[meteorite-list] Asteroid Deflection: Science Fiction or Reality?

[Ron Baalke]

http://www.news.ucsb.edu/2015/015844/asteroid-deflection-science-fiction-or-reality 


Asteroid Deflection: Science Fiction or Reality?

An astrophysics research group experimentally confirms its theories about 
the manipulation of asteroids and photon propulsion
By Julie Cohen
UC Santa Barbara
August 27, 2015 

It's the ultimate science fiction: The immense power of the sun is harnessed 
and converted into a massive phased array of laser beams that have the 
potential to intercept and deflect asteroids before they smash into Earth.

But in this case, fiction may actually be closer to reality. DE-STAR, 
or Directed Energy System for Targeting of Asteroids and exploRation, 
the brainchild of UC Santa Barbara physicist Philip Lubin and Gary B. 
Hughes, a researcher and professor at California Polytechnic State University, 
San Luis Obispo, is designed to do exactly that.

And that's not all. The DE-STAR system could be leveraged for many other 
uses, such as stopping the rotation of a spinning asteroid and achieving 
relativistic propulsion. Now, students in Lubin's Experimental Cosmology 
Group have produced graphic demonstrations of this and other possible 
functions - albeit on a much smaller scale in the lab.

Deflecting Asteroids

To simulate a laser's ability to deflect an asteroid, Travis Brashears 
led a group of students in tests that simulate space conditions. Using 
basalt - the composition of which is similar to known asteroids - they 
directed a laser onto the basalt target until it glowed white hot - a 
process called laser ablation, which erodes material from the sample. 
This changes the object's mass and produces a "rocket engine" using the 
asteroid itself as the propellant. In space, this would be powerful enough 
to alter its course.

"What happens is a process called sublimation or vaporization, which turns 
a solid or liquid into a gas," explained Brashears, now a freshman at 
UC Berkeley who started working in the lab during high school as part 
of UCSB's Research Mentorship Program. 'That gas causes a plume cloud 
- mass ejection - which generates an opposite and equal reaction or thrust 
- and that's what we measure."

De-Spinning Asteroids

Then the team simulated a spinning asteroid using basalt to determine 
whether they could slow, stop and change its rotation direction. They 
used magnets to spin the basalt and then directed the laser in the opposite 
direction to slow the rotation.

"Our video shows the basalt sample slowing down, stopping and changing 
direction and then spinning up again," said Brashears. "That's how much 
force we're getting. It's a nice way to show this process and to demonstrate 
that de-spinning an asteroid is actually possible as predicted in our 
papers."

According to Lubin, a professor of physics at UCSB, manipulating the speed 
of a spinning asteroid offers another important possibility in space: 
the ability to explore, capture and mine asteroids. This is something 
NASA aims to do with its Asteroid Redirect Mission. The mission - which 
remains theoretical - is intended to visit a large near-Earth asteroid, 
collect and return a boulder from its surface and possibly redirect the 
asteroid into a stable orbit around the moon.

"All asteroids rotate; it's just a question of relative to whom and how 
fast," explained Lubin. "To mine an asteroid, it needs to be moving slowly 
enough so you can capture it. Our lab experiments show very graphically 
a practical way to de-spin or redirect an asteroid. It's a vivid demonstration 
that the technique works very well."

Photon Propulsion

In addition, the students explored photon propulsion, which is key to 
the group's latest project, DEEP-IN, or Directed Energy Propulsion for 
Interstellar exploratioN. The DEEP-IN concept relies on photon propulsion, 
whereby thrust from photons emitted from the laser array could be used 
to propel a spacecraft. This allows for the possibility of relativistic 
flight - speeds approaching the speed of light - for the small spacecraft 
required for future interstellar missions.

The team also tested a photon recycler, a device that reuses photons from 
the laser by shining them on a reflector cavity. "We have a second mirror 
at some distance away that bounces the photons back and forth like a ping-pong 
ball onto the spacecraft reflector." Brashears said. "In effect, we're 
recycling these photons to achieve a force multiplication that allows 
the vehicle to go even faster. So far, with a simple implementation, we 
have achieved an amplification factor of five. Much more is possible with 
refinement. This works as predicted, though implementing it into the full 
flight system will be complex."

Contact Info: 

Julie Cohen
(805) 893-7220
julie.cohen at ucsb.edu