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3. Two, one, and we have lift off.
4. Well, we've looked at how rockets can take people
5. into space.
6. What about the basic idea of how do we stay alive in space
7. and healthy so we can carry out useful work?
8. And that's where we get into the concept
9. of environmental control and life support.
10. And we call this ECLSS-- E-C-L-S-S.
11. Environmental Control and Life Support Systems--
12. one of many NASA acronyms that we'll have to get used to.
13. Now, normally, we're talking about human space flight,
14. but satellites also have certain environmental requirements.
15. One of the things that we've seen,
16. particularly in recent times, is an enormous variation
17. in the scale.
18. We have very large telecommunication satellites,
19. the tracking and data relay satellite,
20. which you can see being deployed from the Shuttle
21. and fully deployed at geostationary orbit.
22. Then, of course, the International Space Station,
23. which is a huge spacecraft.
24. And yet, we're also able to make tiny little cube
25. sats with only 10 centimeters in any dimension.
26. So there's a huge scale which we have for spacecraft,
27. and we can miniaturize a lot of spacecraft functions,
28. including thermal control and communications and the like.
29. When we're dealing with people, however, we
30. do have some variability.
31. Here's the crew of SDS 109-- the Shuttle crew
32. which went up to do the final servicing mission on the Hubble
33. Space Telescope in the spring of 2009.
34. And we have the commander, you can see,
35. in the center, Scott Altman, next to mission specialist,
36. Nancy Currie.
37. And there's a big height differential,
38. but nothing like the huge scale that we
39. have between a big telecommunications
40. satellite at geostationary orbit and a tiny little cube sat.
41. So we can't miniaturize human beings.
42. That's the basic factor that we have to work with.
43. And so we have some basic life support requirements
44. which we're going to have to deal with.
45. And let's consider, now, what a human needs
46. to stay alive and healthy.
47. And of course, here on Earth, the Earth-- planet Earth--
48. provides us with the environment which
49. keeps us alive and healthy and allows us to do useful work.
50. Of course, we have to take care of the planet in return.
51. But we don't have that environment
52. when we go into space.
53. We have to take our environment with us.
54. And so what are the characteristics
55. of that environment which we need to stay alive and healthy.
56. We certainly need oxygen-- not just the oxygen to breathe,
57. but we need pressure over our entire bodies
58. so that our bodily fluids don't boil off.
59. And the atmosphere that we're breathing also
60. has to be cleaned.
61. We'll have to remove dust and other particles from it.
62. We have to be at the right temperature,
63. the right humidity.
64. We have to have water to drink, food
65. to eat, waste disposal facilities.
66. And if we want to stay healthy, we have to control microbes.
67. So that's quite a lot of requirements,
68. and again, here on Earth, often we
69. don't think about it because Earth supplies
70. as with most of the aspects of the environment
71. we need to stay alive and healthy.
72. In space, we have to bring it all with us.
73. So we have to create this environment.
75. In addition, since we are on a space mission,
76. our environmental control and life
77. support system better be reliable.
78. On the Space Station, we do have parts of the system which
79. break from time to time.
80. You better be able to maintain the system.
81. If something breaks, you either want
82. to be able to replace it or fix it.
83. And that's what gives you sustainability.
84. And of course, the more spare parts
85. you need, the more often you have to fix it,
86. that's going to cost money.
87. And of course, like anything in space flight,
88. we're concerned with mass because we have to launch off
89. the surface of the Earth.
90. Power is always constrained.
91. We have limited volume.
92. And if the crew has to spend a lot of time taking care
93. of the system just to maintain it,
94. then that's going to take away from other useful work
95. that they want to do.
96. So there's a lot of requirements that we
97. put on our environmental control and life support system.
98. And of course, depending on what your mission is,
99. you're going to have different solutions for your ECLSS
100. requirements, depending on how many crew you have,
101. how big is your spacecraft, and, probably
102. most important of all, how long are you going to be up there
103. in space.
104. In the Mercury Mission, we had missions of just a few days
105. with one single person.
106. And we basically took with us whatever we needed.
107. We carried water.
108. We carried oxygen.
109. Waste disposal was fairly primitive at the time.
110. Contrast that with The International Space Station,
111. and here we see not only the permanent crew of six,
112. but there's a visiting crew that came up either on a Shuttle
113. or nowadays they come up on the Soyuz missions.
114. But we've had as many as a dozen people
115. at a time in the International Space Station.
116. And the people who are there for a long duration
117. stay up for six months at a time.
118. So being able to recycle and reuse
119. your environmental components like oxygen and water
120. becomes much more important on the Space Station
121. than it was on short duration flights.
122. So the basic philosophy which we follow with ECLSS systems is we
123. have certain human needs-- the body has
124. to consume certain materials like oxygen, water, food--
125. and we turn that into waste.
126. So we breathe oxygen in and we breathe out
127. carbon dioxide, which we're going
128. to have to do something with.
129. We eat food and we have solid waste, which
130. we're going to take care of.
