As I understand it, when there is a nuclear event, it generates x-rays followed by the EMP. The goal is to have warheads in flight to be able to continue to their target, so the strategy is to employ an NED. When an event is detected, the warhead shuts down its electronics for the duration of the EMP, and then powers back up.
With her NED, she uses an ASIC for detection. I might get some details wrong, but the ASIC has a physical array in it, and the x-rays flip bits in the array. When enough bits get flipped, one can infer a nuclear event. Because it is an ASIC it is really small, which has important advantages for space-born avionics.
I genuinely wonder if people who work on this kind of stuff feel conflicted about it regularly, or don't think about it, or feel strongly that they are doing good.
For my mom, at first she was very gung ho about it - arsenal of democracy and the importance of having a strong nation. Now she is having second thoughts, and is looking to follow her passion which is something in the education space.
I doubt this, since the EMP is moving at the speed of light, whereas the delay times inherent in most circuitry and the time required to power down most circuitry would be at least an order of magnitude (most likely more) larger.
Explosions, like all other macro scale phenomena are not instantaneous, they just appear so until an appropriately small time step is applied.
No, "X-Rays" travel at the same speed as the "EMP" - both travel at the speed of light. They're both part of the electromagnetic spectrum.
The firmware controlling a nuke has to have, at some point, a bit or control register it sets that causes the explosion to go off:
*pKaboom = true;
*pKaboom = true;
exit(EXIT_SUCCESS); // or maybe failure, if we reach this point? :)
It's probably a lot more prosaic than I imagine.
It happened 175 days ago, when you made an unwise comment about killing children. All your comments since then have not been visible, or upvotable. This is why you're supposed to put contact information in your profile.
I hesitated before posting this, since from your older comments you appear to be a bit of a reddit user, and the comment itself contains several significant technical errors regarding the design of nuclear weapons, (American nuclear weapons haven't been of the "gun" type for 60 years now) which casts a poor light on the comment as a whole; but I don't think you're completely beyond hope.
Make a new account. Try not to be an asshole with it.
But the post was killed...
The reason they don't use GPS is that you would (hopefully) only start throwing ICBMs around if you are in "nucular combat toe to toe with the Rooskies" - and the way you know you are in a proper war is that all your GPS satellites have just been destroyed by the other side.
Its CPU is in fact triply-redundant, like pjscott was saying. They run in lockstep, and they do some fancy stuff that involves dumping the CPU registers to memory, "scrubbing" the registers and then restoring them. I recommend having a look.
Space is cool. Even when it does have nuclear weapons in it.
Interestingly, in this radiation field, every kilogram of mammalian tissue absorbs 10 GW. If this blasts lasts for more than a few nanoseconds, your puddle of goo would be a good guess.
Maxwell makes an entire array of microelectronics components. These are generally meant for use in devices that are deployed into space environments.
There's an interesting (if somewhat technical) document here: http://www51.honeywell.com/aero/common/documents/myaerospace...
So this is to protect your orbital weapons platform from EMP blasts?
This sounds silly, but the vast majority of the cost is non-recurring engineering cost. Manufacturing it would be a relatively cheap matter of sending the design to a fab like TSMC along with a bundle of money. Transistors are dirt cheap.
And anyway, what exactly does "redundancy" mean? If a rocket engine controller is triple redundant, how does that work? Are there three propellant valves in parallel, so each computer controls one-third of the thrust? Are they in series, so that failure of one computer disables the propulsion function? Is there a majority vote system, and is it electronic, electromechanical, or fluidic? Redundancy is not pixie dust that magically makes your system design better.
A sample Google interview question is to design the protocols to run a cluster of unreliable computers. Should there be a MIL-SPEC master computer? Should the cluster elect a master? Or several oligarch servers? Where does an outside agent submit a request, and what does it do if the request is not answered. Designing reliable systems is hard.
For self destruct systems you probably want all three to agree before going bang - while for an emergency escape system you probably want any one of three to be sufficent to deplay.
I vaguely remember being taught that this is the big problem developing real-time safety critical systems.
Alternately, it's possible to use asynchronous processor design and not worry about clock distribution. The tools aren't really there, but there have been async processors made before, and they work. They handle synchronization with local handshaking, instead of distributing a clock signal everywhere.
Another option is to abandon the cycle-for-cycle lockstep requirements, and just ensure that the synchronization time is bounded, and reasonably low. I know there have been some papers published about using this kind of globally-asynchronous-locally-synchronous architecture for realtime apps.
After Ariane 5 crashed spectacularly due to a software error that affected the two on board computers and the ground control unit likewise (http://en.wikipedia.org/wiki/Ariane_5_Flight_501), there had been talk about having the same software be developed by multiple, independent teams, and then use the different versions for error correction. Sounds like a crazy idea and probably won't work, but I don't really know of a better solution either.
Of course, it's useless if the specification is wrong, and the assumption that the differing versions will fail in different ways seems to not hold water.
(But I don't think I need the cavity search every time I enter the US that might come along with that...)
Now try to imagine something using this part in such a way.
/* NED low. Turn off life support. Insurance companies now vapor."
So, I suppose if you experience a nuclear detonation and the chip doesn't go off, you get your money back?!
The detector may have been tested before the discontinuation of underground testing in the US in '92
Really? I would like to have seen that.
(Fun fact: in a fairly large portion of the blast radius of a nuclear bomb, the main danger for people indoors is falling debris and broken glass from the pressure waves. Duck and cover actually works.)
Instructions start at around minute 18.
And it's not like the Indy movies aren't full of situations where his odds of survival would've been ludicrously low.
Something else they make there, I suppose?