 00:21:53.660 --> 00:21:59.700 Better to err on the side of safety, even if that might potentially put you into an 00:21:59.700 --> 00:22:00.710 abort situation. 00:22:00.710 --> 00:22:07.710 And I am trying to exactly reconstruct it. 00:22:08.860 --> 00:22:15.860 The thing is that if you lose one engine now you are abort ATO. 00:22:19.650 --> 00:22:26.650 Now, if you lose a second engine you might be in a situation where certainly you cannot 00:22:28.470 --> 00:22:30.410 make it to orbit. 00:22:30.410 --> 00:22:34.950 And, because you have changed your trajectory, you might not be able to make it to a good 00:22:34.950 --> 00:22:37.220 Trans-Atlantic landing site. 00:22:37.220 --> 00:22:44.220 So, at that point, if you have lost one engine there is a switch on the center console where 00:22:48.600 --> 00:22:52.040 you can override the engine shutdown command. 00:22:52.040 --> 00:22:59.040 What you are now saying is we are in an unsurvivable situation if we only have one engine. 00:23:00.230 --> 00:23:07.230 And, therefore, we will take the extra chance of getting an instrumentation caused engine 00:23:07.720 --> 00:23:08.300 shutdown. 00:23:08.300 --> 00:23:14.110 We are not going to take that chance so we are going to disable the ability of instrumentation 00:23:14.110 --> 00:23:18.530 to shut down the engine and we will just take our chances. 00:23:18.530 --> 00:23:21.240 The ground will continue the calculation. 00:23:21.240 --> 00:23:25.570 And, as soon as you get to the point where you have the capability of doing a single 00:23:25.570 --> 00:23:31.840 engine TAL or a single engine abort to orbit, you re-enable the instrumentation. 00:23:31.840 --> 00:23:38.840 What happened is the Shuttle launched. 00:23:40.990 --> 00:23:47.860 It must have been about 4 or 5 minutes into launch because they lost an engine, it shut 00:23:47.860 --> 00:23:54.860 down automatically, they are now abort to orbit lower orbit, but they were abort to 00:23:55.150 --> 00:23:56.240 orbit. 00:23:56.240 --> 00:23:59.970 Take the switch, put it to inhibit. 00:23:59.970 --> 00:24:05.420 Now, the main propulsion flight controller was very good. 00:24:05.420 --> 00:24:12.420 She realized right away that it was an instrumentation problem because sometimes you can see certain 00:24:12.710 --> 00:24:17.090 trends or you see things change in a way that tells you that this is not the way a real 00:24:17.090 --> 00:24:21.720 engine behaves, that this is more typical of instrumentation. 00:24:21.720 --> 00:24:24.910 She suspected she had an instrumentation problem. 00:24:24.910 --> 00:24:30.910 Now they get a little further along in the launch where they could have potentially done 00:24:30.910 --> 00:24:37.850 -- They were too far to land in the normal TAL sites which were in the daytime on the 00:24:37.850 --> 00:24:44.550 West Coast of Africa, but they could have made a nighttime landing at some emergency 00:24:44.550 --> 00:24:49.380 airport in the Congo, I think it was, if they had lost another engine. 00:24:49.380 --> 00:24:56.380 But, by the flight rules, they take the switch back to enable so that now, because you can 00:24:58.410 --> 00:25:05.410 "safely" lose a second engine you want to protect yourself against an explosive situation. 00:25:05.580 --> 00:25:07.640 So, now they are enabled. 00:25:07.640 --> 00:25:13.400 Now the flight controller sees that the instrumentation on one of the other two engines is starting 00:25:13.400 --> 00:25:16.910 to go back the way the first one was. 00:25:16.910 --> 00:25:23.440 And she realized that in about 15 seconds that engine was going to shut down so she 00:25:23.440 --> 00:25:29.820 immediately called the flight director and said flight, take the switch back to inhibit. 00:25:29.820 --> 00:25:35.790 And this is where the discipline becomes very important, luckily flight didn't get into 00:25:35.790 --> 00:25:40.940 a long involved discussion about why do you want to do that, what is going on, but just 00:25:40.940 --> 00:25:46.160 said CAPCOM engine switch to inhibit. 00:25:46.160 --> 00:25:47.270 They took it. 00:25:47.270 --> 00:25:51.570 And sure enough the instrumentation went bad but the engine was OK. 00:25:51.570 --> 00:25:53.400 They got to orbit. 00:25:53.400 --> 00:25:56.640 Then they used some of their OMS propellant to raise their orbit a little bit. 00:25:56.640 --> 00:25:58.490 That was a Spacelab mission. 00:25:58.490 --> 00:26:00.100 And they had a good mission. 00:26:00.100 --> 00:26:06.360 But the flight controller actually won a big award for that because she really saved the 00:26:06.360 --> 00:26:08.380 day. 00:26:08.380 --> 00:26:13.430 So, yeah, that is the closest we ever came to a real intact abort. 00:26:13.430 --> 00:26:14.070 Yeah. 00:26:14.070 --> 00:26:15.340 Two questions. 00:26:15.340 --> 00:26:20.340 The first one is going back to the return to launch site. 00:26:20.340 --> 00:26:22.880 Do all of the main engine propellant get used up before the tank gets dropped or do you 00:26:22.880 --> 00:26:26.820 not burn some of the propellant? 00:26:26.820 --> 00:26:28.270 You know, I don't know the answer to that. 00:26:28.270 --> 00:26:28.970 I don't. 00:26:28.970 --> 00:26:34.740 And the other one is on the pad, with your flight, wouldn't the sequencing computer shut 00:26:34.740 --> 00:26:37.400 down the other engines if it detected that one of them had failed? 00:26:37.400 --> 00:26:40.600 And so it must have used the good sensor. 00:26:40.600 --> 00:26:42.250 Yeah, that is right. 00:26:42.250 --> 00:26:47.210 And, luckily, our little gauge was just fed by one. 00:26:47.210 --> 00:26:51.440 And, in retrospect, you can say probably that's not a good way to design it but that is the 00:26:51.440 --> 00:26:52.100 way it was designed. 00:26:52.100 --> 00:26:52.850 You're right. 00:26:52.850 --> 00:26:59.450 If the engine controller senses with a majority or however they program it, I don't know the 00:26:59.450 --> 00:27:01.390 details of the guts of the software there. 00:27:01.390 --> 00:27:05.530 But if it is convinced that one of the engines is not working right it shuts down all three 00:27:05.530 --> 00:27:10.620 engines, which is what happened on four occasions. 00:27:10.620 --> 00:27:11.020 Yeah. 00:27:11.020 --> 00:27:18.020 When you talked about the forced pitch over in the return to launch site, was that just 00:27:21.900 --> 00:27:22.280 the gambling of the main engines that gives you that? 00:27:22.280 --> 00:27:23.770 Yeah, because you are off the solids at that point. 00:27:23.770 --> 00:27:24.700 And that is the thing. 00:27:24.700 --> 00:27:31.310 I mean with the solids there is such an enormous thrust and the aerodynamic loads are huge. 00:27:31.310 --> 00:27:35.500 You don't want to deviate from your planned trajectory because one of the things that 00:27:35.500 --> 00:27:40.980 they do is program in load relief for the aerodynamic surfaces. 00:27:40.980 --> 00:27:44.590 They take the day of winds launch. 00:27:44.590 --> 00:27:51.090 And, if you have wind shears or other atmospheric high jet streams that you are going to fly 00:27:51.090 --> 00:27:58.090 through, they actually program the elevons and the body flap to move in such a way as 00:27:58.790 --> 00:28:01.860 to relieve the aerodynamic loading on the wings. 00:28:01.860 --> 00:28:03.880 And that is preprogrammed in. 00:28:03.880 --> 00:28:05.950 It is not a closed loop. 00:28:05.950 --> 00:28:11.100 It is totally open loop so you don't want to change the trajectory once you've put all 00:28:11.100 --> 00:28:11.920 that load relief in. 00:28:11.920 --> 00:28:16.330 How long does that take? 00:28:16.330 --> 00:28:17.640 It's pretty quick. 00:28:17.640 --> 00:28:20.620 It's about ten seconds, if I remember from the simulator. 00:28:20.620 --> 00:28:25.270 It is a sporty maneuver, I will tell you. 00:28:25.270 --> 00:28:26.510 No RCS that goes into that? 00:28:26.510 --> 00:28:31.560 Oh, the RCS is trivial compared to what you're getting out. 00:28:31.560 --> 00:28:35.810 You've got 500,000 pounds coming out of each engine. 00:28:35.810 --> 00:28:42.810 The primary RCS is 750 pounds. 00:28:46.240 --> 00:28:51.630 But, like I said, they do then open up the RCS as you are flying back. 00:28:51.630 --> 00:28:56.510 And what they do is they open up all the engines so that you have symmetrical thrusts so that 00:28:56.510 --> 00:29:01.010 you are firing out of both sides. 00:29:01.010 --> 00:29:07.740 The idea is just to deplete the tanks as much as possible. 00:29:07.740 --> 00:29:14.740 The second technical area that I had been hoping that Al Louviere would get into and 00:29:16.620 --> 00:29:21.470 didn't have a chance to was the payload bay doors which are a fascinating mechanism. 00:29:21.470 --> 00:29:28.470 And it is also going to be a segue into EVA because it was a strange situation. 00:29:30.160 --> 00:29:34.700 It is kind of relate back to that now when you look at how many successful EVAs have 00:29:34.700 --> 00:29:39.650 been done and the Hubble repair and the building of Space Station and all the other things, 00:29:39.650 --> 00:29:46.650 but management at Johnson Space Center was not particularly friendly to EVA back in the 00:29:50.920 --> 00:29:51.830 `70s. 00:29:51.830 --> 00:29:55.480 I asked Chris Kraft about that. 00:29:55.480 --> 00:29:57.100 At first he denied it. 00:29:57.100 --> 00:29:59.320 He said well, I always liked EVA. 00:29:59.320 --> 00:30:04.510 He said well, maybe it was the management of the Astronaut Office that didn't like EVA. 00:30:04.510 --> 00:30:08.750 He did admit that Bob Gilruth who was the Director of Johnson Space Center at the time, 00:30:08.750 --> 00:30:14.620 this was when Chris Kraft was head of flight operations, definitely did not like EVA. 00:30:14.620 --> 00:30:15.350 He was afraid of it. 00:30:15.350 --> 00:30:22.350 He didn't think it was safe, despite the fact that back in 1973 EVA had saved the entire 00:30:23.760 --> 00:30:26.060 Skylab project. 00:30:26.060 --> 00:30:27.540 Hopefully most of you know that story. 00:30:27.540 --> 00:30:30.730 I know it is ancient history. 00:30:30.730 --> 00:30:37.530 And clearly we had done a lot of safe EVAs on the surface of the Moon, but basically 00:30:37.530 --> 00:30:44.530 EVA was looked at it was expensive, it was potentially hazardous. 00:30:44.860 --> 00:30:51.120 Given the things that the Shuttle was supposed to do in the original planning, mainly launch 00:30:51.120 --> 00:30:57.140 satellites, launch pieces of the Space Station, that went away, Launch Defense Department 00:30:57.140 --> 00:31:04.140 satellites, commercial satellites, EVA was not really part of the big picture in planning. 00:31:04.160 --> 00:31:11.160 And, although they did design an airlock for the Shuttle, there were real questions of 00:31:15.120 --> 00:31:17.170 how much preparation do we have to do for EVA? 00:31:17.170 --> 00:31:18.380 Do we really even need it? 00:31:18.380 --> 00:31:25.380 Maybe we could save some weight by not having space suits aboard. 00:31:39.990 --> 00:31:46.990 That is 00:32:02.030 --> 00:32:03.100 where we finally ended up. 00:32:03.100 --> 00:32:05.310 That is the Hubble Telescope. 00:32:05.310 --> 00:32:08.600 This is the side of the payload bay. 00:32:08.600 --> 00:32:11.930 I mean, obviously, EVA became a very successful activity. 