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

support; and most important, don’t have to come back.
    Back in 1969, it seemed as if our astronauts were poised to explore the solar system. Neil Armstrong and Buzz Aldrin had just walked on the moon, and already people were dreaming about going to Mars and beyond. It seemed as if we were on the threshold of the stars. A new age was dawning for humanity.
    Then the dream collapsed.
    As science fiction writer Isaac Asimov has written, we scored the touchdown, took our football, and then went home. Today, the old Saturn booster rockets are idling in museums or rotting in junkyards. An entire generation of top rocket scientists was allowed to dissipate. The momentum of the space race slowly dissipated. Today, you can find reference to the famous moon walk only in dusty history books.
    What happened? Many things, including the Vietnam War, the Watergate scandal, etc. But, when everything is boiled down, it reduces to just one word: cost.
    We sometimes forget that space travel is expensive, very expensive. It costs $10,000 to put a pound of anything just into near-earth orbit. Imagine John Glenn made of solid gold, and you can grasp the cost of space travel. To reach the moon would require about $100,000 per pound. And to reach Mars would require about $1,000,000 per pound (roughly your weight in diamonds).
    All this, however, was covered up by the excitement and drama of competingwith the Russians. Spectacular space stunts by brave astronauts hid the true cost of space travel from view, since nations were willing to pay dearly if their national honor was at stake. But even superpowers cannot sustain such costs over many decades.
    Sadly, it has been over 300 years since Sir Isaac Newton first wrote down the laws of motion, and we are still dogged by a simple calculation. To hurl an object into near-earth orbit, you have to send it 18,000 miles per hour. And to send it into deep space, beyond the gravity field of the earth, you have to propel it 25,000 miles per hour. (And to reach this magic number of 25,000 miles per hour, we have to use Newton’s third law of motion: for every action, there is an equal and opposite reaction. This means that the rocket can go rapidly forward because it spews out hot gases in the opposite direction, in the same way that a balloon flies around a room when you inflate it and then let it go.) So it is a simple step from Newton’s laws to calculating the cost of space travel. There is no law of engineering or physics that prevents us from exploring the solar system; it’s a matter of cost.
    Worse, the rocket must carry its own fuel, which adds to its weight. Airplanes partially get around this problem because they can scoop oxygen from the air outside and then burn it in their engines. But since there is no air in space, the rocket must carry its own tanks of oxygen and hydrogen.
    Not only is this the reason space travel is so expensive, it is also the reason we don’t have jet packs and flying cars. Science fiction writers (not real scientists) glamorized the day when we would all put on jet packs and fly to work, or go on a Sunday day trip blasting off in our family flying car. Many people became disillusioned by futurists because these predictions never came to pass. (That is why we see a rash of articles and books with cynical titles like
“Where’s My Jetpack?”
) But a quick calculation shows the reason. Jet packs already exist; in fact, the Nazis used them briefly during World War II. But hydrogen peroxide, the common fuel used in jet packs, quickly runs out, so a typical flight in a jet pack lasts only a few minutes. Also, flying cars that use helicopter blades burn up an enormous amount of fuel, making them far too costly for the average suburban commuter.
    CANCELING THE MOON PROGRAM
    Because of the enormous cost of space travel, currently the future of the manned exploration of space is in flux. Former president George W. Bushpresented a clear but ambitious plan for the space program. First, the space shuttle would be retired in 2010 and replaced in 2015 by a new rocket system called Constellation. Second, astronauts would return to the moon by 2020, eventually setting up a permanent manned base there. Third, this would pave the way for an eventual manned mission to Mars.
    However, the economics of space travel have changed significantly since then, especially because the great recession has drained funds for future space missions. The Augustine Commission report, given to