1. History

In 2001, Musk conceptualized "Mars Oasis", a project to land a miniature experimental greenhouse containing seeds with dehydrated gel on Mars to grow plants on Martian soil, "so this would be the furthest that life's ever traveled"^[1] in an attempt to regain public interest in space exploration and increase the budget of NASA.^[2][3][4] But Musk realized that even with a much larger space budget, travel to Mars would be prohibitively expensive without a fundamental breakthrough in rocket technology.^[4] In October 2001, Musk travelled to Moscow with Jim Cantrell (an aerospace supplies fixer), and Adeo Ressi (his best friend from college), to buy refurbished ICBMs (Dnepr) that could send the envisioned payloads into space.^[5]

As early as 2007, Elon Musk stated a personal goal of eventually enabling human exploration and settlement of Mars,^[6][7] although his personal public interest in Mars goes back at least to 2001.^[8] 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.^[9] Company plans in mid-2016 continued to call for the arrival of the first humans on Mars no earlier than 2025.^[10][11]

Musk stated in a 2011 interview that he hoped to send humans to Mars's surface within 10–20 years,^[7] and in late 2012 he stated that he envisioned a Mars colony of tens of thousands with the first colonists arriving no earlier than the middle of the 2020s.^[9][12][13]

Development work began in earnest before 2012 when SpaceX started to design the Raptor rocket engine which will propel the Starship launch system. Rocket engine development is one of the longest subprocesses in the design of new rockets.

In October 2012, Musk 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.^[14] 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.^[9][15] 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."^[16][17]

In August 2014, media sources speculated that the initial flight test of the MCT could occur as early as 2020, in order to fully test the engines under orbital spaceflight conditions; however, any colonization effort was reported to continue to be "deep into the future".^[18][19]

In January 2015, Musk said that he hoped to release details in late 2015 of the "completely new architecture" for the system that would enable the colonization of Mars. But those plans changed and, by December 2015, the plan to publicly release additional specifics had moved to 2016.^[20] In January 2016, Musk indicated that he hoped to describe the architecture for the Mars missions with the next generation SpaceX rocket and spacecraft later in 2016, at the 67th International Astronautical Congress conference,^[21] in September 2016.^[22][23] Musk stated in June 2016 that the first unmanned MCT Mars flight was planned for departure in 2022, to be followed by the first manned MCT Mars flight departing in 2024.^[10][24] By mid-September 2016, Musk noted that the MCT name would not continue, as the system would be able to "go well beyond Mars", and that a new name would be needed. This became the Interplanetary Transport System (ITS),^[25] a name that would, in the event, last for just one year.

On September 27, 2016, at the 67th annual meeting of the International Astronautical Congress, Musk unveiled substantial details of the design for the transport vehicles—including size, construction material, number and type of engines, thrust, cargo and passenger payload capabilities, on-orbit propellant-tanker refills, representative transit times, etc.—as well as a few details of portions of the Mars-side and Earth-side infrastructure that SpaceX intends to build to support the flight vehicles. In addition, Musk championed a larger systemic vision, a vision for a bottom-up emergent order of other interested parties—whether companies, individuals, or governments—to utilize the new and radically lower-cost transport infrastructure to build up a sustainable human civilization on Mars, potentially, on numerous other locations around the Solar System, by innovating and meeting the demand that such a growing venture would occasion.^[26][27] In the 2016 iteration, the system technology was specifically envisioned to eventually support exploration missions to other locations in the Solar System including the moons of Jupiter and Saturn.^[28]

In July 2017, SpaceX made public plans for the Interplanetary Transport System based on a smaller launch vehicle and spacecraft. The new system architecture has "evolved quite a bit" since the November 2016 articulation of the ITS. 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 economic spaceflight activities in the near-Earth space zone.^[29][30] The Super Heavy is designed to fulfill the Mars transportation goals while also launching satellites, servicing the ISS, flying humans and cargo to the Moon, and enabling ballistic transport of passengers on Earth as a substitute to long-haul airline flights.^[31]

SpaceX President and COO Gwynne Shotwell expressed in early 2018 that, even with the smaller 9-meter architecture, she sees the program as only the first step to interplanetary and interstellar spaceflight endeavors for SpaceX.^[32]

Musk indicated in November 2018 that "We've recently made a number of breakthroughs [that I am] just really fired up about." and that, as a result, he foresees a 70 percent probability that he personally would go to Mars. He answered an interviewer's question that included a presumption that "a Mars voyage could be an escape hatch for the rich" by saying:^[33]

"No. Your probability of dying on Mars is much higher than Earth. Really the ad for going to Mars would be like Shackleton’s ad for going to the Antarctic [in 1914]. It’s gonna be hard. There’s a good chance of death, going in a little can through deep space. You might land successfully. Once you land successfully, ... there's a good chance you'll die there. We think you can come back; but we're not sure."