00:32:11.930 --> 00:32:15.340 These are the payload bay doors. 00:32:15.340 --> 00:32:20.430 This is in the orbiter processing facility. 00:32:20.430 --> 00:32:27.430 And one of the things, well, I have a picture of closing the door. 00:32:28.730 --> 00:32:33.220 But the mechanism of these doors is extraordinary. 00:32:33.220 --> 00:32:38.480 There are two motors, one at the front and one at the back of each. 00:32:38.480 --> 00:32:44.810 Each of the motors has two drive units and they work through a differential so that if 00:32:44.810 --> 00:32:51.810 one of the motors fails the other one can still drive although at half the speed, just 00:32:52.270 --> 00:32:55.610 similar to the way a car works. 00:32:55.610 --> 00:33:00.740 There is a long torsion rod which runs the length of the Shuttle. 00:33:00.740 --> 00:33:05.130 And then that torsion rod is attached to these bars over here. 00:33:05.130 --> 00:33:11.510 And I am sorry the picture was scanned in and is not terribly sharp. 00:33:11.510 --> 00:33:18.510 As the torsion bar twists then these rods lift up the payload bay door and bring it 00:33:20.070 --> 00:33:21.250 to a close. 00:33:21.250 --> 00:33:26.090 The mechanism, this is the best picture I could find, you notice there is a strong back 00:33:26.090 --> 00:33:32.390 because, as was mentioned, the doors cannot support their own weight in 1G. 00:33:32.390 --> 00:33:39.390 But the system of latches here, you have to remember that the payload bay can expand and 00:33:39.520 --> 00:33:45.440 contract by several inches due to thermal environment. 00:33:45.440 --> 00:33:52.440 And so you have to design a latch system that can accommodate this thermal behavior. 00:33:53.930 --> 00:33:56.950 It was an incredible mechanical challenge. 00:33:56.950 --> 00:34:02.400 And the complexity of this system, I mean I am always amazed when I look at how the 00:34:02.400 --> 00:34:02.930 thing works. 00:34:02.930 --> 00:34:09.399 I have a schematic of them later, which you can look at, but basically you close the doors. 00:34:09.399 --> 00:34:14.280 And then the first thing you do is you want to close the latches on either end. 00:34:14.280 --> 00:34:16.349 And then there is also center line latches. 00:34:16.349 --> 00:34:22.239 And I think Al Louviere did discuss the fact that these payload bay doors are part of the 00:34:22.239 --> 00:34:26.399 structural element of the Shuttle during reentry. 00:34:26.399 --> 00:34:32.000 You cannot reenter if the doors are not just closed by latched. 00:34:32.000 --> 00:34:35.820 You need them latched for structural strength. 00:34:35.820 --> 00:34:42.820 There is a series of bollards here, little protrusions which these latches grab on. 00:34:44.330 --> 00:34:51.330 And they have designed the rigging of the rods such that the latches that are close 00:34:56.149 --> 00:35:02.420 to the hinge line actually close before the latches that are further away. 00:35:02.420 --> 00:35:09.100 It is a sequential closing of the latches all with a single mechanism so that basically 00:35:09.100 --> 00:35:16.100 you pull the part of the door that is closest to the torque rod, you latch that down first, 00:35:17.230 --> 00:35:21.510 and then it is kind of a zipper effect where then you pull it down so that even if the 00:35:21.510 --> 00:35:26.660 door is a little bit warped thermally you will get the door to close properly. 00:35:26.660 --> 00:35:33.660 You wouldn't want to close this latch first and then have the door in a situation where 00:35:33.720 --> 00:35:37.010 it was buckled out. 00:35:37.010 --> 00:35:41.180 And then, of course, the center line latch, because of the thermal expansion, you can 00:35:41.180 --> 00:35:44.480 have the doors coming together like that or like that. 00:35:44.480 --> 00:35:47.580 And you have got to have centerline latches that can accommodate for that. 00:35:47.580 --> 00:35:51.260 It is really quite an incredible design. 00:35:51.260 --> 00:35:55.520 And Al Louviere had said that he was going to talk about it, but he didn't have time 00:35:55.520 --> 00:35:59.270 to. 00:35:59.270 --> 00:36:04.380 There is plenty of redundancy in here because there are these double motors, but because 00:36:04.380 --> 00:36:11.380 this is so critical people started to look at suppose you have some degree stuck in the 00:36:11.850 --> 00:36:18.230 mechanism, it doesn't matter how many motors, you cannot get it closed. 00:36:18.230 --> 00:36:22.570 Suppose the motors jam on one side. 00:36:22.570 --> 00:36:25.600 Now the other motor is not going to be able to drive it. 00:36:25.600 --> 00:36:30.500 So, various things were done to allow for EVA intervention. 00:36:30.500 --> 00:36:34.600 And, in the early Shuttle flights, this was the only thing that the crew trained for with 00:36:34.600 --> 00:36:39.370 EVA, it was just payload bay door contingencies. 00:36:39.370 --> 00:36:46.370 For instance, the PDU, the drive unit, this is the payload bay door drive unit or PLBDU. 00:36:50.750 --> 00:36:54.230 That is what we call a nested acronym. 00:36:54.230 --> 00:36:56.730 That is part of the game there. 00:36:56.730 --> 00:37:00.760 You have to go out and actually peel away the liners of the payload bay. 00:37:00.760 --> 00:37:07.760 And inside here there is a little mechanism where you can insert a special tool and twist 00:37:09.000 --> 00:37:09.680 it. 00:37:09.680 --> 00:37:16.680 And that actually disconnects that motor drive unit from the torque so that it can turn freely. 00:37:19.560 --> 00:37:24.790 And I hope, when you look at these things, you will get some sense of the complexity 00:37:24.790 --> 00:37:26.680 of these mechanisms. 00:37:26.680 --> 00:37:33.680 And so what we do for training -- Of course they build mockups of this in the water and 00:37:34.000 --> 00:37:38.490 we also look at the real Shuttle down in Florida to actually see these units. 00:37:38.490 --> 00:37:42.890 And, for the people who are on the EVA crew, you spend a lot of time crawling around the 00:37:42.890 --> 00:37:47.810 payload bay getting intimately familiar with a lot of the actual mechanisms just in case 00:37:47.810 --> 00:37:54.810 you actually have to go out and do something with it. 00:37:54.880 --> 00:38:01.880 Then suppose the problem is not with the drive unit but that one of these latches get jammed 00:38:03.290 --> 00:38:03.860 up. 00:38:03.860 --> 00:38:06.350 This is actually a tube cutter. 00:38:06.350 --> 00:38:08.100 It is a little hard to see. 00:38:08.100 --> 00:38:11.690 I don't know if you are familiar with the things. 00:38:11.690 --> 00:38:12.480 They are on a ratchet. 00:38:12.480 --> 00:38:18.790 And, as it gradually cuts, you push the blade in bit by bit. 00:38:18.790 --> 00:38:20.500 And then eventually you cut away. 00:38:20.500 --> 00:38:27.280 And this gives you an idea that they just gave us a lot of tools, a pin extractor, a 00:38:27.280 --> 00:38:31.220 crowbar, vice grips, you name it. 00:38:31.220 --> 00:38:34.000 How much did that crowbar cost? 00:38:34.000 --> 00:38:38.660 Well, the crowbar probably cost about $10 at Sears. 00:38:38.660 --> 00:38:45.660 And then they had to put on all of the Velcro and the tethers to go in the tool thing, and 00:38:45.690 --> 00:38:47.860 that probably cost a few hundred dollars. 00:38:47.860 --> 00:38:50.890 And then they had to make a drawing of it, and you know how it goes. 00:38:50.890 --> 00:38:56.250 EVA is very expensive because everything has to be custom made. 00:38:56.250 --> 00:39:03.180 I mean that is one of the things that, because of the constraints of the suits and the gloves, 00:39:03.180 --> 00:39:07.750 you cannot, in most case, just use regular tools. 00:39:07.750 --> 00:39:10.300 And, as I say, everything is tethered. 00:39:10.300 --> 00:39:11.650 And I will show you pictures later. 00:39:11.650 --> 00:39:13.070 We have a little mini workstation. 00:39:13.070 --> 00:39:18.500 They built little receptacles on the side of the suit because it is a hard upper torso 00:39:18.500 --> 00:39:20.270 which can take a certain amount of load. 00:39:20.270 --> 00:39:25.310 And so you plug basically a tool caddy into your suit. 00:39:25.310 --> 00:39:28.800 And then you hang all of these tools on the tool caddy. 00:39:28.800 --> 00:39:35.070 And you will see some pictures later of how that works. 00:39:35.070 --> 00:39:42.070 If the motors don't work and you have now freed the doors so that the door can move 00:39:42.630 --> 00:39:49.630 but you have no motor to drive it, now we have a mechanical winch and a rope on it. 00:39:49.920 --> 00:39:55.750 And I'm not making this up. 00:39:55.750 --> 00:39:56.990 You actually run the rope up. 00:39:56.990 --> 00:40:00.820 These are the little bollards that the latches catch onto. 00:40:00.820 --> 00:40:06.030 You run the rope up over that and then you have to crawl out on the payload bay door, 00:40:06.030 --> 00:40:09.760 which would be a lot of fun, and attach it here. 00:40:09.760 --> 00:40:13.570 And then you actually wind it closed. 00:40:13.570 --> 00:40:14.750 And we do this in the water. 00:40:14.750 --> 00:40:16.840 I mean this is all fully mocked up. 00:40:16.840 --> 00:40:17.820 Yeah. 00:40:17.820 --> 00:40:23.090 What do you do if you have trouble opening the doors just after launch? 00:40:23.090 --> 00:40:28.630 Well, if you cannot open the doors then you come home. 00:40:28.630 --> 00:40:29.470 You wouldn't want to. 00:40:29.470 --> 00:40:33.400 I mean if there was something seriously wrong with the doors you better come home. 00:40:33.400 --> 00:40:38.180 Yeah, we can do this to get them closed. 00:40:38.180 --> 00:40:42.050 But you don't want to purposely put yourself in that situation if you know you have a problem 00:40:42.050 --> 00:40:43.530 beforehand. 00:40:43.530 --> 00:40:45.010 Yeah. 00:40:45.010 --> 00:40:47.980 [NOISE OBSCURES] 00:40:47.980 --> 00:40:50.180 We think it could be done with one person. 00:40:50.180 --> 00:40:51.730 Normally, we only go out with two. 00:40:51.730 --> 00:40:56.920 But in the orbital flight test, the first four flights only had two crew members. 00:40:56.920 --> 00:41:02.440 Was of them was EVA trained. 00:41:02.440 --> 00:41:07.750 And then what happens if you get the doors closed by the latches don't latch? 00:41:07.750 --> 00:41:13.570 They actually made latches that we could put on by hand. 00:41:13.570 --> 00:41:14.990 These are the latches for the side. 00:41:14.990 --> 00:41:21.560 And this is the schematic that sort of show the latches going on the orders in that order 00:41:21.560 --> 00:41:23.820 one, two, three and four. 00:41:23.820 --> 00:41:28.920 And, again, the way they designed this so that they actually close in sequence but you 00:41:28.920 --> 00:41:34.890 only have one drive unit is really just a beautiful mechanical system. 00:41:34.890 --> 00:41:41.320 But if they don't close then you take this, and I won't go into the details, but you have 00:41:41.320 --> 00:41:44.460 to spring it around at least two of those. 