Fly Me To The Moon

"Hot air won't do the job," he continues, "so you must precool the air before it enters the compressor, a concept that had been lurking around since the 1960s." Bond conceived the idea of using the ultracold liquid hydrogen fuel as a heat sink to take the excess heat out of the incoming air and use some of the hot air to support fuel combustion. At the fringes of space, the dual-mode power plant would switch to a conventional rocket engine, drawing on the liquid hydrogen and a small supply of liquid oxygen to propel the winged craft into orbit at a final speed of Mach 25. _SciAm

The dream is to be able to walk outside one's house over to the neighborhood runway. Hop into a plane, and fly into space. Refuel in orbit, then on to the moon. Impossible? Yes, for now. But broken down, step by step, the problem is not insoluble. British company Reaction Engines Ltd. has secured a 1 million Euro grant to further develop its liquid hydrogen space plane propulsion engine, Sabre. The Sabre engine was developed for the Skylon pilotless space plane, but could be adopted for piloted ground launch-to-space vehicles. It is fueled by liquid hydrogen, plus either compressed air or liquid oxygen.

The hybrid propulsion concept was attractive enough that in the mid-1980s Britain's BAE Systems and Rolls-Royce seized on it for an SSTO space plane project called HOTOL (horizontal takeoff and landing). But after HOTOL was canceled in the late 1980s, Bond, Richard Varvill and John Scott-Scott established Reaction Engines to carry on. Bond serves as the firm's managing director, Varvill is technical director and chief designer, and Scott-Scott is engineering director.

Soon the team will begin a series of milestone ground tests using a scaled-down precooler unit and a Viper turbojet engine. If the trials are successful, they could open the way for full-scale development of the air-breathing rocket engine.

As currently envisioned, Skylon would cost an estimated $10 billion to develop, but Bond claims its operational cost per kilogram of orbital payload would be one fiftieth that of current vehicles. So far, the project has consumed about $7 million in private and public funds, and this week the European Space Agency kicked in another $1.25 million. "We hope to complete demonstrating the critical technologies in three years," Varvill states. After that, Reaction Engines will seek to establish a public–private partnership to build the prototype.

Pablo de Leon, Whalen's colleague at U.N.D., shares his co-worker's views: "The concept might work. If it does, Reaction Engines will reach an SSTO vehicle before anybody else." _SciAm

Okay. Realistically, you might want to dock the space plane at an orbiting Bigelow space station and transfer point, and take a moon shuttle on to Luna. The plane will be waiting for you when you get back from your lunar interlude, and will take you back to the neighborhood airstrip, and home.