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Reach for the Stars - Space Tourists Reach for the Final Frontier - By Justin Cummingham
Professional Engineering, the journal of the Institute of Mechanical Engineers, 25 January 2006

The next few years could see the birth of an exciting new industry: space tourism.
Justin Cunningham charts the development of the first private, reusable vehicles

Modelled on the 1927 Orteig Prize for the first non-stop flight from New York to Paris, the Ansari X-Prize aimed to kickstart the space tourism industry by offering $10 million to any company that could complete two suborbital flights within two weeks using a reusable spacecraft.

The private sector responded and the prize sparked new ideas and philosophies about what should drive the spacecraft design. It was won in October 2004 by Scaled Composites' SpaceShipOne, and the past year has seen unprecedented investment by Virgin Galactic to build the first commercial spaceport, in New Mexico, and become the first private operator to offer flights in planes based on SpaceShipOne. Building is soon to start and flights could follow as soon as 2007.

So are we seeing the dawn of a viable new industry, and if so what sort of engineering is needed to sustain and develop this new generation of flying machines?

Heading up the British efforts are Starchaser and Bristol Spaceplanes, which have similar ideas about how to make a successful, low-cost, reusable craft. Although both incorporate similar philosophies, the initial concepts were radically different.

Developing new technology can be a costly, time-consuming and risky business. So to make space travel not only low-cost but also low-risk, the amount of new technology that needs to be developed must be strictly limited. Instead, existing platforms, tried-and-tested technology and standard processes must drive designs to satisfy these constraints.

David Ashford, head of Bristol Spaceplanes, explains that his proposed designs - including Ascender and Spacecab - are based as much as possible on conventional aircraft design. "By using conventional take-off and landing, conventional materials and jet engines and integrated conventional rocket engines, there's no need for new technology development," he says. "It's all about taking well-established principles and components and putting them together in a different way to get a different end result."

The most promising British effort is Manchester-based Starchaser, which has been developing conventional rocket systems for more than 10 years. One of only a handful of global private companies that have actually manufactured and tested flight hardware, it is hot on the heels of X-prize winner Scaled Composites and its SpaceShipOne. Steve Bennett, chief executive of Starchaser, says: "Our overall design philosophy has been to take things one step at a time. We design it, build it, test it and then learn from it. Then we can be sure of the next step."

Like many aerospace companies, Starchaser uses as many COTS (commercial off-the-shelf) components as possible to minimise development costs. Bennett says: "Obviously there are limitations to this, such as our rocket motor development, but we would still try and use valves and fittings that are COTS as well as working within well-researched principles."

Two-in-one craft

Although inspections and pressure tests are carried out, Starchaser never tests components to destruction because their quality is a prerequisite guaranteed by the manufacturer. Part of the cost associated with COTS components is the level of validation they undergo during manufacture.

Scaled Composites uses a combination of the conventional and unconventional in its $30-million, two-in-one craft. It comprises a parent aircraft, White Knight - which resembles another of the company's not-so-conventional aircraft, Global Flyer One - and a smaller, rocket-powered craft, SpaceShipOne, attached to the underside. Taking off like a conventional airplane, the highly efficient twin turbo jets of White Knight lift it to around 50,000 feet where it releases SpaceShipOne. In freefall, SpaceShipOne fires its single rocket motor, which drives it into the upper atmosphere to an altitude of about 60 miles.

The acceleration forces inside the cockpit build up gradually and peak above 5 g for less than 10 seconds. With the pilot and passengers reclined, these forces should be quite tolerable for anyone in reasonable health. The passengers will then enjoy a few minutes of weightlessness before re-entry.

At its apogee, the ship converts to a "feathering" mode, folding its pneumatically actuated wings upwards to provide a shuttlecock effect. This creates extremely high drag on re-entry. It also minimises aerodynamic and thermal loading on the structure while allowing deceleration at a higher altitude. "Since the altitude is higher, the pilot can glide further after the entry deceleration," says a spokesman for Scaled Composites. "A SpaceShipOne pilot can glide more than 60 miles after he converts back to the non-feathered glider shape."

The propulsion system is referred to as a hybrid because it has features of both solid and liquid rocket motors. The hybrid motor uses nitrous oxide (laughing gas) as an oxidiser and hydroxy-terminated polybutadiene (HTPB or rubber) as the fuel. Scaled Composites says: "Both are easily storable and don't react when mixed. Nitrous oxide also self-pressurises when at room temperature, eliminating the need for complicated turbo pumps or plumbing to move the oxidiser to the combustion chamber." The rocket is fired by the pilot during freefall from White Knight, but the engine has no thrust control.

Starchaser takes another approach. Its long-term view of the emerging industry has led it towards a conventional ballistic design. Bennett says: "Our ultimate objective is to put people into space and that's not just suborbital but orbital once the industry has matured and grown. Rockets have long been the vehicle of choice to get to space and the science is well established. This makes the ballistic approach scalable, which is a critical advantage for future development. Various spaceplane designs may find this more of an issue."

Unlike Scaled Composites, which has the financial backing to contract out the design of its propulsion systems to rocket specialists, the Starchaser team has developed its own rocket engine entirely in-house. Its kerosene and liquid oxygen system has come from gradual steps taken by the company over recent years.

Much of the manufacture and machining of Starchaser projects, however, is sub-contracted to industry leaders in the UK. Starchaser is keen to point out the level of expertise and quality it has received: "We really have to champion British industry. We have some world-class [manufacturing and machining specialist] companies in the UK that offer things that the rest of the world can't. As well as this they always are willing to try and have a go."

Both Starchaser and Scaled Composites use CAD systems, finite element analysis and computational fluid dynamics as tools for development and flight analysis. "Without CAD, FEA and CFD we would have found it virtually impossible to remain competitive," says Bennett. "These tools have helped us drastically reduce costs as well as saving us precious development time."

Convenient for spaceport

The US government is also impressed by its efforts, with both federal and state governments enticing Starchaser to relocate to New Mexico near the first proposed spaceport site. Bennett says: "They are bending over backwards in terms of licensing and removing red tape. The bureaucracy and level of expense in the UK are unbelievable. The US [financial] climate is much more conducive to this developing industry, but this is heartbreaking for us as we have built up so many excellent links with both industry and academia that will be all-but lost."

Starchaser prides itself on the strong educational links it has developed with leading universities in the region. It runs programmes such as internships, student projects and work experience, with intake ranging from school pupils to PhD students.

The opportunities offered to schools within the UK by Starchaser are also unique. "We generally have a hands-on approach and want to get students interested so they can take home a very good insight not only into what we do but also what can be possible from engineering," says Bennett. Starchaser has been developing part of its business specifically towards educational outreach, with visits reaching around 400,000 students every year. "We go into schools with a real rocket and propulsion engineers and try to encourage kids into these subjects," he says.

Another area of interest for Starchaser is reusable launch systems. Reusable rockets would bring lower costs and this could see universities launching small scientific payloads on a much more frequent basis. "This will also help test and validate systems within the spacecraft whilst allowing collation of further flight data for later analysis," says Bennett. "Again, this goes back to our philosophy of build, test and develop step-by-step."

Despite the developments of the past few years, it will be some time before the masses get to take trips into space. But like the pioneers of the airline industry in the 1930s and 1940s, the space tourism industry has huge potential.

PE Publishing, courtesy of Professional Engineering magazine

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