Mitch wrote:
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.


Not really.
The amount of fuel saved by starting out at 10Km is quite small.
And now, you've got wings, tail, landing gear, jets, ... to carry too.
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.

Because unfortunately when you do the numbers, it does not make sense.

There are arguments for launching stuff from modified aeroplanes, but
that's the only case that makes some sense.
At best, you need a dry mass of around 10%, in order to get into orbit,
with a single stage, and then you have little or no payload.

With todays technology, wings, jet engines/... are simply too heavy.