The ITS launch vehicle was a 2016–2017 design for a privately funded very large -diameter orbital launch vehicle planned to be developed by SpaceX. Design work was discontinued in 2017 when development was shifted to a smaller 9-meter version with approximately one-third the payload capability, announced under the project name BFR, and subsequently renamed "Starship/Super Heavy" in 2018, and then sometimes just "Starship" by SpaceX in September 2019, but then "Starship and Super Heavy" once again in October 2019. The initial design objective of the ITS launch vehicle was to launch a variety of SpaceX Mars transportation infrastructure missions to Mars and other destinations in the beyond-Earth-orbit portion of the Solar System. The first launch was not expected before the 2020s.
The ITS launch vehicle was to be operated as a somewhat unusual two-stage rocket. Its first stage was to have been powered by 42 Raptor rocket engines—designed and manufactured by SpaceX—operating on densified (chilled near triple point) methane/oxygen, propellants that have not been widely used as rocket propellants in the past. Like the Falcon 9 orbital launch vehicle that preceded it, the ITS launch vehicle's first stage design was intended to be reusable, following a return to the launch site and vertical landing following each launch. When announced, it was also designed to have a new feature for SpaceX launch vehicles: full reusability of even the second-stage and orbital spacecraft as well. The large payload capacity of the launch vehicle placed it into the super-heavy lift class, with the ability to place into low Earth orbit in reusable configuration and in expendable mode.
The second stage of the Earth launch vehicle was planned to have two versions, the Interplanetary Spaceship for passengers and cargo and the ITS tanker to deliver propellants to Earth orbit. Both were to be powered by six vacuum-optimized Raptor rocket engines with three additional sea-level-nozzle Raptor engines for maneuvering. Thus, the element of the launch vehicle that was to provide second-stage acceleration to orbital velocity on all launches from Earth would also be used as an on-orbit spacecraft. The Interplanetary Spaceship was planned as a very long-duration carrier of both passengers and space cargo to interplanetary destinations, and was to have served as both a descent and ascent vehicle at Mars.
The high-level specifications for the vehicle were publicly announced in September 2016, but by July 2017, SpaceX had stated they would not build the -diameter vehicles as previously planned, but would instead build a "still large" but much smaller launch vehicle first. Subsequently, that was revealed to be the BFR in September 2017, a vehicle intended to cost-effectively replace and supersede all existing SpaceX launch vehicles and passenger/cargo spacecraft.
History
The launch vehicle was initially mentioned in public discussions by Elon Musk in 2012 as part of SpaceX description of its overall Mars system architecture, then known as the Mars Colonial Transporter (MCT). MCT was SpaceX's name for its privately funded development project to design and build a spaceflight system of reusable rocket engines, launch vehicles and space capsules to eventually transport humans to Mars and return them to Earth.
As early as 2007 however, Musk had stated a personal goal of eventually enabling human exploration and settlement of Mars. Bits of additional information about the mission architecture were released in 2011–2015, including a 2014 statement that initial colonists would arrive at Mars no earlier than the middle of the 2020s, and SpaceX began development of the large Raptor rocket engine for the Mars Colonial Transporter before 2014.
Musk stated in a 2011 interview that he hoped to send humans to Mars' surface within 10–20 years, and in late 2012 that he envisioned the first colonists arriving no earlier than the middle of the 2020s.
In October 2012, Musk first publicly articulated a high-level plan to build a second reusable rocket system with capabilities substantially beyond the Falcon 9/Falcon Heavy launch vehicles on which SpaceX had by then spent several billion US dollars. This new vehicle was to be "an evolution of SpaceX's Falcon 9 booster ... much bigger [than Falcon 9]." But Musk indicated that SpaceX would not be speaking publicly about it until 2013. In June 2013, Musk stated that he intended to hold off any potential IPO of SpaceX shares on the stock market until after the "Mars Colonial Transporter is flying regularly."
In February 2014, the principal payload for the MCT launch vehicle was announced to be a large interplanetary spacecraft named Mars Colonial Transporter, capable of carrying up to of passengers and cargo. Musk stated that Mars Colonial Transporter will be "100 times the size of an SUV". According to SpaceX engine development head Tom Mueller, concept designs at the time indicated SpaceX could use nine Raptor engines on a single rocket, similar to the use of nine Merlin engines on each Falcon 9 booster core, in order "to put over 100 tons of cargo on Mars." At that time, it appeared that the large rocket core that would be used for the booster to be used with MCT would be at least in diameter—nearly three times the diameter and over seven times the cross-sectional area of the Falcon 9 booster cores—and was expected to have up to three rocket cores with a total of at least 27 engines.
