Re: starship-design: Vapor Trail Fuel

["bugzapper" <bugzappr@bellsouth.net>]

Centerless Turbojet Engine Details

In the case where there are two fans going each way, deosil and widdershins,
in front, for a total of four fans in the forward compression stage, and
four fans taking the thermal energy out of the jet in the rear turbine
stage, the forward escape of air is prevented by the two acoustic barriers
formed by the vorticity reversals between succeeding fans. Forward engine
sensors detect whether the incoming gas is oxidizing or reducing, and the
complementary gas is injected into the main gas channel. In place of a
flameholder, oxyacetylene torch flames are shot into the main gas channel,
from the periphery, to ignite it.

The vanes may have a variable pitch, or a variable rearward attitude, if
this can be arranged without excessive increase in the mass of the rotating
rim. The pitch should be decreased, and the rearward attitude increased, for
an increase in airspeed. As the vanes are deflected farther to the rear,
this opens up the central air channel like an iris, making a larger central
area unimpeded. The engine in this way should operate into the high range of
supersonic speeds, possibly to Mach 4. To operate as a ramjet, the fans have
to stop spinning and be locked back. As the airspeed gets faster, you put
less in its way.

Fuel Laying: A Third Way

A series of flying vessels laying out fuel, may be deployed into the path
projected as the orbit launch trajectory of a spacegoing vehicle. The first
requirement of these flying vessels is that they not ignite the fuel train
they are laying. To this end, their exhaust jets may be cooled, though this
would slow them down. Otherwise, their hot jets must be physically separated
from the fuel train, either by placing their single engine far forward in
the airframe so the exhaust is cooled passing the bulk of the fuel tank, or
by using multiple engines widely spaced so the jet exhaust will not touch
the fuel train. A combination of these factors may be used. These fuel
laying vessels should be reusable, but this may be difficult to achieve for
those which will go to extreme altitudes, which need to be extremely
lightweight.

This seems a more controllable approach (than the last two) to providing
fuel for an externally-fueled orbit launch vehicle. The fuel laying vessels
lay their fuel, then veer downward out of the path, then the launch is made.
Even an "externally-fueled air-breathing" launch vehicle is expected to
complete the run to orbital velocity on internal fuel and internal oxidizer,
as a rocket. The more fuel which has been laid for it, the lighter this
launch vehicle will be, in direct proportionality to its cost.

Is there a scaling down to model size on this? Like, take a model rocket,
and smother its jet with enough fuel vapor to cool it down, so the flame
front will never get out to the fuel-air interface? There may be a solution
like that, but I'm afraid a couple incidents might happen in the
experimental work. In trials before the safe conditions become known, the
entire fuel column might burn off. That would cancel the launch of the air
breather. Safer to separate the engines from the fuel, as above. For
instance, haul a fuel tank between three model rockets. When the fuel's
dispensed, deploy a chute to yank the rocket rig out of the path of the fast
ramjet that's climbing up the fuel trail. Get it right, and they might even
allow this at a rocket meet, so you could set some new records.

Johnny Thunderbird
http://members.100free.com/users/jthunderbird/