1 00:00:12,045 --> 00:00:12,679 Once the fuel 2 00:00:12,679 --> 00:00:15,648 runs out, there is no more mission. 3 00:00:16,583 --> 00:00:17,684 You have to decommission. 4 00:00:17,684 --> 00:00:20,553 So the fuel is very important for the spacecraft. 5 00:00:20,553 --> 00:00:22,922 It can only last as long as the fuel. 6 00:00:22,989 --> 00:00:30,930 Title: Moving Roman - Propulsion 7 00:00:32,332 --> 00:00:35,335 Telescopes like NASA's Nancy Grace Roman Space 8 00:00:35,335 --> 00:00:39,539 Telescope move and point using two methods. 9 00:00:39,539 --> 00:00:42,742 There are reaction wheels to turn the spacecraft with precision 10 00:00:42,876 --> 00:00:46,379 and then hold it steady. 11 00:00:46,379 --> 00:00:50,283 And then there are thrusters that use propellant for large motions 12 00:00:50,483 --> 00:00:55,255 to push the spacecraft into its correct orbit and maintain that orbit. 13 00:00:55,655 --> 00:00:58,358 All which require fuel. 14 00:01:04,464 --> 00:01:06,533 Before entering the large clean room, 15 00:01:06,533 --> 00:01:09,636 the propulsion tanks were assembled in a smaller lab. 16 00:01:11,771 --> 00:01:15,208 So right now we're looking at the propulsion system for the Roman 17 00:01:15,208 --> 00:01:17,844 Space Telescope. 18 00:01:21,915 --> 00:01:22,282 Today 19 00:01:22,282 --> 00:01:25,385 we put our last tank on the propulsion support frame. 20 00:01:25,552 --> 00:01:31,024 The propulsion support frame is the frame that's supporting everything. 21 00:01:32,025 --> 00:01:33,693 The four tanks seen here 22 00:01:33,693 --> 00:01:35,762 were each carefully lifted individually. 23 00:01:37,497 --> 00:01:40,667 The deck that supports them gets positioned below that tank. 24 00:01:41,701 --> 00:01:45,505 These four tanks fuel a series of 24 thrusters 25 00:01:45,738 --> 00:01:47,941 with two different sizes. 26 00:01:48,942 --> 00:01:49,909 On the sides. 27 00:01:49,909 --> 00:01:54,914 We have all of the engines, so we have four sets up top. 28 00:01:54,948 --> 00:01:56,950 Those are our upper ACS’s. 29 00:01:56,950 --> 00:01:58,485 We have four sets at the bottom. 30 00:01:58,485 --> 00:02:00,553 Those are our lower ACS engines. 31 00:02:00,954 --> 00:02:04,757 And then at the bottom over here, those big triangle pods, 32 00:02:06,159 --> 00:02:07,760 those are all of our Delta V engines. 33 00:02:07,760 --> 00:02:10,697 So those will do our big maneuvers. 34 00:02:14,334 --> 00:02:15,902 With the tanks in position. 35 00:02:15,902 --> 00:02:21,274 They're ready for integration into the telescope spacecraft bus, 36 00:02:21,274 --> 00:02:26,379 which happens in NASA's largest clean room. 37 00:02:31,651 --> 00:02:35,388 Now, thrusters use conservation of momentum, ignited 38 00:02:35,388 --> 00:02:40,126 fuel creates expanding gas, which exits the engines in one direction. 39 00:02:40,360 --> 00:02:43,029 And the observatory moves in the opposite direction. 40 00:02:44,097 --> 00:02:47,133 The thrusters are so efficient in the vacuum of space 41 00:02:47,534 --> 00:02:50,403 that they can be surprisingly small to move 42 00:02:50,403 --> 00:02:52,839 the 18 thousand pound spacecraft. 43 00:02:53,606 --> 00:02:56,709 This is all it needs. 44 00:03:29,876 --> 00:03:32,078 With the thrusters on the outside of Roman, 45 00:03:32,078 --> 00:03:35,448 the propellant tanks will sit within the observatory central cylinder 46 00:03:35,682 --> 00:03:43,489 close to their teammates, the reaction wheels. 47 00:03:54,567 --> 00:03:57,403 When the reaction wheels get to their maximum speed, 48 00:03:57,670 --> 00:04:01,040 they have to be slowed down again. 49 00:04:02,141 --> 00:04:05,612 The thrusters fire to balance the angular momentum change 50 00:04:05,979 --> 00:04:10,550 so that the spacecraft doesn't turn as the wheels slow. 51 00:04:13,386 --> 00:04:15,722 Since fuel is limited, 52 00:04:15,722 --> 00:04:18,891 it usually determines the lifespan of distant 53 00:04:18,891 --> 00:04:21,394 spacecraft. 54 00:04:22,061 --> 00:04:24,631 Luckily, the telescope can also point 55 00:04:24,731 --> 00:04:27,734 only using electricity. 56 00:04:27,734 --> 00:04:30,003 But how reaction wheels work. 57 00:04:30,003 --> 00:04:46,986 That's another story.