The announcement in September 2024 by Elon Musk that SpaceX plans to launch a privately funded human mission to Mars as early as 2028 would seem to be nearly as ambitious as John F. Kennedy’s 1961 goal of landing a man on the Moon by the end of the decade. Especially since Musk's timeline requires that a complete Mars landing and return to Earth test mission demonstrating that a human landing would be safe must be accomplished two years from now in 2026, prior to sending astronauts to Mars in 2028. And unlike the Apollo program which had massive federal funding, as well as the resources of multiple large aerospace and industrial companies, scientific institutions, and governmental agencies including of course NASA, SpaceX appears to be doing this all on its own. While recent political events might at some point change the economic and resources equation, it's unlikely that this would happen soon enough to affect the looming 2026 deadline in an appreciable way. And yet Musk has made it clear in his statement that he believes that this timeline is possible.
Representation (by the author) of a hypothetical Starship landing leg plaque
Realistically, landing astronauts on Mars even by 2033 would be extremely challenging, not only because of the huge technical challenges which have to be overcome, but especially because of the limitation of the Earth-Mars transfer windows, which limits test flights to Mars to approximately every twenty-six months.
The SpaceX rapid iterative design process seems well suited for low Earth orbit launches, and probably also for Moon launches, because other than normal logistics (or regulatory approvals) there is nothing that prevents frequent test flights. In the case of Starship for example there have been six full stack test launches since the first flight in April 2023, with a decreasing amount of time between each test flight:
| Starship Full Stack Test Flight |
Date |
Days Between Flights |
| 1 |
4/20/2023 |
|
| 2 |
11/18/2023 |
212 days |
| 3 |
3/14/2024 |
117 days |
| 4 |
6/6/2024 |
84 days |
| 5 |
10/13/2024 |
129 days |
| 6 |
11/19/2024 |
37 days |
The amount of iteration and progress that occurred between each of these flights is too much to detail here, but it has been an impressive display of the SpaceX iterative process, especially considering the scale of Starship as the largest rocket in the world, and the scope of doing things that have never been done before, such as tower catches.
Now imagine that each of these Starship test launches had been separated by 700 days. While that seems almost unthinkable for SpaceX, the fact is that the immutable barrier of Mars launch windows creates the equivalent of a two-year FAA delay between launches to Mars, greatly slowing down the iterations between versions other than what can be tested in Earth orbit such as refueling and in-space long term cryogenic storage.
Essentially this forces SpaceX into more of a traditional waterfall method of development, at least for the Mars flights, where they will need to design and analyze and test as much as possible ahead of a flight, to increase the chances that the ships that they build and send to Mars have the highest possibility of a successful outcome, because one small problem that results in test failure will set them back over two years while waiting for the next launch window.
2026, 2028, 2031 - The Learning and Development Period
This makes a human landing even in 2033 extremely challenging, as there are only three launch windows available for testing prior to this – 2026, 2028, and 2031. During these three launch windows SpaceX would have to test sending Starships to Mars, landing them, refueling them, and returning them safely to Earth. And of course developing other capabilities such as radiation shielding, life support, etc., however those can be tested to some degree in between Mars launch windows. But several important capabilities can only be tested on actual test flights to Mars. Note that while the question is specifically about 2026, the 2033 hypothetical timeline is relevant because it contains all of the same elements that will need to be demonstrated successfully in 2026 using Musk's stated 2028 human landing goal.
2026 - Entry and Atmospheric Testing
Using what we have seen with the Starship test program so far as a template, on a 2033 timeline we could probably expect SpaceX to attempt launching several Starships to Mars in 2026 (which has in fact also been stated by Musk), perhaps each with different design variations to be tested, with the primary goal being to test the controllability of Starship in the Mars atmosphere during entry, as well as testing various thermal protection solutions to determine the type and amounts needed. Similar to the early test flights of Starship, simulated landing with no landing gear would possibly be attempted if any of the test ships made it that far, but landing tests would probably not be a priority during the first launch window.
