Could something like this actually work?

Saw an article today about an aircraft that would change it's buoyancy, so
it would float up like a balloon and then change buoyancy and glide down.
Interesting stuff, although I doubt we'll see it anytime soon. Is something
like this even practical? The article says they take the aircraft up 10
miles to get 400 miles range, I would think ATC wouldn't like the idea of a
free balloon (which is what it would be at that point) up in the flight
levels.

http://www.machinedesign.com/ASP/vie...PACE&catId=379

--
Louis Perley III
N46000 - KBJC

"Louis L. Perley III" wrote in message
...
Saw an article today about an aircraft that would change it's buoyancy, so
it would float up like a balloon and then change buoyancy and glide down.

From the article: "The aircraft, still in development, will be similar to a
submarine that changes its buoyancy, a form of gravity, to float on the
surface of the sea or cruise 300 ft below it. "

Since when is "buoyancy" a form of gravity? Since when does gravity have
more than one form usually known as, umm, gravity?

Cool idea, though.

--
Jim Fisher

"Louis L. Perley III" wrote:

Saw an article today about an aircraft that would change it's buoyancy, so
it would float up like a balloon and then change buoyancy and glide down.
Interesting stuff, although I doubt we'll see it anytime soon. Is something
like this even practical?

A similar technique that's been around quite a while is an internal air bladder
for LTA craft that use helium and hydrogen. Pump the bladder full of air, and
the buoyancy of the craft changes.

George Patterson
A diplomat is a person who can tell you to go to hell in such a way that
you look forward to the trip.

"Louis L. Perley III" wrote in
:

Saw an article today about an aircraft that would change it's
buoyancy, so it would float up like a balloon and then change buoyancy
and glide down. Interesting stuff, although I doubt we'll see it
anytime soon. Is something like this even practical? The article says
they take the aircraft up 10 miles to get 400 miles range,

In theory, yes. In practice, probably not. G It's called a blimp...

One of the things that limits your aircrafts speed (or range - somewhat
interchangable for this discussion) is induced drag. That comes from
using part of the aircraft's power to create lift instead of forward
thrust. If we reduce the weight of an aircraft (keeping everything else
identical) then we can now lower the angle of attack and maintain level
flight at a much lower power setting (or higher speed at the higher powr
setting).

Nothing new here... You can see it in any C-172 that's either light, or
at gross.

So now we seal off part of the plane and replace the air in there with,
well, nothing would be best. We reduce the weight of the plane by the
weight of the air that we pumped out. We can go faster and/or farther
on less.

Now the problem... First off, we lost part of the volumetric capacity of
the aircraft. Second, we played great games with the CG. Third, by
having to seal the area, we increased the "empty" weight some (even if
we maintain 1 atmosphere by pumping back in helium). Fourth, we got
only minimal improvements... maybe a few pounds savings.

That last is the big problem. If we want REAL weight savings we have to
increase the volume. That's called a blimp, and to get useful weight
savings it must be BIG BIG BIG. Now we have a Bonanza that weighs 100
pounds ... but it's 400 feet long and 100 feet across. And NOW we have
to add back in the parasitic drag that all this increased wetted area
generates, and now we are down to 35 knots TAS at full power.


-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------------------------------------------

"James M. Knox" wrote in message
...
"Louis L. Perley III" wrote in
:


That last is the big problem. If we want REAL weight savings we have to
increase the volume. That's called a blimp, and to get useful weight
savings it must be BIG BIG BIG. Now we have a Bonanza that weighs 100
pounds ... but it's 400 feet long and 100 feet across. And NOW we have
to add back in the parasitic drag that all this increased wetted area
generates, and now we are down to 35 knots TAS at full power.

Since it is a glider, it does save the weight of fuel.

"Louis L. Perley III" wrote in message
...
Saw an article today about an aircraft that would change it's buoyancy, so
it would float up like a balloon and then change buoyancy and glide down.
Interesting stuff, although I doubt we'll see it anytime soon. Is
something
like this even practical? The article says they take the aircraft up 10
miles to get 400 miles range, I would think ATC wouldn't like the idea of
a
free balloon (which is what it would be at that point) up in the flight
levels.

