Commentary: Astronauts to Asteroids
We've done the moon. Mars is too far. There's a better destination in our own back yard.
- By Thomas D. Jones
- Air & Space magazine, May 2002
FOR MOST OF THE 1990S, THE-NASA ADMINISTRATOR Dan Goldin enthusiastically endorsed the idea of sending humans to Mars. But in the end, he couldn’t deliver the political mandate or the funding to venture anywhere beyond Earth orbit. New administrator Sean O’Keefe, straightjacketed by budget problems, has so far avoided the topic of “Where next?” That leaves advocates of human space exploration wondering where NASA is ultimately headed, and how soon we might get there.
I came face to face with this struggle over “the vision thing” more than a year ago, just 30 minutes before suiting up for my launch on Atlantis to the International Space Station for mission STS-98. In the astronaut quarters at Cape Canaveral, Florida, Joe Rothenberg, then NASA’s chief of human spaceflight, flatly told me and my crewmates that he saw little chance of astronauts rocketing out of Earth orbit for at least 10 to 15 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 public and political support for more ambitious projects? NASA was clearly intent on not rocking the boat; rather than propose bold new initiatives, it would simply wait for direction from the top.
Now the president and nation are preoccupied with a war, and budget surpluses are proving ephemeral, so any near-term goal for space exploration will have to be both practical and affordable. Thirty years after the last lunar landing, what might that destination be?
The answer came into focus for me on February 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 gold handrail on the station’s Destiny laboratory module, I had one of those moments that crystallize into a permanent memory. The event that grabbed my attention was happening almost 200 million miles away, where a spacecraft called NEAR Shoemaker was making history.
As Bob Curbeam and I worked on outfitting Destiny’s exterior, mission controllers outside Baltimore, Maryland, eased the robot orbiter toward the surface of an asteroid called 433 Eros. The spacecraft had rendezvoused with Eros a year earlier and was now 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 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 spacesuit, sweaty with exertion, I was hit by a shiver of excitement, imagining what it would be like to spacewalk not in Earth orbit but a million miles away, drifting over the rubble-strewn surface of a near-Earth asteroid (NEA).
Today I’m even more convinced that these intriguing objects are the next logical destination for NASA after it finishes building the space station. Unlike a three-year voyage to Mars or establishing a base on the moon, journeys to near-Earth asteroids can get us back in the business of exploring terra incognita soon. And whatever we learn from an asteroid mission would be invaluable to future exploration of the moon and Mars.
What makes NEAs so attractive is their accessibility. Over the past ten years, astronomers have discovered hundreds of asteroids whose orbits around the sun bring them close to Earth. Many are easily reachable with only modest improvements in spaceflight technology; in fact, some are easier to reach than the moon. Already we know of a handful of NEAs that would require less than a year—round trip—for astronauts to explore, and reaching them would use less rocket fuel than a visit to the lunar surface. The flight times are shrinking almost daily. Last year, for example, Leon Gefert of NASA’s Glenn Research Center in Cleveland, Ohio, found that a round trip to 1991 VG, a small NEA only tens of meters across, would take as little as 60 days, with half the time spent exploring the asteroid. Astronomers believe there are hundreds of similar objects out there, waiting to be discovered.
Now, for the first time, we’re talking about journeys beyond the Earth-moon system that are well within the range of current human spaceflight experience. Many cosmonauts and astronauts have already spent more than 60 days in space with no serious problems. “Weekend getaways” to asteroids would be even shorter than a typical tour of duty on the space station, and minimizing exposure to microgravity, cosmic radiation, and solar flares might reduce health risks. Since the astronauts on an NEA mission would never stray more than a few million miles from home, they could abort directly back to Earth in case of an emergency, and be home within weeks.
It isn’t enough, of course, to say we should go to asteroids just because they’re easy to reach. What would such a project offer the nation as a “return on investment”? One payoff would be scientific: Asteroids offer a rich and untapped store of knowledge about the early solar system. An array of asteroid samples, chosen intelligently by field explorers, would tell us how the original stuff in the solar nebula coalesced into planets and other rocky objects billions of years ago. Robotic sample-return missions couldn’t harvest as much material; nor would we expect robot missions to return samples of the same scientific value.
There may also be an economic reward. Asteroid missions would assay natural resources that may eventually help us reduce the horrendous cost of space exploration. For example, the space shuttle currently hauls supplies to the station at a staggering $10,000 a pound, with much of the load being water and propellant. Some NEAs are composed of clay minerals that contain up to 10 percent water. Extracting it and turning it into hydrogen and oxygen rocket propellant may some day prove cheaper than dragging it up from Earth.
Exploring asteroids could also serve as a practical hedge against the impact threat. In January of this year, an NEA called 2001 YB5 swung within 400,000 miles of Earth, less than twice the distance to the moon. Had this stadium-sized boulder hit Earth, it could have devastated a region as large as the coastal states from New York to Virginia. An NEA mission could provide structural and composition data that would enable us to devise a practical scheme for diverting an asteroid should one threaten us.
Finally, sending astronauts to NEAs gets us moving toward Mars. As a spacefarer, I find that the greatest attraction of the “astronauts to asteroids” idea is that all the development costs would directly benefit an eventual Mars expedition. The spacecraft used for an NEA mission would have to do nearly everything required of a Mars ship, 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, valuable rehearsals that greased the skids for the first lunar landing.
It’s time to make a cogent case for moving out of Earth orbit again. The reality is that Congress is not going to hand over $100 billion for a push to Mars anytime soon. NASA must offer the nation a goal that’s new and exciting, doable in the near term, and affordable. I estimate that if we capitalize on experience gained from the space station, we could mount several manned NEA expeditions for about $3 billion a year over the course of 10 years—about the same as the station’s initial construction costs. By way of comparison, $3 billion is less than five percent of the U.S. Department of Agriculture’s annual budget, or half of what American consumers paid for video games last year. We can afford the investment.
To get rolling, we should enhance existing ground-based asteroid search programs to identify attractive, easily reachable targets. NASA should mount robotic precursor missions to NEAs while defining the scope and cost of human expeditions. And focused research should continue on the space station to address the health hazards that will confront astronauts on a deep-space mission.
One challenge, though, is easy—what to name the asteroid expedition. The first voyage beyond Low Earth Orbit (LEO) since Apollo should be called Virgo, after the sixth constellation in the zodiac. Why Virgo? The name evokes a leap into virgin territory, yes, but the clincher is in the stars: As the sun crosses into Virgo in late summer, it leaves Leo inexorably behind.