2028 - Landing Tests
Assuming that the 2026 atmospheric test flights are successful, then in 2028 there would probably be the first actual landing attempts. Landing on Mars is a huge challenge, harder in many ways than landing on the Moon. Starship will be many times more massive than anything that has landed on Mars before. And it will be using a landing technique that has been tested on Earth, but never on Mars. And never on uneven terrain.
2031 - Refueling, Launch From Mars, Return to Earth
Assuming that the 2028 test landings are successful, then in 2031 there would probably be the first attempts at testing refueling at Mars, launch from Mars, and return to Earth. This would likely involve either ISRU fuel production, or refueling in Mars orbit. Each would have extreme challenges. Refueling in Mars orbit means that the landing ships must have enough fuel remaining to launch back into Mars orbit and rendezvous with a fuel depot. And it would likely require an extremely large number of Starships to ferry to Mars orbit the fuel needed for each returning Starship, along with the requisite number of additional Starship launches needed to fuel each of the tanker ships prior to their ferry mission to Mars. ISRU would be no less challenging, as it requires semi-autonomous robotic capability to extract water ice from the surface, which has to be delivered to an electrolysis system, with the resulting oxygen delivered to storage tanks, and the hydrogen pumped into a Sabatier reactor, with the resulting methane delivered to storage tanks. And then the oxygen and methane has to be pumped from the storage tanks into Starship’s propellant tanks prior to launch, similar to what currently happens at the Boca Chica launch site. There could be other methods used such as outputting the propellants directly into the ship's tanks, but whichever method is used the complexity level will be high.
Looking at all of the things that must be developed and tested in just three Mars transfer window launch opportunities, it could be argued that a 2033 human landing on Mars fits within the definition of “Elon time”, i.e. every development step and test has to go relatively smoothly and with no major problems that would result in requiring additional transfer windows for testing. Considering all of this I think an argument could be made that a 2033 human landing on Mars is wishful thinking.
Massively Compressed Waterfall
However instead of this approach the CEO and Chief Technology Officer of the world’s dominant space launch company has said that SpaceX plans to launch humans to Mars in 2028, which essentially means a highly compressed waterfall design process that would result in the launching of Starships in 2026 which are capable of demonstrating a complete Mars landing and return mission. This means that all of the test flight activities that I have listed above would have to be compressed into one launch window, with no opportunity to draw on experience from previous Starship Mars missions. Since it seems unlikely that any of these capabilities will be tested for the first time on a human mission, this means that during the 2026 window SpaceX will need to successfully demonstrate launch to Mars, landing, refueling, and return to Earth.
Complicating things even further is that for an extended stay mission there would not be time for the 2026 uncrewed ships to return to Earth prior to the launch of the human flights in 2028. Again assuming that a complete mission will be demonstrated prior to sending astronauts to Mars, this would seem to be physically impossible using chemical rockets. However it might be possible for a short stay mission of about thirty days, which would allow the 2026 ships to return to Earth prior to the 2028 launch window. This seems to eliminate ISRU as a potential refueling method for the 2026 missions, as it seems nearly impossible that the required methane and oxygen production volume could be completed within thirty days.
The actual likelihood of SpaceX achieving all of this by 2026 is a separate question, considering that in some ways it would be the equivalent of NASA pulling off an uncrewed Apollo lunar landing and return demonstration in 1963. And also considering that the Starship program is still currently working on accomplishing basic Starship capabilities such as its first orbital flight with payload, in-space refueling, and the recovery of the spaceship, none of which it now appears will happen until 2025. Along with what was mentioned in a previous answer, it seems clear that an Olympus Mons sized mountain of massive technical challenges would have to be climbed by SpaceX during the next twenty-four months in order for SpaceX to demonstrate a full Mars mission including return to Earth in 2026.
