Engineering topics

Volz, S. M.

Publications and source records attributed to Volz, S. M..

3 records

NASA NTRS1992

Anomalous on-orbit behaviour of the NASA Cosmic Background Explorer (COBE) Dewar

A brief summary of the nominal cryogenic performance of the Dewar is presented, with emphasis on several aspects of the helium and spacecraft dynamical behavior. The occurrence of temperature and pressure oscillators in the Dewar porous plug is examined. The impact of the internal instrument malfunctions and of external radiation sources on the performance of the Dewar and of the instruments is reviewed. From measurements of the COBE spacecraft spin rate, the spin coupling of the liquid helium to the walls of the Dewar was monitored. The spin measurements are analyzed and a model for the coupling is presented. A number of 'lessons learned' from the COBE mission are reviewed, and the applicability of these lessons to future missions involving cryogenic payloads is addressed.

Volz, S. M.↗

NASA NTRS1991

Final cryogenic performance report for the NASA Cosmic Background Explorer (COBE)

The cryogenic operation of NASA's Cosmic Background Explorer (COBE) ended on September 21, 1990, with the depletion of the liquid helium cryogen. The COBE had successfully completed more than 10 months of dewar and instrument operation. We report on the cryogenic performance of the COBE dewar and of the two cryogenic instruments throughout the mission lifetime. We discuss the steady state dewar performance, and the dewar and instrument response to a variety of transient thermal phenomena, including external radiation (from the earth and the sun) and instrument power variation. We present the effectiveness of using approximate mass gauging techniques in determining the liquid helium content. Finally we discuss the dewar behavior during the depletion of the helium, and the expected thermal performance of the dewar cryogen tank and the cryogenic instruments as they approach final thermal equilibrium.

Volz, S. M.↗

NASA NTRS1991

SHOOT performance testing

The Superfluid Helium On-Orbit Transfer (SHOOT) Flight Demonstration is a shuttle attached payload designed to demonstrate the technology necessary to resupply liquid helium dewars in space. Many SHOOT components will also have use in other aerospace cryogenic systems. The first of two SHOOT dewar systems has been fabricated. The ground performance testing of this dewar is described. The performance tests include measurements of heat leak, impedances of the two vent lines, heat pulse mass gauging accuracy, and superfluid transfer parameters such as flow rate and efficiency. A laboratory dewar was substituted for the second flight dewar for the transfer tests. These tests enable a precise analytical model of the transfer process to be verified. SHOOT performance is thus quantified, except for components such as the liquid acquisition devices and a phase separator which cannot be verified in one gravity.

Dipirro, M. J.↗