Falcon 9 Full Thrust

Full Thrust — also known as v1.2 or Block 3 — solved a margins problem with a simple piece of physics: chill the propellants below their boiling point to raise their density and pack more mass into the same tanks. Liquid oxygen is loaded sub-cooled and the RP-1 is refrigerated too. The result was 17% more thrust without enlarging the structure. To that were added a stretched second stage holding more propellant, an improved stage separation system and the reinforced helium bottle struts, the direct fix for the CRS-7 failure.

With those changes capacity rose to 22,800 kg to low Earth orbit and 8,300 kg to geostationary transfer orbit in expendable configuration. Flying to recover the stage, those figures drop to 17,500 kg and 5,500 kg with a drone ship landing, and to 3,500 kg to GTO if the stage returns to the launch site. Towards Mars the vehicle is rated at 4,020 kg. Liftoff mass settled at 549,000 kg and the first stage delivers 6,800 kN over 162 seconds, with a 934 kN Merlin 1D Vacuum on the second stage — 840 kN in the short-nozzle variant — and 348 s of specific impulse.

The maiden Full Thrust flight, on 22 December 2015, carried eleven Orbcomm OG2 satellites and ended with the first stage settling onto the landing zone at Cape Canaveral. It was the first propulsive return and the first intact recovery of an orbital-class booster in history. In April 2016 SpaceX repeated the feat on an autonomous drone ship in the Atlantic, far harder because of the moving platform and the tighter propellant margins. The version turned landing from an exception into a routine.

The next step came on 30 March 2017 with the SES-10 mission: for the first time a previously flown orbital-class booster — B1021, recovered after CRS-8 — launched and landed again. On that same flight SpaceX recovered a fairing half for the first time, thanks to control thrusters and a steerable parachute that set it down gently on the water.

On 1 September 2016 a Falcon 9 Full Thrust was destroyed on the pad during propellant loading ahead of a static fire test, with the AMOS-6 satellite already mounted. The investigation pointed to the composite helium bottles submerged in sub-cooled liquid oxygen: solid oxygen trapped between the fibre layers is believed to have reacted through friction. SpaceX changed the loading procedure and flew again in January 2017. The episode does not count as an in-flight failure, but it cost four months of stand-down and a satellite.

Over its life Full Thrust took on the Autonomous Flight Safety System (AFSS), first used operationally on CRS-10 in February 2017, which replaces ground radars and personnel with on-board decision logic; from March 2017 every SpaceX launch has used it. In June 2017, on the Iridium NEXT 11-20 flight, the aluminium grid fins were replaced with titanium ones, more resistant to re-entry heating and reusable without servicing.

Its last flight as Block 3 was the Spanish Paz satellite, on 22 February 2018, which also carried the two Tintin prototypes of the Starlink constellation. By then Full Thrust was already evolving into Block 4 and Block 5.