I'm writing a sci-fi novel and I need some clarification on some technical issues.

An HEMP is an high-altitude EMP. A 400km high, high-yield nuclear explosion over Kansas could "switch off" all the continental US.

Yes, we could use a missile to take the warhead in the right position. But "400km" is also the orbital height of the ISS.

So: since that such a launch could be easily detected (I suppose), is it possible to put a nuclear warhead in that position using a "peaceful" space launch as a "camouflage"? What's the best way to do it?

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    $\begingroup$ I think it's fair to say that's something some very expensive analysts spent a lot of government time trying to figure out back in the day. And the details are probably still classified. $\endgroup$ Apr 21 '16 at 8:16
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    $\begingroup$ This really belongs to Worldbuilding.SE $\endgroup$
    – SF.
    Apr 21 '16 at 10:33
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    $\begingroup$ I actually think this is on topic. It has even been spoken of in recent presidential debates. There is considerable information that can be either gleamed or inferred based on public information. $\endgroup$
    – PearsonArtPhoto
    Apr 21 '16 at 12:50
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    $\begingroup$ I will add that NASA's upcoming James Webb Space Telescope will use mirror-unfolding technology once in space to put the telescope mirror in its final configuration. This is technology that has been declassified by the military (that's why NASA can use it) and apparently has been used before. It seems that the military has a very large spy telescope but I have never seen a specific reference to what that telescope is, when it was launched, or what it might be capable of. $\endgroup$ Apr 21 '16 at 16:21
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    $\begingroup$ I'd wager that the military used that for radar satellites, not optical. $\endgroup$
    – Hobbes
    Apr 21 '16 at 16:27

Classified satellites are launched all the time. For example, fourteen KH-11 espionage satellites were launched between 1976 and 2013, and we still have no idea what they look like. So you can launch pretty much what you want and nobody will know for sure what it is.

A satellite that does nothing would be suspicious, so you'd have to stick your warhead inside an operational satellite: one that generates enough data traffic to give a plausible explanation for its existence.

Long-range detection of a bomb is very difficult.

The Defense Threat Reduction Agency (DTRA), a unit of DOD, is pursuing capabilities to increase the distance at which SNM (Special Nuclear Material, i.e. uranium or plutonium) can be detected, with the goal of increasing it to 1 km or more.

(emphasis mine)

But all that doesn't matter. Space launches are easy to monitor, so everyone would know who launched this satellite. That makes it a one-shot weapon. When it's used, you can expect massive retaliation as soon as the victim nation is able.

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    $\begingroup$ Satellite that does nothing, or satellite that doesn't work? $\endgroup$
    – Joshua
    Apr 21 '16 at 16:11
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    $\begingroup$ @Joshua: Actually, for North Korea a satellite that "malfunctions" would be very plausible. $\endgroup$
    – dotancohen
    Apr 21 '16 at 16:17
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    $\begingroup$ Not sure why we need to go picking out individual nations. All space programs have had failures. The US itself has had plenty of malfunctioning satellites. Getting a little tired of all the jingoistic NK bashing! $\endgroup$ Apr 21 '16 at 16:45
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    $\begingroup$ @LightnessRacesinOrbit: Most space programs have also had plenty of successes, but I'm not aware of NK ever actually putting anything in orbit. Between that and their loud internal claims to have succeeded in putting something into orbit every time they fail miserably, the jokes just about write themselves. $\endgroup$ Apr 21 '16 at 17:02
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    $\begingroup$ @MasonWheeler A CNN article says "'Initial observations, available on the publicly-available website Space-Track.org, indicate these two objects -- NORAD catalog identification numbers 41332 and 41333 -- are at an inclination of 97.5 degrees,' said LTC Martin O'Donnell, spokesman for U.S. Strategic Command". - looks like satellite and booster are still up there right now! $\endgroup$
    – uhoh
    Apr 22 '16 at 20:37

First of all, yes, a payload can be launched in to space that would remain at the key altitude for a HEMP, and stay there for some period of time. This has been discussed in terms of North Korea, for instance, which has launched satellites into an orbit that a HEMP attack would be possible, although they likely don't have the payload capacity to launch a weapon in to that orbit today.

Okay, so how would one hide who did this? Hiding the launch is all but impossible, the United States monitors for launches continually across the world, due in large part to the ICBM threat. So one would have to launch a satellite that contained this as a secondary payload. Once the payload was in orbit, the HEMP payload would have to remain, something that large is essentially impossible to hide in LEO today. The track for the satellite would be well established for a long period of time in the future. That track would be tied to the country of origin.

Is it then possible to confuse who launched the attack? Well, maybe. The best way that I can think of would be to explode the weapon when it was physically close to another satellite. I don't know the accuracy of nuclear weapon detection systems, but if two or even 3 satellites were physically close, say, withing 10 km, it might be difficult to determine which of the 3 detonated the weapon. In particular, it might be an interesting scenario if there was both a US and a Russian satellite close together, along with this hidden device. It might be possible to track exactly what happened, but it would take some time. The primary satellite would be completely destroyed, the other ones would likely be in pieces, and non-functional, and even in different orbits, but given some analysis it would likely be possible to determine which satellite of the 3 was the culprit, although it likely would take hours to figure out.

Okay, a few more tidbits. The shape of the satellite might be known from the ground, due to advanced radar systems, which no doubt would be employed to their max for any "hostile" country's launch. Any such item would have to be disguised to prevent that, which might be met with varying success.

  • $\begingroup$ I think your "explode when close to other satellites" idea wouldn't work, because you could just track the orbits of the unexploded ones (and indeed the debris from the exploded one) to work out which one it was. $\endgroup$
    – N. Virgo
    Apr 21 '16 at 14:04
  • $\begingroup$ I think all of the satellites would be destroyed in such a scenario, but you might be right about tracking the orbital debris to work out which of the satellites it was. It would take some time, however, to work that out... I've added details to this effect. $\endgroup$
    – PearsonArtPhoto
    Apr 21 '16 at 14:07
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    $\begingroup$ The other satellites would stop working due to the EMP, and I suppose thermal radiation might move their orbits somewhat, but there would be no shockwave in the vacuum, and hence no force that could actually break them apart. $\endgroup$
    – N. Virgo
    Apr 21 '16 at 14:12
  • $\begingroup$ The debris from the exploding craft would have a high chance of impact, but yes, you are right about the differences in vacuum explosions. Hmmm... $\endgroup$
    – PearsonArtPhoto
    Apr 21 '16 at 14:15
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    $\begingroup$ I submit the best place to hide the HEMP payload is inside the upper stage rocket body. Catalog as main engine failed to ignite for de-orbit burn and RCS capacity insufficient to deorbit. $\endgroup$
    – Joshua
    Apr 21 '16 at 16:13

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