Development of a Cold Gas Propulsion System for the ... - SSL - MIT

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N newton Pa pascal psi pounds per square inch psia pounds per square inch absolute psig pounds per square inch gauge (relative to surrounding atmosphere) RPM revolutions per minute s second SCFM standard cubic feet per minute (standard conditions of 60°F and 14.7 psia) V volt Vdc volts of direct current W watt ° degree (angular measurement) °C degrees Celsius °F degrees Fahrenheit Ω ohm Variables and Constants
1 Introduction The TALARIS (Terrestrial Artificial Lunar And Reduced gravIty Simulator) hopper is a small prototype flying vehicle designed to serve as an Earth-based testbed for guidance, navigation, and control (GNC) algorithms that will be used to explore lunar and other planetary surfaces. To date, nearly all robotic exploration on the surface of the Moon and other planets has been done by stationary landers or wheeled rovers. Hoppers would open up new modes of exploration with their alternate form of mobility. However, because they are a new technology without the long heritage of landers and rovers, there is a greater need for testing to reduce the risk associated with hoppers. The TALARIS testbed provides the opportunity to develop and mature hopper-based GNC algorithms on Earth, which allows for a more controlled environment and easier human access for modifications, upgrades, and repairs if necessary. A hop consists of three main phases: propulsive ascent, traverse flight, and soft landing. A commanded maneuver of this type has been performed off the Earth once, by the Surveyor 6 spacecraft on the Moon. On November 17, 1967, after Surveyor 6 had been sitting on the lunar surface for a week, the spacecraft’s three liquid-fueled vernier rocket engines were reignited and fired for 2.5 s [1]. The control system was set such that the spacecraft would tilt 7° to the west upon liftoff, and the thrust generated was sufficient to cause the spacecraft to rise to an altitude of about 3.5 m and to land 2.4 m away from its starting point. This allowed Surveyor 6 to send back images of the surface disturbances at its initial landing site, providing information on mechanical properties of the lunar surface as well as the effects of firing rocket engines near the surface. Furthermore, the displacement of the spacecraft provided a baseline for stereoscopic viewing and photogrammetric mapping of the surrounding lunar terrain [1]. However, the Surveyor 6 hop is merely the tip of the iceberg in terms of the potential value that could be gained from exploring with hoppers. Hoppers could improve planetary exploration from both the science and engineering perspectives. Hoppers can travel more quickly than rovers, and they can also cover a greater diversity of terrain. Hoppers could fly over large obstacles and traverse steep inclines, possibly even hopping into or out of craters. They might also provide unique opportunities for science during a hop, such as low-altitude aerial observations or examinations of cliff faces or canyon walls at various heights. For more in-depth analysis of the ways in which hoppers might contribute to planetary exploration objectives, see [2] and [3]. Hoppers have certain advantages from an engineering perspective as well. For a rover, initial landing and travel over the surface involve two dissimilar types of propulsion; by contrast, a hopper can be 19
Page 1: Development of a Cold Gas Propulsio
Page 5: Abstract The TALARIS (Terrestrial A
Page 9 and 10: Table of Contents List of Figures .
Page 11: 7 Ongoing and Future Work .........
Page 14 and 15: Figure 6-6. Identification of thrus
Page 17 and 18: Notation Acronyms and Abbreviations
Page 19: N newton Pa pascal psi pounds per s
Page 23 and 24: the idea of hopping was born, and i
Page 25 and 26: However, as stated before, this doe
Page 27 and 28: Figure 2-3. Diagram of ACAT lander
Page 29 and 30: An alternate approach to resolving
Page 31 and 32: accurate conditions for testing GNC
Page 33 and 34: Ballistic hops tend to use less pro
Page 35 and 36: 2.3.2 Comparison of Cold Gas and Mo
Page 37 and 38: Handling propellant There are sever
Page 39 and 40: and if the cold gas system was foun
Page 41 and 42: 3 TALARIS CGSE Design Framework Aft
Page 43 and 44: Figure 3-1. Scaling of TALARIS terr
Page 45 and 46: (3) Providing attitude control Ther
Page 47 and 48: Figure 3-2 also shows the body coor
Page 49 and 50: 4 Modeling and Flow Control Compone
Page 51 and 52: 4.1.2 Rocket Propulsion Equations L
Page 53 and 54: variables in equation (4-8) deal wi
Page 55 and 56: equations. Equation (4-10) was then
Page 57 and 58: that of helium (0.227 MPa = 32.9 ps
Page 59 and 60: thruster solenoid valve, and chambe
Page 61 and 62: where
Page 63 and 64: discussed later in section 6.3.4, t
Page 65 and 66: The flight profile begins with maxi
Page 67 and 68: hop, any given valve or regulator o
Page 69 and 70: esponse time was an important perfo
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directly opens and closes the main
Page 73 and 74:
If 1D isentropic flow is assumed, t
Page 75 and 76:
5 Single-Stream Component Testing A
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the solenoid valve, and a pressure
Page 79 and 80:
As indicated in Figure 5-3, initial
Page 81 and 82:
Figure 5-5. CGSE high side as const
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Figure 5-7 illustrates several aspe
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6 Full Eight-Thruster Flight System
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Figure 6-2. TALARIS CGSE assembled
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stream tests revealed that changes
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Figure 6-5. Original CGSE control c
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other constraints. This was difficu
Page 95 and 96:
variables (such as number of thrust
Page 97 and 98:
One solution to this problem would
Page 99 and 100:
One of the characterization tests w
Page 101 and 102:
or more thrusters were firing toget
Page 103 and 104:
Table 6-3. Valve timing metrics dur
Page 105 and 106:
Figure 6-11. Redesigned CGSE contro
Page 107 and 108:
The imaginary simplified thruster c
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traverse phase of a hop and involve
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Figure 7-3. GNC data from 3-DOF tes
Page 113 and 114:
Tests on this vertical stand demons
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control the belay line can be put u
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accounting for changes in thrust le
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development under the supervision o
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documenting progress takes time whi
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were encountered, it was harder to
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[10] Bryant, K. M., Knight, C. J.,
Page 127 and 128:
[31] Canadian Centre for Occupation
Page 129 and 130:
[50] ISA - The Instrumentation, Sys
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