00:41:44.460 --> 00:41:48.460 And that will give you the structural strength to come home. 00:41:48.460 --> 00:41:54.510 And then if the center line latches don't close, again, you can look at the mechanism 00:41:54.510 --> 00:41:54.760 here. 00:41:54.670 --> 00:41:56.490 And they have yet a different tool. 00:41:56.490 --> 00:42:01.580 Now, this is actually shown on its side, but this is actually on the top. 00:42:01.580 --> 00:42:06.860 And this is a bitch in the water because, yeah, your suit is weightless but the tool 00:42:06.860 --> 00:42:07.740 is not. 00:42:07.740 --> 00:42:10.920 And so you are holding this tool. 00:42:10.920 --> 00:42:15.060 When you're holding the tool you want to sink to the bottom, and so you are trying to hold 00:42:15.060 --> 00:42:15.770 on with one hand. 00:42:15.770 --> 00:42:22.740 And you have a tether so you try to tie yourself to the top there so that you're kind of hanging 00:42:22.740 --> 00:42:23.300 on the tether. 00:42:23.300 --> 00:42:30.050 But then, depending on how your weigh out is, if you move this big tool back and forth 00:42:30.050 --> 00:42:32.680 your body is sort of rocking back and forth. 00:42:32.680 --> 00:42:36.390 And you are working above your head. 00:42:36.390 --> 00:42:39.510 I mean everybody has to do it. 00:42:39.510 --> 00:42:45.430 If you are going to be an EVA crew member and you cannot do this job you are disqualified. 00:42:45.430 --> 00:42:47.670 But nobody likes it. 00:42:47.670 --> 00:42:51.650 It is a real pain. 00:42:51.650 --> 00:42:56.010 That is basically how EVA got sold to the Shuttle System. 00:42:56.010 --> 00:43:02.140 I will show you a few pictures of general EVA activities to give you an idea of how 00:43:02.140 --> 00:43:03.150 the system works. 00:43:03.150 --> 00:43:10.150 And then I want to go into the question of the interaction between EVA and the pressurization 00:43:14.210 --> 00:43:18.560 and the environmental control system of the rest of the Shuttle because, again, this is 00:43:18.560 --> 00:43:20.050 a systems engineering problem. 00:43:20.050 --> 00:43:26.440 And you cannot, in most cases, do one thing without it having an impact on something else. 00:43:26.440 --> 00:43:31.369 I talked about doing all this training. 00:43:31.369 --> 00:43:37.780 Now we are stepping ten years into the future so that is training for the Hubble Telescope. 00:43:37.780 --> 00:43:43.540 And, actually, the telescope is so tall that we couldn't get the whole thing in. 00:43:43.540 --> 00:43:48.970 The pool wasn't deep enough so we had to actually cut it in half, and we would work on one half 00:43:48.970 --> 00:43:54.530 and then work on the other half. 00:43:54.530 --> 00:43:55.180 Here is an example. 00:43:55.180 --> 00:43:59.650 This is me installing the Wide Field/Planetary Camera. 00:43:59.650 --> 00:44:06.650 Now, the training, people normally see the water tank. 00:44:10.180 --> 00:44:11.130 You're not weightless. 00:44:11.130 --> 00:44:13.150 You all understand that. 00:44:13.150 --> 00:44:15.990 If you go upside down the blood rushes to your head. 00:44:15.990 --> 00:44:20.710 If you're holding onto tools, the tools will fall down. 00:44:20.710 --> 00:44:25.460 And of course you don't have these guys when you're out in space. 00:44:25.460 --> 00:44:32.460 Angels if you saw them out in space. 00:44:32.890 --> 00:44:39.890 If you're moving around large objects, they have resistance from the water, so you need 00:44:40.760 --> 00:44:45.940 to get a sense of how easy it is to push things around so you don't get things moving too 00:44:45.940 --> 00:44:46.630 fast. 00:44:46.630 --> 00:44:50.770 We also train on air bearing floors. 00:44:50.770 --> 00:44:55.930 This is a mass model of the Wiff-Pick. 00:44:55.930 --> 00:45:00.400 The same mass, moments of inertia. 00:45:00.400 --> 00:45:04.430 And I am up here on a weight relief system. 00:45:04.430 --> 00:45:08.220 And you can really get a sense of what it feels like. 00:45:08.220 --> 00:45:13.310 And so you are trying to build a kind of muscle memory so that when you get in space you are 00:45:13.310 --> 00:45:19.480 not trying to push things as hard as you push them in the water. 00:45:19.480 --> 00:45:23.980 And you also remember that if you want to stop something you also have to be able to 00:45:23.980 --> 00:45:25.040 exert a force on it. 00:45:25.040 --> 00:45:31.000 Whereas, in the water, all you have to do is stop pushing. 00:45:31.000 --> 00:45:33.970 Now we go into space and we are ready for the EVA. 00:45:33.970 --> 00:45:40.750 I will sort of take you through what is involved to give you a sense of the complexity of this 00:45:40.750 --> 00:45:43.470 system. 00:45:43.470 --> 00:45:46.450 First of all are tools. 00:45:46.450 --> 00:45:49.970 That is what I looked like before all the cosmic rays made my hair fall out. 00:45:49.970 --> 00:45:54.520 It is just one of the hazards of spaceflight. 00:45:54.520 --> 00:45:56.770 Here you see the kind of tool caddies. 00:45:56.770 --> 00:46:00.940 This is for a ratchet wrench. 00:46:00.940 --> 00:46:04.230 And we had about 250 different tools. 00:46:04.230 --> 00:46:08.280 About a hundred planned to use and the rest were for contingencies. 00:46:08.280 --> 00:46:10.440 And we had to take them all out. 00:46:10.440 --> 00:46:12.980 We call this our fish stringer. 00:46:12.980 --> 00:46:15.540 Sort of like a Portuguese fishermen. 00:46:15.540 --> 00:46:19.780 The fisher wives hang all the fish on the string and then hang them out. 00:46:19.780 --> 00:46:25.740 And then we take this out on the fish stringer. 00:46:25.740 --> 00:46:29.110 This is the airlock at launch. 00:46:29.110 --> 00:46:31.290 And it is totally packed. 00:46:31.290 --> 00:46:35.560 And, in fact, we had four spacesuits rather than the normal two so there wasn't a whole 00:46:35.560 --> 00:46:36.240 lot of room. 00:46:36.240 --> 00:46:41.619 And the first thing is you go and you start checking the various systems. 00:46:41.619 --> 00:46:48.619 And then you have to unpack everything and move it into the flight deck. 00:46:48.880 --> 00:46:49.650 That is Story. 00:46:49.650 --> 00:46:53.230 We went out together. 00:46:53.230 --> 00:46:55.450 This is the hard upper torso. 00:46:55.450 --> 00:47:01.750 This is looking down into the inside of the spacesuit. 00:47:01.750 --> 00:47:08.410 The back of the spacesuit there is battery and lithium hydroxide CO2 scrubber. 00:47:08.410 --> 00:47:12.850 The CO2 scrubber has to be replaced after every EVA. 00:47:12.850 --> 00:47:16.980 It is good for about 12 hours. 00:47:16.980 --> 00:47:22.350 And normally if you're only going out once you don't worry about recharging the batteries, 00:47:22.350 --> 00:47:28.660 but since we were doing successive every day EVAs we would have to take the batteries out 00:47:28.660 --> 00:47:29.800 every night and charge them. 00:47:29.800 --> 00:47:32.990 Take the ones that had been charged and put them into the suits that are going to go out 00:47:32.990 --> 00:47:34.200 the next day. 00:47:34.200 --> 00:47:39.470 And just keeping track of which cartridges have been used and which batteries have been 00:47:39.470 --> 00:47:46.470 charged and how much, I mean there is a tremendous amount of overhead effort just in managing 00:47:46.780 --> 00:47:48.890 all of this equipment. 00:47:48.890 --> 00:47:55.890 And we had practiced doing this a lot on the ground, as you can imagine, before we went 00:47:56.540 --> 00:47:57.350 up. 00:47:57.350 --> 00:48:00.150 The morning of the EVA. 00:48:00.150 --> 00:48:06.140 You get up early and eat as big a breakfast as you can because you are not going to get 00:48:06.140 --> 00:48:09.330 much to eat for the next eight hours. 00:48:09.330 --> 00:48:12.710 These are radiation monitors. 00:48:12.710 --> 00:48:17.100 For Hubble we were actually up at about 600 kilometers, which is as high as the Shuttle 00:48:17.100 --> 00:48:24.100 ever goes, so we got really the highest radiation dose that you can get on the Shuttle on a 00:48:25.320 --> 00:48:25.920 normal mission. 00:48:25.920 --> 00:48:30.930 It was about between one and two REMs which is no big health problem. 00:48:30.930 --> 00:48:37.930 But typically the dose on a Shuttle flight at a more typical 300 kilometers is more like 00:48:38.480 --> 00:48:43.590 tens or maybe a little over 100 milliREMs. 00:48:43.590 --> 00:48:45.930 They did want us to take the radiation monitor. 00:48:45.930 --> 00:48:47.460 Now we are in the mid-deck. 00:48:47.460 --> 00:48:52.690 And when you see these pictures you get a sense of when you're doing an EVA the entire 00:48:52.690 --> 00:48:55.190 middeck is just full of stuff. 00:48:55.190 --> 00:48:58.580 I mean there is so much equipment. 00:48:58.580 --> 00:49:05.580 You've got the pants units floating over there, plus the two extra suits and all of the auxiliary 00:49:05.640 --> 00:49:06.530 equipment. 00:49:06.530 --> 00:49:09.730 You try to keep things organized. 00:49:09.730 --> 00:49:16.730 Then for thermal control, the original Apollo spacesuits were designed for daytime use on 00:49:20.020 --> 00:49:21.980 the Moon when it is very hot. 00:49:21.980 --> 00:49:26.880 And, in addition, people are walking so they are putting a lot of metabolic heat into the 00:49:26.880 --> 00:49:27.550 suit. 00:49:27.550 --> 00:49:33.080 And so they were very concerned about being able to have sufficient cooling. 00:49:33.080 --> 00:49:38.080 They developed a very, very efficient sublimator cooling unit. 00:49:38.080 --> 00:49:45.080 You have a little layer of ice that is continually fed from the bottom and it is sublimates. 00:49:45.160 --> 00:49:46.820 That basically is how you get rid of your heat. 00:49:46.820 --> 00:49:51.900 And then you run your cooling water underneath that ice and it cools off. 00:49:51.900 --> 00:49:58.050 And then it is run through what they call LCVG, liquid cooling and ventilation garment 00:49:58.050 --> 00:50:05.050 which has lots of Tygon tubing that goes through it so that it carries the cold water next 00:50:05.950 --> 00:50:06.550 to your skin. 00:50:06.550 --> 00:50:13.550 And also the oxygen that comes into the suit comes through the helmet over the back of 00:50:14.500 --> 00:50:18.920 your head so it flows over your face so you breathe the fresh oxygen. 00:50:18.920 --> 00:50:25.920 But you would like to get ventilation through the entire suit so you don't build up lots 00:50:26.640 --> 00:50:28.950 of humidity in your arms and legs. 00:50:28.950 --> 00:50:34.600 What you do is the return valve actually comes through these air ducts. 00:50:34.600 --> 00:50:40.420 And so the return is picked up at the bottom of your arms and at the bottom of your legs. 00:50:40.420 --> 00:50:45.580 That insures that the air does get circulated through your arms and legs. 00:50:45.580 --> 00:50:52.580 But when we started doing Shuttle EVAs metabolically you are not nearly as stressed. 00:50:54.390 --> 00:51:01.340 Plus, you spend almost half your time in the dark and it gets really, really cold. 00:51:01.340 --> 00:51:08.340 And this has been a constant problem. 00:51:09.350 --> 00:51:14.630 And here is an interesting systems problem to show how everything relates to one another. 00:51:14.630 --> 00:51:20.420 We were very concerned about when you open up the doors of the Hubble Telescope, if direct 00:51:20.420 --> 00:51:27.420 sunlight comes in, it will cause an out-gassing of the internal material which could pollute 00:51:28.720 --> 00:51:30.170 the ultraviolet mirrors. 00:51:30.170 --> 00:51:37.170 The ultraviolet optics are very, very sensitive to organic contamination, so under no circumstances 00:51:37.970 --> 00:51:42.500 could we have sunlight penetrating the interior of the telescope. 