Breakthrough Starshot: 20% light speed to Alpha Centauri nanocraft

Tom Kalbfus · 2016-04-12 11:28:26

http://www.space.com/32548-20-percent-l … video.html

Billionaire pledges $100m to send spaceships to Alpha Centauri
the_bright_star_alpha_centauri_and_its_surroundings-copy-1200x800.jpg
Our neighbouring star Alpha Centauri

ESO/Digitized Sky Survey 2

Today, billionaire Yuri Milner, along with physicist Stephen Hawking, announced the largest ever investment in interstellar travel: a $100 million fund to research and prototype a spacecraft capable of reaching the nearest star in just 20 years.

Forget starships, though. These “wafersats” would be small enough to fit in your hand, weighing just a few grams. Milner and his scientific advisory team believe recent developments in lasers and nanotechnology should make it possible to send thousands of these probes to Alpha Centauri, where they could beam back pictures and scientific data on any planets in orbit.

“We have done some recent research with some of the best minds in different areas, and to my surprise I have concluded it can be done within a generation,” says Milner. But the ambitious project, dubbed Breakthrough Starshot, is likely to raise eyebrows amongst the scientific community.

The plan involves launching spacecraft that are little more than a silicon wafer 10 centimetres across, comparable to the guts of a smartphone. These probes will use metre-wide lightsails of reflective material to capture the momentum from colliding photons and propel themselves along.

Sails powered by sunlight are in the works, but these only produce a small amount of thrust. That’s why, back on Earth, a 100 gigawatt laser will shoot into the sky and dump enormous amounts of energy into this sail, accelerating the craft to 20 per cent of light speed – enough to coast the 4 light years to Alpha Centauri in 20 years.

Fringe science
The technology required to do this doesn’t yet exist, but Milner is confident his team can develop it. “We have researched about 20 technical challenges, and we believe that none of those is insurmountable,” he says. “There is no physical law that contradicts this particular model.”

Yuri Milner is splashing the cash to send tiny spaceships to other stars

Andy Rain/epa/Corbis

Interstellar travel is a fringe area of science, and while many plans exist on paper, space agencies like NASA have devoted little resources to fleshing out the details. Milner, who has funded science prizes and efforts to search for aliens, wants to change that.

So he created a scientific advisory board and settled on a scheme developed by Philip Lubin and his colleagues at the University of California, Santa Barbara. “They’ve enabled this to go from an idea to reality,” says Lubin.

Lubin’s road map to interstellar flight rests on two technological developments. The first is a technique for combining many smaller lasers into a single larger one, known as phased arrays, which was recently developed by the US Defense Advanced Research Project Agency (DARPA).

“Phased arrays have been made in small sizes, and there does not appear to be a fundamental limit of why we can’t go to larger sizes,” he says. But an array capable of beaming the required 100 gigawatts would stretch over a kilometer.

The other is the rise of smaller spacecraft, in part driven by miniaturization for the smartphone industry. Cubesats, just 10 centimeters on each side, are a mainstay in orbit these days. Lubin thinks advances in semiconductor manufacture can crunch this down to a 2D-wafer, while still enabling a spacecraft bristling with sensors.
Cost of a phone
In the coming years, the team plans to develop and test such spacecraft, which would eventually be deployed from a “mothership” in orbit before being accelerated by the giant laser. The team aims to bring the cost of their probes down to that of an iPhone, allowing them to launch thousands of them. Such large numbers are needed because the tiny craft could easily be damaged by high-speed collisions with interstellar dust.

“We have a number of things we want to do in the first and second year,” says Avi Loeb of Harvard University, who heads Milner’s advisory board. “We want to demonstrate that we can send such craft, hundreds of them, with cameras to take pictures of the moon.” The team is already in talks to launch the craft on a conventional rocket to the moon in a year or two, says Loeb.

Some are sceptical that Lubin’s road map can be easily realised. “There is no physical limitation, but there are plenty of engineering challenges,” says Paulo Lozano of the Massachusetts Institute of Technology. These include building a laser far larger than any we have today, developing techniques to use it as both propulsion and communication for the spacecraft, and protecting a tiny probe from the hostile environment of interstellar space. “I honestly don’t think that we are ready with the technology that we have,” Lozano says.

“The technical challenges and economic costs are so high that it is not at all feasible and probably won’t be for a long time,” says Ian Crawford of Birkbeck, University of London. Such small spacecraft are likely to be limited in the data they can gather and beam back, but it may be worth trying the technology. “If we want to study exoplanetary systems in detail, we will need to be able to send spacecraft to these places,” Crawford says. “Exploring these beam-powered propulsion systems with low mass payloads would be a step on the road.”

