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Old January 3rd 19, 10:50 PM posted to sci.space.policy
Greg \(Strider\) Moore
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Default Falcon 9 Delivers Dragon Into Orbit, Flubs Landing

"JF Mezei" wrote in message ...

On 2019-01-02 07:05, Jeff Findley wrote:

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.


So they have now officially downgraded their original plans of between
10 and 100 launches down to 3?


Wow... that's an amazing jump in logic. Now, they've simply only flown a
block 5 3 times because, they haven't had that many flights yet since
they've introduced a block 5.


If they have only 3 in their experience so far, but still plan for much
higher number, my statement still standsL they doN,t yet have the
enxperience to know how many launches a stage can really do.


No, JF, you don't have the experience to know, but they have a pretty good
idea. I'd say this isn't rocket science, but it is. Sort of. It's mostly
materials science and the stresses and loads are pretty well known by now.


Saw a presentation by Mrs Shotwell on Youtube today. Basically, Musk
sets lofty goals and motivates employees to reach for the sky, but then
she and the engineers get to actually work out what goals can be
achieved and get the job done.

Aspirational goals set by Musk aren't necessarily what gets implemented
in the end.


Correct. BUT, 10 is NOT a huge leap. In many ways it's a smaller leap from
3-10 than it is from 1-2.
3-10, you already know the rocket can fly and be re-used. You've proven it.
1-2, you've only proven it can fly, not be reused.


So just because Musk said 100 flights doesn't mean this is the actual
limit they will set. And if the max is 3 flights so far, they are not
even close to knowing what the limi9ts for "easy" reflight , "reflight
after major maintenance" and "likmit for reflights" are.


Again, bear with me: It's the max so far simply because they haven't had
that many payloads since the Block 3 was introduced!


And since they have only reflown 3 times, I am not sure the number 10
for the major refurb has been decided.


It's been decided, but might be revisited. They might decide 7 is a better
number, or 20.
But my guess is they'll stick with 10 for now.

snip
A one off isn't a big deal. But if DoD becomes a major customer and
wants all its launches on brand new stages without landing capability,
then this changes plans, especially when they try to transition frm
Falcon9 to BFR and try to shift resources to producing BFR.


Let's assume DoD becomes a major customer... this means what.. 2-3 flights a
year?
That's EASILY handled by the current capacity. And... given the margins the
DoD is willing to pay, this is a problem SpaceX would LOVE to have. "Oh, you
want more single-use stages, ok, we need to expand our plant a bit, it'll
cost you this much. Sign here." Generally MORE business from a client
willing to pay premiums isn't a bad thing.

The argumenmt I am trying to make is the business model of falcon9 is
re-usability.


I think you have the cart before the horse here.
The business model is "cheaper rockets". They're obtaining this in multiple
methods. Re-usability is only one of those methods.
Note they were already cheaper than the competition before they started to
re-use their rockets.

If one customer pops up and requires non-re-usable
Falcon9s and becomes a major customer, then this changes the business
model because SpaceX is now needing to produce disposable Falcon9s are a
much higher ration than the original business model had antitcipated.


Ayup. A horrible problem to have when the customer is clearly willing to pay
a premium. And again, even if DoD moved ALL their launches to SpaceX, it
wouldn't make that large of an impact. I think Jeff said they currently
have the capacity to build 12 cores a year. Last year, they launched I
think 23 cores. So, even if they magically, per JF logic only use a core 3
times, they only need to build 8 cores a year. And if the DoD is willing to
pay a premium for the other 4 build cores, that's great.



So this also changes any plans they had to reduce production so
resources can be assigned to ramping up production of BFR/BFS.


Not really. At the current rate, they'll have more cores than they'll need
in a year or two.


Remember that BFR/NFS will be a HUGE drain on cash, and if it was to
have been funded by re-using Falcon9s a lot instead of building new ones
all the time, and now, they have to keep on building them, this changes
things.

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.


Which begs the following question: If Falcon9 is underpowered, and has
no margin for a high percentage of launches, was there much of a point
is making it re-usable?


That actually doesn't beg the question. First you have to prove that there's
no margin for a high percentage of flights.
There were 19 launches last year (18 F9, 1 FH).

Of those, 9 (F9, I'm not including the FH) were successful landings, 1
additional was attempted and failed.
So, less than 1/2 were not re-usable. Oh and one more was scheduled for a
landing, but due to weather and not wanting to delay the launch, they
scrapped it. (note this was a Block 4, not Block 5, so they weren't going to
refly it anyway).
Oh and another wasn't recovered because they were test other landing
options.

--
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