text: nasa decided to use a reusable vehicle, instead of single use vehicles, in the early seventies. the shuttle has three rocket engines in its tail and two solid rocket boosters attached to the outside.  the two boosters detach after use and are reusable.  nasa is going to again use single use vehicles.  it is going to be a set of two.\n\nlook here:\nhttp://www.nasa.gov/mission_pages/exploration/spacecraft/index.html