Wasting my time with these nutty notions of large scale peer networking, lighter-than-air-craft . . . Hay! what if, instead of compressing the He, they just liquified a bit of N2 into ballast tanks? Or is diatomic nitrogen to dangerous for humans?

... just like a huge, uncircumcised cock.

Is this some form of (almost literal) willy waving on the part of the US Defence megacorp?

Or some form of psyop against the Taliban?

"70 Virgins? NOT ENOUGH!"

The Pinky-Ponk (as mentioned before on the Register) appears to have a rigid shell. It also carries quite a few passengers considering its size. It gets around the buoyancy problem while unloading passengers by lowering a small spherical anchor to the ground.

Quite frankly I'm amazed DARPA have taken longer to perfect this technology than Iggle Piggle.

The Pinky-Ponk even has a nice balcony for Iggle Piggle and Upsy Daisy to go for a bonk (see episode "Tombliboo Ooo Drinks Everybody Else's Pinky Ponk Juice")

A really bad idea all over again? If the damn thing does not go really high, way out of reach for shoulder fired missiles. Then it might work.

Paris because she knows how to avoid getting hit

Get rather worried if lots of airships start appearing over London. Next thing you know the streets will be full of cybermen!

Mine's the one with the sonic screwdriver in the pocket.

"the famous Pentagon wackboffinry bureau known for its defiant reliance on the appliance of science to all military problems."

That would have cost you a new keyboard and screen and mouse IF I were drinking coffee

What does the second image on the second page remind you of?

maybe not for taking troops into a battle zone but still could be used for moving troops and gear around the US. could be easier to use the trucking them or putting them on railways. would like to see that can just imagine looking up and seeing that monster floating by...

And there was me thinking that was the name British Aerospace (as was) gave to the idea of plucking (Sea) Harriers out of the sky to save all that nasty hovering over the deck business...

http://www.servicepals.com/index.cfm/pcms/site.gallery.view_image/imageID/55130/

Do we not have a structure strong enough yet to make a vacuum ship? It seems to me that if they can evacuate the LHC, we should be able to make ships strong enough to survive 1 atmosphere negative pressure light enough that way.

i.e. you pump out the air to go up, you let it in to go down.

Or perhaps not a vacuum ship, perhaps a H2O ship. If we can't make it strong enough to survive 1 atmosphere, stick a little water in and make it a cold steam ship (h2O is 'lighter' than air).

I don't think this is insoluble, it's just that it's not very useful having a slot large ship that gets blow around easily when there was fuel for 600mph jets.

* a huge thin-skinned balloon full of flammable gas - as in a helium vessel

Um.... wot?

I feel confident that if the boffins at DARPA were given the "challenge" of producing a weapons system that could down an airship from long range, then they'd manage. You have a slow moving, bleedin' enormous target and all you have to do is slash it open with several thousand pieces of hypersonic shrapnel. I really can't see this being a safe way to transport stuff into a war zone.

Of course, for civilian purposes it makes a lot of sense and *that* surely is the point. The US aerospace industry are fed up with Airbus nicking their business, so they're pitching for a few billion dollars in R&D subsidy.

And as memory serves, apart from the obvious "Boom, there goes a whole lot of toffs, Oh the humanity" incident, there were never really that effective. Their only real use was to stick a whopping great swastika on one and tour the world, banging the war drums.

A simple solution, when using a rigid frame, is to inflate a balloon of air inside the buoyant enveloppe, which decreases the buoyancy by augmenting the density of the helium through simple pressurization. This is the typical solution used on modern airships.

There is another problem than buoyancy with airships, though, it is that of maximum velocity against lifting capacity. Lifting heavy loads requires lots of volume, and lots of volume mean big dynamic drag that reduces top speed. One solution was to use a dynamically-lifting shape for the buoyant enveloppe, as for the Dynalifter and its ancestors. But then it just comes down to trading maximum hovering altitude against top speed.

