...Military Space Plane (X-37b) to Launch February 26

On Dec 16, 9:42*am, " wrote:

in typical *nasa fashion they abandoned the successful model which
could of been duplicated easily on a production line basis, and many
more sent to explore.

You aren't understanding the way this works. If we were seriously
going to be exploring to prepare for a landing that is surely what we
would do. (In fact, that's what we did do for the moon in the 1960's
with the Ranger, Surveyor, and Lunar Orbiter programs, each of which
had several coordinated missions). But this isn't about exploring
different spots to see where the best and most interesting places to
land and explore further with humans would be (any such work would be
in the future, once Congress actually starts seriously funding the
Constellation program). This is about answering as many different
questions as possible on a given budget. Spirit and Opportunity
answered the big top-line questions that they were supposed to: was
there ever liquid water on Mars? (Answered affirmatively by the two
rovers.) With more rovers, you could get more detailed and better
answers to that particular question, or you could send a different set
of instruments on a different platform (to support these different
sensors) and try to answer a different top-line question (like looking
for actual evidence of life, say). And all of the people who are
working on questions other than evidence of water in the Martian past
want a chance to get their questions answered. So instead of building
more rovers to better explore that question we get new craft designed
to give a general answer to other questions- say about Titan, or
Europa, or the Martian atmosphere.

The rovers don't really work well as a general purpose bus. Spirit and
Opportunity would be poor platforms for looking for life, as an
example. In order to do that properly you need to sterilize the craft
before launching (so you can be sure you aren't finding earth microbes
that have hitched a ride), and the rovers were not designed for that-
and you really need to design the electronics to survive being baked
like that, or you just built a very expensive brick. In addition, the
air bag system would probably be dropped for future missions- it
turned out to be far more complicated than expected (in particular,
they tried to avoid the need for a steerable braking rocket system
with the airbags, but the mass of the rovers meant that they had to
have such a system anyway- if you have to have a steerable braking
rocket you might as well soft land). So it was pretty much inevitable
that the next generation of rover would not be like Spirit and
Opportunity.

People have looked at using a common bus design to support multiple
missions with different sensors to answer different questions, but it
turns out to not be a great solution. Look at the history of the
Planetary Observer program for reasons why. Or Netlander, which didn't
even get that far.

Chris Manteuffel