2. Description

Artist's concept of SpaceX Starship passing by the Moon. https://handwiki.org/wiki/index.php?curid=1551634

SpaceX's Mars objectives, and the specific mission architectures and launch vehicle designs that might be able to participate in parts of that architecture, have varied over the years, and only partial information has been publicly released. However, once the architecture was unveiled in late 2016, all launch vehicles, spacecraft, and ground infrastructure have shared several basic elements.

2.1. Overview and Major Elements

The SpaceX Mars architecture, first detailed publicly in 2016, consists of a combination of several elements that are key—according to Musk—to making long-duration beyond Earth orbit (BEO) spaceflights possible by reducing the cost per ton delivered to Mars:^[34][35][36]

Additional detail on the Mars transportation architecture was added by Musk in 2017.^{[37]:33:30–36:55}

• a new fully reusable super heavy-lift launch vehicle that consists of a reusable booster stage and a reusable integrated second-stage-with-spacecraft that comes in at least two versions: a large, long-duration, beyond-Earth-orbit spacecraft capable of carrying passengers, bulk cargo, or propellant cargo, to other Solar System destinations.^[20][38] The combination of a second-stage of a launch vehicle with a long-duration spacecraft is unusual for any space mission architecture, and has not been seen in previous spaceflight technology.
• refilling of propellants in orbit, specifically to enable the long-journey spacecraft to expend almost all of its propellant load during the launch to low Earth orbit while it serves as the second stage of the launch vehicle, and then—after refilling on orbit—provide the significant amount of energy necessary to put the spacecraft onto an interplanetary trajectory.
• propellant production on the surface of Mars: to enable the return trip back to Earth and support reuse of the spacecraft, enabling significantly lower cost to transport cargo and passengers to distant destinations. Once again, the large propellant tanks in the integrated space vehicle are filled remotely.
• selection of the right propellant: Methane (CH₄)/oxygen (O₂)—also known as "deep cryo methalox"^[34]:16:25—was selected as it was considered better than other common space vehicle propellants like Kerolox or Hydrolox principally due to ease of production on Mars and the lower cost of the propellants on Earth when evaluated from an overall system optimization perspective. Methalox was considered equivalent to one of the other primary options in terms of vehicle reusability, on-orbit propellant transfer, and appropriateness for super-heavy vehicles.^[8]

2.2. Spacecraft

As of 2020, the SpaceX Starship is planned to be a long-duration cargo- and passenger-carrying spacecraft launched as the second stage of a reusable launch vehicle.^[39][40] While it will be tested on its own initially, it will be used on orbital launches with an additional booster stage, the Super Heavy, where Starship will serve as the second stage on a two-stage-to-orbit launch vehicle.^[41] The combination of spacecraft and booster is called Starship as well.^[42]

2.3. Mars Propellant Plant and Base

Musk plans to build a crewed base on Mars for an extended surface presence, which he hopes will grow into a self-sufficient colony.^[43][44] A successful colonization would ultimately involve many more economic actors—whether individuals, companies, or governments—to facilitate the growth of the human presence on Mars over many decades.^[26][27][45]

Since the Starships are also reusable, Musk plans on refueling them in low Earth orbit first, and then again on the surface of Mars for their return to Earth. During the first phase, he plans to launch several Starships to transport and assemble a propellant plant and start to build up a base.^[46] The propellant plant would produce methane (CH₄) and liquid oxygen (O₂) from sub-surface water ice and atmospheric CO₂.^[47]

Two robotic cargo flights, the first of which may be named "Heart of Gold",^[48] were originally aspirationally slated to be launched in 2022 to deliver a massive array of solar panels,^[44] mining equipment,^[46] as well as deliver surface vehicles, food and life support infrastructure.^[49] Additionally, it was originally planned that in 2024, the mission concept would have four more Starships follow: two robotic cargo flights, and two crewed flights will be launched to set up the propellant production plant, deploy the solar park and landing pads, and assemble greenhouses.^[49] Each landed mass will be at least 100 tons of usable payload, in addition to the spaceship's dry mass of 85 tons.^[49]

