Mars: A Century of Exploration

A Crewed Mission to Mars

The logistics of a crewed mission to Mars are complex to say the least. Not only must the engineering problems be addressed, but the philosophical issues pertaining to our interference with the natural evolution of another planet must also be resolved (especially if extant Martian life is discovered).

There are three categories of risk environments in such a mission:

  1. Active Space Environment. This includes the phases of launch, orbital maneuvers, and atmospheric entry (all of which occur either at Mars or the Earth). The only fatal accidents in both the U.S. and Russian manned spacecraft have occured in launch or landing. This is the highest risk phase of the mission.
  2. In-Space Environment. This segment of the mission is composed of the time spent by the crew in transit between Earth and Mars. The expected hazards are exposure to radiation and zero gravity. This is an "intermediate risk" phase of the mission.
  3. Planetary Surface Environment. This is the lowest risk segment of the mission. The astronauts will be under the influence of a gravitational field that is 1/3 that of the Earth's and will have some protection from the radiation hazards of space in the form of the Martian atmosphere and the presence of the planet itself.
With these risks considered, it would be best to minimize transit time and maximize surface operation. A description of one option is given below (although the dates given are very tentative!).

Approximately every 26 months, Mars and Earth are at their closest together. During 4 of these "launch windows," several launches will be performed - some sending supplies and some sending astronauts - to Mars.

Conventional chemical rockets will be used to launch Mars-bound spacecraft into low Earth orbit (LEO). A liquid hydrogen nuclear thermal rocket (NTR) will be used to transfer the vehicles from LEO to Mars. The NTRs use about 1/2 as much fuel as conventional chemical rockets. The technology for the NTR was developed to near-flight status in the 1960's.

In September 2007, 3 launches will be performed. The first will send a fully fueled Earth return vehicle (ERV) into Martian orbit. The ERV will return the crew to Earth and splash down like the old manned missions from the 1960's. The second launch will send to the surface of Mars an unfueled Mars ascent vehicle (MAV), a liquid oxygen/methane propellant production module, a 160 kW nuclear power module, a supply of liquid hydrogen, a utility truck and a pressurized rover. The third launch will send to the surface of Mars a surface laboratory, a second 160 kW nuclear power module, a utility truck, tools, and spare parts. The surface laboratory will contain the food supplies for the crew.

In October 2009, there will be 3 launches. The first will send a second fully fueled ERV to Martian orbit (there will be a good deal of redundance in the systems, of course). The second launch will send a second unfueled MAV, spare parts and such to the Martian surface. The third launch will be the first crewed vehicle to Mars! The travel time to Mars will be about 180 days. The crew will be at Mars for 500--600 days. The first crew will likely consist of 6 or 7 individuals with a diversity of expertise (engineering, medicine, geology, social science).

In December 2011 and March 2014, there will be 3 launches similar to the situation in 2009. This will mean 12 launches from Earth, 3 of them crewed, and a mission lasting a total of 9 years.

Once at Mars, an aerocapture manuever will be used by both arriving cargo and crew modules to enter Mars orbit. This saves both spacecraft mass and fuel. The descending modules
will then use their aeroshells to enter the Martian atmosphere and will slow for landing using either parachutes or rockets.
History will then be made as the first person sets foot on Mars.
Soon after landing, the crew will position the crew and laboratory modules next to one another and the two modules will be connected.

The pressurized surface rover will be capable of long duration surface expeditions, possibly up to weeks at a time. For shorter surface excursions in the 6 to 8 hour range, unpressurized rovers will be used by crew members wearing extravehicular activity (EVA) suits.

The astronauts will study the geology and mineralogy of the surrounding area and will search for evidence of life, either past or present. They will also look for water in the Martian soil or subsurface.
In addition, the astronauts will have leisure time so that they can appreciate the experience of being the first humans to ever walk on Mars!

At the end of their 16 to 18 month stay on the surface, the crew will climb aboard the Mars ascent vehicle (MAV) in mid 2011. The MAV is a single stage launch vehicle that is designed for the short flight from the surface to the orbiting Earth return vehicle (ERV).

The MAV will rendezvous with the orbiting (now fully fueled) ERV soon after launch. The ERV is composed of a propulsive stage, a transit module, and an Earth entry capsule (EEC). The crew will jettison the MAV while still in Martian orbit. The return trip to Earth will last 180 days. As they approach Earth, the astronauts will separate from the transit module and spent propulsive stage, both of which will continue past the Earth into deep space.
The EEC will re-enter the Earth's atmosphere, similar to the manned missions of the 1960's. The crew will use a parafoil on the EEC to steer themselves to a safe landing on Earth's surface.

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