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Recieving GPS In High Radiation Fields... (Among Other Unfavorable Situations.)

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LAN_403

Patrick

Sat Apr 12 2014, 06:36AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

maybe a "parallel input and logic compare output" is the lighter solution, with otherwise insuffcient lead post stamp sized over the IC dies' ? i suscpect i could live with 2 inches sqaure lead 0.125 inches thick on top and bottom of the main dies'. the lead would then be reducing probability of the trasnsistors being corrupted.

flight control (using PID and logic related calculation) is the only thing that needs to be real time and near radiation proof. if the drones constantly crash, there not of much use in fukushima or hanford, if humans have to keep entering radiation fields to flip them over and take them off again.

BigBad

Sun Apr 13 2014, 09:40PM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
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Radiation shielding is a git. It's one of a few areas where there's little substitute for throwing mass at something.

0.125 inch/3mm thickness of lead probably would not do a lot; you'd need more like several inches.

Patrick

Sun Apr 13 2014, 10:22PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

BigBad wrote ...

Radiation shielding is a git. It's one of a few areas where there's little substitute for throwing mass at something.

0.125 inch/3mm thickness of lead probably would not do a lot; you'd need more like several inches.

for a flying machine, 3mm of lead is all i can afford. the purpose of adding it selectively, was to reduce the probability of simultaneous-similar failures in the parrallel compare logic and MCU.

does that sound credible or useful?

im researcing boron carbide as well... 2.5 vs 11.3 g/cm^-3

Hydron

Mon Apr 14 2014, 01:05AM

Registered Member #30656 Joined: Tue Jul 30 2013, 02:40AM
Location: UK
Posts: 208

There was some research done during the cold war into lightweight shielding for nuclear aircraft. Both the US and USSR had a go, but I don't believe either really cracked it before ICBMs made the concept redundant.

Andy

Mon Apr 14 2014, 01:24AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
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Patrick Zr hydride I think would stop particles, not sure about the gamma rays thought. The particles have a high chance of impact in the metal, used in nuclear fuel rods, its type of like styfrom, which has the same effect, and I think used in nukes for the same reason.

Carbon_Rod

Tue Apr 15 2014, 03:05AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
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Posts: 1155

In general, most modern GPS units support assisted positioning signal carriers (undocumented modern feature on some units). Since GPS is a relatively weak signal, it is often jammed by external interference.

Heavy shielding will unlikely work since the signal amp itself may undergo signal corruption in a hot environment. However, I doubt you will have any real issues with aluminum foil over the electronics, and an exposed ceramic antenna. As if you do encounter problems, the Gamma radiation will jam your control systems and recalibrate your crystal clocks anyways....

The AM tube receiver French-fry controlled pigeon is always an option....

Patrick

Tue Apr 15 2014, 05:57AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Some of those pigeons and bats went out, but never came back. And the Japanese in 1945 saw the consequences...
kinda feel bad for the animals, we humans just have to draw them into our affairs...

Proud Mary

Tue Apr 15 2014, 08:59PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Forget all this stuff about burdening your flying machine with Pb, and think instead of bad electron hole pairs created when gammas knock electrons out of insulators. You get a nasty case of positive trapped charges shifting the operating characteristics of your devices which will no longer turn on and off in the way you would wish. We call this malfunctioning.

'Hardened' circuit designs are most often remedies for trapped charges and leakage disorders. High levels of redundancy may be needed in mission-critical circuits.

There's no point worrying about direct and irreversible damage to semiconducting crystals by neutron bombardment, as the neutrons can go wherever they like on the flying machine scale of things.

Sorry that I haven't been around so much lately, but I have quite a lot on my plate at the moment.

Patrick

Tue Apr 15 2014, 09:58PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Proud Mary wrote ...

Sorry that I haven't been around so much lately, but I have quite a lot on my plate at the moment.

no prob, but im still wondering how they built the Cassini and Hubble spacecraft.

Electra

Tue Apr 15 2014, 10:51PM

Registered Member #816 Joined: Sun Jun 03 2007, 07:29PM
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Posts: 156

I seem to remember reading somewhere the old fusible link proms were used space missions, as a bit in an eprom could be changed by a particle, donâ€™t know theyâ€™d stop the cpu from crashing, but I suppose if the program code wasnâ€™t corrupted at least it could run again once re-started.

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