A solution to this problem is to use a variable-volume dynamically-lifting shape for the enveloppe. As the speed increases the volume can be decreased (pressurizing the lifting gas) and boyant lift exchanged for dynamic lift, saving on dynamic drag, when taking off the enveloppe can be expanded up to the ambient pressure, and when offloading cargo the enveloppe can be repressurized again to lose buoyancy and stay on the ground.

But there is currently no engineering method for building a volume-changing aerodynamic enveloppe that can self-pressurize like this.

About to be unrolled

One way to practise safe flying I spose.

Is it me, or does that first 'Aeroscraft' picture look suspiciously like Thunderbird 2?

"H2O is lighter than air"... "Cold Steam"

Cold steam is water, which is most definately not lighter than air as the weather is proving quite abley at the moment up here.

I did some calculations on this- and to lift a 100kg man (of which I am a frankly awe-inspiring example) you would need approximately 120m^3. Yes, this is probably less than a standard airship- but you've then got to factor in the mass of the envelope itself. This envelope has to be strong enough to prevent itself from collapsing in on itself- and therein lies the problem. It's a pain in the ass to build a structure that won't collapse in on itself on such huge scales with tiny thicknesses of envelope wall.

Vacuum ships, therefore, only work at extremely large scales (according to my kickass spreadsheet on the subject- yes, I have looked into this before and yes, I clearly have too much time on my hands...) and are still pretty useless even then.

----

A helium ship carrying (or surrounded by) a cardboard (or nice bulletproof Kevlar) cutout of the Battlecruiser from StarCraft would be awesome- even if it was of limited strategic value, just seeing one of those leviathans hovering over you would be enough to strike the fear of God/Allah/other into you.

Turn it into the worlds biggest and slowest UAV so you're not risking personnel and you could even go for a cheap Hydrogen based version!

Strap a few Hellfire missiles to it, a few solar panels on the whole top of the vehicle to keep it energy-self-sufficient for ridiculous lengths of time and build in some sort of UAV-based rearming system for the Hellfire launchers and to re-stock any escaping lift gas et voila! A perfect low-maintainance Shock and Awe weapon capable of wiping out anyone that attacks it.

That's about when DARPA starts looking at building a Yamato Cannon...

Perhaps instead of using a compressor, this system is using a freezer, (such as a stirling heat pump see sunpowers website) to freeze the helium gas to a very very very cold liquid state (2K?), this obviously requires a suitible heatsink for the heat pump, which could be a problem, however if you are only needing to freeze relativly small amounts of helium, then several kilos of water may be enough...

I make a 26m diameter sphere displacing 11000kg of air (r^3 * pi * 4/3 * 1.2 kg per m2 of air)

13*13*13*pi*4/3 *1.2 = 11043 kg of air.

The thing is I can easily imagine that being made out of rigid plastic, it only has to take 1 bar of pressure difference at any point and I recall that plastics are far strong for their weight than steel and so the internal structure of that would be relatively easy to make it support 11000kgs (Say 50 people and half for vacuum pump and framework.).

Re:"Cold steam is water, which is most definately not lighter than air as the weather is proving quite abley at the moment up here."

Not at low pressures, I'm suggesting that is it used to lower the difference in air pressure if you can't take the full 1 bar outside to inside (not steam at 1 bar inside, which would have to be hot, but then you'd have a hot air balloon not a vacuum balloon).

So if you could only cope with 0.7 bar, you'd make the rest up with something else like steam or N2, something you could lose or make easily.

Developing the idea of a vacuum ship further.

Imagine a ship with a spherical lifting body 26m diameter. This sphere is a thin polymer, when the balloon is on the ground it is pumped out (so that the vacuum pump does not need to be lifted), and when the balloon needs to come down again, nitrogen or water is injected to reduce the buoyancy.

