Surge Pressure Mitigation in the Global Precipitation Measurement Mission Core Propulsion System

Abstract

The Global Precipitation Measurement (GPM) mission is an international partnership between NASA and JAXA whose Core spacecraft performs cutting-edge measurements of rainfall and snowfall worldwide and unifies data gathered by a network of precipitation measurement satellites. The Core spacecraft's propulsion system is a blowdown monopropellant system with an initial hydrazine load of 545 kg in a single composite overwrapped propellant tank. At launch, the propulsion system contained propellant in the tank and manifold tubes upstream of the latch valves, with low-pressure helium gas in the manifold tubes downstream of the latch valves. The system had a relatively high beginningof-life pressure and long downstream manifold lines; these factors created conditions that were conducive to high surge pressures. This paper discusses the GPM project's approach to surge mitigation in the propulsion system design. The paper describes the surge testing program and results, with discussions of specific difficulties encountered. Based on the results of surge testing and pressure drop analyses, a unique configuration of cavitating venturis was chosen to mitigate surge while minimizing pressure losses during thruster maneuvers. This paper concludes with a discussion of overall lessons learned with surge pressure testing for NASA Goddard spacecraft programs.

Cavitating Venturi Model Using Standard Element and Options in Commercially Available Lumped-Parameter Software

“…Selecting the appropriate venturi configuration for the vehicle propellant system often requires multiple experimental iterations 1,2 in which venturis of different throat diameters are installed in the propellant system and both steady and transient flow tests are conducted. This experimental process is effective but can also be timeconsuming, requiring at least one engineer and one technician full-time for several months for the sizing process, followed by an additional few months' time to characterize the flight venturis.…”