Captive of the Centaurianess by Poul Anderson

The eighty-six hour day of Ganymede drew to a close. Jupiter was at the half now, a banded amber giant in a sky of thronging wintry stars. Ray wiped his grimy hands and sighed.

"Done," he said, looking fondly at the haywired mess filling half the lab and reaching back toward the engines. "We've done it -- we've conquered the stars."