Colossal scale
Even if the team can overcome the technical problems, there is no guarantee we’ll be seeing pictures from Alpha Centauri any time soon. The $100 million is only enough for research, not to fund the full mission, which Milner says will be a decades-long, multibillion dollar project on the scale of the world’s biggest scientific experiments, like the James Webb Space Telescope or the Large Hadron Collider.

Who will fund such a venture is unclear. “Yuri is optimistic he can convince many of his friends to contribute,” says Loeb.

A partnership with organisations like NASA is also a possibility, but the space agency may not be interested. In 2013, billionaire Dennis Tito announce funding for a similarly ambitious project to send a private crewed spacecraft to Mars by 2018, but soon went to NASA asking for assistance. It rejected the mission, which now seems unlikely to ever happen.

“We are not saying it’s easy. We are investing in something that is realistic in the next few years, and then we will take it step by step,” says Milner. “Flying to other stars is dramatically more complicated than within our solar system. We are only saying that we are technologically ready to do this.”

Last edited by Tom Kalbfus (2016-04-12 11:38:18)

RobertDyck · 2016-04-12 13:03:38

You realize Alpha Centauri isn't actually the closest star. Proxima Centauri is closer. Parallax data I got from NASA a number of years ago said Alpha Centauri is 4.38 light years away, while Proxima Centauri is 4.28 light years away. Wikipedia today says Alpha Centauri is 4.37 light years, and Proxima Centauri 4.24 light years. Probably newer data. Technically Proxima Centauri is in orbit about Alpha Centauri, but right now it's 0.13 of a light year closer. It's a very slow orbit, so for the next few centuries it will be closer. Alpha Centauri is a binary star, but if you include Proxima Centauri that makes the star system ternary (3 stars).

Binary stars have a problem, planetary orbits are not stable. Astronomers calculated that a planet would have to be either very close to one star, or very far so that it orbits the gravitational centre between the stars. Any planet in an intermediate orbit would be tugged by gravity of the other star, making its orbit unstable. Alpha Centauri A has 10% more mass than our Sun, and 51% more luminous. Alpha Centauri B is 90.7% as much mass as our Sun, and 44.5% as luminous. "A" has spectral type G2V, "B" is K1V. Our Sun is G2V. So both stars are similar to our Sun. The stars are in orbits about their common gravitational centre, and the orbits are eliptical. Distance between the stars varies from the distance between Pluto and our Sun, to the distance between Saturn and our Sun. So a planet orbiting one star would see that star as a "sun" while the other would appear as a very bright star. I wonder how bright it would appear? Would it be brighter than our Moon?

One planet has been discovered, called Alpha Centauri Bb. That is "b" is the second planet candidate discovered around Alpha Centauri "B", but the only one (so far) believed to exist. The paper published in Nature stated there was a 0.02% probability that it was a spurious detection, meaning it doesn't actually exist. A paper published last October claims it doesn't actually exist. Either way, that planet was said to have an orbital period of 3.2 days making it only 3.6 million miles (6 million km) from its star. Earth orbits about 93 million miles, or 150 million km, from the Sun. "Fried" would be an understatement.

Proxima is 0.237 ± 0.011 light years from Alpha Centauri; it's current position in orbit makes it 0.13 light years closer to Earth. As I said, it will be closer for many centuries. It's a red dwarf star, spectral class M6 Ve, mass 0.123 that of our Sun, radius 0.141 that of our Sun, absolute luminosity 0.0017 that of our Sun. Proxima is likely to have stable planets. Terrestrial ecozone (Goldilocks zone) would have an orbital period of 3.6–14 days; so close that a planet might be tide locked to it's star. But there is a chance of a habitable planet.

I'm trying to argue to send the first interstellar probe to Proxima Centauri instead of Alpha Centuari. It's closer, and greater chance of a habitable planet.

Tom Kalbfus · 2016-04-12 15:12:55

RobertDyck wrote:

