The first rigid airship to be built since the 1930s is about to commence trials in California: and the Pelican prototype also features a new technology, never yet flown, which could finally change things for lighter-than-air craft and see the leviathans of the skies make a serious comeback at last.

The 230ft-long, 18-ton demonstrator has been built for the US military by radical airship firm Aeros of California, helmed by Ukrainian LTA visionary Igor Pasternak. Aviation Week reports that it has now tested its ground manoeuvring equipment inside its hangar, and that next week the ship is set to actually lift off in a further sequence of tests for the Pentagon.

In particular, the US military wants to see if the Pelican can defeat the great bugbear of airships: the fact that they cannot usually offload cargo or passengers without taking on equivalent amounts of ballast. This is because, as weight is removed, the ship will become massively buoyant and will surge upwards uncontrollably.

This isn't too much of a problem where facilities exist to take on water ballast, but ordinary planes are already well established for moving stuff between established airports and bases. Slow airships are unlikely to break into the conventional air cargo sector, as we've previously discussed on these pages.

But the airship can potentially do things that planes can't: specifically it can come down vertically or nearly vertically, like a helicopter, on an unimproved landing zone - and it can do so after a much longer trip than any realistic helicopter can make, as its engines only have to push it along rather than holding it up too. This raises the prospect of long-range military airborne operations which would be significantly less likely to turn into heroic disasters*. Big airships could potentially deliver fully equipped troops, with proper vehicles and heavy weapons, and have them arrive organised and concentrated. Best of all, they could potentially bring them back again if something went wrong.

Unfortunately, while airships until now have been able to bring troops to a landing site, actually getting them off the ship in a timely fashion without a disaster would normally involve venting off huge amounts of lifting gas. This would effectively take the ship out of play until it could be regassed. With helium - the only lifting gas acceptable in a modern ship, especially one headed into combat - expensive and difficult to resupply, this would render the whole idea impractical.

That's where Igor Pasternak's enigmatic Control Of Static Heaviness technology, which the Reg first reported on a few years ago, comes in. Details are closely held, but in outline it appears that COSH involves pumping helium from the ship's lifting cells into containers where it is held at a higher pressure and becomes negatively buoyant. We here on the Reg airship desk suspect that these tanks would be large, of flexible fabric construction rather than rigid metal, holding the helium at a relatively low pressure - that seen inside some modern bicycle tyres would be enough to render it heavier than air. Certainly this appeared to be the type of tank in use on early test blimps. This would minimise the weight of the tanks and the compressors/condensers needed to cram the gas into them.

Pasternak tells Av Week that the COSH gear aboard the new ship can vary the 36,000lb (16,329kg) ship's weight by about 10 per cent. Combined with the use of vertical thrust for takeoff and landing and aerodynamic lift in transit, this should mean it is capable of unloading a useful cargo after a long flight without venting gas.

There's a further issue which tends to complicate matters for airships. As fuel is burned the ship gets lighter, making it difficult to get down on the landing zone and even more difficult to get down after the return trip with cargo gone and COSH tanks presumably filled to capacity already.

Massive rigid ships of the 1930s that used (or were intended to use) helium gas battled this problem by using special equipment to condense water out of their engine exhausts, so taking on ballast (albeit slowly) in mid-air. This gear didn't work terribly well aboard the US dirigible aircraft carriers Akron and Macon, the only ones to actually use it - but the German version intended for use on the Hindenburg and Graf Zeppelin II was said to be better, and today's more advanced technology could presumably do better still. Various promising options exist which weren't known about in the 1930s, quite apart from the use of better modern materials, power sources etc.

Some reports had it that the Aeros ship was to have exhaust condenser gear too, but she doesn't appear to have it yet. This may be something of an academic point as, for now, there is only funding for the most limited trials. Next week will see the ship lift off the ground and test her COSH equipment, but this will take place inside her hangar. No true free flights, still less any extended journeys, will be made unless the Pentagon hands over more cash. It would appear that like so many other airship projects, delays have meant that not as much could be done with the assigned money as had been hoped.

Still, COSH on its own is potentially a game changer, an actual new thing in the world of airships after so many decades. Airship enthusiasts have heard little but bad news of late: the US Air Force's "Blue Devil" mega-blimp has been cancelled and the future of the US Army's much delayed Long Endurance Multi-Intelligence Vehicle (LEMV) hybrid spy-ship is in doubt; it should have been in Afghanistan by now if it was to survive.

The future for the new Aeros ship is no clearer: but it does seem that it might at least see COSH achieve some advancement, and so perhaps change the lighter-than-air picture at last. ®

Bootnotes

*Until now the only way to bring in a large number of troops from the air over long distances has been mass parachute assaults. Such operations, despite the fact that paratroops are always a picked elite, tended to be expensive disasters even when conducted relatively close to friendly surface support in the old days (Crete, Arnhem, Dien Bien Phu etc). Now that there are helicopters, one would only use parachutes for a long-haul mission deep into hostile territory - and given that para drops are strictly one way until a runway and a large surrounding perimeter can be captured, that would be a very gutsy call. This is why the British forces have not conducted a combat parachute drop since the 1950s, and why mass drops have been so very rare since then.

By the way, we do know that the Graf Zeppelin II kept flying for a bit after the Hindenburg disaster, and that she was a rigid ship; no need to write in complaining about the headline unless you really really want to. Likewise we are aware that modern Zeppelin NTs have some rigid structure, but they maintain envelope shape by pressure and so are semi-rigids not rigids proper, like the Aeros ship.