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Saving Earth from an asteroid strike
TECHNOLOGY
How to save the world from an asteroid impact There’s no shortage of bright ideas: the problem is picking one that doesn’t make a bad situation worse David Shiga
270-metre-wide asteroid named Apophis, which has a 1 in 45,000 chance of hitting us in 2036. To investigate the best way to deflect this and other asteroids onto a harmless path, a team led by David Dearborn of the Lawrence Livermore National Laboratory in California has modelled the impact of a nuclear explosion on an object’s trajectory. Their virtual asteroid
IT IS 2036. A large asteroid is on a collision course with Earth. Unless it is stopped, it will crash into the Pacific Ocean, creating a devastating tsunami. What should we do? We could blast the asteroid with a nuclear bomb, but that would risk shattering it into smaller pieces that could still threaten Earth. Or maybe we should try to “Gently nudging an asteroid force it off course by slamming would knock it off course into it with a heavy object – an without breaking it into unproven and therefore risky pieces that could hit Earth” technique. Now there may be a third option: gently nudging the asteroid away from Earth was 1 kilometre in diameter and without breaking it apart, either made of rocky rubble loosely by exploding a nuclear device bound together by gravity, which at a distance or zapping it with is considered by many planetary high-powered lasers. scientists to be the most likely Astronomers have found composition for small asteroids. thousands of asteroids that pass Thirty years before the asteroid near Earth’s orbit, and a few of was set to collide with Earth, these are on trajectories that give a nuclear blast, equivalent to them a small chance of hitting 100 kilotonnes of TNT, was set off Earth. The most worrying is a 250 metres behind it. The nudge Laser asteroid deflector Between eight and 20 spacecraft focus laser light onto a spot on the asteroid, vaporising a section of the object to provide thrust to push it in a new direction Each craft carries a 20-metre mirror, a solar array and a laser Path of asteroid before laser impact
Blasting the asteroid with laser light for months or years pushes it away from Earth
18 | NewScientist | 28 March 2009
from the explosion increased its velocity by 6.5 millimetres per second, a slight change but enough for it to miss us. The technique also reduced the risk of a break-up – just 1 per cent of the asteroid’s material was dislodged by the blast, and of that only about 1 part in a million remained on a collision course with Earth. Dearborn adds that the technology for this method is already established, unlike for the use of a heavy object to shove the asteroid onto a different path – the “kinetic impactor” strategy. “Should an emergency arise, we should know that [the technology] is available, and we should have some idea of how to properly use it,” he says. He has now begun simulating the effect of nudging an asteroid with a smaller nuclear explosion – less than 1 kilotonne – 1 metre below its surface. This would reduce the device’s weight, making it easier and quicker to launch. He will discuss the work next month
One big bang and the threat has gone If we find an asteroid on a collision course with Earth, with no time to gently deflect it from its path, should we blow it up? It’s a controversial idea as it would break the object into smaller pieces, many of which could still hit Earth. Yet there have been few studies looking into the risk that this would in fact happen. Now a team led by David Dearborn of the Lawrence Livermore National Laboratory in California have carried
out a computer simulation that shows the risk may not be as great as had been feared. In their simulation, a 1-kilometre-diameter asteroid was discovered with little warning time. A spacecraft carrying a 900-kilotonne nuclear device intercepted the asteroid 1000 days before impact, burrowed 10 metres into it and exploded. The blast turned the asteroid into a giant debris cloud, and although some of the debris still
PHOTOS12/ALAMY
For daily technology stories, visit www.NewScientist.com/section/tech
at the 1st IAA Planetary Defense Conference in Granada, Spain. A less established and gentler approach would be to nudge the asteroid away from Earth using lasers. In this theory, being investigated by Massimiliano Vasile of the University of Glasgow in the UK and colleagues with funding from the European Space Agency, a fleet of eight or more spacecraft, each carrying a laser, would be sent to rendezvous with the asteroid. Hovering a few kilometres away, each craft would unfurl a 20-metre-wide mirror made of a flexible material such as Mylar. The mirror would focus the sun’s rays onto the spacecraft’s solar panels, powering the laser. All eight lasers would then be simultaneously fired at a single spot on the asteroid’s surface, vaporising that region and creating a plume of gas that should provide enough thrust to push the asteroid off course (see diagram). This relatively gentle nudging, over a period of months or years, would not break the asteroid up into any smaller pieces, the team say. Vasile, who will also be presenting his idea at the conference, touts the flexibility and reliability of the approach. “You have a formation of satellites and if one breaks you have the others [for back-up],” he says. “And it’s scalable, so if you have a bigger asteroid or you want to –Should have used the lasers– have a faster deflection then you add more spacecraft.” Whichever option is ultimately chosen, reliability will be essential hit Earth, it amounted to only for a task as critical as asteroid 1/100,000th of the asteroid’s deflection, says Bill Ailor of original mass of 1 billion tonnes. the Aerospace Corporation in However, Derek Richardson of El Segundo, California, who is the University of Maryland in College chairing next month’s conference. Park cautions that trying to disperse “Launch vehicles fail at a rate of an asteroid in this way would about 1 in 100, and new spacecraft be risky, since the effect of the might fail at the rate of 1 in 3, explosion will depend on the object’s [which] has to be factored into the internal structure. “It may be that overall design of your deflection,” you just blow out a big hole on the he says. “We’re in a sense betting surface,” he says. the planet that we’re going to make this work.” ■
