Plan to Send Probes to the Nearest Star | Hacker News Reader

Plan to Send Probes to the Nearest Star

scientificamerican.com

69 pointslaser46 comments

There seems to be quite a bit of handwaving there. So a "gram-scale" space probe is supposed to contain (1) enough shielding to survive 20 years of travel at 20% of the speed of light (2) sensors good enough to capture useful data during the fraction of a second the probe will be in a decent range of the target and (3) communication equipment to transmit the results back across 4 light years?

I think this proposal is very overly optimistic, but it's not like they haven't considered the points you raise.

https://breakthroughinitiatives.org/Challenges/3

Keep in mind there will be thousands of them. even if most get destroyed at least a few would make it.

Perhaps they could travel single file and block instelar debris for each other. And pool their data to effectively get a longer exposure.

Additionally smaller craft present a smaller target. You could tip them with a few inches of depleted uranium, which would make a reasonable ablative shield. Maybe. Either way it's an engineering problem, rather than a physical impossibility as others here are saying.

How could you stay within gram-scale with a few inches of uranium shielding?

999g! You'd also stack it with voids, works better to slow projectiles.

A several-gram spacecraft travelling at relativistic speeds would pack quite a punch. Definitely the most dangerous piece of space junk ever created. It's interesting to imagine making our first contact with intelligent extra-terrestrials by causing a small Tunguska-like event.

The spacecraft themselves would be essentially invisible: A gram-size interstellar probe striking the Earth’s upper atmosphere at 20 percent the speed of light would release roughly a kiloton of energy, indistinguishable from airbursts produced by meter-scale space rocks that regularly pepper our planet at a rate of about once per year.

So they also want to fund an array that would start looking for a robot impact from other civilizations and recognize it as such.

Tunguska is beginning to make sense now.

Doesn't the interstellar medium effectively turn into alpha radiation at significant percentages of the speed of light?

http://www.antipope.org/charlie/blog-static/2016/08/san-trom...

No, particles don't change their nature depending on their speed. Furthermore, you realize that speed is always relative to something (especially in open space, when there's no conventional reference system as it happens in day-to-day talking on Earth)? So, would you say that a particle can be a neutrino w.r.t. a galaxy and an alpha particle w.r.t. another remote galaxy?

Or that it can be an electron w.r.t. a star and a beta particle w.r.t. another? ;-)

> we have a technical term for an ionized helium nucleus travelling at roughly 2% of the speed of light—6000km/sec—we call it an alpha particle.

Technically, an helium nucleus is an alpha particle, independent of its speed.

Edit: an helium nucleus with two neutrons is an alpha particle. An helium nucleus can exist with just one neutron.

I thought that was a pretty choice line. Relax, I think we both know what Charlie actually means.

Yes, but Charlie got the math wrong. It's a lot less than he suggests.

See: https://news.ycombinator.com/item?id=12329322

In addition, if we are talking "gram sized" projectiles, they likely have a front cross sectional area on the order of 10^-4 m^2 or less. That means that we are talking about 16 milliCuries or so. That's about the amount of radiation in a single medical imaging dose, or as much alpha emission as 1000 smoke detectors.

This is what I was wondering. Thanks!

The sun? Seems a little expensive.

$100M for a space mission seems inexpensive, let alone for our first interstellar one. Sending a few people to low Earth orbit costs $70M/person on Soyuz.

$100M is just the amount promised by the billionaire philanthropist. The mission itself would cost several orders of magnitude more.

The article states

"At an estimated present-day price of approximately $10 per watt of laser power, building and operating Breakthrough Starshot’s 100-gigawatt array today could cost as much as $1 trillion."

but goes on to say that the price is plummeting quickly, and so may be affordable in relatively short order.

Okay, but people are gigantic and heavy, and you have to feed them. Also, they usually have to breathe and go poop. They're like hundreds of thousands of grams, and then some, so 70M is less surprising.

Sending a working cell phone into low earth orbit probably wouldn't approach those numbers, I don't think.

If you're an amateur astronomer there one star that's incredibly easy to find, but you can only see it during the day.

I'm pretty sure we get orders of magnitude more illumination from the sun, even in the middle of the night, than we get from any other star.

