# How does inertial damping work?

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How does inertial damping work?

In: Physics

Firstly, in the real world…it doesn’t. It’s a ‘real thing’ in the fantasy world (e.g. Star Trek) and a hypothetical thing in the real world. In the world of physics it’s often referred to as “intertia negation”, which is imagined to be a process functions the opposite of ballast.

On a small scale we mute the affect of inertia with things that compensate – e.g. a padded seat allows you to sink in a bit making your rate of acceleration a little bit less than that of the object the seat is in, but it also dampens the _impact_ of the inertia by providing padding that prevents the harm of the acceleration on your body.

So there’s no real way to safely stop a large falling object, say, a block of metal without having an unrealistic amount of some sort of “padding”?

It doesn’t exist in real life. In science fiction, it’s often used to hand wave how a spaceship can speed up significantly in seconds without everyone and everything inside being splattered against the back wall.

In real life, astronauts train to survive up to around 10 g’s of force due to inertia. The space craft can’t reasonably accelerate any faster without endangering the astronauts inside. And while it may seem fast, it would take a very long time to reach a significant portion of light speed.

Any moving object has a given momentum, if its accelerating due to gravity, its momentum is constantly growing. The only way to reduce momentum is with an impulse, aka *force* x *time*. A 100kg rock falling from 10m has ~10000 Joules of energy and right before it hits the ground is moving at ~10m/s. Thus in order to stop it must recieve an impulse of 10m/s x 100kg -> 1000kg*m/s.

Since impulse is a produce of force and time, it can happen in a short amount of time with a very high force (aka an impact), or slowly over more time with a lesser force, like hitting padding or a spring. This cannot be avoided, it is a consequence of the conservation of momentum and to the best of our knowledge an unbreakable law of physics.

Inertial dampening is how sci-fi often hand waves away the deadly effect of high g-forces on spacecraft and people. For a unflinchingly realistic depiction of how realistic future spacecraft would operate, watch the show the Expanse, which on the whole only uses realistic physics.