The Rocky Road to Mars
The American Legion Magazine
January 2001
pp. 16-20

Thirty years ago, the Apollo program made getting to the Moon look so easy, that it was easy to imagine that the whole Solar System lay open for human voyages. The most popular science fiction movie in 1969, when Apollo-11 landed, was “2001: A Space Odyssey”, which portrayed moon bases and a manned mission to Jupiter . And it all looked so inevitable.

Well, it’s now 2001, and where’s the odyssey? Where’s the moon base, and where are the manned interplanetary spaceships?

It’s easy to blame budget constraints, or changes in national priorities. It’s easy -- and at least a little bit justified -- to blame leadership failures, both in the White House and at NASA and within American popular culture. But space experts also point to a long list of technical and scientific problems that still need to be solved. The Apollo program was able to short-cut or avoid these problems, but a far-ranging long-term human exploration beyond Earth orbit cannot.

The problems involve technical issues such as propulsion and equipment reliability. They also involve medical issues, both physical and psychological. And they even involve political and diplomatic challenges, as exemplified today by the agonizing struggle to construct a truly international space station.

In NASA’s continuing public relations campaign to find justifications for the $80 billion space station, research for deep-space exploration is one of the favorite refrains. “We’re going to have some more problems,” NASA Administrator Dan Goldin warned last July. “[But] the space station will be built, and then we are going to figure out how people will live and work in space, and we are going to get to Mars.”

Dr. Louis Friedman, president of the privately-funded “Planetary Society“, agrees: “A recent national poll further confirmed public interest and support for human Mars exploration,” he wrote recently. Although NASA has no official program to achieve this, he continued, “the public understands that this is where the space exploration program is heading. In fact, it is my belief, based on extensive interaction with the public, that people generally assume we are preparing to send humans to Mars.”

NASA’s “Strategic Objectives” report, just revised, makes no secret of several goals that are directly applicable to flight to Mars. NASA, the report promises, will “conduct engineering and human health research on the International Space Station to enable exploration beyond Earth orbit.” Furthermore, it promises to “invest in the development of high-leverage technologies to enable safe, effective, and affordable human/robotic exploration” while defining “innovative human exploration missions”.

For humans to get to Mars and back, they first have to survive the journey. Even after forty years of manned flights into space, some lasting a year or more, that fundamental question remains unsolved.

Space biologist Keith Cowing, who now runs the private “NASA WATCH“ internet site, is still cautious about the medical unknowns: “Despite nearly 100 shuttle missions, years of extended stays on Mir, and trips to the Moon, we still do not have all the answers when it comes to sending humans to Mars - safely,” he writes. “While the problems are not insurmountable, they will have to be thoroughly addressed - by both doctors and engineers - before humans can travel to - and work safely upon - Mars.”

According to NASA astronaut John Grunsfeld, the Mars crew "needs to be in the best shape of their lives" upon arrival. But given the current state of knowledge, humans arriving on Mars would be in the same bad condition as humans returning to Earth from Mir -- weak, disoriented, and fatigued both physically and mentally. Not having a Mars crew in tip top condition would place landing activities and any post landing surface activities at risk.

On long flights, astronauts experience bone loss, which while similar in some ways to osteoporosis observed on Earth, doesn’t respond to the same drugs that help earthside sufferers. There’s also a marked decrease in muscle mass - including cardiac muscle - although this is more or less reversed after return to Earth. And cosmic rays in deep space can gradually erode the brain’s neurons and the optic nerves in an astronaut’s eyes, perhaps accumulating detectable damage.

The problem is the distance and the time involved in getting to Mars. Spacecraft reach the Moon in three days, but need eight to ten months to reach Mars. They must then wait more than a year before the planets line up properly for an equally lengthy return leg. Total time in space: more than three years.

One solution, still being considered, is creating pseudo-gravity during the coasting phases, by swinging the spacecraft at one end of a mile-long tether, with a rocket stage at the other end. The only other solution, if drifting for years in zero-gravity is too dangerous for health, is to get to Mars as fast as possible, with trip times measured in weeks, not months.

This is where advanced propulsion comes in. NASA has actually spent a lot of effort over the last thirty years examining and testing designs for more efficient deep-space rockets. But it is still far from actually picking a design and building it.

One classic system with strong support is the “nuclear thermal rocket”, or NTR design. It uses the heat from a nuclear reactor to expand and expel hydrogen gas and thus propel the rocket. A space strategy study team in 1991 called it “the only prudent propulsion system for Mars transit.” Now being designed at NASA’s Glenn Research Center in Ohio, it is a smaller, more efficient version of the “NERVA” engines built and then scrapped during the Apollo program.