00:51:42.500 --> 00:51:47.300 But we were going to be spending a lot of time with the doors open, so how do you insure 00:51:47.300 --> 00:51:50.340 that you will never get the sun coming in? 00:51:50.340 --> 00:51:56.619 Well, the Hubble Telescope is sitting up here like this. 00:51:56.619 --> 00:52:01.900 If that is the sun, just make sure that the belly of the orbiter is always pointed towards 00:52:01.900 --> 00:52:02.290 the sun. 00:52:02.290 --> 00:52:06.800 Then you never have to worry about sun coming into the telescope. 00:52:06.800 --> 00:52:13.170 But what you do have to worry about is that, well, during the dayside of your orbit, if 00:52:13.170 --> 00:52:18.030 the sun is over here and the earth is over here, during the day your payload bay is going 00:52:18.030 --> 00:52:19.580 to be pointed towards the earth. 00:52:19.580 --> 00:52:25.960 And so, you basically have a radiative heat exchange with something that is at about 20 00:52:25.960 --> 00:52:26.750 degrees C. 00:52:26.750 --> 00:52:27.350 No big deal. 00:52:27.350 --> 00:52:33.220 If you go around the other side now, you at nighttime, you're pointed at deep space. 00:52:33.220 --> 00:52:37.450 And so you're radiating towards absolute zero or three degrees Kelvin. 00:52:37.450 --> 00:52:40.290 And that is a concern. 00:52:40.290 --> 00:52:41.260 And you get very cold. 00:52:41.260 --> 00:52:48.260 They were predicting temperatures of as much as 150 below zero Celsius. 00:52:49.580 --> 00:52:55.480 We were very concerned not only were our hands going to get cold but some of our tools might 00:52:55.480 --> 00:52:57.980 not work. 00:52:57.980 --> 00:53:04.980 We pushed very hard for a test in a thermal vacuum chamber. 00:53:05.050 --> 00:53:10.020 Our tools are stored in a toolbox outside in the cargo bay. 00:53:10.020 --> 00:53:15.210 And we wanted to go through going out and taking the tools out. 00:53:15.210 --> 00:53:22.210 And, of course, they are held in there because they have launch locks so there are little 00:53:22.290 --> 00:53:27.940 pit pins and latching mechanisms that you have to remove so that you can get the tools 00:53:27.940 --> 00:53:28.850 out. 00:53:28.850 --> 00:53:30.619 I went in to do the first test. 00:53:30.619 --> 00:53:32.320 And it is a vacuum chamber. 00:53:32.320 --> 00:53:33.520 And the walls are painted black. 00:53:33.520 --> 00:53:38.450 And they can run liquid nitrogen through the vacuum chamber. 00:53:38.450 --> 00:53:42.790 And they could cool it down to the lowest temperatures that we were expecting to experience. 00:53:42.790 --> 00:53:49.790 I opened up the toolbox and about 75% of the tools the launch release mechanisms were just 00:53:50.840 --> 00:53:51.570 frozen shut. 00:53:51.570 --> 00:53:52.980 I couldn't get them out. 00:53:52.980 --> 00:53:55.510 So, that started to get people's attention. 00:53:55.510 --> 00:53:59.820 They sent the engineers in to redo some of the tolerance. 00:53:59.820 --> 00:54:04.220 They played around with the lubrication a little bit. 00:54:04.220 --> 00:54:11.220 Then Story went in a week later to do his run and he was able to get most of the tools 00:54:12.490 --> 00:54:12.990 out. 00:54:12.990 --> 00:54:19.030 I think he got all the tools out, actually, because I was only in for a few hours. 00:54:19.030 --> 00:54:21.830 Because once we realized that it wasn't working I came out. 00:54:21.830 --> 00:54:24.790 He was in there. 00:54:24.790 --> 00:54:29.660 I remember he said at one point just holding onto these tools my hands are really, really 00:54:29.660 --> 00:54:30.160 cold. 00:54:30.160 --> 00:54:31.470 I don't know. 00:54:31.470 --> 00:54:33.920 About an hour or so later someone asked him how his hands were. 00:54:33.920 --> 00:54:36.369 He said oh, they are fine, they've warmed up. 00:54:36.369 --> 00:54:39.750 Well, Story is from the South. 00:54:39.750 --> 00:54:44.920 Those of you with experience in winter know that if your hands are really cold and after 00:54:44.920 --> 00:54:48.920 a while you don't feel them anymore, it doesn't necessarily mean that they have warmed up. 00:54:48.920 --> 00:54:53.510 When they took him out of the chamber his hands were deep purplish black and he had 00:54:53.510 --> 00:55:00.510 severe frostbite to the point where they sent him up to Alaska to some frostbite specialists. 00:55:01.790 --> 00:55:03.160 In the end, he was very fortunate. 00:55:03.160 --> 00:55:07.190 He got off with no major permanent damage and was able to fly. 00:55:07.190 --> 00:55:10.700 But, as you can imagine, that got serious management attention. 00:55:10.700 --> 00:55:14.270 So, gloves now have electrical heating units in them. 00:55:14.270 --> 00:55:17.080 But we didn't have that available. 00:55:17.080 --> 00:55:24.080 What we had to do was to change the attitude profile so that we were basically pointing 00:55:25.090 --> 00:55:26.750 towards the earth. 00:55:26.750 --> 00:55:29.730 Now, that is generally OK. 00:55:29.730 --> 00:55:35.470 If you are pointing towards the earth and the sun is coming from your belly you are 00:55:35.470 --> 00:55:42.470 not going to hurt the Shuttle, but a quarter way around the earth you do have the possibility 00:55:44.430 --> 00:55:49.540 now that the sun is going to hit the telescope. 00:55:49.540 --> 00:55:56.540 What they had to do was to do two attitude maneuvers every orbit in order to basically 00:56:02.260 --> 00:56:05.580 keep us in a more benign thermal attitude for the EVA. 00:56:05.580 --> 00:56:12.349 But to prevent the sun from shinning on the telescope. 00:56:12.349 --> 00:56:17.040 And we didn't the reaction control system propellant budget to support that. 00:56:17.040 --> 00:56:20.910 Remember we were going into a high orbit which meant we needed to use a lot of OMS fuel to 00:56:20.910 --> 00:56:21.990 get up there? 00:56:21.990 --> 00:56:26.599 And we needed a lot of propellant for the deorbit because the higher you are the more 00:56:26.599 --> 00:56:29.520 you have to burn to get down. 00:56:29.520 --> 00:56:36.520 And so the flight control community, together with the pilots got together and developed 00:56:40.240 --> 00:56:45.460 a special way that we could do maneuvers using only half the number of jets that you normally 00:56:45.460 --> 00:56:46.940 use. 00:56:46.940 --> 00:56:53.940 And so this is an interconnection between the thermal environment of EVA and the reaction 00:56:55.280 --> 00:57:00.109 control propellant budget which nobody in the early days of flight planning would ever 00:57:00.109 --> 00:57:02.650 have believed that there is this sort of connection. 00:57:02.650 --> 00:57:07.710 But it is just another good example of how these systems all play with one another and 00:57:07.710 --> 00:57:11.880 you cannot make changes in one without another. 00:57:11.880 --> 00:57:16.130 I am going to finish this unit and then we will take a little break and then I will do 00:57:16.130 --> 00:57:16.960 the last part. 00:57:16.960 --> 00:57:20.470 The process of getting in the suit. 00:57:20.470 --> 00:57:24.640 First you get in LTA, lower torso assembly, basically the pants. 00:57:24.640 --> 00:57:29.320 And, of course, this is one time when you can put your pants on both legs at a time. 00:57:29.320 --> 00:57:30.910 You cannot do that too often. 00:57:30.910 --> 00:57:35.670 But, again, look at the middeck here. 00:57:35.670 --> 00:57:36.740 It is full. 00:57:36.740 --> 00:57:39.760 This, by the way, is the escape pole. 00:57:39.760 --> 00:57:41.970 We talked about this earlier. 00:57:41.970 --> 00:57:48.970 During launch and entry it is actually bolted into position so that it will take you out 00:57:49.790 --> 00:57:55.760 the door, but once you are in orbit you just sort of float it up and out of the way and 00:57:55.760 --> 00:57:57.800 it just kind of Velcroed to the ceiling. 00:57:57.800 --> 00:58:01.980 And, of course, it has no weight up there so it is perfectly happy. 00:58:01.980 --> 00:58:04.230 You get in the pants. 00:58:04.230 --> 00:58:11.109 Now, the upper torso of the suit is attached to the wall inside the airlock. 00:58:11.109 --> 00:58:14.300 Now you have to float into the airlock. 00:58:14.300 --> 00:58:16.390 And that is what you're looking at when you're getting into the suit. 00:58:16.390 --> 00:58:17.950 There are a lot of connections you have to make. 00:58:17.950 --> 00:58:20.619 This is the water bag. 00:58:20.619 --> 00:58:22.830 This is the comm. 00:58:22.830 --> 00:58:26.030 connection for your Snoopy cap. 00:58:26.030 --> 00:58:32.530 This is the water and air connection which you have to hook into your LCBG. 00:58:32.530 --> 00:58:34.690 And these are the arms that you have to get into. 00:58:34.690 --> 00:58:41.690 And the problem in the design here is your shoulders are wider than your chest. 00:58:46.859 --> 00:58:52.900 When you are actually inside the suit you want the distance between these two arms to 00:58:52.900 --> 00:58:55.170 be conformal with your armpits. 00:58:55.170 --> 00:59:00.060 Because, if it is out here that cuts way down on your mobility. 00:59:00.060 --> 00:59:04.650 But if it is too narrow you cannot get into it. 00:59:04.650 --> 00:59:08.359 That is the basic design problem in this sort of a suit. 00:59:08.359 --> 00:59:15.359 Now, the Russians have a rear entry suit that doesn't have that problem. 00:59:16.020 --> 00:59:19.910 It is always a challenge and you really have to push and struggle to get in. 00:59:19.910 --> 00:59:26.910 Eventually they wanted to design this suit so that one person could get in by themselves, 00:59:28.480 --> 00:59:29.770 but it cannot be done. 00:59:29.770 --> 00:59:36.770 I mean you can get in like this but you just cannot pull up the waist ring and attach it 00:59:37.310 --> 00:59:38.670 by yourself. 00:59:38.670 --> 00:59:40.510 Nobody has been able to do that. 00:59:40.510 --> 00:59:46.450 It is a great feeling of accomplishment when you finally get inside. 00:59:46.450 --> 00:59:50.220 Then you put your helmet on. 00:59:50.220 --> 00:59:53.790 Now you're starting to see what we are dealing with because we have to take all this stuff 00:59:53.790 --> 00:59:58.010 outside in addition to the tools that are already outside. 00:59:58.010 --> 01:00:00.910 These are the plugs which we put the mini work station. 01:00:00.910 --> 01:00:07.910 We haven't put it on quite yet but it is just a whole bunch of equipment which you have 01:00:08.510 --> 01:00:10.230 to manage. 01:00:10.230 --> 01:00:16.980 At this point we purge the suit with an oxygen flow. 01:00:16.980 --> 01:00:23.980 Now, remember, we are at an atmospheric pressure, or almost an atmospheric pressure, I will 01:00:25.340 --> 01:00:31.070 get into that later, of pure oxygen, so that also puts very serious flammability constraints. 01:00:31.070 --> 01:00:35.670 Although, when you go outside, you are only at 4 psi. 01:00:35.670 --> 01:00:38.619 When you are inside here you are at the full cabin pressure. 01:00:38.619 --> 01:00:44.180 Actually, in order to do your leap check you have to go to 4 psi above cabin pressure. 01:00:44.180 --> 01:00:50.030 You are actually working at above one atmosphere of pressure of pure oxygen, so that is a very 01:00:50.030 --> 01:00:54.040 serious flammability design constraint. 