|Cost per launch||US$2 million|
The SpaceX Starship system consists of a family of spacecraft collectively named Starship, a super-heavy booster called Super Heavy, and Earth-based support infrastructure, all under development by SpaceX. The whole SpaceX Starship system is a two-stage-to-orbit super heavy-lift launch vehicle and the world's tallest and most powerful rocket ever built, producing more than twice the thrust of the Saturn V. The launch system is fully reusable, capable of landing on Earth and being reused with minimal inspection and refurbishment time. These capabilities help the SpaceX Starship system reduce the cost of launching to space significantly, with the goal of US$2 million per launch.
At present, most manufacturing, assembly, and test flights of Starship prototypes have been conducted at the SpaceX South Texas launch site, referred to by SpaceX as Starbase, and also known by the FAA and legal documents as the Boca Chica launch site. The Starship spacecraft is a second stage of the system while launch, transporting propellant, cargo, and crew, and staying in low Earth orbit. After being refueled by one or more tanker Starships in orbit, the spacecraft would be capable of much higher performance at transporting cargo and crew to higher Earth orbits, other bodies' orbit, or land on the surface of bodies in the Solar System such as the Moon and Mars. The Starship spacecraft can also launch from Mars back to Earth, providing that the crew fuel the spacecraft using on-site propellant. Starship variants are optimized to perform specific tasks, such as travel to the edge of the Solar System to deliver space probes or to designated spaceports on the Earth's surface. NASA has contracted SpaceX to develop a crew-rated Starship vehicle variant known as the Starship Human Landing System that serves as the lunar lander for the Artemis program.
Conception and initial designs
The vehicle's name has changed many times between its first announcement and during the first several years of development. At least as early as 2005, SpaceX used the codename "BFR" for a conceptual heavy‑lift launch vehicle, "far larger than the Falcon family of vehicles."
The launch vehicle was initially mentioned in public discussions by Musk in 2012 as part of a description of the company's overall future Mars program. It was then known as the "Mars Colonial Transporter," with nine Raptor engines on a single stage, similar to the arrangement of nine Merlin engines on each Falcon 9 booster core, in order "to put over 100 tons of cargo on Mars." The system's shortened name was changed to BFR one year later, which has been referred to formally as the "Big Falcon Rocket," and informally by the media and internally at SpaceX as the "Big Fucking Rocket." The second stage and spacecraft were referred to as the "Big Falcon Ship" and the booster as "Big Falcon Booster," with similar informal names given to them.
IIn mid‑September 2016, the launch system was renamed "Interplanetary Transport System," with the booster engine design revealed to contain 42 engines, with 21 Raptor engines on the outer ring and 14 on the middle ring fixed in place, while the seven-engine inner cluster can gimbal. The "Interplanetary Transport Spacecraft" have a nine-engines configuration, six Raptor vacuum-optimized engines around three sea-level Raptor engines cluster. SpaceX mentioned the theoretical possibility of using Starship to carry passengers on suborbital flights between two points on Earth in under one hour, providing commercial long‑haul transport to compete with long‑range aircraft. In September 2017, at the 68th annual meeting of the International Astronautical Congress, SpaceX unveiled an updated vehicle design. This design included a double stainless steel skin with active coolant flows between the two skin layers and multiple pores in the spacecraft for transpiration cooling, though subsequently removed in later designs.
In November 2018, the combination of the Starship spacecraft and Super Heavy booster were referred to collectively by the present name "Starship" or the "Starship system" by SpaceX in their payload user's guide. The second stage of the system was ambiguously named Starship, and the first stage booster was dubbed Super Heavy. Around that time, Musk showed another redesigned concept for the second stage and spaceship with three rear fins and two front canard fins for atmospheric entry, replacing the previous delta wing and split flaps shown a year earlier.
