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Dennis Asato June 28, 2001

XSuperNova / Acceleration Probe (SNAP). Propulsion. Dennis Asato June 28, 2001. SNAP Propulsion System. FUNTIONAL REQUIREMENTS Provide capability for multiple burn, 136 m/s D V Provide capability for 3-axis momentum unload KEY DESIGN DRIVERS Initial payload mass = 1619 kg

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Dennis Asato June 28, 2001

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  1. XSuperNova / Acceleration Probe (SNAP) Propulsion Dennis Asato June 28, 2001

  2. SNAP Propulsion System FUNTIONAL REQUIREMENTS • Provide capability for multiple burn, 136 m/s DV • Provide capability for 3-axis momentum unload KEY DESIGN DRIVERS • Initial payload mass = 1619 kg • ACS momentum unload = 3.5 kg/yr for 5 yrs • No S/C orientation constraints during orbit transfer thruster firings (e.g., instrument protected with covers) • Contamination sensitive instrument & sensors • S/C power constrained to “several hundred watts” SNAP, June 28, 2001Goddard Space Flight Center

  3. OPTIONS THRUST OPTION ISP (s) PROPELLANT MASS (kg) POWER (W) COMMENTS N2H4 22 N 220 117 9.1 W orbit ave.@ 25% d.c.+ 10.2 W/thruster during firing (+) Simple manifold design, low plume contamination, low HW mass (-) Low Isp (?) Fuel slosh issues during science (TBD) MMH/NTO 22 N 300 91 5 W/thruster during firing + TBD W orbit ave. (+) Higher Isp than N2H4 (+) Lower orbital ave. heater power than N2H4 system (-) Complex fuel/oxidizer manifold design (?) Fuel slosh issues during science (TBD) (?) Plume contamination issue (TBD) “Low Power” EP Options • Hall • PPT • Arcjet 123 – 250 mN 500-1765 13 – 44 (excl. ACS) 1800 - 2200 W (+) High Isp (-) High power (-) Thrust too low for orbit transfer; better suited for attitude control, SK, drag compensation (-) High Cost for low DV mission EP SYSTEM THRUST (mN) ISP (s) POWER (kW) Xe Hall 123 1765 2.2 N2H4 Arcjet 250 500 1.8 SNAP Propulsion SystemDesign Trade “Low Power” EP Assumptions SNAP, June 28, 2001Goddard Space Flight Center

  4. SNAP Propulsion SystemDesign Trade Conclusions • Baseline Design: “Blowdown” (unregulated pressure) N2H4 System with 4x22N canted thrusters & three • 48.3 cm dia. propellant tanks • Merits: Simple manifold design, low contamination, relatively low component mass & orbital ave. power • Negatives: Low Isp (large tanks) • Propulsion System Options to Reduce Volume • MMH/NTO, pressure-regulated bipropellant system option would reduce the propellant tank diameter to 35 cm (4 tanks) + a 20 cm dia. pressurant tank. • Orbit transfer with single high DV burn would allow use of solid motor + small N2H4 system (ACS unload & small DV orbit adjust) • 2 kW power system would be required to use EP thrusters (N2H4 arcjet, Xe Hall) – low thrust; long orbit transfer time. SNAP, June 28, 2001Goddard Space Flight Center

  5. F/D Valve N2H4 Tanks w/ AFE-332 or PMD Pressure Transducer Filter LV Latching Isolation Valve Primary & Redundant 22 N Thrusters with Dual Seat Valves P LV SNAP Propulsion System • N2H4 Propulsion System Design • N2H4 mass (10% contingency) = 130 kg • “Dry” mass (4 Tank Design) = 34.1 kg • Three 48.3 cm dia tanks with AFE-332 • elastomer diaphragm • Primary & Redundant set of 22N • thrusters mounted on –X axis & canted • 15o off X-axis • Orbit Ave Power (@25% D.C.) = 23 W • Catalyst Bed + Thruster Power (During Firing) • = 10.2 W per thruster Z Z 15o X Y SNAP N2H4 PROPULSION SYSTEM SNAP, June 28, 2001Goddard Space Flight Center

  6. SNAP Propulsion System SNAP, June 28, 2001Goddard Space Flight Center

  7. GN2 Tanks P Pyro Isolation Valves F Filter 2-Stage Regulator Redundant Check Valves P P MMH or N2H4 N2O4 NC NC F F Latching Isolation Valves LV LV NC NC NC NC NC NC NC NC 8 x 22 N Thrusters (Primary & Redundant) SNAP Propulsion System Regulated BiPropellant System Option SNAP, June 28, 2001Goddard Space Flight Center

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