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The Asteroid Threat: Playing Asteroids for Real

Part 4 of a series

At the turn of the millennium, as the incumbent alumni association president at Colorado College, I contributed a letter for a time capsule that will be opened New Year’s Eve, 2099.  The letter described various aspects of student life during the time in the late 1970s that I attended the liberal arts school in Colorado Springs, Colo., including the fact that students often whiled away their leisure hours playing the new video arcade game Asteroids, in which the object of the participant was to shoot and destroy these menacing space rocks.

“If you only have weeks or months of notice there is really nothing you can do,” says Lu, “because the velocity change required increases greatly the closer you get to the actual impact point.  And with short notice it [asteroid deflection] is essentially impossible with any kind of current technology including nuclear.  That’s why you need early detection so you have many years of notice.  Everyone needs to understand that all the deflection technology in the world is useless until you find the asteroid first.”

Now, on the heels of the Feb. 15, 2013 meteor explosion over the Russian city of Chelyabinsk, a question increasingly being asked in space policy circles is will there come a time, perhaps before that time capsule is opened up, when we have to shoot at, or deflect, an asteroid or comet for real?

 

If the Asteroid’s Coming in Three Weeks…Pray

A possible answer to this question comes from former astronaut Ed Lu, the Chief Executive of the The B612 Foundation – named for the home asteroid of the hero in Antoine de Saint-Exupery’s The Little Prince – the northern California group attempting to build the privately financed “Sentinel” asteroid-detecting space telescope.  The Foundation originated following an informal meeting of scientists at NASA’s Johnson Space Center in Houston, Texas in October 2001, at which a potential asteroid deflection mission was discussed.  And Lu, who organized that meeting, believes there is a 30 percent chance in the next 100 years that we will discover a threatening asteroid headed our way about the size of the one that exploded over Chelyabinsk, or “if it’s coming in more steeply,” an asteroid big enough to kill a city.  And when asked in a March House Science, Space and Technology Committee hearing about potential killer asteroids, NASA Administrator Charles Bolden famously said, “From the information we have, we don’t know of an asteroid that will threaten the population of the United States.  But if it’s coming in three weeks…pray.”

Asteroid Threat: Inner Solar System

The inner Solar System, from the Sun to Jupiter. The asteroid belt is the white donut-shaped cloud, the Hildas (the orange “triangle” just inside the orbit of Jupiter), the Jupiter trojans (green), and the near-Earth asteroids. The asteroids that lead Jupiter are called the “Greeks” and the trailing group are called the “Trojans” The image is looking down on the ecliptic plane as it would have been seen on Aug. 14, 2006. Image by Mdf via wikipedia

 

No Hollywood Endings

Wait a minute! Didn’t Bruce Willis and Ben Affleck already team up to save the planet from a Texas-sized asteroid, set to impact Earth just 18 days after its discovery, in the 1998 blockbuster Armageddon, using a well placed subsurface nuclear device?

Alas, Ed Lu believes Bolden essentially is correct that no movie heroics would work in that short a time frame.  “If you only have weeks or months of notice there is really nothing you can do,” says Lu, “because the velocity change required increases greatly the closer you get to the actual impact point.  And with short notice it [asteroid deflection] is essentially impossible with any kind of current technology including nuclear.  That’s why you need early detection so you have many years of notice.  Everyone needs to understand that all the deflection technology in the world is useless until you find the asteroid first.”

Former astronaut Thomas Jones, who chairs the Committee on Near Earth Objects (NEO) for the Association of Space Explorers, a global organization of astronauts and cosmonauts, and who co-chaired a 2010 NASA Advisory Council Task Force on Planetary Defense, adds this perspective: “What Charlie [Bolden] was referring to is if your search discovered something three weeks out, there’s realistically no time to do anything about it. It’s not something that the military can do anything about or NASA.  If you launch on short notice a nuclear explosive to deflect it, you would probably do more harm than good because you won’t have time to develop any kind of effective technique. All you’re going to be trying to do is a brute force deflection in a very imprecise way that might cause more problems than not.  So yes, you need the space search so that you can do a very measured and highly confident deflection mission.” Beyond pragmatic concerns, there is also a legal issue. The 1996 Comprehensive Nuclear-Test-Ban Treaty technically bans nuclear weapons in space. Thus, any solution of this nature would in theory have to be approved through an international agreement.

 

Dealing With Keyholes in Deflecting Asteroids

Experts point out that even if a killer asteroid is deflected in the nick of time to avoid a collision with Earth, if not done correctly, we are in jeopardy of only postponing our day or reckoning. Simply put, Earth’s gravity will slow slightly the orbital velocity of an asteroid passing just in front of our planet, and speed up slightly an asteroid passing behind Earth. The closer to the Earth the asteroid passes, the more its orbit is changed. If an asteroid deflection mission directs a large object into one of these “gravitational keyholes,” then it may be headed toward a collision course with Earth during some future orbital encounter.

“Any real deflection has to involve at least two components,” says Ed Lu. “The first of which is the primary deflection, to keep it from hitting the Earth. And the second part is a verification that the deflection worked, and a fine tuning if necessary to make sure that it isn’t going into a keyhole and come back a few years later. And there are a lot of those keyholes, hundreds of them. With the kinetic impactors or even a nuclear device, you don’t really know what the end effect is going to be until after you measure it. And you must understand that primary deflections in general are not very controlled.”

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Edward Goldstein has more than 20 years' experience in the U.S. space community. From...