#18 - RW 270
Science Magazine
August 15, 2003
One Nuclear Leap to Mars?
Richard Stone
The Columbia accident may have persuaded many that human space flight is too risky, but Russian space scientists say it's time to be bold as they press ahead with plans for a voyage to the Red Planet

SEMIPALATINSK TEST SITE, KAZAKHSTAN -- In the early 1960s, Pentagon brass pored over surveillance photos with grim fascination. The Soviet Union appeared to be building an underground facility in the heart of a remote and well-guarded atomic weapons testing range in northeastern Kazakhstan, a place no spy could get near. Glimpses of giant metal spheres and high-tech equipment trucked to the site suggested a sophisticated operation. Although opinion was divided, one camp in the U.S. intelligence community concluded that it was watching a top- secret effort to build a "death ray," a particle-beam gun for shooting down American missiles.

After the Cold War ended, Western officials learned the truth, which turned out to be even more far-fetched than the fabled death ray: The Soviets were attempting to build a nuclear engine to propel cosmonauts to Mars. But the Soviet dream, to trump America's moon landing, died along with the Eastern Bloc.

More than a decade later, Russia is fanning the embers. At a meeting in June in Moscow, Russian space scientists unveiled preliminary plans to transport people to Mars, including the likeliest propulsion systems for getting there and measures to protect astronauts from overexposure to cosmic rays and the ill effects of microgravity during a 2-year journey to the Red Planet and back.

The timing wasn't exactly propitious. The loss of the space shuttle Columbia had already raised questions about the value of human space flight and focused attention on the ballooning costs of the current space megaproject, the international space station (ISS). And Russia's chronic problems in coming up with its contributions to the ISS don't augur well for an even more ambitious encore. Nevertheless, experts at all of Russia's major space institutes and rocket-design centers are involved in the planning for a crewed Mars mission, and they have even penciled in a tentative launch date: 8 May 2018. "Our next project will certainly be the Mars mission," predicts people-on-Mars paladin Leonid Gorshkov of Energia, the Moscow-based maker of many of Russia's crewed spacecraft and the Mir space station. "We've progressed quite a long way in the planning."

Gorshkov and his Russian colleagues claim that such a mission could be pulled off for anywhere from $14 billion to $20 billion. But many Western experts think that's pure fantasy. They peg the adventure nearer to the ISS's $100 billion price tag. Even if the Russian space community could get to Mars on a shoestring, it knows it can't go it alone. "We need to consolidate all the forces in space research," says Anatoly Koroteev, director of the Russian Aviation and Space Agency's Keldysh Research Center in Moscow.

One enthusiast, astrogeologist James Rice of Arizona State University in Tempe, says "there are no insurmountable technical showstoppers to sending astronauts to Mars." The chief scientific rationale is that astronauts trained in field geology would be able to roam the surface of Mars, hunting for clues to whether the planet harbors life and undertaking other survey work that crewless landers and sample-return missions could not accomplish. "Mars is a geological wonderland," says Ruslan Kuzmin of the Institute of Geochemistry and Analytical Chemistry in Moscow.

But there are plenty of challenges, the biggest of which may be convincing the public and legislators that a human voyage is worth the cost and the risk. Many scientists just don't see the urgency. "Don't get me wrong, I would be at the front of the queue to go on a manned mission to Mars," says Martin Sweeting, director of the Surrey Space Centre in the U.K. "However, we do not need to incur the enormous additional expense of a manned flight to Mars just yet when unmanned exploratory robots can be sent at a tiny fraction of the cost to do the essential exploration--and then humans can follow 50 to 100 years later when we have more capable technologies."

Still, Russia's concerted efforts to plan one of the grandest scientific adventures of all time have prompted other countries to take a serious look at what it would take to pull it off. "For the first time, Europe is analyzing a possible scenario for human exploration of Mars," says Franco Ongaro, head of advanced concepts and studies at the European Space Agency (ESA), which envisions a launch no earlier than 2025.

