airplanes and space flight

Hi there,

One thing that I always wondered about space flight is why most
agencies (NASA, etc.) do not use a more efficient way of lifting into
space. The vertical rocket takeoff seems to use so much energy and does
not take advantage of the physics of regular flight. Why would one not
use something like a modified commercial airliner (make it airtight and
so forth) and then perform a regular take off and fly up to the
altitude where the air still supports the lift on the wings (using
plain old kerosene) and then once that barrier has been reached utilize
a rocket engine to make it the rest of the way. Should this not allow
for much greater payloads to be carried since less fuel is needed to
get up to 30,000 ft? Plus one could use established procedures such as
in-flight refuling at altitude to lessen the need for fuel at take off
even more.

Just imagine how much could be hauled into space and how much cheaper
it would be if one would modify a 747 and use the cargo capacity of
such a plane. I realize that this is a little simplistic in its
description (put a rocket motor on a 747 and have it lift off), but
nevertheless, why not take advantage of wing designs, etc. to get into
space.

I am sure that there is a very good reason why this has not been done
yet, since there are thousands of very smart people working on these
problems. I would just like to know what the negatives are to this idea
that would make it not feasible to implement. I can't imagine that it
would be cost, since they spend a boat load on the shuttle program as
it is.

Thanks for taking the time to answer this question.



Regards,
Mitch