Consolation prize

This is very, very cool:

Russian billionaire Yuri Milner plans to spend $100 million over the next few years to begin developing the technology needed to build a giant laser array to propel swarms of postage stamp-size spacecraft off on 20-year-long interstellar flights to Alpha Centauri, the nearest star to the sun, the internet investor announced Tuesday.

The tiny 1-gram nanocraft, or “StarChips,” would be equipped with small, ultra-thin light sails and accelerated, one at a time, to 20 percent the speed of light by a powerful half-mile-wide array of ground-based lasers, boosting them to a cruise velocity of some 37,200 miles per second in a few minutes.

From that point on, the tiny spacecraft would sail on their own across the immense 4.3-light-year — 25-trillion-mile — gulf, flying through the Alpha Centauri system about 20 years after launch. Each surviving “spacecraft on a chip” would snap pictures and beam the data back to Earth using tiny on-board lasers, the faint signals arriving four years later.

The G-forces are very high and that would make scaling it up to be a manned starship a huge challenge:

The collimated beam hitting the sail of a nanocraft would accelerate it to cruise velocity in about two minutes, he said, briefly subjecting the craft to 60,000 times the force of Earth’s gravity

When Neil Armstrong landed on the moon in 1969 I expected I would be alive to see colonies on the moon and perhaps even visit the moon myself. That seems very unlikely at this point. But it’s plausible that I will be alive to see the pictures taken from within a million miles from Alpha Centauri. That’s something I didn’t imagine and is a certain amount of consolation.


21 thoughts on “Consolation prize

  1. While that does have coolness factor out the wazoo. I would think using that money, along with some other Roosian multiillionaire’s loot to get that moon colony started would be a better service in the long run.
    Sure thing our respective governments won’t even sniff at it unless there’s sufficient opportunity for graft…or vote buying.

    • Yes, but I would think that Putin would really enjoy the military benefits of getting his hands on such a powerful laser system.

  2. I’ll have to run the numbers, but unless the nanoprobes are made of unobtainium, I think this project will send a lot of melted silicon to AlphaC.

    (Some of the numbers in the article are complete yivshish, but I’ll put that down to its being written by a journalist.)

    • Yeah, 60,000g is a bit much to expect even solid state electronics to survive.

      Accelerate 1 gram from standstill to 37,200 miles per second in two minutes, even with all the different (non-SI) units in there, comes out to a hair under 51,000g – close enough for journalism.
      BUT, that yields about 1.8 terajoules of kinetic energy, supplied by 15 gigawatts of imparted laser power per nanocraft per second.

      Most of that $100 million will go on the power bill.

      • Hm, I wrote a reply, then edited it, but the edit didn’t take and in the process the original reply disappeared too.

        The problem isn’t acceleration, it’s heat. Suppose the light sail is 99.9999% efficient. That means, of the 1.8 TJ applied energy, 1.8 MJ is converted to heat. If we use the specific heat of silicon (other materials are similar), which is 0.7 J/g.K, we arrive at a temperature rise of 2.6 MK. Oops.

        Of course, some of that energy will radiate off again as the craft’s temperature rises. If it’s an efficient light sail, though, that means it’s a white body — no radiation. But suppose the other side is a perfect black body. Now we have to apply the Stefan-Boltzmann law. Suppose we want to keep the temperature below that of boiling water — 373 K. And the blackbody radiator is a square meter (rather ambitious for a 1 gram craft). The S-B law says the blackbody radiation is 1 kW, but the arriving heat flux is 15 kW (15 GW / 1e6 given the assumed efficiency).

        Yes, it looks like at best you’ll be sending melted blobs, and more likely puffs of plasma. As I said, that laser looks more like a weapon than a propulsion tool, at least for this kind of mission.

  3. All this talk of lasers and foreign multimillionaires and the only thing missing is someone saying, I don’t want you to talk Mr. Bond, I want you to die!

  4. When Neil Armstrong landed on the moon in 1969 I expected I would be alive to see colonies on the moon and perhaps even visit the moon myself.

    Me too, but we spent the money on food stamps.