01:00:54.040 --> 01:01:01.040 And we have to sit and breathe pure oxygen then for about 40 minutes to get the nitrogen 01:01:01.880 --> 01:01:02.670 out of our blood. 01:01:02.670 --> 01:01:06.810 And, again, I will be discussing this whole atmospheric and bends problem. 01:01:06.810 --> 01:01:13.560 But, if you don't, when you drop down to 4 psi, the nitrogen in your blood bubbles out 01:01:13.560 --> 01:01:20.560 and you get the bends, just like a diver who comes up too fast from a dive. 01:01:21.180 --> 01:01:25.540 Just one or two pictures of what went on outside. 01:01:25.540 --> 01:01:27.560 There is Hubble. 01:01:27.560 --> 01:01:29.099 I was changing some fuels there. 01:01:29.099 --> 01:01:31.609 It was kind of neat working underneath the solar panel. 01:01:31.609 --> 01:01:34.940 Those were the old ones which we took off and replaced the next day. 01:01:34.940 --> 01:01:39.460 But you have to be really careful because you don't want to bang against it. 01:01:39.460 --> 01:01:44.470 And, of course, you cannot see above your head, so we always have other people looking 01:01:44.470 --> 01:01:44.760 at us. 01:01:44.760 --> 01:01:49.640 This is the kind of situation where if you had a little heads up display where you could 01:01:49.640 --> 01:01:53.960 get this sort of a view to show what you're really doing it would really improve your 01:01:53.960 --> 01:01:55.140 situational awareness. 01:01:55.140 --> 01:01:58.869 But, at the moment, we don't have that. 01:01:58.869 --> 01:02:04.140 It takes not just the people outside but the people inside paying full attention, reading 01:02:04.140 --> 01:02:04.910 procedures. 01:02:04.910 --> 01:02:11.910 Historically, we carried all of our procedures on a cuff checklist, like so. 01:02:14.680 --> 01:02:18.970 But the procedures for Hubble and some of the other flights are so complex that you 01:02:18.970 --> 01:02:19.630 just cannot do it. 01:02:19.630 --> 01:02:24.250 So, nowadays, these are just emergency procedures. 01:02:24.250 --> 01:02:25.820 I will pass this around. 01:02:25.820 --> 01:02:31.490 I would like it back. 01:02:31.490 --> 01:02:32.210 Let's see. 01:02:32.210 --> 01:02:39.210 After putting in the new Wiff-Pick, ground had to do some tests on it, so I got Claude 01:02:40.119 --> 01:02:41.950 to fly me out over the arm. 01:02:41.950 --> 01:02:46.099 And we had one of the old Lunar Hasselblad cameras which they let us carry. 01:02:46.099 --> 01:02:53.099 Normally, we just use Nikons on the Shuttle, but they let us take a Hasselblad. 01:02:53.660 --> 01:02:57.930 That gives a view of what the payload bay looks like EVA. 01:02:57.930 --> 01:03:02.140 Here is Story over here working on one of the other things. 01:03:02.140 --> 01:03:05.050 The Earth is not flat, don't worry about the picture. 01:03:05.050 --> 01:03:12.050 I went around it many times. 01:03:12.270 --> 01:03:19.270 And, I mean, some parts of EVA, I really should share it because it just gets really spectacular. 01:03:19.609 --> 01:03:25.140 This is about 50 feet, I don't know whether to say above or below or whatever of the Shuttle, 01:03:25.140 --> 01:03:28.400 but you're just out there in the middle of nowhere. 01:03:28.400 --> 01:03:31.400 And, at this point, I was the free-floater. 01:03:31.400 --> 01:03:35.119 One of the people is always attached to the end of the arm, which is good when you have 01:03:35.119 --> 01:03:39.760 to move around big pieces of equipment because now you can react the forces with your feet. 01:03:39.760 --> 01:03:46.119 When you are a free-floater either you're in a foot restraint, which limits your mobility, 01:03:46.119 --> 01:03:51.960 or one hand has to actually be holding you so that you can react forces. 01:03:51.960 --> 01:03:58.960 Of course, we are attached by a waste tether, which is then attached to a long real of stainless 01:04:02.450 --> 01:04:02.940 steel. 01:04:02.940 --> 01:04:09.180 But you can set it so that the springiness is taken out. 01:04:09.180 --> 01:04:14.650 And so I could basically, and I did from time to time, must sort of let go. 01:04:14.650 --> 01:04:21.650 And it is a really neat feeling because once you convince yourself that you're not going 01:04:21.660 --> 01:04:28.619 to fall down, which I'm enough of a physicist to understand the orbital mechanics, but, 01:04:28.619 --> 01:04:33.869 nevertheless, the first time I let go it was an interesting feeling. 01:04:33.869 --> 01:04:38.380 The thing is when you're holding onto something, whether by your feet or your hands, of course 01:04:38.380 --> 01:04:44.910 the Shuttle is so much more massive that you feel yourself physically related. 01:04:44.910 --> 01:04:46.450 You are controlled by the Shuttle. 01:04:46.450 --> 01:04:49.589 And so the Shuttle is your point of reference. 01:04:49.589 --> 01:04:53.410 Maybe the Shuttle is in orbit but you are attached to the Shuttle. 01:04:53.410 --> 01:04:57.529 As soon as I let go, the physics totally changes. 01:04:57.529 --> 01:05:01.930 And it was really this transformation into being a human satellite. 01:05:01.930 --> 01:05:04.220 I mean I really felt like I was a satellite now. 01:05:04.220 --> 01:05:05.609 I wasn't attached to the Shuttle. 01:05:05.609 --> 01:05:11.520 And sometimes, if I could turn around before I let go so I didn't see the Shuttle, it was 01:05:11.520 --> 01:05:15.500 really kind of neat, especially at night, just sort of floating there and all the stars 01:05:15.500 --> 01:05:15.940 and everything. 01:05:15.940 --> 01:05:16.260 Yeah. 01:05:16.260 --> 01:05:22.060 Do they build in time for you to be able to kind of do that kind of thing? 01:05:22.060 --> 01:05:24.240 No, they don't build in the time. 01:05:24.240 --> 01:05:31.240 But, like in this case, two days before on Story's and my last EVA we had replaced -- Not 01:05:31.730 --> 01:05:33.109 replaced. 01:05:33.109 --> 01:05:34.720 These are the magnetometers up at the top. 01:05:34.720 --> 01:05:41.720 The gross maneuvering of Hubble is done by reaction wheels, but the reaction wheels, 01:05:43.060 --> 01:05:46.500 when they get spinning too fast, you have to be able to desaturate them so they have 01:05:46.500 --> 01:05:52.300 magnetic torquers, these long torque rods which create a magnetic field. 01:05:52.300 --> 01:05:58.670 There are no jets on Hubble because it would cause pollution of the optics, so you need 01:05:58.670 --> 01:06:04.849 magnetometers up at the top to sense the magnetic field in order to operate the torquers. 01:06:04.849 --> 01:06:08.349 The magnetometers were never designed to be replaced. 01:06:08.349 --> 01:06:09.609 They weren't supposed to fail. 01:06:09.609 --> 01:06:13.660 Well, both of them failed in the first couple of years. 01:06:13.660 --> 01:06:18.950 We couldn't take them off so they designed two new magnetometers that we could actually 01:06:18.950 --> 01:06:21.779 insert and bolt on, on top of the old ones. 01:06:21.779 --> 01:06:27.520 And then we took the electrical and data connections and hooked them up. 01:06:27.520 --> 01:06:33.940 But I noticed on that day -- We were very concerned with quality control. 01:06:33.940 --> 01:06:38.270 First of all, that we didn't break anything that wasn't already broken but also to look 01:06:38.270 --> 01:06:45.029 for any signs of damage because, you know, this was a telescope that was supposed to 01:06:45.029 --> 01:06:47.839 be maintained. 01:06:47.839 --> 01:06:51.910 We saw a little bit of paint chipping off the outside of the old magnetometers. 01:06:51.910 --> 01:06:58.029 They were concerned that they might float around and get into the optics. 01:06:58.029 --> 01:07:04.630 We went into the payload bay the next day, the other EVA team, and they cut off some 01:07:04.630 --> 01:07:09.490 of this gold insulation material from one of the thermal enclosures that some of the 01:07:09.490 --> 01:07:11.000 equipment was in. 01:07:11.000 --> 01:07:13.330 And I'm not supposed to stand in front. 01:07:13.330 --> 01:07:18.580 I keep forgetting that. 01:07:18.580 --> 01:07:24.500 We made those covers, and then we had to go up and install them. 01:07:24.500 --> 01:07:31.500 But, actually, after we installed them then the ground wanted photographic documentation. 01:07:34.180 --> 01:07:35.089 We took pictures. 01:07:35.089 --> 01:07:40.180 And then the crew inside got their telephoto lenses and they took a lot of pictures. 01:07:40.180 --> 01:07:44.500 And then they got the television camera on the end of the arm to take pictures. 01:07:44.500 --> 01:07:49.930 And so, during all that time, you do have a little bit of free time just to sort of 01:07:49.930 --> 01:07:51.050 enjoy the environment. 01:07:51.050 --> 01:07:53.960 It would be a shame not to because it is such a spectacular place. 01:07:53.960 --> 01:07:54.359 Yeah. 01:07:54.359 --> 01:08:00.490 How do you work when there is not light when you're on the dark side. 01:08:00.490 --> 01:08:03.660 Let me turn the laser pointer on here. 01:08:03.660 --> 01:08:05.910 Oh, no, what did I do? 01:08:05.910 --> 01:08:12.910 That is a good time for a break, right? 01:08:13.160 --> 01:08:18.179 Take a two-minute break. 01:08:18.179 --> 01:08:24.439 And then, of course, when the sun rises you know it so you can turn your lights off. 01:08:24.439 --> 01:08:26.670 OK. 01:08:26.670 --> 01:08:33.670 I talked about the necessity of doing a nitrogen purge and pre-breathing oxygen to get the 01:08:34.339 --> 01:08:35.429 nitrogen out of your blood. 01:08:35.429 --> 01:08:42.158 This turns out to be an interesting systems problem because it doesn't just affect the 01:08:42.158 --> 01:08:47.238 suit, it affects the spacecraft. 01:08:47.238 --> 01:08:51.279 Those of you who were here at the beginning saw I was blowing up a balloon which unfortunately 01:08:51.279 --> 01:08:52.670 popped. 01:08:52.670 --> 01:08:59.670 It was only to make the point that you can look at a spacesuit, the arms and legs, cylindrical. 01:08:59.959 --> 01:09:02.219 It is like one of those balloons. 01:09:02.219 --> 01:09:08.118 And when you try to bend the balloon it doesn't like to stay bent because you are compressing 01:09:08.118 --> 01:09:14.389 the gas and you're doing elastic work on the material of the balloon and it wants to snap 01:09:14.389 --> 01:09:14.729 back. 01:09:14.729 --> 01:09:17.190 And spacesuits basically work the same way. 01:09:17.190 --> 01:09:23.618 The old-fashioned pressure suits that test pilots used to wear, which were the genesis 01:09:23.618 --> 01:09:27.399 of the original Mercury suits, they basically stiffen you. 01:09:27.399 --> 01:09:31.448 And, in fact, the launch entry suits that we use on the Shuttle are not designed for 01:09:31.448 --> 01:09:32.259 joint mobility. 01:09:32.259 --> 01:09:35.109 They are just pressurized. 01:09:35.109 --> 01:09:41.599 And we do a pressure check before the mission when we're getting suited up. 01:09:41.599 --> 01:09:47.029 And they blow it up and you just go like that. 01:09:47.029 --> 01:09:50.499 You can move a little bit, you know, enough so that if you're sitting in your seat with 01:09:50.499 --> 01:09:56.820 a seatbelt holding you in form so that your waist is bent, you can move your arms enough 01:09:56.820 --> 01:09:57.789 to get to the controls. 