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

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7.1.2 Vertical Test Stand For initial validation tests with the CGSE vertical thrusters, a test stand was built as an evolution of the one that had been used for 1-DOF vertical testing of the EDFs. In that original stand, the TALARIS hopper had been suspended between two arms which slid up and down on two tall posts but prevented the vehicle from rotating about any of its axes [17]. The new vertical test stand could be used in this way as well. However, in addition to having sliders, it also had rotational bearings at the points where it attached to the TALARIS hopper. Either the sliders or the bearings could be locked if desired to constrain particular degrees of freedom. Furthermore, the spacing of the vertical posts could be changed to allow TALARIS to be mounted in the stand such that the bearings could allow for rotation about either the Y or Z axes. Thus, the following degrees of freedom could all be tested in the new vertical stand: • 1-DOF altitude (travel parallel to X axis) • 1-DOF attitude (either pitch about the Y axis or yaw about the Z axis) • 2-DOF altitude plus attitude (travel parallel to X plus either pitch about Y or yaw about Z) Figure 7-4 shows the TALARIS hopper in the new vertical test stand. Figure 7-4. TALARIS hopper in vertical test stand, allowing both altitude and attitude control testing. 110
Tests on this vertical stand demonstrated 1-DOF attitude control, as shown in Figure 7-5. Figure 7-5. Yaw disturbance rejection demonstrating 1-DOF attitude control of TALARIS hopper. In the test shown in Figure 7-5, the sliders on the vertical test stand were locked, and the hopper was only free to yaw about its Z axis. (Although the test stand prevented the hopper from rolling or pitching, the plot shows some IMU drift, particularly in roll.) The attitude of the hopper was disturbed, but the vertical CGSE thrusters were able to return it to stability. Although 1-DOF attitude control was verified on the vertical test stand, the tests involving altitude were inconclusive. The EDFs still were not ready when vertical validation testing began, so a temporary weight-relief system was devised, utilizing a counterweight which is visible behind the vertical stand at the center right of Figure 7-4. Unfortunately, this applied undesirable dynamics to the vehicle during altitude tests. Furthermore, although the vertical stand was designed to allow only one degree of rotational freedom, when the sliders were unlocked they could travel at slightly different rates, and this meant that there was some degree of both pitch and yaw possible in altitude-plus-attitude testing. 111
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Development of a Cold Gas Propulsio
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Abstract The TALARIS (Terrestrial A
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Table of Contents List of Figures .
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7 Ongoing and Future Work .........
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Figure 6-6. Identification of thrus
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Notation Acronyms and Abbreviations
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N newton Pa pascal psi pounds per s
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1 Introduction The TALARIS (Terrest
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the idea of hopping was born, and i
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However, as stated before, this doe
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Figure 2-3. Diagram of ACAT lander
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An alternate approach to resolving
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accurate conditions for testing GNC
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Ballistic hops tend to use less pro
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2.3.2 Comparison of Cold Gas and Mo
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Handling propellant There are sever
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and if the cold gas system was foun
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3 TALARIS CGSE Design Framework Aft
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Figure 3-1. Scaling of TALARIS terr
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(3) Providing attitude control Ther
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Figure 3-2 also shows the body coor
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4 Modeling and Flow Control Compone
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4.1.2 Rocket Propulsion Equations L
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variables in equation (4-8) deal wi
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equations. Equation (4-10) was then
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that of helium (0.227 MPa = 32.9 ps
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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
Page 71 and 72: 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
Page 77 and 78: 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
Page 83 and 84: Figure 5-7 illustrates several aspe
Page 85 and 86: 6 Full Eight-Thruster Flight System
Page 87 and 88: Figure 6-2. TALARIS CGSE assembled
Page 89 and 90: stream tests revealed that changes
Page 91 and 92: Figure 6-5. Original CGSE control c
Page 93 and 94: 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
Page 109 and 110: traverse phase of a hop and involve
Page 111: Figure 7-3. GNC data from 3-DOF tes
Page 115 and 116: control the belay line can be put u
Page 117 and 118: accounting for changes in thrust le
Page 119 and 120: development under the supervision o
Page 121 and 122: documenting progress takes time whi
Page 123 and 124: were encountered, it was harder to
Page 125 and 126: [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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Development of a Cold Gas Propulsion System for the ... - SSL - MIT

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