The first temporary habitats will be their own crewed Starships, as it is planned for them to have life-support systems.^[43][49] However, the robotic Starship cargo flights will be refueled for their return trip to Earth whenever possible.^[43] For a sustainable base, it is proposed that the landing zone be located at less than 40° latitude for best solar power production, relatively warm temperature, and critically: it must be near a massive sub-surface water ice deposit.^[49] The quantity and purity of the water ice must be appropriate. A preliminary study by SpaceX estimates the propellant plant is required to mine water ice and filter its impurities at a rate of 1 ton per day.^[49] The overall unit conversion rate expected, based on a 2011 prototype test operation, is one metric ton of O₂/CH₄ propellant per 17 megawatt-hours energy input from solar power.^[50] The total projected power needed to produce a single full load of propellant for a SpaceX Starship is in the neighborhood of 16 gigawatt-hours (58 TJ) of locally Martian-produced power.^[51] To produce the power for one load in 26 months would require just under one megawatt of continuous electric power. A ground-based array of thin-film solar panels to produce sufficient power would have an estimated area of just over 56,200 square meters (605,000 sq ft); with related equipment, the required mass is estimated to fall well within a single Starship Mars transport capability of between 100–150 metric tons (220,000–330,000 lb). Alternatively, extrapolating from recent NASA research into fission reactors for deep space missions, it is estimated that sufficient fission-reactor based electric power infrastructure might mass between 210 and 216 metric tons (463,000 and 476,000 lb), requiring at least two Starships for transport. A Mars power system using solar and vertical axis wind turbine design to produce sufficient power might mass just over 3.15 metric tons (6,900 lb).^[52]

The biggest lingering questions about SpaceX's Mars habitation plans have to do with health hazards of prolonged space travel, radiation, weightlessness, and habitation in the low gravity of Mars, which is 38% of the gravity of Earth.^[53][54][55]

2.4. Launch Site

As of September 2017, SpaceX stated that their next-generation launch vehicle is expected to replace the existing SpaceX launch vehicles—Falcon 9 and Falcon Heavy—as well as the Dragon spacecraft, and that is the launch vehicle that would be used to support the SpaceX Mars space transport architecture.^[47] The SpaceX leased launch facility at LC-39A will be used to launch Super Heavy.^[38]

When their earlier concept, then-named "Mars Colonial Transporter," was initially discussed in March 2014, no launch site had yet been selected for the super-heavy lift rocket and SpaceX indicated at the time that their leased facility at historic Launch Pad 39A would not be large enough to accommodate the vehicle as it was understood conceptually in 2014, and that therefore a new site would need to be built in order to launch the >10-meter diameter rocket.^[56] However, it was later revealed that the optimized size of the Raptor engine would be fairly close to the physical size of the Merlin 1D (although each engine has approximately three times the thrust), allowing the use of LC-39A for Super Heavy.^[38]

During a groundbreaking ceremony for the SpaceX South Texas Launch Site in September 2014, Elon Musk mused that the first person to go to another planet could possibly launch from Texas.^[57] Musk stated in September 2016 that the launch vehicle may launch from more than one site.

3. Mission Concepts

3.1. Lunar Tourism Mission

On September 14, 2018, SpaceX announced that a contracted passenger would be launched aboard the Starship to flyby the Moon in 2023.^[58][59] The passenger is the Japanese billionaire Yusaku Maezawa. The Starship will have a pressurized volume of 1,000 m³ (35,000 cu ft), large common areas, central storage, a galley, and a solar storm shelter.^[60]

3.2. Mars Early Missions

Musk has indicated that the earliest SpaceX-sponsored missions would have a smaller crew and use much of the pressurized space for cargo.^[61]

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.^[61]

Before any people are transported to Mars, some number of cargo missions would be undertaken first in order to transport the requisite equipment, habitats and supplies.^[62] Equipment that would accompany the early groups would include "machines to produce fertilizer, methane and oxygen from Mars' atmospheric nitrogen and carbon dioxide and the planet's subsurface water ice" as well as construction materials to build transparent domes for crop growth.^[9]

The early concepts for "green living space" habitats include glass panes with a carbon-fiber-frame geodesic domes, and "a lot of miner/tunneling droids [for building] out a huge amount of pressurized space for industrial operations." But these are merely conceptual and not a detailed design plan.^[61]

