Aeroscraft shows off its giant airship

in space on 2015-10-12 07:40 (#Q6XQ)

Lighter than air vehicles are, for the most part, relics of a distant past. Despite the past century of flight mostly belonging to airplanes and helicopters, there's been a slight resurgence of dirigibles this century. Not least among them is the Dragon Dream, by the Aeroscraft Corporation. This is only half the size of their planned airship...

Rather than the slow-moving luxury cruisers of old, the Aeroscraft is a working vehicle designed to carry 66 tons of cargo reliably to parts of the world without runways. The 555-foot-long craft is at a design freeze. Aeroscraft thinks they have the vehicle they want, and to meet deadlines on time, they're going to stop tinkering with the design and just make the dang thing.

The Aeroscraft is just one of a small new world of gigantic lumbering dirigibles. In 2013, the U.S. Army canceled its LEMV surveillance zeppelin, but the project has since been revived in the United Kingdom as a working machine, and Goodyear is looking at replacing its soft-bodied blimps with more durable rigid airframes.

What giant airship (Score: 1)

by fnj@pipedot.org on 2015-10-12 21:00 (#Q954)

There is no giant airship to show off. It is an idea; nothing more.

The Dragon Dream was strictly a demonstrator, capable of no payload whatsoever. It mever flew. Not once. It made a very timid tethered float like a kid's balloon on a string. Basically they proved that, yes, helium weighs less than air, yes, you can lift things with it, and yes, you can compress and expand it. All that has been well-known for a century. The roof of their decrepit hangar fell in and wrecked it, and they scrapped it, since there was nothing to be gained from it.

Question. Has the hangar roof been surveyed, repaired, and proofed yet? Are they sure they won't overstran it again by hanging heavy weights from it?

I doubt VERY much that they have actual funding to build the full-size model. They might POSSIBLY have enough to crank out another, larger demonstrator.

Could you use hydrogen for permanent-installation balloons? (Score: 1)

by wootery@pipedot.org on 2015-10-13 15:02 (#QBMZ)

As I understand it, the high price of helium is one of the major issues with airships. Could you use (yes, flammable) hydrogen instead, especially for unmanned floating-installation type applications?

If you want to bounce radio signals off something a mile up in the sky, would a hydrogen-filled balloon do the job? The safety issue is surely not a big one if it's not designed to regularly land: a Hindenburg situation seems unlikely if it's neither carrying people nor intended to land.

Re: Could you use hydrogen for permanent-installation balloons? (Score: 1)

by evilviper@pipedot.org on 2015-10-13 18:14 (#QC9W)

Actually, natural gas is cheap, highly buoyant, and not as escape prone as helium or hydrogen... Still highly flammable, and could be used to run the engines as well.

Re: Could you use hydrogen for permanent-installation balloons? (Score: 3, Informative)

by fnj@pipedot.org on 2015-10-13 23:09 (#QD37)

If Hindenburg were filled with natural gas instead of hydrogen, she couldn't have lifted her empty weight off the ground with zero payload and fuel. The following figures are based on very favorable conditions for static lift. More realistic conditions (say 15-25 C, and just 300 m MSL initial cruise altitude) would lower them significantly

Gas capacity = 202 000 m^3
Air density at 0 C, 101 325 Pa = 1.292 kg/m^3
Hydrogen density at 0 C, 101 325 Pa = 0.090 kg/m^3
Hydrogen lift at 0 C, 101 325 Pa = 1.292 - 0.090 = 1.202 kg/m^3
Gross lift 100% filled with hydrogen = 202 000 x 1.202 = 242 800 kg
Methane density at 0 C, 101 325 Pa = 0.716 kg/m^3
Methane lift at 0 C, 101 325 Pa = 1.292 - 0.716 = 0.559 kg
Gross lift 100% filled with methane = 202 000 x 0.559 = 112 900 kg
Weight empty = 118 000 kg

If she had been designed from the ground up for methane, restressed for the lower weights, de-engined for a slower speed (less aerodynamic stress) and carrying fewer passengers, it probably would have been possible to get a ship capable of lifting perhaps (optimistically) 1/4 as much useful lift. Still-air range would have been around 2000 km instead of 12 000 km (usable range with reserves considerably less).

Re: Could you use hydrogen for permanent-installation balloons? (Score: 1)

by fnj@pipedot.org on 2015-10-13 23:19 (#QD45)

The cost of helium is not a critical factor. Even at a very generous $10/m^3, the cost to fill Hindenburg 100% with helium would be $2 million. But it would cost at least $45 million (simply tracking general inflation), and quite possible $100-200 million to build Hindenburg today. Operations are such as not to expend any gas. Diffusion and leakage could certainly be kept to less than the amount of one filling per year.

But yes, certainly hydrogen could technically be used if you could get your craft certified with it, and if you don't mind the hazard of flaming wreckage falling on your citizens.

Re: Could you use hydrogen for permanent-installation balloons? (Score: 1)

by wootery@pipedot.org on 2015-10-14 22:13 (#QGKS)

and if you don't mind the hazard of flaming wreckage falling on your citizens.

Ah yes. That.

Could a balloon be engineered to 'fail safe'... like a self-destruct? If it burns up quickly in case of fire and carries only a light payload (some kind of radio repeater), I imagine the risk could be mitigated. I guess there's always the vulnerability to vandalism though.

Not the first and probably not the last attempt to achieve something like that... CargoLifter (Score: 1)

by tanuki64@pipedot.org on 2015-10-13 18:20 (#QCAQ)

https://en.wikipedia.org/wiki/CargoLifter

At least something useful was done with the hangar after they bankrupted.

More luck to Aeroscraft.