In 2001, Musk was on the Mars Society's board of directors and first presented his goal of enabling Mars colonization. In the 2000s and early 2010s, SpaceX made many vehicle concepts for delivering payloads and crews to Mars, such as space tugs, heavy-lift launch vehicles, Red Dragon capsules. The Mars plan was first formally proposed in 2016 International Astronautical Congress alongside a fully-reusable launch vehicle, the Interplanetary Transport System. Since then, in the late 2010s, the launch vehicle proposal was refined and renamed to Starship, and in 2020s is actively developed. Though many dates for the first human landing on Mars have been stated, as of March 2022[update] Musk stated 2029, the timeline is considered tentative and aspirational.
The basic tenet of SpaceX's Mars program is to reduce the cost of going to Mars, leading to the formation of large Martian settlements. By forming such settlements, it is claimed that this will ensure the long-term survival of the human species. Early missions to Mars will probably feature a small fleet of Starship spacecraft and funded by public–private partnerships. Once infrastructure was established and launch cost is reduced further, more people are expected to go to Mars to establish the first Martian colonies. The return from Mars to Earth will also be available. The plan has been criticized for not being thorough and impractical, as it solely focuses on the transportation aspect of colonizing Mars.
Before founding SpaceX in 2001, a year earlier, Musk joined the Mars Society's board of director for a short time. There, together with Jim Cantrell, they failed to scout for a low-cost rocket in Russia, leading to the formation of the company.: 30–31
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Reusable launch system
Two Falcon Heavy boosters landing at Cape Canaveral, Florida in the Falcon Heavy test flight
SpaceX is privately funding the development of orbitallaunch systems that can be reused many times, in a manner similar to the reusability of aircraft. SpaceX has been developing the technologies over several years to facilitate full and rapid reusability of space launch vehicles. The project's long-term objectives include returning a launch vehicle first stage to the launch site in minutes and to return a second stage to the launch pad following orbital realignment with the launch site and atmospheric reentry in up to 24 hours. SpaceX's long term goal is that both stages of their orbital launch vehicle will be designed to allow reuse a few hours after return.
The reusable launch system technology was developed and initially used for the first stage of Falcon 9. After stage separation, the booster flips around, an optional boostback burn is done to reverse its course, a reentry burn, controlling direction to arrive at the landing site and a landing burn to effect the final low-altitude deceleration and touchdown.
SpaceX intended (from at least 2014) to develop technology to extend reusable flight hardware to second stages, a more challenging engineering problem because the vehicle is travelling at orbital velocity.
Second stage reuse is considered paramount to Elon Musk's plans to enable the settlement of Mars. Initial concepts to make the second stage of Falcon 9 reusable have been abandoned.
As of 2021[update], SpaceX is actively developing the Starship system, with the intent to make it a fully-reusable two-stage launch vehicle, intended to replace all of its existing launch vehicles and spacecraft used for satellite delivery and human transport—Falcon 9, Falcon Heavy and Dragon—and also eventually support flights to the Moon and Mars. In addition it could be used for point-to-point transportation on Earth.
As early as 2007, Elon Musk stated a personal goal of eventually enabling human exploration and settlement of Mars, although his personal public interest in Mars goes back at least to 2001 at the Mars Society.: 30–31 SpaceX has stated its goal is to colonize Mars to ensure the long-term survival of the human species.
Methane was chosen for the Raptor engines because it is cheaper, do not build up of soot, and can be produced on Mars via the Sabatier reaction. The engine family uses a new alloy for the main combustion chamber, allowing it to contain 300 bar (4,400 psi) of pressure, the highest of all current engines. In the future, it may be mass-produced and cost about $230,000 per engine or $100 per kilonewton.
Starship is the launch vehicle's second stage and will serve as a long-duration spacecraft on some missions. The spacecraft is 50 m (160 ft) tall and has a dry mass of less than 100 t (220,000 lb). Starship's payload volume is about 1,000 m3 (35,000 cu ft), larger than the International Space Station's pressurized volume by 80 m3 (2,800 cu ft), and can be even bigger with an extended 22 m (72 ft)-tall volume.: 2 By refueling the Starship spacecraft in orbit using tanker spacecraft, Starship will be able to transport larger payloads and more astronauts to other Earth orbits, the Moon, and Mars.: 5
SpaceX plans to build a crewed base on Mars for an extended surface presence, which it hopes will grow into a self-sufficient colony. A successful colonization would ultimately involve many more economic actors than SpaceX, which to facilitate the growth of the human presence on Mars over many decades. Musk has made many tentative predictions about Starship's first Mars landing, the most recent one in March 2022 being 2029.
