In article ,
says...

On 2018-12-29 08:23, Jeff Findley wrote:

Prior DOD launches on Falcon 9 were not considered "National Security"
launches, from every article I've read. GPS III is considered to be
critical for US forces, unlike prior DOD launches on Falcon 9.

I have to wonder what the "critical" designation is. Adding 1 satellite
to existing GPS constellation simply complements an existing service.

Soldiers in battle would depend on the new GPS III satellites. DOD
doesn't want to lose anything that soldiers would depend upon directly.
The payloads SpaceX launched before this weren't critical for soldiers
in battle.

The Air Force wanted to reserve as much propellant as possible to
insure
the success of the primary mission. They dictated no landing attempt,
so no grid fins or landing legs on this mission.

From an actual performance point of view, would legs and fins make a
noticeable dent in performance? (akaL is the dead weight worth the cost
or removing them ?

Any extra mass on the first stage impacts performance, a bit. It's not
1:1 like on the upper stage, but it still has an impact.

Since this was a new build, it is a no brainer to simply not install
them during assembly, but had this been a re-used block 5, would SpaceX
have bothered removing them?

DOD is currently specifying new Falcon 9 hardware only. DOD has not
certified already flown Falcon 9 first stages for DOD use.

Also, Falcon production lines are obviously not shut down as the
"hopper" prototype for Starship hasn't even flown once yet. So no, I
doubt this impacts their manufacturing plan one iota.

OK, so so far, all that has changed was the end of development for Falcon9 ?

I had read here that there were plans to sut down production of Falcon9
now that block 5 could be re-used many times.

If they did this, they would need maybe 50 first stages (my guess) to
take into account stages lost to mishaps (like the recent stage that
landed in the ocean instead of on land) and to take into account
customers specifying new stages only (i.e. DOD). If this happens, it
won't be for quite some time. They don't have anywhere near that many
Block 5 first stages built yet.

Do you have a cite which says exactly when they plan on stopping Falcon
9 first stage production? I certainly don't.

If DoD becomes a major
customer and insists on wasting perfectly good stages, won't that force
SpaceX to change its plans and continue to produce them for much longer
than originally anticipated?

Like I said above, I personally think they're a few years away from
making this decision.

I take it that the floor/building space and tooling for Falcon9
construction isn't going to be needed for BFR/BFS and that the two can
proceed at the same time ?

From what has been reported, BFR/BFS is being built at a different
facility, so I would think Falcon production could most certainly
continue in parallel (at least as far as facilities are concerned).

GPS satellites are about halfway to geosync and not at equatotial
inclination, so no need to "undo" the latitude you are launching from.
Or are those satellites much heavier than what is normnally launched to
geosync ?

I believe this launch was to a much higher inclination than due east
from KSC (55 degrees inclination according to the article below).

https://www.nasaspaceflight.com/2018...gps-iii-first-
national-security-mission/

According to above, the Falcon 9 placed the GPS III satellite into an
orbit that was 1,200 km x 20,000 km. Another source says that GPS
satellites operate at 20,200 km (12,550 miles) in altitude.

So no, not as high as geosynch, but into a "medium" earth orbit, which
isn't terribly easy to reach.

No sane company stops selling the previous model abruptly.

What I had been told here was that Musk planned to shut production of
new block 5s and just keep re-using the ones that were built.

Yes, eventually. But SpaceX has only produced a handful of Falcon 9
Block 5 first stages so far.

BTW, once BFR is running, if the Falcon9 is truly at its performance
limit for GPS satellites, won't it become cheaper to launch on BFR which
will have pklenty fo spare performance to return and be re-used, thuse
lowering price ?

Maybe, if BFR/BFS is as successful as planned. That's not a given. The
BFS "hopper" hasn't even flown once, let alone the full up BFR/BFS.

Jeff
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