# Acceleration in a vacuum

We all know that if you accelerate at 1g in a vacuum, you'd be pressed into the floor/wall of your spaceship in the same way that you're pressed into the ground on Earth; that is, you would have "Earth Gravity".

I got into a discussion with some people about the structural integrity of a spaceship, though. There were claims that it isn't important and that since there's no air to resist the acceleration in a vacuum, the ship would just move with no problem. Some people argued that if the structure wasn't sound enough and the acceleration force was large enough, the ship could crumple even with no air resistance, just from the back of the ship trying to push the front of the ship. I know that the force has to travel through the object as a compression wave, with molecules pushing the next molecules and so on, so it sounds right to me that the ship could be damaged by the force of the engines pushing it if the force was strong enough. Also, even with no air resistance, the mass of the front of the ship would still resist the change in acceleration due to inertia, so I can picture a poorly made middle-section of the ship being crushed as the back end tried to push the front end. Is that right?

Thanks for any thoughts.

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Yes if the engines were in the back, the forces would be the same on the accelerating ship as if it was standing still on the earth, on its engines. If the engines were in the front, then the spaceship would be pulled apart when accelerating.

Obviously you have to design it to be strong enough to withstand these forces, but that's the least of your worries when designing a spaceship!