THREE-DIMENSIONAL TRANSIENT THERMAL ANALYSIS OF A RECEIVER-ABSORBER-CONVERTER SYSTEM IN THE INTEGRATED SOLAR UPPER STAGE UNIT

Abstract

The Integrated Solar Upper Stage (ISUS) program is directing its efforts at solving endemic national spacecraft architecture problems. The ISUS is an advanced, integrated upper stage concept that would permit payload realignment, allowing large payloads to be moved by smaller and less expensive boosters. A receiver-absorber-converter (RAC) system in the ISUS unit is designed to convert solar energy to kinetic energy in the propulsion phase or electrical energy in the power generation phase for spacecraft control and operation. In this study a three-dimensional, transient, turbulent hydrogen gas flow through the RAC system was simulated using a finite element thermal-hydraulic model. With this model, transient temperature, pressure, and flow fields in the RAC system were obtained. Numerical results of the mass flow rate distribution through hydrogen heating channels reveal that higher mass flow rates occur through those channels near either the hydrogen channels reveal that higher mass flow rates occur through those channels near either the hydrogen inlet or exit. It takes about 18.5 min for the hydrogen exhaust temperature to drop below 2000 K. The results obtained from this work have been applied for validating and optimizing the present RAC design, as well as for performing the thermal stress analysis.