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by trhway 15 days ago
NASA and Starlink have already been using ion drives with 10x ISP of chemical rocket engines. Using such drives a 3 stage with existing nuclear reactors as energy source can get to 150-200 km/s.

While it haven't been built yet, nothing seems to prevent ion drive even with 100x ISP of chemical rocket. That means we can get 1000-2000 km/s (acceleration with existing reactors would take about 100 years) and get to the closest star in 1000 years.
1 comments
deepsun 15 days ago
The problem is radiation. Empty space is not really empty, there are stray atoms floating around. Very scattered, but at a high impact momentum penetrate the ship ionizing anything in their way, and making the ship itself radioactive.

Not even talking about stray high-energy particles from distant supernovas and magnetars -- those irradiate ship regardless of its speed.

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sehansen 15 days ago
If "closest star" is Proxima Centauri, we're talking 4.5 light-years. Getting there in 1000 years means an average speed of 0.45% of the speed of light. At that speed less than 0.01 cm of titanium is enough shielding to keep the radiation out according to figure 1c) in my source below. Which makes sense because because this is ~10% of the speed of "normal" alpha radiation which is stopped by just your skin.

"Radiation Hazard of Relativistic Interstellar Flight" by Oleg Semyonov: https://arxiv.org/abs/physics/0610030 via Project Rho: https://projectrho.com/public_html/rocket/slowerlight3.php

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trhway 15 days ago
anything going out there for those long journeys would/should be big, so there would be enough walls, storage of supplies, reaction mass tanks, etc. to provide significant protection.
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TxFkdZ 15 days ago
Not really. Galaxy is 100k ly across, you can make the journey end to end in 1mil years at 10% light speed. Obviously talking about probes/tech, not "biologicals".

1mil years is really short in the grand scheme of things.

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trhway 15 days ago
>Obviously talking about probes/tech, not "biologicals".

human brain has 100T synaptic connections. We already have 2 trillion parameter AI models. Parameter count grows more 3x per year. It means that in 4 years we'll have 100T model. My point here is that by the time we have probes to send even to the closest star, the biological brain would be the inferior option, and most probably we'd even be able to upload, just as fun small companions-observers, a bunch of people brains into what by the time would be a superintelligent 100000T+ parameter AI brain of the probe.

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TxFkdZ 14 days ago
Yeah I never really believed in biological aliens here. But some kind of alien AI thing/tech...quite probable after all this time. Still not sure as there's still a lot of things that can stop it, but it's possible some kind of synthetic thing could replace biology, eventually, everywhere where there's intelligent life.
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