1. Section 17.0 Propulsion Subsystem Michael S. Rhee Propulsion Lead 5 Space Technology “Tomorrow’s Technology Today” GSFC ST5 PDR June 19-20, 2001

2. GSFC 17 - 2 Agenda Requirements Documentation Subsystem Design Electrical Interface Block Diagram Delta-V Budget Mass and Power Budget Test and Analysis Future Test and Analysis Plan Propulsion Hardware Components

3. ST5 PDR June 19-20, 2001 GSFC 17 - 3 Key Level II Requirements The propulsion subsystem shall include a cold gas micro-thruster system. (MRD10302010) –The ST5 propulsion subsystem is a GN 2 cold gas system based on the Marotta cold gas micro-thruster. Estimates of supply pressure shall be provided by direct pressure telemetry and/or a combination of indirect temperature telemetry and thruster on-time tracking. (MRD10302030) –The ST5 propulsion subsystem includes a miniature pressure transducer by GP:50 to allow direct pressure telemetry. –Tank pressure can be calculated from tank temperature and thruster on-time data. The thruster shall provide telemetry indicating the previous actuation activity of the thruster valve. (MRD10101040) –The thruster control electronics (TCE) includes an indicator to monitor current pulses going to the solenoids.

4. ST5 PDR June 19-20, 2001 GSFC 17 - 4 Key Level II Requirements The thruster shall operate in continuous mode, or pulsed mode. (MRD10302011) –The cold gas micro-thruster is capable of operating from 0.05 sec. minimum pulse width to continuous firing. The propulsion subsystem shall provide a maximum delta-V of 7.6 m/s. (MRD10302020) –The 15cm (6” OD) tank pressurized to 13.8 Mpa (2000 psia) at BOL gives the system delta-V capability of 7.6 m/s. The thruster control circuitry shall have sufficient protections to preclude inadvertent thruster firings due to either hardware or software malfuctions. (MRD10302040) –The TCE incorporates multiple safety features to prevent accidental thruster actuation that can lead to loss of propellant.

5. ST5 PDR June 19-20, 2001 GSFC 17 - 5 Key Level II Requirements The propulsion system shall be designed such that the pre- welded propulsion system can be installed as one complete and tested assembly to the spacecraft. (MRD10302050) –Small size and simplified layout of the ST5 propulsion subsystem allows “assembly line” integration approach. –Each propulsion subsystem is integrated on a duplicate bottom deck plate, which serves as an assembly jig. –Each completed assembly is leak checked and tested for mechanical and electrical functions. –Each completed assembly is integrated on to the spacecraft structure. –The subsystem undergoes environmental test at the spacecraft level.

6. ST5 PDR June 19-20, 2001 GSFC 17 - 6 Key Level III Requirements Operational pressure range: 2000 psia BOL to 100 psia EOL –Thrust range: 2.1 N (2000 psia) to 0.1 N (100 psia) GN 2 Propellant tank size –1730 cc (106 ci) useable internal volume –15 cm (6 “ ) maximum outer diameter Total propellant load: 0.27 kg of GN 2 at 20 degrees C Minimum vacuum specific impulse: 60 seconds Minimum pulse width: 50 ms

7. ST5 PDR June 19-20, 2001 GSFC 17 - 7 Key Level III Requirements ~1/3 Hz actuation frequency mode –For attitude control (spin axis precession) at 20 rpm –50 ms to 2.95 s pulse widths in 50 ms increments 2 Hz actuation frequency mode –For orbit adjustment at 20 rpm –50 ms to 450 ms pulse widths in 50 ms increments Capable of continuous firing Temperature range –-20 to 40 degrees C operating –-40 to 55 degrees C survival 1x10 -4 scc/s He Maximum allowable system leakage rate

8. ST5 PDR June 19-20, 2001 GSFC 17 - 8 Documentation Status Propulsion Subsystem Specification ST5-495-019 –Preliminary Propulsion Subsystem Interface Control Document ST5-495-015 –Preliminary Cold Gas Micro Thruster SOW ST5-495-001 –Under Project Configuration Management Cold Gas Micro Thruster Specification ST5-495-002 –Under Project Configuration Management Other propulsion components SOWs and SPECs are in draft –Propellant tank –Pressure transducer –Propellant filter –Fill and drain valve

9. ST5 PDR June 19-20, 2001 GSFC 17 - 9 ST5 Propulsion Subsystem Design

10. ST5 PDR June 19-20, 2001 GSFC 17 - 10 ST5 Propulsion Subsystem Design

11. ST5 PDR June 19-20, 2001 GSFC 17 - 11 Electrical Interface Block Diagram + 5VDC + 7.2VDC GND Temperature Pressure Feedback Command Pressure Transducer Thruster Control Electronics (TCE) Cold gas micro thruster Tank Thermistor TCE Thermistor Thruster Thermistor Analog Single ended digital Single ended digital C&DH

