Re: Air-fueled aircraft on Titan

On 24 okt, 06:15, Steve Hix <se...@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
In article <gdql79$t9...@xxxxxxxxxxxxxx>,
 af...@xxxxxxxxxxxxxxxxxxx (John Park) wrote:

"Carey Sublette" (carey...@xxxxxxxxx) writes:

Either way (using ambient CH4 or carrying it as fuel) you could do a bit
better using fluorine instead of oxygen as the oxidizer:
http://en.wikipedia.org/wiki/Liquid_rocket_propellants

The greater reactivity and energy of fluorine should improve the lean
flammability problem.

Ook! Fluorine is much rarer than oxygen, harder to isolate, and, for us
carbon-based bipeds, VERY much nastier. I hope we're not that desperate..

How about a fission-core thermal jet using the atmosphere as the working
fluid? Lower gravity/higher atmospheric density works for us there.

Why jet?

US came close to building a nuclear plane. Based on B-36 - with its
six turning and four burning. Those six turning could and did carry a
payload of a running fission reactor. They considered a way to hook
the reactor output to propellers, but never tested it.

Titan has just 14 % the gravitational attraction of Earth. The surface
pressure is 1,5 times higher, and temperature roughly 3 times lower
(90 K on Titan, over 270 K on Earth). Which means that the air density
is 4,5 times higher. Since a wing has to produce 14 % of lift, the v
squared term should be 3,1 % that on Earth. Thus a plane flying on
Titan would need to have a true airspeed under 18 % that on Earth.

The thrust needed is proportional to the lift needed, so also 14 %.
Power is force times velocity (true velocity, not indicated
airspeed!), so a plane on Titan would need just about 2,5 % of power
to carry the same mass of engine.

However, the fission reactors scale down poorly.

If you want a chemical heat engine, though, a major issue will be that
the energy of a hot, well burned stoichiometric fire is unusable. No
material will convert it into useful mechanical work because no
material will stand the heat. Whether you are dealing with turbine
blades, piston cylinders or Wankel combustion chambers, they only work
on Earth because of excess air whose sole function is to keep the
gases cool enough to be usable. So, when you are carrying both your
reducer and oxidant, whether on Titan, Mars or Venus, you must figure
out a way to let inert local air cool your engine.
.

Relevant Pages

  • Titans Surface Organics Surpass Oil Reserves on Earth
    ... Titan's Surface Organics Surpass Oil Reserves on Earth ... Saturn's orange moon Titan has hundreds of times more liquid ... Several hundred lakes and seas have been observed, ...
    (sci.space.news)
  • Re: Shrinking Earth
    ... > Radioactive elements in the earths core could fission ... > Over geological time the mass of the earth would remain the ... in volume on fission. ... reaction of the fuel element's cladding with the heat exchange medium. ...
    (sci.geo.geology)
  • Rivers on Titan, one of Saturns moons, resemble those on Earth (Forwarded)
    ... Rivers on Titan, one of Saturn's moons, resemble those on Earth ... Parker, who has collected data from rivers all over the world, has ...
    (sci.space.news)
  • Rivers on Titan, one of Saturns moons, resemble those on Earth (Forwarded)
    ... resemble rounded stones lying in a dry riverbed on Earth. ... on Titan be anything like those on Earth? ... "The idea that rivers of methane moving chunks of ice on Titan ought to ... Parker, who has collected data from rivers all over the world, has ...
    (sci.astro)
  • Re: A setting question
    ... of aircraft on Titan +100 years as we see on Earth now? ... Oxygen could be liquified on Titan, given a little pressure. ... I wouldn't believe actual models and types of aircraft being used on ...
    (rec.arts.sf.composition)
Loading