NASA also is eager to lay the technical groundwork, if not test the political waters. John Mankins, acting assistant associate administrator for advanced systems at NASA, argues that the mission will be feasible only after scientists develop the "right tools" to achieve a deeper understanding of the physiological effects of long-duration space flight and of the martian environment itself. "We believe these are challenges that can be met," he says, "but it will take a lot of work to get there."

Back to the future

Out on the arid Kazakh steppe, it's easy to see why this facility, known as Baikal-1, gave Cold Warriors the shivers. From the outside it's inscrutable: Entry is through a plain white wooden door set in an artificial knoll. Inside a murky foyer, a soldier toting a Kalashnikov guards a meter-thick, 10-ton steel blast door. Stepping through this portal is like falling down the rabbit hole in Alice in Wonderland into a warren of control rooms and offices linked by brightly lit, lime-green tunnels. The longest tunnel of all, its walls seeming to converge into the distance, separates the nuclear beast from its human masters. Shoes squeak as white-coated scientists walk this linoleum-floored green mile to the cavernous halls housing Baikal's exotic reactors.

In the late 1950s, the Soviet Union and the United States launched military programs to develop nuclear reactors for lifting rockets into space and propelling spacecraft on exploratory missions. Mars was an obvious target--particularly for the Soviet Union, where the Red Planet had long been a source of fascination. Alexei Tolstoi's popular 1923 novel Aelita described a Soviet expedition to establish a communist colony on Mars, and "Forward to Mars!" was a popular slogan at the time. "Such an expedition seemed very real back then," says Gorshkov.

A nuclear engine was thought necessary because of the amount of energy needed to get a long-haul spacecraft out of near-Earth orbit, then out of martian orbit for the return trip. In 1959, Sergei Korolev, founder of the Soviet space program, pulled together top experts to start laying plans for a human Mars mission. The task force quickly grasped that the mission would need a stupendous rocket to lift an interplanetary spacecraft, dubbed the TMK, into low-Earth orbit. Designers drafted plans for the N-1, a 123-meter-tall nuclear rocket that would do the job.

During the 1960s moon race, the superpowers forged ahead with fission engine programs and other nuclear technologies. Soviet hopes to land on the moon faded after three successive failed launches of a redesigned N-1. "The whole enterprise was too expensive for our country even in those times," says Mars expert Vasily Moroz of the Space Research Institute in Moscow. After Apollo 11, the Soviet Union redoubled its efforts toward a Mars mission. The TMK was shelved after it became apparent that a more logical approach was to assemble a Mars spacecraft in orbit, à la Mir. According to current Russian plans, such a ship, once assembled, could weigh as much as 600 tons, or about six payloads of Energia's current heavy-lift rocket.

The amount of thrust necessary to get to Mars and back called for a revolutionary new engine design, and Baikal-1 was built to develop it. "It was anticipated to be highly dangerous work," says the facility's chief engineer, Aleksander Kolbaenkov. The effort involved testing new forms of nuclear fuel, such as carbides of plutonium and uranium, which could generate extremely high temperatures and deliver maximum power. "The fuel included many technical innovations," says Oleg Pivovarov, director of the Institute of Atomic Energy of Kazakhstan's National Nuclear Center, which runs Baikal. The exotic materials and an explosive coolant, liquid hydrogen, were a perilous combination. Whenever the reactor was fired up, "nobody was allowed to be on site," says Kolbaenkov. The risky work paid off, and in 1978 the team began testing an engine prototype called IRGIT.

The rival U.S. nuclear engine program never got as far. But as the Cold War wound down, NASA, the U.S. Department of Defense, and the U.S. Department of Energy tried to move the technology forward with a decade-long, $500 million program to develop a multimegawatt reactor. After critical internal reviews, the program was killed in 1993--before a reactor was even tested--in part to funnel cash to the shuttle program.

In 1987 the last Soviet leader, Mikhail Gorbachev, pitched the idea of joining forces on a Mars mission to U.S. President Ronald Reagan. Unfortunately, says Gorshkov, who helped brief Gorbachev, "Reagan showed no interest in this problem." Since 1992, Baikal-1 has had virtually no funding to fine-tune IRGIT. "These tests were never completed because of the Soviet collapse," Kolbaenkov says.

