Can Transporters Be Far Behind?
Two NASA astronauts
have suggested a new way to deflect an Earth-bound asteroid -- one
that wouldn't involve landing a spacecraft on the celestial body,
blowing it up with nuclear weapons, or in any other way subjecting
it to Bruce Willis.
Instead, the crew of the so-called "gravity tractor" would use
the spacecraft's thrusters to hover above the asteroid, and utilize
the gravitational attraction between the craft and the asteroid to
gradually pull it off course.
"You would use this small gravity force between the [spacecraft
and the asteroid] as your towline to basically pull this thing,"
said NASA astronaut Edward Lu, who along with colleague Stanley
Love devised the gravity tractor idea.
"If an asteroid is found to be at an impact trajectory with
Earth … you will have many decades of notice," said Lu to
National Geographic. "And it turns out that you only need to change
its velocity by a very small amount in order to prevent a
Indeed, the two astronauts maintain that, given about 20 years
notice, NASA could launch a gravity tractor spacecraft capable of
deflecting an asteroid 650 feet in diameter -- simply by towing it
into a new trajectory, a process expected to take about one
While lacking a certain excitement -- more along the lines of
the elegant space station docking scene in "2001," versus an
"Armaggedon"-style explosion -- the gravity tractor would likely be
a safer method than attempting to land on a tumbling asteroid,
blowing it up, or attaching a booster rocket pack to it --
alternate methods suggested in the past by scientists and
"Landing means dealing with a rough surface with poorly known
physical properties and somehow compensating for the asteroid's
rotation, which wants to whirl your thrust[ers] … around
like a lawn sprinkler," Love said. "Using gravity as a towline
frees you from those messy details."
Besides, blowing up an
asteroid -- or slamming a large spacecraft into one to break it
into smaller pieces -- are just "bad ideas," added Lu. "If you do
that, you better have a darn good idea where all those pieces are
Granted, the probability of a large asteroid slamming into our
planet is slim -- which makes now the perfect time to make plans
for such an event, said Love.
"In my office, we do not wait until the building is on fire to
conduct fire drills," the astronaut said. "Recent large natural
disasters, such as the tsunami in the Indian Ocean and the
hurricanes in our own country, underscore the value of being
prepared for an emergency."
While it's nothing to lose sleep over, we may soon have the
chance to test the gravity tractor concept.
99942 Apophis, a 1,000-foot asteroid scheduled to come within
about 19,000 miles of Earth in 2029, will have its orbit altered by
the event to the point it might -- might -- hit our planet when it
comes back around in 2036. (The odds are about 1 in 5,000.)
"If around 2013 we find out that it's going to hit, we could
[initiate] a very tiny change in [the asteroid's] orbit before
2029," Lu said.