It is not a free balloon. Even if it was, free balloons climb to very high
altitudes now. They are the favored means of transport for space aliens
visiting Roswell. :-)

Hmmm... a double-balloon balloon with wings. I wouldn't invest in
it/him.

the double balloon concept: it could have better control over roll but
it will expensive in terms of weight and drag. Extra fabric,
structural components, etc. Then again is added control needed? We've
been flying around in blimps/etc for a century without problems in
this area (to the best of my knowledge). And pitch shouldn't be an
issue, separate chambers inthe front/back of a -long- tube will fix
that.

Only 50% larger than a 747 to carry the same load? I'm using
preliminary specs from the imaginary CL160 program from the Zeppelin
company to extrapolate here. (but I consider Zeppelin a bit more
credible, the current company is making rigid airships now; can the
data be compared to the gravityplane is another matter) Anyways the
CL160 is supposed to be 250m x 65m x 82m in length with a payload of
160 tons. The 747 is 70 meters long and has a load of 125 tons. So
then the gravplane needs to be roughly 3x the length.

I wonder how the inventor got the 4x improvement numbers over existing
wind turbines. Some data along with the claims would be nice.

Overall the general concept is sound, we all know it could work.
There's nothing cutting edge about this and current algorithims and
models will work- so why does he need to prove the idea in the ocean?
Submarines have diveplanes. Why the glider tests? We already have
gliders and balloons. To me he seems like a crackpot inventor just
wanting to play. If he was serious why not break out the engineers to
see what is feasible technically abd draw up some real plans, and then
bust out the finance types to see if it is worth doing?

my .02

-lance smith





"Louis L. Perley III" wrote in message ...
Saw an article today about an aircraft that would change it's buoyancy, so
it would float up like a balloon and then change buoyancy and glide down.
Interesting stuff, although I doubt we'll see it anytime soon. Is something
like this even practical? The article says they take the aircraft up 10
miles to get 400 miles range, I would think ATC wouldn't like the idea of a
free balloon (which is what it would be at that point) up in the flight
levels.

http://www.machinedesign.com/ASP/vie...PACE&catId=379

Since when are Journalists actually responsible for articulating facts
accurately?

"Jim Fisher" wrote in
:

"Louis L. Perley III" wrote in message
...
Saw an article today about an aircraft that would change it's
buoyancy, so it would float up like a balloon and then change buoyancy
and glide down.

From the article: "The aircraft, still in development, will be similar
to a submarine that changes its buoyancy, a form of gravity, to float
on the surface of the sea or cruise 300 ft below it. "

Since when is "buoyancy" a form of gravity? Since when does gravity
have more than one form usually known as, umm, gravity?

Cool idea, though.

--
Jim Fisher

"C J Campbell" wrote in
:

Since it is a glider, it does save the weight of fuel.

Didn't notice the "and glide down" part until you pointed it out. Okay...
so change the above to reflect an aircraft with an engine of 1G thrust
rating. G

-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------------------------------------------

"Louis L. Perley III" wrote in message
...
Saw an article today about an aircraft that would change it's buoyancy, so
it would float up like a balloon and then change buoyancy and glide down.
Interesting stuff, although I doubt we'll see it anytime soon. Is
something
like this even practical? The article says they take the aircraft up 10
miles to get 400 miles range, I would think ATC wouldn't like the idea of
a
free balloon (which is what it would be at that point) up in the flight
levels.


http://www.machinedesign.com/ASP/vie...PACE&catId=379



1) I wonder why a typical blimp has to use such a large volume (the ballon)
to provide the lift and a relatively tiny cabin attached underneath, whereas
this craft seems to use a much smaller volume (the wings). Has the inventor
calculated this correctly?

2) Where is the power source? Conservation of energy says that the plane
could not continue to ascend and descend without some input of energy. The
initial ascent would be powered by the energy required to separate helium
from the atmosphere, which is accomplished on the ground, but it should not
be true that the plane would "always land with its tanks fully pressurized",
since theoretically the amount of energy generated by the turbines during
the descent could not be enough to compress the gas used for the ascent.
Esecially if the efficiency of the turbines is 20%.

On the other hand I still think that Boeing 747s get off the ground by some
sort of magic. There is no way such a huge vehicle could be lifted by thin
air.