Re: The Cold Equations


Brad Guth wrote:
> tomcat,
> This following topic might interest itself as being a partial solution
> to your megatonnage spaceplane that supposedly floats because of its
> less than paper thin composites. Thus "space flight is nothing to be
> afraid of" because of your conditional laws of physics stipulates that
> space radiation and debris are apparently as invisible and thus as
> harmless as were all of those supposedly nasty WMD that have been
> replaced with IEDs, that are actually quite visible but only manage to
> kill more than their fair share of innocent folks.
>
> 25%c Interstellar Probe in Our Lifetime - by: IsaacKuo
> http://groups.google.com/group/sci.space.policy/browse_frm/thread/a8dc97990c758b23/7d94a24e33c1e2f2#7d94a24e33c1e2f2
>
> I noticed that you couldn't manage to answer as to the megatonnage of
> crude oil that's taken in order to place a given tonne into orbit. Why
> is that?



Well, Brad, I am not a physicist either. But I will attempt to delve
into it a bit with what little I know.

Atomic Bombs are one thing, and manned spaceplanes are another. The
radiation that nuclear propulsion -- regular type, not your design --
creates would require either very heavy shielding or have to be placed
quite a distance away from the crew quarters so square of the distance
can diminish the intensity of the radiation. (Also, environmentalists
would go 'nuts' if such a thing were launched from the earth.)

Now, your idea is that Radon is less radioactive but still packs a
punch. I suspect, however, that heavy shielding will still be
required. To generate the kind of thrust a rocket needs to break the
bonds of gravity it has got to be producing radiation like crazy.
Correct me if I am wrong on this point.

In fact, I am concerned about the 2 'little' nuclear reactors I would
use to produce electricity for ship operation on an interplanetary
voyage. Putting them in the rear with shielding only on the side
facing the ship cuts the weight, but the environmentalists won't like
it. These 'electricity' producing reactors, however, will be very
small compared to any that would be a primary source of energy for the
main drive.

Atomic hydrogen fuel gets around all this radiation problem because
there is none. It is 'atomic' only in the sense that extreme cold
reduces the hydrogen molecules to atoms. When the atoms recombine into
molecules, which they will do automatically upon warming, enormous heat
is 'instantly' generated. The liquid helium that helps cool the LH2
into slush, and hold it at temperature in the tank, adds greatly to the
thrust when it 'instantly' expands into gas in the combustion chamber.
The only R&D I see here involves the design of well insulated tanks to
insure that proper temperature is maintained. The SSMEs combustion
chamber and throat may have to be reinforced, but might work as is.

Getting back to what I understand of your idea, using your minimal
radiation radon reactor to fuel ion engines might be workable. Ion
engines don't need huge thrust to simply increase a spaceplane's speed
once it has blasted off from the Earth. Therefore, your reactor could
be fairly small -- similiar to my electricity ones -- yet provide
enough power for both the ion engines and shipboard electrical
requirements. Remember, however, if your radon reactor is a new idea
then R&D looms ahead, and that means lots and lots of money and time.

Also, when you speak of using liquid radon products to cool the ships
hull I envision 'radiation' sweeping through the ship in tubes
irradiating everything in sight. Perhaps I am wrong, however. LH2 is
efficient in cooling the interior of the ship because it has to be
warmed prior to combusion anyway. Just as easy to use the ship as it
is to use warming tubes of some kind. The SSME solves this problem, by
the way, by having the fuel flow through the Bell prior to entering the
combustion chamber. This cools the bell and warms the LH2
simultaneously.

Rocketdyne has the SSME fully tested and proven. It is extremely
reliable. It is a high power, non-polluting, rocket engine that is
here and ready today. All of the LH2 and 'slush' tank design has been
done and works. Atomic hydrogen is still in the R&D phase but should
be out of that soon. This is off-the-shelf 'plug it in' equipment.

You can't have R&D hangups and build a SSTP spaceplane in 8 years.



tomcat

.

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