3.3. Mars Settlement Concept

As of 2016 when publicly discussed, SpaceX the company is concentrating its resources on the transportation part of the overall Mars architecture project as well as an autonomous propellant plant that could be deployed on Mars to produce methane and oxygen rocket propellants from local resources. If built, and if planned objectives are achieved, then the transport cost of getting material and people to space, and across the inner Solar System, will be reduced by several orders of magnitude. SpaceX CEO Elon Musk is championing a much larger set of long-term Mars settlement objectives, ones that take advantage of these lower transport costs to go far beyond what the SpaceX company will build and that will ultimately involve many more economic actors—whether individual, company, or government—to build out the settlement over many decades.^[26][27]

In addition to explicit SpaceX plans and concepts for a transportation system and early missions, Musk has personally been a very public exponent of a large systemic vision for building a sustainable human presence on Mars over the very long term, a vision well beyond what his company or he personally can effect. The growth of such a system over decades cannot be planned in every detail, but is rather a complex adaptive system that will come about only as others make their own independent choices as to how they might, or might not, connect with the broader "system" of an incipient (and later, growing) Mars settlement. Musk sees the new and radically lower-cost transport infrastructure facilitating the buildup of a bottom-up economic order of other interested parties—whether companies, individuals, or governments—who will innovate and supply the demand that such a growing venture would occasion.^[26][27]

While the initial SpaceX Mars settlement would start very small, with an initial group of about a dozen people,^[61] with time, Musk hopes that such an outpost would grow into something much larger and become self-sustaining, at least 1 million people. According to Musk,

Even at a million people you’re assuming an incredible amount of productivity per person, because you would need to recreate the entire industrial base on Mars. You would need to mine and refine all of these different materials, in a much more difficult environment than Earth. There would be no trees growing. There would be no oxygen or nitrogen that are just there. No oil.

Excluding organic growth, if you could take 100 people at a time, you would need 10,000 trips to get to a million people. But you would also need a lot of cargo to support those people. In fact, your cargo to person ratio is going to be quite high. It would probably be 10 cargo trips for every human trip, so more like 100,000 trips. And we’re talking 100,000 trips of a giant spaceship.^[63]

The notional journeys outlined in the November 2016 talk would require 80 to 150 days of transit time,^[45] with an average trip time to Mars of approximately 115 days (for the nine synodic periods occurring between 2020 and 2037).^[35] In 2012, Musk stated an aspirational price goal for such a trip might be on the order of US$500,000 per person,^[9] but in 2016 he mentioned that he believed long-term costs might become as low as US$200,000.^[45]

(As of September 2016), the project has financial commitments only from SpaceX and Musk's personal capital. The Washington Post pointed out that "The [US] government doesn't have the budget for Mars colonization. Thus, the private sector would have to see Mars as an attractive business environment. Musk is willing to pour his wealth into the project" but it will not be enough to build the colony he envisions.^[64]

In March 2019, Musk said that in his opinion it would be theoretically possible for a self-sustaining city on Mars to emerge by 2050.^[65]

3.4. Outer Planet Concepts

The overview presentation on the Mars architecture given by Musk in September 2016 included concept slides outlining missions to the Saturnian moon Enceladus, the Jovian moon Europa, Kuiper belt objects, a fuel depot on Pluto and even the uses to take payloads to the Oort Cloud.^[38] "Musk said ... the system can open up the entire Solar System to people. If fuel depots based on this design were put on asteroids or other areas around the Solar System, people could go anywhere they wanted just by planet or moon hopping. 'The goal of SpaceX is to build the transport system ... Once that transport system is built, then there is a tremendous opportunity for anyone that wants to go to Mars to create something new or build a new planet.'"^[8] Outer planet trips would likely require propellant refills at Mars, and perhaps other locations in the outer Solar System.^[45] Plans for the Starship have reiterated the idea of using it for missions to outer planets.^[32]

4. Funding

The extensive development and manufacture of much of the space transport technology has been through 2016, and is being privately funded by SpaceX. The entire project is even possible only as a result of SpaceX multi-faceted approach focusing on the reduction of launch costs.^[38]

(As of October 2016), SpaceX was expending "a few tens of millions of dollars annually on development of the Mars transport concept, which amounts to well under 5 percent of the company’s total expenses",^[45] but expects that figure to rise to some US$300 million per year by around 2018. The cost of all work leading up to the first Mars launch was expected to be "on the order of US$10 billion"^[45] and SpaceX expected to expend that much before it generates any transport revenue.^[27] No public update of total costs before revenue was given in 2017 after SpaceX redirected to the small launch vehicle design of the BFR.

