Modifications from Falcon 9 v1.1
The third version of the Falcon 9 was developed in 2014–2015 and made its maiden flight in December 2015. The Falcon 9 Full Thrust is a modified reusable variant of the Falcon 9 family with capabilities that exceed the Falcon 9 v1.1, including the ability to "land the first stage for geostationary transfer orbit (GTO) missions on the drone ship"[14] The rocket was designed using systems and software technology that had been developed as part of the SpaceX reusable launch system development program, a private initiative by SpaceX to facilitate rapid reusability of both the first–and in the long term, second—stages of SpaceX launch vehicles.[15] Various technologies were tested on the Grasshopper technology demonstrator, as well as several flights of the Falcon 9 v1.1 on which post-mission booster controlled-descent tests were being conducted.[16]
In 2015, SpaceX made a number of modifications to the existing Falcon 9 v1.1. The new rocket was known internally as Falcon 9 Full Thrust,[17] and is also known as Falcon 9 v1.2, Enhanced Falcon 9, Full-Performance Falcon 9,[14] and Falcon 9 Upgrade.[18]
A principal objective of the new design was to facilitate booster reusability for a larger range of missions, including delivery of large commsats to geosynchronous orbit.[12]
Modifications in the upgraded version include: The modified design gained an additional 1.2 m of height, stretching to exactly 70 m including payload fairing,[13] while gaining an overall performance increase of 33 percent.[18] The new first-stage engine has a much increased thrust-to-weight ratio.
The full-thrust first stage booster could reach low Earth orbit as a single-stage-to-orbit if it is not carrying the upper stage and a heavy satellite.[22]
Versions launched in 2017 have included an experimental recovery system for the payload fairing halves. On 30 March 2017, SpaceX for the first time recovered a fairing from the SES-10 mission, thanks to thrusters and a steerable parachute helping it glide towards a gentle touchdown on water.[23]
On 25 June 2017 flight (Iridium NEXT 11–20), aluminum grid fins were replaced by titanium versions, to improve control authority and better cope with heat during re-entry.[24] Following post-flight inspections, Elon Musk announced the new grid fins likely will require no service between flights.[25]
- liquid oxygen subcooled to 66.5 K and RP-1 cooled to 266.5 K[19] for density (allowing more fuel and oxidizer to be stored in a given tank volume, as well as increasing the propellant mass flow through the turbopumps increasing thrust)
- upgraded structure in the first stage[18]
- longer second stage propellant tanks[18]
- longer and stronger interstage, housing the second stage engine nozzle, grid fins, and attitude thrusters[18][20]
- center pusher added for stage separation[18]
Autonomous flight termination system
SpaceX has been developing for some time an alternative autonomous system to replace the traditional ground-based systems that had been in use for all US launches for over six decades. The autonomous system has been in use on some of SpaceX' VTVL suborbital test flights in Texas, and has flown in parallel on a number of orbital launches as part of a system test process to gain approval for use on operational flights.
In February 2017, SpaceX's CRS-10 launch was the first operational launch utilizing the new Autonomous Flight Safety System (AFSS) on "either of Air Force Space Command's Eastern or Western Ranges." The following SpaceX flight, EchoStar 23 in March, was the last SpaceX launch utilizing the historic system of ground radars, tracking computers, and personnel in launch bunkers that had been used for over sixty years for all launches from the Eastern Range. For all future SpaceX launches, AFSS has replaced "the ground-based mission flight control personnel and equipment with on-board Positioning, Navigation and Timing sources and decision logic. The benefits of AFSS include increased public safety, reduced reliance on range infrastructure, reduced range spacelift cost, increased schedule predictability and availability, operational flexibility, and launch slot flexibility."[26][27]
Autonomous flight termination system
SpaceX has been developing for some time an alternative autonomous system to replace the traditional ground-based systems that had been in use for all US launches for over six decades. The autonomous system has been in use on some of SpaceX' VTVL suborbital test flights in Texas, and has flown in parallel on a number of orbital launches as part of a system test process to gain approval for use on operational flights.
In February 2017, SpaceX's CRS-10 launch was the first operational launch utilizing the new Autonomous Flight Safety System (AFSS) on "either of Air Force Space Command's Eastern or Western Ranges." The following SpaceX flight, EchoStar 23 in March, was the last SpaceX launch utilizing the historic system of ground radars, tracking computers, and personnel in launch bunkers that had been used for over sixty years for all launches from the Eastern Range. For all future SpaceX launches, AFSS has replaced "the ground-based mission flight control personnel and equipment with on-board Positioning, Navigation and Timing sources and decision logic. The benefits of AFSS include increased public safety, reduced reliance on range infrastructure, reduced range spacelift cost, increased schedule predictability and availability, operational flexibility, and launch slot flexibility."[26][27]
Block 4
In 2017, SpaceX started flying incremental changes to the Falcon 9 Full Thrust version, calling them "Block 4".[28] At first, only the second stage was modified to Block 4 standards, flying on top of a "Block 3" first stage for three missions: NROL-76 and Inmarsat-5 F4 in May 2017, and Intelsat 35e in July.[29] Block 4 was described as a transition between the Full Thrust v1.2 "Block 3" and the following Falcon 9 Block 5. It includes incremental engine thrust upgrades leading to the final thrust for Block 5.[30] The maiden flight of the full Block 4 design (first and second stages) was the NASA CRS-12 mission on 14 August 2017.[31]
Block 5
SpaceX announced in 2017 that another series of incremental improvements were in development, a Falcon 9 Block 5 version, which has succeeded the transitional Block 4. The largest changes between Block 3 and Block 5 are higher thrust on all of the engines and improvements on landing legs. Additionally, numerous small changes will help streamline recovery and re-usability of first-stage boosters. Alterations are focused on increasing the speed of production and efficiency of re-usability. SpaceX aims to fly each Block 5 booster ten times with only inspections in between, and up to 100 times with refurbishment.[32][33]
Block 5 second stages can be built with a mission extension kit to allow longer duration and/or more engine starts.
Rocket specifications
Falcon 9 Full Thrust specifications and characteristics are as follows:[13][29][34]
The Falcon 9 Full Thrust uses a 4.5 meter long[34] interstage which is longer and stronger than the Falcon 9 v1.1 interstage. It is a "composite structure consisting of an aluminum honeycomb core surrounded by a carbon fiber face sheet plies".[13] The overall length of the vehicle at launch is 70 meters, and the total fueled mass is 549,000 kg.[34] The aluminium-lithium alloy used is 2195-T8
