SpaceX begins to tackle the great challenges of a trip to Mars

Earlier this month, Mars' main "development engineer" for SpaceX, Paul Wooster, presented an update of the company's vision for reaching the red planet. In his presentation at the Humans to Mars 2019 Summit in Washington DC, Wooster said SpaceX was on track to send humans to Mars by the mid-2020s. He was probably referring to the launch opportunities for Mars in 2024 and 2026, but he also acknowledged that there was still a lot of work to be done to achieve this.

SpaceX plans to bring humans to Mars with a two-stage rocket: the Starship upper stage and a Super Heavy thruster (formerly known as the Big Falcon Rocket, or BFR). Iterative design versions of the spacecraft are being built at facilities in Boca Chica, Texas, and near Cape Canaveral, Florida. Elon Musk, founder of SpaceX, is expected to provide an update on their development at the end of June.

Wooster said SpaceX was working to "minimize the number of things we need to do to get this first mission to Mars." Part of this minimization implies a massive payload capacity. Starship, once refueled in low Earth orbit, is expected to have a capacity of over 100 tons on Mars.

This will allow SpaceX to adopt a "brute force" approach, which will greatly simplify the overall logistics of the first missions. For example, it will take more consumables instead of recycling, more equipment and spare parts and other infrastructure, Wooster said.

Of course, there are many other variables beyond the arrival on Mars that contribute to the success of the mission. Wooster echoed Musk who, in previous discussions, said the company was not so focused on other aspects of the mission, such as long-term storage of food products, collecting of resources and science to lead on Mars. "SpaceX is really a transportation company," said Wooster. SpaceX is instead looking for partners to help in these parts of the plan – it only takes building the rocket.

How to return

But these things beyond the construction of the rocket are critical. The use of in situ resources is one of the key elements to make the Mars mission more profitable. Crew members use the resources available on Mars to reduce the complexity of the mission – essentially living off the land. This was proposed for the first time in the Mars Direct plan described by Martin Marietta, as it allows for a much smaller and less expensive mission. The main benefit of making the thruster for the return trip to Earth on Mars is itself, which greatly reduces the cost of the mission.

This is an area in which SpaceX is particularly eager to find partners. "There are a lot of important aspects in producing the thruster for this vehicle," Wooster said. The company intends to do it itself if necessary, but said that SpaceX would gladly allow others to help. SpaceX is also looking for partners for critical needs such as food, habitats, science, food storage, etc. Beginning in September 2018, the company began organizing conferences to solicit advice and support in these areas.

Paul noted a particular concern about energy needs, estimated at about 1 megawatt on a 500 day stay on Mars. Nuclear power would be the preferred source for this type of energy, but NASA is currently developing only 10 kW of nuclear power, which means that further development would be needed to meet SpaceX's needs.

Solar energy is possible but would require more than 6,000 square meters of panels. The recent SpaceX launch of 60 Starlink satellites included many solar panels – enough to power the International Space Station – but that still only represented 120 kW. The Martian surface is also a difficult environment for solar panels; further from the sun, there are regular dust storms, day / night temperature cycles are important and optimal orientation could be a challenge. Nevertheless, all of these issues could potentially be overcome with the large cargo capacity of Starship.

In-orbit refueling is another important concern. Although this is frequently done with non-cryogenic fuels on the International Space Station, this has never been demonstrated on a large scale in space with supercooled rocket fuel. We had to know that it worked before launching a mission on Mars.

According to the current mission plan, a Super Heavy rocket would launch a spacecraft bound for Mars in low Earth orbit. At this point, the spacecraft would need more fuel to transport its payload to the red planet. It is estimated that five Starship launches are needed to refuel a single spacecraft bound to Mars in Low Earth Orbit, which would involve the transfer of hundreds of tons of methane and liquid oxygen. Wooster said it was one of the most challenging technology challenges that SpaceX will have to overcome.

From the water, wanted

SpaceX has defined a plan that will send at least two cargo missions to Mars at the earliest opportunity. These test missions will identify available resources on Mars and potential hazards at the landing site. As long as these missions are going well, the company plans to send two more cargo missions as well as two crewed missions to Mars.

If the conditions on Mars are not those expected by SpaceX in terms of resource availability, Mr Wooster said that SpaceX was planning to bring fuel components to Mars for the return trip, possibly in the form of an aircraft. water or pure hydrogen. The company could also return a spaceship with less than a full load of fuel. SpaceX said it could send back between 20 and 50 tons of payload from the surface of Mars to Earth with a fully powered rocket, but that it could make the return with less freight and less fuel if necessary.

You can also leave a spacecraft in orbit, which would reduce fuel consumption. Or, as Gerry Sanders of NASA's space resource utilization team said, a return could be accomplished simply by throwing extra fuel on Mars and transferring it into a single Starship rocket.

At the summit, several NASA officials seemed to be interested in the potential of Starship, but felt that the moment had not yet come to start seriously planning this potential. Humphrey "Hoppy" Price, chief engineer of NASA's Mars robotics program at the Jet Propulsion Laboratory, said NASA would wait five years for Falcon Heavy to be ready when it planned the date SpaceX had announced for the first time its availability. (It should be noted that NASA's own Space Launch System rocket was originally scheduled to be launched in 2016, but is now probably delayed until 2021). When Starship representatives are ready, NASA will be very interested.

SpaceX is also working with NASA to find a site where Starship could land safely on Mars and be refueled for a return to Earth. Refueling requires the presence of water ice, which is mainly found in high latitudes, and a high power level. If it comes from the Sun, it is easier to produce at lower latitudes. Latitude between 30 and 40 degrees satisfies both criteria frequently on Mars. For a safe landing, Starship also requires a location relatively free of rocks and steep slopes. In addition, a thicker atmosphere provided by a lower landing would allow Starship to use the atmosphere to slow down, thus simplifying the landing process.

Until now, NASA and SpaceX have identified four areas meeting their criteria for a secure mission to Mars: the Arcadia, Deuternolius, Utopia and Phlegra regions, located in the northern hemisphere. On the map, the blue and green regions have a lower altitude, which makes them better landing locations than the orange, red and white areas.

It is good that SpaceX realizes that it will take a lot of help to get to Mars. It is also positive that NASA and the academic community have begun to mobilize to help one of the most ambitious companies of our time.