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PHYSICS OF THE IMPOSSIBLE
One proposal is to install a rail gun on the moon. Outside the
Earth's atmosphere, a rail gun's projectile could speed effortlessly
through the vacuum of outer space. But even then the enormous accelerations generated by a rail gun might damage the payload. Rail guns
in some sense are the opposite of laser sails, which build up their ultimate speed gently over a long period of time. Rail guns are limited because they pack so much energy into such a small space.
Rail guns that can fire objects to nearby stars would be quite expensive. In one proposal the rail gun would be built in outer space, extending two-thirds of the distance from Earth to the sun . It would store
solar energy from the sun and then abruptly discharge that energy into
the rail gun, sending a 10-ton payload at one-third the speed of light,
with an acceleration of 5000 g's. Not surprisingly, only the sturdiest robotic payloads would be able to survive such huge accelerations.
THE DANGERS OF SPACE TRAVEL
Of course, space travel is no Sunday picnic. Enormous dangers await
manned flights traveling to Mars, or beyond. Life on Earth has been
sheltered for millions of years: The planet's ozone layer protects the
Earth from ultraviolet rays, its magnetic field protects against solar
flares and cosmic rays, and its thick atmosphere protects against meteors that burn up on entry. We take for granted the mild temperatures
and air pressures found on the Earth. But in deep space, we must face
the reality that most of the universe is in turmoil, with lethal radiation
belts and swarms of deadly meteors.
The first problem to solve in extended space travel is that of
weightlessness. Long-term studies of weightlessness by the Russians
have shown that the body loses precious minerals and chemicals in
space much faster than expected. Even with a rigorous exercise program, after a year on the space station, the bones and muscles of Russian cosmonauts are so atrophied that they can barely crawl like
babies when they first return to Earth. Muscle atrophy, deterioration of
PHYSICS OF THE IMPOSSIBLE
One proposal is to install a rail gun on the moon. Outside the
Earth's atmosphere, a rail gun's projectile could speed effortlessly
through the vacuum of outer space. But even then the enormous accelerations generated by a rail gun might damage the payload. Rail guns
in some sense are the opposite of laser sails, which build up their ultimate speed gently over a long period of time. Rail guns are limited because they pack so much energy into such a small space.
Rail guns that can fire objects to nearby stars would be quite expensive. In one proposal the rail gun would be built in outer space, extending two-thirds of the distance from Earth to the sun . It would store
solar energy from the sun and then abruptly discharge that energy into
the rail gun, sending a 10-ton payload at one-third the speed of light,
with an acceleration of 5000 g's. Not surprisingly, only the sturdiest robotic payloads would be able to survive such huge accelerations.
THE DANGERS OF SPACE TRAVEL
Of course, space travel is no Sunday picnic. Enormous dangers await
manned flights traveling to Mars, or beyond. Life on Earth has been
sheltered for millions of years: The planet's ozone layer protects the
Earth from ultraviolet rays, its magnetic field protects against solar
flares and cosmic rays, and its thick atmosphere protects against meteors that burn up on entry. We take for granted the mild temperatures
and air pressures found on the Earth. But in deep space, we must face
the reality that most of the universe is in turmoil, with lethal radiation
belts and swarms of deadly meteors.
The first problem to solve in extended space travel is that of
weightlessness. Long-term studies of weightlessness by the Russians
have shown that the body loses precious minerals and chemicals in
space much faster than expected. Even with a rigorous exercise program, after a year on the space station, the bones and muscles of Russian cosmonauts are so atrophied that they can barely crawl like
babies when they first return to Earth. Muscle atrophy, deterioration of