This topic covers thermal cycling testing of electronics. Thermal cycling involves heating and cooling the environment at ambient pressure to expose the unit under test to specific temperature extremes and a specific rate of temperature change between those extremes. Performance of the system is monitored throughout the cycling process to verify complete functionality at temperature limits and basic function throughout the testing (i.e., during changes in temperature). This is accomplished by running full functional tests at the first and final hot/cold plateaus and by operating the unit in a more static but active configuration during the entirety of the test to excite and detect failures. The goal of thermal cycling is to verify the performance of the design on qualification units and to identify any workmanship or material defects in acceptance units. Smallsat projects often do not follow traditional thermal analysis and manufacturing processes and utilize COTS components. Thermal cycling can be a valuable tool to significantly improve smallsat reliability by screening for thermal design flaws and workmanship defects.
Resource in this topic area are primarily standards and white papers that outline traditional processes for thermal cycling and book chapters that provide nuanced guidance and background information. This background information can inform careful modification of traditional processes for smallsat projects.
The relative simplicity and size of smallsats creates an opportunity to only conduct thermal cycling at a higher-level of integration and significantly reduce cost. If you choose to take this approach to thermal cycling, consider whether to exclude certain subsystems or components whose thermal ratings will require less extreme hot/cold limits and therefore reduce the overall quality of the test (e.g., batteries). In addition, make sure to weigh cost savings against the elevated risk of failure when testing at higher-levels of integration.
Make sure to turn the unit under test off and back on at each hot and cold plateau to verify that the unit can start up under these conditions. Failure to support hot or cold startup could lead to a failure to recover from on-orbit faults (or to start up at all following deployment/separation).
During qualification runs of your test, carefully monitor the humidity in the test chamber and, if possible, use a window to visually inspect the unit under test for condensation and ice. Nitrogen or dry air supplies must be capable of sufficient flow-rates to support the intended rates of temperature change such that the the temperature of the coldest surface on unit under test is never below the dew-point inside the chamber.
Thermal cycling is inherently dynamic - the humidity and temperature of the test chamber is changing and the electrical connections and operational states of the unit under test are typically switched repeatedly to check for hot/cold startup, nominal operation during transitions, and full functional testing. This means that if something goes wrong, the operator needs to be able to respond quickly to reduce the risk of damage to the unit under test. Make sure to include thorough monitoring of the unit under test and response plans to likely equipment failures or human errors in your test procedure.
It is important to recognize the logistical and technical complexity of thermal cycling and plan accordingly with sufficient budget and schedule. Determining appropriate requirements is relatively straightforward. However, setting up the facilities and procedures to support these requirements can be very challenging. Careful planning and qualification of the procedure is required to prevent damage to the unit under test (e.g., from moisture condensation or human error).
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.
In this report, risk perspectives of Class C and Class D (moderate and high-risk) programs are discussed ... and aligned with mission success expectations. Thermal test recommendations to achieve desired test effectiveness goals are provided along with the associated risks resulting from tailored thermal test parameters. Beyond providing cost-effective thermal test requirements applicable to many smallsat missions, this document provides extremely valuable context and data to support its recommendations and enable a detailed understanding of each test.
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.
This conference paper presents detailed thermal analysis and thermal environmental test planning for ... a CubeSat. It's a good case-study and example report for smallsat thermal analysts and thermal test engineers. Inputs, assumptions, methods, and results are all presented in detail.
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.
This document discusses the importance of early stress screening on flight hardware to identify latent ... defects to prevent schedule delays and program costs increasing. Pre-unit-level testing is thoroughly discussed and how it can be applied to the MIL-STD-1504E requirement for unit-level thermal testing.
This site provides a high-level overview of thermal cycling and relevant graphs and equations used in ... thermal cycle modeling. There are multiple similar lessons offered such as thermal test levels & durations, heat sinks, thermographic mapping of PC boards, etc.
This site provides a high-level overview of thermal test levels & durations and provides lessons learned, ... graphs, and equations. Detailed analysis and results of thermal dwell testing on spacecraft like Voyager, Galileo, Viking, and Mariner are discussed in detail with recommendations for future spacecraft provided.
This standard provides environmental and structural ground testing requirements for space hardware. This ... is a very comprehensive and traditional requirements document not appropriate for determining requirements for most smallsat projects; however, it provides definitions, baseline requirements, and specific methodologies for each type of test and can serve as a valuable reference to inform smallsat testing. This section titled "Unit Thermal Cycle Test, Electrical and Electronic" provides thermal cycling test requirements and related information.
This handbook provides in-depth guidance on testing of space vehicles. This is a dated but comprehensive ... source of space hardware test environments and processes that could be used to inform test planning and execution for smallsat projects. This section covers thermal cycling testing of space vehicles.