131. We drink water and we produce urine and sweat
132. and, again, we're going to have to deal with all of that.
133. When we're dealing with environmental control and life
134. support systems, there are two fundamental aspects
135. of the systems that we have to deal with.
136. And that is, what is the basic operational mode?
137. And we talk about open loop ECLSS and closed loop ECLSS.
138. Open loop, we saw pictures of the Mercury,
139. and this is basically a system whereby
140. we bring all the resources that we want with us from the Earth.
141. All the water we're going to drink,
142. all the oxygen we're going to breathe, and so on.
143. And we don't try to recycle it because the mission is
144. short enough that we can afford to bring it all with us.
145. But if we're going to stay up for a reasonable amount
146. of time, we want to start closing the various loops
147. in water and oxygen so that we can actually reuse
148. some of our waste products.
149. And that way, we don't have to launch as much
150. from the Earth, that tremendously reduces
151. the cost of the space mission.
152. And of course, we have different systems-- water, air,
153. and so on.
154. And some of the systems are partially open or partially
155. closed, and you can have some systems which are closed
156. and other systems which are open.
157. It all depends on the nature of the mission.
158. And these are all design decisions
159. which engineers have to make when
160. they're designing a spacecraft.
161. A way of looking at open and closed loop
162. systems and their advantages and disadvantages.
163. First of all, the graph here.
164. Open loop, the mass requirements depend essentially-- almost
165. linearly-- with the duration of the mission.
166. In other words, if you were going
167. to stay up for a very short time, you need very little.
168. And then as the mission length increases, you need more.
169. So if you're going to stay up for twice as long
170. and you're not recycling your water, your oxygen,
171. you're going to need twice as much water or oxygen.
172. For a closed loop system where you recycle,
173. there is a certain initial mass you have to start with
174. and you have to launch all of your recycling equipment.
175. And we'll see later on what some of that equipment looks like.
176. But since you're recycling, the amount
177. that you have to resupply doesn't increase nearly
178. as rapidly, and so you can see the slope is much less.
179. And there is for all of these systems
180. a certain crossover point at which
181. it becomes advantageous from the mass point of view
182. to have a closed loop system rather than an open loop
183. system.
184. And remember that this crossover point may not
185. be the same for all the different parts of the ECLSS--
186. the water crossover point may be at a different mission
187. duration, for instance, than the oxygen recycling system.
188. Examples.
189. One of the things that we have to do
190. is remove carbon dioxide from the atmosphere
191. after we breathe it out.
192. We have a chemical called lithium hydroxide-- LiOH--
193. which actually combines with carbon dioxide
194. and removes it from the air.
195. But it can only do it once, and you can't recycle it.
196. It's a simple system.
197. We use it for launch and reentry vehicles.
198. Older space suits used lithium hydroxide.
199. The Shuttle used it.
200. But up on the Space Station where crews spend a lot longer,
201. we want reusable scrubbers so that we
202. don't just use the lithium hydroxide once
203. and throw it away.
204. So we have various types of reusable scrubbers,
205. which we'll talk about later.
206. And if you want to get even deeper into the recycling,
207. you'd actually like to recover some of the oxygen from the CO2
208. rather than just throw all the CO2 away.
209. So there's different levels of closing
210. the loop with CO2 scrubbing.
211. Water, if you have a short mission,
212. just take all the water you need to drink
213. and don't recycle it at all.
214. In the early space stations, in the initial configuration
215. of the International Space Station,
216. we actually reused some of the water
217. that we got from cabin humidity.
218. That's what comes out in your perspiration and your breath.
219. That's called so-called gray water.
220. Nowadays, we're actually recycling
221. the urine that's collected in the International Space
222. Station.
223. So the level of recycling has increased,
224. and we need to supply less and less water.
225. So that's a basic introduction to some
226. of the fundamental concepts of environmental control and life
227. support.
228. And we can actually look at the difference
229. that it makes to the mass that you
230. have to launch in terms of how much you
231. recycle different elements.
232. So you can see looking at this plot, far and away the most
233. important thing is the recovery of waste water.
234. Because if you have no recycling, a completely open
235. environmental control and life support system--
236. we look at it at a level of 100--
237. we cut down by over a factor of two just
238. by recovering our wastewater.
239. And then re-generating carbon dioxide
240. where we don't throw away the lithium hydroxide
241. but we have a reusable scrubbing unit, that
242. helps us a little bit.
243. Getting the oxygen back from the CO2 gets us down a little bit
244. further.
245. We don't currently recycle our solid waste to produce food.
246. So we don't do that.
247. Of course, if you have a small leak in the spacecraft
248. and no spacecraft is 100% airtight,
249. you're always going to be losing a little bit of oxygen
250. and nitrogen and you'll have to make that supply up.
251. So that makes a little difference.
252. And so on.
253. There's a few small areas here.
254. But basically it's the water, the CO2,
255. and the oxygen recovery which are the big factors.
256. And we're going to look at those in a lot more detail
257. and see how we actually do this type of recycling
258. in our environmental control and life support systems.
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