Previously on rec.arts.sf.tv.babylon5.moderated, Chris Adams said:

> >That is merely a question of engineering, not science.  We HAVE the
> >technology, just not the will due to cost.  I'd bet that any of us here
> >could sketch out the basic design criteria of such a craft and with the
> >proper engineering to make it real, it would work.  It might cost a
> >couple billion dollars at first and be the size of a 747 or C5, but it
> >would work.
> 
> Go ahead, I'll wait.  How is it looking?

I'm not an engineer, I never claimed to be.  I can't build the thing.

> We really don't have the technology to do that.  We really can't make
> the vehicle much lighter (and still be able to carry anything) due to
> the limits of materials.  For example, the X-33 test vehicle was going
> to use carbon-fiber composite fuel tanks, but they didn't work out.
> Liquid hydrogen is a hard thing to hold; it blew the sides off of the
> tank in a test.  The SSME (Space Shuttle Main Engine) is already the
> highest performing rocket engine ever built, and it can't come anywhere
> near handling a horizontal takeoff.

That's why it would have multiple engine types.  From what little I do
know, I understand that rockets are not the most efficient for
in-atmosphere use.  Ideally, it would have three sets of engines, each
for a different stage of the flight:

1: Jets for lower atmosphere flight
2: RAM or SCRAM Jets for upper atmosphere flight
3: Rockets for use in the vacuum

If the three sets turns out to be not feasible, then scrap the second
set and use just jets and rockets.

> The amount of energy required to get to low Earth orbit is massive when
> compared with air flight.  The top speed of a 747 is 567 mph; Shuttle
> orbital velocity is about 17,500 mph.

Use jet engines for horizontal lift-off and flight up to the upper
atmosphere, and then light off the rockets for the push into orbit.

Or, if you are really strapped for weight, then make it a dual-stage
craft, which I believe is the direction Virgin Galactic is going: a jet
powered atmospheric flight first stage with the orbiter second stage
piggy-backing.  First stage returns under power to the launch site and
the orbiter continues up under rocket power, and later returns on a
glide path.

> Besides, "just throw money at it" doesn't really make much sense.  If
> you can spend a fraction of the price on a one- (or few-) use capsule
> and a throw-away rocket, why spend much much more on the magic
> spaceplane, other than to fulfill science-fiction dreams?

Because it is, or can be, bigger.  Economics of scale, etc.  Sure, a
747 costs lots more than a Piper Cub, but the 747 can carry
significantly more.  Assuming a full load, this makes the per-pound
lift more economical and thus more viable.

The spaceplane concept would allow for larger scale commercial use of
and travel to/from orbit.

> >I just think that NASA is taking a giant step backwards with their
> >current plans on the eventual replacement of the Shuttle.  We SHOULD be
> >using self-contained and fully reusable spaceplanes by now to get to
> >and from orbit.
> 
> That kind of thinking got us the Shuttle, which really proved that even
> vertical takeoff and horizontal landing wasn't that great of an idea.
> You might could improve on the safety by having a first stage entirely
> below the vehicle, but you'd end up with an impossibly tall stack.
> 
> Reusable didn't work out that well either.  The stresses on the vehicle
> were pushing the limits, so a lot of inspection and refurbishment was
> required between every flight (the SSMEs were essentially rebuilt every
> time).

Yeah, the turn-around time was supposed to be a couple of weeks, not
months.

As I recall, there was a hell of a lot of changes made to the original
shuttle design because NASA was in a rush and didn't want to wait for
what was originally planned, which was supposed to be better than what
we eventually got.  Just because we got a bad version doesn't mean that
the concept is bad, it just means that we got a bad implementation of
the concept.

-- 
Jeffrey Kaplan                                         www.gordol.org
Double ROT13 encoded for your protection

"On the other hand, maybe wounding him isn't such a bad idea after
all."  (Dr. Franklin, B5 "Dust To Dust")
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