First rigid airship since the Hindenburg cleared for outdoor flight trials
Can brand new COSH tech finally revive the aerial leviathans of the 1930s?
Why airships never really got off the ground
One of the reasons that the DARPA Walrus plans of the noughties never went ahead - despite the appearance of the impressive Lockheed P-791 testbed airship - was that while a big rigid ship could, technically, do the military air-assault job, it would normally have to vent off much of its lifting gas as the troops disembarked so as to avoid soaring disastrously skyward. Nobody any more is really up for using explosive hydrogen as a lifting gas, especially for a ship headed into combat, and simply chucking away huge amounts of expensive helium isn't really on either. On the other hand, if the ship could only deliver its cargo at places where it could rapidly take on vast amounts of water ballast it wouldn't be very useful.
Indeed, with nothing else in the picture, a good deal of lifting gas would generally have to be thrown away on any long airship journey to compensate for the weight of fuel burned by the engines and so let the vessel get down at the end: this too would be unacceptable in a helium ship, or even a hydrogen one aiming to land at a place without a hydrogen supply.
This was the great Achilles heel of the pre-WWII rigids, in fact, though it didn't prevent them being built back then as their rival the long-range aeroplane was in its infancy. Various solutions have been offered: one is the use of gaseous fuel weighing the same as air, stored in the envelope alongside the lifting gas, as seen on the inter-war airliner Graf Zeppelin. Another ploy is the use of condensers to collect water from the engines' exhaust, as used (though apparently their gear didn't work very well) by the US Navy flying aircraft carriers Akron and Macon in the 1930s. Similar machinery was also developed for the ill-fated Hindenburg and her sister ship Graf Zeppelin II, though as it turned out the US wouldn't let the Nazis have any helium. As a result the two ships were hydrogen filled and didn't bother with water-recovery.
Since the disappearance of the great rigids following the Hindenburg disaster, other ploys have been proposed: most notably the use of ships which are actually heavier than air and supplement their gas lift by the use of vertical engine thrust and/or dynamic lift generated as an aeroplane does by flying along. This renders the ship just as vulnerable to disaster following an engine failure as an aeroplane or helicopter is, but it removes some of the ballast problem.
All these plans have circulated for decades, however, without any prospect of a return by proper, heavy-lift big rigid ships: though the US Army's LEMV ship of recent years (now cancelled) - actually aimed at high-flying, light-load spy missions - could potentially have carried out cargo tasks had it survived.
The Aeroscraft, though, is different because it has COSH: we here on the Reg airship desk first reported on this technology a few years back. Essentially what COSH does is take some of the ship's helium and compress it to the point at which it is heavier than air, so removing lift. It seems likely that the gas isn't compressed to any very high pressure, meaning that the tanks in which it is put could be potentially large enough to do the job while remaining acceptably lightweight.
They might well be of fabric construction - this seemed to be the case on initial test blimps. Pressures similar to those seen inside some modern bike tyres would be enough to render helium heavy rather than buoyant, or perhaps the system merely makes it less buoyant.
Looks like rigid tanks these days, but probably not any very high pressure
Pasternak's company nowadays makes bold claims for COSH, saying:
The control of static heaviness is Aeros’ solution to a virtually ballast exchange-free flight. Through a pilot’s control, the vehicle itself can be configured to provide enough static heaviness to offload personnel and cargo, without the limitation of taking on external ballast to stay grounded.