System would destroy asteroids that threaten Earth
As an asteroid roughly half as large as a football field—and with energy equal to a large hydrogen bomb—readies for a fly-by of Earth on Friday, two California scientists are unveiling their proposal for a system that could eliminate a threat of this size in an hour. The same system could destroy asteroids 10 times larger than the one known as 2012 DA14 in about a year, with evaporation starting at a distance as far away as the Sun.
UC Santa Barbara physicist and professor Philip M. Lubin, and Gary B. Hughes, a researcher and professor from California Polytechnic State University, San Luis Obispo, conceived DE-STAR, or Directed Energy Solar Targeting of Asteroids an exploRation, as a realistic means of mitigating potential threats posed to the Earth by asteroids and comets.
"We have to come to grips with discussing these issues in a logical and rational way," said Lubin, who began work on DE-STAR a year ago. "We need to be proactive rather than reactive in dealing with threats. Duck and cover is not an option. We can actually do something about it and it's credible to do something. So let's begin along this path. Let's start small and work our way up. There is no need to break the bank to start."
Described as a "directed energy orbital defense system," DE-STAR is designed to harness some of the power of the sun and convert it into a massive phased array of laser beams that can destroy, or evaporate, asteroids posing a potential threat to Earth. It is equally capable of changing an asteroid's orbit –– deflecting it away from Earth, or into the Sun –– and may also prove to be a valuable tool for assessing an asteroid's composition, enabling lucrative, rare-element mining. And it's entirely based on current essential technology.
"This system is not some far-out idea from Star Trek," Hughes said. "All the components of this system pretty much exist today. Maybe not quite at the scale that we'd need—scaling up would be the challenge—but the basic elements are all there and ready to go. We just need to put them into a larger system to be effective, and once the system is there, it can do so many things."
The same system has a number of other uses, including aiding in planetary exploration.
In developing the proposal, Lubin and Hughes calculated the requirements and possibilities for DE-STAR systems of several sizes, ranging from a desktop device to one measuring 10 kilometers, or six miles, in diameter. Larger systems were also considered. The larger the system, the greater its capabilities.
For instance, DE-STAR 2—at 100 meters in diameter, about the size of the International Space Station—"could start nudging comets or asteroids out of their orbits," Hughes said. But DE-STAR 4—at 10 kilometers in diameter, about 100 times the size of the ISS –– could deliver 1.4 megatons of energy per day to its target, said Lubin, obliterating an asteroid 500 meters across in one year.
The speed of interplanetary travel—far beyond what is possible with chemical propellant rockets used today—could be increased with this sized system, according to Lubin. It could also power advanced ion drive systems for deep space travel, he said. Able to engage multiple targets and missions at once, DE-STAR 4 "could simultaneously evaporate an asteroid, determine the composition of another, and propel a spacecraft."
Larger still, DE-STAR 6 could enable interstellar travel by functioning as a massive, orbiting power source and propulsion system for spacecraft. It could propel a 10-ton spacecraft at near the speed of light, allowing interstellar exploration to become a reality without waiting for science fiction technology such as "warp drive" to come along, Lubin said.
"Our proposal assumes a combination of baseline technology—where we are today—and where we almost certainly will be in the future, without asking for any miracles," he explained. "We've really tried to temper this with a realistic view of what we can do, and we approached it from that point of view. It does require very careful attention to a number of details, and it does require a will to do so, but it does not require a miracle."
Recent and rapid developments in highly efficient conversion of electrical power to light allow such a scenario now, Lubin said, when just 20 years ago it would not have been realistic to consider.
"These are not just back-of-the-envelope numbers," Hughes concurred. "They are actually based on detailed analysis, through solid calculations, justifying what is possible. And it's all available under current theory and current technology.
"There are large asteroids and comets that cross the Earth's orbit, and some very dangerous ones going to hit the Earth eventually," he added. "Many have hit in the past and many will hit in the future. We should feel compelled to do something about the risk. Realistic solutions need to be considered, and this is definitely one of those."
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Provided by: University of California - Santa Barbara
Could a laser weapon save earth from killer asteroids?
