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Programming Error Doomed Russian Mars Probe
astroengine writes "So it turns out U.S. radars weren't to blame for the unfortunate demise of Russia's Phobos-Grunt Mars sample return mission — it was a computer programming error that doomed the probe, a government board investigating the accident has determined."
According to the Planetary Society Blog's unofficial translation and paraphrasing of the incident report, "The spacecraft computer failed when two of the chips in the electronics suffered radiation damage. (The Russians say that radiation damage is the most likely cause, but the spacecraft was still in low Earth orbit beneath the radiation belts.) Whatever triggered the chip failure, the ultimate cause was the use of non-space-qualified electronic components. When the chips failed, the on-board computer program crashed."
Well... if you read TFA (or actually the first TFA linked), it is clearly written:
In a report to be presented to Russian Deputy Prime Minister Dmitry Rogozin on Tuesday, investigators concluded that the primary cause of the failure was "a programming error which led to a simultaneous reboot of two working channels of an onboard computer [...] Likewise, cosmic rays and/or defective electronics are not the leading suspects behind Phobos-Grunt’s demise.
The summary is clearly bolting together two contradicting reports.
The summary is so contradictory because it quotes from 2 articles, and each of them is completely different. One says that the parts were space-tested and fine, and the other says they were never space-certified and were definitely bad. The first one says instead that a software bug caused parts of the system to reboot. The second doesn't know what happened and just blames faulty hardware.
"If you make people think they're thinking, they'll love you; But if you really make them think, they'll hate you." - DM
Try this one on your hardware guys:
"The main purpose of software is to make hardware reliable".
Drives them nuts...
I'm not a satellite engineer, but wouldn't it be easy enough to just install a lead shield around the PCB to protect from most radiation? As long as the shield's not too thick, it shouldn't add too much weight, especially compared to using older-technology chips that'll take up more board space.
Well, that depends. Even on Earth's surface, we have to use ECC in more demanding application. In LEO, you lose the protection of the atmosphere but you still have Earth's rather strong and large magnetosphere. But this was an interplanetary probe. Once you get out of the radiation belts, interstellar and intergalactic particles start hitting you. You can't protect from those with a lead shield of any reasonable size. Pretty much the only way is simply to make the chip simple, rugged and design it with components (transistors) large enough that a particle flying through won't bother you much. Or add redudnancy. Or both, if possible (that's the usual case).
Ezekiel 23:20
As another EE with experience in rad hard space qualified design, he's not being self-contradictory. He's spot on.
If your CMOS structures are prone to latchup in the presence of single high energy events, then shielding does you no good. The amount of shielding necessary would more than consume the entire payload mass budget. Adding insufficient shielding just creates showers of secondary particles, each with more than enough energy to cause latchup alone, therefore rendering you at a statistical loss compared to no shielding whatsoever.
With this in mind means designing the CMOS structure to make shielding unnecessary. For example, build your circuits on bulk insulators instead of bulk semiconductor.
Just because you can't understand it doesn't mean he's self contradictory. You just missed his point. And then attacked him.
I can see the fnords!