Vibrating touch screens spell out Braille TOUCH-SCREEN devices like the iPhone are great when you can see them, but not much good if you are blind. Now a new way of presenting Braille characters on a mobile device could be the first step towards a Braille-ready touch-screen phone. In Braille, letters are encoded using a two-by-three matrix in which each character is represented by a different configuration of raised and absent dots at the six locations. To display these dots on a touch-screen device, Jussi Rantala of the University of Tampere in Finland and colleagues used a Nokia 770 Internet Tablet, which has a piezoelectric material built into the touch screen that vibrates when an electric signal is applied to it. The team installed software that represents a raised dot as a single pulse of intense vibration, and an absent dot as a longer vibration made up of several weaker pulses (see diagram, below). To discover how visually impaired volunteers would prefer to receive these vibrations, the team developed two different presentation methods. In the first, the user touches the screen on the left-hand side to read whether or not there is a bump in that position of the matrix, then moves their finger horizontally
across the screen to read the remaining five dots. “But it wasn’t that easy to read,” says Rantala. In the second method, the user simply places a finger anywhere on the screen and holds it still. The phone then displays a character by vibrating the sequence of six dots, each 360 milliseconds apart. “It took some time for them to start reading, because this representation is totally different from anything else that they had previously used,” says
“Once the volunteers were used to the vibrations, they could read a letter in as little as 1.25 seconds” Rantala. But once the volunteers were used to it, they were able to speed it up and read a character in as little as 1.25 seconds (IEEE Transactions on Haptics, DOI: 10.1109/toh.2009.3). The team’s next step will be to present entire words and sentences. Screen-reading software is already available that “grabs” information displayed as text and turns it into speech. The same information could be turned into Braille characters on phones with vibrating touch screens, says Rantala. Anil Ananthaswamy ■
Finger on the pulse The raised or absent dots of a conventional Braille character can be represented as a sequence of vibrations of different intensity
Conventional Braille characters
1 2 3
A
B
4 5 6
C
D
E
F
Braille touch screen INTENSE PULSE
C
1
2
WEAKER PULSE
3
4
5
6
28 March 2009 | NewScientist | 19
How to save the world from an asteroid impact There’s no shortage of bright ideas: the problem is picking one that doesn’t make a bad situation worse David Shiga
270-metre-wide asteroid named Apophis, which has a 1 in 45,000 chance of hitting us in 2036. To investigate the best way to deflect this and other asteroids onto a harmless path, a team led by David Dearborn of the Lawrence Livermore National Laboratory in California has modelled the impact of a nuclear explosion on an object’s trajectory. Their virtual asteroid
IT IS 2036. A large asteroid is on a collision course with Earth. Unless it is stopped, it will crash into the Pacific Ocean, creating a devastating tsunami. What should we do? We could blast the asteroid with a nuclear bomb, but that would risk shattering it into smaller pieces that could still threaten Earth. Or maybe we should try to “Gently nudging an asteroid force it off course by slamming would knock it off course into it with a heavy object – an without breaking it into unproven and therefore risky pieces that could hit Earth” technique. Now there may be a third option: gently nudging the asteroid away from Earth was 1 kilometre in diameter and without breaking it apart, either made of rocky rubble loosely by exploding a nuclear device bound together by gravity, which at a distance or zapping it with is considered by many planetary high-powered lasers. scientists to be the most likely Astronomers have found composition for small asteroids. thousands of asteroids that pass Thirty years before the asteroid near Earth’s orbit, and a few of was set to collide with Earth, these are on trajectories that give a nuclear blast, equivalent to them a small chance of hitting 100 kilotonnes of TNT, was set off Earth. The most worrying is a 250 metres behind it. The nudge Laser asteroid deflector Between eight and 20 spacecraft focus laser light onto a spot on the asteroid, vaporising a section of the object to provide thrust to push it in a new direction Each craft carries a 20-metre mirror, a solar array and a laser Path of asteroid before laser impact
Blasting the asteroid with laser light for months or years pushes it away from Earth
18 | NewScientist | 28 March 2009
from the explosion increased its velocity by 6.5 millimetres per second, a slight change but enough for it to miss us. The technique also reduced the risk of a break-up – just 1 per cent of the asteroid’s material was dislodged by the blast, and of that only about 1 part in a million remained on a collision course with Earth. Dearborn adds that the technology for this method is already established, unlike for the use of a heavy object to shove the asteroid onto a different path – the “kinetic impactor” strategy. “Should an emergency arise, we should know that [the technology] is available, and we should have some idea of how to properly use it,” he says. He has now begun simulating the effect of nudging an asteroid with a smaller nuclear explosion – less than 1 kilotonne – 1 metre below its surface. This would reduce the device’s weight, making it easier and quicker to launch. He will discuss the work next month
