Agree with you, my friend - depots don't make economic sense until we have
high volume transportation - which does not yet exist.
But high volume transportation is in our national interest for the things
we will need to do in cislunar space - and defended depots will facilitate
that.
So, in my view, we should intentionally build towards a high volume
transportation future - both to increase our GDP and to provide security
for our $trilllions in investment out there (a robotic deterrent platform
on the back side of the Moon, for example, should not have to land in order
to refuel).
Of course, once we have high Isp, high thrust NTR or fission fragment or
NSWR or whatever, the need for large, vulnerable chemical depots goes away
;)
Godspeed,
Bill
On Sat, Aug 24, 2019 at 6:19 PM William Claybaugh <wclaybaugh2@xxxxxxxxx>
wrote:
Bill:
Of all people, you particularly have no reason to open even a public email
to me with a caution about being “respectful”. You earned my respect long
ago and it has never diminished.
But allow me to point out the fallacy in your argument: the “fuel depots”
that we almost all use for our personal transport are the economic effect
of *hundreds of millions* of vehicles needing fuel.
In LEO—for more than 60 years—there have been zero point zero vehicles
needing refueling.
I grant you that if we are still stuck w/ chemical rockets when hundreds
of millions of vehicles require refueling in LEO every week, then a gas
station might well be the efficient economic solution. That is not the
world in which you and I live.
Analogical thinking is seductive but generally worthless in my view unless
the previous analog is exactly comparable to the present problem; that is
simply not the case here.
A single “gas station” servicing far less than one thousand customers per
year simply cannot make economic sense; the costs are calculably far higher
than alternative—and existing—options.
Bill
On Sat, Aug 24, 2019 at 6:18 PM Bill Bruner <bill@xxxxxxxxxx> wrote:
Bill - respectfully - Chevron is building a "propellant depot" near my
office. As with the LEO depot, the cost of the propellant will be the cost
of transporting it there in a specialized tanker, plus the amortization
cost of the depot.
The local depot operator is able to sell propellant to me at the cost of
transport plus the amortization cost of the depot plus a profit (and
obscene California and Federal fuel taxes).
So everyone makes money - the propellant extraction company, the refiner,
the tanker transportation company, the depot operator and the blood sucking
state and federal governments :)
I choose to refuel there on the way to work, because I don't want to
invest in a larger vehicle with more propellant capacity. All I want to do
is get to work and come home - so I win, and everyone else in the value
chain wins too.
I submit that this sort of architecture is not only eminently possible in
LEO and LLO - I further submit that it is absolutely necessary in order to
build the robust and flexible cislunar transportation architecture we need
to secure the Earth Moon system for free people.
Yes, it will require investment in specialized vehicles and depot
infrastructure, but so did the railroad, air navigation and interstate
highway systems that built this country.
Your friend,
Bill
Bill Bruner, Col., USAF (ret.)
New Frontier Aerospace
bill@xxxxxxxxxx
925-456-4553
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On Sat, Aug 24, 2019 at 4:47 PM William Claybaugh <wclaybaugh2@xxxxxxxxx>
wrote:
Rand:
They don’t need a depot because they designed their architecture to
avoid it; that appears—to me—to have been a thought choice. I previously
reached similar conclusions in a proprietary study for a former employer.
You’ve a gift for assertion; please, where is the economic analysis that
proves your many claims correct?
Bill
On Sat, Aug 24, 2019 at 5:30 PM Rand Simberg <simberg@xxxxxxxxxxxxxxx>
wrote:
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 else did
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 as much
as possible with rockets. Having a place to leave propellant, whether
excess flight reserve, or just some in the tank because the launch
payload was light, will decrease the cost of propellant on orbit on the
margin, and perhaps quite a bit. The effect of sending everything to
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 in a
single launch. Boeing's electric GEO birds are just the first step in a
process that is now underway.
On 2019-08-24 16:16, William Claybaugh wrote:
Rand:
Then why is SpaceX not building a depot?
Is it remotely possible that they have done the same analysis I have
done?
Bill
On Sat, Aug 24, 2019 at 5:13 PM Rand Simberg <simberg@xxxxxxxxxxxxxxx
wrote:
The whole point is to replace the existing architecture with one
that is
much more scalable and cost effective. With the coming space
transports
from SpaceX and Blue Origin, and the new smallsat launchers, that is
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 payloadhas
failed to fly because the launcher couldn't carry it; arguing thatits
depots solve a problem that does not exist is simply specious.
I am aware that SpaceX is planning to make use of refueling for
planned fully reusable architecture and that plan does appear tolower
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 costswould
be higher by the amount required to build and operate that depot.<simberg@xxxxxxxxxxxxxxx>
Bill
On Sat, Aug 24, 2019 at 1:08 PM Rand Simberg
wrote:need
We are on the verge of getting a fundamentally different launch
architecture. Probably more than one. I don't understand why you
think
that depots are costly.
On 2019-08-24 12:04, William Claybaugh wrote:
Henry:am
I’ve reread this post more than a few times and I’m afraid I
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 not
aany
of the attributes you conjecture and instead plan in future for
isfundamentally different launch architecture.rational
Setting aside the improbability of selling this idea to any
investor or government, I don’t see the point: architecturesthat
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:the
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 pro-rataamortization
of the cost of the depot plus the pro-rata depreciation of thedepot plus
the cost of losses.
Propellant in an upper stage costs the price of propellant on
eitherground
plus the cost of launching it to LEO.
True if:
1. The cost of launching an extra kilogram to LEO is the same
mass.way.
2. There is extra room in the tanks for it.
3. The lower stage has the lift capability to carry its extra
tank a4. Reduced upper-stage launch mass doesn't confer some special
advantage,
like seriously reduced structural mass, that's very important
later.
Which is to say, if it's just a matter of whether to fill the
advantagebit
more, that does indeed usually win. Depots et al show to
when
it's not that simple, when one (or more) of those assumptions
aboutnot
thattrue.
It's appealing to think (or at least claim) that things *are*
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
onlysuch
violations? Yes! They nearly sank Apollo -- which survived
thatConstellation'sbecause
Wernher von Braun had quietly built a rather bigger rocket than
Houston's
spacecraft mass estimates would have required -- and
troubled history conspicuously included repeated discoveries
players--whothis?the
rockets were undersized. Let's see, that's 2 out of NASA's 2
previous
attempts to reach the Moon that had big trouble with those
assumptions --
should we really believe that the current attempt is immune to
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 "facts".
Henry
