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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

X-Ray Calorimeter Mission

Propulsion

Mark Underdown

2 – 6 April 2012

overview
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
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
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
v budget
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
v sensitivity
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
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
Blow-Down Curve

BOL

L2

MR-111C Operating Range

Launch Window

Orbit Maintenance

MCC

LV Dispersions

thrusters
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
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
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
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
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
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.