Heechee Rendezvous

After millennia had passed, Mankind discovered the Heechee legacy (an alien culture that fled to the reative safety of a black hole)—in particular an asteroid stocked with autonavigating spacecraft. Robinette Broadhead, who had led the expedition that unlocked the many secrets of Heechee technology, is now forced once more to make a perilous voyage into space—where the Heechee are waiting. And this time the future of Man is at stake....