To keep the rigid shape the baloon is filled with sol-gel, the lighted foam made.

http://www.solgel.com/articles/june01/news06_101.htm

I think it's density is 700g per cubic metre, I make 6500kgs of sol gel. But hold on a second, would it really need to *fill* it. Suppose instead we only put a metre thick of solgel around the outside of the shell to keep it rigid., i.e. say 1* 4* pi *r2 *.7 = 1500kgs of solgel, so your 11kgs displacement sphere weight say 3000kgs (half solgel half outer membrane) and can lift 7000kgs.

I know sol gels are insanely expensive, but I'm assuming they can be made cheaply if there was a market for them.

There is no way that you can recover a weight of water from the exhaust gas of an engine, that will balance out the weight of fuel consumed, unless you are burning a fuel that contains way more Hydrogen than Carbon, and/or is lighter than air in itself.

Secondly, why does no-one want to use Hydrogen anymore? It was the skin of the Hindenburg that caught fire (first) - if it had used a non-flammable skin then there would have been no problem.

Which was proposed for the original Hindenberg when that was going to be inflated with helium following the R101 design.

There would be two sets of gas bags, large doughnut shaped ones containing the helium lifting gas, and smaller cylindrical bags embedded in the helium bags containing hydrogen 'anti-ballast'. As the airship burned fuel it would become lighter. Cheap hydrogen would be vented from the bags, reducing lift and returning the vessel to trim.

The plan was abandoned when the US refused to sell helium to Nazi Germany and the Hindenberg was redesigned as a cheaper hydrogen ship.

" inflate a balloon of air inside ..... This is the typical solution used on modern airships"

And, indeed, fish.

Say we made a vacuum balloon out of a sphere of concrete, how thin would it have to be?

Concrete is 2243kgs per m3, 13m radius balloon displaces 11000kgs.

x* 4* pi *13*13 *2243 = 11000

x = 0.0023 meters = 2.3 mms.

Ha ha, too thin, OK maybe a bigger balloon with more concrete, but conversely how big would the balloon have to be before a concrete balloon 2cms thick would float. As the balloon gets bigger the volume it displaces increases by a power of 3 but it's surface increase by a power of 2.

I have to go, but if anyone cares to work it out it might be fun making a floating concrete balloon.

The second picture seems to suggest that the rigid airframe of the Zeppelin will extend just around the diameter of the COSH torii?

Sans the need for ballonet & water/blaugas ballast, I am curious as to the cubic volume of cargo this Zep could transport.

What about the airframe & superstructure: Aluminum-Titanium Alloys? Maybe they have a huge oven in the works to bake carbon fiber segments for the airframe?

"But why not simply compress the helium into high-pressure storage tanks when it's not needed?"

My thoughts exactly...

I'd definitely be open to owning a rigid frame airship as personal airborne luxury "yacht" - complete with glass-floored observation room, fully-stocked bar, four-poster beds, spa, lots of polished hardwood and brass and olde worlde style (and perhaps a "steampunk" look to all the high tech - anyone know where to get a Victorian-styled walnut-and-brass GPS unit?).

Cruising altitude needn't be particularly high - I'd want to be able to see the scenery (and for people below to see my floating pleasure palace and feel suitably jealous) Top speed - as I said, I want to see the scenery.

The best way would be to recycle the helium from the balloon by condensing it into a liquid via a combination of high pressure pipework and low temperature condensers, thereby allowing the ship to fall,

then you simply release the helium back into the ballon to go back up.

Is much, much harder than you think. A regular old GoodYear blimp can remain aloft for almost 10 hours with a car sized hole it it. (or lots and lots of little holes if you prefer) It has to do with the low pressure of the gas in the envelope you know.

If you wanted to put one out of the sky you'd have to hit the cockpit or set it on fire.

http://www.worldskycat.com/

And British too - but I have to say the web site hasn't changed forever and maybe they're defunct. They land on the ground and use a kind of reverse hovercraft idea (suckercraft??).

Wonder if Boeing are infringing any patents? Or just lazy?

