Original URL: http://www.theregister.co.uk/2010/06/22/lemv_contract/

Huge new airships for US Army: designed in Blighty

Hybrid dyno/hover vessels to make 3-week flights

By Lewis Page

Posted in Science, 22nd June 2010 11:39 GMT

British engineers are to partner with a major US defence contractor to build a large "optionally manned" robot spy airship, intended to lurk for three weeks at a time in the skies above Afghanistan.

The LEMV airship to be built for the US Army. Credit: Northrop/HAV

Now that's a big robot.

American arms'n'aerospace goliath Northrop Grumman announced the deal last week, revealing that the US Army has ordered "up to three" Long Endurance Multi-Intelligence Vehicle (LEMV) ships in a $517m deal. Northrop will lead a consortium of several firms on LEMV, but it is acknowledged that the actual airships will be based on Brit company Hybrid Air Vehicles' 300-foot-long HAV304 design.

Hybrid Air Vehicles is the latest in a long line of UK firms which have sought to revive the idea of large airships. In the 1930s huge rigid vessels developed from World War I zeppelin bombers astonished the world, acting as longhaul air liners and (in two cases) as flying aircraft carriers with embarked forces of biplane fighters.

Following well-publicised disasters like the R101 and Hindenburg tragedies the great rigids disappeared. But some latter-day enthusiasts have kept the dream alive: in particular Blighty's Roger Munk, who was the inventor and driving force behind UK companies such as Airship Industries, ATG and now Hybrid Air Vehicles (HAV).

Brit design sees off P791 suck-ship and miracle gas-squash rivals

HAV's new special sauce was the idea of "hybrid" ships which would not, like their illustrious predecessors, actually be lighter than air. Some 60 to 80 per cent of their weight would be supported by the buoyancy of their helium, and the rest by other means: vertical thrust from the engines during takeoff and landing, and aerodynamic lift generated by the ship's forward motion while in transit*. Here's a vid of a subscale prototype in action:

During Munk's four-decade career from the 1970s on, however, the remaining world airship industry never really got much further than traditional blimps with some minor refinements. At one point early this century it seemed that the grand old days might be back, when famous US military crazytech agency DARPA decided to build an enormous "Walrus" airship transport. This would have been capable of hauling an entire US Army ground combat battalion and its equipment across hundreds of miles to land without an airport, a task impossible for any realistic fleet of current aircraft.

Conventional airships could never fulfil the Walrus requirement as they had to take on equal tonnages of water ballast when offloading heavy cargo. This was to prevent them becoming uncontrollably buoyant and surging wildly off the ground - then to soar through their "pressure height" and lose most of their helium.

Thus the various Walrus contenders generally put forward hybrid-style designs. HAV partnered with Northrop to offer theirs; more well-known at the time was the P-791 subscale demonstrator (seen in the vid below) built by rivals Lockheed. The P-791 used a reversible hovercraft air-cushion system to manoeuvre on the ground for landing and takeoff, which could also be used to suck it firmly down in place while offloading cargo.

Another rival was the Aeroscraft from Ukrainian designer Igor Pasternak, which was intended to make use of superheat/chilling and mysterious gas-compression COSH technology to help deal with the lift-control problem.

High spy ship hopes to rise above enemy ground fire

In the end the Walrus was cancelled in 2006, perhaps sensibly enough as its military usefulness was rather doubtful. It was only spec'd for 10,000 feet cruising altitude, meaning that the huge craft could be attacked by shoulder-launched missiles at any point on its flight path.

Following the demise of Walrus, the only game in airship town became the US Army's Space and Missile Defence Command, interested in airships as airborne listening, communications and radar posts rather than transports. An airship can potentially stay up for much longer than a fixed-wing craft, so lowering costs and increasing coverage. The US Air Force, much preferring jets or satellites, was uninterested; but the soldiers, seeing the airship merely as a tool rather than a way of life, thought it might be of use.

Thus was born the LEMV, under which a much smaller Walrus would carry a much smaller surveillance payload on higher patrols at 20,000 feet where it would be less easily attacked by basic groundbased weapons. Risk would be further reduced by the fact that the ship would be unmanned on operations, though flown by onboard pilots when in controlled US airspace or en route to or from the warzone.

Some analysts consider that an airship-borne persistent spy package would be able to create a huge hi-res moving picture of an area - say, around a city - sufficiently comprehensive to more or less eliminate the threat from roadside bombs or insurgent ambushers. Every time such an incident occurred, it would be possible to rewind and zoom the picture so as to backtrack the bomb-placing team or whoever to their bases.

Whether such airborne spy equipment actually exists is a moot point: most of the publicly known programmes don't offer this level of capability, rather seeking to provide multiple "drinking-straw" narrow viewpoints in place of the single camera system found on most present-day surveillance birds.

In any case, the actual payload of the LEMV is to be a moveable feast: it will be built with the ability to swap "plug and play" modules in and out while deployed in theatre, so that local commanders can send it up carrying whatever they like.

The optionally manned LEMV is expected to be approximately 300 feet long and will use turbodiesels to drive its swivelling propulsors during takeoff and landing. Once on station these will shut down in favour of a more economical electric drive running from a central generator, which will also supply juice for the payload. The margin of weight supported initially by thrust/dynamic lift will mean that the ship can burn up its fuel without becoming positively buoyant, and so will not need to vent costly helium in order to land.

The ship is to fly for the first time next year, and set for operational testing shortly thereafter.

All in all, the LEMV isn't a Walrus, isn't a proper return by true successors of the great 1930s dirigibles. Nonetheless it's a very noteworthy project which could lead to great things if it succeeds: and $517m, for all that much of the cash will go on payload tech rather than the ship itself, isn't chickenfeed.

Unfortunately the news comes too late for Roger Munk, who died in February: but one can assume that if he knew about the LEMV announcement he'd be very happy. ®

Bootnote

*It was actually quite common for the oldtime fully-buoyant 1930s ships to make use of dynamic lift at times, though the most successful operators - those of the German interwar zeppelins - cautioned against it as it rendered the ship liable to disaster if engine thrust was lost, and was also thought to overstress the ship.