One big bang and the threat has gone If we find an asteroid on a collision course with Earth, with no time to gently deflect it from its path, should we blow it up? It’s a controversial idea as it would break the object into smaller pieces, many of which could still hit Earth. Yet there have been few studies looking into the risk that this would in fact happen. Now a team led by David Dearborn of the Lawrence Livermore National Laboratory in California have carried
out a computer simulation that shows the risk may not be as great as had been feared. In their simulation, a 1-kilometre-diameter asteroid was discovered with little warning time. A spacecraft carrying a 900-kilotonne nuclear device intercepted the asteroid 1000 days before impact, burrowed 10 metres into it and exploded. The blast turned the asteroid into a giant debris cloud, and although some of the debris still
PHOTOS12/ALAMY
For daily technology stories, visit www.NewScientist.com/section/tech
at the 1st IAA Planetary Defense Conference in Granada, Spain. A less established and gentler approach would be to nudge the asteroid away from Earth using lasers. In this theory, being investigated by Massimiliano Vasile of the University of Glasgow in the UK and colleagues with funding from the European Space Agency, a fleet of eight or more spacecraft, each carrying a laser, would be sent to rendezvous with the asteroid. Hovering a few kilometres away, each craft would unfurl a 20-metre-wide mirror made of a flexible material such as Mylar. The mirror would focus the sun’s rays onto the spacecraft’s solar panels, powering the laser. All eight lasers would then be simultaneously fired at a single spot on the asteroid’s surface, vaporising that region and creating a plume of gas that should provide enough thrust to push the asteroid off course (see diagram). This relatively gentle nudging, over a period of months or years, would not break the asteroid up into any smaller pieces, the team say. Vasile, who will also be presenting his idea at the conference, touts the flexibility and reliability of the approach. “You have a formation of satellites and if one breaks you have the others [for back-up],” he says. “And it’s scalable, so if you have a bigger asteroid or you want to –Should have used the lasers– have a faster deflection then you add more spacecraft.” Whichever option is ultimately chosen, reliability will be essential hit Earth, it amounted to only for a task as critical as asteroid 1/100,000th of the asteroid’s deflection, says Bill Ailor of original mass of 1 billion tonnes. the Aerospace Corporation in However, Derek Richardson of El Segundo, California, who is the University of Maryland in College chairing next month’s conference. Park cautions that trying to disperse “Launch vehicles fail at a rate of an asteroid in this way would about 1 in 100, and new spacecraft be risky, since the effect of the might fail at the rate of 1 in 3, explosion will depend on the object’s [which] has to be factored into the internal structure. “It may be that overall design of your deflection,” you just blow out a big hole on the he says. “We’re in a sense betting surface,” he says. the planet that we’re going to make this work.” ■
Vibrating touch screens spell out Braille TOUCH-SCREEN devices like the iPhone are great when you can see them, but not much good if you are blind. Now a new way of presenting Braille characters on a mobile device could be the first step towards a Braille-ready touch-screen phone. In Braille, letters are encoded using a two-by-three matrix in which each character is represented by a different configuration of raised and absent dots at the six locations. To display these dots on a touch-screen device, Jussi Rantala of the University of Tampere in Finland and colleagues used a Nokia 770 Internet Tablet, which has a piezoelectric material built into the touch screen that vibrates when an electric signal is applied to it. The team installed software that represents a raised dot as a single pulse of intense vibration, and an absent dot as a longer vibration made up of several weaker pulses (see diagram, below). To discover how visually impaired volunteers would prefer to receive these vibrations, the team developed two different presentation methods. In the first, the user touches the screen on the left-hand side to read whether or not there is a bump in that position of the matrix, then moves their finger horizontally
across the screen to read the remaining five dots. “But it wasn’t that easy to read,” says Rantala. In the second method, the user simply places a finger anywhere on the screen and holds it still. The phone then displays a character by vibrating the sequence of six dots, each 360 milliseconds apart. “It took some time for them to start reading, because this representation is totally different from anything else that they had previously used,” says
“Once the volunteers were used to the vibrations, they could read a letter in as little as 1.25 seconds” Rantala. But once the volunteers were used to it, they were able to speed it up and read a character in as little as 1.25 seconds (IEEE Transactions on Haptics, DOI: 10.1109/toh.2009.3). The team’s next step will be to present entire words and sentences. Screen-reading software is already available that “grabs” information displayed as text and turns it into speech. The same information could be turned into Braille characters on phones with vibrating touch screens, says Rantala. Anil Ananthaswamy ■
Finger on the pulse The raised or absent dots of a conventional Braille character can be represented as a sequence of vibrations of different intensity
Conventional Braille characters
1 2 3
A
B
4 5 6
C
D
E
F
Braille touch screen INTENSE PULSE
C
1
2
WEAKER PULSE
3
4
5
6
28 March 2009 | NewScientist | 19