5 ms·
"To block gamma rays completely, you need about 13.8 feet of water, 6.6 feet of concrete, or about 1.3 feet of lead." https://www.epa.gov/radiation/radiation-b
by gafferongames 2y ago
"To block gamma rays completely, you need about 13.8 feet of water, 6.6 feet of concrete, or about 1.3 feet of lead."
https://www.epa.gov/radiation/radiation-basics#:~:text=Gamma%20rays%20are%20a%20radiation,be%20required%20to%20stop%20them https://www.epa.gov/radiation/radiation-basics#:~:text=Gamma....
- arijo 2y agoYou don't need to block gamma radiation completely to increase the electronics reliability :) Maybe you could improve the system availability considerably by a bit of gamma radiation protection combined with some more parallelism of the components ..
- adastra22 2y agoUsually partial blockage is worse, because you end up with a spray of secondary particles instead of a single ray.
- arijo 2y agoMakes intuitive sense, thanks for the insight. A second layer blockage for the secondary particles wouldn't have to be as dense or am I missing important physics? (I guess a lot of gamma radiation would still reach this second layer so please ignore my question :)
- adastra22 2y agoKeep adding layers until you get to 1.3 feet of lead and it’ll work.
- arijo 2y agohaha thanks for the correction - I was under the Turtles All the Way Down mindset :)
- numpad0 2y agoIsn't that more like how you make bombs than armors more effective - with backside spalling and secondary fragmentations?
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- exe34 2y agocan you block a hemisphere? the other 2pi steradians are shielded by the earth...
- m4rtink 2y agoMaybe the secondaries could be blocked by different/lighter materials ? Basically a Whipple Shield for radiation. :)
- adastra22 2y agoStopping power is basically correlated with mass.
- quailfarmer 2y agoThis may be true for high energy particles, but the majority of TID damage is done by higher flux lower energy, for which shielding is often viable!
- adastra22 2y agoThe point is that shielding turns a single high energy particle that would otherwise strike and probably destroy a single transistor, into a veritable spray of lower energy particles causing bit flips or worse all over the circuit. This spray of particles can be stopped... with 1.3 feet of lead shielding.
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- christophilus 2y agoA box with 1.3’ walls seems doable, actually, depending on how small the chips are. Might still be cheaper and more effective than specialized chips. But I know nothing, so am probably wrong.
- xmprt 2y agoLead is extremely dense so carry 1.3' walls of lead is probably more expensive than just having more redundancy or using better quality chips.
- thelittleone 2y agoIf the only thing that effectively shields these processors from radiation is lead, concrete etc (per earlier comments), what design changes / quality improvements can compensate?
- MetaWhirledPeas 2y agoDoes liquid fuel protect as well as water? Suspend the computers in the center of the fuel tank.
- jazzyjackson 2y agoI think the trouble is such a cube would weigh 12,400 pounds (a sphere maybe more reasonable at 6,510lb - without any room for electronics inside) https://www.wolframalpha.com/input?i=+lead+cube+with+side+length+2.6+feet https://www.wolframalpha.com/input?i=+lead+cube+with+side+le...
- paledot 2y agoHah, beat me to the nerd snipe. Moreover, that sphere would cost $10k to make and, at a launch price of $1500/kg, cost $4.5 million to launch into orbit.
- bboygravity 2y ago
- piyh 2y agoMore water in orbit sounds like a good idea to me
- persnickety 2y agoCan it even be blocked completely? Every layer of material geometrically reduces the proportion of rays going through. Or am I wrong about that?
- Filligree 2y agoNo, that's correct. Of course there's still some level of reduction beyond which the gamma rays don't matter, but where you want to place it is somewhat arbitrary.
- jiggawatts 2y agoJust put the electronics in the middle of the header tank.
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- jacobn 2y agoWould they need to be blocked completely? Maybe a much thinner shielding would still produce a significant benefit? (Though likely not of course ;)
- mttch 2y agoHigh energy gammas have a relatively low cross section, most are going to pass right through the chip. If you add a too little shielding, or don’t layer shielding appropriately you are going to stop more gammas but produce lower energy x-rays from the shielding, which have a higher cross section, potentially increasing your chip dose.
- orbisvicis 2y agoWould it be possible to create a "skip" EM shield that does the opposite - increasing the energy of the gamma rays thereby reducing the likelihood of stopping them?
- nine_k 2y agoNo idea how. Energies of most chemical bonds / electrons around atoms are not very high, not sufficient to emit proper gamma rays AFAICT. High-energy gamma rays are produced in nuclear reactions. While "clean" nuclear reactions that emit only gamma rays and not neutrons do exist, they are very high-energy and thus hard to initiate, and I don't think it would be easy to capture the energy of incoming gamma efficiently enough.
- orbisvicis 2y agoYeah, the problem is getting the EM and M fields to interact. I'm not sure creating gamma rays would help.
- quailfarmer 2y agoYes, you can attenuate TID effects with reasonably thin aluminum shielding
- wojciii 2y agoI would wish you would use proper units. ;-) But would using redundant systems separated in space connected with each other not offset the chance that they all would be affected at the same time? This is actually not rocket science .. just hard engineering and hardware/software design for redundant systems which is also usable on the ground.