[jonmrodriguez]

Hm, it was just a memory, probably either misremembered Wikipedia or maybe it's in "A Deepness in the Sky". Sorry

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EDIT: Found it. It was indeed from "A Deepness in the Sky", which is fiction. There's a sentence in chapter 17 that says "The Reprise reached ramcruise, 0.3 lightspeed, and sailed endlessly across the depths."

[deletes]

I prefer the Tau Zero ramjet version where they almost reach lightspeed. https://en.wikipedia.org/wiki/Tau_Zero