Airship-to-Orbit?

nafod40 wrote in message ...
When I read the article, what I saw was that they wanted to glide the
airship upwards and have it accelerate as it rose, using the positive
buoyancy as it's source of thrust. So it'd be an upside-down glider.
They were proposing to gain much of the airship's escape velocity that way.

My understanding is that when they mean electric propulsion, they're
not talking about an electric motor. They mean an electric
ion-thruster, which expels charged ions straight out at very high
velocity. Electric ion-thrusters are supposed to be 5 times as
efficient as chemical combustion rocket engines, propellant-wise, and
they are powered by electricity which a blimp could gather thru solar
energy. But they need to operate in a vacuum or near-vacuum
environment, which is why it might make sense with an airship that is
up where the air is very thin. The problem is that the thrust from an
ion-engine is very low, like a small puff from your lungs, so it can't
really move a big object like a blimp. But ion-engines are very
long-lasting (can operate for tens of thousands of hours before
wearing out) compared to chemical rocket engines. But who wants to
take so long to get to orbit???


There are other types of electric thrusters which can produce more
thrust, such as the VASIMR, they'd need megawatts of power like from a
nuclear reactor. Could the surface area of a blimp gather that much
solar energy?

I would think hydrogen would be an obvious choice. Helium molecules are so darn
small that they leak out of practically anything. That is why the coated mylar
party balloons are used instead of latex.

Hydrogen likes to be H2 which is huge compard to a single helium, and lighter
yet stronger materials can be used to hold it.

-- Charlie Springer

(Wright1902Glider) wrote:

Um,

What happens to the gas bag once it makes orbit? Am I correct in assuming
that
there will be a serious pressure differential between the interior and
exterior
of the bag? I'm thinking "World's Largest Baloon Goes POP!" ?????

Ask yourself, what is the difference between almost a vacuum and a vacuum? Not
much. If it will hold 16 lbs/sq in, that is about all you need. Things like
people only blow up in vacuum in fiction. If they did, then immagine what would
happen to a SCUBA diver as they come up through three atmospheres of pressure
change!

BTW, Echo 1 was one of the first US sats and it was a metal film coated balloon
to bounce communications.

-- Charlie Springer

On 28 May 2004 03:11:03 GMT, (Regnirps) wrote:

(Wright1902Glider) wrote:
:
:Um,
:
:What happens to the gas bag once it makes orbit? Am I correct in assuming
:that
:there will be a serious pressure differential between the interior and
:exterior
:of the bag? I'm thinking "World's Largest Baloon Goes POP!" ?????
:
:Ask yourself, what is the difference between almost a vacuum and a vacuum? Not
:much. If it will hold 16 lbs/sq in, that is about all you need. Things like
eople only blow up in vacuum in fiction. If they did, then immagine what would
:happen to a SCUBA diver as they come up through three atmospheres of pressure
:change!

If it's filled with pure O2, 3 or 4 psi will do it, that's what Apollo
used.

Not that I believe the rest of it, mind you.

The pictures look fake to me. I also get real leary when they ask for donations.

Brett

"Regnirps" wrote in message
...
I would think hydrogen would be an obvious choice. Helium molecules are so
darn
small that they leak out of practically anything. That is why the coated
mylar
party balloons are used instead of latex.

I have never noticed that helium filled latex balloons lose buoyancy any
faster than the Mylar ones. I thought Mylar was used because it is bright
and shiny. I have also heard that birds are less likely to eat it and die,
which probably ranks right up there with urban legends about wedding rice
and birds. Back in the old days (when I was a child) I used to sell balloons
to raise money for Rotary and the local rodeo. No such thing as Mylar
balloons then, but they were filled with helium. The balloons would hold
their helium for a week or more. I also recall latex weather balloons filled
with helium. Although I personally launched literally thousands of toy
balloons filled with helium, I never heard of a bird being killed by one. I
have seen toy helium filled balloons at 11,000 feet.

When we lived in the Philippines in the 70's they still sold balloons filled
with hydrogen, which has been banned in the US because of its flammability.
Let one of these toys near a lit cigarette and you could have one badly
burned kid.

"C J Campbell"

I have never noticed that helium filled latex balloons lose buoyancy any
faster than the Mylar ones.

A regular ballon is usually limp in less than 24 hours and useless shortly
after that. The Maylars are good for about a week I think. I either case, I
wonder how much is escaping through the knot or filler adhesive?

-- Charlie Sprinher

A regular ballon is usually limp in less than 24 hours and useless shortly
after that. The Maylars are good for about a week I think.

I've had a 12" (30cm) Mylar balloon hold its lift for over a month.

I either case, I
wonder how much is escaping through the knot or filler adhesive?

Sometimes a plastic plug is used in He-filled rubber balloons. Might that work
longer?

(G EddieA95) wrote:

Sometimes a plastic plug is used in He-filled rubber balloons. Might that
work
longer?

It might help a little, but the helium is diffusing right through the rubber.
The stuff is notorious. Many a physics graduate student has spent years chasing
down helium leaks in high vacuum and cryogenic equipment.

-- Charlie Springer

On 29 May 2004 02:58:52 GMT, (Regnirps) wrote:

(G EddieA95) wrote:

Sometimes a plastic plug is used in He-filled rubber balloons. Might that
work longer?

It might help a little, but the helium is diffusing right through the rubber.
The stuff is notorious. Many a physics graduate student has spent years chasing
down helium leaks in high vacuum and cryogenic equipment.

Back when I was just a young engineer, the test organization I was in did
leak testing for the fuel tanks for the first Air-Launched Cruise Missiles
(ALCMs). Said tanks were pressurized with helium, with a sniffer to chase
down the leaks.

Ron Wanttaja