Actually, even something as primitive as a NSWR (https://en.wikipedia.org/wiki/Nuclear_salt-water_rocket) can reach a good percentage of the speed of light after basically processing a comet for fuel. From the Wikipedia article:

"The design and calculations discussed above are using 20%-enriched uranium salts. However, it would be plausible to use another design which could achieve much higher exhaust velocities (4,725 km/s) and use a 30,000-tonne ice comet along with 7,500 tonnes of highly enriched uranium salts to propel a 300-tonne spacecraft up to 7.62% of the speed of light and potentially arrive at Alpha Centauri after a 60-year journey."

Sure, not 99% the speed of light or continuous 1 g acceleration but IMHO good enough for an oversized nuclear squirt gun.

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stouset 3 hours ago | parent | next [-]

Still, this is many, many orders of magnitude short of what’s being discussed. Essentially the forefront of technology could get us to just barely speed past our nearest neighbor in one human lifespan.

	▲	saalweachter 2 hours ago \| parent [-]
		That's why we need to find a globular cluster with metal-rich planets, and take a generation ship over there. Sure, a thousand generations will live and die along the way, but once we get over there, you've got stars every 0.1 ly or so, and with very plausible future tech, you could navigate between them in a few years. You could set up a proper starfaring, interplanetary civilization, with tradeships either going back and forth between two neighboring systems, or winding on long, never-repeating routes, visiting a dozen or so star systems in a human life. (Most globular clusters appear to be old and metal-poor, and we haven't found a lot of planets there, and this only works if you find a globular cluster where ~every star can support a colony.)

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metalliqaz 2 hours ago | parent | prev [-]

Imagine such a complex machine working without fail for 60 years. It's just not plausible in my view.