On a uranium wing and a prayer

While the Baikal team is itching to rev its nuclear engines again, currently it is NASA that is spearheading the resurrection. Researchers at the agency's Marshall Space Flight Center in Huntsville, Alabama, working closely with Los Alamos National Laboratory in New Mexico, are carrying out a project called the Safe Affordable Fission Engine (SAFE) to test the components of a 400-kilowatt uranium engine. As one of the R&D jewels of NASA's new Prometheus program for solar system exploration (Science, 28 March, p. http://www.sciencemag.org/cgi/content/short/299/5615/1969>1969), SAFE aims to develop fission engines for a variety of long-haul missions to any point in the solar system, from robotic sample returns to human voyages. NASA and its partners are proceeding cautiously. SAFE is like "the DC-9, being a first step toward developing modern, high-performance jets," says project scientist Michael Houts, a nuclear engineer at Marshall.

To get astronauts to Mars, however, the SAFE team would have to scale up to a much more powerful reactor, one generating at least 10 megawatts. Houts thinks that such a reactor could be commissioned by 2020; the Russians and the Kazakhs hope to soon switch into overdrive to get IRGIT or a successor ready as an option for a 2018 launch.

Even the most zealous nuclear enthusiasts realize that the idea of astronauts straddling a nuclear reactor for 2 years may not be the most salable option. Fresh uranium fuel is weakly radioactive, so an accident on launch would disperse little fallout. But as the uranium fissions, radioactive daughter isotopes such as cesium-137 and strontium-90 will accumulate and pose a risk. Houts points out, however, that even a modestly shielded core after shutdown would expose astronauts to radiation doses that are similar to what they would already be receiving from cosmic rays.

Still, the psychological "Chornobyl effect" has researchers casting for alternatives in case nuclear propulsion proves unpalatable. One option that Russian scientists have been pushing since 1988 is thin-film solar arrays, advanced versions of conventional photovoltaic cells that were tested on Mir 5 years ago. The amorphous silicon arrays, just 20 micrometers thick, could deliver 15 megawatts for electrical rocket engines that have a proven track record in orbit. More futuristic approaches range from antimatter engines--a NASA favorite--to extremely powerful lasers, to be based on Earth, the moon, and Mars, that would nudge spacecraft along.

A perilous voyage

Finding the right technology to get to Mars is one thing. Getting there safely is quite another. There are two paramount safety concerns: how to prevent cosmic rays from frying the astronauts' DNA and how to prevent their muscles, bones, and cardiovascular systems from deteriorating.

For the most part, the radiation threat is predictable. The longer people are in space, the more cosmic rays they are exposed to and the more their DNA is corrupted and the greater their odds are of developing cancer. Tackling this issue is, in part, a straightforward engineering problem: ensuring that the spacecraft's walls are clad with adequate shielding to block the brunt of the cosmic rays and energized particles from the sun impinging on the ship. Another element is to plan a voyage when solar activity is ebbing, reducing the threat from solar flares and coronal mass ejections. That has some Russian planners eyeing the May 2018 launch. "We can't miss this favorable opportunity," pleads Vitaly Semyonov, the chief planner of a crewed Mars mission at the Keldysh Research Center, who notes that the next auspicious launch window, taking into account both the solar cycle and the proximity of the orbit of Earth and Mars, would be 2032.

But space medical experts are also worried about a less understood effect of cosmic rays: light flashes apparently triggered when certain types of charged particles, such as helium nuclei, sizzle cells in the retina. Apollo 11 astronauts were the first to report seeing the sporadic flashes. "They were often reported after the astronauts closed their eyes and before drifting off to sleep," says physicist Alexander Popov of the Moscow Engineering Physics Institute. Popov, who is part of a team that studied light flashes extensively in the Mir cosmonauts, says he worries about the potential cumulative effects over a longer-duration mission. The big unknown: whether 2 years of such flashes would degrade vision or otherwise damage the central nervous system.

