Physics of the Future: How Science Will Shape Human Destiny and Our Daily Lives by the Year 2100

permafrost begins to melt, the planet would naturally continue to warm on its own.
    ECONOMIC BENEFIT?
    One should have no illusions that we will benefit immediately from an economic bonanza by colonizing the moon and Mars. When Columbus sailed to the New World in 1492, he opened the door to a historic economic wind-fall. Soon, the conquistadors were sending back huge quantities of gold that they plundered from Native Americans, and settlers were sending valuable raw materials and crops back to the Old World. The cost of sending expeditions to the New World was more than offset by the fabulous fortunes that could be made.
    But colonies on the moon or Mars are quite different. There is no air, liquid water, or fertile soil, so everything would have to be brought by rocket ship, which is prohibitively expensive.
    Furthermore, there is little military value to colonizing the moon, at least for the near term. This is because it takes three days on average to reach the moon from the earth or vice versa, but a nuclear war can be fought in just ninety minutes by intercontinental ballistic missiles. A space cavalry on the moon would not reach the battle on earth in time to make a difference. Hence, the Pentagon has not funded any crash program to weaponize the moon.
    This means that if we do initiate large-scale mining operations on other worlds, it will be for the benefit of space colonies, not for the earth. Colonists will extract the metals and minerals for their own use, since it would cost too much to transport them to earth. Mining operations in the asteroid belt would become economic only when we have self-sustaining colonies that can use these raw materials themselves, which won’t happen until late in this century or, more likely, beyond.
    SPACE TOURISM
    But when might the average civilian go into space? Some visionaries, like the late Gerard O’Neill of Princeton University, dreamed of a space colony as a gigantic wheel, including living units, water-purification plants, air-recycling units, etc., established to solve overpopulation on earth. But in the twenty-first century, the idea that space colonies would relieve the population problem is fanciful at best. For the majority of the human race, earth will be our only home for at least a century or more.
    However, there is one way in which the average person may realistically go into space: as a tourist. Some entrepreneurs, who criticize the enormous waste and bureaucracy of NASA, think they can drive down the cost of space travel using market forces. Already, Burt Rutan and his investors won the $10 million Ansari X Prize on October 4, 2004, by having launched SpaceShipOne twice within two weeks to just over 62 miles above the earth. SpaceShipOne is the first rocket-powered spacecraft to have successfully completed a privately funded venture into space. Development costs were about $25 million. Microsoft billionaire Paul Allen helped to underwrite the project.
    Now, with SpaceShipTwo, Rutan expects to begin tests to make commercial spaceflight a reality. Billionaire Richard Branson of Virgin Atlantic has created Virgin Galactic, with a spaceport in New Mexico and a longlist of people who will spend $200,000 to realize their dream of flying into space. Virgin Galactic, which will be the first major company to offer commercial flights into space, has already ordered five SpaceShipTwo rockets. If successful, this might drive down the cost of space travel by a factor of ten.
    SpaceShipTwo uses several methods to cut costs. Instead of huge booster rockets to carry the payload into space, Rutan places his spaceship atop an airplane, so that it can piggyback on a standard air-breathing plane. This way, you simply consume the oxygen in the atmosphere to reach high altitudes. Then, at about 10 miles above the earth, the spaceship separates from the airplane and turns on its rocket engines. Although the spaceship cannot orbit the earth, it has enough fuel to reach almost 70 miles above the earth, above most of the atmosphere, so passengers can see the sky turn purple and then black. Its engines are powerful enough to hit Mach 3, or three times the speed of sound (roughly 2,200 miles per hour). This is certainly not fast enough to put a rocket into orbit (you need to hit 18,000 miles per hour for that), but it is enough to take you to the edge of the atmosphere and the threshold of outer space. In the near future, perhaps a trip to space may cost no more than a safari in