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Laser “tractor beams” to tidy up space junk
natural motion games
TECHNOLOGY
Steer space junk out of Earth’s orbit with a laser WITH Earth’s orbit cluttered with dead satellites, discarded rocket boosters and other space junk, ways to prevent the accumulation of such debris are desperately needed. How about using a tractor beam to simply steer future junk aside, says space-flight engineer John Sinko of Nagoya University, Japan. Sinko’s idea is based on an experimental type of spacecraft engine called a laser thruster. Inside these motors, laser pulses fired into a mass of solid propellant cause a jet of material to be released, pushing the craft in the opposite direction. Sinko realised that the laser did not necessarily have to be on the same craft. “These on-board motors
“A spacecraft could fire a low-power laser beam at another craft to steer it from a distance” could also be targeted remotely by lasers for tractor beaming,” he says. He has designed a series of laser thrusters that can be activated in this way. A spacecraft fitted with a laser would fire a low-power beam at a thruster fitted on another craft to attract, repel or steer it in another direction. Pushing a spacecraft away is a relatively simple matter, but more complex designs using mirrors are
needed to use a beam to tug one towards the laser (see diagram). Combining those designs could allow full control in any direction, says Sinko. He imagines spacecraft being fitted with remotely operated thrusters before launch, so that once they reach the end of their lives it is simple to alter their orbit or even shove them into the atmosphere to burn up – even if they have lost all power (Journal of Propulsion and Power, DOI: 10.2514/1.46037). Tractor beams could be fired from up to 100 kilometres away, says Sinko, either from a spacecraft in orbit or a mirror in space redirecting a beam from Earth. “It’s an interesting idea that could work in principle,” says Richard Holdaway, director of space science technology at the Rutherford Appleton Laboratory in Didcot, UK. Keeping a laser beam accurately trained on a distant motor would be a challenge, he adds, “but perhaps not an insurmountable one”. Sinko hopes to test one of his tractor beams on a 10-kilogram satellite within a few years. He is not alone in trying to develop such technology: a team at the Research Institute for Complex Testing of Optoelectronic Devices and Systems in Sosnovy Bor, Russia, is working on similar ideas. Paul Marks n
Making space in space Satellites fitted with laser thrusters could be controlled remotely with low-power lasers to manoeuvre them out of Earth’s orbit
PUSHING
PULLING
INCOMING LASER BEAM
INCOMING LASER BEAM
EXHAUST
PROPELLANT PROPELLANT SATELLITE SURFACE
MIRROR
THRUST
THRUST
20 | NewScientist | 1 May 2010
THRUST
EXHAUST
–So real it hurts–
Survival of the fittest makes for more lifelike animations MONSTERS and aliens that move more realistically than ever before are coming soon to a screen near you. It’s all down to an animation technique first used to “evolve” the most lifelike interaction between human characters and their surroundings through trial and error. NaturalMotion of Oxford, UK, whose technique was used in the films Troy and Poseidon, has now shown that artificial evolution can equally be applied to non-human body shapes – for instance, bipedal monsters. “It’s equivalent to me waking up in a child’s body and being able to balance and look natural straight away,” says Torsten Reil, the firm’s CEO. State-of-the-art animation for non-human film characters usually involves filming real actors wearing motion-capture sensors. Then artwork of a monster, say, is mapped onto the footage and made to move using these sensors as a guide. Computer games use this technique but it is not ideal because a number of set sequences must be applied in almost all situations.
