Could an asteroid be used as defense ? How could I do this , if it's possible?

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    $\begingroup$ Defense against what? land based infantry? Another asteroid? The common cold? $\endgroup$ Jun 28, 2016 at 4:10
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    $\begingroup$ @cinnamon18 Best way to cure diseases :) $\endgroup$ Jun 28, 2016 at 4:19
  • $\begingroup$ This is very broad at the moment. Yes, there are ways to use an asteroid defensively. Or did you mean defense as an alternative for war (the US has a defense department rather than a war department)? Are you on a planet? In a space ship? What? $\endgroup$
    – Brythan
    Jun 28, 2016 at 5:07

2 Answers 2


Well it depends on what you want do with that asteroid.....

If you are at war with another planet, you can simply use a gravitational slingshot to nudge a passing comet/asteroid into that planet that you want to destroy. Though it takes a lot of time and energy. The best defence is a good offense :)

Or, if the other planet does the same thing (with smaller objects), instead of wasting energy from your forcefield you can (again) nudge a asteroid into taking the damage.(Kind of implausible, but still).

In fact, if you have a lot of time ( and lot of paranoid scientists) you can make passing asteroids orbit around your planet ! One asteroid orbiting around your planet won't do much, but if you have many, projectiles launched towards you might get blocked by those asteroids. Also the enemy will now have to calculate a way to get a projectile past those asteroids, so you get more time for yourself :) (though it makes space travel really annoying (getting past those asteroids))


It is not clear what you are asking, but the answer is probably "No" anyway.

  • Most asteroids are too small to slingshot around them. This requires a deep gravity well like Earth, Venus, or even better Jupiter or Saturn.
  • Using a slingshot to change course and save fuel reduces your freedom of maneuver. You have to wait for years, even decades to get the conditions for a particular flight. So they might be useful for offense, when you can pick the time for attack, but not for defense.
  • Slingshots produce relatively modest course changes by the standards of a setting where interplanetary war is possible.

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