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

passengers.
    To jump-start research in space elevators, NASA has encouraged several contests. A total of $2 million in prizes is awarded through NASA’s Space Elevator Games. According to the rules set down by NASA, to winthe Beam Power Challenge, you must create a device weighing no more than 50 kilograms that can climb up a tether at the speed of 2 meters per second for a distance of 1 kilometer. What makes this challenge so difficult is that the device cannot have fuel, batteries, or an electrical cord. The energy must be beamed to the device from the outside.
    I had a chance to see firsthand the enthusiasm and energy of engineers working on the space elevator and dreaming of claiming the prize. I flew to Seattle to meet young, enterprising engineers in a group called Laser-Motive. They had heard the siren call of NASA’s contest and then began to create prototypes that may one day activate the space elevator.
    I entered a large warehouse that they had rented to test out their ideas. On one side of the warehouse, I saw a powerful laser, capable of firing an intense beam of energy. On the other side of the warehouse, I saw their space elevator. It was a box about three feet wide, with a large mirror. The laser beam would hit the mirror and be deflected onto a series of solar cells that would convert the laser energy into electricity. This would trigger a motor, and the elevator car would gradually climb a short cable. In this way, you would not need electrical cables dangling from the space elevator to provide its energy. You would just fire a laser at the elevator from the earth, and the elevator would climb the cable by itself.
    The laser was so powerful, we all had to wear special goggles to protect our eyes. It took numerous trial runs, but they finally were able fire the laser and send the device climbing the cable. At least in theory, one aspect of the space elevator had been solved.
    Initially, the task was so difficult that no one won the prize. However, in 2009 LaserMotive claimed the prize. The contest took place at Edwards Air Force Base in the Mojave Desert in California. A helicopter flew over the desert, holding up a long cable. The LaserMotive team was able to make their elevator climb the cable four times in two days, with the best time being 3 minutes and 48 seconds. So all the hard work I had seen finally paid off for these young engineers.
    STARSHIPS
    By the end of the century, even despite recent setbacks in funding for manned space missions, scientists will likely have set up outposts on Marsand perhaps in the asteroid belt. Next, they will set their sights on an actual star. Although an interstellar probe is hopelessly beyond reach today, within 100 years it might become a reality.
    The first challenge is to find a new propulsion system. For a conventional chemical rocket, it would take about 70,000 years to reach the nearest star. For example, the two
Voyager
spacecrafts, launched in 1977, have set a world record for an object sent into deep space. They are currently about 10 billion miles into space but only a tiny fraction of the way to the stars.
    Several designs and propulsions systems have been proposed for an interstellar craft:
     
    • solar sail
    • nuclear rocket
    • ramjet fusion
    • nanoships
    I had a chance to meet one of the visionaries of the solar sail when I visited the NASA Plum Brook Station in Cleveland, Ohio. There, engineers have built the world’s largest vacuum chamber for testing space satellites. The chamber is truly cavernous: it is 100 feet across and 122 feet tall, large enough to contain several multistory apartment buildings and big enough to test satellite and rocket parts in the vacuum of space. Walking into the chamber, I felt overwhelmed by the enormity of the project. But I also felt privileged to be walking in the very same chamber where many of the United States’ landmark satellites, probes, and rockets have been tested.
    There, I met one of the leading proponents of the solar sail, NASA scientist Les Johnson. He told me that ever since he was a kid reading science fiction, he dreamed of building rockets that could reach the stars. Johnson has even written the basic textbook on solar sails. Although he thinks it might be accomplished within a few decades, he is resigned to the fact that an actual starship may not be built until long after he has passed away. Like the masons who built the great cathedrals of the Middle Ages, Johnson realizes that