01:09:57.789 --> 01:10:01.420 But I certainly wouldn't want to try and go out and do any useful work in that. 01:10:01.420 --> 01:10:08.420 It has really been an extraordinary design process that people have been able to develop 01:10:10.019 --> 01:10:13.949 spacesuits with articulating joints. 01:10:13.949 --> 01:10:19.570 I mean it is certainly not like walking around and doing things just with your body, but 01:10:19.570 --> 01:10:24.239 it is amazing how flexible spacesuits are. 01:10:24.239 --> 01:10:30.159 And it is a continual challenge to develop, particularly for the gloves. 01:10:30.159 --> 01:10:34.440 And, when we get back to the moon, to have legs that can actually walk in so that you 01:10:34.440 --> 01:10:36.179 don't have to hop around all the time. 01:10:36.179 --> 01:10:38.269 Although, there are times when that is good, too. 01:10:38.269 --> 01:10:45.269 But, in any case, the stiffness of the suit, because it turns out that most of the stiffness 01:10:47.139 --> 01:10:54.139 comes from compressing the gas, you want to try, first of all, to build articulated joints 01:10:54.309 --> 01:10:57.190 that don't change their volume. 01:10:57.190 --> 01:11:02.449 And, actually, people have designed metallic suits that look like Robby the Robot. 01:11:02.449 --> 01:11:07.010 So, they truly are zero delta volume suits. 01:11:07.010 --> 01:11:10.699 The problem is they are very heavy and there are other problems with metallic suits. 01:11:10.699 --> 01:11:15.760 And I don't have time to go into that. 01:11:15.760 --> 01:11:21.260 Given that you're going to have some volume change, the amount of work that you do is 01:11:21.260 --> 01:11:24.699 thermodynamically pressure times volume. 01:11:24.699 --> 01:11:27.309 You are going to have a delta V. 01:11:27.309 --> 01:11:29.389 You want to reduce the pressure. 01:11:29.389 --> 01:11:35.800 The lower your suit pressure, the easier it is to bend. 01:11:35.800 --> 01:11:42.679 Basically, you don't want to fill your suit with any gas that you don't really need. 01:11:42.679 --> 01:11:48.630 We certainly don't need nitrogen to stay alive, not on a short-term basis, so we fill the 01:11:48.630 --> 01:11:52.099 suit with oxygen. 01:11:52.099 --> 01:11:57.820 And we run it at about 4.3 psi for the Shuttle. 01:11:57.820 --> 01:12:04.820 This is just historically Mercury, Gemini and Apollo, the suit pressure was a little 01:12:05.699 --> 01:12:06.079 bit lower. 01:12:06.079 --> 01:12:13.079 Doctors felt, after doing calculations, what you're really interested in is the partial 01:12:14.469 --> 01:12:16.699 pressure of oxygen in your blood. 01:12:16.699 --> 01:12:19.329 And they wanted a little bit more margin. 01:12:19.329 --> 01:12:23.159 Since the Shuttle was supposed to be operational this and operational that, they wanted a little 01:12:23.159 --> 01:12:25.869 bit more margin. 01:12:25.869 --> 01:12:30.429 And so we bumped up the suit pressure a little bit. 01:12:30.429 --> 01:12:37.199 Mercury, Gemini and Apollo cabin was 100% oxygen at the same pressure so that you didn't 01:12:37.199 --> 01:12:40.340 have to worry about pre-breathing. 01:12:40.340 --> 01:12:46.329 In Skylab, it was not pure oxygen but it was a high enough oxygen that, again, they didn't 01:12:46.329 --> 01:12:47.599 have to worry about pre-breathe. 01:12:47.599 --> 01:12:54.599 It wasn't until we went to the Shuttle, which typically the Shuttle is at 14.7 or 100 kilopascals 01:12:58.869 --> 01:13:02.280 normal atmospheric pressure. 01:13:02.280 --> 01:13:07.840 If we know we are going to be doing a lot of EVAs, and I will talk about this later, 01:13:07.840 --> 01:13:13.849 what we do is we drop the overall cabin pressure, but we keep the partial pressure of oxygen 01:13:13.849 --> 01:13:18.699 the same so you end up bumping up the oxygen concentration. 01:13:18.699 --> 01:13:21.099 We don't do that with the ISS. 01:13:21.099 --> 01:13:28.099 The decision was made by the life scientists that since they wanted to study biology on 01:13:28.670 --> 01:13:35.639 the Space Station and all of our database is at one atmosphere, that if they took the 01:13:35.639 --> 01:13:42.479 Space Station down to 10.2 psi basically it would invalidate all of their life science 01:13:42.479 --> 01:13:44.369 research. 01:13:44.369 --> 01:13:47.559 So, the Station was only designed for one atmosphere. 01:13:47.559 --> 01:13:51.820 The operational people, when they started to talk about how much EVA was going to be 01:13:51.820 --> 01:13:58.300 involved in building and maintaining the Space Station, the astronauts said this is crazy. 01:13:58.300 --> 01:14:05.300 And you will see the impact of this later. 01:14:06.889 --> 01:14:08.699 This is just looking in the future. 01:14:08.699 --> 01:14:14.570 These are decisions that are going have to be made for future space systems, and they 01:14:14.570 --> 01:14:17.860 are looking at a lower working pressure. 01:14:17.860 --> 01:14:23.559 And you will see why as I go through this presentation. 01:14:23.559 --> 01:14:28.119 I think I'm not going to go through those charts. 01:14:28.119 --> 01:14:29.699 Again, this is a system. 01:14:29.699 --> 01:14:33.570 So, you are affecting a great many different things. 01:14:33.570 --> 01:14:37.659 Let's see. 01:14:37.659 --> 01:14:44.659 Which is the laser here? 01:14:44.769 --> 01:14:49.300 There we go. 01:14:49.300 --> 01:14:56.300 One of the interesting things here with EVA, just like in any ECLS system, is that the 01:14:57.539 --> 01:15:03.150 human body becomes one of your subsystems that you have to take care of. 01:15:03.150 --> 01:15:07.650 And, in many cases, we don't have a whole lot of design flexibility with our bodies 01:15:07.650 --> 01:15:11.229 because they come predesigned. 01:15:11.229 --> 01:15:15.079 So, we have to deal with that. 01:15:15.079 --> 01:15:22.079 We have all of the physiology, the bends. 01:15:22.639 --> 01:15:22.889 Materials. I talked about flammability in a pure oxygen environment. 01:15:25.820 --> 01:15:32.820 I talked about the constraints of microgravity and partial gravity physiology studies in 01:15:33.170 --> 01:15:33.829 the ISS. 01:15:33.829 --> 01:15:40.829 Of course, NASA has decided that we don't need to do that anymore. 01:15:41.190 --> 01:15:44.440 And, I guess, our international partners are still going to want to do this. 01:15:44.440 --> 01:15:47.449 In any case, the Station is designed. 01:15:47.449 --> 01:15:53.809 The cooling we talked about, I think, in the ECLA section lecture, the fact that if you 01:15:53.809 --> 01:15:58.340 drop your cabin pressure now you've got to pump more air for all the air cooled things. 01:15:58.340 --> 01:16:05.340 And if you really want a design for a variable cabin pressure then that flows over into the 01:16:07.959 --> 01:16:14.959 cooling requirements, more water cooling, different fan requirements and so on. 01:16:15.849 --> 01:16:17.079 And it goes on. 01:16:17.079 --> 01:16:24.079 If you are going to do multiple EVAs, what you're really interested in, when you're looking 01:16:26.840 --> 01:16:33.300 at efficiency, is what we call EVA Work Efficiency Index. 01:16:33.300 --> 01:16:40.300 It is the total amount of time involved in preparing for and carrying out an EVA, the 01:16:40.380 --> 01:16:43.979 ratio of that to the actual useful working time you get outside. 01:16:43.979 --> 01:16:49.619 And the more time you have to spend breathing pure oxygen to denitrogenate your blood, that 01:16:49.619 --> 01:16:52.619 is taking away from your overall work efficiency. 01:16:52.619 --> 01:16:58.159 When we do tests on the ground and we start out at normal sea level pressure and we want 01:16:58.159 --> 01:17:05.159 to go down to 4.3 psi pure oxygen, we actually have to do a four hour nitrogen purge. 01:17:09.199 --> 01:17:14.760 We have to just sit in the suit or stand in the suit for four hours, this is in the EVA 01:17:14.760 --> 01:17:18.409 test chambers, before we actually can go down to pressure. 01:17:18.409 --> 01:17:22.749 If you want to get an eight hour work day of EVA, that is just unacceptable. 01:17:22.749 --> 01:17:28.110 And that is why they made the decision to lower the Shuttle's cabin pressure. 01:17:28.110 --> 01:17:30.679 Then you only have to do about a 40 minute EVA. 01:17:30.679 --> 01:17:36.459 And I have some of the specific numbers on that later. 01:17:36.459 --> 01:17:41.289 As I say, just the review here is that we do have this capability on the Shuttle. 01:17:41.289 --> 01:17:44.949 We don't have it on the Station. 01:17:44.949 --> 01:17:49.219 They have figured out a few ways to make the denitrogenation process a little bit more 01:17:49.219 --> 01:17:54.880 efficient on the Station, but it is still a big overhead hit. 01:17:54.880 --> 01:18:01.840 And we are very concerned for the future because EVA is not just an afterthought when you're 01:18:01.840 --> 01:18:04.380 going to be exploring on the Moon or Mars. 01:18:04.380 --> 01:18:07.829 You are going there basically to do EVA. 01:18:07.829 --> 01:18:10.690 Otherwise, why bother? 01:18:10.690 --> 01:18:13.209 We have got to deal with this. 01:18:13.209 --> 01:18:18.699 Here is the basic physiology that we are dealing with. 01:18:18.699 --> 01:18:25.699 Oxygen percentage on the abscissa, total pressure on the ordinate and all different units. 01:18:26.479 --> 01:18:33.479 Millimeters of mercury, psi, and I think now people use kilopascals, which I don't really 01:18:34.639 --> 01:18:35.329 relate to. 01:18:35.329 --> 01:18:39.820 But I know about 100 kilopascals is about one atmosphere, so luckily that makes it easy. 01:18:39.820 --> 01:18:46.820 Normally, we are at one atmosphere 20% or 21% oxygen, we are up here, and this is the 01:18:49.829 --> 01:18:53.940 normal sea level equivalent. 01:18:53.940 --> 01:19:00.940 You start dropping the pressure and you have to increase the percentage of oxygen. 01:19:02.010 --> 01:19:09.010 There is a maximum level of breathing oxygen at pressure oxygen toxicity because oxygen 01:19:11.760 --> 01:19:16.320 is almost totally absorbed through your alveoli. 01:19:16.320 --> 01:19:23.320 And normally our alveoli stay inflated because we have 80% nitrogen which is only very reluctantly 01:19:24.550 --> 01:19:25.070 absorbed. 01:19:25.070 --> 01:19:28.969 I mean it does get through, that is how it gets into our blood and so on, but it is a 01:19:28.969 --> 01:19:30.409 much slower transport. 01:19:30.409 --> 01:19:31.909 But oxygen gets right through. 01:19:31.909 --> 01:19:38.909 And if you breathe pure oxygen for a long time you can really hurt your lungs and it 01:19:40.959 --> 01:19:44.010 can be lethal at a certain point. 01:19:44.010 --> 01:19:49.119 We actually don't have any good physiological data. 01:19:49.119 --> 01:19:51.789 I was down in Houston last week at a big EVA conference. 01:19:51.789 --> 01:19:53.760 That is why we didn't have class on Tuesday. 01:19:53.760 --> 01:20:00.719 They were talking about what about long-term planetary EVAs, even at 4 psi pure oxygen, 01:20:00.719 --> 01:20:03.329 is that going to be harmful to health? 01:20:03.329 --> 01:20:04.079 We honestly don't know. 01:20:04.079 --> 01:20:10.219 I mean that is an active area which needs research. 