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

Final Version LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center Propulsion Page 2 Functional Requirements & Assumptions (1 of 3)  General  Range Safety: EWR and MIL-STD-1522A  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) projection onto ecliptic plane (RSR frame) Mid Course Corrections Lunar Orbit Launch Insertion L2

Final Version LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center Propulsion Page 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 Functional Requirements & Assumptions (2 of 3)

Final Version LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center Propulsion Page 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

Final Version LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center Propulsion Page 5  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 Transfer Stage Requirements projection onto ecliptic plane (RSR frame) Mid Course Corrections Lunar Orbit Launch Insertion L2

Final Version LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center Propulsion Page 6  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^ m/s / day (tot=32)  Reorientation 1.9X-5 m/s^ 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 3.81X 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 Detector S/C Requirements

Final Version LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center Propulsion Page 7  Optics Hub S/C is the leader at L2  Phase1 Maneuvers:AccelerationDelta-V  Lissajous StabilizationN/A25 m/s in Phase1  Formation KeepingNone needed (hub is the leader)  ReorientationNone needed (hub is the leader)  Phase2 Maneuvers:  Lissajous StabilizationN/A100 m/s in Phase2  Formation KeepingNone needed (hub is the leader)  ReorientationNone needed (hub is the leader) Optics Hub S/C Requirements

Final Version LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center Propulsion Page 8  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^ 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 Free Flyer S/C (6) Requirements

Final Version LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center Propulsion Page 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

Final Version LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center Propulsion Page 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

Final Version LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center Propulsion Page 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

Final Version LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center Propulsion Page 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

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

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

Final Version LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center Propulsion Page 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

Final Version LAI MAXIM-PF May 13-17, 2002 Goddard Space Flight Center Propulsion Page 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