On 11Oct2017 1234, C. Berry wrote:
> I like that for the cinematics, but a ship that relies on turbojets to
> achieve escape velocity is going to be unable to take off from a vacuum
> (or even non-oxygen-atmosphere) world -- which again plays hell with
> canon in general, and the various design sequences in particular.

I would assume they're a jet that uses heat exchange, with heat from the
reactor or drive heating air inside the jet. That lets them diffuse the
exhaust heat by moving a lot of (not so) hot air slowly rather than a
rocket exhaust very quickly. Loss of specific impulse isn't nearly so
important when you're not carrying most of the reaction mass (air) with
you. On an airless world, just use the rockets/thrusters normally.

IMTU ships use thrusters that happen to produce lovely blue waste 'heat'
that looks similar to a rocket exhaust, so they need to be on the ship's
surface and when in an atmosphere this causes a jet of rather hot air.
Thus they are a health and safety consideration when landing ships
(especially for those ships without contra-grav), and in combat drives
on increases your IR signature in the direction they're facing by a good
bit. It also means that powerful thrusters in atmosphere are not silent.

Also IMTU contra-grav units operating close to the ground will cause a
ground tremor with amplitude and frequency increasing with the mass of
the object covered by the CG. A flight belt would give a high pitched
buzz when within a metre or two of the ground that would only carry a
few metres. An air/raft a mid-high pitch when within a few metres of the
ground, carrying for a few tens of metres. A trader landing would give
off a deep bass that would carry for hundreds of metres. Those working
around CG vehicles a lot will be able to recognise standard CG sets and
vehicles by their vibration, and guess at the mass of unfamiliar ones.
It also means that grav tanks can be stealthy to other vehicles by
flying low, but grunts will be able to hear them at distances that will
be tactically useful in built-up areas while being out of LOS of the
tanks even if they're running their thrusters at very low power.

Basically, this prevents grav tanks and drones making infantry obsolete
in cluttered environments, by stopping them from being completely stealthy.

--
Rupert Boleyn <xxxxxx@gmail.com>
Chief Assistant to the Assistant Chief