A scene of astronauts on Mars in the 2016 IAC presentation
As envisioned in 2016, the first crewed Mars missions might be expected to have approximately 12 people, with the primary goal to "build out and troubleshoot the propellant plant and Mars Base Alpha power system" as well as a "rudimentary base." In the event of an emergency, the spaceship would be able to return to Earth without having to wait a full 26 months for the next synodic period.
On Mars, to fuel return missions, resources on the planet such as subsurface water and carbon dioxide in the atmosphere will be used. The Sabatier reaction then may be used to create liquid methane and liquid oxygen, Starship's propellant, in a power-to-gas plant. On Earth, similar technologies can be used to create carbon-neutral propellant for the rocket.
Colonization and terraforming
Artist's conception of the process of terraforming Mars
The Mars program's ambition is to eventually be able to send a million people to Mars, using a thousand Starships sent during a Mars launch window. The notional journeys outlined in the November 2016 talk would require 80 to 150 days of transit time, with an average trip time to Mars of approximately 115 days (for the nine synodic periods occurring between 2020 and 2037). In 2012, Musk stated an aspirational price goal for such a trip might be on the order of US$500,000 per person, but in 2016 he mentioned that he believed long-term costs might become as low as US$200,000.
In July 2010, after the final launch of Falcon 1 a year prior, SpaceX presented launch vehicle and Mars space tug concepts at a conference. The launch vehicle concepts were called Falcon X, Falcon X Heavy, and Falcon XX; the largest of all is the Falcon XX with a 140 t (310,000 lb) capacity to low Earth orbit. To deliver such payload, the rocket was going to be as tall as the Saturn V and use six powerful Merlin 2 engines. Around 2012, the company first mentioned the Mars Colonial Transporter rocket concept in public. It was going to be able to carry 100 people or 100 t (220,000 lb) of cargo to Mars and powered by methane-fueled Raptor engines.
Red Dragon capsule
Two Red Dragon capsules on Mars, next to an outpost
The primary objective of the initial Red Dragon mission was to test techniques and technology to enter the Martian atmosphere with equipment that a human crew could conceivably use. The series of Mars missions were to be technology pathfinders for the much larger SpaceX Mars colonization architecture that was announced in September 2016. An additional suggested use for a mission called for a sample returnMars rover to be delivered to the Martian surface.
The program was conceived in 2011 as a potential NASA Discovery mission launching as early as 2022, and evolved over several years once it did not receive NASA funding from the 2013–2015 Discovery Mission program cycle. In April 2016, SpaceX announced that they had signed an unfunded Space Act Agreement with NASA, providing technical support, for a launch no earlier than 2018. In February 2017, SpaceX noted this launch date was delayed to no earlier than 2020. In July 2017, Elon Musk announced that development would be halted and resources redirected to Starship.
SpaceX illustration of the 2016 Interplanetary Transport System
On 26 September 2016, a day before the 67th International Astronautical Congress, the Raptor engine fired for the first time. At the event, Musk announced SpaceX was developing a new rocket using Raptor engines called the Interplanetary Transport System. It would have two stages, a reusable booster and spacecraft. The stages' tanks were to be made from carbon composite, storing liquid methane and liquid oxygen. Despite the rocket's 300 t (660,000 lb) launch capacity to low Earth orbit, it was expected to have a low launch price. The spacecraft featured three variants: crew, cargo, and tanker; the tanker variant is used to transfer propellant to spacecraft in orbit. The concept, especially the technological feats required to make such a system possible and the funds needed, garnered a large amount of skepticism.