01:20:10.219 --> 01:20:15.689 On the other side, of course you get into hypoxia which you have all heard of. 01:20:15.689 --> 01:20:19.579 You get it when you go up on Mount Everest and so on. 01:20:19.579 --> 01:20:26.579 So, you've got a boundary that you have to work in. 01:20:27.159 --> 01:20:31.939 Now, this is sort of where things have fallen. 01:20:31.939 --> 01:20:34.939 The blue line is the hypoxic boundary. 01:20:34.939 --> 01:20:39.659 The green line is normal oxygen. 01:20:39.659 --> 01:20:45.820 When we were using pure oxygen spacecraft environments, we were well above that. 01:20:45.820 --> 01:20:48.090 You would like to stay as close as possible. 01:20:48.090 --> 01:20:55.090 With Shuttle EVA, we moved a little bit closer to hypoxic, but we're still in a physiologically 01:20:55.300 --> 01:21:02.300 perfectly reasonable environment. 01:21:02.639 --> 01:21:04.889 Decompression sickness, just a quick review. 01:21:04.889 --> 01:21:06.030 Any scuba divers here? 01:21:06.030 --> 01:21:09.489 You are all familiar with this. 01:21:09.489 --> 01:21:16.489 There are various levels of decompression sickness anywhere from just a mild tingling 01:21:17.139 --> 01:21:24.139 of the skin to joint pain to phase three DCS where you get central nervous system impairment 01:21:25.489 --> 01:21:32.489 which can actually cause death, so you don't want to mess around with it. 01:21:36.380 --> 01:21:39.059 People refer to this famous R value. 01:21:39.059 --> 01:21:40.590 You run into this all the time. 01:21:40.590 --> 01:21:47.249 What you are really interested in is what is the ratio between the actual partial pressure 01:21:47.249 --> 01:21:52.900 of nitrogen in your blood compared to your suit pressure? 01:21:52.900 --> 01:21:57.090 And this over here shows this R value. 01:21:57.090 --> 01:22:03.550 If you are down at one the nitrogen isn't going to bubble out at all so you have no 01:22:03.550 --> 01:22:05.709 incidence of bends. 01:22:05.709 --> 01:22:12.579 VGE, venous gas emboli. 01:22:12.579 --> 01:22:19.579 And then, as the R value increases, the dotted line gas emboli, that just means you have 01:22:20.110 --> 01:22:20.909 bubbles forming. 01:22:20.909 --> 01:22:26.099 DCS means actual symptoms of bends. 01:22:26.099 --> 01:22:30.300 And then grade three DCS which is very serious indeed. 01:22:30.300 --> 01:22:37.300 The way they make these measurements, they have these large physiological studies where 01:22:37.389 --> 01:22:42.329 they actually get people to volunteer to go through these pumped down protocols. 01:22:42.329 --> 01:22:48.659 And then they actually put sensitive microphones and ultrasound things that can actually hear 01:22:48.659 --> 01:22:51.249 the bubbles as they move around your veins. 01:22:51.249 --> 01:22:56.070 I have never been able to figure out why anybody would volunteer for these experiments. 01:22:56.070 --> 01:22:59.739 I take my hat off to them. 01:22:59.739 --> 01:23:06.300 Because the only way you build up this data is that some people actually do get the bends 01:23:06.300 --> 01:23:07.170 from these experiments. 01:23:07.170 --> 01:23:12.849 And, of course, they have hyperbaric chambers which, as soon as there are any symptoms, 01:23:12.849 --> 01:23:17.079 they put them right into the chamber and pump them to pressure and it goes away. 01:23:17.079 --> 01:23:20.439 And I don't think that they have lost any volunteers. 01:23:20.439 --> 01:23:26.400 Like I say, that is not something I am going to volunteer for. 01:23:26.400 --> 01:23:31.360 Other factors, this is something that becomes important. 01:23:31.360 --> 01:23:36.630 It turns out that the amount of time you spend at reduced pressure is important. 01:23:36.630 --> 01:23:37.860 Also exercise. 01:23:37.860 --> 01:23:42.739 It turns out that the more you exercise, maybe it makes sense, you're moving your joints 01:23:42.739 --> 01:23:45.469 around, but the bubbles come out. 01:23:45.469 --> 01:23:48.579 Actually, what they have started to do on the Space Station, since we cannot go to a 01:23:48.579 --> 01:23:55.579 reduced cabin, that while they are breathing oxygen for the first hour or so they do very 01:23:55.590 --> 01:24:01.849 exhaustive exercise, both upper and lower body on an exercise bike with arm exercise 01:24:01.849 --> 01:24:02.280 as well. 01:24:02.280 --> 01:24:09.280 To try to drive away as much of the oxygen early on in the decompression preparation 01:24:10.570 --> 01:24:11.429 as you can. 01:24:11.429 --> 01:24:14.219 OK. 01:24:14.219 --> 01:24:16.900 Where does that put us? 01:24:16.900 --> 01:24:22.079 As I said, the more nitrogen you have in your blood to start out with, the longer a pre-breathe 01:24:22.079 --> 01:24:28.829 you are going to have to do before you can go out. 01:24:28.829 --> 01:24:32.949 These are the normoxic and hypoxic lines, which I showed you before. 01:24:32.949 --> 01:24:39.139 And then these are the contours of the amount of time you have to pre-breathe. 01:24:39.139 --> 01:24:46.139 Remember, I told you if you are at one atmosphere, 20% oxygen, your pre-breathe time is 240 minutes, 01:24:48.139 --> 01:24:49.409 four hours. 01:24:49.409 --> 01:24:53.499 This is to get yourself down to an R value of 1.65. 01:24:53.499 --> 01:25:00.499 This is not 100% safe because, remember, at 1.65, there still is a 25% incidence of DCS. 01:25:08.650 --> 01:25:15.650 Now, the interesting thing, these are the statistics that come from the laboratory trials, 01:25:15.840 --> 01:25:21.760 we have never had a reported case of bends during EVAs. 01:25:21.760 --> 01:25:25.949 And people are not quite sure why. 01:25:25.949 --> 01:25:30.820 Some people suspect that maybe even if an astronaut is getting joint pain they are not 01:25:30.820 --> 01:25:37.539 going to report it because maybe that would prevent you from doing another EVA. 01:25:37.539 --> 01:25:42.769 I mean there are enough other pains that you undergo in just using a spacesuit that maybe 01:25:42.769 --> 01:25:44.170 you don't even notice it. 01:25:44.170 --> 01:25:48.579 You feel a problem in your joints or your fingers and you say oh, damn, my gloves don't 01:25:48.579 --> 01:25:53.789 fit right or something like that. 01:25:53.789 --> 01:25:55.550 I have another slide mentioning this later. 01:25:55.550 --> 01:26:02.550 There is some suspicion that weightlessness may have an impact, which means that the bends 01:26:04.179 --> 01:26:10.999 susceptibility on the Moon or on Mars may actually be greater than it is in weightlessness. 01:26:10.999 --> 01:26:15.579 We just don't know. 01:26:15.579 --> 01:26:18.860 Here is where we have gotten to on the Shuttle EVA. 01:26:18.860 --> 01:26:25.389 Again, this is no pre-breathe, this is one hour pre-breathe, so we are at about 40 minutes 01:26:25.389 --> 01:26:26.329 on the Shuttle. 01:26:26.329 --> 01:26:30.189 That is where we are. 01:26:30.189 --> 01:26:33.630 Now, this is a design problem. 01:26:33.630 --> 01:26:35.260 How are we going to design the CEV? 01:26:35.260 --> 01:26:40.039 How are we going to design the equipment, the habitats that we are going to use on the 01:26:40.039 --> 01:26:43.519 Moon and Mars? 01:26:43.519 --> 01:26:45.539 Now we're talking about surface exploration. 01:26:45.539 --> 01:26:52.539 And, as I said, there is a lot of uncertainty about the affect of gravity. 01:26:52.780 --> 01:26:58.670 But we suspect that it may be more bends inducing than weightlessness. 01:26:58.670 --> 01:27:05.670 And so what they are doing for safety and conservatism is instead of using the R value 01:27:07.019 --> 01:27:14.019 of 1.65, which we use on the Shuttle, they are taking it down to about 1.3, 1.4. 01:27:18.239 --> 01:27:19.499 Now, what does that do? 01:27:19.499 --> 01:27:22.349 Here is 1.4, 1.3. 01:27:22.349 --> 01:27:27.249 Where does that put the Shuttle EVA we now would have to get down to that R value? 01:27:27.249 --> 01:27:31.530 We have got a two hour pre-breathe. 01:27:31.530 --> 01:27:37.769 To get down to 1.3, we have got a 2.5 hour pre-breathe. 01:27:37.769 --> 01:27:42.499 And this is with the normal spacesuit at 4.3 psi. 01:27:42.499 --> 01:27:46.369 We are heading an operational problem. 01:27:46.369 --> 01:27:51.949 If you want to go out on your geology traverse on the Moon, you have got to depressurize, 01:27:51.949 --> 01:27:53.539 denitrogenate for 2, 2.5 hours. 01:27:53.539 --> 01:27:55.110 I don't think so. 01:27:55.110 --> 01:27:56.959 But what are we going to do? 01:27:56.959 --> 01:28:03.959 Well, if you increase the suit pressure now the R value, at a given level of nitrogen, 01:28:06.510 --> 01:28:07.739 goes down. 01:28:07.739 --> 01:28:14.739 And so at 6 psi, even for an R of 1.3, you are in the zero pre-breathe range, which would 01:28:17.610 --> 01:28:19.269 be great. 01:28:19.269 --> 01:28:24.599 People have suggested, well, maybe we should build a variable pressure suit so that you 01:28:24.599 --> 01:28:29.360 could go out at 6 psi, sort of get things set up. 01:28:29.360 --> 01:28:35.360 And then all that time counts towards your denitrogenation so maybe then after two hours 01:28:35.360 --> 01:28:37.360 into your EVA now you can drop your pressure. 01:28:37.360 --> 01:28:41.809 And now, if you have any things where you need more dexterity, you will be OK. 01:28:41.809 --> 01:28:48.809 But the pressure control system in a spacesuit is a very complex undertaking. 01:28:49.959 --> 01:28:52.769 The Russians do have a dual pressure suit. 01:28:52.769 --> 01:28:57.380 They never used the lower pressure, to my knowledge. 01:28:57.380 --> 01:29:00.789 And it is a big hit to try to design this into the suit. 01:29:00.789 --> 01:29:03.959 And, of course, to design a suit to operate at a higher pressure. 01:29:03.959 --> 01:29:10.289 The Russians work at about 5 psi, but it means your suit is less flexible, heavier and is 01:29:10.289 --> 01:29:16.209 just going the opposite direction from the desire to accomplish useful work, which is 01:29:16.209 --> 01:29:19.439 why you are putting on the spacesuit in the first place. 01:29:19.439 --> 01:29:23.689 This is what we are working against. 01:29:23.689 --> 01:29:25.030 Again, we have got a systems problem. 01:29:25.030 --> 01:29:26.800 It is not just the pressure. 01:29:26.800 --> 01:29:30.999 It is the oxygen. 01:29:30.999 --> 01:29:37.999 In Skylab, in Apollo, because you were working in a pure oxygen environment, now, of course, 01:29:39.229 --> 01:29:42.780 we're talking about what is the pressure going to be in the cabin. 01:29:42.780 --> 01:29:48.119 You want to keep the cabin at a higher oxygen environment. 01:29:48.119 --> 01:29:50.889 Your material selection is highly limited. 01:29:50.889 --> 01:29:54.510 As it says, they tended to use a lot of metallic materials. 01:29:54.510 --> 01:29:56.599 Well, what do we know about metals? 01:29:56.599 --> 01:29:58.729 Particularly aluminum. 01:29:58.729 --> 01:30:03.229 First of all, aluminum will burn at 100% oxygen. 01:30:03.229 --> 01:30:08.749 But your cabin, even if it is not 100% oxygen, you are going to have a lot of metallic material. 01:30:08.749 --> 01:30:15.749 Well, metal, when you're dealing with radiation, you hit metal, aluminum or even higher atomic 01:30:19.420 --> 01:30:24.039 number metals with primary cosmic rays and you get spallation. 01:30:24.039 --> 01:30:26.409 You produce a lot of secondary particles. 