DARPA's Airborne Launch Assist Space Access (ALASA) has released a video showing how the takeoff process works. As you'll see in the animation below the fold, those rockets have to be light, because they're designed to be carried by unmodified jets into the air, before they're released to make their way into space.
Since the planes will serve as the "first stage," (hence, reusable) the government/military/companies with access to the technology will be able save money. In fact, each launch will only cost $1 million (a SpaceX launch costs around $55 million, but that's already cheap for a big rocket), and rockets can be deployed within 24 hours of being commissioned. But enough about the project's details: you should seriously watch the video below to see how a jet-small rocket combo can take a satellite to space.
