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

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Patrick

Tue Apr 15 2014, 11:00PM

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

I think the GPS is the least significant problem, the greater problem is the computing of flight and operational commands. Besides it's looking like I need to switch between inertial nav and radio fixed beacon triangulation at fukushima/Chernobyle/Windscale/hanford sites.

BigBad

Wed Apr 16 2014, 12:47AM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600

Patrick wrote ...

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

It will help with some types of radiation.

Basically, there's alpha, beta and gamma.

Alpha and beta you might well be able to shield.

Gammas will just go straight through.

You've also got to watch out for secondary radiation; when you stop primary radiation, it creates a shower of secondary.

Basically, it's very complicated; and there's much less scope for shielding flying machines.

You might even be better off with very little shielding due to the lack of secondary radiation and just rad-harden everything.

Patrick

Wed Apr 16 2014, 02:00AM

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

Of this is a point of future research, clearly more in depth then I first realized... but please continue to comment everybody...

Carbon_Rod

Wed Apr 16 2014, 07:08AM

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

Most of the solutions to these problems have been documented for aerospace projects. We've seen consumer grade AVR processors in research satellites function just fine. However, I'd suggest looking at a 1990s version of an old Motorola 68HC (1st gen) or intel 32 486sx series based computer.

Note, that export of any hardened control system is now prohibited if the device is intended for an Unmanned Aerial Vehicle... even if for civilian applications.

Even the hardened fault-tolerant software developed by NASA would fall into this class.

Sulaiman

Wed Apr 16 2014, 07:59AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

As I see it, your key systems are;

1) Onboard flight control
2) Uplink receiver for flight commands
3) GPS receiver
4) GPS decoder
5) Onboard instrumentation e.g. Radiation measurement
6) Onboard video camera(s)
7) Downlink transmitter(s)
8) Ground based equipment

Item 8 should of course be in a low hazard area

Item 7 should be less susceptible to radiation than other key systems

Item 6, the live video downlink will show video noise
when radiation levels are high enough to cause electronic failures
.. early warning if no onboard radiation monitoring.

Item 5 is designed to work in a radiation environment

item 4 can be eliminated by directly sending the GPS receiver data to the ground station for decoding.

Item 3 could temporarily/intermittently fail
but the ground station decoder should be able to quickly re-synch,
especially if assisted gps is used at the ground station

Items 2 and 1 seem to be the most critical,
flight command receiver interference can be mitigated by the flight controller only accepting valid commands,
e.g. sending a digital data stream with error detection/correction.

I've no idea how item 1, the flight controller, can be 'protected'
Physical shielding of the core controller may be assisted by strategic location of batteries and less critical parts.

One minor thing, can radiation cause a LiPo failure .. catastrophic.

If the vehicle is small/light (not likely to harm the target site)
then it may prove cheaper to provide moderate protection
and accept the occasional lost vehicle,
and have multiple 'expendable' vehicles
as the relative cost of vehicles to project costs is negligible.

Proud Mary

Wed Apr 16 2014, 09:58AM

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

Patrick wrote ...

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.

NASA: Commercial Off The Shelf (COTS): Radiation Effects Considerations and Approaches

How Rad Hard Do You Need? The Changing Approach To Space Parts Selection?

Radiation Hardening at the System Level

BigBad

Wed Apr 16 2014, 08:00PM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600

Patrick wrote ...

Of this is a point of future research, clearly more in depth then I first realized... but please continue to comment everybody...

You should read this:

So gamma and neutron radiation is the most problematic; you can practically shield alpha and beta

Patrick

Sat Apr 26 2014, 03:02AM

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

So, would neutron emitters be present, or neutrons fast or slow be escaping from a reactor in the condition of those a fukushima? After all they aren't fully opened up as in Chernobyl...

Ash Small

Sat Apr 26 2014, 07:00AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Patrick wrote ...

So, would neutron emitters be present, or neutrons fast or slow be escaping from a reactor in the condition of those a fukushima? After all they aren't fully opened up as in Chernobyl...

"By March 23, 2011, neutron beams had already been observed 13 times at the crippled Fukushima nuclear power plant."

There are plenty of other articles regarding these 13 'observed' neutron beams on the internet.

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