Spaceplanes to the Moon

The fully mature spaceplane of the future will have the ability to take off from any spaceport on Earth, cruise into low orbit, refuel, and fly its passengers and cargo to the Moon. Its cargo may comprise not only bulk dry goods and supplies for a Moon base, but also precious rocket fuel for the base's day-to-day operations. The mature spaceplane would best be utilized in this way, serving as space tanker both initially to and eventually from the Moon.

in his book Return to the Moon. Apollo 17 geologist-astronaut Harrison H. Schmitt reveals that production of helium-3 from Lunar soil will release a host of other elements and compounds, including helium-4, nitrogen, carbon monoxide, methane, "large amounts of hydrogen," and water. Helium-3, which is extremely rare on Earth but is common on the Moon because of the Solar wind, could be used in fusion plants to power the energy demands of the twenty-first century.5 But consider the list of by-products: "Large amounts of hydrogen," the best rocket fuel in the Universe; water, which can either be consumed or hydrolyzed into hydrogen and oxygen - the best rocket propellant combination in the Universe; methane, another rocket fuel or source of energy, in any case; and nitrogen, an inert element that can be combined with oxygen to provide breathable air.

Now the pieces of the puzzle are beginning to fall into place. The Moonplane, with its enormous propellant tanks and modest cabin, can be filled with Lunar rocket pro-pellant produced as by-products of helium-3 production. Transporting these precious fluids from the Moon to low Earth orbit requires only a small fraction of the energy

• - ) 9C~X9 ^ ^^ . ® X-36 ^^^^^^

Fig. 4.11 The tail-less X-36 parked on the ramp at Dryden Flight Research Center, California, in 1997. Will future spacecraft bound for the Moon look like this? (courtesy NASA)

Fig. 4.11 The tail-less X-36 parked on the ramp at Dryden Flight Research Center, California, in 1997. Will future spacecraft bound for the Moon look like this? (courtesy NASA)

that it would take to transport the same cargo in the opposite direction, because Earth lies at the bottom of its own gravity well. Gravitationally speaking, it is "downhill" from the Moon. Moreover, the spaceplane is ideally suited to make this downhill run, because it has the unique ability to decelerate in Earth's atmosphere, emerge back into the vacuum of space, and settle into a low Earth parking orbit. Propellants are delivered to the orbital depot, and the spaceplane reenters the atmosphere - this time in earnest - and returns to its home spaceport.

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