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Gary Davis Robert Estes Scott Glubke

Micro Arcsecond X-ray Imaging Mission, Pathfinder (MAXIM-PF). Propulsion. Gary Davis Robert Estes Scott Glubke. May 13-17, 2002. Launch. Insertion. L2. Lunar Orbit. Mid Course Corrections. projection onto ecliptic plane (RSR frame). Functional Requirements & Assumptions (1 of 3).

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Gary Davis Robert Estes Scott Glubke

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  1. Micro Arcsecond X-ray Imaging Mission, Pathfinder (MAXIM-PF) Propulsion Gary Davis Robert Estes Scott Glubke May 13-17, 2002

  2. Launch Insertion L2 Lunar Orbit Mid Course Corrections projection onto ecliptic plane(RSR frame) Functional Requirements & Assumptions (1 of 3) • General • Range Safety: EWR-127-1 and MIL-STD-1522A • (launch/processing @ KSC/CCAS) • Class A mission: single fault tolerant • Transfer stage needs only axial thrust, ACS thrust • Optics Hub, Detector, and Free Flyers need thrust in all directions • 1 year in Phase1 with 45 reors., 4 years in Phase2 with 45 reorientations. • Thruster contamination and EM issues can be “engineered” • Broad thrust ranges • Transfer to L2 • All S/C are attached together • High thrust chemical propulsion needed for: • ELV velocity dispersions • Mid-course corrections during transfer trajectory • Insertion maneuver near L2 • Transfer stage is jettisoned • Assume need to safe/vent this stage (inject into helio orbit) LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center

  3. Functional Requirements & Assumptions (2 of 3) • “Lissajous Stabilization” at L2 • Thrust needed on all S/C to maintain the Lissajous orbit • Assume that science observations are stopped for stabilization maneuvers • Formation Keeping • Optics Hub S/C is the leader and does not need to perform any formation keeping maneuvers • Detector S/C follows the leader and need to perform maneuvers to keep up • Free Flyer Optics S/C also need to perform formation keeping maneuvers • Reorientation Maneuvers • Optics Hub is assumed to rotate in place (it’s the leader) • Detector and free flyer S/C maneuver to match the Optics Hub’s orientation • 10 degree reorientation assumed • Phase1 = 1 day, Phase2 = 7 days LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center

  4. Functional Requirements & Assumptions (3 of 3) • Lissajous Stabilization Thrust Control: • For Lissajous stabilization, the S/C can be reoriented to align thrusters with desired velocity direction • Maneuvers will be short so power should not be a problem • Plan maneuvers after observations, before the next reorientation to minimize science downtime • Formation Keeping (& reor.) Thrust Control: • Translational thrust needed in ALL directions • 6 DOF (+/- X, Y, & Z) • Maximum thrust needed is approx. 20 mN • Minimum thrust needed is approx. 3X10-4 mN (this is < 1 microN) • A five order of magnitude thrust range • Formation Keeping (& reor.) ACS Control: • Torques needed about all axes • 6 DOF (+/- Roll, Pitch, & Yaw) • Minimum Impulse Bit = 20 microNs LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center

  5. Launch Insertion L2 Lunar Orbit Mid Course Corrections projection onto ecliptic plane(RSR frame) Transfer Stage Requirements • L2 Propulsion Insertion Module • Carries All S/C attached together • Axial del-V thrust, 3 axis ACS • High thrust chemical system • Functions: • Launch Vehicle Correction • Contingency • Mid-Course Correction (MCC) • Lissajous Orbit Insertion (LOI) • Transfer to L2 • Transfer from ELV trajectory to L2 orbit: 200 m/s • Assumes a Delta-IV Launch Vehicle C3 = -0.7 km^2/s^2 • Transfer stage is jettisoned after LOI • Needs to be safed (vented, helio orbit) to meet orbit debris requirements LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center

  6. Detector S/C Requirements • Detector S/C is a follower at L2 • Phase1 Maneuvers: Acceleration Delta-V • Lissajous Stabilization N/A 25 m/s per year in Phase1 • Formation Keeping 1X10-6 m/s^2 0.0864 m/s / day (tot=32) • Reorientation 1.9X-5 m/s^2 1.61 m/s ,1 day reor. (tot=117*) • Phase2 Maneuvers: • Lissajous Stabilization N/A 100 m/s in Phase2 • Formation Keeping 1.1X10-5 m/s^2 .95 m/s / day (tot=1389) • Reorientation 3.81X10-5 23.1 m/s , 7 day reor. (tot=2042*) *Includes formation keeping during reorientations and 1.5x correction factor • Note: Phase1 = 1yr, 45 reorientations, Phase2 = 4yr, 45 reorientations LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center