Just as serious is the spell that microgravity puts on the body. It doesn't take long for the effects of weightlessness to take hold. After only 12 days in orbit on Soyuz-18, cosmonauts "could do nothing" when they returned to Earth, says Adilia Kotovskaya of the Institute for Biomedical Problems (IBMP). "They said their legs were like fins." With some 500 people venturing into space over 4 decades, says IBMP Director Anatoly Grigoriev, spacefaring nations have devised sufficient measures to keep muscles toned, such as having astronauts work out on treadmills or fancy stationary bicycles called ergometers.

But experts don't yet know how to prevent the erosion of cardiovascular fitness and bone tissue. "These are the most critical issues for long-duration space flight," says Kotovskaya. Adds Grigoriev, "We still don't understand why the body can't synthesize bone tissue in space." And although a spell on the space station can be followed by some Earth-bound rest and relaxation to rebuild bone mass, travelers to Mars need to be fit when they arrive. Russian planners are considering shock tactics. "We must create artificial gravity to prevent them from adapting to weightlessness," says Kotovskaya. During the long flight, astronauts would take turns spinning in a centrifuge that would accelerate their bodies up to 8g. Kotovskaya's team is conducting ground-based tests of a short-arm centrifuge.

Besides keeping prospective martianauts physically fit, planners will have to prevent psychological meltdowns as well. ESA is going to probe this issue by observing the 16 or so hardy individuals who spend the long, dark winter at Europe's new inland Antarctic research station, Concordia. "As one of the most isolated places on Earth, Concordia will replicate aspects of a mission to Mars," says ESA's Oliver Angerer, manager of a research program expected to begin in 2006. Like on a long space voyage, "it would be simply impossible to mount an emergency rescue at Concordia" for 9 months of the year, he notes. The station will also be a test bed for medical-monitoring and water-recycling technologies for a human mission.

Russia has a similar endurance test in mind. IBMP plans to confine six cosmonauts for 500 days beginning next year in three space station modules on the institute grounds. To assess whether cultural differences might amplify any frictions, researchers may invite foreign astronauts to take part. "One of the biggest challenges [of a Mars mission] will be sociological," says someone with experience, former Mir cosmonaut Sergey Avdeev.

Seeing red

Although ESA and NASA experts generally agree that Russia's aim for a crewed Mars mission before 2020 is technically feasible, they are not in such a hurry. ESA is setting its sights first on getting to the moon. "We think the moon will be a very important intermediate step," says Ongaro, who says ESA hopes to team up with partners on a crewed moon mission between 2020 and 2025. As a run-up to a crewed Mars adventure, ESA hopes to mount a series of sample-return missions to Mars between 2011 and 2017. "If we can't bring back a few rocks, then we shouldn't send people," says Ongaro. ESA is eyeing 2033 as "the best opportunity," he says, for a crewed mission. Some Russian experts acknowledge that's a more realistic timetable. "My feeling is that the world is still not ready" for the mission, says the Space Research Institute's Moroz.

NASA's aspirations are more nebulous. In the wake of the Columbia disaster, the agency is undergoing an internal review of its priorities. In human space exploration, the completion and operation of the ISS is expected to be affirmed as the agency's top priority. But laying the groundwork for Mars could become a more visible part of the ISS's raison d'être. "We should see the space station as a step along the way," says Ongaro.

Russia, meanwhile, will continue to push the early launch. "Up until now we're on schedule" for 2018, says Semyonov, thanks to crucial funding from the International Science and Technology Center, a Moscow-based organization that supports nonproliferation projects and has paid the lion's share of Russia's mission planning. But the Russian government has been hard pressed to come up with meager financial contributions to the ISS; a Mars mission would be a much bigger investment. "One doesn't see Russia coming up with those funds in the near future," Ongaro says.

But political imperatives can change rapidly. Perhaps one of the spacecraft now on the way to the Red Planet will discover something "compelling or bizarre that would shake people into thinking, 'We need to go now,' " says Rice of Arizona State. Or perhaps governments will conclude that Mars should be terraformed to serve as a kind of Noah's Ark for the human race in the event of a cataclysmic asteroid strike, says Moroz. If so, the Russian planners are practically halfway there.

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