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Let's say gravity drives exist. This is a device that can power a spaceship by creating an artificial gravity well some distance in front of the spaceship that the spaceship perpetually falls into, much like the carrot on a stick approach:

Carrot on a stick

This device requires a ton of energy to power (no violating conservation of energy), but is helpful because it allows space ships to accelerate substantially faster than 1G without squashing their occupants.

Here are the specs that I have so far:

  • The drive is quite big; let's say the size of an Olympic swimming pool.
  • The drive allows accelerating a 500m long ship at 10G (and has parameters that are appropriate for projection strength and projection distance to make that possible without imposing crazy sheer forces on the ship), but can't do much more than that on current energy production.
  • The drive doesn't work in strong gravity gradients, such as if it's sitting on a planet's surface.
  • The drive has some mechanism by which it doesn't violate conservation of momentum (like ejecting propellant opposite the attraction is necessary to maintain the gravity source).

What is a "good" military use/exploit of this technology (besides the obvious use of getting your spaceships to a place faster)? One key aspect of this technology is that it would take a lot of energy to power, so to be a "good" application, it needs to be something that can't be achieved with simpler technology on a similar energy footprint.

For example, can you use it to chuck asteroids at planets? Yes, but as far as I can tell, not for less energy than if you just pushed the asteroids with space ships with conventional chemical engines. So, unless I'm missing something in my analysis, I wouldn't classify this as a "good" use because it's not something that the gravity drive itself enables.

Example 2: can you put your gravity well in the middle of another spaceship to crumple it? Sure, but to count as a "good" use, this has to be more effective than hitting them with a payload from a mass-driver (and I'm not sure why it would be).

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    $\begingroup$ Your drive won't work. Momentum is conserved. You can do it (in reverse) with a negative mass carrot, but there are no negative masses, and if there were, very little about your universe would make any sense at all. $\endgroup$
    – g s
    Commented Apr 21, 2023 at 17:33
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    $\begingroup$ (Which isn't to say that you shouldn't have it, just that you should bury its mechanism under an unknown principle of science and decide secondary consequences, if any, arbitrarily.) $\endgroup$
    – g s
    Commented Apr 21, 2023 at 17:41
  • $\begingroup$ @gs The ship could eject reaction mass to offset if that's needed. I don't need this to be energy efficient; I need it to be able to do high acceleration on biological payloads without killing them. $\endgroup$
    – Zags
    Commented Apr 21, 2023 at 18:04
  • $\begingroup$ It sounds like the function of the device is to create a large uniform force field. $\endgroup$
    – Daron
    Commented Apr 21, 2023 at 18:17
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    $\begingroup$ As it stands, this question isn't a great fit due to its open-ended nature. There's a potentially unbounded number of possible answers which aren't wrong as such, but there's no useful metric for establishing which one (if any) is the right answer. I think you need to be more focussed than "enumerate all the possible uses of X". $\endgroup$
    – Starfish Prime
    Commented Apr 21, 2023 at 18:46

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Some initial commentary - in a Military context, concerns about Power Usage are generally second or third order concerns - Generally the Military cares about Firepower, Survivability and Mobility. If that means we have to have a bigger engine (like sticking a Jet Engine in a Tank or go with a Nuclear Power Plant in modern terms) so be it - so Energy Intensity is generally not what a Military cares about. If it does something that is useful - then we'll find the energy means to support that thing.

First thoughts:

1: Defence against projectiles/anything with Mass. Even a guided projectile that suddenly has to deal with small pockets of suddenly shifting Gravity is going to really mess with their guidance systems, even light-based weaponary can be bent by a Gravity field.

Why is this a good use? Because having an active protection system means you don't need to use passive protection systems or armour. A Lighter ship can either carry more payload for a given mass (more things that go boom) or it can be lighter overall meaning more agile.

2: Screwing with Sensors. "All war is Deception" - a Trick as old as time, if you can use your gravity drive to make a super-dense gravity thing appear somewhere you aren't to make it look like you are attacking from a direction that you aren't, then you have a significant tactical advantage.

3: Gravity Weapons. I know you said 'why is this better than a Mass Driver?' - well, for starters, you already have the Gravity Drive. Having a Mass Driver is another thing that you need to bolt onto your ship, if you can turn the Gravity Drive into an offensive weapon, then that's one less thing you need to lug round space. Plus a Mass Driver has to bypass the Enemies Armour/defensive systems, but a Gravity Well doesn't need to. As above - Energy be damned.

4: Anti-Infantry. Humans are squishy, a sudden 10G increase in gravity for 3-4 minutes could potentially incapacitate or kill all the people on an enemy ship (Blood rushing from the brain, oxygen starvation) - unless the enemy ship is completely automated, that's a really good way to safely disable an enemy vessel and capture it (then get all that lovely technology and intel - which often has a worth that is infinitely more valuable than any strength of arms).

I could go on - but yes. Defence, deception, and Anti-Infantry.

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  • $\begingroup$ The problem with bending light as a deflection system is that if you can see the thing, then aiming in that direction guarantees a hit. Doesn't matter how badly you contort space. Now maybe if you could rapidly and randomly change the contortions then you'd have something, but it'd have to be freaky fast or else your shield only works for a certain range. $\endgroup$
    – BMF
    Commented Apr 22, 2023 at 0:52

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