Story identification: space travel limited after depletion of a resource

Question

I'm trying to find a novel or short story I read at least 10 years ago. The back story being, as I recall, humanity scavenges alien technology floating in space which was reverse engineered to create some form of FTL travel. Humanity spreads across the universe, exploring new systems and colonizing new worlds. However, humanity does not fully understand the scavenged technology.

Eventually, the resource required to power the FTL device runs out and the various colonized systems are isolated from each other. Some colonies are close enough to maintain relations via sub-light travel.

The story follows a character aboard a ship who somehow encounters technology which was under development prior to the demise of the scavenged FTL device. The technology in question is an engine capable of FTL travel, possibly called a Slow Drive, which was largely dismissed in the past because it was slower than the scavenged FTL device. That said, the Slow Drive would be a massive improvement upon the sub-light engines of the story's current setting.

Answer 1

This sounds very much like Godspeed by Charles Sheffield.

It includes the Slowdrive you mentioned (The other, faster FTL drive is named "Godspeed")

The other plot point the you might recognize is the legend of the "two-half-man": Brothers, where one lost his arms and the other his legs so they worked together as a team.

Jay Hara is an ordinary young man growing up on the isolated planet of Erin. But Jay dreams of adventure and escapades and the legend of the lost "Godspeed" drive which allowed humans to travel at faster-than-light speeds. His life changes when he joins up with the seedy spacer, Paddy Enderton and Captain Daniel Shaker. Captain Shaker is a charming but ruthless adventurer who inspires both fear and admiration in equal measure, and he and his questionable crew are joined by Jay as they race to find the legendary drive Jay Hara used to dream about.

Godspeed is a true coming-of-age tale told in the classic tradition of R.L. Stevenson's Treasure Island. A modern day pirate story, set among the stars.