Could we launch a probe at a star to get a better look?

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Sleeper
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Could we launch a probe at a star to get a better look?

Postby Sleeper » Fri Apr 26, 2013 4:08 pm UTC

A couple weeks agohumanity discovered two planets that are more Earth-like than any others ever found. Kepler-62 and its planets are about 1,200 light-years away and "ahead of us" on the galactic carousel our solar system is in, orbiting the galactic center. You can see the area they're in if you're in North America after midnight looking to the right of the North Star, below Hercules and above the Milky Way.

America's spacecraft Kepler found them. Kepler looks at only that tiny patch of sky described above (and shown here).

It's extremely unlikely any human will ever get to visit Kepler-62.

We have some clues that Kepler-62's planets might be habitable, but there's very little information.

Would it be possible to get a closer look?

According to this, a solar sail with a magnetic beam transmitter (producing its own "solar wind") could conceivably get up to 1/10 light speed. So it would take "only" 12,000 years for such a probe to get to Kepler-62. Or 42 years to get to Proxima Centauri, 4.2 light-years away.

There are probably closer stars with better planets than Kepler-62. It's possible that NASA's TESS probe, scheduled to launch in 2017 (but I always assume delays), could find better planets much closer. TESS will look not at a tiny patch of sky but anywhere in the sky, so it could look specifically at the closest stars to Earth. Hopefully we can get better clues as to their atmosphere and potential for habitability. If we found something really interesting, we would want to take a closer look and maybe even launch a robotic probe toward it. This would likely require a project lasting decades or centuries.

What would it take to establish a generations-long program to launch and manage a robotic probe as it makes its long journey across interstellar space?
Last edited by Sleeper on Fri Apr 26, 2013 6:48 pm UTC, edited 1 time in total.

speising
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Re: Could we launch a probe at a star to get a better look?

Postby speising » Fri Apr 26, 2013 6:05 pm UTC

a stable hereditary form of government.
you'll never get a project with this timeframe done in a democracy, where plans have to reap benefits in time for the next election.

btw, the beam for the solar sail would be transmitted from earth/some orbit to push the craft. it wouldn't be installed on the craft itself.

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Re: Could we launch a probe at a star to get a better look?

Postby lgw » Fri Apr 26, 2013 7:39 pm UTC

Sleeper wrote:According to this, a solar sail with a magnetic beam transmitter (producing its own "solar wind") could conceivably get up to 1/10 light speed. So it would take "only" 12,000 years for such a probe to get to Kepler-62. Or 42 years to get to Proxima Centauri, 4.2 light-years away.


Not a very practical idea in the first place, I fear. A solar sail is large and friction in space isn't 0, so I'm not buying this 0.1c claim without some math, but even if you somehow reached that speed your sail wouldn't last long. Also, you have no real way to brake (though maybe we're satisfied with a quick fly-by). Also unstated is how many years of acceleration would be required to get to 0.1c at some reasonable beam power.

But lets handwave all of that, and say we can get a 100 kg probe up to 0.1c. That's going to take about 1017 J of energy. If we're wildly optimistic and assume a 1% overall efficiency, that's 1019 J. That's actually not so bad: if spread out over, say, a century the yearly power cost would be well within NASAs budget by my math (roughly 30 TWH per year, at say 10 cents/KWH gives $3 Billion/year). But you couldn't possibly have that beam emitter inside the atmosphere - you'd need something up in orbit that you could beam power up to from very spread-out ground stations to avoid superheating a column of air - either in geosync and working when not in eclipse, or in Asimov orbit (hovering far over a pole with a solar sail - and I read that 20+ years ago, so I could be misremembering Azimov as the originator) for a continuous beam. So we'd need to really push our current tech level to put something like that in high orbit, and the result would be NASA owning the most powerful weapon ever built.

speising wrote:a stable hereditary form of government.
you'll never get a project with this timeframe done in a democracy, where plans have to reap benefits in time for the next election.


Historically, hereditary governments tend to fail every 3rd generation. However, a hereditary government with the most powerful weapon ever built - well, who cay say.
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scarecrovv
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Re: Could we launch a probe at a star to get a better look?