  7. Optics Hub S/C Requirements • Optics Hub S/C is the leader at L2 • Phase1 Maneuvers: Acceleration Delta-V • Lissajous Stabilization N/A 25 m/s in Phase1 • Formation Keeping None needed (hub is the leader) • Reorientation None needed (hub is the leader) • Phase2 Maneuvers: • Lissajous Stabilization N/A 100 m/s in Phase2 • Formation Keeping None needed (hub is the leader) • Reorientation None needed (hub is the leader) LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center

  8. Free Flyer S/C (6) Requirements • Free Flyer Optics S/C (all 6) are followers at L2 • Phase1 Maneuvers: Acceleration Delta-V • Lissajous Stabilization N/A (not deployed from Optics Hub S/C) • Formation Keeping N/A (not deployed from Optics Hub S/C) • Reorientation N/A (not deployed from Optics Hub S/C) • Phase2 Maneuvers: • Lissajous Stabilization N/A 100 m/s in Phase2 • Formation Keeping 1X10-6 m/s^2 0.0864 m/s per day (tot=380*) • Reorientation 1X10-9 m/s^2 6X10-4 m/s/7 day reor. (tot=12*) *Includes formation keeping during reorientations and 3x correction factor • Note: Phase1 = 1yr, 45 reorientations, Phase2 = 4yr, 45 reorientations LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center

  9. Transfer Stage Propulsion Design • Transfer Stage • Monopropellant hydrazine using unregulated pressurization • 500 kg total mass for the stage • 410 kg of hydrazine • 3 kg of pressurant • 40 kg for a 42 in diameter titanium tank with AF-E-322 diaphragm • 42 kg remains for thrusters/plumbing components/structure/sep systems • Reduce debris hazard after separation: venting/orbit change Thrusters • Needs a thrust for a 50 m/s burn to be performed in < 1 hour • 25 N engines located (in pairs) in 4 locations (8 engines total) Delta-V LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center

  10. Optics Hub Architecture • Optics Hub: • L2 Stabilization • 8 hydrazine thrusters, single diaphragm tank, blowdown • Simple high thrust design • 12 MEMS cold gas ACS thrusters • Mass: wet = 77 kg, dry=15 kg • Power: 5 W (valve and heater power accounted by other subsystems) • Cost:$1000k LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center

  11. Detector Architecture • Detector: • L2 Stabilization • 8 hydrazine thrusters, single diaphragm tank, blowdown • Simple high thrust design • 24 kg hydrazine • Formation keeping and reorientation • 4 – 3nozzle Pulsed Plasma Thrusters (PPT’s = $250k each) • 87 kg Teflon • Mass: wet = 153 kg, dry=42 kg • Maneuver power : 300 W (valve and heater power accounted by other subsystems) • Cost:$2000k LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center

  12. Free Flyer Architecture • Free Flyer • L2 Stabilization • 8 hydrazine thrusters, single diaphragm tank, blowdown • Simple high thrust design • 14 kg hydrazine • Formation keeping and reorientation • 4 – 3nozzle Pulsed Plasma Thrusters (PPT’s = $250k each) • 8 kg Teflon • Mass: wet = 64 kg, dry=42 kg • Maneuver power: 10 W (valve and heater power accounted by other subsystems) • Cost: $2000k LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center

  13. Detector, Free Flyer: PPT LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center

  14. Detector, Free Flyer: Low Thrust Options, Typical performance LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center

  15. Detector, Free Flyer: Low Thrust Options • FEEP, Colloid: thrust too low, modulation range too narrow • Ion, Hall: no pulse mode, limited life (through put), modulation range too narrow • PPT • Adequate thrust • Pulse mode • Variable pulse frequency during “continuous” mode • Broad thrust modulation range: 100x may be possible (achieved via capacitor charge level and frequency) • No grid or neutralizer erosion • Life extensions via: • Increased capacitor capability (reducing ratio of charge used/max charge greatly increases life) • Multiple/replenishable spark plugs LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center

  16. Propulsion Summary • High thrust: chemical propulsion is standard technology • Low Thrust: Key Driving Requirement • Thruster selection (PPT) sensitive to combined flight dynamics and ACS requirements • No current technologies exist which meet requirements • PPT unit flight demonstrated on EO-1 • Significant life extension required for any “electric” technologies LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center

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