Space pier

Joe Strout wrote:
Holding up a launcher from balloons would take a lot of very tall
balloons, but it still sounds a lot easier to me than building a
mountain that big.

You are probably right.

But in my old-fashioned habits of mind, I think of a mountain as
something permanent, while balloons are temporary things that will keep
having to be replaced.

The exit from any kind of mass driver would have to be horizontal
rather than vertical. So it would seem to have to be high enough so
that this would not have a greater penalty than the benefits of using a
mass driver instead of a rocket booster. Even just saving the first
stage of a two-stage rocket would greatly reduce the costs of going
into space.

I see that the peak of Mount Everest is 29,028 feet above sea level,
and there the atmospheric pressure is roughly a third of what it is
normally.

Airplanes typically fly at 33,000 feet. But it doesn't seem to be
useful to make an airplane the first stage of a rocket, since the
problem with a rocket is gaining momentum, not altitude. Altitude is
useful as a way to get above air resistance, to make it easier to gain
momentum: but the small improvement would not justify the effort of
flying a rocket up to that altitude to ignite it there.

Balloons used to go to much higher altitudes than airplanes could
reach, thus there was the fear Germany would use them to bomb Britain
during World War I. Could a tethered-balloon elevator take rockets up
to 50,000 feet for launching?

I fear such an idea would also be impractical and unsafe, although at
least it requires less resources than an artificial mountain five times
as high as Everest.

John Savard

In article .com,
wrote:

Balloons used to go to much higher altitudes than airplanes could
reach, thus there was the fear Germany would use them to bomb Britain
during World War I. Could a tethered-balloon elevator take rockets up
to 50,000 feet for launching?

Easily. 50,000 feet is about 15 km. Even amateurs have sent balloons
as high as 35 km:
http://www.universetoday.com/am/publish/satellites_budget.html

And note that I'm not proposing, in this case, simply launching a rocket
from a stationary balloon platform. Rather, I'm saying: let's make a
launch pier (i.e. a high-altitude catapult system), but suspend it from
balloons instead of supporting it from ridiculously tall towers.

Note that the link above gives you a good idea of how ridiculous those
towers would need to be -- consider that the photo there was taken from
only 35 km up; Hall is proposing compression structures three times
taller than that! Not to say that it can't be done someday... but I'd
believe balloon suspension far more readily in the near term.

I fear such an idea would also be impractical and unsafe, although at
least it requires less resources than an artificial mountain five times
as high as Everest.

Right. It's certainly a bit of a Rube Goldberg solution, as so many
innovative launch ideas are. It couldn't possibly pay for itself unless
the launch rate were very high -- but then, with a very high launch
rate, rockets would be a lot cheaper too, and substantially more
flexible.

Note that our own Mike Combs wrote a science fiction book, based on
essentially this same concept, in 1995. It's available he
http://members.aol.com/howiecombs/bridge.htm

It's a good read, and even if some of the technical details may not
stand up to careful scrutiny, I think the basic idea is sound.

Best,
- Joe

on Thu, 11 Jan 2007 08:33:05 -0700, Joe Strout sez:
In article .com,
wrote:

Balloons used to go to much higher altitudes than airplanes could
reach, thus there was the fear Germany would use them to bomb Britain
during World War I. Could a tethered-balloon elevator take rockets up
to 50,000 feet for launching?

Easily. 50,000 feet is about 15 km. Even amateurs have sent balloons
as high as 35 km:
http://www.universetoday.com/am/publish/satellites_budget.html

And note that I'm not proposing, in this case, simply launching a rocket
from a stationary balloon platform. Rather, I'm saying: let's make a
launch pier (i.e. a high-altitude catapult system), but suspend it from
balloons instead of supporting it from ridiculously tall towers.

OK, how's this for a vision of Mookian proportion (Bill, I use that
term in only the best good humour): you pick yourself the optimum
altiplana, highest and closest to the equator, and you clear
flat fields about a mile or so across, with three or four large
elevated, reinforced deep anchor points around the perimeter. Then
you start stacking whacking great airbags, like english muffins,
each heated to give a slight positive buoyancy relative to
the surrounding air. The bags are tethered to the anchor points,
and to each other, and they decrease in size somewhat as you go up.
(I am guessing that the "cellular" construction will minimize
the internal weather issues, plus it will provide a series
of platforms for the heaters, and I guess some form of internal
cable elevator series.)

The technology to do this sort of thing exists, to some degree:
we have locally a stadium with a 200m diameter inflated teflon
fabric roof (please disregard that it popped a hole last week
and deflated after being in place 20 years - the hole should
be repaired in a few days and the mushroom reinflated).

This should get you a series of posts that combine a solid
ground anchor with balloon buoyancy. I have a vague memory
of this idea being kicked around here (or sst) some years ago...
Say you're starting from 5km up, you could get up to 20km
with a not-unreasonable aspect ratio, and if you wanted more
(up to what such buoyancy can get you) you could put out
more money for a bigger footprint - I assume that fighting
the jetstream is going to require something more robust than
a needle.

Note that the link above gives you a good idea of how ridiculous those
towers would need to be -- consider that the photo there was taken from
only 35 km up; Hall is proposing compression structures three times
taller than that! Not to say that it can't be done someday... but I'd
believe balloon suspension far more readily in the near term.

Heck, looking at those pics, it occurs to me with the balloon-piers,
you could build a resort on the top - if people are willing to
fork over money to be ballistically hurled to the top of the
atmosphere for a few seconds, surely they'd be happy to pay
a huge premium to dine at the ultimate rotating view restaurant.
Perhaps you could fund most of your launch costs that way (^:


--
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Pete Vincent
Disclaimer: all I know I learned from reading Usenet.