Oil isn't the only chemical resource we have to worry about using wisely here on Spaceship Earth. Helium is another very valuable resource, and we should be careful about how we use it up. An airship that deliberately vents it in order to control buoyancy seems very wasteful to me. One AC has suggested a closed-loop cycle to refrigerate any lost helium. Sounds like a good idea, but I wonder if it can work in practice. Since helium will leak out of any balloon and since (I imagine) the refrigerator will be very heavy and/or require a quite a bit of energy to operate it looks like this idea faces some very big challenges if it's to get off the ground and/or be sustainable enough to be a real contender.

Zeppelins: cool? Yes. Practical? Probably not.

http://www.wired.com/wired/archive/8.08/helium.html

A titanic "*Eros*craft" should indeed be able to haul an entire US Army unit...

... I want someone who invents something that resembles a huge phallus the gargantupenis, or dongzilla, or something similar.

I'd be so pleased.

the COSH thing resembles a giant condom being rolled onto the blimp.

Paris because....

The day i arrive at work in a fish is the day I.......er...arrive in a fish.

Just a crow a little. I had the pleasure of a ride in an Airship Industries er. fish sometime back in the 80s. They had a couple flying at Farnborough and I managed to bags me a ride over the swimming pools of Weybridge.

I can't decide. COSH. Can't be right. Is he a Babylon 5 fanatic, or did he just fat finger the keyboard when he's actually rolling in DOSH?

http://www.youtube.com/watch?v=6bWpXqU6ekY

"But why not simply compress the helium into high-pressure storage tanks when it's not needed?"

indeed.

as far as bouyancy control goes for something like that it seems like the most obvious and relatively simple option.

a few cannisters spread out evenly around the ship that are able to hold enough compressed gas so as to keep gas expansion down to a minimum whilst increasing weight without actually venting gas seems to seems like an option that ticks all the required bxoes for what's needed.

surely such a simple solution would not evade epople smart enough to build an airship? well, aside from the hindenburg lads, they weren't overly bright wth the whole 'flammable gas' idea. :o)

Paris, cos you can't stop her from going down either!

When we get fusion working, there should be plenty of helium available. If you could make the reactor small enough you could put it in the craft and make it as you go along, oh hold on it would use heavy hydrogen as fuel which would be even more buoyant. Oh never mind I'm sure we've got plenty of time to work that one out.

"There is no way that you can recover a weight of water from the exhaust gas of an engine, that will balance out the weight of fuel consumed, unless you are burning a fuel that contains way more Hydrogen than Carbon, and/or is lighter than air in itself."

This rather depends on what you consider "way more hydrogen than carbon". Methane is one extreme, and burning 16 grams of methane gets you 36 grams of water. Oils and fats are essentially (CH_2)_n, and get you 18 grams of water for every 14 grams of lipid. But I suppose by atoms they still have more hydrogen than carbon. Burning benzene will only get you 54 grams of water for every 78 of fuel, so /technically/ I suppose you're correct, but pretty much any fuel that's not coal will contain more hydrogen than carbon anyway.

You are forgetting the oxygen Dave. As Craig points out most fuels contain two hydrogen atoms per carbon atom, with two additional hydrogen atoms per molecyle. Two and two hydrogen atoms form up with oxygen atoms from the air and form water. If you trap the water from the exhaust what you basically do is to replace a liquid with two hydrogen atoms per carbon atom with another liquid that have two hydrogen atoms per oxygen atom. Oxygen and carbon have comparable weights with oxygen being the heavier one.

Craig, I'll take your numbers at face value, but if we're talking something like condensing the water vapour in the engine exhaust, wouldn't it also condense any water vapour in the incoming combustion gas ie the surrounding clouds (even when not cloudy, humidity is often a couple of dozen percent or more)? Or have I misunderstood, and if so what went wrong? If I haven't misunderstood, then in most parts of the world you'd get more condensate out than the input from fuel would initially indicate, right?

