In article ,
says...
On 2018-12-30 19:46, Fred J. McCall wrote:
SpaceX has a pretty damned good idea of where the lower threshold is
for number of reuses before major refurbishment is required.
They do? What the maximum number of times a bloc, 5 has been re-used so
far ?
Yes, they do. Three. Note that they're still doing inspections and
some parts replacement between flights. They're not to the "gas and
go" type of operation.
Any commercial customers lined for for the 9th launch of a Falcon 9 yet?
I seriously doubt that the launch contracts are worded that way.
Customers want the earliest launch possible, so why would anyone specify
that they want to wait until the 9th launch of a first stage?
The
'equation' doesn't particularly change, since it's always been an
assumption that some launches will require expending the vehicle.
Say for sake of discussion that SPaceX can launc Falcon9 10 times.
When you have a "performance requirememt won't allow landing"
requirememnt, you use a Falcon 9 that has done 9 launches, and it is
ditched on its 10th launch. This way, you don't lose any potential
flight on that rocket.
You do know that after 10 flights they plan on refurbishing the booster
for even more flights, right?
With Block 5, SpaceX to increase launch cadence and lower prices
written by Michael Baylor May 17, 2018
https://www.nasaspaceflight.com/2018...crease-launch-
cadence-lower-prices/
From above:
Block 5 first stages are designed to fly up to ten times with
little to no refurbishment. In fact, with a scheduled maintenance
every ten flights, it will be possible to launch a Block 5 first
stage up to 100 times.
I'd expect SpaceX to want to expend the booster with the most flights,
not one with 9. But the customer might still want a "new" booster on an
expendable launch, so you charge the customer more money (so you can
manufacture a replacement booster) and carry on.
The other option would be to use a Falcon Heavy and recover both
boosters and the core stage. But again, that's going to be up to the
customer as well. Currently Falcon Heavy has only flown once. So a
customer like DOD might prefer a "single stick" Falcon 9 since it has a
far longer track record.
This is quite different from DoD requiring that SpaceX uses a brand
spanking new Falcon9 that is ditched with less than 1 flight (since
re-use factors in the multiple lighting of engines for launch AND landing).
You're conflating two different issues here. Expendable vs. reusable is
a different issue than new booster or flight proven booster. The former
is based on the delta-V and payload mass required for the launch and the
latter on DOD certifications (i.e. paperwork because they've never flown
on anything reused except for the space shuttle).
The two really are separate requirements, so your argument makes zero
sense to me.
If SpaceX uses its remaining production capability for Falcon9 to build
stages for DoD that are never re-used, that doesn't leave many Falcon9s
in stock that can be used and re-used for affordable commercial launches.
This is hand-waving bull****. Let's look at the *numbers*.
SpaceX launched 21 times in 2018 and one of those was a Falcon Heavy.
Quite a few of those were on new boosters. SpaceX still has a quick
production tempo. This really isn't an issue.
Here's a table:
https://www.reddit.com/r/spacex/wiki/cores
SpaceX currently has 11 cores classified by observers as "Flightworthy
Cores". These are all Block 5. Note one of these is "salty" and might
not fly again.
The one that landed in the water might, or might not, be re-flown. My
guess is that the engines are toast and it might not make sense to
refurbish it. But, they can at least salvage parts off it (like the
titanium grid fins). At any rate, Musk tweeted they plan on adding a
redundant hydraulic pump for the grid fins to prevent a landing failure
due to the pump failing.
So, out of *all* of the Block 5 cores produced so far, only a single
core has been completely lost (B1054 on the GPS III mission). SpaceX
currently has 10 known good cores in its inventory, and they're still
producing more.
If DoD allows the use of used Falcon9s, then SpaceX can do a number of
commercial launches on a stage and then finish that stage's life with
non re-usable DoD launch, and that makes a huge financial difference for
SpaceX which needs to build far fewer stages to get the same job done.
Again, they'd have to do this on the "99th" flight of a core, not the
9th, so this argument makes no sense because DOD will have certified
flight proven Falcon 9 stages for DOD launches. They're in the process
of doing this, but it's clearly not as high of a priority compared to,
you know, actually launching DOD satellites on new boosters since SpaceX
is still building new boosters.
I really don't understand all of your hand-wringing here. It makes no
sense.
You're obviously too thick to understand WHY a vehicle would be
expended on a launch.
In this particular case, because a lawsuit was involved for SpaceX to
get this launch, all bets are off on the real reasons for it. As Mr
Findley pointed, contract was signed at a time SpaceX was trying but had
not yet demonstrated re-use. Also, should it succeed (which it did), the
Dod would have had to setup procedures in the contract to ensure it can
"clean" the landed stage of any possible military secrets inside. So
requiring it be ditched in ocean would be much simpler and risk free.
Expending the booster was due to the delta-V requirement and the
relatively high mass of the GPS III satellite. Again, this is
*completely* separate from the "new booster" requirement.
Remember also that if contract was signed prior to Block5 being in
production, it also means that the increased capacity/thrust it brought
would not have been required to launch that satellite, so using Block5
may have brough enough spare capacity to allow a landing. But since
contract stipulated no landing, SpaceX complied.
Remember also that if contract was signed prior to Block5 being in
production, it also means that the increased capacity/thrust it brought
would not have been required to launch that satellite, so using Block5
may have brough enough spare capacity to allow a landing. But since
contract stipulated no landing, SpaceX complied.
IT could very well be a true performance limitation. But I am not 100%
sure of it
Consider this: if Musk planned Falcon9 to be reusable 10 to 100 times,
but most of the launches are to be capacity limited and require
ditching, there wouldn't be much re-use done and that would change the
financials of that project a LOT. So I really suspect that commercial
launches to geosync will allow landing and re-use. Launching to half of
that should have allowed it even more (unless GPS satellite was very
very heavy).
The delta-V margin was *very* "tight" on this mission if SpaceX had
attempted recovery. Again, DOD didn't want to take any chances on
something deemed critical for war-fighters.
In the future, I wouldn't be surprised to see a GPS III (in a similar
orbit) launching on a Falcon Heavy with both boosters and the core
recovered. But we'll see.
IT could very well be a true performance limitation. But I am not 100%
sure of it
Yes, it was a "true performance limitation" because there would have
been very little margin for error. DOD didn't like that. So, no
recovery.
Consider this: if Musk planned Falcon9 to be reusable 10 to 100 times,
but most of the launches are to be capacity limited and require
ditching, there wouldn't be much re-use done and that would change the
financials of that project a LOT. So I really suspect that commercial
launches to geosync will allow landing and re-use. Launching to half of
that should have allowed it even more (unless GPS satellite was very
very heavy).
You "suspect" wrong. You can't do this "in your gut", you have to *do
the math*.
We've told you repeatedly that it's the *inclination*, orbital altitudes
(apogee and perigee), and the mass of the GPS III satellite *combined*
that caused Falcon 9 to have very little margin for recovery on this
mission. You keep ignoring the *inclination*. You CAN'T DO THAT!
Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.