THEMIS IIRT PRE-SHIP TELECON MPSR RFA #4 Mike Sholl University of California - Berkeley

1. THEMIS IIRT • PRE-SHIP TELECON • MPSR RFA #4 • Mike Sholl • University of California - Berkeley

2. MPSR RFA #4 TITLE:Thruster Qualification Data RFA CODE: MPSR #4 REQUESTED BY:Scott Glubke SPECIFIC REQUEST: Provide a summary of thruster operation (pulse and steady state) versus qualification testing for the primary modes of operation. Include a risk assessment for any regions or modes outside the qualified operating range for the thruster. RESPONSE: Subsequent to a similar recommendation that we stay within thruster qualification, we have chosen to lower the fuel load rather than add risk. The calculations have shown that a fuel load of 49.0 kg (0.5 kg less than originally planned) will keep pressures within qualification limits at all expected temperatures. Therefore, our current proposed propellant load is 48.8kg ±0.2kg.  Additionally, precision weights will be used during the fueling operation to ensure the accuracy of the loading operations fall within our ±0.2kg tolerance. Note: The Aerojet MR-111C thruster used on THEMIS heritage is listed in Michael Leeds’ Powerpoint presentation, provided.  Data contained in Leeds’s presentation was consolidated from Aerojet data.  For steady-state operation, the MR-111C is qualified up to 450psi (Mars ’98, Stardust).  For pulsed operation, it is qualified up to 400psi (Radarsat, Landsat 6).  For steady-state operation, the MR111C is qualified to pressures down to 75psi (ACE) and for pulsed operations down to 80psi (numerous missions).  During THEMIS ATP testing, all MR-111Cs used on the program were tested (steady state) down to 50psi.  This test consisted of a 100s burn, but was not a full qualification test.  In order to mitigate risk, 25 psi is added to this lower test limit as a minimum allowable feed pressure.  Feed pressure limits are 400psi (upper) and 75psi (lower).