It doesn't if you're just redoing Apollo, at low flight rates. It does
if you're engaging in a serious program of lunar exploration and
exploitation. The problem with reuse of landers isn't development cost,
but that the cost of getting the propellant to the lunar surface moon
from earth, using conventional expendable vehicles (and particularly
SLS) exceeds the cost of the lander.
On 2018-03-04 14:52, 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> 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:depot and
Sorry, but time to call bullshit.
I was on the ESAS team and personally costed a dozen different
reusable lander concepts.wrote:
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>>
studies that
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
return...have been
performed on making an ascent vehicle for Mars sample
the bestI was a bit surprised that they throught a hybrid would be
desirement tochoice, but that must have been strongly driven by the
it to bebe storable at low temperatures. I am surprised they found
less.the lightest option as well. A paraffin wax hybrid no
over
The key question to ask is something that is often skipped
even inassumptions used
papers, never mind presentations: what were the
in thecarefully so
analysis? It's all too common to choose the assumptions
It'sthey stack the deck in favor of the pre-chosen winner.
interestingdifferent
that the two studies shown in this slide deck ranked the
business for aapproaches in quite different orders.
About twenty years ago, when LLNL was in the rocket
camelittle while, John Whitehead (LLNL) and Carl Guernsey (JPL)
up withthat was
a rough design sketch of a biprop SSTO Mars ascent vehicle
pumps, andlighter than any of these concepts and had about twice thepayload. The
key features were pump feed using LLNL's miniature piston
loaded into thepropellants stored in tanks aboard the mothership and
combinationascent-vehicle tanks only just before ascent -- the
they didn'tpermitted *very* lightweight ascent-vehicle tanks, since
Earth-launch/Mars-landinghave to carry significant pressure loads or
a narrowloads. (Oh, and the design wasn't constrained to fit into
W&Gcylinder, as the ones in this latest study seem to be.)
might haveapproach and
been too optimistic in spots, but it was an interesting
potential newlooked promising.
This all reminds me of the strong LEMcentricity of NASA on
Lunar landers.was working
Ten-ish years ago when Constellation was still a thing and I
on a propulsion tech demo aimed at such landers, I was exposedto a fair
amount of the customer's thinking on the matter.Apollo LEM
All of the concepts were scaled-up versions of the basic
configuration, a tail-lander with long legs to provide groundclearance
for a big centrally-mounted engine. All.things like
There were amusing problems with the scale-ups. You'd see
thirty-foot vertical ladders for crew access, and in at leastone
instance, a built-in crane (!) for lowering cargo from theweren't
several-stories-up lander upper deck to the surface.
Side lander concepts, such as the Masten/ULA XEUS, apparently
even thinkable.consider
There also was (is still?) an accompanying utter refusal to
reusable landers and the propellant depot system to supportsuch - too
risky, too expensive. Likely so - if done by those usualsuspects under
business-as-usual.
Henry V