Postby scarecrovv » Fri Apr 26, 2013 8:44 pm UTC

lgw wrote:the result would be NASA owning the most powerful weapon ever built.


I think I'd be ok with that.

NASA: Please fund the mission to Europa.
Congress: No.
NASA: Fund the fucking mission or we'll use the orbital laser cannon to carve dicks into the roofs of your houses. Don't think we won't either. Look at what we did to Mars back in 2013!
Congress: All right! All right!

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Re: Could we launch a probe at a star to get a better look?

Postby thoughtfully » Fri Apr 26, 2013 9:20 pm UTC

I don't know about the durability issue, but slowing down is a solved problem. Basically, a section separates off and reflects part of the beam into the remaining portion. I'm pretty sure it's in the Wikipedia article on solar sails. Alternatively, read Indistinguishable from Magic by Robert Forward. Lots of fun stuff in there.

I'm pretty sure durability isn't that big an engineering problem, and tractable with existing tech and testing procedures. There's coverage of that also in the Wikipedia article.
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Re: Could we launch a probe at a star to get a better look?

Postby lgw » Fri Apr 26, 2013 10:33 pm UTC

thoughtfully wrote:I'm pretty sure durability isn't that big an engineering problem, and tractable with existing tech and testing procedures. There's coverage of that also in the Wikipedia article.


I'm having a hard time imagining how to make a lightweight solar sail that wouldn't just ablate away as 0.1c hydrogen rains down on it. I'd expect anything larger would go right through the ship. At that sort of speed I'd expect it to be like a wooden sailing ship - a constant slow-motion explosion that only stays afloat if you repair it faster than it's falling apart.
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Re: Could we launch a probe at a star to get a better look?

Postby Copper Bezel » Sat Apr 27, 2013 1:03 am UTC

To be fair, all biological organisms are exactly that, too. But of course, that's also not "existing tech."

Does the relative speed of the beam vs. the craft really have to be 0.1c, though? I mean, you need a maximum of at least 0.1c to catch up with the craft at "cruising speed"; when the beam is at 0.1c, and the craft is at 0.09c, the relative velocity of the "wind" is just 0.01c. Couldn't you start lower and step up? Like you said, the acceleration doesn't happen over a short period of time.
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Re: Could we launch a probe at a star to get a better look?

Postby scarecrovv » Sat Apr 27, 2013 3:24 am UTC

Copper Bezel wrote:Does the relative speed of the beam vs. the craft really have to be 0.1c, though? I mean, you need a maximum of at least 0.1c to catch up with the craft at "cruising speed"; when the beam is at 0.1c, and the craft is at 0.09c, the relative velocity of the "wind" is just 0.01c. Couldn't you start lower and step up? Like you said, the acceleration doesn't happen over a short period of time.

It's not the beam that's impacting at 0.1c. The beam is made of photons, which will be impacting at 1c by definition. The massive particles hitting at 0.1c are the interstellar medium, and if you want to travel at 0.1c there's no way around that.

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Re: Could we launch a probe at a star to get a better look?

Postby Copper Bezel » Sat Apr 27, 2013 3:41 am UTC

Oh, right. = / I thought that the original post was suggesting a particle beam (in contrast to a laser) and missed the screamingly obvious problems on the other side of the sail.
So much depends upon a red wheel barrow (>= XXII) but it is not going to be installed.

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Re: Could we launch a probe at a star to get a better look?

Postby Sleeper » Sat Apr 27, 2013 7:30 pm UTC

So maybe the solar sail wouldn't work. Maybe we'd use a different propulsion method.

I'm curious about how close we'd have to get to be able to tell whether a planet actually has life.

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Re: Could we launch a probe at a star to get a better look?

Postby Copper Bezel » Sat Apr 27, 2013 8:36 pm UTC

Depends on the key you're looking for and the level of certainty required. For instance, this exoplanet was discovered 129 light years away, but it's a gas giant large enough and reflecting enough light from its star to actually peg the composition of the atmosphere. If you could do the same with a dirt ball (at a much smaller distance, natch, given the smaller target and things,) and if you then detected free oxygen, that planet would be likely to harbor life. So, potentially, many light years away, still.
So much depends upon a red wheel barrow (>= XXII) but it is not going to be installed.

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