In September 2017, at the 68th Annual International Astronautical Congress, Musk announced the BFR (Big Falcon Rocket), a revision to the Interplanetary Transport System's design. The rocket was still going to be reusable, but its launch capacity to low Earth orbit was reduced to 150 t (330,000 lb), and its body was smaller. Unlike its conceptual predecessor, the potential applications for the BFR were more varied. Variants of the BFR would be able to send satellites to orbit, resupply the International Space Station, land on the Moon, travel between spaceports on Earth, and ferry crew to Mars. In April 2018, the Mayor of Los Angeles confirmed plan for a BFR rocket production facility at the Port of Los Angeles, but it was cancelled around May 2020.
A year later in September 2018, Musk updated about the spacecraft's new two forward flaps at the top and three larger aft flaps at the bottom. Both set of flaps help control the spacecraft's descent, and the aft flaps are used as landing legs for the final touchdown. Two months later in November 2018, the rocket booster was first termed Super Heavy and the spacecraft was termed Starship.
Examination of Starship SN20's heat shield, September 2021
Starship's development is iterative and incremental, marked by tests on rocket prototypes. The first prototype to fly using a Raptor engine was called Starhopper. The vehicle had three non-retractable legs and was shorter than the final spacecraft design. The craft performed two tethered hops in early April 2019 and three months later, it hopped without a tether to around 25 m (80 ft). In August 2019, the vehicle hopped to 150 m (500 ft) and traveled to a landing pad nearby.
Mk1 was destroyed November 2019 during a pressure stress test and Mk2 did not fly because the Florida facility was deconstructed throughout 2020. SpaceX began naming its new Starship upper-stage prototypes with the prefix "SN", short for "serial number". No prototypes between SN1 and SN4 flew; SN1 and SN3 collapsed during pressure stress tests and SN4 exploded after its fifth engine firing. Starship SN5 was built with no flaps or nose cone, giving it a cylindrical shape. The test vehicle consisted of one Raptor engine, propellant tanks, and a mass simulator. On 5 August 2020, SN5 performed a 150 m (500 ft)-high flight, successfully landing on a nearby pad. On 3 September 2020, the similar-looking Starship SN6 successfully repeated the hop.
SN8 was the first complete Starship prototype and underwent four static fire tests between October and November 2020. On 9 December 2020, SN8 flew, slowly turning off its three engines one by one, and reaching to an altitude of 12.5 km (7.8 mi). The craft then performed the belly-flop maneuver and dove back through the atmosphere. As it tried to land, an issue with fuel tank pressure caused the prototype to lose thrust and impact the pad. On 2 February 2021, Starship SN9 launched to 10 km (6.2 mi) and crashed on landing, similar to SN8.
A month later, on 3 March 2021, Starship SN10 launched on the same flight path and landed hard, crushing its landing legs and exploded, probably due to a propellant tank rupture. Starship SN11, on 30 March 2021, flew into thick fog along the same flight path. During descent, the vehicle exploded, scattering debris up to 8 km (5 mi) away. Starship prototypes SN12, SN13, and SN14 were scrapped before completion, and Starship SN15 was selected to fly instead. The prototype features general improvement on its avionics, structure, and engines, incorporating prior prototype's failures. On 5 May 2021, SN15 launched, completed the same maneuvers as older prototypes, and landed softly after six minutes.
In July 2021, Super Heavy BN3 conducted its first full-duration static firing, lighting three engines. A month later, using cranes, Starship SN20 was stacked atop Super Heavy BN4 for the first time. SN20 was the first to include a body-tall heat shield, made of hexagonal heat tiles. In October 2021, the catching mechanical arms were installed onto the integration tower, and the first tank farm's construction was completed.
Illustration of a Starship rocket ready for launch
SpaceX aims to perform the first Starship orbital test flight in 2022. During the test flight, the rocket is planned to launch from Starbase, after which the Super Heavy booster will separate and perform a soft water landing around 30 km (20 mi) from the Texas shoreline. The spacecraft will continue flying with its ground track passing through the Straits of Florida and then softly land in the Pacific Ocean around 100 km (60 mi) northwest of Kauai in the Hawaiian Islands. The spaceflight will last ninety minutes.: 2–4
Reception and feasibility
SpaceX has not detailed plans for the spacecraft's life-support systems, radiation protection, and in situ resource utilization, technologies which are essential for space colonization.