Whatever NASA comes up with to replace the present shuttle will cost $10-15B
(current dollars) for development (the development cost for the present
orbiter was $13B in current dollars) and will have an annual operating cost
pretty much the same as it is now (about $4B per year for 6 - 8 flights). I
posted a detailed cost estimate for a typical OSP/Delta IV configuration in
this newsgroup in the thread entitled

shuttle cost versus other launch options

dated 16 April 2003 to back up what I say about operating cost of a shuttle
successor.

Why are these costs the same? Because the technology that will be used for
the shuttle replacement will be the same as that used for the original
shuttle, namely, Apollo heritage technology. Since those ancient days when I
worked on the original shuttle Phases A and B efforts in 1969-72, there have
been no magic materials, no wonderful propulsion advances, no super-duper
manufacturing processes developed that will change the basic economics of
manned reusable launch vehicles/spacecraft. The newest U.S. engine,
Rocketdyne's RS-68 used on the Delta IV CBC, is a scaled-up and slightly
modified version of the excellent J-2S engine that was developed in the late
1960s for the Apollo Applications Program (AAP) that was supposed to carry
on after the moon landings were over (AAP became Skylab). In 1995-96 I
worked on development of carbon/silicon carbide (C/SiC) materials for the
X-33 technology support effort. C/SiC is supposed to have superior strength
and oxidation resistance compared to the infamous RCC material so much in
the news because of the Columbia disaster. But the jury is still out on
C/SiC as a replacement for RCC, since it has problems of its own, not the
least of which is relatively low manufacturing yield.

We knew as far back as the shuttle Phase I effort in 1969 that the
development cost of a manned reusable spacecraft like the orbiter does not
scale very strongly with size (i.e. with payload bay dimensions, which
determine the size of the aluminum airframe). The airframe is relatively
inexpensive. It's the complex systems (RCS, propulsion, avionics,
hydraulics, APU, environmental control, prime power, etc.) that drive the
development cost of a reusable spacecraft, and these systems are essentially
the same design whether the reusable spacecraft is large like the present
orbiter or small like the proposed winged versions of the OSP. Nobody has
come up with alternate designs for these complex, expensive systems used on
present orbiter that will reduce the development cost of the shuttle
replacement significantly.

Later
Ray Schmitt





"Hallerb" wrote in message
...

To replace the shuttles. Theres just too many jobs dependent on the
program.
Whatever replaces it cant be as costly and costly equals jobs.

So I think the shuttle will end because of accidents probably running out
of
orbiters. I hope at least one survives for a museum exhibit.