What's the pricing on those chips?
The ¬NED pin goes low on detection of a nuclear detonation [pdf]
41–50 of 86 posts
Re: The ¬NED pin goes low on detection of a nuclear detonation [pdf]
#42Well, this is certainly cooler than anything I work on, nuclear destruction or not.
Re: The ¬NED pin goes low on detection of a nuclear detonation [pdf]
#43So, 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, a…
I thought EMP affected electronics regardless of whether they are powered at the time of the burst or not?
EMP generally refers to the radio-frequency flash. This device is for the ionizing radiation flash -- gamma rays, x-rays, and neutrons -- that can be extremely damaging to devices that are powered on. For example, the ionizing radiation can cause power transistors to turn on unconditionally, which can fire rockets, burn out power converters, and so forth.
Re: The ¬NED pin goes low on detection of a nuclear detonation [pdf]
#44Earlier quoted context omitted.
I'm fairly certain that ICBM's use inertial guidance with predefined/computed coordinates ( http://en.wikipedia.org/wiki/Inertial_guidance ). There's no software involved, its all physical. Detonation is (probably) trigged by a combination of altimeter, accelerometer and other telemetry systems.
Yeah, GPS doesn't work so well through the plasma sheath around a reentry vehicle. And you don't have a whole lot of time to acquire GPS lock, or steer, when you're still traveling at hypersonic speeds and it takes maybe half a minute to hit the ground after first encountering the upper atmosphere.
Cruise missiles, on the other hand... Well, let's just say there are eye-witness accounts of one flying down the street and turning the corner at an intersection before detonating in a tiny radius. All the was left of the target was a single shoe, IIRC.
Re: The ¬NED pin goes low on detection of a nuclear detonation [pdf]
#45Earlier quoted context omitted.
I'm fairly certain that ICBM's use inertial guidance with predefined/computed coordinates ( http://en.wikipedia.org/wiki/Inertial_guidance ). There's no software involved, its all physical. Detonation is (probably) trigged by a combination of altimeter, accelerometer and other telemetry systems.
Yeah, GPS doesn't work so well through the plasma sheath around a reentry vehicle. And you don't have a whole lot of time to acquire GPS lock, or steer, when you're still traveling at hypersonic speeds and it takes maybe half a minute to hit the ground after first encountering the upper atmosphere.
On U.S. ICBM's the there is no single detonation circuit. US nuclear bombs are "hardware encrypted".
So nuclear bombs go off if they have a certain physical layout that leads to supercriticality. What this means is not really relevant here, save that you have to have X pieces of "material" within a few mm of their "ideal" location, which is a big 3d puzzle that is very non-trivial to solve.
The inside of a nuclear bomb contains about 30 "traditional" detonators. When you fire them a piece of the bomb material (either uranium or plutonium) gets shot out of a cannon, into a tube that is a few centimeters long, with the "detonation" position randomly selected within a certain range. These positions are what's inside the president's suitcase.
You can launch a warhead with the wrong codes (right launch code, wrong arming code), in which case it'll basically be a small bathtub falling out of the sky. With useless fissile material inside, properly isolated (because melted into steal) and contained nuclear material inside. A non-detonated warhead is useless without enrichment facilities, and if you have those, chances are you have bombs anyway (there is 1 country in the world with enrichment facilities but no bomb, no it's not Iran).
What you need to do to detonate the device is quite complex, and very finicky. And of course, the actual detonation system is redundant. So the warhead decides to detonate, and only when it decides it will detonate in the very near future (the "point of no return") it will send the arming codes to a set of processors sealed deep inside the actual bomb. These processors will then fire the charges catapulting nuclear material along their tubes, with the sequence and timing provided by the arming code. Either the codes are correct, and the bomb will detonate, or they're incorrect and the fissile material will melt into the casing. These processors don't have any idea which of the two will happen.
Once launched, the bomb WILL send an arming code to the processors under certain circumstances it will send known wrong codes (it will not detonate outside of the target area). Once the umbilical is detached, a wrong set of arming codes are sent to the detonators and a timer is activated which will cause them to fluke-detonate. Anything touches the arming mechanism, they destroy the bomb. Anything happens to either processor, they destroy the bomb. Anything tries to unscrew the internal access, they destroy the bomb ...
Accepting any arming code, right or wrong is done for 2 reasons. First, there is no-one in the US military except for 2 people that can detonate nuclear warheads (there are more which can launch them though). I believe that a third person holds the detonation codes, but has no access either directly or by giving commands to others, to the bombs. Second, if someone holds a gun to the president's wife head he can launch the missiles which will do nothing more than destroy the US nuclear capability without doing anything different from when he's actually ordering an attack.
Re: The ¬NED pin goes low on detection of a nuclear detonation [pdf]
#46Earlier quoted context omitted.
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 ridicu…
Aren't the mechanisms of Moore's Law (ie. smaller transistors that run at lower voltages) exactly the same things that make chips more susceptible to radiation? Once you compensate for that by including more redundancy, you may not have a cheaper chip.
Yes. More dense, lower power chips are more susceptible to radiation.
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.
Re: The ¬NED pin goes low on detection of a nuclear detonation [pdf]
#47Guaranteed 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.
A nuclear bomb emits a fast flash of radiation over about 50 nanoseconds. Even if the total dose is small, it arrives fast enough to spuriously turn on transistors.
Re: The ¬NED pin goes low on detection of a nuclear detonation [pdf]
#48"Tested and Guaranteed"
Really? I would like to have seen that.
Re: The ¬NED pin goes low on detection of a nuclear detonation [pdf]
#49Money back if not entirely satisfied!
Re: The ¬NED pin goes low on detection of a nuclear detonation [pdf]
#50Earlier quoted context omitted.
Aren't the mechanisms of Moore's Law (ie. smaller transistors that run at lower voltages) exactly the same things that make chips more susceptible to radiation? Once you compensate for that by including more redundancy, you may not have a cheaper chip.
Yes. More dense, lower power chips are more susceptible to radiation. 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 ele…
Depends on the desired outcome.
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.