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Stephen Hawking’s plan to blast a tiny ship to another star

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By Ryan Faith
This week, on the 55th anniversary of Yuri Gagarin’s first-ever manned spaceflight, Russian internet entrepreneur Yuri Milner and British physicist Stephen Hawking announced a project aimed to send a spacecraft to another star. With lasers!
Breakthrough Starshot, as it’s called, has a lot going for it in terms of popular interest: Hawking, starships, lasers, super tiny robots, and billionaires (the good internet kind, not the evil oil industry kind). The only way science could get any sexier is if Neil deGrasse Tyson and Bill Nye sang a romantic duet.
And it may not even be bullshit.Space is very well-named. It’s unimaginably, mind-bogglingly big and empty. Everyone on Earth is nothing but microscopic statistical fluctuations in the otherwise near-perfect featureless nothing. Even the bits of space that contain something are so far apart that there’s really no way for a human mind to grasp the distance in concrete terms.
The basic unit of measurement for distance on interstellar scales is the light year (ly). It, like space, is also well-named, because it’s how far light can travel in one year. One light year is 5,879,000,000,000 miles. But 5.8 trillion anything is an unimaginably large number, whether it’s miles, debt dollars, or marshmallow Peeps. A light year is so much distance that it makes typical units of measurement, like miles, all but meaningless.
The closest star system, Alpha Centauri, is 4.367 ly away. That means that at the speed of light, which is literally as fast as information can travel, it takes more than four years and four months for a message to get from there to here. It is quite literally impossible and counter to the laws of physics for Earth to know about anything that happened near Alpha Centauri since December 2011.
And that’s the closest star to Earth.
You can skip this next bit all this if you’ve been keeping up on your rocket science. We’re skipping rocket equations, impulse, relativity, and whatnot, and just tagging the big points.
Travel between stars comes down to a problem of how much stuff you have to move (mass), how much energy you can put into making it go faster (energy), and how long it will take to get there (time). If you want to send something of a reasonable mass (an astronaut, dishwasher, or dairy cow) to another star, and you can expend only a certain amount of energy doing it, then it will take unreasonable amounts of time to get there. The Voyager 1 probe is the first and only human-made thing that has ever left the solar system. If it were heading in the correct direction (it isn’t), it would take more than 75,000 years to reach Alpha Centauri.
If, however, you want to send that cow to Alpha Centauri in a reasonable amount of time (say, 25 years), you need an unreasonable amount of energy. Without running the numbers, it’s safe to say that this amount of energy is way beyond the realm of practicality.
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Lastly, if you want to spend a reasonable amount of time and a reasonable amount of energy, then your spacecraft needs to be very small. But what if instead of reasonable energy, we use a gigantic amount, and instead of a very small spacecraft, we use one that is downright adorable and teeny-tiny. Play with the numbers, and we may be able to get that craft traveling at 20 percent the speed of light. That’s enough to get us to Alpha Centauri in a perfectly reasonable 20 years.
How teeny-tiny does the spacecraft need to be, and how gigantic an amount of energy are we figuring on? Well, if the bright folks at Breakthrough Starshot are to be believed, the spacecraft will weigh just a few grams. That’s basically the weight of a postcard, plus or minus a few paperclips. As for energy, we’re talking a bit more than the output of all the world’s nuclear power plants in 15 minutes. (Again, these are considered the “reasonable” numbers. Space, as previously reported, is kind of insane.)
This is where the lasers come in. When light hits something, it exerts an incredibly minuscule amount of pressure. But shoot enough light at something, and that pressure starts to add up. Breakthrough Starshot wants to aim about 100 gigawatts of laser power at its spaceship for two minutes.
The total thrust that would create is less than the amount needed to keep a dairy cow hovering in mid-air on Earth. But apply that thrust to something light as a postcard in space, and the ship would hightail it on out of here at an acceleration equivalent to 60,000 times Earth’s gravity.
The pointy-headed folks are putting their faith in a couple of things happening before they can build their spaceship. The first involves Moore’s Law, which states that the number of transistors that can be shoehorned into a computer circuit doubles every two years. In a very simplified nutshell, it’s the reason we everyone has a smartphone today, but 30 years ago, a basic cell phone the size of a brick was considered cutting-edge technology, available only to the super wealthy. The trend toward more and better technology in tinier and tinier packages is why Hawking and friends believe they will one day get something useful out of a spacecraft that weighs as much as a postcard.
Oh, and laser power increases according to relatively similar rules. But that said, this laser array would not be something that could be plugged into the nearest wall outlet. Folks are putting forward some ideas about chemically powered lasers, but regardless, the idea is that with a couple decades of steady technological advancement, it might just be possible to build a big enough array of giant lasers with enough juice to zap the crap out of a space postcard and blow it into the next star system.
That said, even if this approach isn’t crazy, that doesn’t mean it’s a done deal. Even if it turns out Breakthrough Spaceshot can do it, that doesn’t mean they will do it. Because just as they will need to juggle mass, power, and time, they will also need to work with cost, politics, and time.
