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>
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:that
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>> 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
>> have beenbest
>> performed on making an ascent vehicle for Mars sample return...
>> I was a bit surprised that they throught a hybrid would be the
>> choice, but that must have been strongly driven by thedesirement to
>> be storable at low temperatures. I am surprised they found it tobe
>> the lightest option as well. A paraffin wax hybrid no less.carefully so
>
> 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
> they stack the deck in favor of the pre-chosen winner. It'swas
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
> lighter than any of these concepts and had about twice theand
payload. The
> key features were pump feed using LLNL's miniature piston pumps,
> propellants stored in tanks aboard the mothership and loaded intothe
> ascent-vehicle tanks only just before ascent -- the combinationdidn't
> permitted *very* lightweight ascent-vehicle tanks, since they
> have to carry significant pressure loads orEarth-launch/Mars-landing
> loads. (Oh, and the design wasn't constrained to fit into anarrow
> cylinder, as the ones in this latest study seem to be.) W&Gand
might have
> been too optimistic in spots, but it was an interesting approach
> looked promising.new
This all reminds me of the strong LEMcentricity of NASA on potential
Lunar landers.working
Ten-ish years ago when Constellation was still a thing and I was
on a propulsion tech demo aimed at such landers, I was exposed to afair
amount of the customer's thinking on the matter.clearance
All of the concepts were scaled-up versions of the basic Apollo LEM
configuration, a tail-lander with long legs to provide ground
for a big centrally-mounted engine. All.like
There were amusing problems with the scale-ups. You'd see things
thirty-foot vertical ladders for crew access, and in at least onetoo
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 -
risky, too expensive. Likely so - if done by those usual suspectsunder
business-as-usual.
Henry V
