[AR] Re: Mars Ascent Vehicle studies
- From: William Claybaugh <wclaybaugh2@xxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Mon, 05 Mar 2018 21:54:12 +0000
Henry:
I’ve spent rather some time now looking at previous studies and visiting w/
a former colleague who is—in my view—the next best space architect in the
US after Mike Griffin to discuss and think about your post; please see
below:
On Sun, Mar 4, 2018 at 5:24 PM Henry Spencer <hspencer@xxxxxxxxxxxxx> wrote:
On Sun, 4 Mar 2018, William Claybaugh wrote:
Take five minutes and you should figure out that reuse on the moon
doesn't make sense for the same reason it doesn't make sense for LEO:
flight rates are too low to justify the additional development cost.
If your vision of activity on the Moon is repeating Apollo -- a few short
visits followed by program cancellation -- that's undoubtedly true. And
of course, this is a self-fulfilling prophecy, because if you build your
hardware around that impoverished vision, that's all it will be good for.
Henry, this is just rant; nobody intentionally builds an “improvised
vision”. Please stop; you are a better person than this sort of
“argument”. That your replies to my posts are increasingly of this
character concerns me.
On the other hand, if your vision is "sustained human presence on the
Moon", you might decide that this requires planning your hardware to
support higher flight rates before too very long, even if it therefore is
suboptimal for a brief initial period of limited activity. This would
require a rather different approach to the problem.
Yes, absolutely. But: *you* seem here to have freed yourself from budget.
That is not possible; policy makers deal with reality as it is, that means
budgets. Above all that means budgets.
Nor is the “suboptimal” period brief by any calculation of which I am
aware: Griffin and I had a fair debate during ESAS (to, I think, the
considerable shock of more than a few career folk) over whether what is now
SLS was embedding ELV costs for decades to come. Mike—correctly—argued
that when costs dropped sufficiently, government would have no choice but
to reengineer the Earth-moon architecture to take advantage of those new
lower costs. He challenged me to analyze the trade between spending the
money then (2006) to build a the fully reusable Earth-moon transportation
system per our 1994 paper against the—at that moment—ESAS baseline
architecture.
Keeping spending w/i the then projected NASA budgets, the fully reusable
Earth-moon transportation system of the 1994 BIS paper was cheaper than the
then ESAS architecture after 84 years. In those days, the USG discount rate
was 7% which implies that the break even investment horizon for the USG—at
that time—was about 45 years, generously. In short, the at that moment
ESAS architecture cost less for almost a century. We also didn’t get to the
moon before 2050...an obvious political non-starter.
This is how OMB makes budget decisions: if you want to force your vision of
the future on today, you have to prove it is cheaper. If—as I have
consistently found—it is not cheaper, then you have to wait. Productivity
will eventually catch up.
Bill
I note that the latter is what NASA was explicitly directed to do by the
NASA Authorization Act of 2005 (US law 190-155, 30 Dec 2005) -- the quoted
phrase is verbatim. If you seek an example of letting institutional
assumptions override rational planning, consider the transformation of
that phrase into a program whose highest goal was to repeat Apollo.
Reuse on the Moon, like reuse for LEO, is justifiable only if your goals
reach well beyond the first dozen flights.
I have personally costed many dozens—approaching a hundred—at least
partially reusable lunar architectures. The 1994 BIS paper that you so
dislike presents the best results I have to date found: a fully reusable
Earth-moon transportation system that gets down to about $5000 per pound
round trip. So far as I know that is the only publicly costed fully
reusable Earth-moon transportation system. Never mind the couple of hundred
Billion dollars that architecture would cost to develop.
Henry
Other related posts:
