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Mars Direct illustration
Mars Direct has emerged as the leading architecture for human missions to Mars. However, that doesn’t mean that there’s no room for improvement. (credit: Mars Society)

Some thoughts on Mars Direct

If one or more nations decide to go to Mars within our lifetime, I believe that they will use Robert Zubrin’s Mars Direct plan as the blueprint for the mission. His plan provides a realistic scenario for sending a crew to Mars for an investment of time and money similar to what was spent on the Apollo program. The Case for Mars, first published in 1996, explains this plan in detail.

A lot has changed over the last few years though. China has become the third nation to develop an independent manned space program. Several privately financed groups are getting close to performing suborbital launches to win the X Prize. The International Space Station has been built (partially) and maintained successfully for several years by a group of different space agencies. Perhaps most importantly, NASA has started to look for a new direction after the loss of the shuttle Columbia.

At the end of October, Robert Zubrin had the chance to present his Mars Direct plan to the Senate Commerce Committee as part of their hearings on the future of the US space program. The plan was well received and seemed to resonate with the desire to craft a new destination-driven policy for NASA that will take us beyond Earth orbit again. Mars is the obvious compelling destination and Mars Direct is the obvious choice for how to get us there.

Mars is the obvious compelling destination and Mars Direct is the obvious choice for how to get us there.

If there is a chance that Mars Direct might be used as the roadmap for the United States’ plans for future space exploration, we should take a closer look at some of the details and see what changes might need to be made based on recent events. When evaluating the specifics of the plan, the key point should be to determine what is the best available option that will satisfy a given requirement in the most efficient way possible. Considering this, what would some of the possible changes be in an updated plan?

Consider the multinational approach

The plan offers three suggestions for how a manned mission could be funded: an Apollo style mission financed by a single country, a multinational effort where the costs are spread among a number of participants, and a prize-based system that would encourage private companies to fulfill the mission. At the time the book was written, the Apollo type of mission was the only one that had been successfully accomplished. The construction of the International Space Station had not started and there were good reasons to believe then that it might never get built. The X Prize has still not been claimed by a private company, but it looks like it’s only a matter of time.

Although the space station is not completed yet, the last several years have shown how multiple agencies can work together successfully on a very complicated mission. Our experience with the station has also given us an example of the dangers involved in a “go it alone” approach. If the United States had built the station on its own, as was originally intended, the station would have been left empty after the Columbia disaster and, like Skylab, might have fallen out of orbit if shuttle service was unable to resume in time to boost the station’s altitude.

Fortunately, our international partners are currently able to provide alternate access to orbit that has allowed crews to continue occupying the station after the loss of the shuttle. On a manned mission to Mars, Russia, Europe, Japan, China or any of the other countries that might take part in the mission would be able to help in similar ways. Beyond simply sharing the expense, other agencies can save time and money by offering existing services that are required in the plan that would otherwise need to be developed specifically for the mission.

What about the other two options? Although extremely successful, the Apollo program was born out of a unique period of world history. Without a motivating force similar to the Cold War it would seem impossible today to get the same amount of political will to spend the time and money required for a mission to Mars. It also seems that the prize based approach is not quite ready for this mission—private companies need to be able to put people in orbit before being able to send them to Mars. Working with our international partners might not just be our best option, but our only option for a manned mission.

Reconsider the cargo-only space shuttle

The main launch vehicle originally envisioned for the Mars Direct plan is a cargo-only variant of the space shuttle. Different variations are referred to as Shuttle C, Shuttle Z or Ares. The idea behind this concept is to evolve the existing shuttle system into a heavy-lift launch vehicle that is approximately as powerful as the Saturn 5. This option would be better than creating an entirely new heavy lift launcher from scratch if there were no other heavy lift launchers available, but there are.

Working with our international partners might not just be our best option, but our only option for a manned mission.

As part of the Air Force’s Evolved Expendable Launch Vehicle (EELV) program, the Delta 4 and Atlas 5 launchers have come into service. Boeing and Lockheed Martin also have plans for heavy-lift versions of both vehicles. The European Space Agency also has it’s own heavy-lift launcher with the Ariane 5. Russia has also developed a launcher that could be used for the task—the Energia was used to carry their own space shuttle into orbit and is comparable in power to the Saturn V. Although the Energia is now defunct, it’s possible that the Russians could revive this program as their contribution to the mission.

It is likely that a shuttle derived heavy lift launcher is the best option for a manned Mars mission, but if an existing launcher fills the role or would fill the role if upgraded then both time and money can be saved. Why reinvent the wheel and create a new vehicle if we don’t have to?

One other interesting possibility for launching the mission presents itself if we consider taking a multinational approach. Because of their distance from the equator, both the American spaceport in Florida and the Russian spaceport in Kazakhstan are unable to take full advantage of the extra boost the Earth’s rotation gives to launches. It’s more efficient to launch closer to the equator, so the European Space Agency’s facilities in French Guiana, located only a few degrees north of the equator, could be the ideal spot for the beginning of the mission to Mars.

page 2: reconsider the direct to Mars approach >>