McLean1382 wrote:

Dick Morris writes:

I was reading a paper in "The Case for Mars VI" last week which put it
at about 1/3 of the total estimated program cost. That's a non-trivial
cost item, but there are additional indirect effects. The high cost of
Earth-to-orbit transportation with expendable launchers leads to the
traditional obsession for minimizing the mass placed into orbit, which
drives development costs up across the board.

Depends on which iteration of the reference mission you look at. Another
version projects earth-to-orbit systems as 25% of the cost.

Even with LEO transit costs a couple of orders of magnitude less, you are still
going to have strong incentives to minimize mass. Getting from LEO to Mars and
back still requires a lot of delta v, even with aerobraking. And the need for
extreme reliability will drive up development costs in any case.

There will still be an incentive, though not to the extreme that NASA
carries it. An excessive focus on mass minimization drives up
development costs through endless trade studies to determine the
absolute best (miminum mass) concepts, extremely detailed analyses to
precisely characterize each part's operating environment amd
reliability, plus the agressive weight-reduction campaigns that seem to
be inevitable when a too-aggressive dry mass target has been selected
and the hardware ends up over-weight. That process also degrades
reliability by limiting redundancy and safety factors. Design the
entire mission with comfortable safety margins from the start and
development cost goes down while reliability goes up. (To obtain an
acceptable level of mission reliability it will still be necessary to
carry a significant quantity of spares for the higher-failure-rate
items.)

(Above all, we should never, never, EVER design a mission based on
technology advances that are ASSUMED will be available by the time
development is complete. If the technology advances do not materialize
on time, then virtually the entire development team will be sitting
around playing computer solitair or surfing the net while technology
catches up, or the program will require a very expensive redesign.
NEVER use an operational program as a device to "push the technology".
NASA has shot itself in the head doing exactly that for the last 30
years: Shuttle, ISS, NASP, SEI, X-33, SLI.)

The real barrier to the Mars Reference MIssion isn't so much the cost estimate,
but the reasonable fear of cost overruns, and the danger of these is probably
greatest on the TMI stage, TEI stage, landers, an ascent stage. We've built
HLVs, and have engines, tanks and strap-ons in production that are reasonably
well suited. The other vehicles are much more like estimating the cost of the
LM before it was built.

I would say that the cost estimates alone are quite sufficient as a
barrier, but if we design the ENTIRE mission with comfortable margins,
then the probability of cost overruns will be greatly reduced. That
will increase the IMLEO significantly, other factors being equal, but
that will not be a substantial cost item with low-cost Earth-to-orbit
transportation.

McLean