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On 2017-10-31 06:24, Jeff Findley wrote:

I see, so you're picking on the "only three" reflight number and
ignoring the success of the 12 flights of "new" first stages?

My issue is with claims by cheerleaders that SpaceX had already proven
it was capable of high reflight rate, not high flight rate.

You guys have since admitted that the current batch will only get one
reflight (if any) and not till block 5 will multiple reflights be
possible. But have yet to agree that multiple reflights or quick
turnaround has yet to be demonstrated.

Block 3 was used to learn what needed to be improved for reuse to become
easier, but there is nothing fundamental about them that prevents them
from being flown more than once. Same for Block 4.

It's just that they're building Block 5 now, since it's needed for
commercial crew flights (all the bits NASA wanted for redundancy, abort,
and etc.), so switching all production to Block 5 makes sense.

Since Block 5 also has changes specifically designed to make reuse
easier (like a new base heat shield that doesn't need replaced after
every flight), it makes sense to start relying them a.s.a.p. This is
the reason Block 3 and Block 4 will only see one reflight for each
booster.

By the way, only three of those 15 flights this year have "expended" the
first stage, so they've gotten quite good at recovering stages.

Yes they have. But what is not YET known is the state of those 12
recovered stages and how much work is needed to put them on a launch pad
(or what percentage are not worth refurbishing).

Sure we do, there have been pictures of each and every one either on the
landing pad or on the barge coming into port. You know it's 2017 and
you can find pictures on the Internet, right? There are Reddit forums
for SpaceX that are quite active and they create sub-Reddit forums for
each landed booster. By looking at the pictures you can see that the
booster itself has always been intact.

3 have been reflown and a few more slated to refly, 5 out of 15 means
33% recovery rate. If they go up to 7, then roughly 50% recovery rate.

It's possible that all 12 can and will be recovered, but none of the
current launch plans show this. So this remains speculation by cheerleaders.

SpaceX always tries to recover the first stage, even if they know
they're not going to reuse it. The only exception is for launches where
the payload margins are so thin that there will be no fuel for a
recovery attempt. In that case it's damn obvious they're not going to
attempt recovery because the booster will be sitting on the launch pad
without landing legs or grid fins.

At any rate, there is now a huge backlog of boosters to refurbish and
refly. 2018 and 2019 should have a much higher portion of "previously
flown" stages than 2017.

If they accumulate landed new stages at faster rate than they can
refurbish them, then at one point, they have to start to throw some
away. So again, this is an unknown.

Bull****. This is known. That's why they have said publicly that Block
3 and Block 4 boosters will only be reused at most once.

There is a difference between what SpaceX plans to do and what it has done.

This is a truism and applies to all launch companies. It is therefore
meaningless.

And while there will always be a difference between its ambiutions and
what it has delivered (and nothing wrong with that), what is wrong is to
consider its ambitions to be "deone deal" when it hasn't been done yet,

No one has made that assertion here. I certainly have not to my
knowledge. I've just posted cites which state the facts of what they
have done and what they are planning to do.

The following are the facts:

1. SpaceX has had three successful reflights of a Falcon 9 first stage
with zero failures on reflight.
2. SpaceX has successfully recovered a quite impressive number of first
stages, even for "high energy" launches where fuel reserves are low and
in fairly rough seas (like this week's recovery).
3. SpaceX has several more boosters scheduled for reflight including a
NASA commercial cargo flight scheduled for this December.
4. Block 5 is coming soon, because it's needed for commercial crew.

Conclusion? SpaceX is making significant progress on reuse in that
they've collected a lot of data from a lot of recovered stages which has
allowed them to tweak the design to optimize reuse. That's the Block 5.
No it's not flown yet, but a decent engineer would conclude that there
is a very good chance, based on the facts above, that it will in fact be
easier to reuse.

There is a difference between idle speculation and reasoning based on
available facts.

Jeff
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