
The ¬NED pin goes low on detection of a nuclear detonation [pdf] - robinhouston
http://www.maxwell.com/products/microelectronics/docs/HSN1000_REV3.PDF
======
idoh
So, my mom is a former Maxwell employee who now does her own defense
contracting, and makes this same type of part.

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.

~~~
kprobst
I thought EMP affected electronics regardless of whether they are powered at
the time of the burst or not?

~~~
ynniv
You can harden your circuits against EMP, it's just expensive and almost
universally unnecessary. Almost.

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kabdib
I've wondered about the following:

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;
    

or something like that. My question is: What is the line of code after that?

    
    
        *pKaboom = true;
        /*NOTREACHED*/
    

I suspect it's more complicated than that (there's an infinite loop of some
kind that keeps retrying the command sequence). I also suspect I will never
know, short of some very hush-hush software being open-sourced someday. :)

~~~
agmiklas
GCC has a noreturn pragma for this sort of thing. It lets you mark functions
as never returning, which can in turn help the optimizer generate code leading
up to that function's call sites.

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JonnieCache
They also sell something called the SCS750 which is apparently like a
BeagleBoard _IN SPAAAACE..._

[http://www.maxwell.com/products/microelectronics/product.asp...](http://www.maxwell.com/products/microelectronics/product.aspx?PID=SPACE-
SBC)

Datasheet:
[http://www.maxwell.com/products/microelectronics/docs/SCS750...](http://www.maxwell.com/products/microelectronics/docs/SCS750_REV7.PDF)

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.

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tdicola
Guaranteed to operate in ionizing radiation of 10^12 rad/s. Yikes, that's like
10 billion sieverts/s. Since a dose of something like 10+ sieverts is fatal
I'm guessing a human would be turned to a puddle of goo around that much
radiation.

~~~
kmm
1e12 rad/s is 10e9 Gray/s. Sieverts measure something else, dose equivalence.

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.

------
geuis
Here's a link to the product page,
[http://www.maxwell.com/products/microelectronics/product.asp...](http://www.maxwell.com/products/microelectronics/product.aspx?PID=SPACE-
NUCLEAR-EVENT).

Maxwell makes an entire array of microelectronics components. These are
generally meant for use in devices that are deployed into space environments.

~~~
JonnieCache
_"FOR SPACE"_

Holy shit.

So this is to protect your orbital weapons platform from EMP blasts?

~~~
pjscott
Or anything you feel like putting in space, that you worry might be near a
nuclear explosion or other source of intense ionizing radiation at some point.
Be prepared, as the boy scouts say. I assume that maxim goes double in space,
considering how expensive it is to put things up there in the first place.

~~~
sliverstorm
No kidding. I believe NASA had something like 3 dual-redundant flight
computers on the Voyager probes.

~~~
pjscott
Just think how much redundancy you could get, cheaply, with the advances that
have been made with Moore's Law over the years. Computers for space probes
don't need to be that fancy. It's totally feasible to build processors that
use error-correcting codes in their entire datapaths, have tri-modular
redundancy for all their functional units, and then are arranged alongside
several other identical processors for ridiculous amounts of redundancy.

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.

~~~
Nitramp
Redundancy in hardware is one problem. But then all those CPUs still run the
same software.

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.

~~~
gnaffle
<http://en.wikipedia.org/wiki/N-version_programming> It's used in Airbus
planes, for instance.

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.

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linuxlizard
"not authorized for use as critical components in life support devices"

Now try to imagine something using this part in such a way.

/* NED low. Turn off life support. Insurance companies now vapor."

~~~
jrockway
You, sir, have just _voided the warranty_.

------
bravesirrobin
I just love this bullet point: * Maxwell Technologies Specified, Controlled,
Tested and Guaranteed

So, I suppose if you experience a nuclear detonation and the chip doesn't go
off, you get your money back?!

~~~
dimitar
I think you can physically model the ionizing radiation of a nuclear event,
without actually detonating a weapon, just condoms are tested for elasticity
by filling them with pressured air and water.

The detector may have been tested before the discontinuation of underground
testing in the US in '92

------
jeffreymcmanus
the unit test for this thing must be awesome

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rphlx
Hopefully the Built-In Test pin doesn't trigger a nuclear event.

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JoeAltmaier
"Tested and Guaranteed"

Really? I would like to have seen that.

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illamint
Well, this is certainly cooler than anything I work on, nuclear destruction or
not.

------
fleitz

      while(ned_pin) {};
      party_like_its_1999();

~~~
pjscott
Remember to declare ned_pin volatile. (Sorry to be pedantic, but I was getting
physically uncomfortable about the possibility that it might not have been
declared volatile.)

~~~
sjwright
You're physically uncomfortable about indefinite 1999-esque partying? Do you
have something better to do when !ned_pin?

~~~
pjscott
Of course! When the !NED pin goes low, duck and cover like it's 1959.

(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.)

~~~
elliottkember
So hiding in a fridge might actually save you?

~~~
vidarh
Given how close to ground zero in Hiroshima and Nagasaki people actually
survived just by virtue of being slightly more shielded than people around
them: Yes, it'd probably at least increase your odds.

And it's not like the Indy movies aren't full of situations where his odds of
survival would've been ludicrously low.

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nobody31
Money back if not entirely satisfied!

------
jwallaceparker
Wow. Great article. This is big.

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marshray
I like how the logo on the package is the M from *Monsters, Inc."

Something else they make there, I suppose?

