# Presentation: 276664

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

**Robert Estes**
**Scott Glubke**

**Propulsion**

**May 13-17, 2002**

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

## 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)

## “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

- 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) **

**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

## 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

- 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 **

## 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

- 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 **

## 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)

- 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 **

## 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

- 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 **

## Transfer Stage Propulsion Design

**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

## 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

## 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

## 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

## Detector, Free Flyer: PPT

## Detector, Free Flyer: Low Thrust Options, Typical performance

## 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

## 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