A decelerating "beamer" or aerobraking would bring it into Mars orbit. Transit time would be less than two weeks.
A precursor interstellar mission out to the Oort cloud of comets, one light-year away, would call for a 24-gigawatt 2-mile diameter antenna costing around $144 billion, Benford estimates. The payload would weigh 150 pounds, half of the weight being the half-mile diameter sail. After five hours of beaming the probe would be accelerated to 140,000 miles per hour.
A true starship, capable of reaching the neighboring Alpha Centauri system within 40 years at 1/10th the speed of light, would likely weigh several tons unless it made extensive use of nanotechnology. Former NASA Administrator Dan Goldin talked of reducing the size of interstellar probes to that of as soup can.
The killer is that 300 terawatts would need to be beamed from a 60-mile diameter antenna to accelerate this sucker! That's about 20 times the daily electric power consumption of the entire planet.
The probe would need to be accelerated rapidly to avoid vaporizing the sail. The acceleration would therefore be 50 times the force of gravity on Earth's surface, or 50G's – so don't plan on stowing away onboard, you'll be flattened like a pancake.
To borrow an idea from Carl Sagan's 1985 novel Contact, imagine a nearby civilization transmitting blueprints to us for building a practical beaming system. It would be used to launch a time-capsule probe to their star where their own beaming system would decelerate and capture it.
Such interstellar parcel packages might be the only practical way to exchange physical samples between neighboring extraterrestrial civilizations. We might send them the DNA of various species on Earth. Imagine replicating the San Diego Zoo on Alpha Centauri.
Editor's note: This article was originally published on March 20, 2012.
Image credits: NASA