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Comment by sehugg | Hacker News Reader

There's a $100 million effort to develop tiny spacecraft that are accelerated to 10%-20% the speed of light with ground-based lasers: https://en.wikipedia.org/wiki/Breakthrough_Starshot

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Today at 2:55 EST Philip Lubin, who is involved with the Starshot project, will present some work on the study he is doing for NASA investigating the feasibility of this.

You can watch it live here: http://livestream.com/viewnow/NIAC2016

The craziest thing to me is that if we sent a generational spaceship there that was expected to take 1,000 years, it seems likely that better technology would allow the next generation of spaceships to get there much faster. So by the time the 1,000 year spaceship arrived, there would already be people there!

Or maybe they'd rendezvous and bring them "up to speed" so to speak ?

it would be better to just 'seed' the tiny starshot spacecraft with human embryos that could litter the planet and then develop on arrival.

See James P. Hogan's Voyage from Yesteryear. It involves a post-scarcity civilization seeded in much the way you suggest.

https://en.wikipedia.org/wiki/Voyage_from_Yesteryear

Right because human babies let alone embryos do so well on their own.

that's why we also send self-replicating nanobots along with them.

For their extensive experience in child rearing.

no problem, we train them with a convolutional neural net w/ examples from earth to provide for them. should suffice until about an age of 7 after which they'll just continue to use the nanobots to provide raw materials.

Adults from later, faster spacecrafts could raise the babies.

we'll also send send self-replicating nanobots

Why wouldn't they just bring their own? Or make some?

This is a known paradox, I forget what it's called though. The concept is that it's arguable that any long-term space travel is pointless because there will always be a faster ship surpassing it as the originating civilization improves its technology, and so on for that faster ship. So, it's irrational to ever launch anything...

Apple has adopted a similar philosophy with their MacBook Pro line of computers.

I haven't laughed so much in days. Thank you.

On a tangent with this topic, you guys should treat yourselves with a short sci-fi story named "The road not taken".

I just finished reading the entire novel series that Turtledove spun out of that short story concept. It's really good, well-researched and imaginative.

This is known as the incessant obsolescence postulate: http://arxiv.org/abs/1101.1066

Seems like you'd reach a point where it becomes worth it even with continuous improvement. If the speed of light really is a speed limit, then you'll get to a point where the maximum theoretical improvement is still some small amount. If there's a way to go faster than light, then you'll get to a point where it only takes two seconds to get to your destination.

Even without the speed limit, you can expect to reach this point. Let's say your technology gets 10% faster every 25-year generation, you should launch a 200-year trip but not a 250-year one. We'll probably keep improving at that pace or better for a few iterations at least, but eventually space travel will be a stable technology, speed improvements will be rare and incremental, and 1000-year journeys will be justified.

Right, barring time travel, once you can make the voyage at all, you'll always reach a point where it makes sense to depart on it. If you invent technology that takes a million years to arrive, then you have a maximum deadline of a million years. Past that point, even instantaneous travel won't be worth waiting for, if your goal is simply to get there as early as possible.

>>This is a known paradox >>So, it's irrational to ever launch anything...

That faster ship just won't appear out of the blue.

You need to launch slower ones to get to the faster ones.

Its like the original inventor of the car opting not to build it because someday there would be a Ferrari.

Yup -- This is precisely the answer to the question, so it thus remains an unresolvable paradox.

But you don't have to send your people 1000 years away.

Improving the speed of a 1000-year ship may only require improvements in propulsion or structure (lighter ships). There are nearby incentives to create better propulsion and structure. We do not necessarily have to launch a 1000-year ship to create a 500-year ship.

> So, it's irrational to ever launch anything...

Sounds like the interstellar version of Zeno's paradox.

But technology that would be able to send spaceships significantly faster would probably cost significantly more, so it might not be worth pursuing given the cost.

Moore's law never stopped anyone from making chips with current technology.

It was a theme it this cartoon: https://en.wikipedia.org/wiki/Once_Upon_a_Time..._Space

Maybe there could be a kind of factory-ship that was built to be self-improving, so during those 1000 years it would improve itself and increase it's speed.

If you're limiting it to generational ships then there isn't much improvement to be made, we can still only accelerate at ~1G. The only variable is how long that acceleration can be maintained.

After we build the laser it might not cost that much more just to keep a constant stream of these guys going to the planet relaying their information back along the stream. Effectively giving us a streaming feed of what's happening on the planet.

A single probe in orbit could obviously do this but with this idea there's no way to slow down.

There's a way to slow down:

http://www.lunarsail.com/LightSail/rit-1.pdf

>The lightsail is built in two sections, an outer doughtnut- shaped ring, and an inner circular section 30 km in diameter. This 30 km payload section of the sail has a mass of 71 metric tons, including a science payload of 26 metric tons. The remaining, ring-shaped "decel" stage has the mass of 714 metric tons, or ten times the smaller payload "stage". The central payload section of the sail is detached from the larger stage and turned around so that its reflecting surface faces the reflecting surface of the ring-shaped portion (see Fig. 4). At a time 4.3 years earlier, the laser power from the solar system was upgraded to 26 TW (there are 37 years to get ready for this increase in power). The stronger laser beam travels across the space to the larger ring sail. The increased power raises the acceleration of the ring sail to 0.2 m/s2 , and it continues to gain speed. The light reflected from the ring sail is focused onto the smaller sail, now some distance behind. The light rebounds from the 30-km sail, giving it a momentum push opposite to its velocity, and slowing it down. Since the smaller sail is 1/10 the mass of the larger one, its deceleration rate is 2.0 m/s2 , or 0.2 g. The light flux on the smaller sail has increased considerably, but it is only two-thirds of the maximum light flux that the sail can handle.

