starship-design: Re: Vapor Trail Fuel

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

Pollutants

> mixing with the surrounding air by diffusion. Now this is a recipe for air
> pollution, definitely, for the vehicle can by no means scoop up all the
fuel

Lately I have been using a narrowed definition for air pollution, which
includes any carbon whatever the oxidation state. (AFAIK all carbon
compounds are IR absorbant e.q. greenhouse gases.)  Loosening my restricted
definition to a more common definition, if the fuel is burned to CO2 and
water we wouldn't normally count it as pollution. We can see that much of
the fuel which does not go through the scoop is burned anyway, on passage of
flames from the vehicle's jet. (Or after the launch, sweeping the area with
an IR laser may help clean up by igniting unburned wisps of fuel.) So by
most folk's criteria, there might be little noticeable pollution in such a
launch.

But space launches run hot, and always produce NOx. The hotter the flame,
the more nitrogen and oxygen combine. We got to burn hot anyway, because we
got someplace to go, and a short time to get there. But I have been thinking
of a way to reduce the acidity of hot flames, by including an admixture of
hydrogen where the nitrogen and oxygen recombine. The resulting ammonia gas
should chemically combine with the oxides of nitrogen on cooling, forming
ammonium nitrate, a perfectly eco-friendly solid fertilizer.

> small controlled release from a couple thousand feet altitude, most of
which
> will be burned off in a matter of seconds.
-----
> ... The vehicle may be
> lifted up into the fuel stream either under its own power, or by various
> launch assistance techniques.

See how noncommital? See how hard I tried not to say, "Shoot the launch
vehicle out of a gun"?

> This segment of level flight might seem almost a detour, for a vehicle
> headed way up yonder, but it should boost the vehicle to Mach 4
practically
> for free, in terms of onboard expendables.

I didn't mention the dirtside application I had in mind, that of
accelerating airships. No Mach 4 for them, but a good healthy boost to
leeward. Just why has nobody ever put a jet engine on an airship? With a
good start like this, an airship wouldn't need a turbojet engine with all
its associated weight, for a lightweight ceramic ramjet would suffice.

> ... Lighter means faster and way cheaper, more access. Actually I
> was thinking in kind of survivalist terms, a last-ditch way to haul lots
of
> people off a planet in hazard, when I came up with a gasoline streamer
> method of flight vehicle acceleration.

Or to haul lots of people out on airships if their particular region was
emperiled.

> ... But people should consider the
> concept of externally-fueled air breathing boosters, because they seem to
me
> about the best way to go if we ever do get the method right. There's a way
> to shoot fuel up just right so a ship can use it, a ship with just scoop,
> engine and payload.

Bet there is. I got two ways here, using windswept fuel streamers or a
one-shot hydrogen gun. Got any more?

"Just scoop, engine and payload" is exaggeration, stating an engineering
extreme, that those are the most massive ship components. I for one won't go
anywhere on a ship that doesn't keep fuel aboard at all times, even the
space shuttle, though I worked with that program for nearly nine years.
Sometimes things change, and it's sad when things change and you're out of
fuel.

Johnny Thunderbird