In January 2019, Musk announced that the Starship's structure and tanks would construct from stainless steel rather than carbon fiber composites. The strength‑to‑mass ratio of the new design should be comparable to or better than the earlier SpaceX design alternative of carbon fiber composites, from the low temperatures of cryogenic propellants to the high temperatures of atmospheric reentry. In October 2019, the Starship spacecraft's engine configuration changed to the current form, with six Raptor engines, three optimized for sea‑level and three optimized for vacuum. During that time, the spacecraft's fins arrangement changed to the current form, with a pair of aft fins at the bottom and forward fins at the top.
Development and testing
All Starship spacecraft and Super Heavy booster prototypes were constructed at the SpaceX South Texas launch site, referred to by SpaceX as Starbase, and also known as the Boca Chica launch site by legal documents. Starship prototypes are subjected to several tests on the launch stand before launch, including ambient-temperature pressure tests, wet dress rehearsal, and static fire of the engines. During the ambient-temperature pressure test, inert nitrogen gas fills the test article's propellant tanks, which checks for leaks and verifies plumbing performance and a basic level of structural integrity. The wet dress rehearsal involves loading and unloading supercool propellant, which tests the tanks' strength. For some test articles with thrust structures, a hydraulic ram was attached to the thrust puck to simulate the thrust of Raptor engines. Finally, a static fire test is performed by loading liquid oxygen and liquid methane and firing the Raptor engines briefly while Starship is on the test stand.
The Starship spacecraft is 50 m (160 ft) tall and 9 m (30 ft) in diameter. It is a fully reusable spacecraft with a dry mass of 120 t (120 long tons; 130 short tons) or less. The spacecraft acts as the second stage of the launch system to reach orbital velocity on launches from Earth. Starship also functions as a long‑duration spacecraft and a single-stage-to-orbit rocket when launches from Mars, the Moon, and other planets and moons. Starship is also capable of re-entering Earth's atmosphere from orbital velocities and landing vertically, with a design goal of rapid reusability without the need for extensive refurbishment. The spacecraft is capable of being refueled in space for most missions beyond Earth's orbit.
The Starship spacecraft's body is composed of rolls of 304L stainless steel sheets 4 mm (0.16 in) thick and 72 in (180 cm) wide. The sheets then get bent into "rings" that measure 9 m (30 ft) in diameter, which are then stacked by cranes and welded together to form main segments of the Starship vehicle. In the future, proprietary "30X" stainless steel alloy will be used instead of 304L stainless steel.
The bottom-most section, informally called the "skirt," houses the Raptor engines, as well as composite overwrapped pressure vessels that store helium gas used to spin up the Raptor turbopumps. Above the engine section are the liquid oxygen and liquid methane propellant tanks, separated by a "common dome" containing a small, spherical methane "header tank" used to contain propellant for landing. Six Raptor engines power the spacecraft, three designed for sea-level operation and three Raptor Vacuum engines optimized for use in the vacuum of space, producing a cumulative thrust of about 14 MN (1,400 tf; 3,100,000 lbf).
The payload section is situated above the propellant tanks and used to house cargo, crew, or both. Variants of Starship designed to transport satellites will possess a large "clamshell fairing door" that remains closed during launch, opens in orbit to release payloads, and closes again during return to Earth. Unlike a conventional rocket payload fairings jettisoned and expended during ascent, the clamshell door will enable Starship to capture and return satellites to Earth. SpaceX claims that Starship will possess "the largest usable payload volume of any current or in development launcher." Crewed Starships will feature cabins, solar storm shelters, storage space, a viewing gallery, and carry up to 100 passengers. The payload section also carries the liquid oxygen header tank, as well as auxiliary equipment such as avionics, batteries, and communications equipment.
Starship possesses two pairs of actuated "body flaps" that are mounted perpendicularly to the spacecraft's body and are used to control attitude during reentry and descent. A larger pair of aft flaps are located at the bottom of Starship, while a smaller pair of forward flaps are located near the nose cone. The body flaps are actuated using electric motors manufactured by Tesla, and serve to create additional drag and control the vehicle's attitude during descent.
