OK, great. Our primary disagreement is on how far off the future is. I'm
glad that you don't think that space transportation is somehow
magically, ultimately immune to fundamental economics. Because many in
this industry seem to, and are not unhappy about that. :-)
I just wish that the future had happened sooner. In the case of Apollo,
it happened too soon, which is how we got so screwed up.
On 2019-08-24 18:31, William Claybaugh wrote:
Rand:
We agree!
There is almost certainly some far distant future in which my current
focused economic analysis is made moot by technological progress.
But my my feet are not firmly planted on cloud nine and I try—as
best I am able—to deal with reality as it is: I am not given to
Science Fiction fantasies of the future.
Bill
On Sat, Aug 24, 2019 at 6:12 PM Rand Simberg <simberg@xxxxxxxxxxxxxxx>
wrote:
One does not need to do an "economic analysis" to know that bulk
deliveries of a commodity are cheaper than specialized ones, and
that
more stages improve transportation efficiency, particularly when
they
aren't thrown away. We will be delivering propellant to orbit that
is
not mission specific, and whether we put it in a Starship, or a
depot,
or a handbasket, doesn't really matter. The days of a single launch
sending a payload to a non-LEO destination, at least as the normal
way
of doing things, are coming to a close.
What will happen will happen, regardless of your economic analyses.
On 2019-08-24 16:46, William Claybaugh wrote:
Rand:to
They don’t need a depot because they designed their architecture
avoid it; that appears—to me—to have been a thought choice. Ia
previously reached similar conclusions in a proprietary study for
former employer.analysis
You’ve a gift for assertion; please, where is the economic
that proves your many claims correct?<simberg@xxxxxxxxxxxxxxx>
Bill
On Sat, Aug 24, 2019 at 5:30 PM Rand Simberg
wrote:else
Because they don't think they need one. That doesn't mean that
others
won't find it useful, or even that SpaceX wouldn't if someone
asdid
it.
We've needed to decouple LEO launch from other destinations for a
long
time, and until we do so, we won't drive down the overall costs
launchmuch
as possible with rockets. Having a place to leave propellant,
whether
excess flight reserve, or just some in the tank because the
onpayload was light, will decrease the cost of propellant on orbit
tothe
margin, and perhaps quite a bit. The effect of sending everything
in a
LEO, including propellant, and then departing from there with an
in-space transfer vehicle has the efficiency effect of adding
another
stage, that is fully reusable. It's how we would have done things
long
ago if we had wanted to build an affordable transportation
infrastructure, but we got sidetracked by Apollo and USAF
conservatism,
in which few could imagine not getting to the final destination
step
single launch. Boeing's electric GEO birds are just the first
onein a
process that is now underway.
On 2019-08-24 16:16, William Claybaugh wrote:
Rand:have
Then why is SpaceX not building a depot?
Is it remotely possible that they have done the same analysis I
done?<simberg@xxxxxxxxxxxxxxx>
Bill
On Sat, Aug 24, 2019 at 5:13 PM Rand Simberg
wrote:
The whole point is to replace the existing architecture with
thatthat is
much more scalable and cost effective. With the coming space
transports
from SpaceX and Blue Origin, and the new smallsat launchers,
foris
payload
happening in real time.
On 2019-08-24 14:29, William Claybaugh wrote:
Rand:plainly
I conclude that depots add cost to space flight because they
so do compared to the existing architecture. To date, no
thathas
failed to fly because the launcher couldn't carry it; arguing
depots solve a problem that does not exist is simply specious.
I am aware that SpaceX is planning to make use of refueling
toits
planned fully reusable architecture and that plan does appear
costslower
their required investment as compared to building a biggerrocket. I
do not understand that their cost would be further lowered bypaying
the cost of a depot; rather, it appears obvious that their
launchdepot.would
be higher by the amount required to build and operate that
<simberg@xxxxxxxxxxxxxxx>
Bill
On Sat, Aug 24, 2019 at 1:08 PM Rand Simberg
wrote:
We are on the verge of getting a fundamentally different
afraidyouarchitecture. Probably more than one. I don't understand why
think
that depots are costly.
On 2019-08-24 12:04, William Claybaugh wrote:
Henry:
I’ve reread this post more than a few times and I’m
notI
am
not able to make sense of it.ignore
If I understand your argument, it is at heart that we should
the 60 plus year existence proof that chemical rockets do
architecturesforneed
any
of the attributes you conjecture and instead plan in future
a
fundamentally different launch architecture.rational
Setting aside the improbability of selling this idea to any
investor or government, I don’t see the point:
samepro-ratathat
require refueling don’t require a depot or it’s costs.<hspencer@xxxxxxxxxxxxx>
Bill
On Fri, Aug 23, 2019 at 2:56 PM Henry Spencer
wrote:
On Fri, 23 Aug 2019, William Claybaugh wrote:
Propellant at a propellant depot costs the price of thatpropellant on the
ground plus the cost of launching it to LEO plus the
theamortization
of the cost of the depot plus the pro-rata depreciation of
ondepot plus
the cost of losses.
Propellant in an upper stage costs the price of propellant
the
ground
plus the cost of launching it to LEO.
True if:
1. The cost of launching an extra kilogram to LEO is the
extraeither
way.
2. There is extra room in the tanks for it.
3. The lower stage has the lift capability to carry its
importantspecialmass.
4. Reduced upper-stage launch mass doesn't confer some
advantage,
like seriously reduced structural mass, that's very
thelater.
Which is to say, if it's just a matter of whether to fill
assumptionstank a
advantagebit
more, that does indeed usually win. Depots et al show to
when
it's not that simple, when one (or more) of those
*are*is
not
true.
It's appealing to think (or at least claim) that things
survivedaboutthat
decouplesimple.
Trouble is, often they aren't.
For example, an important advantage of depots is that they
LEO
departure mass from launcher payload mass, so violations of
assumptions 2
and 3 don't threaten to sink your project. Should we worry
such
violations? Yes! They nearly sank Apollo -- which
discoveriesthanonly
because
Wernher von Braun had quietly built a rather bigger rocket
Constellation'sHouston's
spacecraft mass estimates would have required -- and
troubled history conspicuously included repeated
2that
the
rockets were undersized. Let's see, that's 2 out of NASA's
"facts".toprevious
attempts to reach the Moon that had big trouble with those
assumptions --
should we really believe that the current attempt is immune
players--whothis?
Depots are not getting any traction because the key
quietlyare at
OMB and the Space Council--know these facts.
Or because they are getting their briefings from folks who
aren't
discussing the dubious assumptions underlying these
Henry