Musk indicated in September 2016 that the full build-out of the Mars colonialization plans would likely be funded by both private and public funds. 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.^[27][45] In October 2017, he reiterated that "the actual establishment of a base was something that would be handled largely by other companies and organizations. ... 'Our goal is get you there and ensure the basic infrastructure for propellant production and survival is in place', he said, comparing the BFR to the transcontinental railways of the 19th century. 'A vast amount of industry will need to be built on Mars by many other companies and millions of people'.^[66][67]

In 2016, Elon Musk stated that there is no expectation of receiving NASA contracts for any of the Mars architecture system work, but affirmed that such contracts would be good.^[68]

5. SpaceX Tentative Calendar for Mars Missions

In 2016 SpaceX announced that there would be a number of early missions to Mars prior to the first trip of the new large composite-structure spacecraft. The early missions are planned to collect essential data to refine the design, and better select landing locations based on the availability of extraterrestrial resources such as water and building materials.^[24]

5.1. 2016 Plans

In 2016, SpaceX announced plans to fly its earliest missions to Mars using its Falcon Heavy launch vehicle prior to the completion, and first launch, of any ITS. Later missions utilizing this technology—the ITS booster and Interplanetary Spaceship with on-orbit propellant refill via ITS tanker—were to begin no earlier than 2022. At the time, the company was planning for launches of research spacecraft to Mars using Falcon Heavy launch vehicles and specialized modified Dragon spacecraft, called Red Dragon. Due to planetary alignment in the inner Solar System, Mars launches are typically limited to a window of approximately every 26 months. As announced in June 2016, the first launch was planned for Spring 2018, with an announced intent to launch again in every Mars launch window thereafter.^[24] In February 2017, however, the first launch to Mars was pushed back to 2020,^[69] and in July 2017, SpaceX announced it would not be using a propulsively-landed Red Dragon spacecraft at all for the early missions, as had been previously announced.^[70]

The tentative mission manifest from November 2016 included three Falcon Heavy missions to Mars prior to the first possible flight of an ITS to Mars in 2022:^[24]

• 2018: initial SpaceX Mars mission: the Red Dragon, a modified SpaceX Dragon 2 spacecraft launched by Falcon Heavy launch vehicle.
• 2020: second preparatory mission: at least two Dragon capsules to be injected into Mars transfer orbit via Falcon Heavy launches
• 2022: third uncrewed preparatory mission: first use of the entire ITS system to put a spacecraft on an interplanetary trajectory and carry heavy equipment to Mars, notably a local power plant.
• 2024: first crewed ITS flight to Mars according to the "optimistic" schedule Musk discussed in October 2016,^[71] with "about a dozen people".^[72]

5.2. 2017 Revisions

In February 2017, public statements were made that the first Red Dragon launch would be postponed to 2020. It was unclear at that time whether the overall sequence of Mars missions would be kept intact and simply pushed back by 26 months. In July 2017, Musk announced that development of propulsive landing for the Red Dragon lander capsule was cancelled in favor of a "much better" landing technique, as yet unrevealed, for a larger spacecraft.^[70]

A 9 m (30 ft)-diameter rocket design, using the same Raptor engine technology and carbon-fiber composite materials of the earlier ITS, was unveiled at International Astronautical Congress on September 29, 2017^[73] with the code name "BFR". It was similar to the ITS design, but smaller. Musk announced additional capabilities for the BFR, including Earth missions that could shuttle people across the planet in under an hour (most flights would be less than half an hour), Lunar missions, as well as Mars missions, that would aim to land the first humans on the planet by 2024.^[74] SpaceX now plans to focus mainly on one launch vehicle for these missions - the BFR,^[75] now given an official name of "Super Heavy". By focusing the company's efforts onto just a single launch vehicle, the cost, according to Musk, can be brought down significantly.^[30] SpaceX also plans to use the Super Heavy for Earth-orbit missions, replacing all current SpaceX Falcon launch vehicles. Construction of the first of the Super Heavy vehicles would begin in 2018, according to Musk.^[76]

5.3. Further Delays

As of 2020, none of the planned Mars missions have started yet. One of the rockets that could potentially be used for a Mars mission will be used for a Moon mission first, which according to Musk might happen in 2021.^[77] It is unknown when any of the Mars missions will commence.