Were liquid boosters on Shuttle ever realistic?

In article m,
says...

On 2017-10-27 18:49, Greg (Strider) Moore wrote:

Actually delivers? They've done 15 flights this year and expect at least 4
more (I'm not counting Heavy as I expect that will slip).

What percentage were re-used stage 1s ?

Google it. It's worth a Google.

SpaceX is basically at the "prototype" stage for reflying stages. It
hasn't delivered yet on high rate and quick turn around of reflying stages.

So what? They're doing better at turning around recovered first stages
to be re-flown faster than any of the competition (none of them are
doing this for their orbital launchers). They're also cheaper than just
about anyone else (for LEO and GTO payloads). So, who cares how long it
takes to turn around a Block 3 or Block 4?

Just because everyone has confidence that it will deliver, it doesn't
mean that it has delivered.

The Block 5 has improvements to the design to help with reuse. SpaceX
will only get better at this while the competition (aside from Blue
Origin, who's still working on the BE-4 engine for New Glenn) are not
even trying to reuse anything.

Also not clear what percentage of landings might cause more than a
easily replaced broken leg (compressed crush zone). Say, for sake of
discussion, only 50% of stages can be reflown, this could change SpaceX
plans to wind down Falcon 9 production to start BFR production because
they would need higher stock of new Falcon 9s to cope with fact they
aren't recyling 100% of stages.

The crush core is more likely to be used up on high energy launches. In
the future, these will be flown on Falcon Heavy, so that the side
boosters will land on concrete pads at Cape Canaveral and only the core
booster stage will need to land on the barge (with more fuel margin than
a Falcon 9 would have had). So this will get better with time.

So there needs to be more empirical data on landings, refurbishements
before SpaceX would know for sure how thing will pan out.

Bull****. They're already saving money by reusing recovered first
stages. That's what counts. Customers are already switching to flights
with reused first stages because they can get their payloads into orbit
faster than if they wait for a new first stage to be built. Getting
your satellite in orbit faster means it generates revenue sooner.

or it could be that even with the hard landings, the stages are far from
having any structural damage and fixing legs is the only repair needed,
so it become more of a 1 and 0 (either it lands and can be re-used
easily, or goes kaboom on landing).

This is more likely. That's why there is crush core inside the legs.
It's expendable. It's like an energy absorbing bumper on a car. A
"fender bender" destroys the bumper cover and the energy absorbing
material in the bumper, but saves the rest of the car from structural
damage. So, those leaning first stages on barges means the crush core
did its job.

And while "going kaboom" on landing hasn't happened in a while, is this
just stroke of luck, or has SpaceX realy gotten their software to work
reliably enough to conclude that "kabooms" won't happen again? How many
more landings before such a conclusion can be made?

There is always risk. There are no guarantees in life.

Jeff
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