  5. Lessee now …

    These little widgets are stated to have a mass of one gram for the chip and one gram for the sail. Let’s see how much kinetic energy each one would have at a velocity of 0.2 times the speed of light.

    m = 0.002 kg
    v = 0.2 * 300e6 m/s

    E = 0.5 * m * v^2
    E = 0.5 * 0.002 kg * (0.2 * 300e6 m/s)^2
    E = 3.6e12 J

    That’s a lot of energy, and that’s how much for each one. The article states that perhaps a thousand would be launched. In kilowatt-hours, that’s:

    E (total) = 3.6e12 J / widget * 1000 widget * 2.7777777778e-7 kWh / J
    E (total) = 1e9 kWh

    According to Forbes, “In 2011, the world consumed about 4 billion kilowatt-hours (kWh) of electricity.” That’s a fair number to get the scale of this, so let’s use it. As a fraction of the energy consumed on earth in one year, launching these 1000 widgets would require:

    f = 1e9 kWh / 4e9 kWh
    f = 0.25

    And that assumes 100% efficiency.

    So, at an absolute minimum, it would require diverting and storing up one fourth of the world’s energy consumption for one year and delivering it in a total time of 33 hours via a laser onto an area “a few meters across”.

    Nope. Ain’t gonna happen.

  6. It won’t happen, for several reasons, only a few of which have been stated here.

    Anyway, I already read that book, The Mote in God’s Eye. It’s a pretty good book for them that likes SciFi. That was the Mote; an odd green light from a constellation which turned out to be a gigantic laser used to launch some space ships carrying the first intelligent aliens that Humanity ever encountered.

    Why are y’all talking about a moon colony? What for? There’s nothing there and it’s a deadly place to be unless you’re underground. Same with Mars. We can live underground here and not worry too much about dying if we come out to the surface once in a while. The only plausible use I could see for a moon base would be for the worst military assignment in history.

    Sorry, Folks, but colonizing other worlds, if it ever happens at all, is a long, long way off. The images we were fed about such things back in the ’50s and ’60s failed to mention the deadly radiation that’s out there, everywhere, among other deal-killing problems.

    Any why is it that people who seem to be libertarian get all gushy with enthusiasm over gigantic, coercively funded public works programs as long as they’re for space ships?

    So it’s not a matter of whether you favor confiscation and redistribution? You do favor it? It’s just a matter of the excuse that’s used to justify it? It’s like that joke about the woman being offered a few hundred million dollars to have sex with a stranger. She’d do it of course. Then she’s offered twenty dollars or some such;
    “Well! Just what kind of woman do you think I am?!!”
    “We’ve established that. We’re just trying to nail down the price.”

    As far as spending tax dollars on food stamps verses space ships; the food stamps buy you more votes. It’s as simple as that. Just look at it form the most corrupt, vacuous, shithead politician you can imagine and you’ll get it right practically every time. All that money spent on the Apollo Program? All it got the political parties in the long run was some cool film footage no one sees anymore without wondering if it was all a hoax. Ah, our Grand, Progressive public works! It would make any psychotic dictator very proud.

    So this dumbshit billionaire would do better buying food stamps, or hiring a movie special effects lab to fake it for him both now and twenty years from now. “Hey, we launched our nano ships successfully!” Who’s to say they didn’t?
    “Hey, we finally got a message from our nano ships, from another solar system! No really!” Who’s to say they didn’t? Who’d know the difference but a few people who can do math? Regardless, he could have his own army of violent criminals, just like the Democrats, if he only spent it on food stamps instead.

    In other news; my son sent me a very convincing video of a perpetual motion machine the other day. Very convincing that is unless you know the first thing about elementary mechanics, energy, or the natural motion of a pendulum. I bet the machine and video together cost less than 100 dollars too, and so this billionaire should take a lesson from it if he wants to get anywhere in “science”.

  7. While I’m not an expert in the calculations other commenters made, I agree that it isn’t going to happen.
    A 1 gram spacecraft isn’t feasible for low earth orbit, let alone extra solar system travel – the components can’t be made anywhere near that small, and even if they could there wouldn’t be a way to power them or protect them from radiation while up there.
    There is also no way to fit energy storage on them; current deep space technology requires nuclear generators since solar panels are not useful far from the sun.
    I could see him claiming a 1 pound or 50 pound spacecraft, but not a 1 gram spacecraft – but then, the power required from a laser would be even higher.
    I could wonder about a longer pulse of less power, but orbital mechanics and laser hazard distances would get really awkward really quickly.

  8. Often these fantastic assertions are for the purpose of luring idiot politicians into approving public funding, and/or other idiot rich people into donating. Keep an eye on that.

  9. Lyle,
    you forget the space race was directly due to keeping at least parity with the Soviets as they militarized space. He who holds the high ground…

    It would seem that we forced them to quit thinking about colonizing the moon, due to our very quick increase in tech over them, in the scramble to get there. If we had moved a little slower, perhaps by not having JFK push for the moon by the end of the 1960’s, we may have both got out there, with a continued but lower priority. Maybe we would have bankrupted them 10-15 years sooner!

  10. I’m curious, how is a one gram spacecraft 20 years down the road going to send a receivable signal from four light years distance? You can’t tell it how to aim, so you need on board computing and sensors for that. How powerful does a signal have to be to be receivable at four light years? And how do you build a transmitter that light?
    Good luck.

    • “I’m curious, how is a one gram spacecraft 20 years down the road going to send a receivable signal from four light years distance?”

      It isn’t.

      First things first. Consider the process of accelerating it to 0.2 times the speed of light in two minutes, which would require an acceleration of (in round numbers) 50,000 G’s. Would the force that provides that acceleration be symmetric, such that the widget would have no angular momentum when it is done? If not, how would it shed that angular momentum such that it could point an antenna (of any type) toward Earth, all via a widget with a mass of one gram?

      Second things second. Consider how it would determine where Earth is so it could aim an antenna. After the trauma of 50K G’s for two minutes, it wouldn’t have a clue. What would it do? Look at the stars, and with what?

      Third things third. The New Horizon probe that recently flew past Pluto has a plutonium powered power supply and a large antenna. The signal received on Earth from its transmitter is so weak that it takes a very large radio telescope to receive it. Given that weak signal, its bandwidth is so low that it will take nearly two years to transmit all its data back to Earth. So, what would power a transmitter, what kind of transmitter would it be, and what kind of antenna would it use, all such that it is only a part of a widget with a mass of one gram, but could transmit a detectable signal back to Earth over five light years?

      Fourth things fourth. The article states that the transmitter would be a laser. Well, a laser antenna (a laser diode, perhaps) is quite small. Suppose it’s a powerful one, at four watts. Its transmitter would be a narrow beam, which would spread considerably over four or five light years, but it would be 26 orders of magnitude weaker than the star that drowns it out. Think you could see it?

      Nope. Ain’t gonna happen.

      • #4:

        Laser emits coherent light. Stars do not, as far as I know. I’m fairly sure nothing else does this, either. So, it’s possible that it’s signal will still be discernible here, even at low power.

        • A laser is very directional. That’s good — you have a gain antenna at the transmitter. It’s also bad — you need to aim it accurately. A one gram device that can accurately aim a laser is a bit difficult to understand.

          This question can be answered quantitatively. You’ve got transmitter gain, path loss, receiver antenna gain, and processing gain. Receiver gain comes from the size of the receiver: assume you’re using the Keck telescope. Processing gain is filtering (narrow band filter taking advantage of the narrow band source) and time domain processing (very slow code and advanced signal processing to improve the signal/noise ratio). This will tell you whether the signal can be detected.
          You also have the interfering source (the star). For the signal/interference ratio, receiver gain doesn’t help, but processing gain does. I don’t know what processing gain is achievable; 260 dB seems like a stretch to put it mildly (assuming that “26 orders of magnitude” is reasonably accurate, I don’t know if it is).

          BTW, over a significant distance, lasers are not coherent. Every laser has a “coherence length”, and for semiconductor lasers that is quite short. Even for much narrower sources like single mode HeNe lasers, it’s only a few dozen meters typically. But coherence is not required for this.

  11. So it’s a safe bet Mr. Putin wants cover to build a powerful land based laser. Not much of a weapon for offensive operations, but could probably kill incoming ICBMS or MRVS. Russia’s version of “star wars”. At least he’s doing something to protect his people. Our gubmint wouldn’t tell us even if the missiles were on the way… Just another day that would “live in infamy”…

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