Gary Davis

1
Micro Arcsecond X-ray Imaging Mission, Pathfinder
(MAXIM-PF)
Propulsion
Gary Davis Robert Estes Scott Glubke
May 13-17, 2002
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Functional Requirements Assumptions (1 of 3)

• General
• Range Safety EWR-127-1 and MIL-STD-1522A
• (launch/processing _at_ 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)

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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 (its
  the leader)
• Detector and free flyer S/C maneuver to match the
  Optics Hubs orientation
• 10 degree reorientation assumed
• Phase1 1 day, Phase2 7 days

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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 lt 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

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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
  km2/s2
• Transfer stage is jettisoned after LOI
• Needs to be safed (vented, helio orbit) to meet
  orbit debris requirements

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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/s2 0.0864
  m/s / day (tot32)
• Reorientation 1.9X-5 m/s2 1.61 m/s ,1
  day reor. (tot117)
• Phase2 Maneuvers
• Lissajous Stabilization N/A 100 m/s in
  Phase2
• Formation Keeping 1.1X10-5 m/s2 .95
  m/s / day (tot1389)
• Reorientation 3.81X10-5 23.1 m/s , 7
  day reor. (tot2042)
• Includes formation keeping during reorientations
  and 1.5x correction factor
• Note Phase1 1yr, 45 reorientations, Phase2
  4yr, 45 reorientations

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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)

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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/s2 0.0864
  m/s per day (tot380)
• Reorientation 1X10-9 m/s2 6X10-4
  m/s/7 day reor. (tot12)
• Includes formation keeping during reorientations
  and 3x correction factor
• Note Phase1 1yr, 45 reorientations, Phase2
  4yr, 45 reorientations

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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 lt 1 hour
• 25 N engines located (in pairs) in 4 locations (8
  engines total)

Delta-V
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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, dry15 kg
• Power 5 W (valve and heater power accounted by
  other subsystems)
• Cost1000k

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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 (PPTs
  250k each)
• 87 kg Teflon
• Mass wet 153 kg, dry42 kg
• Maneuver power 300 W (valve and heater power
  accounted by other subsystems)
• Cost2000k

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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 (PPTs
  250k each)
• 8 kg Teflon
• Mass wet 64 kg, dry42 kg
• Maneuver power 10 W (valve and heater power
  accounted by other subsystems)
• Cost 2000k

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Detector, Free Flyer PPT
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Detector, Free Flyer Low Thrust Options, Typical
performance
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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

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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