Astronauts and space go hand in hand. Or do they?
In the 1960s, when money flowed freely to NASA, putting men on the moon was the pride of the United States space program. After the Challenger accident, and with federal money tight, Congress and some NASA scientists are questioning the value of using men in space travel and exploration.
It's generally cheaper to use unmanned launch vehicles, planetary probes, experimental facilities, and observatories. Introducing humans into the process has benefits, but it also means providing life-support systems, living quarters, and higher standards of safety.
In many cases, unmanned space projects are precursers of manned exloration. A robotic sample return mission is certain to preceed a manned expedition to Mars.
But sometimes unmanned space science programs, that go where man cannot, get squeezed out when NASA undertakes glamorous projects like the space shuttle. For example, plans to send a US spacecraft to Halley's comet in 1986 were canceled, in part, because of ballooning shuttle costs.
After Challenger, NASA began to consider the advantages of an unpiloted launch rocket (in addition to the shuttle) for satellites and other cargoes that do not require astronauts to deploy them. In a period of tight money, other manned programs are also getting a close look.
A $25-billion permanently manned station in space and continuation of the shuttle program form the core of NASA's current plans for the mid-1990's. The station will provide support for space and materials research, but some scientists consider it primarily a base for supporting the extention of human presence in space.
Expanding human presence to Mars or the moon is an implicit goal, according to a Congressional Budget Office study released last spring.
Holding NASA budgets to current levels would require stretching out the space station until 2005 or ``de-emphasizing manned space activities,'' says the budget office report. In such a case, the US would defer going to Mars for the time being.
On the other hand, tripling NASA's budget (currently $9 billion) by the year 2000 would permit a Mars mission early in the 21st century.
Which of these roads the US follows depends heavily on the next president. All are real possibilities.
Reasons to expand human presence into space range from the pragmatic to the symbolic.
``If NASA did not have a manned space flight program it would not be as popular as it is,'' says Terry Dawson, staff member of the House Science, Technology and Space Committee. It would just be another science agency ``out of the public mind.''
Often men can do what machines can't.
``There were all sorts of experiments that flew on Spacelab that wouldn't have returned any results unless someone had been up here on the Shuttle to fix them when they broke down,'' says Jeffrey Rosendhal, a visiting professor at George Washington University's Space Policy Institute.
Dale Andersen, a Lockheed senior biologist who looks for life beyond Earth, says studying a planet with robotics is not enough. ``When you do it remotely, you have this preconceived notion and you send that notion out there in a can. If you let it look around you either see exactly what you are looking for or you don't see exactly what you are looking for.... Whereas a man can reconsider the situation completely.''
Ultimately, exploration is never done just for the scientific returns, Mr. Andersen says. He supports a manned Mars mission mainly to get people thinking. ``People should be able to look at that sparkle in the sky and feel good about themselves....'' There are very few things that ``get people to stop thinking about the mundane,'' he says.
``If people stop thinking creatively then their culture dies. This is one way to keep from stagnating,'' he says.
The benefits of manned space flight are difficult to quantify. ``You have to start assigning costs to things people don't know how to assign value to. For example, what is the value of having a human on Mars who can kick the dust and pick up a rock that a machine wouldn't have noticed?'' asks Edward Crawley, an astronautics engineer at the Massachusetts Institute of Technology.
No one is really sure that people could ever make it to Mars and back. An unmanned Viking mission landed on Mars in 1976 and began relaying photographs.
Nevertheless, the Soviets have long had a specific, stated goal to send men to Mars. For over five years they have been studying the ability of humans to endure long periods in the low gravity of space. The longest a cosmonaut has stayed in space is one year. A Mars round trip would take at least two.
The planned US space station would provide US, Japanese and European scientists with the opportunity to do similar long-duration studies.
One thing scientists seem to agree on: If the US undertakes a manned Mars mission, it should not be a publicity stunt. It should be an evolutionary process of exploring the planet as a long-term project, says Dr. Rosendhal.