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A synopsis of the On-Orbit Compressor Technology Program is presented. The objective is the exploration of compressor technology applicable for use by the Space Station Fluid Management System, Space Station Propulsion System, and related on-orbit fluid transfer systems. The approach is to extend the current state-of-the-art in natural gas compressor technology to the unique requirements of high-pressure, low-flow, small, light, and low-power devices for on-orbit applications. This technology is adapted to seven on-orbit conceptual designs and one prototype is developed and tested.

The focus is the generation of technology and fabrication of prototype hardware applicable to seven Space Station compressor system applications. The compressors are of the single acting reciprocating piston type and, in general, may be termed miniature in size compared with normal commercially available equipment. The initial technology development is focused on improved valve designs, and the control of pulsations and heating effects in order to increase compressor efficiency and reduce cycle temperatures, thus permitting significantly increased stage pressure ratios. The initial test compressor was successfully operated at pressure ratios of up to 50:1, and this significant extension of allowable pressure ratio will result in a reduction of the number of required stages and, hence, total hardware thereby reducing system weight and volume. These experiments have also identified the need to employ low shaft speeds, on the order of 250 to 500 rpm, to enhance heat transfer and increase life. The prototype compressor currently being designed, is to be driven by a low-speed brushless dc motor sealed in a case common to the compressor drive mechanism case. The compressor and motor case will communicate with stage suction pressure so that any minor gas leakage past the piston rings will be returned to the suction. Emphasis in this prototype design is being placed on simplicity, durability, commonality of components, and high efficiency.

The bellows flow excitation mechanism and results of comprehensive test program are summarized. The analytical model for predicting bellows flow induced stress is refined. The model includes the effects of an upstream elbow, arbitrary geometry, and multiple piles. A refined computer code for predicting flow induced stress is described which allows life prediction if a material S-N diagram is available.

Results of theoretical and experimental investigations of bellows typical of those found in space shuttle external tanks are presented. Correlation parameters are identified which generalize the alternating stress calculations cited in an earlier study. Alternating stress amplitudes and mean stress levels form the basis of a fatigue analysis incorporating seven ordinate charts for 347 stainless steel, alloy 21 6-9, and Inco 718. A crack propagation model is included with a program for computing bellows fatigue life. Two phase flow and material hardness properties are discussed.

Vibratory amplitudes and stress levels from metal bellows flow induced vibrations, discussing damping and acoustical resonances effects

Instrumentation and development techniques for low velocity gas flow measurement

Experimental research describes fluid flow and the fluid-elastic mechanism causing bellows flow excitation, and aids in design of conventional bellows liner which suppresses flow-induced vibrations. Analytical models facilitate prediction of flow excitation occurrence and estimation of severity of bellows vibrations.

Flow-induced vibration of bellows with internal cryogenic fluid flows

Study of ducting and duct components to minimize pressure loss in space vehicle high velocity feed system

Longitudinal vibrations induced by internal flow in metal bellows resembling vortex shedding excitations of elastically restrained cylinders, discussing spring mass mechanical model

Dynamic models for viscous fluid transmission lines using distributed parameter for accuracy and rational approximate form to avoid computational difficulty

Surface disintegration of contained liquid excited longitudinally at HF

Linear symmetric modes of propagation for viscous compressible liquid in rigid and elastic conduits analyzed using Navier-Stokes equations

Bellows configurations design, pressure loss, and vibration tests to minimize pressure drop and improve gas and liquid flow in spacecraft high velocity duct systems

Linear symmetric modes of propagation for viscous compressible liquid in rigid and elastic conduits analyzed using Navier-Stokes equations

Surface instability and disintegration of liquid in longitudinally excited container

Navier-Stokes equation for dynamics of viscous fluid transmission lines in closed conduits

Atmospheric density effect on computation of earth satellite orbits

Effects of two-phase fluids on flow characteristics in fluid conduits

Fluid transients in closed conduits

An analytical model and corresponding computer program for studying disturbances of liquid propellants in typical engine feedline systems were developed. The model includes the effects of steady turbulent mean flow, the influence of distributed compliances, the effects of local compliances, and various factors causing structural-hydraulic coupling. The computer program was set up such that the amplitude and phase of the terminal pressure/input excitation is calculated over any desired frequency range for an arbitrary assembly of various feedline components. A user's manual is included.

Gas velocity measuring instrument measures transport time of ion-trace traveling fixed distance between ionization probe and detector probe. Electric field superimposes drift velocity onto flow velocity so travel times can be reduced to minimize ion diffusion effects.

An analytical model and computer program were developed for studying the disturbances of liquid propellants in engine feedline systems. It was found that the predominant effect of turbulence is to increase the spatial attenuation at low frequencies; at high frequencies the laminar and turbulent frequencies coincide. Recommendations for future work are included.