Falcon 9 Block 5 Updates and Discussion

[abaddon]

OneSpeed's excellent analysis of AX-1 vs AX-2 telemetry shows clearly that the trajectories were basically identically until terminal guidance, with the 1st stage on AX-2 and an earlier MECO delivering the upper stage to a lower and slower drop-off than AX-1, with the upper stage made up the difference.  Ergo, not booster improvements, at least not ones that weren't already available for AX-1.  It's possible that there were improvements strictly limited to boost-back and landing, I suppose, but not the primary boost phase before stage sep.  So, unlikely to be a hardware improvement, more expanding the flight envelope, trusting the upper stage a little bit more, and transitioning to the 1-3-1 landing.  While still leaving enough margin all around to keep NASA happy.

[RDMM2081]

(snip)So, unlikely to be a hardware improvement, more expanding the flight envelope, trusting the upper stage a little bit more, and transitioning to the 1-3-1 landing.  While still leaving enough margin all around to keep NASA happy.

This was my assumption, more trust in the booster/2nd stage margins, and they ate just a little smidge into the life and death margins in order to have just enough more prop to spend on boostback which resulted in LZ1 vs droneship. But that's just my guess, nothing more.

[CuddlyRocket]

While still leaving enough margin all around to keep NASA happy.

It's not really up to NASA is it. Their sole concern is that Dragon approaches the ISS in a suitable condition. If Axiom and SpaceX went to use some of the second stage margin for other purposes that's at their risk.

[edkyle99]

Does Crew Dragon still weigh ~12.5t?

Gunter lists 12.055 tonnes, at least for the first Crew Dragon.  SpaceX doesn't publicize official spacecraft liftoff weight numbers to my knowledge.

 - Ed Kyle

[TrueBlueWitt]

While still leaving enough margin all around to keep NASA happy.

It's not really up to NASA is it. Their sole concern is that Dragon approaches the ISS in a suitable condition. If Axiom and SpaceX went to use some of the second stage margin for other purposes that's at their risk.

Word was that this would also be the case for NASA missions from here out.. so we'll see.

[Barley]

1. Operational improvements do matter.  Just because the hardware was capable five years ago doesn't mean the software and wetware were capable.  You don't get a time machine to go back and tell your past self all the slightly stupid stuff you should not have been doing.

This could include things like better operation of the grid fins to increase drag (hence reduce reentry and landing burns) or decrease drag (to get range needed for RTLS) or improved operations of the capsule and upper stage.

2. Operational improvements also apply to manufacturing.  Even without any explicit changes to specs or processes.  Figuring out how to hit the "center" of the specs can be useful.  For example if sheet metal is speced to be 1mm +- 0.002mm tuning the process to get 1mm+-0.001mm reduces variability which reduces the maximum mass you have to deal with.  In my experience with welds some welders will be embarrassed if you look at their five-year old welds, even though they were perfectly serviceable and passed all inspections (and have been working for five years).

Some people will argue that none of this should happen because the system should have been perfectly optimal from the start and because learning is bad.  This is a very limiting view and is impossible to actually achieve.