Henry:
You—and others—seem to be ignoring the key lesson of Shuttle: reuse costs
*more* unless the flight rates are very high.
Just building a reusable asset and operating it at low flight rates will be
more expensive than expending. “Build it and they will come” is not a sound
strategy wrt nation-state funding.
If you have some other funds source, have at it.
Bill
On Sun, Mar 4, 2018 at 6:28 PM Henry Vanderbilt <hvanderbilt@xxxxxxxxxxxxxx>
wrote:
And flight rates will remain too low until flight costs come down
drastically. Which will only happen with sensibly-planned reusability -
throughout the transportation process.
A classic chicken-and-egg problem.
But sometimes if you want a growing affordable egg supply, you just have
to ditch that cheaper-in-any-given-week-to-get-a-dozen-at-the-store
calculation and go buy some chickens.
And if your employer is on a fixed budget, while their corporate culture
makes it unthinkable that the analysis be based on anything but buying
fully NASA human-rated FARS-compliant chickens at ten thousand dollars
each, well, yes, the analysis will show building chicken coops to be
utterly impractical.
Which brings us back to the original discussion of institutional
assumptions excluding potentially superior approaches.
Henry
On 3/4/2018 3:52 PM, William Claybaugh wrote:
Henry:Constellation
Take five minutes and you should figure out that reuse on the moon
doesn’make sense for the same reason it doesn’t make sense for LEO:
flight rates are too low to justify the additional development cost.
Bill
On Sun, Mar 4, 2018 at 3:17 PM Henry Vanderbilt
<hvanderbilt@xxxxxxxxxxxxxx <mailto:hvanderbilt@xxxxxxxxxxxxxx>> wrote:
Bill,
All I know is what survived that initial winnowing process to come
across my desk as attempts at public explanation of what
was trying to do.was
No sign of either reusables or horizontals that I ever noticed. (I
already quite attuned to reusability, of course, and it was watchingthe
increasingly peculiar attempts to deal with consequences of extremepart
vertical lander stacking that started me thinking about that point
also.)
Now, if you can point me to publicly released documents indicating
either of those was seriously considered for actual development as
of the program, I will stand corrected.elsewhere.
Until then, I will assume they didn't survive your costing process.
Which brings us back to the original discussion of institutional
assumptions leading to effectively pre-chosen winners and excluding
potentially superior approaches, in Mars Ascent Vehicles and
less.
The view through your particular knothole may vary, of course.
Henry
On 3/4/2018 2:00 PM, William Claybaugh wrote:
> Henry:
>
> Sorry, but time to call bullshit.
>
> I was on the ESAS team and personally costed a dozen different
depot and
> reusable lander concepts.
>
> The view through your knothole might be biased....
>
> Bill
>
> On Sun, Mar 4, 2018 at 1:51 PM Henry Vanderbilt
> <hvanderbilt@xxxxxxxxxxxxxx <mailto:hvanderbilt@xxxxxxxxxxxxxx>
<mailto:hvanderbilt@xxxxxxxxxxxxxx
<mailto:hvanderbilt@xxxxxxxxxxxxxx>>> wrote:
>
> On 3/3/2018 8:37 PM, Henry Spencer wrote:
> > On Sat, 3 Mar 2018, Lars Osborne wrote:
> >> The discussion about LITVC reminded me of some of the
studies that
> >> have been
> >> performed on making an ascent vehicle for Mars sample
return...
> >> I was a bit surprised that they throught a hybrid would
be the best
> >> choice, but that must have been strongly driven by the
desirement to
> >> be storable at low temperatures. I am surprised they
found it to be
> >> the lightest option as well. A paraffin wax hybrid no
> >It's
> > The key question to ask is something that is often skipped
over
> even in
> > papers, never mind presentations: what were the
assumptions used
> in the
> > analysis? It's all too common to choose the assumptions
carefully so
> > they stack the deck in favor of the pre-chosen winner.
> interestingW&G
> > that the two studies shown in this slide deck ranked the
different
> > approaches in quite different orders.
> >
> > About twenty years ago, when LLNL was in the rocket
business for a
> > little while, John Whitehead (LLNL) and Carl Guernsey
(JPL) came
> up with
> > a rough design sketch of a biprop SSTO Mars ascent vehicle
that was
> > lighter than any of these concepts and had about twice the
> payload. The
> > key features were pump feed using LLNL's miniature piston
pumps, and
> > propellants stored in tanks aboard the mothership and
loaded into the
> > ascent-vehicle tanks only just before ascent -- the
combination
> > permitted *very* lightweight ascent-vehicle tanks, since
they didn't
> > have to carry significant pressure loads or
Earth-launch/Mars-landing
> > loads. (Oh, and the design wasn't constrained to fit into
a narrow
> > cylinder, as the ones in this latest study seem to be.)
> might haveone
> > been too optimistic in spots, but it was an interesting
approach and
> > looked promising.
>
> This all reminds me of the strong LEMcentricity of NASA on
potential new
> Lunar landers.
>
> Ten-ish years ago when Constellation was still a thing and I
was working
> on a propulsion tech demo aimed at such landers, I was
exposed to a fair
> amount of the customer's thinking on the matter.
>
> All of the concepts were scaled-up versions of the basic
Apollo LEM
> configuration, a tail-lander with long legs to provide ground
clearance
> for a big centrally-mounted engine. All.
>
> There were amusing problems with the scale-ups. You'd see
things like
> thirty-foot vertical ladders for crew access, and in at least
> instance, a built-in crane (!) for lowering cargo from the
> several-stories-up lander upper deck to the surface.
>
> Side lander concepts, such as the Masten/ULA XEUS, apparently
weren't
> even thinkable.
>
> There also was (is still?) an accompanying utter refusal to
consider
> reusable landers and the propellant depot system to support
such - too
> risky, too expensive. Likely so - if done by those usual
suspects under
> business-as-usual.
>
> Henry V
>
>
>
