This answer to Where in the solar system could a nuke be tested without anybody noticing? has got me wondering if nuclear explosions (nuclear tests) in space above Earth ever produced any chunks of space debris. Were there any objects from the exploding vehicles that were subsequently tracked or observed, or did all of them completely self-vaporize or at least only make particles too small to track?

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    $\begingroup$ There have never been any nuclear explosions in Earth orbit. $\endgroup$ – prl Sep 7 '19 at 17:55
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    $\begingroup$ @Fred, while it’s true that not all the fissile material takes part in the reaction, it is all vaporized, along with the rest of the bomb parts. $\endgroup$ – prl Sep 7 '19 at 17:58
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    $\begingroup$ @prl okay I'll modify the wording, thanks for the heads-up! $\endgroup$ – uhoh Sep 8 '19 at 2:43
  • $\begingroup$ @prl, sure, no nukes from a spacecraft that reached orbital velocity, but there were twenty above the Karman line. $\endgroup$ – Camille Goudeseune Sep 8 '19 at 4:41

The U.S. detonated five nuclear bombs above the atmosphere. Not many minutes after one of these, nothing bigger than a molecule was left. So no debris, only a few radiation belts of high-energy electrons, which persisted for up to a few years. The other four explosions were likely similar.

As for the Thor launch vehicle, it was just a single stage (not trying to reach orbital velocity, so no second stage needed), so it was vaporized by the explosion.

The USSR also detonated some above the atmosphere. These were extensively studied because of the widespread damage their EMPs caused to terrestrial electrical equipment, but I see no mention in these reports of material debris, either orbital or raining back down to earth.

Reports about the three low-yield 1.7 kT detonations of 1958's Operation Argus (the Wayback Machine's best link is 2011 Jun 11; 142 pages) are replete with references to radiation belts (Argus's purpose) and the radiation precautions for personnel. But not a whiff in all of that about even the possibility of space debris. Google's ngram shows that we'd hardly started talking about that until twenty years later, never mind figuring out how to track it or even detect it. Because the launches were suborbital, any energy imparted to debris to achieve orbital trajectory must have come from the detonation. It's a safe guess that any such energy transfer would instead have vaporized the debris: Hiroshima's 16 kT caused "complete destruction" for about a mile, which for this 10$\times$ smaller explosion equals a radius of the cube root of 5280 feet, or 17 feet, comfortably beyond the missile's radius. Again, nothing bigger to track than a cloud of molecules.

  • $\begingroup$ It looks like there were about 20 tests total with about eight very low yield events between 1 and 10 kilotons. I think the low-yielders might be the best place to look for surviving debris, rather than Starfish Prime. $\endgroup$ – uhoh Sep 8 '19 at 2:50

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