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In addition to radiation, acceleration, and vibration, a launch vehicle can encounter excursions in temperature, and critical electronics for guidance and control should probably be resistant to excursions that exceed limits beyond which its reliability decreases significantly.

Are there "space-specs" similar to mil-specs for maximum temperature?

Comments below this answer talk about things like semiconductors, batteries, and electrolytic capacitors as things that might (or might not) be happy at 200C.

Question: In general though, is there any information about a standard or guideline for maximum temperature for mission-critical electronics in spacecraft?

Barring the availability of any good sources for a temperature, is there any information or indication that might suggest 200C would make some components "unhappy"? For that context, the situation would be that this is a non-launch situation and the components, though not in use, would be exposed for hours.

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    $\begingroup$ Silicon carbide based semiconductors have been used in laboratory up to temperatures of 600 °C. There are commercial types for 200 to 300 °C. Silicium semiconductors are limited to 150 °C. $\endgroup$ – Uwe Jul 9 '18 at 16:01
  • $\begingroup$ @Uwe you can read more about SiC electronics for Venus in this answer but I didn't know you can get a guidance computer system for a rocket made from SiC. That still leaves all of the other components as well. $\endgroup$ – uhoh Jul 9 '18 at 16:09
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    $\begingroup$ There is no SiC based microprocessor today, SiC is mainly used for power semiconductors.It seems possible to build a SiC based computer, but this will be very expensive and will take some years. There should be some applications on Earth too, not only in Venus landers. $\endgroup$ – Uwe Jul 11 '18 at 19:46
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The typical temperature range for space-qualified electronics components is -55C to +125C (at the case). The spacecraft is designed to keep the components within their qualified range, usually with a 15C margin on each side, so -40C to +110C. Batteries have a smaller range, requiring more thermal control for their location, e.g. -20C to +40C for Li-ion.

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  • $\begingroup$ There are rechargeable batteries for higher temperatures too, for instance the sodium–sulfur battery operating at 300 to 350 °C. A test in space was done in Space Shuttle during mission STS-87 20 years ago. $\endgroup$ – Uwe Jul 10 '18 at 17:36
  • $\begingroup$ Why is the upper bound much more than the lower-bound? $\endgroup$ – Magic Octopus Urn Jul 10 '18 at 18:42
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    $\begingroup$ 0C is an arbitrary origin of the Celsius temperature scale, having to do with the freezing point of water. Which has nothing to do with electronic components (except maybe some batteries). So there is no meaning to the "upper" or "lower" bound of that range. It is simply a range of 180C. $\endgroup$ – Mark Adler Jul 10 '18 at 19:56
  • $\begingroup$ @Magic Octopus Urn: You may express the temperature range not only in Celsius but also in Kelvin if you don't like the numbers for the bounds. $\endgroup$ – Uwe Jul 11 '18 at 19:51
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Spaceflight hardware tends to be extensively designed. So you'll see documents that talk about the "thermal management plan" that design for specific temperatures at specific places, then quality plans to check those calculations, and test plans to confirm them further.

Air Force Space Command's SMC-S-016 "TEST REQUIREMENTS FOR LAUNCH, UPPER-STAGE AND SPACE VEHICLES" controls some of this activity on the test end. It gives some idea of what's involved:

3.22 Maximum and Minimum Model Temperature Predictions

The maximum and minimum model temperature predictions are the hottest and coldest temperatures predicted from thermal models using applicable effects of worst-case combinations of equipment operation, internal heating, vehicle orientation, solar radiation, eclipse conditions, ascent heating, descent heating, and degradation of thermal surfaces during the service life

3.23 Maximum and Minimum Predicted Temperatures

The maximum and minimum predicted temperatures (MPT) are the highest and lowest temperatures that an item can experience during its service life, including all test and operational modes. The MPT are established by adding thermal uncertainty margins to the maximum and minimum model temper- ature predictions

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4.4.2 Thermal Uncertainty Margins

For the purpose of thermal uncertainty margin specification, thermal control hardware is categorized as either passive or active. Passive hardware uses a thermal uncertainty margin, whereas active hardware uses excess power as a thermal uncertainty margin. Examples of passive and active thermal control hardware for purposes of uncertainty margin are identified in Table 4.4-1. enter image description here

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6.2.4 Thermal Development Tests

For critical electrical and electronic units designed to operate in a vacuum environment less than 0.133 Pa (0.001 Torr), thermal mapping for known boundary conditions may be performed in the vacuum environment to verify the internal unit thermal analysis, and to provide data for thermal mathematical model correlation. Once correlated, the thermal model is used to demonstrate that criti- cal part temperature limits, consistent with reliability requirements and performance, are not exceeded.

When electrical and electronic packaging is not accomplished in accordance with known and accepted techniques relative to the interconnect subsystem, parts mounting, board sizes and thickness, number of layers, thermal coefficients of expansion, or installation method, development tests should be performed. The tests should establish confidence in the design and manufacturing processes. Heat transport capacity tests may be required for constant and variable conductance heat pipes at the unit level to demonstrate compliance. Thermal conductance tests should be considered to verify con- ductivity across items such as vibration isolators, thermal isolators, cabling, and any other potentially significant heat conduction path.

Engineering Development Units (EDU) of cryogenic systems may be tested in a vacuum environment for early verification of system performance and margins, and assessment of parasitic heat leaks. A thermal balance test may also be conducted to demonstrate thermal control hardware and subsystem performance and to collect data for thermal model correlation.

The tests that result from this end up being complex, as they try to reproduce the entire sequence of conditions encountered:

enter image description here

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In short, I'm not aware of any "standards". There are some vague norms though these will depend upon the context.

The most important two bits of context are:

How you are defining temperature

You can refer to the temperature of a semi-conductor junction or the outside of its case, the board its mounted on, the baseplate of the box that the circuit board is in or the panel of the satellite. Any of these are different representations of the environment temperature. If the component is dissipative then there will be a wide variation in temperature across those different cases. As a purely made up example, with a baseplate in the range 40 - 60degC the junction of a power transistor could easily be in the range 110 to 130degC. The limit for such a component on a manufacturer's datasheet will depend on the current going through it.

Derating

The old world of big expensive satellites de-rates components for lifetime. That is, you take the maximum power that you want to operate the component, look up the permitted temperature as per the datasheet and then take off, say, ten or twenty degrees (again made up example) for a 10 year life and some other figure for a low duty cycle, if applicable and work out your new, lower, maximum temperature limit.

This derating bit is a probability game. Its not the same as finding a temperature limit that is both necessary and sufficient. You just get more failures at higher temperatures over a period of time. I suspect that the conventions that lead to this sort of derating, despite being spelt out in all sorts of Mil-HDBKs, are probably so arcane as to defy exact explanation. Perhaps someone else on this forum could help out with that bit!

I suspect also that there maybe a modern ground swell that says this is too conservative, though this very much comes down to you (or your customer's) risk appetite. I think it would be a very interesting topic as regards bringing the cost down though.

The comments to the related question you mentioned on space certification also all looked relevant to me, particularly the "New Space companies are kind of on their own".

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