Re: How Rockets Differ From Jets


Brad Guth wrote:
> The shuttle doesn't use such slush cooling of it's hull and, if all
> goes sufficiently well because nothing gets broken or they're not being
> utilized as a handy thermal feedback drone on behalf of yet another
> DoD/ABL star-wars field test, it seems that of all other such things
> being most pathetic about our shuttle is that it's primary inner
> structural foundation of their hull is made extensively of aluminum,
> that damn near melts just by looking cross-eyed at it.
>
> Surely the 1000°C sustainable capacity of basalt fibers, microballoons
> and of ceramic binders that can be further embellished with
> internal/external layers of spendy CNT and then Corelle/ceramic coated
> is worth looking into, that plus if still necessary the cryogenic value
> of utilizing the fluid radon as phase-changing into a vapor/gas instead
> of taking to much slush hydrogen along for the ride might seem
> advantageous, especially since the Radium-->Radon breeder reactor needs
> some place to temporarily store the produced liquid radon byproduct
> anyway, before it's subsequently phased into a gas and utilized as
> powerful ion thrusting.


The Shuttle uses a vacuum bottle design to stop heat penetration of the
hull. It is the R factor of vacuum that I have regarded as the best
way to insulate the outer hull from the inner.


> >Remember, however, that stopping a spaceplane going 200,000+ mph takes
> >a lot of stopping. Even if you slow to 50,000 mph or less the reentry
> >air friction heat will be . . . tremendous.
> Obviously you'll have to slow down to something less than 7.8 km/s (say
> 17,400 mph), as otherwise you're not ever coming down. Thus how much
> energy is that "slowing down" going to take per tonne?

The exact same amount of energy it would take to get the spaceplane
going that fast, in an airless vacuum, to begin with.


> BTW; by the time reaching Earth as arriving from the direction of the
> sun, why the heck would the Spaceplane still be doing 200,000 mph (89.4
> km/s)?
> I would have thought it would be somewhat costing up-hill by having to
> pull away from the likes of Venus and that other little pesky gravity
> sucking item called THE SUN, thus getting slower until being sucked in
> by the nearby gravity influence of Earth, which isn't going to
> significantly happen as coming away from the sun until you're within
> 16r or less distance from Earth.

You are already in the Sun's gravity well to begin with so it is
neutral with regard to Venus Earth transit. Get too close to the Sun
and it is a different matter.


With just the right amount of Venus
> slingshot utilized should get the arrival back at mother Earth as per
> arriving at whatever remaining velocity you'd think best manageable.

This is absolutely correct. Either Venus, itself, or it's moons could
be used for a slingshot. You can also do a 'gravity-free' burn by
waiting until you are some distance from Venus before you do a final
burn of 1 minute or so.



> Speaking about "air spikes"; What if the leading edges (most critical
> reentry surfaces) were essentially 100% radon-->ion thrusters or
> perhaps even just radon discharge accommodated?
> Wouldn't such fast moving ions of such terrific mass and thereby
> terrific KE worth of ion thrust react as somewhat fending off the
> atmosphere, as well as providing their nearly continuous and thus soft
> retro-thrust?

Reverse thrusting ion engines might work -- brilliant!

> >If you don't have to
> >tether down the dry weight vehicle so it doesn't float off, then those
> >engineers haven't done their jobs.
> I agree. However floating off in Earth's thin and relatively low
> density atmosphere plus rather substantial gravity isn't likely, unless
> displacing all of the available interior volume with H2.

Negative! Use vacuum. Vacuum is much lighter than H2. If you don't
believe me check it out. Compare the weight of H2 with . . . 0!


> Spaceplane air conditioning via nuclear reactor; namely a small
> multi-MJ U238/U239-->Radium-->Radon Breeder Reactor.
>
> Pressurised radon gas as having been created within a high pressure
> cooker of a Radium-->Radon Breeder Reactor, as a highly pressurized
> decay containment cell of providing liquid phase Radon, which is then
> routed through external heat-radiating cooling plates and, basically
> short-term stored within high pressure receiver tanks as a liquid cash
> that's 452 fold denser than Radon gas that's been cooled by whatever
> the nighttime/shaded environment of space can manage to provide, from
> which the refrigeration phase-shift into gas should represent quite a
> bit of thermal energy transferring capacity.
>
> Essentially your Spaceplane is in serious need of being as much nuclear
> powered as possible, at least as being supplemented with the byproduct
> of Rn222 that'll be utilized as Spaceplane shell cooling as well as
> fuel for accommodating all of those ion thrusters. I'm thinking this
> ion thrusting process could require several hundred MJ worth of applied
> energy, as there should be dozens of these fairly large (0.1~1.0 m2)
> Radon-->ion thrusters involved, and that's going to take a good supply
> of Rn222 plus the neceaasey MJ worth of applied electrons for creating
> all of those fast moving ions.

Sounds great if it works. Don't know much about Radon reactors. How
much will it weigh. That is a very important factor for a spaceplane.


> BTW; Airbus A380 supposedly carries 30 metric tonnes worth of
> structural composites, with a gross empty/dry mass of nearly 280
> tonnes, and a gross takeoff mass that'll soon exceed their original
> design limit of 590 tonnes (slush C12H26 fuel could easily add 10
> tonnes).

The airbus A380 was made to be . . . economical. Not 'state of the
art' with regard to it's weight. Not in the 'spaceplane' ballpark.


tomcat

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Relevant Pages

  • Re: How Rockets Differ From Jets
    ... of utilizing the fluid radon as phase-changing into a vapor/gas instead ... You're giving me the strong impression that your CNT Spaceplane as ... ion thrusting process could require several hundred MJ worth of applied ...
    (sci.space.shuttle)
  • Re: How Rockets Differ From Jets
    ... Radon is already in a high state of flux, having a half life of 92 ... a great deal of energy is liberated ... The radioactive fuel in a nuclear power plant generates 200,000,000 ... This is where your spaceplane = shuttle ...
    (sci.space.shuttle)
  • Re: How Rockets Differ From Jets
    ... Don't count on 'special' shockwaves or even air spikes to ... Thus radon can be compressed into an extremely dense liquid form, ... large enough sphere so that your Spaceplane could ... Kurt Vonnegut would have to agree; WAR is WAR, ...
    (sci.space.shuttle)