31 Jan. 2011

 

Deflecting NEOs with solar sails

 

Near Earth Objects (asteroids that have orbits bringing them dangerously close to Earth) are receiving ever more attention, especially after recent impacts on Jupiter.
There are two possible ways to avoid the impact of a body with a dangerous orbit: the first is to bomb the object to try and destroy it, but this would have an unpredictable outcome, the second is to try to deviate it so it moves into a less threatening orbit.
At the 73rd Annual Meeting of the International Meteoritical Society, an interesting implementation of this second method was presented by a team of researchers from the New York City College of Technology (including Gregory L. Matloff, Lufeng Leng and Thinh Lê, pictured). They proposed to deviate NEOs by generating jets of material on their surface, similar to those found on cometary nuclei.
In order to produce these jets, an area of the asteroid must be subjected to intense heating, something that could be achieved by solar collectors, made of huge metallic sails (ten times thinner than a hair) positioned so as to collect and concentrate solar radiation onto the surface.
By flying alongside their target for several months, these reflectors could heat a part of the asteroid's surface to the point of generating jets of heated material. In order for this to work however, it is essential to understand to what depth the material needs to be heated; too deep, and the result would simply be to warm the asteroid, without creating any jets.
From the laboratory experiments carried out by the City Tech team, using red and green lasers and Allende meteorite samples (top right in photo), it turns out that the heat needs to be deposited very near the surface, around a tenth of a millimetre. This should create a controllable jet whose effect, over time, would be to deviate the NEOs trajectory, hopefully by just enough to avoid a collision.
Although the method is untested, there are those who think the method should be applied to the NEO Apophis, before its close approach to Earth in 2029, to avoid any unexpected orbital variations that could render its 2036 return more dangerous.

 

by Michele Ferrara & Marcel Clemens

credit: New York City College of Technology, Michele Forsten