The Sky Road — Ken MacLeod

Centuries after its catastrophic Deliverance, humanity is again reaching into space. And Clovis, a young scholar working in the spaceship= construction yard, could make the difference between success and failure. For his mysterious new lover, Merrial, has seduced him into the idea of extrapolating the ship's future from the dark archives of the past.

A past in which, centuries before, Myra Godwin faced the end of a different space age--her rockets redundant, her people rebellious, and her borders defenseless against the Sino-Soviet Union. As Myra appealed to the crumbling West for help, she found history turning on her own strange past--and on the terrible decisions she faces now.

Decisions which, centuries later, will determine the direction of the new space age. Merrial's people, the mysterious "tinkers," know this. And, they know that the truth lies in the secret files left by Myra Godwin.