01:30:26.409 --> 01:30:30.639 And you end up with actually more radiation than you would have gotten if you had just 01:30:30.639 --> 01:30:32.869 gotten hit by the incident cosmic ray. 01:30:32.869 --> 01:30:37.699 What you really prefer is to have low atomic number. 01:30:37.699 --> 01:30:39.579 Hydrogen is best. 01:30:39.579 --> 01:30:42.400 Water, hydrogen, oxygen and so forth. 01:30:42.400 --> 01:30:48.999 If you are forced to increase the metallic content of your spacecraft because of the 01:30:48.999 --> 01:30:55.999 oxygen flammability problems now you are going in the wrong direction for radiation protection 01:30:58.429 --> 01:31:04.309 which becomes an issue when you're dealing with long duration stays on the Moon, interplanetary 01:31:04.309 --> 01:31:06.380 transport and so on. 01:31:06.380 --> 01:31:08.139 So, it is all interrelated. 01:31:08.139 --> 01:31:13.769 You cannot change one thing without changing the other. 01:31:13.769 --> 01:31:14.030 Flammability. 01:31:14.030 --> 01:31:15.300 Well, we have been talking about that. 01:31:15.300 --> 01:31:18.079 I won't stay on that. 01:31:18.079 --> 01:31:24.249 But, again, it is very dependent on oxygen. 01:31:24.249 --> 01:31:27.010 Oxygen restricts the use of non-metallic materials. 01:31:27.010 --> 01:31:32.170 But nonmetallic materials are what we would like to use from a radiation point of view. 01:31:32.170 --> 01:31:38.189 You would like to have a lot of hydrocarbons, you know, polyethylene plastic in your spacecraft 01:31:38.189 --> 01:31:43.070 because they absorb cosmic rays. 01:31:43.070 --> 01:31:49.820 But, in any case, it is pretty well agreed that we never want to go above 30% oxygen. 01:31:49.820 --> 01:31:55.189 It just becomes too restrictive on the types of materials we can use. 01:31:55.189 --> 01:31:56.840 That is going to be a design constraint. 01:31:56.840 --> 01:32:03.840 And, remember, we are aiming towards a systems level design of our long duration space habitats 01:32:05.590 --> 01:32:07.039 which are EVA compatible. 01:32:07.039 --> 01:32:09.539 30% oxygen. 01:32:09.539 --> 01:32:11.260 Now we are back to this. 01:32:11.260 --> 01:32:13.170 Now we can draw a red line. 01:32:13.170 --> 01:32:15.599 And we have got to stay on the left of that line. 01:32:15.599 --> 01:32:19.949 We have got to stay above the blue hypoxic line. 01:32:19.949 --> 01:32:26.949 Now, also remember that we have got these pre-breathe lines. 01:32:27.429 --> 01:32:31.849 Let's say we are going to limit pre-breathe to no more than one hour. 01:32:31.849 --> 01:32:35.869 Well, we are cutting down on our design space here. 01:32:35.869 --> 01:32:40.110 We have got the oxygen flammability which is cutting off to the right. 01:32:40.110 --> 01:32:44.239 We have got the hypoxic limit which is cutting off in this direction. 01:32:44.239 --> 01:32:47.869 And we have got the pre-breathe limit which is cutting off there. 01:32:47.869 --> 01:32:54.869 We are kind of in a, I won't call it a box, a rather small triangle. 01:32:57.349 --> 01:33:03.869 Now, if we go to a 6 psi spacesuit, as I said, we open up the design space a lot. 01:33:03.869 --> 01:33:10.019 But at a price of flexibility, maneuverability and the ability to do the things that we want 01:33:10.019 --> 01:33:14.530 to do in the first place. 01:33:14.530 --> 01:33:16.699 Where are we going to go with this? 01:33:16.699 --> 01:33:19.340 As I say, it is an active area of research. 01:33:19.340 --> 01:33:26.340 I cannot tell you what the answer is going to be but it looks like they are going to 01:33:30.719 --> 01:33:37.719 probably be going for 8 to 9 psi with an oxygen concentration approaching 30%. 01:33:39.249 --> 01:33:44.689 And that the CEV, from what I have been told, is most likely going to be designed with a 01:33:44.689 --> 01:33:48.939 variable pressure capability because it also has to be able to dock with the Space Station 01:33:48.939 --> 01:33:51.309 which means it has to be able to take one atmosphere. 01:33:51.309 --> 01:33:58.309 And also, because the CEV by itself is not going to have an airlock, if you would have 01:33:58.369 --> 01:34:03.689 to do an emergency EVA out of the CEV, for whatever reason, you are going to have to 01:34:03.689 --> 01:34:10.689 depressurize like we did back in the Gemini days, or Apollo. 01:34:10.820 --> 01:34:17.449 And, of course, that is going to affect the design of all the other systems on the CEV 01:34:17.449 --> 01:34:24.449 because they will have to be able to operate from a vacuum all the way up to one atmosphere. 01:34:28.420 --> 01:34:34.010 Just in the end, I hope what you have gotten out of this is, again, we are trying to look 01:34:34.010 --> 01:34:37.039 at things from a systems engineering point of view. 01:34:37.039 --> 01:34:43.619 And this is one big system where EVA cannot be considered just on its own. 01:34:43.619 --> 01:34:50.400 I gave an example of how it affects the RCS system with Hubble. 01:34:50.400 --> 01:34:54.409 Here it affects the environmental control life support. 01:34:54.409 --> 01:35:01.409 Flammability, radiation protection, it is all linked together. 01:35:02.639 --> 01:35:09.639 This was the recommendation that we came out with, slightly below 9 psi pushing 30%. 01:35:10.409 --> 01:35:17.409 But, as I said, there is a lot of research that has to be done to understand the way 01:35:17.610 --> 01:35:22.478 bends behave at partial gravity. 01:35:22.478 --> 01:35:23.419 How we are going to do that? 01:35:23.419 --> 01:35:30.070 I have no idea. 01:35:30.070 --> 01:35:37.070 As I said, for the International Space Station, we have to be able to go up to regular atmosphere. 01:35:43.439 --> 01:35:48.429 We were making this presentation as part of the study we were doing last year on CEV, 01:35:48.429 --> 01:35:53.769 but it was so relevant to what we did here that I didn't see any point in modifying it 01:35:53.769 --> 01:35:54.419 for this class. 01:35:54.419 --> 01:36:01.419 But we had to make these decisions on the Shuttle based on similar calculations looking 01:36:02.709 --> 01:36:03.959 at the design space. 01:36:03.959 --> 01:36:10.079 The difference was with the Shuttle we were using an R value of 1.6, 1.7. 01:36:10.079 --> 01:36:14.860 And so we were able to get down to a 40 minute pre-breathe. 01:36:14.860 --> 01:36:21.189 What we do with the Shuttle is about the day before you are going to do your first EVA 01:36:21.189 --> 01:36:25.739 you actually drop the cabin pressure. 01:36:25.739 --> 01:36:31.380 And when we had the lecture on environmental control, remember there is a cabin pressure 01:36:31.380 --> 01:36:35.309 controller at 14.7 and a pressure controller at 8 psi. 01:36:35.309 --> 01:36:41.519 But when they designed the Shuttle, nobody was thinking about EVA or about this pre-breathe 01:36:41.519 --> 01:36:41.800 time. 01:36:41.800 --> 01:36:45.019 And so, there is no 10.2 controller. 01:36:45.019 --> 01:36:46.459 We have to do that manually. 01:36:46.459 --> 01:36:51.099 You drop it and then you add a little bit of nitrogen or a little bit of oxygen, depending 01:36:51.099 --> 01:36:54.669 on what the instrumentation tells you you need. 01:36:54.669 --> 01:37:01.559 And then there is a periodic maintenance which you have to perform in order to keep the proper 01:37:01.559 --> 01:37:07.320 gas concentrations. 01:37:07.320 --> 01:37:11.209 And then we leave it down there for the duration of all the EVAs. 01:37:11.209 --> 01:37:18.209 And then, when the last EVA is finished, then you turn the 14.7 controller back on. 01:37:18.219 --> 01:37:25.219 Now, of course, since you have the proper oxygen partial pressure, most of the gas that 01:37:27.699 --> 01:37:29.949 comes into the cabin is nitrogen. 01:37:29.949 --> 01:37:34.820 And, actually, I think we may have mentioned this before, it comes in the bathroom. 01:37:34.820 --> 01:37:41.820 And so, for the time when you are re-pressurizing the cabin, the bathroom is off limits. 01:37:44.349 --> 01:37:46.030 And I think that is basically it. 01:37:46.030 --> 01:37:51.320 The timing has been pretty good. 01:37:51.320 --> 01:37:51.929 Questions? 01:37:51.929 --> 01:37:52.369 Comments? 01:37:52.369 --> 01:37:53.249 Yeah. 01:37:53.249 --> 01:38:00.249 Is anybody looking at using a fully one atmospheric spacesuit? 01:38:06.019 --> 01:38:09.159 Actually, it turns out there is a principle called holdings principle. 01:38:09.159 --> 01:38:16.159 Let me get this up because I have some pictures of what we were doing. 01:38:32.610 --> 01:38:38.419 If you change by less than a factor of two you don't get the bends. 01:38:38.419 --> 01:38:40.939 This is an empirical finding. 01:38:40.939 --> 01:38:47.939 And so, the idea was if you could have a suit that worked at about 8 psi you would have 01:38:48.010 --> 01:38:49.820 a zero pre-breathe suit. 01:38:49.820 --> 01:38:52.079 And I participated in a bunch of tests. 01:38:52.079 --> 01:38:59.079 These are some other robotic things. 01:39:00.929 --> 01:39:06.439 This was the hard suit designed by Ames. 01:39:06.439 --> 01:39:12.539 Because it is a constant volume suit it is not sensitive to the pressure the way that 01:39:12.539 --> 01:39:16.269 a soft suit is. 01:39:16.269 --> 01:39:19.739 And we did a lot of tests, actually. 01:39:19.739 --> 01:39:23.550 We always came unstuck on the gloves. 01:39:23.550 --> 01:39:30.550 Nobody has been able to design an 8 psi glove that really gives you sufficient mobility. 01:39:31.869 --> 01:39:32.939 I mean it is a dream. 01:39:32.939 --> 01:39:34.280 People would love to be able to do it. 01:39:34.280 --> 01:39:36.909 If we could figure it out that would solve all these problems. 01:39:36.909 --> 01:39:43.909 Although, if you are going to Mars maybe you don't want full pressure because if you have 01:39:47.159 --> 01:39:54.159 one atmosphere compared to 8 or 9 psi your structure has to be that much thicker and 01:39:55.469 --> 01:39:55.919 heavier. 01:39:55.919 --> 01:39:58.999 They went through some of those calculations. 01:39:58.999 --> 01:40:01.409 This is now on the hand with the Space Station. 01:40:01.409 --> 01:40:05.789 And they figured that for all the meteorite shielding and everything they had to put on 01:40:05.789 --> 01:40:11.400 the outside of the Space Station that actually the change in thickness that would be involved 01:40:11.400 --> 01:40:16.978 in changing the pressure from one atmosphere to another really wouldn't make that much 01:40:16.978 --> 01:40:18.889 of a difference. 01:40:18.889 --> 01:40:22.789 All of these things, again, they are interrelated. 01:40:22.789 --> 01:40:24.749 But it is a good point. 01:40:24.749 --> 01:40:30.209 That is why I showed those designs for 6 psi because people are still thinking suppose 01:40:30.209 --> 01:40:33.780 we could design a spacesuit to work at a higher pressure. 01:40:33.780 --> 01:40:40.780 But right now we don't know how to do that. 01:40:43.019 --> 01:40:45.679 I hope everybody has a very happy Thanksgiving. 01:40:45.679 --> 01:40:48.719 We will see you a week from today. 01:40:48.719 --> 01:40:55.719 And if there are any questions, again, about either your oral presentations or the written 01:40:57.510 --> 01:41:01.329 presentations, I will be here today. 01:41:01.329 --> 01:41:06.070 And then I am gone for the rest of the week, but I will be looking at emails so you can 01:41:06.070 --> 01:41:08.599 send me emails and we can discuss things. 01:41:08.599 --> 01:41:08.909 OK.