To enable recovery and reuse of Starship from orbit, as well as enable Starship to land on Mars, the vehicle is equipped with a heat shield made of hexagonal ceramic tiles. The tiles cover the windward side of Starship and protect the vehicle from the harsh conditions of atmospheric entry. SpaceX simulations project that 99.9% of the vehicle's kinetic energy can be dissipated upon reentry on Earth, and 99% of the vehicle's kinetic energy can be dissipated on Mars entry despite the much thinner atmosphere.
SpaceX has announced that Starship will eventually be built to several operational variants. The Starship cargo variant is likely to be the earliest operational variant, as it doesn't involve crew and leaving Earth's orbit. The original spacecraft variant is intended to exclusively fly cargo transport missions initially and that passenger flights would come only much later. The spacecraft would be able to transport and place spacecraft into orbit, with a large cargo bay door that can open in space to facilitate the delivery and pickup of cargo. The Starship crew variant would be a large, long‑duration spacecraft capable of carrying passengers or cargo to low Earth orbit, the Moon and Mars. As envisioned in the 2017 design unveiling, the Starship specialized for a Mars mission might have a pressurized volume of approximately 825 m3 (29,100 cu ft), which could be configured for up to 40 cabins, large common areas, central storage, a galley, and a solar flare shelter for Mars missions.
For transporting space probes, cargo, and crew to higher orbits or at further interplanetary or interstellar space destinations, propellant cargo‑only propellant tankers would rendezvous with and refuel the spacecraft in Earth orbit. The tanker variant is designed to be light and reusable, designed to be able to perform automatic rendezvous and docking operations and on‑orbit propellant transfer to Starships. This variant is expected to come later; initial in‑space propellant transfer will be from one modified standard Starship to another.
The Starship design is expected to be flexible. For example, a possible modification to the base Starship would have only an expendable three‑engine Starship with no fairing, rear fins, or landing legs, to optimize its mass ratio for interplanetary exploration with robotic probes.
NASA Human Landing System
In April 2021, NASA contracted SpaceX to manufacture a modified variant of Starship, known as the Starship Human Landing System, to serve as the crew-carrying lunar lander for the Artemis program. Under the contract, Starship HLS would carry out two lunar landing missions, the first being an uncrewed demonstration test and the second being a crewed lunar landing occurring as early as 2024.
Starship HLS, being optimized for the cislunar spaceflight regime, has several large differences from the main Starship design, most notably the removal of the heat shield and body flaps, as the ship will not be returning to Earth. The spacecraft will also be equipped with a docking port, solar panels, and additional landing thrusters placed much higher up on the ship to minimize dust clouds during landing. SpaceX also envisioned a lunar cargo lander for transferring high-mass cargoes from the Earth's surface to the Moon under the Commercial Lunar Payload Services program, which is not required to leave the lunar surface.
Super Heavy booster
The booster stage Super Heavy is 69.5 m (228 ft) long and is 9 m (30 ft) in diameter, designed to hold subcooled liquid methane and liquid oxygen propellant like the Starship spacecraft. In mid-2021, the design was changed to not include legs, since the booster would be captured by the launch tower. The booster is powered by 29 or 33 sea-level variant Raptor engines that provide approximately 74,000 kN (17,000,000 lbf) total liftoff thrust, although expected thrust can change as the design progresses. The propellant capacity of Super Heavy is approximately 3,400 t (7,500,000 lb).
Super Heavy uses the same stainless steel rings for its construction as the Starship spacecraft. The first three bottom steel rings house the thrust dome, the bottom of the liquid oxygen tank, and COPVs used for autogenous pressurization of the fuel tanks of Super Heavy. Unlike the Starship spacecraft where Raptor engines mount inside the skirt section, 29 or 33 of them are mounted directly to Super Heavy's bottom. Super Heavy is also equipped with a thrust puck and a complicated feed system that feeds the Raptor engines with propellant. On top of the rings at the bottom are the four four-ring sections which serve as the liquid oxygen tank wall. The next four rings contain the common dome, which separates the two propellant tanks. The three steel sections above the common dome section are the wall for the liquid methane tanks, which are four, three, and three rings high from bottom to top. Finally, a forward dome inside a three-ring high section tops off the construction and the methane tanks. The top section has a mounting adapter for Starship to stack on top of Super Heavy.