This is from the same people who announced the "Breakthrough Message", an open competiton with a $1 million dollar prize pool, whose details were "to be announced soon". [1]

The press release was made in July 2015, and there has been no communication about it since then. I'm not sure how seriously to take this group.

[1] http://www.breakthroughinitiatives.org/Initiative/2

Also, https://en.wikipedia.org/wiki/Starwisp

0.20 c

Unless "The Moties" send one here, first :-)

Yet another comment plugging a story involving some novel interplanetary travel (this one involving a species from a red dwarf): https://en.wikipedia.org/wiki/The_Mote_in_God%27s_Eye

This should be the top comment! Not the guy poo pooing on the idea of checking out this planet.

(ignore what I said here)

The laser is only on each device for 10 minutes. And there are 1,000 of them. So the hope is that at laest 1 in 1,000 will make it.

if even a tiny fraction of those 1000 tiny probes hit that planet at 20% of speed of light, could that pose a problem? it sounds like a shotgun approach, not so figuratively, using pellets loaded with plutonium.

The probes would each be only a few grams, so they'd have about 10^13 J of relativistic kinetic energy, or a half kilotons of TNT equivalent. This can be compared with the 15 kilotons for the (small, by modern standard) Little Boy atomic bomb. So it's probably noticeable for any inhabitants in the area, depending on how the energy is dissipated in the atmosphere, but still quite small on the scale of a planet.

It should be noted that meteors explode with Hiroshima-like force fairly regularly within Earth's atmosphere, on the order of once a decade or so. It happens high up enough that nobody notices beyond an occasional light show. The meteor explosion which hurt a bunch of people in Chelyabinsk a few years back was about 500 kilotons.

cool, good to know that raining down a bunch of probes in this manner would most likely be a pretty light show. still i wonder about the plutonium aspect of this?

it might be prudent to first consult with the legal experts and diplomats of the Galactic Council, to clear this type of activity with them first, minimize interpretation of this probing as a hostile interstellar act.

I don't think the plutonium would be enough to have any real effect, although it might irritate the inhabitants if there are any. Certainly, we've put far more plutonium into Earth's atmosphere by blowing up thousands of nuclear bombs in it, and we survived.

Clearing it with the Galactic Council definitely sounds like a good idea. Do you have their phone number handy? I seem to have deleted their contact info by accident.

And so many of those people were injured because they went to a window to see the spectacle, not knowing about the shock wave that was coming.

It made me realize that the civil defense films we watched in the '50s weren't so misguided after all:

https://www.google.com/#q=when+you+see+the+white+flash+duck+...

Indeed, that's pretty much what "duck and cover" was all about. There was even a school teacher in Chelyabinsk who apparently remembered her Cold War drills and had her students take cover, saving them from injury.

>>So it's probably noticeable for any inhabitants in the area

An intelligent civilization with a 1000 year head start whose presence was just proven by device that arrived at 10% the speed of light would pretty much scare any government on earth.

I would assume it would scare the aliens there too.

Also at 10% the speed of light the probe zips by the planet in a fraction of a second. There's no slowing down in this scenario.

Could they carry mini solar sails to slow down? Solar parachutes if you will.

Or if we sent them in single file several seconds apart they could each relay what they see to the ones behind them and then back to us. Effective oh giving us a long exposure.

There are ideas for slowing them down and even returning them back to Earth, at least in principle:

http://www.centauri-dreams.org/?p=31913

Nothing that could be implemented in any foreseeable future though.

You can slow down - just that the probe won't remain intact. But perhaps that isn't necessary for the probe to be useful. We can also use these space probes to do geological and atmospheric surveys of the planet when they arrive.

Simply: we slam the probe into the planet, a few milliseconds after it transmits the final images. One gram going at 20% of the speed of light has kinetic energy that bears comparison to the Hiroshima bomb.

At a steep angle of entry, the huge entry glow will give a reading of the atmospheric molecular makeup. And if we can ionize some of the crust, massive space telescopes can get a spectroscopic measurement of the composition, four light years away.

Let's hope any alien race living there doesn't have the same idea and send a few probes to smash in to Earth.

That would be like Christopher Columbus, mid-Atlantic crossing, encountering a gunpowder-equipped Mayan navy going off to conquer Europe. Not likely.

now that's a way to say Hi to a foreign species! there isn't high chance this wouldn't be considered as an act of hostility, and if they would check our history of our current world, they would probably just decide to erase this dangerous species from the face of the universe for greater common good.

I think we both know humanity's interstellar destiny is to become the murderous alien invaders we've faced down in so many movies.

This is the coolest project I've heard about in a while. Thanks for sharing!

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