Supercee

But Man had always been a restless, persistent creature, and the stars called, and in an incredibly short space of time a highly-ingenious refinement of the theta drive gave him supercee. “What I can’t understand, Psy, is why in the name of Mira the Terrans couldn’t have been admitted to the Federation as soon as they developed supercee. […]” Offhand I’d say that the Terrans, when they hit on the secret of star-driving a planet, which isn’t much of a trick once the supercee principle is clearly understood, decided to go off on a hunt round the galaxy for a see-tee system.

1960, AUTHOR UNKNOWN, Astounding Science-fiction, pp70, 72, & 73; presumed to be an earlier work (1930 or earlier), as quotations 2 and 3 also appear in:

^({1})“[…] A couple of … after the last rescue ship had lif … into space and shifted into the … of supercee, the star exploded.” ^({2})“Surely you know the answer to that one,” he said after a moment or two, “or have you forgotten all about a little thing called the decrement effect?” The Psychologist nodded. “Precisely. The decrement effect. The factor that makes supercee — supercee as we know it, that is — inoperable in intergalactic space.” He looked thoughtful. “I don’t think anyone’s yet evolved a satisfactory theory to account for the existence of the effect. The only thing that’s certain is that it’s tied up in some way with gravity fields — or, rather, with the absence of g-fields.” He shrugged. ^({3})“What I can’t understand, Psy, is why in the name of Mira the Terrans couldn’t have been admitted to the Federation as soon as they developed supercee. […]”

The core was virtually unreachable at supercee velocities. So the Lost Star’s bleep has been sounding for eighty years, and no ship has reached her.