Flame, because there's no smoke without fire. Unless it's fake smoke, or clouds.

"based in California"

Nuff said.

Airships in the form of blimps have been using inflatable cells inside the lift bag to adjust lift for some time so nothing new.

Also see the following site for an airship that uses an inflatable structure and lands on the ground. http://www.21stcenturyairships.com/

The ship in picture has stering planes wich if I remeber Barns Wallises figers account for 5% of the weight and 25% of the drag, oh and when landing and taking off (at slow speed)dont work well.

Better use vectored thust as 21st Centry Airships do and you could use some of the thrust to lift the ship when landing and taking off. This would allow you to have a quick turn around, ie quicker than adjusting the lift, which may be usefull in the mitatery!!!

Mines the one with Barns Wallises Autobiograthy in the pocket

While the buoyancy issue is problematic, the article and comments seem to have missed the other huge problem with lighter than air craft. Being lighter than air they're very easy to blow around using air. Anything other than dry, windless weather and the things become really difficult to fly. Rain can be a right bugger, lots of nasty unbuoyant stuff sticking to the enormous surface area...

They're just a crap idea, let them die in peace...

Has anyone ever considered methane-filled airships? Inflammable, true, but a lot less prone to leaking than hydrogen, and less explosive. They even let us use the stuff to cook with.

It's lighter than air.

If the airship were fuelled part with its own methane and part with liquid hydrocarbon it could maintain correct bouyancy: loss of lift from burned methane = loss of weight from burned liquid fuel.

Methane can also be "compresed" without much pressure, into cold water, to yield methane hydrate or clathrate. A little warmth reverses the process. This might also be a useful property.

BTW the Hindenburg disaster was not primarily caused by hydrogen. The primary cause was an electrical discharge setting fire to the highly inflammable metallized-paper-and-dope outer skin. That fire then released and ignited hydrogen from the gasbags. Had the gasbags been helium-filled, the Hindenburg would still have burned and crashed, but not such a big fire. I'm fairly sure that a hydrogen-filled airship built with modern materials could be safe. Ish. Cheap flight in a third-world country sort of safe, anyway.

Have you any idea how little lifting power either hydrogen or helium possesses?

A quick back-of-the-envelope calculation shows that lifting 500 tons will require a volume equivalent to a sphere 2900 feet (over half a mile!) in diameter.

This assumes, of course, that the structure of the airship is massless. I am guessing here, but I suspect that any structure strong enough to keep 500 tons of cargo from dropping through the floor will add a good deal of vehicle weight to the equation, increasing vehicle volume much further.

...by the same thought presented at the end of the article. As soon as they presented the problem, I wondered the exact same thing, "Why can't they just compress what they aren't using?" There MUST be some sort of technical issue, because if I (An engineering idiot) can think of that right away, I'm sure some genius has thought of it, too.

So, does anyone know why it wouldn't work?

Because I didn't read the second page...

electrical power doesn't change weight, solar panels covering the topside would be useful too...

The Hindenburg was actually designed to use helium, but the USA, which has a virtual monopoly on the supply, refused to supply it to Germany, despite the fact that it has no strategic value and that, in any case, as the Hindenburg lost ~5% on every trip across the Atlantic, anytime the USA had wanted it could have cut off the supply.

Also worth pointing out that the Hindenburg and its predecessor, the Graf Zeppelin, provided a regularly (weekly?) service between Germany and Brazil.

Until the disaster not a single passenger had been harmed.

Had the helium been available...

While I understand English separates our two countries, here where DARPA exists, we call it the DefenSe Advanced Research Projects Agency. I suspect that over in the UK, it might just be called "Q section". Similar end functions.

Just to wrap this one up, a 2cm thick concrete vacuum balloon would need to be 224m in diameter to fly.

Can you imagine it? A 224m diameter sphere of concrete flying in the sky under it's own boyancy, blown about by winds. What a sight that would be.