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X-Ray Calorimeter Mission. Propulsion Mark Underdown 2 – 6 April 2012. Overview. Monopropellant (Hydrazine) Propulsion subsystem operating in a Blow-down mode Two 22 inch spherical propellant tanks with diaphragms Thrusters: Twelve 4N thrusters ( Aerojet MR-111C)
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X-Ray Calorimeter Mission Propulsion Mark Underdown 2 – 6 April 2012
Overview • Monopropellant (Hydrazine) Propulsion subsystem operating in a Blow-down mode • Two 22 inch spherical propellant tanks with diaphragms • Thrusters: Twelve 4N thrusters (Aerojet MR-111C) • Propellant Mass: 86.2 kg • Subsystem Dry Mass: 26.3 kg • Subsystem is single-fault tolerant (dual-fault tolerant wrt Range Safety) • All components are TRL9
Propulsion Subsystem Description • Mono-Propellant, blow-down system using hydrazine fuel • Two diaphragm propellant tanks • Diameter ~22 inch • Each hold ~48 kg of fuel (total required = 86.2 kg) • Twelve 4-N thrusters • Thrusters arranged in 2 banks to provide redundancy • Thrusters provide 6 DOF • Dual coil thrusters • Dual coil latch valves • Pressurant side of tanks isolated to ensure equal draining • Dedicated transducers provide propellant knowledge for individual tanks P P N2 N2H4 N2 N2H4 Diaphragm Tanks F 4 N Thrusters FD Valve Latch Valve Pressure Transducer Filter F P
Propulsion Subsystem Drivers • Provide ΔV for 2530 kg maximum launch mass (wet mass) • Provide 6 DOF to spacecraft via thrusters • Unload momentum wheels • Size the propulsion system for 5 years at L2 at maximum launch mass • Single fault tolerant • Dual fault tolerant with respect to catastrophic hazard- AFSPCMAN 91-710 • Minimize plume contamination to mirror and radiators • Minimize product qualification testing
ΔV Budget • Propellant was budgeted for a 2530 kg S/C (including propellant mass) • Nominal ΔV = 66 m/s. Adding 10% AC tax and 0% Margin • LV Dispersions not well supported. May increase by 25 m/sec (current tank set can accommodate, see ΔV Sensitivity chart for tank capacity margins) • Specific Impulse (Isp) assumes 10⁰ degree cant in two planes. (219.4 s represents average over full pressure range) • Total propellant mass = 86.2 kg • Maximum continuous burn = 6232 seconds (~104 minutes), Launch Window+Dispersion
ΔV Sensitivity • Propellant was budgeted for a 2530 kg S/C (including propellant mass) • Nominal ΔV = 72.6 m/s, Isp = 219.4 sec (10⁰+ 10⁰ cant) , Propellant mass = 86.2 kg • Max load = 127.6 kg (2 x 5555 in^3 tanks, 400 – 100 psi blowdown, 50 – 10 C)
Propellant Tanks • 2 spherical diaphragm tanks with tab mounts • ATK Part No. 80259-01 • Volume = 5,555 in3 (one tank) • Propellant Capacity • 72 kg each (qualified max), • 64 kg for 400 – 100 psi blowdown, 50 – 10 ⁰C • Titanium Construction • Mass = 7.27 kg each • Diameter = 22.14 in. • MEOP = 475 psi • BOL 400 psi @ 50C for this mission • Tank will blow down to ~ 181 psi at 10 ⁰C
Blow-Down Curve BOL L2 MR-111C Operating Range Launch Window Orbit Maintenance MCC LV Dispersions
Thrusters • Twelve Aerojet MR-111C monopropellant thrusters • 4 N (1 lbf), • Extensive flight heritage • Sizing: • ΔV • Four 4N thrusters complete largest maneuver (Launch window+ELV Dispersion Correction - 33 m/s) in about 104 minutes • Thruster qualified for hundreds of minutes continuous firing • ΔH • Unloads expected to be infrequent (~ 75 days) • Minimum impulse bit @ 400 psi~ 0.08 Ns x moment arm • Estimated propellant required for ΔH is 0.5 kg • Assume unloading 122.5 Nms every 75 days for 5 years • Pulse Life • Maximum number of pulses ~ 12000 for ΔH • Thruster qualified for >> 100,000 pulses
Notional Thruster Locations Provide 6 DOF and redundancy in the event of thruster failure 8 Thrusters canted 10⁰ in two planes Couple 4 Thrusters canted 45⁰ in one plane Solar Array Notional CG Lines of Action
Master Equipment List • All components are TRL-9 • Power • Thruster Cat-Bed Heaters = 3.85 Watts each. Minimum of 4 heaters powered for one hour before maneuvers • Pressure Transducers = 1 Watt each. 2 Pressure Transducers powered continuously • Valve, line and tank heaters booked by Thermal
Issues and Concerns • Plume Impingement • Current configuration eliminates most plume concerns • Other configurations especially modular may require analyses • Investigate current BL thruster configuration for adequacy • Torque margin • Redundant modes • Latch valve grouping • Cant angles • Reported propellant budget based on max launch weight • Conservative • Includes launch adapter • Calculate on margined dry mass also • Smaller tanks (~2 kg savings) • Investigate other configurations • Packaging/integration advantages (struts, mount to cone, mount to/through solar array • Match to torque requirements (with margin)
Acronyms BL – Baseline BOL – Beginning of Life DOF – Degree of Freedom FD Valve – Fill and Drain Valve MCC – Mid-Course Correction MEOP – Maximum Expected Operating Pressure MR – Monopropellant Reaction (Engine)
Propulsion Labor • Total FTEs = 12.9 • Cost assumes In-House build at GSFC and covers the following tasks: • Propulsion subsystem design and analysis • Procurement activities (component purchases and contract management) • Propulsion subsystem assembly • Propulsion subsystem testing • Propulsion support during S/C level I&T • Launch site support • Note: FTEs do not include thermal design, drawing production, support structure fabrication, or electrical harness integration.
