this engine has a medium for acceleration the space inside the thruster demonstrates mass inertia and energy through disruption to the subspace barrier.
this drive disrupts the space time continuum at the front of the engine and stiffens it at the back of the engine essentially creating a warp drive. and no 5mm is not a measurement of length it would be a measurement of the amount of gravitational energy required to move an object 5 mm in a downward direction
Nikolai Tesla developed a radiometric thruster that could be used to get to mars and back using less energy than it takes to fall 5 mm in earths gravity when that said energy is converted into electromagnetic energy. the energy provided would be introduced at high frequency and high voltage through two parallel plates separated by two more parallel plates that act as insulation.
fig.1
please leave a comment or another design.
https://www.greenoptimistic.com/build-ufo-anti-gravity-spaceship/#.XBGB4VswiM8
inertial dampening would have to occur through an Inertia Dampening Field. this field would then have to occur through the use of quantum field matrix or another unknown energy matrix and through that field it would disperse all inertia throughout the specified object or specified space that this field would occupy