# Artificial gravity and inertia negation

In my universe, spaceships use a device that can generate a bubble of gravity that is homogeneous and unidirectional. You can manipulate the direction and intensity of gravity in any way you want. The end result is convenient Earth-like gravity everywhere on the ship.

Spaceships commonly use gravity assist for acceleration and deceleration. Because humans are squishy by nature, that puts hard limits on how much you can accelerate, which is hardly ideal.

So, is it possible to use my artificial gravity generator to negate inertia? Preferably so that you wouldn't be able to feel a significant difference (alternatively, an unpleasant difference) between dead stop and full throttle, or that a coffee mug on a table wouldn't spill everywhere.

Bonus question: what other uses could such an artificial gravity generator have?

• Gravity is basically acceleration, so you can use the gravity generator to negate the acceleration of the ship. Assuming the engine and the generator are consistent (i.e. not rough like an old car engine), there should be very little force felt. Another advantage would be that you would be able to take off vertically and make it feel normal. If the gravity generator is sufficiently cheap, you can use it as a handy way to reach hard-to-reach places, or to put objects in places that are normally impossible. May 31, 2016 at 12:41
• Gravity manipulation is one of the key technologies in David Weber's Honorverse - they use it for construction, communication, propulsion, protection, and attack. May 31, 2016 at 13:06
• What, your people haven't invented inertial dampers yet? Get with the times! May 31, 2016 at 13:21
• One bonus application is if you increase the gravity would time not pass more speedily (like in interstellar)? This could potentially create one way "time travel". May 31, 2016 at 16:04
• The Higgs Boson could be interesting to read about. Jun 1, 2016 at 11:59

The equivalence principle (postulated by Einstein) states that gravitational and inertial mass are the same (https://en.wikipedia.org/wiki/Equivalence_principle). So, even if you could create an artificial gravity field in your spaceship, the inertial mass of objects within that field would not change. To reduce the inertial mass you would need to have a machine that actually changes the true gravitational mass.

Gravity within the ship will only have to compensate for it's own acceleration. External gravity (such as from gravity assists) will apply equally to the ship and everything in it, and will have very little discernable effect. The ISS actually experiences almost full earth gravity, but because it's in freefall, it seems like zero gravity on the inside.

Acceleration will apply across the entire ship uniformly, and can be countered by tuning the angle and intensity of your gravity bubble.

Other uses:

Propulsion - If this isn't reactionless, you can apply a small gravitational field to the air, ground, water around you in a large area and accelerate pretty quickly without needing traction. This could potentially be a lot more efficient than existing air and watercraft propulsion, especially rockets. With a very large bubble, you could even get some thrust in space.

Hovering - Again, if it's not reactionless one can use a small, intense gravity bubble below something as a kind of frictionless multidirectional wheel.

Inertial damping - It was the original point, but it's important. highly manoeuvrable craft like fighters, drones and missiles get much faster and more manoeuvrable if they don't have to worry about ripping themselves apart.

High speed aircraft - normally these are uncomfortable due to constant turbulence, and high G forces when manoeuvring. If an aircraft could accelerate a bubble of air around it, this is not a problem as the turbulence mostly happens near the boundary of the bubble.

Pumping - A weak gravity bubble across a spaceship corridor can circulate air without inconvenient fan blades.

Weapons (launcher) - A series of high-intensity gravity bubbles in a line is essentially a railgun, with the additional bonus that what you launch will experience no g-forces, no electric current running across is, no intense magnetic field and does not have to be conductive.

Transport - Since we can apparently survive being fired out of a cannon, if we are fired into the barrel of an equally powerful cannon elsewhere we can travel by cannon. Probably a bit silly, since this enables many other wonderful vehicles.

Heavy industry - This could make lifting heavy things much easier.

• Welcome to the site Steven, well thought out answer. For more info on the site check out the help center and feel free to visit in Worldbuilding Chat Jun 7, 2016 at 13:27