Another concept getting publicity recently is a variation of the old classic, “ion drive”. Here, the propellant is electrically-charged ‘plasma’ (atoms stripped of their electrons) that is expelled by magnetic forces generated by powerful electrical currents. The latest design adds the ability to “change gears” in the efficiency of the engine, depending on whether one needs higher thrust during initial climb from Earth orbit (“first gear”) or greatest efficiency during interplanetary cruise (“sort of an “overdrive” gear).

Franklin Chang-Diaz, a physicist who became a NASA astronaut twenty years ago, has been championing this concept for at least that long. Test hardware for a prototype -- called the VASIMIR, for “Variable Specific Impulse Magneto-Plasma Rocket” -- has been built by NASA, and in-space tests of a small-scale engine could occur within a few years. A full-scale version would need a power plant (either a nuclear reactor or a giant solar battery array) big enough to serve a medium-sized town.

Another little-appreciated Mars challenge is in building hardware that can function faultlessly for years in space, or for months on the Martian surface, with minimal maintenance and replacement parts. For the space shuttle flights, every day in space usually means weeks of ground servicing. On space stations, massive amounts of time -- 50 to 80% or sometimes more -- needs to be devoted to in-flight maintenance and repair.

Even the famous Apollo lunar spacesuits from the 1960s were barely able to function for three days on the Moon, the longest period on the surface. After ten or twenty hours of use, exposed to abrasive lunar dust, their joints were jamming, their air seals were leaking, their electrical circuits were sputtering. On Russian space stations, spacesuits are certified for ten four-hour spacewalks before needing a massive overhaul that often takes a week of work by the cosmonauts.

The space suits to be used on Mars will face the worst of all these environments -- abrasive dust AND literally hundreds of day-long space walks per suit. Furthermore, the Apollo suit was physically bearable only because of the Moon’s weak gravity. On Mars, the suit would have weighed twice as much and been impossible to wear for more than an hour or two at a time. NASA thus needs spacesuits that are lighter, more efficient, more durable, and more serviceable than any they’ve ever built before.

The actual operating conditions on Mars need to be far more precisely measured. For example, the effects of wind-blown Martian dust on hardware is of great concern. "Fine particles are blowing at speeds up to 200 mph,” a NASA engineer told a conference in Colorado in 1998, “and that will cause electrostatic charging, but we don't know how much."

The dust will clog chemical recycling canisters, stick to windows and photovoltaic arrays, and abrade moving parts. Once inside the astronauts’ habitat, it will get over everything, but nobody knows if it’s toxic, or flammable.

Engineers can’t design their equipment until they actually measure the dust, and plans to perform simple experiments on robot Mars landers have been cancelled in the wake of the 1999 unmanned Mars probe disasters. It will probably take another ten years now before that kind of critical design information is available.

Another feature of the Martian environment must be tested in order to take advantage of it: local resources. Unlike the airless, bone-dry Moon, Mars has a small atmosphere and accessible water.

These materials could be processed into drinking water, breathing air, and even fuel for rockets and ground vehicles. But prototypes of the hardware for such processes must be tested during robot missions to Mars, in actual conditions, before entrusting astronauts’ lives to their reliability. These plans, too, have been indefinitely shelved following the recent setbacks.

An interesting pattern emerges concerning the fundamental nature of the technologies for Mars exploration. Unlike for Apollo and the Moon, where it was hardware that was most challenging -- the rockets, the navigation, the crew control systems, and even the rocks that were the mission's goals -- for Mars the underlying unifying theme is connected to life sciences.

This Martian theme ranges from the microscopic (the nano-fossils that may signify past life on Mars and will be the prime objective for search), to the medical (human physical survival under flight conditions remains uncertain), to the social (the proper mix of crew skills, and the proper crew organization for multi-year missions beyond the range of radio conversations, remain unknown), to the political and diplomatic (the mustering of national perseverance and international cooperation needed for such a long-term project), to the interplanetary (protective quarantine standards are prudent), to the ecological (visionary hand-waving about 'terraforming' the entire planet in a century or two). Only a few of these themes were at all significant during the 1960s moon landings, but every one of them is critical to a successful human mission to Mars.

And that may be the key that will unlock the door of a future government commitment to such a project. Such life-science-related themes are not merely critical to designed a workable Mars mission. They are crucial to human civilization right back home on Earth.

Advocates believe that the technological lessons that a Mars mission will force us to learn could result in the same sort of industrial invigoration that the Apollo challenges fuelled thirty years ago. If designed properly, this bold project could accelerate innovative research aimed at terrestrial problems.

Louis Friedman, president of the Planetary Society, looks even further ahead in his call for preparing for human interplanetary flights: “For both these great objectives -- the search for life beyond Earth and the quest for humans to evolve into a multi-planet species -- the action is at Mars. NASA may not need more money for Mars exploration -- but humanity does. It is part of our finding our place in the cosmos.”