Giant solar powered airship could satellites and act as low cost communications and surveillance hubs, it has been claimed.

A new report backed by Nasa also says the stratosperic balloons, which would fly to the edge of space, could allow science experiments and even space telescopes to be launched for a fraction of the cost of a rocket.

Experts have already flown experimental airships at heights of 65,000 feet, and weather balloons often also reach high altitudes.

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Nasa says the airship contest will have a $4m prize fund, and will be launched next year.

HOW IT WOULD WORK Nasa says the airship contest will have a $4m prize fund, and will be launched next year. 'Competitors must fly a powered airship that remains stationary at 20km (65,000Z) al/tude for over 20 hours with a 20kg payload,' the agency revealed. 'The design must be scalable to longer flights with more massive payloads.' Advertisement

A recent study from the Keck Institute for Space Studies at Caltech suggests that a more capable airship may not be far-off - and calls for Nasa to sponsor a contest to build better airships.

'There are few opportunies for space missions in astronomy and Earth science,' Nasa said in a document outlining its plans.

'Airships (powered, maneuverable, lighter-than-air vehicles) could offer significant gains in observing sky and ground coverage, data downlink capability, and continuity of observations over existing suborbital options at competitive prices.'

Nasa says the airship contest will have a $4m prize fund, and will be launched next year.

'Competitors must fly a powered airship that remains stationary at 20km (65,000Z) al/tude for over 20 hours with a 20kg payload,' the agency revealed.

'The design must be scalable to longer flights with more massive payloads.'

Experts have welcomed the plans.

'Stratospheric airships could give us spacelike conditions from a spacelike platform, but without the spacelike costs,' Sarah Miller, an astrophysicist at the University of California, Irvine, told the New York Times.

To get a better idea of how stratospheric airships might fit into scientific research, Dr. Miller and colleagues prepared a lengthy analysis at the Keck Institute for Space Studies.

'Over the last two decades, there has been wide interest in developing a high altitude, stratospheric lighter-than-air (LTA) airship that could maneuver and remain in a desired geographic position (i.e., 'station-keeping') for weeks, months or even years,' the report said.

'Such a stratospheric airship would offer the military surveillance capabilities over large areas.

The United States Army commissioned test flights of the Hi-Sentinel 20 to determine whether blimps could hoist communications satellites above enemy territory.

'This platform would also provide telecommunication companies a means of providing commercial communication and data services to consumers in remote areas.

'While stratospheric airships remain a promise rather than a reality today, seeing through the final stages of development of such vehicles operating in the relatively light winds present in the lower stratosphere at altitudes around 65 kft (20 km), would enable unique data collection opportunities for Earth and atmospheric scientists.

'They would be a gamechanger for space scientists since their costs as a platform would be substantially lower than satellite missions.'

Steve Smith, an aerospace engineer who in 2005 designed one of the first successful stratospheric airships, the Hi-Sentinel 20.

The United States Army commissioned test flights of the Hi-Sentinel 20 to determine whether blimps could hoist communications satellites above enemy territory.

The airship took off from New Mexico in 2005 and remained aloft only about eight hours, but it proved that an unmanned blimp could be steered through the stratosphere by a team of engineers on the ground.

'Science, rather than war, could be the ultimate motivator to push industry toward final development of stratospheric airships, which will provide a unique platform for monitoring our most precious resource, the Earth, and for seeking out the new cosmic horizons toward the edge of our observable universe,' the Keck report concluded.