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Thermal Vacuum

Scope and Description

This topic covers thermal vacuum (TVAC) testing of a spacecraft and/or its subsystems. TVAC testing is the most realistic thermal simulation of the flight environment. For this reason, this testing is critical to ensuring mission success and can not be replaced by ambient pressure thermal testing. During a TVAC test, hardware is subjected to a number of hot-cold cycles in a vacuum environment and system performance is verified through functional tests which are carried out at temperature plateaus.

Resources under this topic include standard testing thresholds/requirements, guidance for developing and operating a TVAC chamber, and example test reports.

Best Practices and Lessons Learned

  • Only conducting thermal testing at ambient pressure often yields significantly unrealistic results. Always conduct at least one hot-cold TVAC cycle at the spacecraft-level and with comprehensive functional testing.
  • Always bond thermistors to the hardware under test using a robust, thermally conductive bonding compound. Test are often delayed or invalidated due to improperly attached test instrumentation which becomes detached.
  • Thermistor wires can create thermal bridges between components. Take special care when routing and affixing test instrumentation to avoid influencing results.
  • Ensure that all bolts are torqued per their flight specification. This is to ensure that the thermal gradients across bolted interfaces are as flight-like as possible.

Resources

This conference paper describes thermal modeling of a smallsat and correlation to thermal vacuum (TVAC) ... test data. While dated, it is a useful case study for smallsat developers. It includes a complete description of the inputs and methods for modeling, analysis, and correlation to test data.

Book
George Sebestyen et al.

This book chapter, titled "Thermal Design" covers thermal design, analysis, and testing for LEO satellites. ... This includes background on the physics of heat transfer, thermal control hardware, and processes for thermal design, analysis, and testing. Note that this chapter is only 13 pages, and does not go into significant detail on any of the included topics.

White Paper
NASA

This page in the NASA Public Lessons Learned System recommends that thermal vacuum tests follow dynamics ... tests (e.g. vibration testing). It provides detailed guidance and motivation for this recommendation.

Book
David Gilmore

This chapter titled "Thermal Testing" is a comprehensive reference regarding thermal testing of space ... flight hardware. The tests covered are thermal cycling (ambient pressure), thermal vacuum, thermal balance, and burn-in. It includes a description of the elements and stages of the traditional approach, environments, margins, requirements, and required equipment/facilitates.

White Paper
US Department of Defense

This handbook provides in-depth guidance on testing of space vehicles. The testing covered includes structural ... loading, thermal vacuum, thermal cycling, thermal balance, pressure testing, burn-in, random vibration, acoustic, and pyroshock - among others. This is a dated but comprehensive source of space hardware test environments and processes.

White Paper
Aerospace Corporation

Cost and schedule pressures that becoming more often a part of smallsat development has led many developers ... to debate the costs and benefits of thermal vacuum testing. This resource takes a deeper dive into this question to determine just how valuable thermal vacuum testing is.

This article is a reflection on the acceptance testing performed for a 120kg small satellite. It covers ... EMC testing, vibration testing, and thermal/vacuum testing. This case study is a good resource to review before performing your own testing.

Article
Roy Chisabas et al.

Thermal-vacuum cycling tests are necessary for evaluating the survivability of a satellite in the harsh ... thermal environment of space. The objective of this resource is to deliver and establish a set of "comprehensive and coherent thermal-vacuum specifications." Detailed specification and process is provided throughout.

Article
Roy Chisabas et al.

Thermal-vacuum testing is critical to ensuring satellite reliability and survivability. Unfortunately, ... many thermal-vacuum chambers are much larger than necessary for small satellites, resulting in an unnecessary cost burden for developers. This paper seeks to outline the methodology for developing thermal-vacuum chambers for testing small satellites.

White Paper
NASA

These slides are a summary of NASA's Marshall Space Flight Center's (MSFC's) thermal vacuum testing philosophy. ... The slides cover general concepts followed by an example of how a box would be tested at MSFC.

White Paper
Aerospace Corporation

"This Standard establishes the environmental and structural ground testing requirements for launch vehicles, ... upper-stage vehicles, space vehicles, and their subsystems and units. In addition, a uniform set of definitions of related terms is established."

Standard
ESA

This ECSS standard details specific standards for ground testing of space flight hardware. The testing ... covered includes mechanical, structural, thermal, electrical, and RF - among others.

This site provides a high-level overivew, lessons learned, and recommendations related to thermal vacuum ... (T/V) testing. A NASA JPL study with a summary of analysis and test results is provided as an example when thermal/atmospheric (T/A) testing is performed instead of T/V testing.

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