The team at NaturalMotion took a different approach. They began with 100 identical virtual skeletons, complete with simulated muscles and motor nerves. Then they attributed random values to the strength of connections between key motor nerves in each individual and made them perform a task, such as walking. Those that walked furthest without falling were labelled the “most fit” and used to spawn the next generation. By running this process over several generations, they evolved algorithms capable of generating natural-looking movement in any situation, says Reil. These skills will be on show in NaturalMotion’s Backbreaker American football game, which is due for release in June. Reil’s team have now applied their algorithms to radically different body shapes. “We can add additional joints – we might give a leg two knees,” says Reil. “And recently I’ve been looking at how a three-legged stool walks and balances. It makes you realise why biology doesn’t go for three legs.” Colin Barras n
TECHNOLOGY
Steer space junk out of Earth’s orbit with a laser WITH Earth’s orbit cluttered with dead satellites, discarded rocket boosters and other space junk, ways to prevent the accumulation of such debris are desperately needed. How about using a tractor beam to simply steer future junk aside, says space-flight engineer John Sinko of Nagoya University, Japan. Sinko’s idea is based on an experimental type of spacecraft engine called a laser thruster. Inside these motors, laser pulses fired into a mass of solid propellant cause a jet of material to be released, pushing the craft in the opposite direction. Sinko realised that the laser did not necessarily have to be on the same craft. “These on-board motors
“A spacecraft could fire a low-power laser beam at another craft to steer it from a distance” could also be targeted remotely by lasers for tractor beaming,” he says. He has designed a series of laser thrusters that can be activated in this way. A spacecraft fitted with a laser would fire a low-power beam at a thruster fitted on another craft to attract, repel or steer it in another direction. Pushing a spacecraft away is a relatively simple matter, but more complex designs using mirrors are
needed to use a beam to tug one towards the laser (see diagram). Combining those designs could allow full control in any direction, says Sinko. He imagines spacecraft being fitted with remotely operated thrusters before launch, so that once they reach the end of their lives it is simple to alter their orbit or even shove them into the atmosphere to burn up – even if they have lost all power (Journal of Propulsion and Power, DOI: 10.2514/1.46037). Tractor beams could be fired from up to 100 kilometres away, says Sinko, either from a spacecraft in orbit or a mirror in space redirecting a beam from Earth. “It’s an interesting idea that could work in principle,” says Richard Holdaway, director of space science technology at the Rutherford Appleton Laboratory in Didcot, UK. Keeping a laser beam accurately trained on a distant motor would be a challenge, he adds, “but perhaps not an insurmountable one”. Sinko hopes to test one of his tractor beams on a 10-kilogram satellite within a few years. He is not alone in trying to develop such technology: a team at the Research Institute for Complex Testing of Optoelectronic Devices and Systems in Sosnovy Bor, Russia, is working on similar ideas. Paul Marks n
Making space in space Satellites fitted with laser thrusters could be controlled remotely with low-power lasers to manoeuvre them out of Earth’s orbit
PUSHING
PULLING
INCOMING LASER BEAM
INCOMING LASER BEAM
EXHAUST
PROPELLANT PROPELLANT SATELLITE SURFACE
MIRROR
THRUST
THRUST
20 | NewScientist | 1 May 2010
THRUST
EXHAUST
–So real it hurts–
Survival of the fittest makes for more lifelike animations MONSTERS and aliens that move more realistically than ever before are coming soon to a screen near you. It’s all down to an animation technique first used to “evolve” the most lifelike interaction between human characters and their surroundings through trial and error. NaturalMotion of Oxford, UK, whose technique was used in the films Troy and Poseidon, has now shown that artificial evolution can equally be applied to non-human body shapes – for instance, bipedal monsters. “It’s equivalent to me waking up in a child’s body and being able to balance and look natural straight away,” says Torsten Reil, the firm’s CEO. State-of-the-art animation for non-human film characters usually involves filming real actors wearing motion-capture sensors. Then artwork of a monster, say, is mapped onto the footage and made to move using these sensors as a guide. Computer games use this technique but it is not ideal because a number of set sequences must be applied in almost all situations.
The team at NaturalMotion took a different approach. They began with 100 identical virtual skeletons, complete with simulated muscles and motor nerves. Then they attributed random values to the strength of connections between key motor nerves in each individual and made them perform a task, such as walking. Those that walked furthest without falling were labelled the “most fit” and used to spawn the next generation. By running this process over several generations, they evolved algorithms capable of generating natural-looking movement in any situation, says Reil. These skills will be on show in NaturalMotion’s Backbreaker American football game, which is due for release in June. Reil’s team have now applied their algorithms to radically different body shapes. “We can add additional joints – we might give a leg two knees,” says Reil. “And recently I’ve been looking at how a three-legged stool walks and balances. It makes you realise why biology doesn’t go for three legs.” Colin Barras n