NASA SP-413 Space Settlements - Saint Ann's School

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96 NASA SP-413 — SPACE SETTLEMENTS — A Design Study During acceleration the payload is tightly held in the bucket, but when lunar escape velocity is reached and the velocity is correct the payload is released. Since the bucket is constrained by the track to follow the curve of the lunar surface, the payload rises relative to the surface and proceeds into space. Each bucket then enters a 3 km region where a trackside linear synchronous motor decelerates it at over 100 g. It is returned to the loading end of the track along a track parallel to the accelerator. At the load end of the track the liquid helium used to cool the superconducting magnets is replenished, and a new payload loaded. Then the bucket is steered to the start of the accelerator for another circuit. Figure 5-19 shows the mass launcher schematically. More details are given in appendix F. TABLE 5-13 — ANNUAL MASS IMPORTS Imports Crew consumables Maintenance supplies Crew rotation* Atmosphere leak replacement Mass, t/yr 270 100 14 18 Total 402 * The same mass is also transported from Moon to Earth. TABLE 5-14 — LUNAR BASE EARTH-SUPPLIED MASS System Mining and conveyor system Housing and life support Technical support Launcher Power plant (200MW + 10%) Mass, t 250 2,400 500 4,000 9,900 Total 17,050 TABLE 5-15 — LUNAR BASE POWER REQUIREMENTS System Power, MW Launcher 192 Mining 0.7 Compaction 7.15 Living quarters .15 Total 200 With a 70 percent duty cycle, this system can launch 1.1 Mt/yr. To assure this duty cycle during lunar night as well as lunar day, two complete mass launchers are necessary. A nuclear power plant rather than a solar plant is required so the operation can continue through the lunar night. Power and Supply Several nuclear reactor single-cycle helium-Brayton plants of 10 to 50 MW each are used instead of a single big plant because the smaller plants can be transported assembled and become ready to operate by use of space shuttle main engines. The redundancy of several smaller systems is attractive, especially since the plants need to be taken off-line for refueling every year or two. The total capacity is 220 MW and the total mass is 9900 t, including a 10 percent design factor. The mass of the power plant is estimated using the value of 45 t/MW, which is projected to be applicable to nuclear plants within the decade. 1 Shielding will be provided by lunar material. 1 Austin, G., NASA-Marshall Space Flight Center, personal communication, June, 1975. Figure 5-19 — The mass launcher. Chapter 5 — A Tour Of The Colony
NASA SP-413 — SPACE SETTLEMENTS — A Design Study 97 Figure 5-20 — The mass catcher. THE MASS CATCHER AT L2 The problem of collecting the stream of material launched by the mass-driver is solved by a kind of automated “catcher’s mitt, “ the mass catcher, located at L2. Although the catchers are fully automated there is a 2-person space station at L2 for maintenance personnel. This station is adequately shielded against possible hits by stray payloads. Because it would be dangerous to navigate in the vicinity of the catcher while the launcher is operating, you are not able to visit the catcher personally. Instead you learn about it from an operator who is at the Moon base on recreation leave. He tells you that the mass catcher is an active device to capture payloads of lunar material shot by the mass launcher. The payloads are solid blocks 0.20 m in diameter, made of compacted and sintered lunar soil. Each payload has a mass of 10 kg and arrives at L2 with a speed of 200 m/s. The catcher is in the form of a thin, light net, 10 m 2 in area, which is manipulated by three cables to position the net anywhere within an equilateral triangle. The cables are wound on reels which move on three closed loop tracks Each side of the equilateral triangle is 1 km, thus providing a 0.43 X 10 6 m 2 catch area The total mass of the catcher is 220 t. Station-Keeping With the Rotary Pellet Launcher You learn that the mass catcher uses an unusual propulsion device — a rotory pellet launcher — to position the catcher so that it is always facing the incoming stream of payloads. Furthermore, this device provides a counterthrust to the force of some 2000 N imparted to the catcher by the stream. Further details of the mass catcher are provided in appendix G, and because of their importance the trajectories from the Moon to L2 and their relation to stationkeeping are described in appendix H. The mass catcher is illustrated in figure 5-20. Figure 5-21 — The rotary pellet launcher Chapter 5 — A Tour Of The Colony
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