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I’m usually sceptical about eye-catching space missions bankrolled by rich men and launched in the presence of Stephen Hawking. So I’m surprised to find myself intrigued by Yuri Milner’s Project Starshot. Milner is a Russian billionaire entrepreneur who founded the Breakthrough Foundation, which funds ambitious research to explore the universe and “seek scientific evidence of life beyond Earth.” He is putting $100m into the project of developing a fleet of tiny spacecraft. The idea is to send them to the nearest star system, Alpha Centauri, and have them transmit back images and data within (some of) our lifetimes.
Alpha Centauri is 4.4 light years (about 40 trillion km) away, which means that to get there in 20 years, as Milner envisages, will require the vessels to travel at a quarter of the speed of light (up to 60,000km a second), thousands of times faster than a typical spacecraft travels in our solar system at the moment. To do this, Milner proposes that we should use light power.
The vessels would deploy “light sails” and would be propelled by the force that light imparts when it falls on a surface. Each craft would be tiny—no bigger than a coin, and weighing a few grams—and would be loaded with miniaturized cameras and other instruments. Each would have a sail attached, about a metre or so square. Initially, they would be boosted to enormous speeds by being pushed with the beam of a massive Earth-bound laser. The technology exceeds current capabilities, but several space experts agree that it’s feasible.
The fact that light exerts pressure, even though it has no mass (and so, you might say, apparently nothing to “push with”) has been recognized ever since James Clerk Maxwell developed the modern theory of light as an electromagnetic wave in the late 19th century. It was originally thought that “light mills”—little windmill-type devices placed inside a vacuum bulb, first made by William Crookes in 1873—rotate by light pressure when they are illuminated. That turned out not to be the true explanation for the rotation, but all the same, light pressure is now well established.
It’s on this basis that “solar sailing” has long been discussed as a means of cheap space travel. The idea is that huge, lightweight reflective “sails,” perhaps hundreds of metres across, would be unfurled on spacecraft once outside Earth’s atmosphere, where they would harvest the pressure of sunlight to sail through space. The push is tiny but in space, without air resistance or gravity, any small force will create steady acceleration, leading eventually to immense speeds.
If a fleet of tiny unmanned craft can get to Alpha Centauri this way, they could send back messages at light speed, so we’d only have to wait another four and a half years to receive them. If we can get a mission launched in the next ten years, it will be only 25 years after that—all going to plan—that we get a close-up view of another star system.
Sadly, it won’t be the most interesting of star systems. Alpha Centauri has little to recommend it as a destination beyond proximity: no planets have been detected around the star. It is actually a binary star: two stars orbiting one another, along with a small third companion, a red-dwarf star called Proxima Centauri. That doesn’t preclude the possibility of the system having planets, but it’s a complicated environment in which to form them.
Other nearby stars look more promising in that respect, but even the nearest of these change the mission time significantly in human terms. Epsilon Eridani, which appears to have at least one massive Jupiter-like planet, is 10.5 light years away, making the journey and reporting time more like 65 years.
Most rocket scientists seem to agree that, if we’re going to set our sights beyond our own neighbourhood—the moon, Mars, the asteroids—then we need to find new ways of powering spacecraft besides loading them with conventional rocket fuel. Aside from light sailing, one popular candidate is the Star Trek-sounding “ion thruster” an engine powered by firing electrically charged atoms (ions) out of the exhaust, accelerated by electric fields to enormous speeds. Like all rocket engines, it’s a simple application of Newton’s third law of motion: for every action, there is an equal and opposite reaction. Cast an object in one direction and you create a force propelling you in the other. Conventional rocket engines operate on the same principle, but use much more propellant. Ion thrusters release the propellant more gradually but over a longer period, so it takes longer to build up speed but ultimately they can achieve an enormous velocity.
Ion thrusters have already been used on Nasa spacecraft such as Deep Space 1 (launched 1998 as a test device for this and other new technologies) and Dawn (launched 2007). But the top speed achieved with these is only around 10km a second, so it would take a spacecraft about 100,000 years to reach Alpha Centauri that way.
Milner’s demand for a giant laser has inevitably led to wisecracks about him being the next Bond villain in disguise. But it’s not clear that we really have the technology to make the idea work yet—which is why Milner is putting his money where his mouth is.
Among other things, this development is further confirmation that the future of space exploration might be in the private sector. What with space tourism and asteroid mining, it is going to be the wealthy entrepreneurs who are driving innovative means of getting into space and doing stuff there. On the one hand, this probably places human spaceflight, which is showboating with little scientific value, where it belongs: in the commercial sphere. For once, it might also exemplify a little of the free market’s much vaunted “public good from private greed,” accelerating space technologies in a way that more conservative government-backed space agencies will not.
But it’s hard not to feel a little queasy at the sight of so much money literally going up in smoke while the Earth still needs good alternative energy technologies to fossil fuels—not to mention the myriad other global problems science must address, such as water crises, antibiotic resistance and viral epidemics. But to regard philanthropy as a zero-sum game doesn’t obviously make much sense: it’s not as if we can expect to vote on how billionaires use their cash.
And next to the vanity project that is Virgin Galactic, or the rapacious space-buccaneering of lunar or asteroid mining, a mission to a star looks exciting and noble, as well as scientifically useful. When the European Space Agency landed a space probe on a comet, when Nasa sent a craft down to take photos of Saturn’s moon Titan, covered with lakes of liquid methane, and when its New Horizons craft brought us jaw-dropping images of Pluto, I felt proud that humans could do such things, and more certain that it is healthy for a culture to be devoting some of our resources and ingenuity to space exploration. Even if Project Starshot proves to be pie in the sky, for chutzpah alone it’s worthy of admiration.
Now read: Could humans survive deep space travel?