The launch tower is 479 ft (146 m) tall, with 469 ft (143 m) being steel tower trusses and a 10 ft (3.0 m) long lightning rod. The launch tower also contains fuel pipes, data cable, and power lines in the quick disconnect arm, as well as an internal elevator for easy access to the tower and Starship system. The tower also has a large gantry pulley and "chopstick arms," which are used to lift the Super Heavy booster and Starship spacecraft and catch the booster.
Although the original concept used landing legs on both the booster and the spacecraft, SpaceX decided to incorporate a catching system into the launch tower instead. The catching system includes arms that will be able to move up and down along the tower and side to side on pivots, with a cable system that will match the speed of incoming Super Heavy's that touch down using its grid fins. This system simplifies the Starship system's reusability feature since it will be used to catch the Super Heavy booster upon return from launch and the spacecraft upon return from orbit and also to lift the booster and the spacecraft into position, allowing for a speedy turn-around time. In December 2020, Musk added the possibility of catching the booster by the small pins using the launch tower arm, eliminating the need for landing legs and further simplifying recovery processes.
Cost and planned usage
Starship is intended to become the primary SpaceX orbital vehicle. SpaceX intends to eventually replace its existing Falcon 9, Falcon Heavy, and Dragon 2 fleet with Starship, which is expected to take cargo to orbit at a far lower cost than any other existing launch vehicle. In November 2019, Elon Musk estimated that fuel will cost $900,000 per launch and operational costs per launch could drop as low as $2 million.
In addition to the commercial launch market that SpaceX has been servicing since 2013, the company intends to use Starship to launch the largest portion of its internet satellite constellation, Starlink, with more than 12,000 satellites intended to be launched by 2026, more than six times the total number of active satellites in orbit in 2018. An orbital launch of Starship could place up to 400 Starlink satellites into orbit with a single launch, whereas the Falcon 9 flights in 2019‑2020 can launch a maximum of 60 satellites per flight. Beyond the low-Earth orbit launches performed by Falcon 9 and Falcon Heavy in the 2010s, the Starship system is an architecture designed to perform many diverse spaceflight missions, due to the very low mission marginal cost.
Funding and contracts
The development work on the two-stage launch vehicle design has been nearly entirely privately funded by SpaceX. The entire project is possible only as a result of SpaceX's multi-faceted approach focusing on the reduction of launch costs. However, the speed of commercially available Mars transport for both cargo and humans will be driven, in large part, by market demand as well as constrained by the technology development and development funding.
In January 2016, the United States Air Force signed a contract with SpaceX $33.7 million to develop a prototype Raptor engine for a methalox upper stage for Falcon 9 and Falcon Heavy, with up to a further $61.4 million available for additional requirements. SpaceX has no plans to develop a methalox second stage for the Falcon launch vehicles but the Air Force wanted this technology to be developed.
Beginning in 2019, SpaceX began to offer specific services to potential future customers using Starship, Super Heavy, or Raptor engine technologies. In June 2019, SpaceX indicated they could potentially launch commercial payloads using Starship as early as 2021, which can result in the recognition of revenue before a flight is launched. On September 14, 2018, Yusaku Maezawa contracted SpaceX for a nine-crew private circumlunar lunar mission called the dearMoon project, in which Yusaku would give the remaining 8 seats to anyone around the world. In October 2020, NASA awarded SpaceX $53.2 million to conduct a large-scale flight demonstration to transfer 10 metric tons of cryogenic propellant between the tanks of two Starship vehicles.
In April 2020, NASA announced they would pay SpaceX $135 million for initial design work of a variation of the Starship second‑stage vehicle and spaceship called the Starship Human Landing System as one of three potential lunar human landing systems for the NASA Artemis program. On 16 April 2021, NASA selected SpaceX's Starship for the human landing system, awarding SpaceX with a contract valued at $2.89 billion spread over several years.