Will any spaceship exceed 10% of the speed of light relative to its planet of origin before 9999?

Resolves YES when humanity becomes aware of any spaceship travelling at >10% of the speed of light (either domestic or alien origin)

Resolves no in 9999 but it could be re-resolved if we meet aliens after 9999 and they say they were totally doing that before 9999.

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predicts NO

a highly elliptical orbit passing close to a neutron star or black hole to take advantage of the oberth effect is one way of achieving this but you get less than a second above 10% c unless it's a supermassive black hole.

predicts NO

@JonathanRay and the ship would be spaghettified

Before 9999 or before 10,000?

More importantly, what if such a ship is built and launched from space, with no identifiable planet of origin (e.g. assembled in a multi-planetary station)?

predicts NO

@BrunoParga Velocity relative to the station it was built on

@JonathanRay makes sense, thank you.

predicts YES

Project Daedalus, with 70's (expectation of) very plausible tech, was estimating it probable to get up to around .12c using a fusion rocket.


predicts NO
predicts NO

@JonathanRay some way of interacting with dark matter efficiently to push it around would make this a zillion times easier because then you don't have to carry all the reaction mass with you.

@JonathanRay Ridiculously easy. If you don't need to throw away reaction mass to accelerate, it's just a matter of dumping energy into your motor. For example, at 100% drive efficiency, a 100 ton craft with a 1 Gigawatt reactor could reach .1 c in ~41 years. Adjust for whatever efficiencies your drive might have and how good a reactor we might have once such a thing would be discovered. For many values, the time required is quite short.

Still voting No on that question though. I think dark matter really only interacts with gravity, and there's no way we're getting some kind of gravity-wave-ramscoop in 100 years.

Yes on this question though. 9999 is a long time to build Project Daedalus.

predicts YES

Plasmadyne techniques seem plausible and could probably reach 0.2 c or so using dynamic soaring + shear sailing + Q-Drive as suggested by Jeff Greason. Alternatively there's various beam methods - Andrew Higgin's suggestion to use a pair of large (1000 km diameter) superconducting loops in low counter-rotating orbits seems promising and could drive 0.1 c beams at potentially very high specific power. Laser sail propulsion is the highest TRL but also less efficient - though if we colonize space my guess is our civilization will large enough by 9999 to make laser propelled 0.1 c probes pretty viable even if all the other propulsion methods didn't work out for some reason.

predicts NO

@AlphaCoronae Dynamic soaring won’t do much because escape velocity at surface of the sun is only 0.2% c and you’d need repeated approaches. Can’t get much energy from a single hyperbolic flyby.

Shear sailing won’t work because any significant difference in velocity between the pellets and the craft will destroy the craft

predicts NO

Pu239 yields 210MeV per fission and weighs 239g per mol. This works out to an exhaust velocity of 4.3% c with 100% burnup and 100% efficiency. Real world will be 1/9 of that energy at best, so a specific impulse of 4.3/3 = 1.4% c

It seems unlikelyish that engineering break even on fusion is even possible. Antimatter ala Star Trek is out of the question as there is no way of storing it in large quantity.

Voyager is going like 5x the max theoretical hydralox exhaust velocity but half of that came from gravity assists which won’t be available for relativistic travel. The motion of nearby stars is way too slow for gravity assists to matter.

Fission reactor based ships are going to have a worse ratio of fuel to dry weight than chemical rockets because of all the reactor hardware.

So it seems pretty safe to say that without fusion or insane numbers of stages (whose size increases exponentially) we won’t get beyond 5% c with a self-powered craft.

bought Ṁ80 of YES

@JonathanRay We achieved engineering break even on fusion in 1952. Not in a sense practical for power production, but for a sufficiently huge nuclear pulse vehicle it'd be fine.

Your question doesn't require the vehicle be self-powered anyway.

predicts NO

@AlphaCoronae True it doesn't have to be self-powered. The laser-mirror thing would work if we were willing to spend approximately the current earth's entire annual energy output on a space-based diode laser (atmospheric effects causing 200 arcseconds of beam-spreading are prohibitive) to accelerate a voyager-sized probe to 10% c. Not sure how that would ever be economical for any purpose other than acquiring more resources to run more compute after our starting star system had been saturated to its capacity for compute.

