JF Mezei wrote on Sat, 29 Dec 2018
13:01:49 -0500:

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.


There is a lot more to GPS than you're aware of.


But it is critical in that being the first of new generation, they want
to test/evaluate it likely before launching the rest.


No. It is 'critical' because it is a Block III bird.


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 ?

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?


Since they're easily removed and designed for that, why wouldn't you?


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.


You're like a two-year-old. Everything is RIGHT NOW. What you've
read here is that there are plans to reduce and eventually shut down
Falcon 9 production. This hasn't really changed. Once a sufficiently
large stock of Falcon 9 exists I'd still expect them to shut down that
production line.


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?


I would currently anticipate that BFR/BFS will be ready around
2024-25. Add another 5-10 years for them to become 'routine' and
demonstrated reliable.


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 ?


The biggest bottleneck is skilled workers.


Also, while it is mentioned that this "had" to be expendable due to
performance, is that really really the case? Reading that article,
especially the section about lawsuits, I get the feeling that someone
wanted the SpaceX flights to be more expensive so as to not make the ULA
costs look so absurd.


Your 'feelings' are not evidence. This launch was to an excessively
high inclination, so they still had to do a large plane change. I
seriously doubt ULA costs had anything to do with it beyond Congress
telling USAF that they need to get cheaper launches.


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 ?


A plane change is a plane change. They had to make a large plane
change to get this bird on orbit.


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, ONCE THERE IS A SUFFICIENTLY LARGE EXISTING INVENTORY. Doh!


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 ?


Once it has demonstrated reliability it will be cheaper to launch
EVERYTHING on BFR/BFS because of the order of magnitude increase in
reusability.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn