In 1989 George H.W. Bush gave a speech in which he called on NASA to build and commission a space station, undertake a return to the Moon and then embark on human missions to Mars. While one may debate the real political intent behind this call - whether, in fact Bush and his Administration would sign-up to such a project were it to be presented to them - one cannot deny the subsequent turn of events.

Following the call, NASA embarked on a study of what would be required to achieve the Bush Space Exploration Initiative, and after 90 days published a report that was somewhat staggering - for all the wrong reasons. While NASA did> provide an overview for achieving the goals set-out by George H.W. Bush, it did so by setting the goals against a politically-suicidal time frame of 30 years, and at a fiscally suicidal cost of some $450 billion. Had the plan gone ahead, it would have been the single most expensive project the United States had undertaken since World War Two.

Other than the space station, the idea was comprehensively rejected by Congress.
In 2004, George W. Bush addressed NASA in the wake of the Columbia space shuttle tragedy, and commanded the agency to complete the space station, return to the Moon and then go on to Mars. Again, the real political intent behind this command is unclear, but nevertheless NASA went ahead and drew up plans for meeting Bush's requirements. And while this time the agency apparently learned one lesson from their 1989 response to George Bush Senior's call, and left out the in-depth breakdown of overall costs, they still opted to span the activities in terms of decades, with even a return to the Moon taking twice an long to achieve than it had when John F. Kennedy directed the agency to land men on the Moon "before the decade is out", back in the 1960s!

Even so, the results following NASA's response to George W. Bush's call have been more-or-less the same as the aftermath of the publication of their so-called "90-day Report" back in the 1990s: complete political indifference and a space programme that is again under review and in danger of stagnation.

Which is a shame, because following the debacle of the 1989 Space Exploration Initiative, two engineers - Robert Zubrin, founder of the Mars Society, and David Baker - both then working for Martin Marietta Space Industries, put their heads together and developed a mission proposal for getting humans to Mars in just a single decade of technology development, and at a cost not of hundreds of billions of dollars - but of <i>tens</i> of billions. They called their mission proposal <i>Mars Direct</i>, and it is as relevant and achievable today as it was back when it was first proposed in 1994.

The Hardware

At its heart, Mars Direct called for the development of three items of hardware:

A man-rated booster: Ideally, this would be capable of lifting some 40 tonnes directly to Mars, and would be developed from existing space shuttle technology. In 1994, Baker and Zubrin called their booster the "Ares", and while NASA forestalled the idea for over a decade, such a booster is now on the drawing boards, and NASA have chosen to call it the Ares V - the "V" a reminder of the mighty Saturn V rocket used to first reach the Moon, the capabilities of which the new rocket mimics.

The Earth Return Vehicle (ERV): This is a two-stage vehicle that is sent to Mars uncrewed. The upper stage of the vehicle contains living space and supplies for a crew of 4 to 6 people that would be used for the 6-month trip <i>back</i> to Earth at the end of the mission. The lower stage of the ERV contains the primary descent / ascent engines and a chemical processing plant together with a robotic tractor and small nuclear generator. The key point here is that the ERV arrives on Mars almost entirely empty of fuel. Rather than carry all the propellants it would need to reach Mars and make the return trip to Earth, it will actually manufacture the fuel it needs for the voyage home once it has arrived safely on Mars!</li>

The Habitat Unit: This is the vehicle used to launch a crew of 4 or 6 to Mars directly from the surface of the Earth. It comprises up to three decks of living and working space and functions as both a spacecraft for the trip to Mars, and as a home / laboratory for the 500 days the crew will spend exploring Mars.

Mars Direct shows that some 10 years will be required to develop and flight-test these hardware elements - none of which require the development of new or exotic technologies - which means that using this proposal, humans could be walking on the surface of Mars within the time frame NASA has set for its return to the Moon!

How It All Works

The optimum time to launch to Mars occurs once every 26 months. During this time, vehicles can be launched from Earth to Mars on what are called “minimum energy trajectories”, meaning they can get to Mars with the minimum expenditure of fuel, thus allowing us to reduce their overall mass at launch. So we start our mission to Mars during one of these periods when Mars and Earth are relatively close.

At this time, say, 2018, a single booster launches an unmanned Earth Return Vehicle to Mars, which takes 8 months to get there. When it reaches Mars, it uses a combination of its descent engines and parachutes to make a soft landing on the surface. The ERV then deploys its robot truck, which carries the nuclear generator a few hundred metres from the lander and sets it on the ground. The generator is then started up remotely, and the energy it produces is used to power the chemical production plant on the ERV. The chemical plant in turn uses carbon dioxide from the Martian atmosphere, together with 6 tonnes of hydrogen carried in the ERV’s tanks, to generate the fuel the ERV needs to return home, using a process first proven to work in 1913, called the Sabatier Reaction. In all, this process takes 10 months to generate some 112 ronnes of fuel, of which 96 will be required for the ERV's flight back to Earth - the rest can be used to fuel rover vehicles.

Then, 26 months after the first launch - long after the ERV has sent telemetry back to Earth informing mission control it is fuelled and ready to fly home - two more boosters lift off from Earth.

The first of these carries another unmanned ERV bound for Mars on a low-energy 8-month trajectory while the second booster launches a crewed habitat unit on a 6-month trip to Mars. On arrival, the Mars Habitat uses its descent engines and parachutes, together with telemetry received from the ground, to touchdown in close proximity to the ERV. Once on the ground, the crew give the waiting ERV a thorough check-out to ensure it is correctly fuelled and capable of returning them to Earth. Porividing it is, Mission Control on Earth can direct the ERV still en route to Mars to proceed to anothe landing site, where it can commence fuelling itself in anticipation of the arrival of a further crew, two years in the future.

If, for any reason, the waiting ERV is incapable of the return trip to Earth, Mission Control can direct the second vehicle to land close to the waiting crew, who can then oversee its fuelling operations during their 18-month stay on the planet, and thus ensure that, at the end of their explorations, they have a vehicle capable of carrying them back to Earth.

Thus, Mars Direct achieves four significant benefits over other human mission to Mars concepts.

• It provides a means to undertake mission to Mars directly from the surface of the Earth without needing a lot of complicated on-orbit rendezvous with the space station or complex, space-based refuelling operations or the need for complicated on-orbit space vehicle assembly
• It maximises the time a crew spends on Mars, allowing them to undertake wide-ranging scientific studies and exploration both on foot and using small rover vehicles.
• It provides the crew on Mars with a back-up option for their return to Earth (the 2nd ERV); something no other long-range space mission has ever been able to supply.
• By staggering the landing locations for each ERV across the surface of the planet, Mars Direct enables us to undertake a progressive exploration of the planet, seeking out those places where we might find life - or the evidence of past life and / or the optimal location for establishing a permanent scientific outpost on Mars.

In 2003, a joint NASA / ESA cost analysis showed that a mission concept such as Mars Direct could be developed within a 10 or 12 year time frame and at an initial cost of some $31.2 billion (£19.5 billion), with each subsequent mission costing some $5.6 billion (£3.5 billion) thereafter - that's more than ten times less than NASA's 1989 estimate of $450 billion!

Were Mars Direct to be adopted as an international programme, then the cost per participating nation would be well within reach of existing space development budgets.
The only real questions is: what can we do to encourage the likes of NASA and ESA to accept the logic of Mars Direct?

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