A Question on the Nature of LTA craft

[Moonstone Spider]

A Blimp gains it's density from a baloonet inside a balloon, the Balloonet is filled with air and you can pump air in and out of it. As you pump in air, it becomes denser and the Zeppelin sinks, pump air out and density drops and it falls.

Here's the question, where is the potential energy for the Airship coming from? Obviously if 2,000 tons of steel and hydrogen just rose up a thousand feet in the air it has vastly more potential energy than before, but I don't see where the energy going into that came from.

[Sea Skimmer]

A Blimp gains it's density from a baloonet inside a balloon, the Balloonet is filled with air and you can pump air in and out of it. As you pump in air, it becomes denser and the Zeppelin sinks, pump air out and density drops and it falls.

Here's the question, where is the potential energy for the Airship coming from? Obviously if 2,000 tons of steel and hydrogen just rose up a thousand feet in the air it has vastly more potential energy than before, but I don't see where the energy going into that came from.

The energy would be coming from the atmosphere. As the gasbags expand, they displace more and more air, which then pushes back, providing the lift and energy.

At least that’s how I understand it.

[Nick]

The energy would be coming from the atmosphere. As the gasbags expand, they displace more and more air, which then pushes back, providing the lift and energy.

At least that’s how I understand it.

Ah, I just figured out how the energy balance actually works: the net change in GPE is ZERO.

Think about it: the airship is displacing a volume of air with equal mass. So, as the airship changes height, it is replaced by air at its previous height. The GPE of the airship has increased, but the GPE of an equivalent amount of air has decreased.

Cool, I'd never thought about that:> Neat question Moonstone!

[Moonstone Spider]

Thanks for the info, I never considered that some air lost GPE. I've been going nuts for the past 3 days trying to figure this question out myself.

[Moonstone Spider]

Hmm, thinking on this, would it be possible to make a pseudo-perpetual motion machine off of bouyancy? The power to pump the air in and out of the Balloonet is probably less than it a blimp rising and falling turned a turbine. . . interesting thought. Probably impractical though.

[RayCav of ASVS]

A Blimp gains it's density from a baloonet inside a balloon, the Balloonet is filled with air and you can pump air in and out of it. As you pump in air, it becomes denser and the Zeppelin sinks, pump air out and density drops and it falls.

Here's the question, where is the potential energy for the Airship coming from? Obviously if 2,000 tons of steel and hydrogen just rose up a thousand feet in the air it has vastly more potential energy than before, but I don't see where the energy going into that came from.

The energy would be coming from the atmosphere. As the gasbags expand, they displace more and more air, which then pushes back, providing the lift and energy.

At least that’s how I understand it.

Sounds simple and logical enough.

[RayCav of ASVS]

Hmm, thinking on this, would it be possible to make a pseudo-perpetual motion machine off of bouyancy? The power to pump the air in and out of the Balloonet is probably less than it a blimp rising and falling turned a turbine. . . interesting thought. Probably impractical though.

If nothing else, Entropy will eventually have its way with it. All the laws of Thermodynamics tie in to make perpetual motion machines impossible.

[Mr Bean]

Remeber that classic joke about PM machines?

So hows the Preptual Motion machine coming?
Not good but I can't seem to stop trying