I’m usually sceptical about eye-catching space missions bankrolled by rich men and launched in the presence of Stephen Hawking. So I’m surprised to find myself intrigued by Yuri Milner’s Project Starshot. Milner is a Russian billionaire entrepreneur who founded the Breakthrough Foundation, which funds ambitious research to explore the universe and “seek scientific evidence of life beyond Earth.” He is putting $100m into the project of developing a fleet of tiny spacecraft. The idea is to send them to the nearest star system, Alpha Centauri, and have them transmit back images and data within (some of) our lifetimes.
Alpha Centauri is 4.4 light years (about 40 trillion km) away, which means that to get there in 20 years, as Milner envisages, will require the vessels to travel at a quarter of the speed of light (up to 60,000km a second), thousands of times faster than a typical spacecraft travels in our solar system at the moment. To do this, Milner proposes that we should use light power.
The vessels would deploy “light sails” and would be propelled by the force that light imparts when it falls on a surface. Each craft would be tiny—no bigger than a coin, and weighing a few grams—and would be loaded with miniaturized cameras and other instruments. Each would have a sail attached, about a metre or so square. Initially, they would be boosted to enormous speeds by being pushed with the beam of a massive Earth-bound laser. The technology exceeds current capabilities, but several space experts agree that it’s feasible.
The fact that light exerts pressure, even though it has no mass (and so, you might say, apparently nothing to “push with”) has been recognized ever since James Clerk Maxwell developed the modern theory of light as an electromagnetic wave in the late 19th century. It was originally thought that “light mills”—little windmill-type devices placed inside a vacuum bulb, first made by William Crookes in 1873—rotate by light pressure when they are illuminated. That turned out not to be the true explanation for the rotation, but all the same, light pressure is now well established.
It’s on this basis that “solar sailing” has long been discussed as a means of cheap space travel. The idea is that huge, lightweight reflective “sails,” perhaps hundreds of metres across, would be unfurled on spacecraft once outside Earth’s atmosphere, where they would harvest the pressure of sunlight to sail through space. The push is tiny but in space, without air resistance or gravity, any small force will create steady acceleration, leading eventually to immense speeds.
If a fleet of tiny unmanned craft can get to Alpha Centauri this way, they could send back messages at light speed, so we’d only have to wait another four and a half years to receive them. If we can get a mission launched in the next ten years, it will be only 25 years after that—all going to plan—that we get a close-up view of another star system.
Sadly, it won’t be the most interesting of star systems. Alpha Centauri has little to recommend it as a destination beyond proximity: no planets have been detected around the star. It is actually a binary star: two stars orbiting one another, along with a small third companion, a red-dwarf star called Proxima Centauri. That doesn’t preclude the possibility of the system having planets, but it’s a complicated environment in which to form them.
Other nearby stars look more promising in that respect, but even the nearest of these change the mission time significantly in human terms. Epsilon Eridani, which appears to have at least one massive Jupiter-like planet, is 10.5 light years away, making the journey and reporting time more like 65 years.
Most rocket scientists seem to agree that, if we’re going to set our sights beyond our own neighbourhood—the moon, Mars, the asteroids—then we need to find new ways of powering spacecraft besides loading them with conventional rocket fuel. Aside from light sailing, one popular candidate is the Star Trek-sounding “ion thruster” an engine powered by firing electrically charged atoms (ions) out of the exhaust, accelerated by electric fields to enormous speeds. Like all rocket engines, it’s a simple application of Newton’s third law of motion: for every action, there is an equal and opposite reaction. Cast an object in one direction and you create a force propelling you in the other. Conventional rocket engines operate on the same principle, but use much more propellant. Ion thrusters release the propellant more gradually but over a longer period, so it takes longer to build up speed but ultimately they can achieve an enormous velocity.
Ion thrusters have already been used on Nasa spacecraft such as Deep Space 1 (launched 1998 as a test device for this and other new technologies) and Dawn (launched 2007). But the top speed achieved with these is only around 10km a second, so it would take a spacecraft about 100,000 years to reach Alpha Centauri that way.
Milner’s demand for a giant laser has inevitably led to wisecracks about him being the next Bond villain in disguise. But it’s not clear that we really have the technology to make the idea work yet—which is why Milner is putting his money where his mouth is.
Among other things, this development is further confirmation that the future of space exploration might be in the private sector. What with space tourism and asteroid mining, it is going to be the wealthy entrepreneurs who are driving innovative means of getting into space and doing stuff there. On the one hand, this probably places human spaceflight, which is showboating with little scientific value, where it belongs: in the commercial sphere. For once, it might also exemplify a little of the free market’s much vaunted “public good from private greed,” accelerating space technologies in a way that more conservative government-backed space agencies will not.
But it’s hard not to feel a little queasy at the sight of so much money literally going up in smoke while the Earth still needs good alternative energy technologies to fossil fuels—not to mention the myriad other global problems science must address, such as water crises, antibiotic resistance and viral epidemics. But to regard philanthropy as a zero-sum game doesn’t obviously make much sense: it’s not as if we can expect to vote on how billionaires use their cash.
And next to the vanity project that is Virgin Galactic, or the rapacious space-buccaneering of lunar or asteroid mining, a mission to a star looks exciting and noble, as well as scientifically useful. When the European Space Agency landed a space probe on a comet, when Nasa sent a craft down to take photos of Saturn’s moon Titan, covered with lakes of liquid methane, and when its New Horizons craft brought us jaw-dropping images of Pluto, I felt proud that humans could do such things, and more certain that it is healthy for a culture to be devoting some of our resources and ingenuity to space exploration. Even if Project Starshot proves to be pie in the sky, for chutzpah alone it’s worthy of admiration.
Now read: Could humans survive deep space travel?
