I remember when Falcon Heavy was formally announced at Space Access 2011 by Shotwell herself, though it had been in the SpaceX customer guide since circa 2006 as the "F9S9" (as opposed to the F9S5 that used five engine boosters). Much like Delta IV, it was originally supposed to use crossfed boosters, so the core was full at booster separation (like Delta IV was supposed to do, b/c Falcon 9/Heavy was largely designed by ex-McDD Delta guys).

Good to see FH continuing to launch high value NASA science missions, rather than the much more troubled Starship...