D URING the last 20 years, in-flight refueling of military aircraft has become routine. The extension of this operational technique to earth-orbital spacecraft will become mandatory as mission durations are extended up to one year and beyond. This paper reviews the more feasible and promising concepts for propellant transfer in orbit and discusses their compatibility with typical refueling requirements.Several analyses are presented which relate to determining vapor-liquid-interface stability, pressurant requirements, transfer-line chilldown, receiver-tank thermodynamics, propellant-transfer dynamics and associated nonsteady flow problems, and dielectrophoresis. A simplified concept for estimating suction specific speeds of low-NPSH (net positive suction head) pumps is given. Finally, two figures of merit are suggested for use in system tradeoffs, one for the transfer system only and one for the over-all tanker vehicle.
Propellant Transfer System ConceptsTank replacement is an obvious method for transferring small to moderately large quantities of propellants. Quickdisconnect couplings would be utilized to minimize required extra-vehicular activity (EVA) on the part of the astronauts. This concept appears to be attractive for resupply of life support fluids and for transferring small quantities of propellants.The use of bladders ( Fig. 1) or pistons for expulsion has definite advantages in a zero-gf environment. 45 The problems of ullage control and liquid/vapor separation are eliminated, and the propellant outage is limited only by imperfections in the bladder design or its operation. No artificial gravity need be created to prevent vapor ingestion, as in the case of pump transfer systems. An ideal bladder structure
John E. Boretz is a Senior Staff Engineer reporting to the Manager of the Electrical Systems Laboratory in TRW Systems' Space Vehicle Division. He also is Program Manager for the NASA Manned Space Flight Center Lunar Surface Power System Program, a technology development project related to a 300-v, 45-kw, 5-yr-life, solar array system. He has had technical responsibility for several space system proposals and study programs, including the extended LEM solar array, high-voltage solar arrays, Skylab I Solar Array, and a large, body-mounted solar array system for a low-Earth-orbital satellite (HEAOS). From 1962 through 1964, he was Manager of Saturn S-II Stage Systems Integration at North American Rockwell and was responsible for Saturn V/Apollo mission operations systems analysis and integration. Earlier, atMartin-Marietta, Denver Division, he was responsible for the development of the propulsion systems for the Titan I and II ICBM's and ultra-low-pressure rocket systems. His experience includes nuclear engineering (AMF), environmental control systems (Fairchild-Hiller), jet engines (Curtiss-Wright), rocket engines (M. W. Kellogg), and structural analysis (Navy Department). J. E. Boretz received a B.S.M.E. from Cooper Union School of Engineering (1948), an M.S.M.E. in applied mechanics and thermodynami...