Original URL: http://www.theregister.co.uk/2009/08/19/sanswire_sts_111_announcement/

Unmanned German sperm dirigible 'to fly within days'

Robo-airship's tail full of weightless Zeppelin fuel

By Lewis Page

Posted in Science, 19th August 2009 14:42 GMT

A German-American venture says it is now days from the maiden flight of its 111-foot long, tadpole-esque "segmented" drone airship.

The STS-111 "Stratellite", produced by Sanswire of Florida and TAO Technologies GmbH of Stuttgart, has now been assembled at the firm's German test centre. According to a Sanswire-TAO announcement issued yesterday, "the first flight of the full scale STS-111 is expected to take place at the end of August". The test vid above shows a smaller prototype.

The robotic ship uses a cunning technique from the lost golden age of dirigible airships to deal with the knotty issue of buoyancy control. Only the "head" compartment of the bendy airship actually contains helium for buoyancy. The remaining "tail" cells contain the fuel for the craft's engine, in the form of "Fuelgas" mixed to have the same density as air. Thus, as fuel is burned the buoyancy of the ship is unaffected and there's no need to vent off expensive helium.

The company describes this as the "unique weightless Fuelgas system", but in fact it isn't unique. The famous Graf Zeppelin airship liner of the 1930s ran on "Blaugas" for the same reasons, filling up to a quarter of her mighty hull with the gaseous neutrally buoyant fuel.

The STS-111 is an interim, medium altitude ship intended as a stepping stone towards a more capable stratospheric craft to follow. This would lurk for long periods in the "wind bucket" found between 65 and 70,000 feet, so as to avoid being blown off station. It would serve as a communications relay platform, aiming to compete with satellites (hence the "stratellite" name). ®