Ah, Shuttle. Which again circles us back to the original discussion of
institutional imperatives excluding potentially superior approaches.
I differ on the key lesson of Shuttle. It's more like, if you want to
win a horse race, don't have a government committee design your horse.
YMM, of course, V.
Henry
On 3/4/2018 6:45 PM, William Claybaugh wrote:
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 <mailto: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:
>
> 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>
<mailto: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
Constellation
> was trying to do.
>
> No sign of either reusables or horizontals that I ever
noticed. (I was
> already quite attuned to reusability, of course, and it was
watching the
> increasingly peculiar attempts to deal with consequences of
extreme
> 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 part
> of the program, I will stand corrected.
>
> 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
elsewhere.
>
> 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>>
> <mailto: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 less.
> > >
> > > 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. It's
> > interesting
> > > 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.) W&G
> > might have
> > > 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 one
> > 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
> >
> >
> >
>
