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NEO Table

PHA Table

Asteroid Classifications

Asteroid Missions

Asteroid Deflection Techniques
Although there are many deflection techniques possible (see the
Resources section for a Website describing 10 of them), this Unit asked
students to consider only three: a Gravitational Tractor, the
Kinetic Impact Method, or a Nuclear Explosion. In Mission 4
students see the consequences of each choice.

Gravitational Tractors
Gravity pulls any two objects in space towards each other. Even a
very small object like a spacecraft pulls on a large object like an
asteroid, up to a specific size. A gravity tractor uses the mutual
gravity between a robotic spacecraft and an asteroid to slowly
accelerate the asteroid in the direction of the "hovering"
spacecraft. The data students examined on this method should
have led them to realize it would be ineffectual on the Atlas
asteroid, which is larger than the maximum 250 meters in size. If
chosen, they face a world where the asteroid was not deflected
and actually landed on the NASA desert base.

The Kinetic Impact Method
In this method, an attempt to directly alter the asteroid's momentum is
accomplished by sending a spacecraft to collide with it. This method is a
better choice than the gravity tractor because it works on a larger
asteroid and is less expensive than the nuclear explosion. Students who
select the Kinetic Impact Method see a world that averted the disaster
and has already turned their attention to other things.

Nuclear Explosion
Also a possibility for the large Atlas asteroid, this method is problematic
if the asteroid breaks into fragments in the explosion. Any fragment
larger than 35 meters across would not burn up in the atmosphere and
itself could impact Earth. In fact, in this Unit those fragments DO fall to
Earth, and turn out to be radioactive themselves. This choice turns out
to be the worst decision of the three, as the damage spread across
many areas of the world.