12. ST5 PDR June 19-20, 2001 GSFC 17 - 12 Propulsion Delta-V Budget

13. ST5 PDR June 19-20, 2001 GSFC 17 - 13 Propulsion Mass Budget Mass budget

14. ST5 PDR June 19-20, 2001 GSFC 17 - 14 Propulsion Power Budget Power budget

15. ST5 PDR June 19-20, 2001 GSFC 17 - 15 Propulsion Test and Analysis Analytical model of the cold gas propulsion system –Predicts impulse delivered as a function of thruster on-time –Adiabatic Case: Tank is insulated, dQ/dt = 0 –Isothermal Case: Tank temperature = constant = 20 degrees C The actual behavior will fall between these two bounding cases The model will be calibrated to match the thrust stand test of the cold gas micro thruster

16. ST5 PDR June 19-20, 2001 GSFC 17 - 16 Propulsion Test and Analysis Thrust stand testing of the prototype cold gas micro thruster –In-House designed and built thrust stand to measure thrust range from 1 to 0.001 N –Initial testing done in ambient condition; future testing will be done in vacuum.

17. ST5 PDR June 19-20, 2001 GSFC 17 - 17 Future Test and Analysis Plan In-House thrust stand testing of the cold gas micro thruster as a part of the qualification program Refined analytical model of the propulsion system based on thrust stand test results Create analytical model for predicting propellant usage based on thruster on time data and tank temperature Structural analyses (Swales) Thermal analyses (Code 545 or Swales)

18. ST5 PDR June 19-20, 2001 GSFC 17 - 18 Propulsion Hardware Cold gas micro thruster (NMP Technology) –Developer: Marotta Scientific Controls, Montville, NJ –Low power (1 watt), light weight (50 g) design –Prototype hardware delivered to GSFC in July ’99 –In-House thrust stand testing of the prototype thruster in Dec. ’00 –Contract awarded to Marotta in Sep. ’99 for full development program –Currently in Phase B/Design stage; Phase C to begin in June ‘01 –Qual unit: proto-flight test levels –Flight units: acceptance test levels

19. ST5 PDR June 19-20, 2001 GSFC 17 - 19 Propulsion Hardware Thruster Control Electronics (NMP Technology) –Developer: Marotta Scientific Controls, Montville, NJ –Prototype TCE delivered to GSFC in July, ’99 –Contract awarded to Marotta in Sep. ’99 for full development program –Currently in Phase B/Design stage; Phase C to begin in June ’01 –Incorporates multiple safety features for increased reliability Telemetry Feedback Signal Thruster ON Limit Timer Thruser ON Limit Timer Disable Disable Valve Open Command when Capacitor Charge is too low Automatic Valve Close on Power Loss –Qual unit: proto-flight test levels (To be performed In-House) –Flight units: acceptance test levels (To be performed In-House)

20. ST5 PDR June 19-20, 2001 GSFC 17 - 20 Propulsion Hardware Baseline Pressure Transducer –Vendor: GP:50 –7.2 VDC, Low power (200 mW), lightweight (60 g) design –Analog electronics previously flown in STS –ST5 version will undergo full qualification program based on ST5-495-007, “Component Test Requirements and Guidelines” –Current status: SOW and Spec completed. Ready to start procurement. Miniature Fill and Drain Valve and Propellant Filter –Vendor: Vacco –Fully qualified, COTS –Deliverables: Three flight units with acceptance data packages –Current Status: SOW and Spec completed. Ready to start procurement.

21. ST5 PDR June 19-20, 2001 GSFC 17 - 21 Propulsion Hardware Propellant Tank –Vendor: Carlton Technologies Inc. –Lightweight composite vessel: carbon fiber with aluminum liner –Proof factor of 1.5x MEOP; Burst factor of 2.0x MEOP –Full qualification program based on MIL-STD-1522A and ST5-495-007 “Component test requirements and guidelines” One qual unit for cycle test (min. 50 cycles) and burst Three flight units (leak and proof) Environmental testing at the spacecraft level –Current Status: SOW and Spec completed. Ready to start procurement.

22. ST5 PDR June 19-20, 2001 GSFC 17 - 22 Risk Mitigation – Delta-V Budget Risks to Available Performance –Increase in S/C Mass Current propulsion system delta-V capacity based on 20.96 kg spacecraft mass Any increase in spacecraft mass will reduce the system delta-V capacity –Thruster Isp is lower than 60 sec. Current Predictions for Isp Analytically Based Ambient Measurements of Performance Lower Than Expected Currently Updating Model and Planning In-Vacuum Testing Mitigation –Alter Constellation Design Eliminate Apogee Raise Maneuver Sequence No Impact to Mission Success or Resources –Change Propellant Use of Heavier Fuel, at Lower Isp Can Yield Significant Increase in Delta-V at Same Volume and Pressure Impact: Increase in Spacecraft Mass –Increase Tank Volume Increase in Available Propellant for Same Pressure Impact: Increase in Both Spacecraft Volume and Mass