[meteorite-list] Asteroid Deflection: Science Fiction or Reality?
From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 30 Sep 2015 13:59:51 -0700 (PDT)
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.
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."
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
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."
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."
julie.cohen at ucsb.edu
Received on Wed 30 Sep 2015 04:59:51 PM PDT