Astronaut Tom Jones - speaker, author, consultant - four Space Shuttle Missions, three space walks at the International Space Station, author of Sky Walking: An Astronaut's Memoir

The Next Giant Leap

For nine years, former NASA administrator Dan Goldin enthusiastically endorsed the idea of sending humans to Mars, but couldn't deliver either a mandate or funding for human exploration beyond Low Earth Orbit (LEO). His successor, Sean O'Keefe, confronted with a straightjacketed budget, has studiously avoided discussing the "Where Next" topic, too. I came face-to-face with NASA's ongoing struggle with "the vision thing" a year ago, just thirty minutes before suiting up for my launch to the Space Station aboard Atlantis. In the Cape crew quarters, chief of human spaceflight Joe Rothenberg told me flatly that he saw little chance that astronauts would rocket out of Earth orbit for at least the next ten to fifteen years.

I was shocked. About to strap on a rocket and head for the Space Station, my boss had just told me that NASA was essentially marking time. Wasn't it his job - and the Administrator's -- to develop the public and leadership support for stepping beyond LEO? What I saw was that NASA was intent on not rocking the boat; rather than propose bold new initiatives, it would wait for direction from the top. With the President and nation now preoccupied with an open-ended war, and budget surpluses proving ephemeral, we need a practical, affordable near-term exploration goal that can muster administration, congressional, and public support. Thirty years after the last lunar landing, what objective can blast us out of Earth orbit again?

The answer came into focus for me on Feb. 12, 2001, during my second spacewalk outside the Space Station. Falling around the planet at five miles per second, my space-suited hand gripping a golden handrail on ISS's Destiny module, I had one of those moments that crystallize in space and time to become an indelible memory. The event that grabbed my attention was happening almost 200 million miles away, where the asteroid probe NEAR Shoemaker was making history.

As Bob Curbeam and I worked on outfitting Destiny's exterior, mission controllers eased NEAR Shoemaker toward the surface of asteroid 433 Eros. The little spacecraft had rendezvoused with Eros a year earlier. Now it was ending its mission with a spectacular gamble -- a landing on one of the oldest objects in the solar system.

Beamer and I had just uncovered the Destiny's new research window when our radios crackled with the astounding news that NEAR Shoemaker had bounced down on Eros' dusty terrain -- and survived! In my space suit, sweaty with exertion, I was nevertheless hit by a shiver of excitement, imagining what it would be like to be EVA, not in Earth orbit, but a million miles away, drifting over the rubble-strewn surface of a near-Earth asteroid (NEA). Today I believe these intriguing objects are the perfect stepping stones to Mars. Unlike that distant goal, however, or a return to the Moon, Near-Earth Asteroids can get us back in the business of exploring terra incognita in a way that's doable, affordable, and that advances us toward the eventual exploration of Mars and the Moon.

What makes NEA's especially attractive now is the convergence of our capability with their accessibility. Over the past ten years, astronomers have discovered hundreds of new NEA's, some in orbits that are easily reachable, with only modest improvements in human spaceflight technology. Here are five key reasons why these mountain-sized objects should be our next exploration objective:

Near-Earth Asteroids are easier to get to from LEO than the Moon.

Figuratively speaking, they're just off the next exit down the cosmic interstate. We can make a relatively short round-trip to NEA's in Earth-like orbits for very reasonable amounts of rocket power. Already we know of a handful of NEA's that can be reached on round trips lasting six months to a year -- for a velocity change, or V, no greater than that required for a round-trip from LEO to the lunar surface (about 9.4 km/sec). But the flight times are shrinking steadily. Last year, Leon Gefert of NASA's Glenn Research Center found that a round trip to 1991 VG, a small NEA only tens of meters across, would take as little as 60 days (including a 30-day stay at the asteroid). The total V would be just 6.1 km/sec, and just 4.9 km/sec if we stretch the trip out to 90 days. We expect hundreds of similar objects are out there, just waiting to be discovered.

These "weekend getaways" minimize exposure to micro-g, cosmic radiation and solar flare hazards (and are shorter than current ISS expeditions). And since the astronauts on such a mission never get farther from home than about a million miles, they can deal with a severe systems failure by executing an abort directly back to Earth.

Asteroids offer a rich and untapped store of knowledge about the early solar system.

Unlike the rocks on the Moon or Mars, these splintered fragments from the main asteroid belt (between Mars and Jupiter) represent ancient, well-preserved material from the age of planet formation. An array of asteroid samples - chosen intelligently by field explorers - would tell us how this original stuff from the solar nebula coalesced into the zoo of protoplanets that gave rise to Earth and its rocky neighbors. The resulting science bonanza would dwarf the return from robotic explorers in both quantity and quality.