By August 2014, media sources speculated that the initial flight test of the Raptor-driven super-heavy launch vehicle could occur as early as 2020, in order to fully test the engines under orbital spaceflight conditions; however, any colonization effort was then reported to continue to be "deep into the future". Previously, the launch vehicle was known informally as the BFR ("Big Falcon Rocket or Big Fucking Rocket"), a name coined by Musk personally in reference to the BFG 9000 from the 1993 video game Doom. The spacecraft had a similar moniker: informally dubbed the BFS (for Big Fucking Spaceship), also coined by Musk. SpaceX indicated in 2014 that there may be more than one design in a family of SpaceX super-heavy lift launch vehicles.In January 2015, Musk said that he hoped to release details of the "completely new architecture" for the Mars transport system in late 2015 but those plans changed and, by the end of the year, the plan to publicly release additional specifics had moved to 2016. Musk stated in June 2016 that the first unmanned MCT Mars flight could happen as early as for 2022, to be followed by the first manned MCT Mars flight departing as early as 2024. Company plans as of mid-2016 continued to call for the arrival of the first humans on Mars no earlier than 2025. As of 25 August 2016, the rocket had not yet been given a formal name by SpaceX, although Musk commented on a proposal on Twitter to name it "Millennium". In his September 2016 announcement, Musk referred to the vehicle components as the "interplanetary booster", the "interplanetary spaceship", and the "tanker". In mid-September 2016, Musk noted that the Mars Colonial Transporter name would not continue, as the system would be able to "go well beyond Mars", and that a new name would be needed. The name selected was Interplanetary Transport System (ITS)although in an AMA on Reddit on Oct 23, 2016, Musk stated, "I think we need a new name. ITS just isn't working. I'm using BFR and BFS for the rocket and spaceship, which is fine internally, but...", without stating what the new name might be.
SpaceX CEO Musk unveiled details of the space mission architecture, launch vehicle, spacecraft, and Raptor engines that power the vehicles at the 67th International Astronautical Congress on September 27, 2016. The first firing of a Raptor engine occurred on a test stand in September 2016 as well.
In October 2016, Musk indicated that the initial prepreg carbon-fiber tank test article, built with no sealing liner, had performed well in initial cryogenic fluid testing, and that a pressure test of the tank at approximately 2/3 of the design burst pressure was slated for later in 2016, with the very large tank placed on an ocean barge for the test. This test was successfully completed in November 2016.
In July 2017, SpaceX made public plans to build a much smaller launch vehicle and spacecraft in lieu of building the ITS, and stated that the new system architecture had "evolved quite a bit" since the November 2016 articulation of the very large ITS launch vehicle. A key driver of the new architecture is to make the new system useful for substantial Earth-orbit and cislunar launches so that the new system might pay for itself, in part, through commercial spaceflight activities in the near-Earth space zone. In September 2017, the new smaller design was revealed to be the diameter launch vehicle, referred to by its "code name" BFR, with similar core vehicle structure (carbon fiber), engines (Raptor), and Mars mission architecture; but explicitly aimed at superseding and replacing the entire existing set of SpaceX launch vehicle and spacecraft offerings—Falcon 9, Falcon Heavy, and the Dragon spacecraft—with a more cost-effective LV, while being designed to be fully reusable like the ITS launch vehicle.
Description and technical specifications
The ITS launch vehicle stack was composed of two stages. The first stage was always to be an interplanetary booster while the second stage would have been either an interplanetary spaceship (for beyond-Earth-orbit missions) or an ITS tanker (for on-orbit propellant transfer operations).
Both stages of the ITS launch vehicle were to be powered by Raptor bipropellant liquid rocket engines utilizing the full flow staged combustion cycle with liquid methane fuel and liquid oxygen oxidizer. Both propellants would be fully in the gas phase before entering the Raptor combustion chamber. Both stages were intended to utilize a bleed-off of the high-pressure gas for autogenous pressurization of the propellant tanks, eliminating the problematic high-pressure helium pressurization system used in the Falcon 9 launch vehicle. The self-pressurization gas system is a critical part of SpaceX strategy to reduce launch vehicle fluids from five in their legacy Falcon 9 vehicle family to just two, eliminating not only the helium tank pressurant but all hypergolic propellants as well as nitrogen for cold-gas reaction-control thrusters.
The overall launch vehicle height, first stage and the integrated second-stage/spacecraft, was . Both stages of the ITS LV were to have been constructed of lightweight-yet-strong carbon fiber, even the deep-cryogenic propellant tanks, a major change from the aluminum-lithium alloy tank and structure material used in SpaceX Falcon 9 family of launch vehicles. Both stages are fully reusable and will land vertically, technology initially developed on the Falcon 9 launch vehicle first stages in 2012–2016. Gross liftoff mass is at a lift-off thrust of . ITS LV would be able to carry a payload to low Earth orbit of in expendable-mode and in reusable mode.
ITS booster
The first-stage ITS booster, or Interplanetary booster—was a -diameter, -high, reusable rocket to be powered by 42 sea-level rated Raptor engines producing some of thrust in each engine. Total booster thrust was to have been approximately , several times the thrust of the Saturn V Moon mission launch vehicle.
The design engine configuration included 21 engines in an outer ring and 14 in an inner ring, with these 35 engines fixed in place. The center cluster of seven engines were to be gimbaled for directional control, although some directional control to the rocket is also available by utilizing differential thrust on the fixed engines. Design thrust on each engine was aiming to be variable between 20 and 100 percent of rated thrust.