Re: Why does a space shuttle have to carry all the fuel with it?

The orbital catapult idea is an idea that's been bounced around science 
fiction stories for many decades.  Other ground launched capabilities have 
been and have since continued to be explored.  I mentioned the orbital 
catapult...this name fits a broad group of possabilities from the simple 
mechanical catapult for "small" loads to the more advanced electro-magnetic  
rail launcher.  

The Space Shuttle was designed as a re-usable multiple 
mission/multiple payload configurable spacecraft, meaning that the 
original intent was to build a re-usable spacecraft which could perform any 
orbital mission ever required.  As a result the Shuttle needs external and 
internal fuel tanks for orbital insertion(maneuvering to the desired hight 
above the Earth) and if needed orbital maeuvers during mission payload 
deployment and for emergency use during the re-insertion and landing side 
of its mission.  The space shuttle was also original conceived to save 
money in the long term over an unrecoverable craft (rocket).

Today, the technology is just beginning to surface which may in the future 
lead to the development of unmanned/remote guided spacecraft.  Such 
spacecraft may also be launced by a ground-based launcher.  As it stands 
today, it is not economically feasible to build such a spacecraft.  Also, 
it is more feasible from a design point of view to carry your fuel and 
independent maneuvering ability with you onboard the craft.

However, in the future with an orbital colony or an orbital platform free 
of the burden of Earth's gravity, a "catapult" of some sort may be employed 
to launch freight into the Earth's orbit for pick-up via an 
intra-solar(within our own solar system) shuttle, or even catapulted to a 
new destination....in the future anything may be possible.