The series of small H-bombs is a nice idea, but the weight percentage of burnt-up fuel in those is not great. A W80 (which is optimized to be lightweight for missiles and such) has a max yield of 150kt=6E14J and weighs 130kg (1.15kt/kg). Assuming 100% efficiency of converting the yield to kinetic energy (lol) this works out to an effective exhaust velocity of 3000km/s = 1%c, which is worse than my above calculation. Larger size increases efficiency, and Tsar Bomba if it had used a uranium tamper would have yielded 100Mt and weighed 27000kg, or about 4kt/kg, so it would have had about 2x the effective exhaust velocity of the W80 but still way below what we'd need to get to 10% c with a reasonable number of stages. The W88 was in the middle at about 1.5kt/kg

predicts YES

@JonathanRay B41 got 5.1 kT/kg, which is a bit higher.

On a larger scale Edward Teller looked into the design of much larger and more mass efficient nukes in Ripple, and suggested a derived gigaton weapon in the 25-30 ton range for asteroid deflection, corresponding to a maximum possible Ve over 0.03 c. You'd need a rather colossal worldship to employ it, of course, but the theoretical limits of nuclear bomb propulsion could be high.

predicts YES

7,976 years is a long time! Conditional on human survival and travel speed of 0.1c being physically possible it seems a safe bet this will happen.

How big does it has to be to count as a spaceship? Would nanosat-size count?

predicts NO

@ArmandodiMatteo Already answered below: “A spaceship, at the bare minimum, has to contain either a computer or a brain, and some capability for receiving and transmitting signals intelligently. So a bullet or a relativistic jet is not a spaceship.”

Also keep in mind my calculations below about collisions with protons in the interstellar medium providing 15 million times the usual flux of radiation that you’d get from cosmic rays. That would probably destroy your nano bots.

predicts YES

@JonathanRay 7900 years is a long time to develop capabilities to rad-harden stuff. Plus all that flux is in a single direction, making the problem easier than the equivalent issue were we to scale up the number of cosmic rays.

bought Ṁ10 of YES

https://en.wikipedia.org/wiki/Breakthrough_Starshot this concept seems like it would fit the description. Beyond today's technology but not outrageous, reduces this to "will humans go extinct first" question imo

predicts NO

@Tomoffer Potential problems with that:

  • Collisions with space dust at 10% c destroy your ship

  • Energy efficiency per unit of momentum imparted is like 100 million times worse than ion drive

  • So much laser energy is required that a decent acceleration would vaporize your ship, and reflect off the atmosphere and damage the transmitter

predicts YES

@JonathanRay these problems are of course not solved, but at least discussed with possible solutions mooted:

They're certainly not saying any of this is easy, but they did give it quite a lot of thought.

Stationary space-ships that are very, very far away also count for YES?

predicts NO

@Simon74fe It probably makes no difference because we’d have no way of detecting spaceships so far away that they get 10% c for free from the Hubble constant. But the spirit of the question is a spaceship capable of moving at 10% c relative to the origin of that spaceship.

predicts YES

@JonathanRay Woah, that's a totally different question. The title is explicit that it's relative to Earth?

@IsaacKing If you go far enough away, the fabric of space moves at 10%c relative to Earth.

predicts NO
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predicts NO

@Mqrius The distance for that is 200 million light years

predicts YES

@Mqrius Right, so as per the original question, this should resolve YES in that case.

I see that Jonathan has now changed the title to a completely different question, which seems unfair. Not only due to the expansion of space, but also because it means this could now resolve NO if an alien civilization constructs a ship capable of such local speeds but humanity never does.

predicts NO

@IsaacKing Alien ships traveling 10% c relative to their origin would always count. Locally stationary alien ships >200M ly away would not automatically count just because of the 10% c expansion of their space relative to earth. The title change only matters if we discover an alien ship >200M light years away without either us or the aliens having 10% c tech. Since this is basically probability zero so we can cross that bridge when we get there.

predicts YES

@JonathanRay Well clearly you believed it mattered enough for you to want to change the title, so it seems hypocritical to now say it's basically probability zero and I shouldn't worry about it. If it doesn't matter, the original resolution criteria would have been fine!

By the way, how did you get to 200 million ly? I'm getting 1.4 billion. Hubble's constant is 70 km/s/Mpc, 10% of c is 29979 km/s, so it's 29979/70 = 428 Mpc.

predicts NO

@IsaacKing The first google result said 500km/s/Mpc in the blurb and I went with that, but you’re right.

predicts NO

@IsaacKing Sorry, I changed the title because I am more interested in figuring out whether it is possible to construct a spaceship with a delta-v of 10%c than figuring out whether it is possible to communicate over 1.4 billion light years. I don’t want people to waste time speculating on the latter. Feel free to create an insurance market if you think I might misresolve it according to the original criteria.