Final Version

Gary DavisRobert EstesScott Glubke

Propulsion

May 13-17, 2002

Micro Arcsecond X-ray Imaging Mission, Pathfinder (MAXIM-PF)

LAI MAXIM-PF May 13-17, 2002Goddard Space Flight Center

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Final Version

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)

projection onto ecliptic plane(RSR frame)

Mid Course Corrections

Lunar Orbit

Launch

Insertion

L2

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Final Version

“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)

LAI MAXIM-PF May 13-17, 2002Goddard Space Flight Center

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Final Version

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, 2002Goddard Space Flight Center

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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

LAI MAXIM-PF May 13-17, 2002Goddard Space Flight Center

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Final Version

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

Detector S/C Requirements

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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)

Optics Hub S/C Requirements

LAI MAXIM-PF May 13-17, 2002Goddard Space Flight Center

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Final Version

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

Free Flyer S/C (6) Requirements

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Final Version

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, 2002Goddard Space Flight Center

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Final Version

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, 2002Goddard Space Flight Center

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Final Version

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, 2002Goddard Space Flight Center

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Final Version

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, 2002Goddard Space Flight Center

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Final Version

Detector, Free Flyer: PPT

LAI MAXIM-PF May 13-17, 2002Goddard Space Flight Center

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Detector, Free Flyer: Low Thrust Options, Typical

performance

TECHNOLOGY Isp min I-bitpower,

minpower, max mN

thruster wt., kg

system, kg

PPT (gen) 500-1400 1e-5-150e-5 5 150 .01-3 1.5 5

PPT teflon 200-1400 5.00E-05 5 70 .1-4.5 1.5 5gas PPT 5000 1.00E-05 5 150 .1-1 1.5 6.5

Cesium FEEP 9000 1.00E-08 3 370 .01-2.8 0.45 3

small ion1800-3500 no pulse 100 500 5-20 2.5-5

micro ion2000-3000 no pulse 10 50 .05-.5 <1

Colloid 500-1450 1.00E-08 2 10 .001-.3

LAI MAXIM-PF May 13-17, 2002Goddard Space Flight Center

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Final Version

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, 2002Goddard Space Flight Center

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Final Version

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