Science: Clipping the costs of high fliers: Peter Bond looks at a reusable rival to the Space Shuttle which could eventually take tourists on holidays that are literally out of this world

IMAGINE throwing away your car after each journey and buying a new one. Sounds crazy? That is what happens every time a rocket carries a satellite into orbit. Since Sputnik heralded the dawn of the space age 36 years ago, many thousands of expendable launch vehicles have soared into the sky, never to return. That represents an awful lot of hardware and money gone up in smoke.

The Space Shuttle was supposed to change all that, but it has never fulfilled Nasa's expectations. Now it may have a competitor. At the end of this week, if the weather holds, the desert sands of New Mexico will reverberate to the roar of rocket engines, as a small, bullet-shaped vehicle known as the DC-X (Delta Clipper Experimental) lifts off and manoeuvres overhead before gently setting down once more on a small concrete pad.

This revolutionary launch vehicle is the result of a competition held by the United States' Ballistic Missile Defence Organisation (BMDO), the body originally responsible for the heavily cut-back Star Wars programme. BMDO was hoping to obtain a totally reusable launch vehicle capable of carrying numerous small payloads (less than nine metric tonnes) into orbit at very short notice. Requirements included low launch costs, rapid turnaround, small ground crews and minimum maintenance. In short, the space equivalent of a modern aircraft.

The winner of the dollars 58.9m ( pounds 40m) contract was McDonnell Douglas, with its vertical take-off and landing design. Less than two years after its acceptance, the DC-X, a one-third scale prototype, is ready to begin flight testing. Such record-breaking rapidity is the result of borrowing and adapting existing technology, thus minimising paperwork and development of new hardware. As William Gaubatz, the project director, admits: 'We literally went to the aircraft world and pulled out navigation systems, computers and other hardware, then reconfigured them to meet specific needs of the DC-X'

One of the most important preconditions was that the new vehicle would have single-stage-to-orbit (SSTO) capability. Until now, all leading launch vehicles have been multi-stage affairs. As the fuel in each section is exhausted, the redundant stage is discarded. High-energy liquid oxygen/liquid hydrogen propellants have enabled a reduction in the number of stages to two, and now the single- stage launcher is about to become a reality.

The first trials of the 40ft-high (12.2m) vehicle will begin in the early morning, when wind speeds are at a minimum. Under the watchful eye of the former Apollo astronaut Charles Conrad, just three ground controllers and a further three staff will monitor progress from a nearby trailer.

The rocket will lift off from the concrete flight stand and rise to a few hundred feet. The modified engines will then throttle back to allow the craft to hover, extend its landing legs and descend on to a landing pad.

If all goes well, later flights will take place at greater altitudes, with the final series simulating re-entry from Earth's orbit. The rocket will head towards Earth nose-first, then rotate into a base-forward position before using its onboard radar for a pinpoint touchdown. Information for navigation and guidance will be fed into the vehicle's computers from satellites.

If the DC-X tests are successful, McDonnell Douglas hopes that the BMDO will give the go-ahead for a new family of sub-orbital rockets. More significantly for the future of space transportation, the company is prepared to develop a full-scale demonstration version of the DC-X as early as 1997, followed by a fleet of operational vehicles before the turn of the century.

Standing 127ft (38.8m) high and 30ft (9.2m) wide at the base, the full-size monster would be capable of lifting nine tonnes of cargo into low Earth orbit. Unlike most rockets, which carry their payload in the nose, Delta Clipper would have a cargo hold in its mid-section, between the two fuel tanks. The rocket would be able to carry out a range of activities automatically, including satellite launch and retrieval, cargo transfer and space-station resupply.

McDonnell Douglas argues that, by combining reusability with streamlined ground and flight operations, the Delta Clipper would slash launch costs and open up the high frontier to a whole new army of potential users. From the current figure of about dollars 50m for each flight by a large expendable rocket, charges for the newcomer could amount to less than dollars 10m, and perhaps as low as dollars 1m, per flight.

Delta Clipper would also have potential as a future replacement for the unreliable, expensive shuttle, which requires more than 40,000 people for maintenance, operational support and turnaround, compared with 35 for the Delta Clipper. Instead of several months between each orbital mission, Delta Clipper should be able to fly again within three to seven days. Furthermore, its manufacturers say that the onboard adaptive guidance will allow it to fly in wind conditions that currently ground the shuttle.

Its eight rocket motors would give it the capability of returning safely to the launch site, should a problem arise during take-off. Since the engines would operate at 90 per cent power, there would be plenty in reserve to deal with any emergencies. Reduced wear and tear would lead to longer life between overhauls.

With a crew of two installed in the central hold, the Clipper could even serve as a human transportation system. It could eventually open up near-Earth space to tourists: Dr Gaubatz suggests that the Delta Clipper could eventually carry up to 50 people on the most exciting adventure holidays ever offered. 'Airlines didn't start out by carrying people. Word slowly got around.'

The one red light on the horizon involves funding. The BMDO has been wound down and no longer requires a large reusable rocket capable of placing sizeable payloads in low-Earth orbit. Nasa and the US Air Force have already invested huge sums in programmes to build new launch systems and show little interest in such a revolutionary concept. They are trying to sell the idea of a new expendable rocket, known an Spacelifter.

So will the full-size Delta Clipper ever fly? At present, funding beyond 1993 is uncertain. However, says Dr Gaubatz, 'Companies didn't rush out and buy a jet aeroplane the first time they were introduced. Space will never be opened up until people can get there safely at a price they can afford. We'll be able to provide the data to enable the administrators to make up their minds. What will remain is for someone to say 'Do it'.'

The author's new book, 'Reaching for the Stars, the illustrated history of manned spaceflight' has just been published by Cassell at pounds 15.99.

(Graphic omitted)