I figure YES by three lines or reasoning:

1. Antimatter. It's the universe's cheat code. Or some other form of hand-wavium. Physics is so clearly not all figured out yet.

2. It's tough to look at the last 1000 years of progress, then look ahead to the next 8000 and think, "oh that'll be too hard."

3. Doesn't really matter if it happens or not. Mana will be won or lost based on how this market fluctuates short-term. I think the overwhelming majority of bettors will read this as "is 9999 sufficiently far away to be sci-fi?"

I think a light sail that's very thinly distributed wouldn't necessarily have issues with collisions. Especially if different cells only connect intermittently with each other. If there's a collision then maybe a few cells are lost and that's it, not the whole spacecraft.

There's probably a way of doing it with a swarm of light sail cells that can coordinate with each other and self-heal

Accelerating something like that to 10% the speed of light doesn't seem that hard

Just need a big laser

Could even make it more exotic by having the sail cells gather matter from collisions to make more cells. Or fire particles at the cells along the path of the laser beam for them to use.

The idea of feeding the cells with a particle beam is nicer because the relative velocities can be, in theory, adjusted to make the collisions very mild

Considering that particle accelerators are technology we already have, doesn't seem that implausible we could get something like this to work by the year 9999

If you allow for beaming light and matter at a swarm of cells like this then it also allows you to do tricks like use the matter as propellant to slow down past a certain point. Or split the swarm in 2 and use one half as a mirror to slow the other half down. All kinds of tricks are possible in theory.

@MalachiteEagle Light sails are hopeless because they accelerate so slowly that you can't get much acceleration from a single close approach to a star. You'd need a series of thousands of hyperbolic close approaches to different stars, and you'd need to be able to fold away the light sail to reduce drag in between the close approaches.

in theory a light sail could get up to speed eventually, but it would take way more than 7000 years.

@JonathanRay i'm talking about light sails illuminated by powerful lasers in the above comments

@JonathanRay therefore possible to achieve 10% rapidly

the energy requirement for laser propulsion is absurdly high. The current total global energy production going to a 50% efficient diode laser would be enough to accelerate a 500kg probe at about 1g. You need about 1/10 of a year at 1g to get up to 10%c at a distance of 0.05ly. Then you have unavoidable beam spreading proportional to wavelength/diameter. Diode lasers are limited by the band gap, and the highest band gap is under 7ev which is a limit of 177nm. With an aperture of 50m that's going to spread out to 1674km at a distance of 0.05ly. If you go into the soft x-ray wavelengths (1nm) the laser efficiency will be less than 1% and then the beam only spreads out to 9.5km. There's unavoidably a minimum probe size for any complex electronics to survive the journey, because of radiation from from interstellar neutral hydrogen which can't be deflected colliding with it at 0.1c = 9MeV. This minimum thickness of shielding is probably >500kg/m^2. See below calculation that you'd need 33cm of lead = 3300kg/m^2 to match the radiation levels on a mars trip.

@JonathanRay say the meat of the probe is a very narrow cylinder with lots of shielding in the front of it, and then you have a very wide sail around that, to keep the total mass under 500kg. The beam spreading issue still makes the energy requirements prohibitively high, and you'd probably also have problems with radiation embrittlement of whatever you use to make the sail.

@JonathanRay here’s a simpler way to think about this if you move away from the single massive probe idea. Instead of a 500-kilogram craft trying to pull off 1 g of acceleration, imagine a large swarm of ultralight sail-cells, each carrying only tiny amounts of mass and extremely miniaturized electronics. You can spread your total payload across thousands or even millions of these minuscule craft, which drastically reduces the shielding requirements and solves a lot of the problems you raised. Because each individual cell is so light, it doesn’t need anything close to 33 centimeters of lead. It can rely on thin, well-chosen materials or even just radiation-hardened components, and if some portion of the swarm fails, enough cells can survive to keep the mission going.

With this approach, you don’t need to pump out 1 g of continuous thrust. You can work with a much gentler acceleration—like a fraction of a g over weeks or months—powered by a sustained laser beam or phased array. The moment you shed the requirement for huge acceleration in short bursts, the energy requirements become far less daunting. There are already concepts for phased-array lasers or free-electron lasers with better-than-1% efficiency, and they can operate at near-UV or X-ray wavelengths. Even with diffraction limitations, a large phased array can form a beam that stays tight enough across interstellar distances to impart enough momentum to these lightweight sails. The idea is to let the swarm soak up laser photons over time rather than trying to slam it with all our global energy in one enormous pulse.

If you do the math in a simple way, radiation pressure acting on a perfectly reflecting sail provides twice the laser power divided by the speed of light as the net force. Over a long enough period, the resulting low but steady acceleration adds up to 10% the speed of light, and you don’t have to waste power aiming for any quick 0-to-60 sprint. Because the sails are so light, the total thrust needed per cell is easily within range if you use a big but realistic power source and spread it out over a timescale of months. Beam spreading isn’t fatal for a swarm spread over kilometers instead of a single compact craft, and each cell can collect enough photons over its small cross-section to keep accelerating. You can even imagine strategies to mitigate interstellar collisions, like letting the swarm spread out so the cross-sectional density is low, or using partial sacrificial shielding on the forward cells.

It’s basically a completely different engineering setup than the 500-kilogram probe you’re calculating for. When you swap that big, monolithic spacecraft for a cloud of many lightweight, resilient pieces, the trade-offs change dramatically. The swarm can take some hits without failing entirely, and it can operate on much smaller per-unit power and shielding budgets. That’s how it becomes plausible to shoot for 10% the speed of light without requiring the absurd scaling you get from the single heavy-probe scenario.

Tritium is nearly impossible to store cryogenically because of the decay heat and short half life. If you store it as T2O you get about the same energy per kg of fuel as fission. Liquid T3N could be 60% better. You'd probably have to produce it in situ from neutron irradiation of lithium, just like every modern fusion warhead. Your ship needs facilities to separate the tritium from irradiated lithium. It also needs a very thick lithium blanket around the reactor to max out the neutron economy since there is no external source of tritium or neutrons. D-T produces one neutron and then you need that neutron to produce tritium from Li-6. There's no neutron multiplier without fission or some Be n-2n reactions.

Any sort of fusion other than D-T is hopeless from an engineering breakeven standpoint. If you do get D-T to work, the dry mass ratio won't be great and that's bad for delta-V The combined cycle of 6Li+n -> T + He4 + 4.8MeV and D+T-> He4+n+ 17.6MeV means you're using about 8 AMU to make 22.4 MeV so the specific impulse is sqrt(2*22.4MeV / 8amu) = ~7.7% c, ignoring the beryllium or whatever you use to boost neutron economy. So with a 95% fuel fraction and perfect efficiency the speed would max out at ~20% c.

with current technology, suppose you have a fully fueled starship in space, attached to a stage that just uses solar ion drive to get it into a highly elliptical orbit with an apogee beyond pluto and a perigee as close as it can get to the sun without being destroyed. Then you save all that fuel to burn hard upon closest approach to the sun, taking full advantage of the oberth effect. Since you're going about 9 times faster than LEO, and energy is force times distance, you get 9 times more kinetic energy from the burn. Starship's delta-v is about 9km/s so you'd get a v-inf around 27km/s without even using a jupiter gravity assist

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

@JonathanRay and if you want to protect it with a magnetic deflector there are problems:
1. a lot of the interstellar medium is neutral hydrogen
2. deflector drag scales as the square of ship radius, but available fuel scales as the cube of ship radius, so this probably doesn't work at small scales.

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