By the classical tsiolkovsky equation, a 95% fuel ship has to have an effective exhaust velocity of 1/3 of its final velocity. Protons at c/30 have an energy around 1 MeV. Meaning they'd have to be accelerated through a million volt potential in an ion drive. Or 2+ million volts if we're dealing with heavier atoms that have neutrons. That seems challenging from an engineering standpoint but perhaps doable. Plenty of materials with a dielectric strength >50Mv/m

@RobertCousineau I wouldn't say the below is truly a truly a crux as I don't think fusion is required for this to be likely (although it definitely does make it more likely), but it is a strong characteristic disagreement.

I added a new 10k Yes limit at 66%.

the trouble with a small ship is that the ratio of surface area to mass is worse so it gets pummeled to death by space dust and radiation much faster. At 10% c even cold protons are hitting it at energies around 9 MeV

@JonathanRay 9 MeV protons striking anything will produce gamma rays and neutrons

it might be feasible with fission powered ion drive to get enough delta-v to transfer to a highly elliptical orbit around the milky way which passes close enough to the supermassive black hole to reach 10% c -- if the ship isn't destroyed by radiation or collisions with debris in that high density zone first

never bet on a 2000x increase in a world record (4000000x in terms of energy)

@JonathanRay This makes no sense. Here’s a very obvious counter-example (I guess it’s only a 1500x increase but it’s also only in about 130 years, vs 8000 in this market)

https://en.m.wikipedia.org/wiki/List_of_production_cars_by_power_output#Timeline_of_most_powerful_production_cars

@JonathanRay put a new limit of 10k at 60%.

@benshindel there were a lot of low hanging fruit when cars were first invented and most of that increase on the log scale was frontloaded in the first 20 years

@JonathanRay Space travel was making that kind of rapid progress in the 1950s but it's been a mature industry for half a century

Would tiny lightsails like these qualify?

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

@benshindel if it is capable of sending us a message from alpha centauri, yes. I doubt anything that small could hold an adequate transmitter.

@JonathanRay Why is that a condition? I don’t understand why that’s relevant.

What happens if we pass 9999 but then reverse the arrow of time and subsequently develop such capabilities after we pass back below 9999 CE?

@benshindel Time doesn’t work that way

@JonathanRay say that to yourself in (9999-2024)*2 years

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.

@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)?

@BrunoParga Velocity relative to the station it was built on

@JonathanRay makes sense, thank you.

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

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

a potential crux: https://manifold.markets/JonathanRay/dark-matter-used-as-reaction-mass-b

@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.