Resources from NEA's can help us reduce the cost of future space exploration.

These same ancient materials represent a rich trove of natural resources that can replace some of the bulk supplies we bring - at horrendous expense - up from Earth. The shuttle hauls supplies to the Station, for example, at a staggering $10,000 a pound, with water and propellant making up much of each shipment. But some NEA's, like their parent bodies in the main belt, are composed of clay minerals that contain up to 10% water. This easily liberated hydrogen and oxygen could eventually satisfy our needs for rocket fuel and life support fluids, and none of it will have to be dragged laboriously out of a gravity field.

Asteroid exploration serves as a practical hedge against the impact threat.

In January 2001, asteroid 2001 YB5, some 300 m across, swung within 600,000 km of Earth, less than twice the distance to the Moon. The impact of this stadium-sized boulder would have devastated a region stretching from New York to Virginia. Geologists exploring a few NEA's could develop the asteroid structural data needed to devise a practical diversion scheme, an added payoff from our next venture out from LEO.

Sending astronauts to Near-Earth Asteroids gets us moving towards Mars.

From my spacefarer's perspective, the most attractive idea about "astronauts to asteroids" is that all of the development costs are directly applicable to an eventual Mars mission. The spacecraft will have to do nearly everything required to go to Mars, save for the landing itself. NEA voyages represent a natural progression in difficulty, more challenging than the dash-for-the-Moon Apollo missions, but less daunting than a multi-year Mars expedition. So think of an NEA mission as a shakedown cruise for a Mars trip: the 21st-century equivalent of Apollo 8 or Apollo 10, invaluable rehearsals that greased the skids for the first manned lunar landing. When it's time to go to Mars, we'll scale up the propulsion and life support capability for the landing mission - and we'll already have invaluable deep space experience under our belt. Asteroids get us moving in the right direction.

What would the encounter phase of an NEA mission be like? The cruise vehicle would orbit from a safe distance while sending field explorers down to the surface. In the very low gravity field-measured in thousandths of a g - these EVA's would be much more like my delicate tiptoeing around the ISS than the hard-charging marathons of the Apollo moonwalks. Tethering and delicate control will be all-important, since an astronaut and his tools could easily drift away from the surface. More reminiscent of Apollo will be the dust problem. Stirred up by sampling work or thruster firings, the fine particles will take minutes to settle. Planetary scientist Dan Durda of Southwest Research Institute suggests that the astronaut experience will be analogous to cave diving: near-weightless, with the slightest wrong move stirring up a vision-obscuring cloud that will dissipate only slowly. Instead of trying to stand and walk on such a surface, an astronaut might be equipped with a portable scaffold. The strong, light framework could anchor him within arms' length of the work at hand, yet prevent an embarrassing facedown drift into the primordial dust. Imagine a souped-up MMU jetpack, with adjustable struts to prop an astronaut in any desired orientation. Each EVA would end at a central work platform, where each spacesuit would get a thorough - and welcome - dust-off.

It's time for NASA to make a cogent case for moving out of Earth orbit again. The reality is that Congress is not going to hand over a hundred billion dollars for a determined push to Mars anytime soon. Instead, the agency must offer the President and nation a goal that's new and exciting, technically doable, and affordable. Using the lessons learned from ISS hardware, my guess is that we could mount several manned NEA expeditions for no more than about $30 billion, spread over ten years - about the same as the Station's initial construction costs. By way of comparison, that's about half of what the government spent on agriculture - just last year. We can afford this investment.

To get rolling, we should enhance existing NEA search programs. That's how we'll find more attractive, low- V mission targets. (NASA acted correctly in December to restore funding for radar studies of NEA's.) The agency should mount precursor missions to NEA's while defining the scope and cost of human expeditions to these bodies. Its decision to jump-start research into nuclear power and propulsion is a good first move. And focused research should continue on ISS to blunt the hazards - micro-g deconditioning, radiation exposure, and command and control - that will confront a crew embarked on a months-long deep-space mission.

One challenge is already behind us - what to name the asteroid expedition. The first venture beyond Low Earth Orbit since Apollo should be called Virgo, after the sixth constellation in the zodiac. Why Virgo? Its name evokes a leap into virgin territory, yes. But the clincher is to be found in the heavens: as the Sun marches through the zodiac into Virgo, it leaves LEO inexorably behind.

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Tom Jones is a planetary scientist, writer, consultant, and former astronaut. On four space shuttle flights he racked up three spacewalks and fifty-three days in orbit.