On Mon, 13 Sep 2010 19:07:16 -0400, JF Mezei
wrote:

At the end of the day, aren't all options for space travel
"too expensive"

What NASA should have done in the mid 1990s is to get funding to build a
new and improved shuttle. An evolution.

Instead, it has tried many times for the "revolution" with totally new
designs and each time, those projects were cancelled because of cost
overruns and uncertaintly in the project's success.

They did have various "evolutionary" Shuttle Mk.II proposals, starting
in 1985 and really gaining steam after Challenger. Shuttle II studies
(most of which looked like a Shuttle External Tank with wings and a
bulbous payload bay) kept going for quite a while, as a fallback /
partner to X-30, and seems to have died around the time of the Space
Exploration Initiative fiasco, along with ALS/NLS.

NASA should have had funding to build one new orbiter every 5-8 years
with more improvements as it retires the oldest remaining one. This
would hace reduced costs over time as improvements were made.

Rockwell offered two updated Orbiters after Challenger. NASA said no,
because the new-builds (OV-2xx)) would not be compatible with the
Columbia-class Orbiters (OV-1xx) and operations cost would have gone
through the roof. Boeing made the same offer after Columbia, but by
then anything with wings was considered eeeeeevvvvviiiiiilllll.

The cost of building a new and improved orbiter would have been offset
by the savings of not having to do the heavy maintenance on the oldest
orbiter being replaced.

But the added costs of now having to maintain two different families
of space vehicles was prohibitive, especially along side the added
costs of designing, qualifying, and building the updated model. The
budget for it was never there, especially in the Space Station
design/development era. Even the relatively cheap ASRM was
unaffordable.

This applies also to the Orbiter Update program, with things like
Liquid Flyback Booster (RFS) all-electric APU, and non-toxic OMS/RCS,
all of which were in development for implementation on the current
fleet between the collapse of X-33 circa 2000 and the loss of Columbia
in 2003.

Yes, there would have been incompatibilities, but in the long term,
costs woudl have gone down. NASA was able to live with part of its fleet
having upgraded glass cockpits,

They had no choice: they couldn't get spare parts for the original
anymore, and they had to operate both a lot longer than planned
because of Station and Shuttle delays (Endeavour didn't get its glass
cockpit until after Columbia was lost.)

and part having the ODS/airlock while
one was left with the airlock in the crew compartment.

Same airlock. Just outside instead of inside. Not a huge problem.

NASA was able to upgrade SSMEs and apply the upgraded engines to the
fleet progessively.

But they didn't co-exist for long... a couple of flights of a new
turbopump, and then fleetwide replacement. Then a couple of flights of
the other turbopump, and ditto. It would have been years before the
last of the Columbia-class was replaced.

So it seems that NASA was quite able to live with disparate fleet of
orbiters.

Not nearly to the degree an updated Orbiter would have inflicted.

Brian