Micro Arcsecond Xray Imaging Mission Pathfinder MAXIMPF Final

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

Functional Requirements & Assumptions (1 of 3) Final Version ¨ General · Range Safety: EWR-127 -1 and MIL-STD-1522 A · · · · (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 Phase 1 with 45 reors. , 4 years in Phase 2 with 45 reorientations. Thruster contamination and EM issues can be “engineered” Broad thrust ranges ¨ Transfer to L 2 · All S/C are attached together · High thrust chemical propulsion needed for: · ELV velocity dispersions · Mid-course corrections during transfer trajectory · Insertion maneuver near L 2 · 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 Launch Insertion L 2 Lunar Orbit Mid Course Corrections projection onto ecliptic plane (RSR frame) 2

Functional Requirements & Assumptions (2 of 3) Final Version ¨ “Lissajous Stabilization” at L 2 · 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 performation 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 Phase 1 = 1 day, Phase 2 = 7 days LAI MAXIM-PF May 13 -17, 2002 Goddard Space Flight Center 3

Functional Requirements & Assumptions (3 of 3) Final Version ¨ 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 m. N Minimum thrust needed is approx. 3 X 10 -4 m. N (this is < 1 micro. N) 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 micro. Ns LAI MAXIM-PF May 13 -17, 2002 Goddard Space Flight Center 4

Transfer Stage Requirements Final Version ¨ L 2 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 L 2 Launch Insertion L 2 Lunar Orbit Mid Course Corrections projection onto ecliptic plane (RSR frame) · Transfer from ELV trajectory to L 2 orbit: 200 m/s · Assumes a Delta-IV Launch Vehicle C 3 = -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 5

Detector S/C Requirements Final Version ¨ Detector S/C is a follower at L 2 · Phase 1 Maneuvers: Acceleration Delta-V · Lissajous Stabilization N/A 25 m/s per year in Phase 1 · Formation Keeping 1 X 10 -6 m/s^2 0. 0864 m/s / day (tot=32) · Reorientation 1. 9 X-5 m/s^2 1. 61 m/s , 1 day reor. (tot=117*) · Phase 2 Maneuvers: · Lissajous Stabilization N/A 100 m/s in Phase 2 · Formation Keeping 1. 1 X 10 -5 m/s^2. 95 m/s / day (tot=1389) · Reorientation 3. 81 X 10 -5 23. 1 m/s , 7 day reor. (tot=2042*) *Includes formation keeping during reorientations and 1. 5 x correction factor ¨ Note: Phase 1 = 1 yr, 45 reorientations, Phase 2 = 4 yr, 45 reorientations LAI MAXIM-PF May 13 -17, 2002 Goddard Space Flight Center 6

Optics Hub S/C Requirements Final Version ¨ Optics Hub S/C is the leader at L 2 · Phase 1 Maneuvers: · Lissajous Stabilization · Formation Keeping · Reorientation · Phase 2 Maneuvers: · Lissajous Stabilization · Formation Keeping · Reorientation LAI MAXIM-PF May 13 -17, 2002 Goddard Space Flight Center Acceleration Delta-V N/A 25 m/s in Phase 1 None needed (hub is the leader) N/A 100 m/s in Phase 2 None needed (hub is the leader) 7

Free Flyer S/C (6) Requirements Final Version ¨ Free Flyer Optics S/C (all 6) are followers at L 2 · Phase 1 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) · Phase 2 Maneuvers: · Lissajous Stabilization N/A 100 m/s in Phase 2 · Formation Keeping 1 X 10 -6 m/s^2 0. 0864 m/s per day (tot=380*) · Reorientation 1 X 10 -9 m/s^2 6 X 10 -4 m/s/7 day reor. (tot=12*) *Includes formation keeping during reorientations and 3 x correction factor ¨ Note: Phase 1 = 1 yr, 45 reorientations, Phase 2 = 4 yr, 45 reorientations LAI MAXIM-PF May 13 -17, 2002 Goddard Space Flight Center 8

Transfer Stage Propulsion Design Final Version ¨ 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 9

Optics Hub Architecture Final Version ¨ Optics Hub: · L 2 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: $1000 k LAI MAXIM-PF May 13 -17, 2002 Goddard Space Flight Center 10

Detector Architecture Final Version ¨ Detector: · L 2 Stabilization · 8 hydrazine thrusters, single diaphragm tank, blowdown · Simple high thrust design · 24 kg hydrazine · Formation keeping and reorientation · 4 – 3 nozzle Pulsed Plasma Thrusters (PPT’s = $250 k each) · 87 kg Teflon · Mass: wet = 153 kg, dry=42 kg · Maneuver power : 300 W (valve and heater power accounted by other subsystems) · Cost: $2000 k LAI MAXIM-PF May 13 -17, 2002 Goddard Space Flight Center 11

Free Flyer Architecture Final Version ¨ Free Flyer · L 2 Stabilization · 8 hydrazine thrusters, single diaphragm tank, blowdown · Simple high thrust design · 14 kg hydrazine · Formation keeping and reorientation · 4 – 3 nozzle Pulsed Plasma Thrusters (PPT’s = $250 k each) · 8 kg Teflon · Mass: wet = 64 kg, dry=42 kg · Maneuver power: 10 W (valve and heater power accounted by other subsystems) · Cost: $2000 k LAI MAXIM-PF May 13 -17, 2002 Goddard Space Flight Center 12

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

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

Detector, Free Flyer: Low Thrust Options Final Version ¨ 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: 100 x 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 15

Propulsion Summary Final Version ¨ 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 16