Spacecraft propulsion systems commonly use pressure-fed, 100-lbf class engines for the apogee insertion of geostationary satellites and for axial maneuvers of unmanned planetary spacecraft. Performance increases in these propulsion systems can be obtained by operation at higher chamber pressures. High-chamber-pressure operation, however, is not practical with pressure-fed systems, since the increases in propellant and in pressurant tank masses offset the engine performance gains. Pumped systems are required to derive a performance benefit from high-pressure operation. The use of pump technology has the potential to increase a satelliteís payload by 35 to 40 percent, but the feasibility of making a high-efficiency centrifugal pump small enough (0.5-in.-diameter impeller tip) for a 100-lbf class rocket engine has never been demonstrated.
Two-stage centrifugal pump installed in Glennís Research Combustion Laboratory.
Modern machine tool capabilities have made the design of such a pump possible. A two-stage pump with an overall pressure rise of 250 psia was designed and fabricated. The design includes crossover deswirl vanes between the stages and an exit volute. The mechanical layout of the pump is an overhung two-stage configuration with interstage seals and bearings exterior to the pump. Design criteria included compatibility with a hydrazine propellant. Supporting stress and dynamic analyses of the design were performed; then, the anticipated design performance was predicted with a steady, three-dimensional viscous flow calculation.
The two-stage centrifugal pump was tested in NASA Glenn Research Centerís Research Combustion Laboratory using water as a surrogate fluid for hydrazine. The pump ran at speeds up to 57,000 rpm and flow rates up to 1.2 gal/min. In general, pressure rises of about 75 percent of the predicted values were observed for the various flow rates and speeds. The pump delivered a pressure rise of 190 psi at 0.8 gal/min with an efficiency in the 45- to 50-percent range. Several branches from Glenn contributed to this effort. The Engine Systems Branch and Electric Propulsion Branch conducted thermodynamic and mission analyses of the pumped spacecraft systems. The Compressor Branch designed the hydraulics for the pump impellers and diffusion systems. The Mechanical and Rotating Systems Branch was responsible for the mechanical design and fabrication of the pump, and the Thermal and Fluid Systems Branch, the Avionics, Power, and Communications Branch, and the Mechanical and Rotating Systems Branch designed the pump stand and its data-acquisition system.
Pump performance map as a function of rotational speed.
Long description of figure 2.
This successful effort, started in fiscal year 2004, was funded by NASAís Energetics Legacy Program. It showed that the fabrication technologies exist to build high-efficiency pumps. These pumps have flow rates relevant to spacecraft propulsion and pressure increases that can significantly benefit mission payloads.
Find out more about Glennís research:
Compressor Branch: http://www.grc.nasa.gov/WWW/5810/
Power and In-Space Propulsion Division: http://www.grc.nasa.gov/WWW/5000/pep/
Mechanical and Rotating Systems Branch: http://www.grc.nasa.gov/WWW/7725/
Thermal and Fluid Systems Branch: http://www.grc.nasa.gov/WWW/7730/
Dr. Steven J. Schneider, 216-977-7484, Steven.J.Schneider@nasa.gov; and Joseph P. Veres, 216-433-2436, Joseph.P.Veres@nasa.gov
Authors: Dr. Steven J. Schneider, Joseph P. Veres, Brian D. Reed, Dr. Chunill Hah, Anthony L. Nerone, Cameron C. Cunningham, Thomas G. Kraft, Paul F. Tavernelli, and Bryan Fraser
Headquarters program office: Exploration Systems
Programs/Projects: Advanced Space Technology; Power, Propellants, and Chemical Systems; Energetics Legacy Program; Spacecraft Propulsion
Materials and Structures
Last updated: October 16, 2006
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