The military is building a space plane. Now it looks to have an engine up to the task

A decade after the U.S. Air Force commissioned the next generation of GPS satellites, the first of these spacecraft is finally set to launch into orbit later this year.

As with other national security missions, a roughly 200-foot-tall rocket will blast the massive satellite to space, fulfilling a contract worth more than $80 million.

But as nations develop technology to disable or shoot down satellites - as China did to one of its own satellites with a ground-based ballistic missile in 2007 - the U.S. military has started to look at options for rapidly and cheaply launching smaller crafts into space.