Deciding not only how to explore space, but where to go in the first place, are critical issues for NASA's long-term space exploration missions, according to scientists and aerospace experts addressing a presidential commission Friday.
NASA's space vision to send astronauts back to the moon, then Mars, does implicitly address two of its three goals for human exploration, but that doesn't mean it's too early to start looking at the "beyond" bit, panelists told the team charged with shaping U.S. space exploration policy.
"The 'beyond' doesn't really require astronauts," said Jonathan Lunine, a planetary scientist at the University of Arizona. "But it does require telescope systems."
Lunine told commissioners that NASA's Terrestrial Planet Finder (TPF) mission, a space-based telescope to seek out Earth-like planets orbiting alien stars, is a good example of what the space agency is currently doing to identify new targets for space exploration.
Lunine appeared Friday before the Presidential Commission on the Implementation on United States Space Exploration Policy, on the second and last day of the commission's hearings in San Francisco. President George W. Bush appointed the commission to recommend the best course to fulfill his space vision of returning humans to the moon, and sending them onward to Mars, in the next 40 years.
"TPF is the gateway to something much grander," Lunine said, adding the space telescope mission could determine whether alien planets have their own continents and oceans. A follow-up, larger version of TPF could even determine whether a world would be habitable for life, though Lunine admitted such a tool would take two decades or more to develop.
Other astronomers said robotic missions to nearby asteroids, as well as Mars and the moon, could expand NASA's targets for eventual human visitors, possibly culminating in long-term crewed missions aboard nuclear-powered spacecraft.
Space pitstops
Human missions to local asteroids could serve as an incremental step for astronauts making the leap from the moon to Mars.
James Benson, founder and CEO of the private space firm SpaceDev in Poway, California, told commissioners that astronauts could make use of a minor asteroid belt sitting between Earth and Mars thought to contain dormant comets.
The water in those comets, he said, could be converted in to rocket fuel for future missions, and is just one way NASA or even private companies could make use of resources waiting to be used in space.
Some of those who spoke before the commission recommended the eventual use of Prometheus, a NASA project to build a spacecraft that relies on a nuclear reactor for power and propulsion, to visit a near-Earth asteroid and give the space rock a little push. The Prometheus project is currently being designed to serve the planned Jupiter Icy Moons Orbiter (JIMO) mission.
"Asteroids are important for three reasons," said David Morrison, senior scientist at NASA's Astrobiology Institute at the Ames Research Center in Moffett Field, California. "They're left over building blocks of the planets, they could provide important materials such as iron and water in space and they do sometimes collide with the Earth."
Sending the nuclear-powered Prometheus to an asteroid could be used not only prove Earth's capability to push space rocks off a collision course, but also the vehicle's space worthiness as well.
"The near-Earth asteroid mission is far less challenging than JIMO," Apollo 9 astronaut Rusty Schweickart told commissioners.
Another challenge to NASA's space vision is developing new propulsion methods that will carry astronauts through space.
"It's pretty clear that propulsion is the enabling technology to achieve this mission," said Edward "Pete" Aldridge, chairman of the presidential commission.
Aerospace experts told commissioners that NASA does have the rocket technologies to achieve many of its near-term goals, such as sending robotic probes to the moon and Mars. But mid-range goals out past 2012 will require human-rated expendable launch systems that have yet to be developed.
The launch system we put in place must serve this nation for many years after the shuttle's retirement," said Byron Wood, of Boeing Rocketdyne, adding that new or modified rocket engines will be required for future space vehicles. "Without at least some investment from the government, this space vision will not be achievable, or in the least, it will be severely handicapped."
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