Hybrid Airships Options

[Stahlseele]

Would it be possible (with SR composite materials tech) to use a bunch of rigid plastic tanks that are simply sucked vacuum in order to achieve liftoff? To reduce lift, simply fill some of them with air again..

*blink blink*
wait what?
you want something that flies because you take something out of there? O.o

[Ascalaphus]

A large vacuum in a lightweight container would be buoyant, right? It's even lighter-than-air than helium.

[hobgoblin]

given that i have seen a video demo of a steel thermos get crushed by simply having the air cooked out of it, good luck with that.

variant on the theme:
http://www.youtube.com/watch?v=5fX9C_K58C0

[Ascalaphus]

Yes, but there's a big difference between built for vacuum and not built for vacuum.

[Draco18s]

"Built for vacuum" tends to be "heavy."

[Ascalaphus]

"Built for vacuum" tends to be "heavy."

I guess that depends on what kind of Future Tech new materials get developed in SR. Given the amount of surface-orbit traffic, there should be a market for ultra-strong light materials.

[hobgoblin]

most of that traffic comes from going with a railgun rather then chemical rockets for most of the bulk cargo.

[hobgoblin]

btw, i found this:
https://secure.wikimedia.org/wikipedia/en/w..._vessel#Scaling

anyone up for some math?

[Method]

ewww! You got physics in my RPG! Gross! (IMG:style_emoticons/default/biggrin.gif)

[kigmatzomat]

btw, i found this:
https://secure.wikimedia.org/wikipedia/en/w..._vessel#Scaling

anyone up for some math?

Let's start with the simple balloon ball.

M = 1.5 Pressure * Volume * density of material / max stress of material

Assuming we have total vacuum, that gives us a pressure of 101k Pascal
Volume, let's use 1 hindenburg : ~200,000 m^3

So let's try a carbon-nanotube assembly, being the strongest, lightest material I can think of. They have a density of 0.55g/cm^3 => 550kg/m^3. Nanotubes appear to have 150G Pascals of compressive strength, per some quick google-fu.

M = 1.5 * 0.1 G Pa * 200,000 m^3 * 550kg/m^3 / 150G Pa = 110,000 kg

The displaced mass is 200,000m^3 x the density of air (1.2Kg/m^3) = 240,000kg.

Total gain: 130,000 kg that can be used for drive system, fuel, control systems, gondola, cargo, and crew. Considering that's enough mass capacity for 2 M1 Abrams tanks, I think that can be done.

The hydrogen-lifted hindenburg had a total capacity of ~250,000 kg (the bags were slightly larger than the nice, round 200k m^3 volume I used) and the craft massed 215,000 kg when fueled.


We can use the bullet-shaped vessel formula to get the classic cigar-shaped blimp. We'll use the dimensions of the hindenburg, 20m radius and 220m of cylindrical body for a total length of 240m.

M = 2 pi R^2 (R+W) * pressure /density
M = 2 * 3.14 * 20^2 * (20+220) * 0.1 Gpa * 550kg/m^3 / 150G Pa = 221,000 kg

This would have the same displaced mass of 240,000 kg, giving us 40,000kg gain for drive, fuel, controls, gondola, etc. That's quite a bit less than the Hindenburg.

[Fix-it]

good math there, however, we seem to be re-inventing a square wheel. perhaps materials science will improve enough one day.

I also dug up this interesting article with only a 7% advantage in lifting power over hydrogen, vacuum looks pretty terrible.

a thought occurs that you could use hydrogen for lifting gas, and as power for your turbines.

[CanRay]

a thought occurs that you could use hydrogen for lifting gas, and as power for your turbines.

On the bright side, people are used to not smoking on flights now...

[hobgoblin]

so perhaps it will work after all.

hmm, now i got the mental vision of 4 nanotube spheres linked via scaffolding and a single lifting/container rig in the center.

[Draco18s]

I also dug up this interesting article with only a 7% advantage in lifting power over hydrogen, vacuum looks pretty terrible.

It's 7.5% (100/93, not 100-93), but close enough.

The problem is maintaining the same craft-weight to support your "vacuum balloon" (i.e keep it from being crushed by the atmosphere).