NASA’s flagship mission to Europa has a problem: Vulnerability to radiation
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Even cold swapping would be nice. The challenge is that most missions are pushing their mass limit, and the extra hardware and volume to make swapping easy is something they can’t afford. Not to mention that “swap” implies connectors, and anyone who has worked with spacecraft hates connectors. Connectors are what fails, connectors are what cause problems with signal integrity, perhaps not quite as bad as valves, but they’re way up on the list, and most valves have connectors, for two reasons to hate valves.
This is, by the way, one of the big changes that launch vehicles like Starship will make - all of a sudden, you’re not trying to squeeze into a small fairing and remove every last gram of excess mass.
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Most radiation testing for total dose effects (which is at issue here, I think) is done with elemental radiation sources (e.g. Cesium 137 or Cobalt 60). I recall hearing numbers like “about $1/rad” for testing (So testing to 20 kRad is about $20k) The tricky thing is that the effects are different if it’s a high dose rate or a low dose rate. There are things like annealing (radiation damage heals itself, especially if the part is hot, the displacement in the lattice caused by a charged particle can “flow” back into place over time).
You use an accelerator for evaluating single event effects like latchup or single event upsets (bit flips) - different testing than total dose. The problem isn’t so much paying for accelerator time, it’s getting the time in the first place - there’s not a huge number of places that do this kind of testing, and they tend to be booked up long in advance.
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You're not buying enough to get a sales rep. $8 is a bit of an exaggeration. You're a few orders of magnitude too low for anyone to care. Once you do have the sales rep, then that rep will be concerned about that meager $8 purchase, because of the expectation that you're prototyping for something that will require thousands more units.
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Also note that Starship is doing everything possible to remove connectors. Flanges are replaced with welds. Welds are replaced with integral manufacturing. Even when you have mass and volume to spare, everyone hates connectors.
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And if you think electrical connectors are bad, try optical ones. There's nothing quite like "oh crap, this single-mode fibre tip has a burned face where a speck of dust touched it, now let's go track down every other connector face that it could possibly have touched since the damage first occurred...."
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In addition Io provides a large batch of particles to ionize and accelerate. You can even see the glowing footprint of Io in Hubble images of Jupiter's aurora.
Io's footprint shows up at the poles because charged particles are guided by Jupiter's huge magnetic. Ions going along a field line feel no force but trying to cut across them induces a spiral motion, so they spiral down and impact at the poles.
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I wouldn't expect optical connectors to be generally viable in space until they are made from explicitly covalently bonded materials. The optical interface is just too prone to material dislocations otherwise.
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SEUs are only part of the problem.
Some types of radiation will physically damage transistors changing their characteristics.
And just to make it extra weird sometimes you get behaviours where transistors get worse and then get less worse depending as dose increases.
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These are power transistors. I would expect they’re too large to be affected by SEUs.
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This is a dinosaur company, you are completely underestimating their strength. For example, you can recall the case when SpaceX sent its parts for military certification to a similar company in the USA. SpaceX discovered that the signatures on the certificates were too similar. After conducting investigations, they discovered that no action was being taken with the parts. The signature was simply copied and the parts were sent back. The company got away with it by simply throwing one person under the truck.
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That's definitely not true.
A story from a friend who was at Caltech around 1970 about a mission to Venus: (from memory... which may be failing). A Venus mission used a gem-quality, sapphire lens, valued at a large value (US$20k?) that was imported from overseas to the U.S. The sapphire was integrated into probe, and prior to launch, someone from U.S. Customs was shown the lens in the probe, and commissioned to witness the launch, allowing him to check off the 'exported' box on a form, saving the probe assembler from paying import duties.
I'm sure somebody here can make a better guess than me as to which probe it was.
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Bulk silicon is also prone to 'latch up', and as a result, rad-hard dice frequently use different technologies for chip manufacture, e.g., SOS (Silicon On Sapphire) or SOSE (Silicon On Something Else), where a thin layer of silicon is grown or mounted on sapphire or some other thermal-expansion-matched substrate. The very thin layer of silicon also makes the bulk much smaller for the absorption of radiation and generation of charged ions and free electrons in the silicon itself.
E.g., last I looked, rad-hard silicon-on-sapphire RCA 1802 "Cosmac" chips were still available commercially, and have for decades been popular as satellite controllers, despite being perhaps less powerful (compute-wise) than an Intel 8080.
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Interesting, thank you.
So exploiting a tax loophole by claiming "export" to save some money seems to have worked in the past. GG
I'd regard this as "loophole" as this still would be an export without a corresponding import and tax being paid elsewhere on import is the very reason this "exported" box exists in the first place.
As for the discussion's context of mandatory export regulation of space parts:
Can anybody confirm/deny that you need to run all parts send into interplanetary space or LEO through export regulations?
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It's been stated the affected parts were made by Infineon.
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MOSFETs actually make pretty good radiation detectors as the damage effects are predictable.
https://oncologymedicalphysics.com/mosfet-detectors/
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Would a lead enclosure for protecting the electronics (or even just the MOSFETs, depending on the case) be a possibility? Or the amount of lead necessary to protect it would be too much weight?
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I agree with the sentiment, but not the wording. To be exported, a product only needs to leave the country of manufacture. Space is not America, thus it should be an export according to my understanding.
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You have to be large enough for them to care and small enough for them to question whether you have an effective compliance program. Around fifteen years ago I bought components for PCB manufacture from Digi-Key for a multi-billion dollar company and never got asked about application.