It's called moonshine :^) at a magnitude of -14, the moon, which has ~0.25% of the brightness of the sun at -26.

All of the visible stars in the sky come to less than 10% of the moon's illumination. https://en.wikipedia.org/wiki/Apparent_magnitude

Sure, we get more illumination from the sun at night than we do from the stars. That doesn't mean we can see the sun at night; we can't.

Can you see the sun through a (reflecting) telescope? What's the difference between seeing a star via its light reflecting off a planet and seeing the star via its light reflecting off a mirror?

Mirrors show the image of what they reflect. Non-reflective surfaces don't.

What's the difference between the image of yourself in a puddle of rain on the sidewalk, and the image of yourself in the dry concrete of the sidewalk? One exists, and one doesn't. There's still light that travels from you, to the sidewalk, to your retinas, but that light reveals essentially nothing about you. The sidewalk has overwritten the information it used to carry.

I was thinking even when the moon was on the wrong side. IIRC we get more sunlight reflected off Jupiter alone than we get from any other star.

Sure but you can't see the sun at night...

Sorry, but are you on drugs?

Solar Probe Plus mission for instance is a $1.2 billion program.

http://www.space.com/9262-nasa-cant-afford-senate-timeline-s...

Playing along.... $100 million for research before sending sounds fine to me.

The sun (8 minutes from earth) is not a star. It is considered a dense helium hole.

I probably had you second thinking your comment for a bit. It's actually a star.

I would love it if this was anything but science fiction but it's not. I have friends who liken traveling to the stars to the journeys of people like Columbus, but people just have no idea of the mind boggling, mind bending, if-you-think-you-grasp-then-you-really-don't distances involved in travelling even to the edge of our own solar system let alone to the nearest star.

It might happen but will never succeed.

Complete no.

Don't be so pessimistic.

But they're not sending big, fat, needs-life-support Columbus. They're proposing gram sized probes propelled by a super "laser". (Dr. Evil scare quotes.)

On Earth, the distances are similarly huge but still manageable.

For example, from me to Latin America 7000 times of what I walk every day from and to work. So in my daily walks that's 20 years worth of walking! Or 40 years for both-ways trip! And yet I've been there.

Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space. [Douglas Adams]

Don't be ridiculous. There's no way that you could have been there. It's simply too far away. Latin America will always be out of our reach.

May as well just throw the towel in now, eh? Why waste money on space when it could be used to feed the starving here on earth?

rolls eyes

Nobody ever achieved anything by not trying, and saying "it's just too far, too hard".

Nothing is impossible, some things are just very, very difficult.

Except that $100 million isn't how much it would cost, its how much that has been promised. To actually send a probe would take several orders of magnitude more money; the amount being quite uncertain because the technologies are not yet developed.

At an estimated present-day price of approximately $10 per watt of laser power, building and operating Breakthrough Starshot’s 100-gigawatt array today could cost as much as $1 trillion.

They're hoping the cost would come down if the tech to build it becomes a cheap-to-produce commodity, like Tesla batteries.

The title says "$100M plan", not a plan for a $100M mission :)

Call me a cynic but... When a philantropist invest so much money in a project. Does he make some return on investment (money, intellectual property, etc.) or is is absolutely real philantropy ?

Directly and financially, certainly no. But it's (usually) good press, (most would say) a good goal, and if it works out because of this $ the philanthropist is famous for helping fund it.

Dark Forest anyone?

Yeah, especially with the tri-solar system they're aiming at. At least our probes wouldn't be as menacing as the Droplet though!

Even if the feasibility of these types of missions is low/improbable, its nice to read about them. They stir the imagination, and create fodder for space travel dreams. and, that's not so bad. It's that, or our children will be interested in becoming only sports figures, actors, engineers for social media companies only interested in more clicks/engagements of advertisements (and not addressing real worldly problems), or worse. ;-)

So would Yuri Milner get to own the couple of patents that would come out of this project?

It's very interesting and odd that a few months ago such an elite group came together to announce this trip and then now a new paper has announced finding of a habitable planet around the sister star system? I sound like a conspiracy nutjob but these seem like highly coincidental announcements..

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