The private British SF-01 (Fig. 12.6) is in many ways the most intriguing of the currently contemplated spaceplane concepts. It is the largest design among the suborbital vehicles, carries the most passengers, costs the least to develop, charges little, is cheap to operate, and does not pollute the planet. It is still early in the maturation process and will likely evolve over time, but here are the basic facts as of October 2007.
The Spacefleet Project, based in southern England, plans to build a fleet of three environmentally friendly spaceplanes powered by liquid hydrogen and liquid oxygen. Not only are these the best rocket fuels around, but they can be produced by electrolysis of water using a solar photovoltaic array and/or wind energy. In this way, producing the propellants is a perfectly clean process, as is burning them in the engines, since the only combustion product is water vapor. The Spacefleet Project claims that its spacecraft is the only one under development known to inject zero carbon emissions into the atmosphere. Furthermore, production of these clean, energetic propellants is free and sustainable once the equipment is up and running.
The SF-01 has four LOX/LH2 four-chamber rocket engines with a mixture ratio of 7 to 1, a thrust per engine of 150 kN, a specific impulse of 350 s, and a burn time of 125 s. The titanium hull measures 14 x 14 x 3 m, with the height increasing to 6 m when the landing gear is lowered. The final design may include turbojet engines, but this is still under review. SF-01 carries 56 m3 of high-energy propellants, enabling it
to take no less than eight passengers and two pilots to an apogee of 340 km after launch from an inclined ramp at the spaceport. Passengers will experience a maximum of 2.4 G during the 2-min burn of the rockets, which cut off at 140 km. They will enjoy a full min of weightlessness as the spaceplane soars to the same altitude as the International Space Station. This is nearly three times the height reached by other space tourist vehicles, a factor that should increase passenger excitement and satisfaction significantly. Similar to other spaceplanes, it will glide back and land on the spaceport runway after each spaceflight. The SF-01 is also able to make intercontinental "point-to-point" flights, deploy small satellites, or carry scientific payloads in its large payload bay, with appropriate modifications (see also Fig. 12.7).
The development project is expected to take 3 years and cost no more than €260 M, finishing with delivery of three vehicles. The electrolysis plant should cost another €150 M, but thereafter should be cheap to operate. The company is now actively seeking funding.
Spacefleet is well-placed to gain the experience necessary for future orbital refueling operations, one of the keys to future spaceflight. The project scientist and managing director is Dr. Raymond D. Wright, an electrochemist with a quarter-century of experience in the British electrical industry and founder of Spacefleet, Ltd. He is therefore well qualified to head up the project. Ticket prices are projected to be a competitive $120,000, little more than half what much of the competition is charging.4
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