Super rough guesstimates figure than in 20 years or so, the cost for a laser array big enough to do this will be in the $5 billion to $10 billion range. That’s very rough, and doesn’t count R&D and other costs. The folks at Breakthrough Starshot figure that before they even need to worry about a whole mess of lasers, they need to get a very small scale demonstration system set up. Right now, they’re guessing that the $100 million that’s been put up by Russian billionaire Yuri Milner should be enough to build a proof-of-concept demonstrator. If that small-scale test rig is successful and can demonstrate the fundamentals, it will become much, much easier to scare up the cash either from private or public sector sources. Traditionally, the biggest obstacle to privately funding space stuff is proving you’re not a scam artist or lunatic yammering about, say, space lasers.
After a successful proof of concept, it’ll be time to convince other billionaires like Mark Zuckerberg, who is on the board of Breakthrough Starshot, and their various buddies to each toss a few hundred million in the kitty, until there is enough cash to go build a giant array of lasers in the Chilean mountains. But, really, based on the previous century of large-scale mega projects like this, government funding will still be necessary. Which brings in politics and time.
If some government agency stashed away $500 million per year for the next two decades — the time Breakthrough Starshot figures it needs before technology matures enough — there would be more than $10 billion on hand. But no government budget is ever structured like that. That said, there is precedent for advanced planning of some sort; a good 20 years before the first moon landing — and more than 10 years before President John F. Kennedy committed the US to going to the moon — some of the political groundwork was already being put in place.
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So when the Soviets beat the US to putting the first human in space, there was already a path of sorts when Kennedy came asking what the US could do to show they didn’t suck at space. So maybe a launch 20 years from now isn’t crazy talk.
On the other hand, humanity has been “about 20 years” away from landing a guy on Mars since sometime in the mid-1960s.
Let’s wave the magic wand and fast forward several decades. Everything has come together, everything works and our postcard spaceship is zipping along at a merry 134,000,000 miles per hour when it finally reaches Alpha Centauri. The little ship has been lucky enough to avoid any dust or whatnot on the way (hitting anything whatsoever at these speeds means game over). What happens?
You’re going to get about a day or two in-system before you’ve barreled through the whole thing and are off into deep nothingness. The ship is way, way too tiny to carry enough fuel to slow down. So the spaceship will do some drive-by science and send back images of whatever the cameras happen to pick up while blasting through the system. Which, frankly, won’t be a huge amount — nowhere near as much data as we normally get back from a mission today. At any rate, during the brief passage, the spacechip shoots that information back to Earth with a very small laser, and then some big-ass telescopes pick up the signal and reconstruct the data. It would be pretty awesome.
Each probe costs less than $1,000 (thanks to Moore’s Law), and launching them isn’t going to break the bank — all the cost here is in building the initial infrastructure. About $100,000 for each mission isn’t out of the question. With a marginal cost like that, you can afford to send many, many probes. And since they’re built and launched one at a time, you can spread that cost out over a long period of time. Maybe launch 250 per year; that’s $25 million per year, which (considering the initial price tag) is dirt cheap.
If you launch a stream of these, what you end up with is something that very much resembles stop-motion animation of what’s going on in that system as each probe snaps pictures as it blasts through. Let’s imagine that we shoot one of these postcards to Alpha Centauri more or less once per workday for the entire 20 years it’s going to take for the first spaceship to arrive. That comes to a grand total of just over 55 pounds of spaceship that we’ve managed to send to another star, which is actually a pretty respectable amount.
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And this is the tremendously clever bit. You can send a pretty respectable mass for a huge (but not impossible) amount of energy and get it there on a reasonable time scale, just so long as you take the spaceship and cut it into very small pieces that you send individually. It’s a way to cheat the underlying physics problem.
This approach to exploring space has all kinds of other implications. You could shoot a post-card sized ship to Pluto and get it there in about a day. You’re not going to get all the big instruments out there, but you can get enough pictures and basic data to figure out what the hell it is you should be looking for when you launch a larger mission. And maybe you send the larger ship to Pluto with the same laser array, but don’t worry about getting it up to such blistering speeds. And you could still get it there in 10 days or 100 days rather than the almost 10 years it took for the New Horizons mission to make the trek.
Meanwhile, that laser array has got to have some other uses. It almost certainly wouldn’t be able to stop Earth-destroying asteroids, but many square miles of high-power lasers could basically be used as a kind of gigantic telescope, leading to extremely detailed mapping of the moon or other rocky planets, or a proactive way to find asteroids, Earth-killers or not. Point being, other applications of the technology would build the case for enduring its costs.
Breakthrough Starshot appears to have already achieved something that has never been done before: The introduction of the first serious plan for interstellar travel that isn’t completely obvious horse shit for a technological or practical reason. It may never get off the ground — there’s a space-sized mess of harsh reality standing between it and Alpha Centauri — but it also may be crazy enough to work.
Follow Ryan Faith on Twitter: @Operation_Ryan

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