Why are inertial compensators only needed for crewed ships?

Question

Honorverse spacecraft move around using a reactionless "impeller drive" based on gravity manipulation. This drive can accelerate craft at thousands or even tens of thousands of thousands of gravities in the case of impeller missiles.

Crewed ships also have "inertial compensators" which protect the crew from the acceleration, and these have a limit on how much acceleration they can handle before failing. This limits crewed spacecraft to accelerations in the hundreds of gravities.

When I think about it though, this doesn't make sense. If the impeller drive is creating a gravitational field which causes the ship to fall forward, then there's nothing to protect against as all of the matter in a member of the crew will be falling at the same rate, and at the same rate as the ship.

If the impeller drive is not doing that but is, for instance only accelerating the drive system which then transfers the force to the rest of the ship, and the crew, mechanically, then the drive should destroy the ship just as readily as the crew when enough force to accelerate it at 300g is transmitted through it.

Physics and material engineering aren't my areas of expertise, but it seems like every single component of a missile would have to be made of something like the Scrith of Ringworld that transcends the properties of what we know matter to be rather than just being advanced nanotechnological materials as described in the books.

A force field that can exert balancing forces on the drive system and the rest of the ship to even out the force would resolve this, and so, make sense as an "inertial compensator" but then missiles would need the same compensators, and ships that suffered compensator failures would be destroyed rather than killing their crew while remaining intact.

Has this ever been addressed either in the text or in a pronouncement from David Weber? Am I underestimating the strength that is possible for nanotech materials?

Answer 1

If the impeller drive is not doing that but is, for instance only accelerating the drive system which then transfers the force to the rest of the ship, and the crew, mechanically, then the drive should destroy the ship just as readily as the crew when enough force to accelerate it at 300g is transmitted through it.

That's the case, which is why ships tend to break in half or fly into small pieces in case of a compensator failure. Sometimes they do remain intact, but probably <50% of the time (wild guess based on scenes I remember).

Missiles in the Honorverse, on the other hand, are designed to withstand multi-thousand-G forces uncompensated while remaining intact. The materials involved are ludicrously strong, being engineered down to the molecule like a much-advanced, more controlled version of nanotubes etc.

It would probably be possible to build ships that strong (there's text evidence of LACs being dragged about uncompensated at several hundred G*), but it would incur a weight penalty and be pointless since the crew would end up flat regardless.

No LAC crew could survive the sort of acceleration ships routinely pulled in hyper for the simple reason that their inertial compensator would pack up the instant they tried it. But if they took the entire crew off and removed or secured all loose gear, Valentine suggested, there was no reason the ships themselves couldn't take the acceleration on the end of a tractor beam.

*And RMMS Dorado of course, although the canonicity of that scene is disputable.

Answer 2

Human work spaces are full of soft objects, including humans, that are not designed for high acceleration. Think about what would happen in a modern wet navy warship if it were to suddenly jump to 500 Gs - all sorts of stuff would break and or move (until it hit a wall, where it would shatter or crumple).

On the other hand, missiles are carefully and specifically designed to withstand high Gs. For starters, they are solid all the way through, with every component fastened tight to prevent it from moving and supported so that it doesn't break. This is made easier by the use of "molycirc" - molecular circuitry - which is a hard, solid block of electronics - the three dimensional equivalent of modern printed circuit boards and chips.

Answer 3

Non-living things can be made far more durable than humans. The hard drive in your laptop, for example, is probably rated for an impact of 500 Gs; you aren't good for more than about a hundred even if you hit at the ideal angle. Proximity fuses and other electronics in "smart" warheads can handle accelerations in excess of ten thousand Gs.

Use basic high-acceleration construction techniques, throw in two thousand years of improved high-strength alloys, and it's not surprising that missiles can survive insane accelerations even without applied handwavium.