2018-02-12

@doug_ellison @dsfpspacefl1ght Found the source of the problem. The NASA database has the Falcon Block 1 performance. Version currently in production and set to fly in a few months is Block 5. SpaceX GNC team is submitting updated numbers.

@kerrbones @nextspaceflight Not enough ignition fluid to light the outer two engines after several three engine relights. Fix is pretty obvious.

@EmreKelly @nova_road @nextspaceflight East, to support high flight rates for F9 and dual ocean landings for FH side boosters

@octagrabber @nova_road @nextspaceflight No

@nova_road @nextspaceflight A Shortfall of Gravitas

@nextspaceflight A third is under construction

@DJSnM @doug_ellison @dsfpspacefl1ght Under consideration. We’ve already stretched the upper stage once. Easiest part of the rocket to change. Fairing 2, flying soon, also has a slightly larger diameter. Could make fairing much longer if need be & will if BFR takes longer than expected.

@DavideDF_ @doug_ellison @dsfpspacefl1ght Side boosters landing on droneships & center expended is only ~10% performance penalty vs fully expended. Cost is only slightly higher than an expended F9, so around $95M.

@doug_ellison @DavideDF_ @dsfpspacefl1ght https://t.co/LijrUMuJDq

@AngryPackOMeese @dlxinorbit @doug_ellison @dsfpspacefl1ght Of course :)

@AngryPackOMeese @dlxinorbit @doug_ellison @dsfpspacefl1ght Maybe that plan works out, but I will seriously eat my hat with a side of mustard if that rocket flies a national security spacecraft before 2023

@dlxinorbit @doug_ellison @dsfpspacefl1ght That was three years ago, before ULA cancelled all medium versions of Delta IV. Future missions have all Delta fixed costs piled on, so their cost is now $600M+ for missions contracted for launch after 2020. Nutty high.

@doug_ellison @dsfpspacefl1ght Both exhaust velocity (Isp) and mass ratio drive the rocket equation. Also thrust/mass matters a lot for Oberth effect. Delta upper stage Isp is good, but mass ratio and thrust are not.

@doug_ellison @dsfpspacefl1ght The performance numbers in this database are not accurate. In process of being fixed. Even if they were, a fully expendable Falcon Heavy, which far exceeds the performance of a Delta IV Heavy, is $150M, compared to over $400M for Delta IV Heavy.