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The “single event effect” (SEE, the generic term) that one worries about for MOSFETS is Single Event Gate Rupture (SEGR). Let’s say you’ve got a part with 100V Max Vgs - And for some reason, you’ve got 90V on the gate, and then a charged particle comes by at pushes the field at some location over the limit - bang, hole in the oxide film, and you’ve just got a failed FET.
There’s a theory that this is what happened to the radar power supply in SMAP:
NASA LLIS: Proximate Cause of the SMAP Radar Failure
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You do not. Launching into space is not exporting. You retain ownership as well, so if it falls out of the sky and causes damage, you’re liable. It is the “launching nation” that is responsible for policing this.Interesting, thank you.
So exploiting a tax loophole by claiming "export" to save some money seems to have worked in the past. GG
I'd regard this as "loophole" as this still would be an export without a corresponding import and tax being paid elsewhere on import is the very reason this "exported" box exists in the first place.
As for the discussion's context of mandatory export regulation of space parts:
Can anybody confirm/deny that you need to run all parts send into interplanetary space or LEO through export regulations?
However, let’s say your US built cubesat is being shipped to New Zealand for launch on an Electron. You DO need an export license (and you also need a NZ import license). Fortunately, NZ is not on anyone’s “list of designated countries”, so the license is straightforward.
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It doesn’t have to be lead - when it comes to shielding, it’s mostly “mass per area” that counts. Aluminum can be used, steel, tantalum, etc. If you know in advance, spot shielding of individual parts has been done.
As I recall, for Europa’s surface environment, shielding equivalent to a meter or two of water (so, 100-200 g/cm2) is sufficient to shield down to “normal“ levels of radiation.
But there’s a problem - shielding works pretty well for total dose, but not as well for high energy particles. For one thing, when that high energy particle hits the shield and gets stopped, that generates a bunch of new radiation (X-rays, often) - bremsstrahlung (Literally “braking radiation” in German). That’s how X-ray tubes work - shoot 100 keV electrons at a copper target.
There are clever shielding designs of multiple materials that are more effective - first layer stops the incident particle, subsequent layers stop the secondary particles, etc.
The other problem is that there are really high energy particles for which it’s not possible to shied enough (Galactic Cosmic Rays) - they’re going to come on through.
If you want to fool around with radiation and shielding models, take a look at SPENVIS
https://www.spenvis.oma.be/intro.php
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Juno is using a titanium vault, with walls 1cm thick.
https://en.wikipedia.org/wiki/Juno_Radiation_Vault
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And for neutrons, you want light weight atoms - water, paraffin, etc. But of course neutrons would not get trapped in Jupiter’s magnetic field.
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Right. Contact your other customers and briefly summarize the issue, and ask if they'd like to consult further with you on this. Communicate.
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Strictly speaking, GCR can be shielded against, but it takes about a mile of HRE (hard rock equivalent) to do it. Neutrino detectors are located deep in old mines for that reason. That obviously isn't practical for spacecraft.
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There is an old lawyer/cockroach joke here I am not going to repeat, but to say cockroaches were reportedly to have a high radiation tolerance.
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I'll disagree with you: without the appropriate process(es) and feature size(s) and technologies, dice won't be rad-hard. Depending on the application, the packaging may also matter a great deal. E.g., packaging may be critical for resistance to alpha particles (not penetrating) or itself cause problems (thorium in the packaging, as happened a few decades back), or may make problems worse due to creation of secondary particles, depending on the expected environment.
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Having conducted such tests informally, yes, cockroaches are pretty radiation tolerant. They are also vacuum tolerant. And plasma etcher tolerant. When your bosses buy surplus equipment, as you’re cleaning it up and making sure it works, you can have all sorts of fun.
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if you are talking about the one that did fairing work for SpaceX for a while, no SpaceX brought that fully in house afterwards.
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How difficult is it to set up a test environment, exposing semiconductors to radiation?
I would have thought that NASA would have done such testing, rather than completely rely on manufacturer specs.
I would have thought that NASA would have done such testing, rather than completely rely on manufacturer specs.
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for low intensity you can use elemental sources, high intensity, stuff that can cause latch ups and bit flips, you need a particle accelerator those tend to be booked up several years out.
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NASA does do some radiation testing (typically of parts that don’t have a radiation pedigree), and they do proton testing of assemblies going to ISS (things like COTS routers, etc.). There used to be papers at MAPLD (may still be, I haven’t looked) every year with lists of all the stuff that got tested.
(https://www.seemapld.org/ )Check out the archive of all the papers..
But for the most part, rad hard components are “designed” to be hard, and the mfr tests them in accordance with a variety of standard test procedures. The mfr often contracts that out to places that do such testing (e.g. TAMU or Brookhaven for accelerator testing). But, in general, DoD, NASA, and others wanting higher quality or rad-hard parts rely on checking the paperwork, rather than retesting. - one joke is that the QML and regular parts come off the same line, but the extra cost for the QML parts is the pallet of paperwork that’s delivered with the tube of parts.
Once the parts are tested, if the fab process doesn’t change, they would just do some sample testing from each lot, to make sure that nothing wonky is going on. Back in the day, there was significant change lot to lot, because processes weren’t as well controlled. Now, though, semiconductor processes are very, very well controlled.
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its also one of the things that x-37 is likely used for, especially with the FH launch.
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Not back in the 70s when these were built. CA was CA, with maybe one or two variants. Nowadays? I'd think it likely.
I wish I'd asked Joe more questions (this was 1992 or 93) and didn't think about it.
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There is a potentially missed opportunity here. Don't implant the transistors to begin with and let the Jovian radiation do that for you. Could end up with some novel new transistor types as well.
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How can anyone take you series when you in fact do not use a real name. For all we know , You could be just coping and pasting the above response
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