Mars Direct

Mars Direct ^[1] is a sustained humans-to-Mars plan developed by Dr. Robert Zubrin that advocates a minimalist, live-off-the-land approach to exploring the planet Mars, allowing for maximum results with minimum investment. Using existing launch technology and making use of the Martian atmosphere to generate rocket fuel, extracting water from the Martian soil and eventually using the abundant mineral resources of the Red Planet for construction purposes, the plan drastically lowers the amount of material which must be launched from Earth to Mars, thus sidestepping the primary stumbling block to space exploration and rapidly accelerating the timetable for human exploration of the solar system.

Overview of Mission Architecture

The general outline of Mars Direct is simple. In the first year of implementation, an Earth Return Vehicle (ERV) is launched to Mars, arriving six months later. Upon landing on the surface, a rover is deployed that contains the nuclear reactors necessary to generate rocket fuel for the return trip. After 13 months, a fully-fueled ERV will be sitting on the surface of Mars.

During the next launch window, 26 months after the ERV was launched, two more craft are sent up: a second ERV and a habitat module (hab), the astronauts’ ship. This time the ERV is sent on a low-power trajectory, designed to arrive at Mars in eight months – so that it can land at the same site as the hab if the first ERV experiences any problems. Assuming that the first ERV works as planned, the second ERV is landed at a different site, thus opening up another area of Mars for exploration by the next crew.

After a year and a half on the Martian surface, the first crew returns to Earth, leaving behind the hab, the rovers associated with it and any ongoing experiments conducted there. They land on Earth six months later to a hero’s welcome, with the next ERV/hab already on course for the Red Planet. With two launches during each launch window – one ERV and one hab – more and more of Mars will be opened to human exploration. Eventually multiple habs can be sent to the same site and linked together, allowing for the beginning of a permanent human settlement on the planet Mars.

Landing area

What is the best landing site? A good answer to this question is the southern plains of Lunae Planum just north of Ophir Chasma (on the equator at 65° long W.). This places the base at an average elevation (between 6 and 7 km) and within a couple of thousand km’s of most of the scientifically interesting sites on Mars.

Advantages of This Mission

There are several advantages which include:

By creating fuel on Mars with hydrogen brought from Earth, much less mass needs to be shipped to Mars, greatly reducing launch mass (and therefore cost). This hydrogen can be shipped in the form of liquid hydrogen, or benzene. (The latter brings more hydrogen in a space storable form, but requires more complex chemistry to create the rocket fuel.)
By using a direct launch to Mars, risk is reduced since two separate launches to not have to be mated together with an orbital rendezvous. Certainly dozens or hundreds of launches are not required to build a huge space craft. This reduces expense and increases safety.
By making methane / oxygen fuel on Mars, plenty of fuel can be made for the rovers, which allow a great range in exploring interesting sites hundreds of kilometres away from the base. This greatly improves the value of the mission.
A nuclear power plant on the planet means that the mission will be energy rich, allowing high density data transmission back to Earth, and plentiful energy for science and life-support. This increases safety, and the value of the time spent on Mars.
A high energy mission can melt water out of permafrost and experiment with industrial processes, which improves the value of the mission.
The conjunction class mission, reduces the amount of radiation exposure compared to the opposition class mission (which does a swing by past Venus). 550 days on Mars rather than only 30 days. 360 days in space rather than 610 days. The opposition mission also swings past Venus, so the solar radiation will be more intense.
The conjunction class mission, increases the amount of time spent on Mars, allowing more exploration and science to be done.
A radiation storm shelter will be provided to provide safety from a massive solar flare, if the crew is unlucky enough to experience one during the mission.
The third stage booster will be kept, and attached via a long line. The habitat (hab) and the third stage will be swung around this tether to provide Mars' gravity while traveling in space, to completely avoid a weightless environment. This improves safety.
By choosing a travel time to Mars (about 6.5 months), the crew is on a 'free return' trajectory where if they choose NOT to land on Mars, they return to Earth exactly 2 years after launch. This means that the Earth will be there, when they arrive back at Earth's orbit. This increases safety, if for some reason they have to abort the landing.
The second Earth Return Vehicle (ERV) is launched on a slower trajectory, so if the crew can not land within 1,000 km of their own ERV, the second one can land beside them, with the pilot on Mars directing it down. This improves safety.
A fully fuelled ERV is waiting for the crew before they launch. This improves safety.
Enough food and supplies are brought to last the full crew for more than 26 months past their normal return time. If for some reason they can not return, they can survive long enough to allow another mission to be sent to rescue them. This improves safety.
Sandbags can be filled with soil to increase radiation protection by putting sand bags on the roof of their habitat (hab). If locally sourced water can be found, water (which is an excellent neutron absorber), can also be used. (By using local materials for radiation protection, the cost of the mission is reduced. (Tho for a 1.4 year stay on the surface, the amount of radiation is not a critical problem without this step.)

Robert Zubrin discusses the advantages of such a mission in some detail in his book, "The Case For Mars", IBSN 9-781451-68113.

Variations of this plan

There have been several variations of this plan.

NASA created a 'Mars Semi-direct' mission with 6 crew which was based on ideas of Mars direct.
Robert Zubrin created a version using Falcon Heavy boosters (for supplies) and a Falcon 9 booster (man rated) for a 2 person exploration team. ^[2]
A Moon Direct mission was proposed by Zubrin, as a lower cost way of exploring Luna. ^[3]