They were solid fuel rockets, but like none ever used before.

Suddenly the engines, fed by auxiliary fuel rockets, roared into life.

"I'll have the base send up a fuel rocket."

But solid fuel rockets simply can't be made to burn with absolute evenness as a team.

"A solid fuel rocket can start off at ten gravities acceleration," he said slowly.

Assuming they're solid fuel rockets, they are on a collision course with us.

The remnants of the solid fuel rockets let go.

And there were racks to which solid fuel rockets of various sizes could be attached.

Joe cracked the control of his forward liquid fuel rockets.

Nobody was going to get out to the planets right away; the space program would limp along on liquid fuel rockets.