The SpaceX Plan to Colonize Mars

At this week's International Astronautical Congress, SpaceX CEO Elon Musk outlined a bold and well thought out approach for the colonization of Mars based on three key principles:

1. Reusing all system components to minimize costs
2. Fueling outbound transports in orbit to maximize payload capacity
3. Enabling fuel production on Mars to eliminate the need to carry return fuel

Reusable booster rockets will carry interplanetary transport vehicles and fuel tankers into Earth orbit and return to land back at the launch site. These massive boosters, powered by 42 of SpaceX's new Raptor engines, have four times the payload capacity of the Saturn V moon rocket. Reusing these boosters not only cuts cost, but drastically reduces the time required to deliver additional payloads.

The transport vehicles will carry people and cargo back and forth between Earth and Mars, and the tankers will be used to fuel the transports in Earth orbit. This approach will allow the transports to be launched without fuel on board, maximizing the amount of people and supplies each ship can carry to Mars.

The transport ship and tanker will be based on the same fuselage design to keep costs to a minimum. Both of these ships can return to Earth using aerobraking and propulsive landing capability so they can be reused on subsequent missions, another key factor in managing costs. The transport ship will also be capable of landing on Mars and launching from there back to Earth. Since Mars' gravity is only 38% of Earth's, the transports will not require a booster rocket to return home.

In order to get back to Earth, fuel must be produced on Mars. To enable this, the Raptor engine runs on methane and oxygen, both of which can be produced on Mars using the carbon dioxide that makes up most of the atmosphere and the water ice that can be found on and under the ground. Power generated by solar panels or nuclear reactors can be used to melt the ice and split the hydrogen from the oxygen via electrolysis. Some of the oxygen can be used for rocket oxidizer, and the rest can be used for life support. The hydrogen can then be combined with the carbon dioxide in a reaction to create methane rocket fuel and water for life support.

Musk's plan is based on the (approximately) 2-year cycles of Earth-Mars orbital alignment when getting to Mars will only take 90 to 120 days. He envisions a fleet of transports that will gather in Earth orbit and all leave for Mars together at these times. This will allow large amounts or cargo and large numbers of colonists to arrive at once, increasing the odds of survival for the colonists since the loss of any one ship will have less overall impact on the mission.

All of this sounds amazing, yet what makes it plausible is that SpaceX is already a successful, fully-integrated space systems provider, and they have already developed many of the technologies required for this plan to succeed. However, there are still some major obstacles to clear:

• SpaceX will need a lot of additional cash to complete this plan. Musk was clear that he will need funding help from both the private and public sector to get the system built.
• The booster and transport/tanker vehicles are still being designed, and there are major technical challenges to be worked out along the way. For example, the design calls for composite fuel tanks to keep weight down, but it may be difficult to make this material work at this scale and with the temperatures and pressures required as Lockheed learned during their failed attempt to build the SSTO Venture Star space transport back in 2001.
• How the colonists will be housed, fed, and protected from radiation on the long journey to Mars is still being worked out. Musk believes the radiation risk is small and can be mitigated by keeping the ship pointed away from the sun during the transit, using the engine, fuel tanks, water stores, and cargo to shield the passengers.
• How the proper landing sites will be selected and prepared prior to the first colonists' arrival is still to be determined. Building enough habitat for hundreds or thousands of colonists is a large task, and making sure that fuel production and food production facilities are already in place is critical to success. If you land too far from the ice, or if one of the transports crashes on the fuel factory, the mission is doomed.
• Exactly how the colony will be sustained in terms of food, water, air, and housing is still not clear. We'll need to figure out how to build and maintain airtight and radiation-proof structures using as much local material as possible. We'll also need to learn how to grow food on Mars.
• Having a lot of people on Mars will require some form of local government. Just like on Earth, there will be disagreements, crimes, and other problems between people that will have to be dealt with. You will need police, courts, and jails.
• Since there will be men and women, there will be babies. Education facilities will be required at some point.
• What will be the basis of the colonists' economy? Will they be employees of SpaceX? Will they get (or even need) a salary? Will there be taxes? How will goods and services be equitably distributed?

Musk indicated a belief that building a self-sustaining colony on Mars would be a 40 to 100 year process, and he plans to start sending the first ships by 2018. These would initially be the smaller unmanned Dragon capsules, followed by the large colonial transports in 2023. Assuming he can get the funding, given the estimated costs and life expectancy of the various ships, he believes he can deliver people and cargo to Mars for less than $140,000 per ton. This is an amazing achievement when compared to the cost of current approaches for interplanetary travel.

Finally, we should consider the human element of this endeavor. Life on Mars will be difficult, the work will be hard, and the risk of death will be omnipresent. In many ways, the Martian colonists will be like those who left Europe for the New World in the 17th century. Many will die in shipwrecks, from work accidents, from illnesses, and other things that we don't often concern ourselves with in the developed world. On top of all that they will have to live in an enclosed habitat all the time; going outside will require a space suit. Given this, will people even want to go to Mars? If they go will they want to stay? What will be their motivation? Musk's goal of making humanity a multi-planet species is admirable, but previous colonization events have been driven by people's internal desires to find a better life for themselves and their family. Will Mars hold this kind of promise for enough people to create a viable community, or will it end up as just another lonely outpost for a few dedicated explorers and scientists? Only time will tell, and I look forward to seeing how this develops over the next few years.