I don't think any of us are proposing building a reusable system for a
low flight rate. Even NASA wasn't proposing that with the Shuttle. It
just happened due to budget constraints. What we are proposing is not
doing Apollo again, which is what Shelby et al insist that NASA do.
On 2018-03-04 17:45, 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> 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:LEO:
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
flight rates are too low to justify the additional developmentcost.
wrote:
Bill
On Sun, Mar 4, 2018 at 3:17 PM Henry Vanderbilt
<hvanderbilt@xxxxxxxxxxxxxx <mailto:hvanderbilt@xxxxxxxxxxxxxx>>
come
Bill,
All I know is what survived that initial winnowing process to
across my desk as attempts at public explanation of whatConstellation
was trying to do.noticed. (I was
No sign of either reusables or horizontals that I ever
already quite attuned to reusability, of course, and it waswatching the
increasingly peculiar attempts to deal with consequences ofextreme
vertical lander stacking that started me thinking about thatpoint
also.)indicating
Now, if you can point me to publicly released documents
either of those was seriously considered for actualdevelopment as part
of the program, I will stand corrected.process.
Until then, I will assume they didn't survive your costing
institutional
Which brings us back to the original discussion of
assumptions leading to effectively pre-chosen winners andexcluding
potentially superior approaches, in Mars Ascent Vehicles andelsewhere.
different
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
depot and<mailto:hvanderbilt@xxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxthe
<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
studies thatsample
>> have been
>> performed on making an ascent vehicle for Mars
return...would
>> I was a bit surprised that they throught a hybrid
be the bestthe
>> choice, but that must have been strongly driven by
desirement tothey
>> be storable at low temperatures. I am surprised
found it to beno less.
>> the lightest option as well. A paraffin wax hybrid
skipped>
> The key question to ask is something that is often
overassumptions
even inassumptions used
> papers, never mind presentations: what were the
in the
> analysis? It's all too common to choose the
carefully sowinner. It's
> they stack the deck in favor of the pre-chosen
theinteresting
> that the two studies shown in this slide deck ranked
differentGuernsey
> approaches in quite different orders.business for a
>
> About twenty years ago, when LLNL was in the rocket
> little while, John Whitehead (LLNL) and Carl
(JPL) camevehicle
up with
> a rough design sketch of a biprop SSTO Mars ascent
that wastwice the
> lighter than any of these concepts and had about
pistonpayload. The
> key features were pump feed using LLNL's miniature
pumps, andand
> propellants stored in tanks aboard the mothership
loaded into thesince
> ascent-vehicle tanks only just before ascent -- thecombination
> permitted *very* lightweight ascent-vehicle tanks,
they didn'tfit into
> have to carry significant pressure loads orEarth-launch/Mars-landing
> loads. (Oh, and the design wasn't constrained to
a narrowbe.) W&G
> cylinder, as the ones in this latest study seem to
interestingmight have
> been too optimistic in spots, but it was an
approach andon
> looked promising.
This all reminds me of the strong LEMcentricity of NASA
potential newand I
Lunar landers.
Ten-ish years ago when Constellation was still a thing
was workingbasic
on a propulsion tech demo aimed at such landers, I wasexposed to a fair
amount of the customer's thinking on the matter.
All of the concepts were scaled-up versions of the
Apollo LEMground
configuration, a tail-lander with long legs to provide
clearancesee
for a big centrally-mounted engine. All.
There were amusing problems with the scale-ups. You'd
things likeleast one
thirty-foot vertical ladders for crew access, and in at
theinstance, a built-in crane (!) for lowering cargo from
apparentlyseveral-stories-up lander upper deck to the surface.
Side lander concepts, such as the Masten/ULA XEUS,
weren'trefusal to
even thinkable.
There also was (is still?) an accompanying utter
considersupport
reusable landers and the propellant depot system to
such - toousual
risky, too expensive. Likely so - if done by those
suspects under
business-as-usual.
Henry V