-by Tomasz Nowakowski, Astrowatch.net
Potentially hazardous asteroids are still looming large in the minds of scientists engaged in planetary defense issues. Numerous strategies describing deflection of near-Earth objects (NEOs) have been proposed, including methods employing kinetic impactors, robotic mining, and gravity tractors. However, one of the concepts has recently received attention as one of the most serious proposals.
The project, named DE-STAR (Directed Energy System for Targeting of Asteroids and exploRation), envisions a large phased-array laser in Earth orbit to deflect asteroids, comets, and other NEOs endangering the planet. There is also a much smaller, though similar system being considered, called DE-STARLITE, that could travel alongside the target, slowly deflecting it from nearby over a long period.
According to the authors of these proposals, their goal was to create an orbital planetary defense system capable of heating the surface of potentially hazardous objects to the point of vaporization. They emphasize that vaporization on the surface of an object continually ejects vaporized material, creating a reactionary force that pushes the object into a new path. This can be accomplished by lasers deployed on spacecraft stationed near the asteroid.
The system should be capable of projecting a laser at a distant asteroid with sufficient flux to heat a spot on the surface and vaporize solid rock. Currently, high-powered lasers deliver sufficient energy density to melt and vaporize any known material.
(a) Concept diagram of an orbiting DE-STAR engaged in multiple tasks including asteroid diversion, composition analysis, and long-range spacecraft power and propulsion. (b) Visualization of a laser beam with relevant physical phenomenon included at a flux of about 10 MW/m2. Credit: Kosmo et al.
"Generally speaking, the technology is available today. The main challenge with building a full DE-STAR is the necessary scale to be effective," Qicheng Zhang of the University of California, Santa Barbara, one of the authors of the project, told Astrowatch.net.
Zhang and his colleagues claim that if DE-STAR had a 330-feet-wide phased laser array, it could divert volatile-laden asteroids 330 feet in diameter by initiating engagement at about two million miles. However, DE-STARLITE, being a much smaller and less expensive system, is the more practical option. For instance, a 20 kW version of DE-STARLITE operating for 15 years could deflect an Apophis-size (1,066 feet) asteroid at a distance equal to Earth's diameter. A 1 MW version could deflect all known threats up to 1,640 feet in diameter with five-year laser activity.
"The bigger the NEO, the longer the time needed. The bigger the laser, the shorter the time needed. With a very small 20 kW DE-STARLITE, a 300-meter-wide (1,000 foot) asteroid can be deflected in 15 years. Smaller asteroids can be deflected in under a year, after the spacecraft's arrival at the asteroid," Zhang said.
According to the scientists, DE-STARLITE would be ineffective at deflecting targets on short notice due to the time required for transit to the target asteroid. Thus the DE-STAR system seems to be a last line of defense on short notice.
A full stand-off system like DE-STAR is still considered as a possibility for the more distant future for its ability to rapidly respond to identified threats. It could also provide one of the few options for defense against long-period comets, which modern technology is often incapable of reaching by spacecraft.
An orbiting DE-STAR of adequate size would have the capability of reacting to small or moderately sized objects that are discovered with limited time to react. However, the researchers note that actual effectiveness of a deflection mission depends strongly on the target. A mission optimized for one target may be ineffective when applied to another, even one of the same size and composition.
"It depends on the exact circumstances. If, say, a 100-meter-wide asteroid were found today on a collision course with Earth next week, directed energy would not be a viable solution as that would require a very large laser array that would be far bigger than an equally effective single-use impactor or explosive. If, on the other hand, we find that same asteroid 30 years before impact, directed energy would be very effective, even with 10 kW lasers which are far below the power of many lasers in possession by the U.S. military today," Zhang explained.
The concepts of DE-STAR and DE-STARLITE show that the directed energy method could be a promising technology for planetary defense. It could save our planet from small- to mile-class hazardous objects. With the recent technology advancements it is now feasible to consider the methods based on laser ablation as one of the most relevant and effective techniques of asteroid deflection.
Explore further: System would destroy asteroids that threaten Earth
Provided by: Astrowatch.net
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