STARSHIPS 159
a suborbital sail also failed back in 2001.) But in February 2006 a 15-meter solar sail was sent successfully into orbit by the Japanese M-V rocket,
although the sail opened incompletely.
Although progress in solar sail technology has been painfully
slow, proponents of the solar sail have another idea that might take
them to the stars: building a huge battery of lasers on the moon that
can fire intense beams of laser light at a solar sail, enabling it to coast
to the nearest star. The physics of such an interplanetary solar sail are
truly daunting. The sail itself would have to be hundreds of miles
across and constructed entirely in outer space. One would have to
build thousands of powerful laser beams on the moon, each capable of
firing continuously for years to decades. (In one estimate, it would be
necessary to fire lasers that have one thousand times the current total
power output of the planet Earth.)
On paper a mammoth light sail might be able to travel as fast as
half the speed of light. It would take such a solar sail only eight years
or so to reach the nearby stars. The advantage of such a propulsion
system is that it could use off-the-shelf technology. No new laws of
physics would have to be discovered to create such a solar sail. But the
main problems are economic and technical. The engineering problems in creating a sail hundreds of miles across, energized by thousands of powerful laser beams placed on the moon, are formidable,
requiring a technology that may be a century in the future. (One problem with the interstellar solar sail is coming back. One would have to
create a second battery of laser beams on a distant moon to propel the
vessel back to Earth. Or perhaps the ship could swing rapidly around
a star, using it like a slingshot to get enough speed for the return voyage. Then lasers on the moon would be used to decelerate the sail so it
could land on the Earth.)
RAMJET FUSION
My own favorite candidate for getting us to the stars is the ramjet fusion engine. There is an abundance of hydrogen in the universe, so a
a suborbital sail also failed back in 2001.) But in February 2006 a 15-meter solar sail was sent successfully into orbit by the Japanese M-V rocket,
although the sail opened incompletely.
Although progress in solar sail technology has been painfully
slow, proponents of the solar sail have another idea that might take
them to the stars: building a huge battery of lasers on the moon that
can fire intense beams of laser light at a solar sail, enabling it to coast
to the nearest star. The physics of such an interplanetary solar sail are
truly daunting. The sail itself would have to be hundreds of miles
across and constructed entirely in outer space. One would have to
build thousands of powerful laser beams on the moon, each capable of
firing continuously for years to decades. (In one estimate, it would be
necessary to fire lasers that have one thousand times the current total
power output of the planet Earth.)
On paper a mammoth light sail might be able to travel as fast as
half the speed of light. It would take such a solar sail only eight years
or so to reach the nearby stars. The advantage of such a propulsion
system is that it could use off-the-shelf technology. No new laws of
physics would have to be discovered to create such a solar sail. But the
main problems are economic and technical. The engineering problems in creating a sail hundreds of miles across, energized by thousands of powerful laser beams placed on the moon, are formidable,
requiring a technology that may be a century in the future. (One problem with the interstellar solar sail is coming back. One would have to
create a second battery of laser beams on a distant moon to propel the
vessel back to Earth. Or perhaps the ship could swing rapidly around
a star, using it like a slingshot to get enough speed for the return voyage. Then lasers on the moon would be used to decelerate the sail so it
could land on the Earth.)
RAMJET FUSION
My own favorite candidate for getting us to the stars is the ramjet fusion engine. There is an abundance of hydrogen in the universe, so a