You realize Alpha Centauri isn't actually the closest star. Proxima Centauri is closer. Parallax data I got from NASA a number of years ago said Alpha Centauri is 4.38 light years away, while Proxima Centauri is 4.28 light years away. Wikipedia today says Alpha Centauri is 4.37 light years, and Proxima Centauri 4.24 light years. Probably newer data. Technically Proxima Centauri is in orbit about Alpha Centauri, but right now it's 0.13 of a light year closer. It's a very slow orbit, so for the next few centuries it will be closer. Alpha Centauri is a binary star, but if you include Proxima Centauri that makes the star system ternary (3 stars).
Binary stars have a problem, planetary orbits are not stable. Astronomers calculated that a planet would have to be either very close to one star, or very far so that it orbits the gravitational centre between the stars. Any planet in an intermediate orbit would be tugged by gravity of the other star, making its orbit unstable. Alpha Centauri A has 10% more mass than our Sun, and 51% more luminous. Alpha Centauri B is 90.7% as much mass as our Sun, and 44.5% as luminous. "A" has spectral type G2V, "B" is K1V. Our Sun is G2V. So both stars are similar to our Sun. The stars are in orbits about their common gravitational centre, and the orbits are eliptical. Distance between the stars varies from the distance between Pluto and our Sun, to the distance between Saturn and our Sun. So a planet orbiting one star would see that star as a "sun" while the other would appear as a very bright star. I wonder how bright it would appear? Would it be brighter than our Moon?
One planet has been discovered, called Alpha Centauri Bb. That is "b" is the second planet candidate discovered around Alpha Centauri "B", but the only one (so far) believed to exist. The paper published in Nature stated there was a 0.02% probability that it was a spurious detection, meaning it doesn't actually exist. A paper published last October claims it doesn't actually exist. Either way, that planet was said to have an orbital period of 3.2 days making it only 3.6 million miles (6 million km) from its star. Earth orbits about 93 million miles, or 150 million km, from the Sun. "Fried" would be an understatement.
Proxima is 0.237 ± 0.011 light years from Alpha Centauri; it's current position in orbit makes it 0.13 light years closer to Earth. As I said, it will be closer for many centuries. It's a red dwarf star, spectral class M6 Ve, mass 0.123 that of our Sun, radius 0.141 that of our Sun, absolute luminosity 0.0017 that of our Sun. Proxima is likely to have stable planets. Terrestrial ecozone (Goldilocks zone) would have an orbital period of 3.6–14 days; so close that a planet might be tide locked to it's star. But there is a chance of a habitable planet.
I'm trying to argue to send the first interstellar probe to Proxima Centauri instead of Alpha Centuari. It's closer, and greater chance of a habitable planet.

Well the idea is to send a swarm of micro laser sails, with a bank of lasers on Earth, it takes a few minutes for those laser sails to reach 20% of the speed of light, according to these scientists. Seems like with an apparatus like that, sending swarms of laser sails to other targets wouldn't be much of a problem, especially since Proxima Centauri is partially on the way to the Alpha Centauri A-B system. So it would take about 22 years for the sail swarm to reach their targets and take pictures once launched, and it takes only a few minutes to launch each swarm. We could also send other swarms to Tau Ceti for instance, maybe Sirius as well, it might be nice to get a close look at the white dwarf Sirius B as well. No one's ever seen a white dwarf star up close before! Other targets may be Epsilon Eridani, Delta Pavonis is a fairly sunlike star as well, and it is a loner like our own Sun, it may have a few planets which might be worth investigating. There is a nearer term option to find those planets as well, a star-shaped occulter blocks the light of a star in from of a space telescope such as the upcoming James Webb telescope to be launched in 2018, with that, it may be possible to detect extra solar planets directly without having to wait 22 years. Also it might be nice to know exactly where those extra-solar planets are, so we can fine tune the trajectory of those laser sails to take close up pictures of them.

SpaceNut · 2016-04-12 18:34:29

Using a laser is akin to using a candle as the sun is way more powerful and the solar wind drops off with distance so for a much smaller sun (laser) to keep pushing it also would need to move with the same rate as what it is pushing also if we look at the power for distance the same is true for how a laser would work with regards from it to the solar sail.....

So if we are taking 22 years we are not at the speed of light as that would only be a little over 4 years....
The speed of light in vacuum, 299,792,458 metres per second or 1 light-year = 9,460,730,472,580,800 metres (exactly) So we would be traveling at 1,720,132,813,196,509 meters per year or 54,507,719 meters per second...

The fastest rocket launch was on January 19, 2006, New Horizons was launched from Cape Canaveral Air Force Station directly into an Earth-and-solar escape trajectory with a speed of about 16.26 kilometers per second (58,536 km/h; 36,373 mph). The Jupiter flyby increased New Horizons' speed by 4 km/s (14,000 km/h; 9,000 mph), accelerating the probe to a velocity of 23 km/s (83,000 km/h; 51,000 mph) relative to the Sun and shortening its voyage to Pluto by three years.

So we would need to push that very fast rocket a multiple of approximately 2400 times faster ...ouch...

So once we get close to the target system what are we doing? choice 1 is going into orbit about the sun trying to slow down some how so as to stay in the system, choice 2 trying to slow down in order to orbit an exoplanet....of which these will be total autonomous in happening and the best that we could expect is just a steady stream of data coming to us if we can recieve it 4 years plus after we are there.....

