Zeppelin: Highest Altitude + Restrictions

[FiggyOO]

Does anyone happen to know the highest a zepplin has gone, and what the theoretical max it could reach? What would be the restrictions that would keep it from reaching a higher altitude?

 

[ray b]

a zepplin [ dirigible ] has an internal frame and POWER ?
and I have never heard of a pressurized one so they stayed fairly low
a free balloon without such heavy bits can and has gone far higher
about 113,000ft manned is the current record with unmanned going up about 140,000
for free balloons

 

[FiggyOO]

If the cabin of the dirigible were to be pressurized, how high do you think it might be possible for it to float up?

 

[russ_watters]

Pressurization of the cabin is irrelevant to the question. The fact that it has structure makes a zeppelin heavier than a balloon, which restricts its altitude.

A quick google shows that the record is 7600m (25,000 ft).

http://en.wikipedia.org/wiki/List_of_Zeppelins

 

[FiggyOO]

I'm still just saying theoretically though, how high could it go.

 

[russ_watters]

Not much higher than the record.

 

[mgb_phys]

In practical terms it's limited by the mass of the structure - but theoretically as the mass of the structure goes to zero, or you make one so big that the mass of the structure is negligible.

 

[jaap de vries]

Not much higher than the record.

 

[ray b]

I'm still just saying theoretically though, how high could it go.

modern materials like carbon fiber and mylar could make a lot lighter structure
then old pre-war german teck
so I would guess about 100,000 feet max and not cheap or eazy to do
why anyone would want to go that high or for what reason I have no clue

 

[montoyas7940]

a zepplin [ dirigible ] has an internal frame and POWER ?

Use big rocket engines and point them straight down. You could go as high as you want.
You might really wish for that pressurized cabin though.

 

[FiggyOO]

Well, I was thinking because they can lift ~50 tonnes or more, and so if you had no cargo, and a small pressurized cabin then I would hope it would be possible to even higher up than 100,000 feet.

 

[montoyas7940]

The problem is the buoyant force is provided by the atmosphere. About half of the atmosphere is below 20,000 ft. So as you go higher you will quickly run out of buoyancy.

Edit: half by weight, that is.

 

[Mech_Engineer]

Well, I was thinking because they can lift ~50 tonnes or more, and so if you had no cargo, and a small pressurized cabin then I would hope it would be possible to even higher up than 100,000 feet.

You wouldn't be able to lift 50 tons to 100,000 ft with any zeppelin of a standard size, the amount of atmosphere required to be displaced would be incredible; basically, the heavier the vehicle, the lower the max altitude available. Heavy-lift lighter than air ships need to stay low in the atmosphere where the air is nice and dense and you don't have to displace too much fluid.

Think about it, to lift 50 tons at sea level, you have to displace about 37,000 m^3 of air (not including the weight of the ship itself.) To lift 50 tons at 100,000 ft, you have to displace 72 times that, 2.66 milllion cubic meters of atmosphere.

 

[FiggyOO]

What would happen, if you could somehow launch a space worthy rocket from an LTA at an altitude higher than max Q? How much more efficient, etc would it be to have V naught at an altitude where max Q is?

 

[montoyas7940]

FiggyOO, you mean like Spaceship One and White Knight? If you launch from a greater altitude you would simply have a new max Q that occurs at a higher altitude. It is more efficient however.

 

[FiggyOO]

Sure. I guess that would work.

Anyone got a direction to point for me to do some calculations with differing altitudes and stuff for max Q etc?

 

[russ_watters]

It is more efficient, but not much more efficient. Max Q occurs relatively early in the flight and the shuttle isn't going very fast at max Q (only about 1/10th orbital speed).

 

[Mech_Engineer]

What would happen, if you could somehow launch a space worthy rocket from an LTA at an altitude higher than max Q? How much more efficient, etc would it be to have V naught at an altitude where max Q is?

FiggyOO, you mean like Spaceship One and White Knight? If you launch from a greater altitude you would simply have a new max Q that occurs at a higher altitude. It is more efficient however.

It has been pointed out many times in several topics on this forum that it isn't height that gets you into orbit, its velocity. Launching a spaceship from 100k feet up adds about 0.261 MJ/kg of potetial specific energy, however about 30 MJ/kg of kinetic energy is required for orbit at 261km.

 

[montoyas7940]

It has been pointed out many times in several topics on this forum that it isn't height that gets you into orbit, its velocity. Launching a spaceship from 100k feet up adds about 0.261 MJ/kg of potetial specific energy, however about 30 MJ/kg of kinetic energy is required for orbit at 261km.

Yeah, good point. Spaceship One is a strictly suborbital space worthy craft.

 

[montoyas7940]

What about it FiggyOO, are you just looking for as much altitude as possible? Or do you want a free fall orbit. We might to have to find you a tall mountain on the equator.