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My understanding is that initial acceleration from the blast and following solar wind will clear the area around the asteroid for spacecraft navigation (in reasonable time). A 2-3 kilometer M-type asteroid (or smaller) would not have enough gravity to be able to keep around the dust cloud from the blast?

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  • $\begingroup$ I understand that there are concerns regarding residual radiation left on the asteroid, but this is not a question here. $\endgroup$
    – anon
    Jan 21, 2023 at 16:54
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    $\begingroup$ Every space faring nation has agreed to the Outer Space Treaty and have agreed not to put weapons of mass destruction into space, so this is pretty much a non-starter. $\endgroup$ Jan 21, 2023 at 20:25
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    $\begingroup$ Opinion-based questions are not appreciated at this site, and at many other StackExchange network sites. "What do you think ..." is asking for opinions. Also, push questions ("Here's my analysis. Am I right or am I right???") questions also are not appreciated here. Finally, questions that are pure sci-fi are not appreciated here. I suggest you take your question to Worldbuilding.SE. $\endgroup$ Jan 21, 2023 at 20:43
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    $\begingroup$ I don't think we need to close this question for "primarily opinion-based answers" now that thoughtful and science-based answers have begun. Voting to leave open. $\endgroup$
    – uhoh
    Jan 22, 2023 at 0:55
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    $\begingroup$ This question appears to imply that the non-core material isn't useful. That's probably not true. It can be a source of water, oxygen, construction materials, even reaction mass, as well as various interesting minerals. $\endgroup$
    – PM 2Ring
    Jan 23, 2023 at 1:02

2 Answers 2

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One kiloton moves both quite a lot and probably less than you need.

This study on nuclear craters along with a bunch of maths relevant to OPs interests has a table on page 24 summerising various actual blasts, including some subsurface low yield shots that got crater sizes around 100 feet and moved around 1 million cubic feet of material. While an asteroid will have lower density much lower gravity they provide a useful hard number to start with in terms of just turning blast into moved mass.

Moved into metric that is 28 thousand cubic meters, the table lists alluvial soil which is around 1.5 tonnes per cubic meter so 'moved' around 42,000 tonnes of material. It is notable that the table suggests smaller yields get more cubic volume moved per ton of yield.

Shifting 42k tonnes of material is great, but if we take Bennu as an example asteroid that is still only 0.00006% of the total mass.

So we have moved thousands of tonnes of debris into the space around our target making it rather hazardous, but only moved a relatively small portion of the overall asteroid so not necessarily useful if trying to clear overburden off a metal core or trying to fully 'pit' the asteroid by ejecting the core entirely.

Separate to the questions around getting nuclear weapons for this purpose, a crater made this way will tend to expose frozen volitiles to sunlight which will probably tend to outgas long after the blast keeping the crater area populated with dust and debris, a more controlled mechanical excavation may reduce this, or even allow them to be captured.

There may be mining situations where this makes sense, but it is unclear at this time what that would be - if we are after HE3 from the solar wind then we want to carefully strip the surface off without disturbing anything.

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  • $\begingroup$ The report says near-surface is that above or below? I $\endgroup$
    – Pioneer_11
    Jan 22, 2023 at 1:16
  • $\begingroup$ "GremlinWranger" - Thank you for a thoughtful answer! It brings several points I was not thinking about. $\endgroup$
    – anon
    Jan 22, 2023 at 1:20
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    $\begingroup$ @Pioneer_11 the report is interested in below surface level but given the limited data for actual detonations includes data for both. I based most of the answer on the Teapot ESS shot that was 1.2 Kt at -20 meters, which is also a useful data point on the machinery you'd need to place these. A 20+meter hole is not something you dig by hand even in zero g. $\endgroup$ Jan 22, 2023 at 2:43
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While I'd have to check exactly what yield you would need you could probably expose the core of an asteroid fairly easily. However, you run into several massive issues.

  1. the outer space treaty forbids the use of nukes in space

  2. you would create a vast amount of space junk of a whole range of sizes. This space junk would spread out in all directions and make it increasingly risky to approach the asteroid. Additionally given the very large energies involved the space junk would fly out to a range of nearby orbits.

  3. you've just made everything you want to mine fairly radioactive

Finally if you're wanting to mine the core of the asteroid then you're going to need mining equipment capable of cutting through whatever the core is made of. That means you already have the equipment to cut strait through the outer parts of the asteroid and reach the core, in which case why not simply do that?

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    $\begingroup$ Thank you for your answer. This is not a political forum, so I would not argue about chances to change the treaty if China were interested in this venture. Second, we are talking about the asteroid belt, not LEO. And collisions with a similar outcome (1 kiloton explosion) happen fairly often. $\endgroup$
    – anon
    Jan 21, 2023 at 21:50
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    $\begingroup$ Morgan Stanley says that in 15-20 years private Space Industry will be 1 trillion dollars. So remarks about SCI-FI don't make much sense. SpaceX evaluation already 130 billion dollars. $\endgroup$
    – anon
    Jan 21, 2023 at 22:08
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    $\begingroup$ @TheMatrixEquation-balance I'm not arguing politics I'm just saying that current laws forbid it. That being said it's often difficult to discuss space without politics as space programs are almost always government funded so it comes in along the way. Secondly Just because Morgan Stanley says something doesn't necessarily make it right or wrong. A lot of the future of space exploration depends on how successful starship is, the development of similar vehicles and various ISRU developments none of which are vaguely guaranteed. Basically everyone is usually guessing and trying to make headlines $\endgroup$
    – Pioneer_11
    Jan 21, 2023 at 23:01
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    $\begingroup$ @TheMatrixEquation-balance I'm not knowledgeable about the frequency of collisions in the asteroid belt, but space junk is always bad and you do not want to go making any more of it than you absolutely have to. Additionally, there is a big difference between two massive asteroids bumping into each other at low velocity, meaning most of the scattered material will also be low velocity, and be quickly recaptured, and nukes which will scatter space junk at high velocity, meaning it will both disrupt other orbits and be unlikely to be recaptured any time soon. $\endgroup$
    – Pioneer_11
    Jan 21, 2023 at 23:07
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    $\begingroup$ @TheMatrixEquation-balance you make several good points here that bolster the legitimacy and thoughtfulness of your question. It's just a suggestion, but in the future you might consider including some of this kind if thing from the beginning in your questions, to avoid the appearance of "Hey I just had a crazy idea, what if...?" that can attract reflexive down and close votes. While it's hard to add "prior research" to this question perhaps, at least add some "prior thinking-through" might help. $\endgroup$
    – uhoh
    Jan 22, 2023 at 0:50

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