Tom Kalbfus · 2016-04-12 18:52:15

I don't think the sail swarm can slow down, once there, it will pass through the system at 20% of the speed of light taking pictures as it passes through. We can send other sail swarms at each individual target in the system, we will probably have to observe those objects through a telescope to tell where they are going to be when the sail swarms pass through. Being very small, the tiny sails can endure tremendous acceleration, which is how they accelerate to 20% of the speed of light in a few minutes. Lets say it takes 1 minute to accelerate to 20% of the speed of light. There are 60 seconds in a minute with an average speed of 10% of the speed of light, the sails will travel 1,800,000 km in one minute, so the laser beams would have to accelerate those sails over that distance, and then they would coast.
The acceleration would be 1,000,000 meters per second squared or about 100,000 times the acceleration due to Earth's gravity for a period of 60 seconds. So if the sail weighs 1 gram, if would weigh 100 kg under that acceleration.

RGClark · 2016-04-28 22:32:10

I've been thinking of ways we can get such nanocraft to link up through self-assembly and form larger structures that can do more detailed observations and experiments. This could work even for visits to far off destinations still in the Solar System such as Kuiper belt objects like Pluto or the Oort cloud.

The main problem is getting the many objects flying independently and getting further apart the further out they go to gradually be drawn to each other and link up. Once they link up, I don't it would be too difficult to then get them to do self-assembly.

But it's that drawing together step that is the hard part.

Some ideas on how they might be made to link up: perhaps the light sails can be angled so that they would be directed to conglomerate at a common point. It is known that solar/laser sails can do "tacking" to change their direction.

Another possibility is that there will be the ionized solar wind and interplanetary and interstellar dust that the nanoprobes could react against to be directed to a common point.

BTW, I don't think it would too difficult to do the self-assembly. Still I'd like to get some feedback on how it could done. Note the nanoprobes are consider to be about the size, and complexity of, say, a virus, or RNA molecule. This also raises the possibility of alien species using this to seed other star systems with life.

Bob Clark

Last edited by RGClark (2016-04-28 22:33:38)

Tom Kalbfus · 2016-04-29 02:43:54

The nanocraft can also be targeted at another object in between Earth and Alpha Centauri, another spaceship perhaps, a larger one capable of carrying humans, this spaceship has a laser that targets the incoming nanocraft, ionizing each one, producing a plasma stream approaching the larger ship at 20% of the speed of light. The larger ship also happens to have a magsail, which deflects the incoming particle stream, transferring the momentum to the larger ship. The acceleration for the larger ship is more gradual, and unlike the micro sails, the larger ship can also decelerate using the stellar winds of the two target stars, since the ship will be moving towards them at almost 20% of the speed of light, the stellar wind will be moving in the opposite direction relative to the ship at 20% of the speed of light, and fully capable of slowing that ship down from 20% of the speed of light, but not capable of reaccelerating the ship back up to 20% of the speed of light. The starshot approach is half of what is needed to send humans to Alpha Centauri. if we can get an acceleration of 1 g, it would take 6,000,000 seconds to reach 20% of the speed of light 100,000 minutes, or 1666 hours and 40 minutes or 69 days, 10 hours, and 40 minutes, it would still take 22 years to get there and another 69 days, 10 hours, and 40 minutes to slow down upon approach. Then an interplanetary drive to reach the planet of our choice.

RGClark · 2016-04-29 20:17:01

Assuming we can get the nanoprobes to link up this may be something we can do now. The Hawking proposal is for a 100 gigawatt laser to send multitudes of 1 gm probes. Then scale down the size of the probes to get a more feasible laser power requirement. See the list of typical values of the mass of different objects here:

https://en.m.wikipedia.org/wiki/Orders_ … .88.927_kg

A human ovum weighs in the range of a few micrograms. This would require a laser only 100 kilowatts. With the nanoscale engineering currently used to make integrated circuits, we can make a quite complex "cell" of the same mass of a human ovum that can be used to build a more complex system.

Bob Clark

tahanson43206 · 2023-10-03 17:59:16

The video at the link below provides a comparison of various ways to reach Proxima Centuri. The animation is good, and narration (by text) about right for a general audience.

https://www.msn.com/en-us/news/technolo … dfc6&ei=23

There is probably a shorter URL.

(th)

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#1 2016-04-12 11:28:26

Breakthrough Starshot: 20% light speed to Alpha Centauri nanocraft

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#5 2016-04-12 18:52:15

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#6 2016-04-28 22:32:10

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