Search Results

New Space Support Equipment (SSE) components developed for the Hubble Space Telescope Second Servicing Mission are described, with particular emphasis on how flight experience from the 1993 First Servicing Mission was utilized in the design and testing process. The new components include the Second Axial Carrier (SAC) Axial Scientific Instrument Protective Enclosure (ASIPE), the magnetic-damped SAC ASIPE Load Isolation System, the Enhanced Power Distribution and Switching Unit (EPDSU), and the Multi-Mission Orbital Replacement Unit Protective Enclosure (MOPE). Analytical modeling predictions are compared with on-orbit data from the Hubble Space Telescope (HST) Second Servicing Mission. Those involved in thermal designs of hardware for use on the Shuttle or Space Station, particularly with astronaut interaction, may find interest in this paper.

The thermal design strategy is discussed as it relates to the production of up to 34 identical small satellites in a relatively short period of time. Tight production and launch schedules and the need to design for low mass, risk, and cost presented a design challenge for all disciplines. A specific arrangement of passive thermal control features, including ITO-coated AgTef covered structure radiators, MLI, and software controlled heaters established a robust design. Thermal modeling of the bus and unique antenna are presented including a comparison between the predicted and required component temperature ranges. Also described are the primary mission objective, the spacecraft configuration, requirements and design drivers, mission environments, and design parameters.

In August, 1995, the TOPEX/Poseidon satellite completed its third year in orbit and met its operational life requirement. The satellite TCS is performing as expected with the telemetry indicating that all components are operating within their allowable temperature ranges during normal mission modes. This paper assesses the performance of TCS from the start of the mission through 3 years in orbit at 1335 km altitude and 66.25° inclination. This orbit is in the Van Allen Belt in which few spacecraft fly. Specific attention is paid to environmental, operational, and attitude control conditions and their effects on the satellite thermal performance. The thermal telemetry data of each satellite module is discussed with respect to thermo-optical property degradation and the effects of varying orbital sun angles.

A wide range of environmental exposures, stringent payload interface conditions, a low risk requirement, low allowable heater power, constraints of a fixed price contract and aggressive schedule presented a challenge in developing the FUSE bus (spacecraft) thermal design. The bus provides power, attitude control and telemetry for the satellite, which includes the bus and instrument payload. The thermal design that evolved is remarkably self-regulating. This is attributed to the synergistic effect of a compact structure that allows cross-coupling of radiators with different exposures in addition to the advantages of a large louver. This paper discusses the design approach, key thermal control features, supporting analyses and trade studies, and how predicted results compare with requirements for the design envelope and beyond.

The use of the SINDA/FLUINT computer code (Reference 1) for solving convective cooling problems has proven to be a valuable design and analysis tool. SINDA/FLUINT is used to efficiently support design applications where thermal analysis involving both heat transfer and fluid flow are involved. The program allows for simplification of fluid modeling compared to older versions of SINDA where this could only be done through user-generated logic. Also, SINDA/FLUINT provides a faster and simpler analysis basis over more complex fluid dynamics software programs, which can be an advantage for certain design applications. This paper discusses the utilization and benefits of SINDA/FLUINT for examples of such designs.

Thermal design and verification testing of the ASIPE, one element of the re-usable Space Support Equipment (SSE), are discussed with respect to how unique and competing requirements are satisfied for Scientific Instrument (SI) conditioning, safety, and on-orbit servicing operations. A system approach, rather than optimizing any one performance characteristic, results in a robust design. The special thermal testing required to verify the unique enclosure is described. Analytical modeling predictions are compared with on-orbit telemetry from the Hubble Space Telescope (HST) First Servicing Mission (FSM). Emphasis is on why the design works well, rather than the specific hardware selected. Those involved in thermal designs of hardware with astronaut interaction may find interest in this paper.

The importance of developing test correlated analytical models, of critical or unique spacecraft hardware, is not limited to pre-flight design verification. Such thermal models can also be extremely useful tools in assessing on-orbit operational and temperature anomalies. This paper discusses the application of test correlated thermal models, developed for a complex electro-mechanical system, in support of on-orbit operational replanning in response to unexpected mechanism movement and electronics temperature levels. The modeling effort utilized a recently developed routine for chaining coordinate systems in TRASYS (Thermal Radiation Analysis System). Results from the modeling provided detailed data, which complemented the limited telemetry and supported the operational replanning to ensure acceptable performance would be maintained throughout the mission.

In order to characterize the thermal performance of the spacecraft at attitudes beyond initial constraints and to expand the operational envelope, on-orbit testing was performed. Plans and tradeoffs in preparing for the testing are discussed. Results are presented and compared with analytical predictions. Although the payload and bus sections were only separately thermal vacuum tested prior to flight, results from the on-orbit testing indicate the integrated thermal design is robust. One thermal anomaly was discovered which is attributed to specular reflections from a radiator. The influence of the on-orbit testing results on spacecraft continuing operations is also discussed.