HOUSTON, Texas - The International Space Station is an invaluable teaching tool for hardware and assembly ideas required to install a permanent base on the Moon and for dispatching humans onward to Mars.

The orbiting outpost--still being built--shouldn't be thought of as completely finished anytime soon, said William Gerstenmaier, NASA's Space Operations Mission Directorate Associate Administrator.

"It's really more than completing the space station. We're learning assembly techniques that can be used for exploration. As we go to Mars we're not going to be able to do that Mars journey with a single spacecraft launch. We're going to have to do some type of assembly in space," Gerstenmaier said.

Gerstenmaier spoke today here at the 2nd Space Exploration Conference - Implementing the Vision, organized by the American Institute of Aeronautics and Astronautics.

What works, doesn't work

"We get a chance to learn what works and doesn't work" on the International Space Station (ISS), Gerstenmaier added, valuable lessons learned for a Moon base and the long journey by crews to Mars. "The space station is not just about completing it but how it fits into the larger goal of exploration."

Re-supply of the ISS has spotlighted how best to re-supply crews on the Moon and for later human voyages to the red planet, Gerstenmaier said. Moreover, the ISS has shown "what works and doesn't work...what's too complicated...takes too much time...what involves more risk than necessary," he said.

ISS experience has yielded insight into the redesign and change of systems so that voyages to Mars can be made more routine, Gerstenmaier noted.

Lessons learned

NASA announced yesterday that the space agency is putting at the top of a beyond Earth agenda the establishment of a Moon base.

"We have made the determination that we're going to be 'base-centric'; get as much mass down to the surface of the Moon and leave it there ... to build up infrastructure," said NASA's Scott Horowitz, Exploration Systems Mission Directorate Associate Administrator.

That ability to land substantial hardware on the Moon for use by crews on the Moon is a pattern akin to what is planned for later Mars expeditions, Horowitz said.

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With the space station, the sphere of human influence has been extended to a couple of hundred miles above the Earth. That human influence will be taken to a couple hundred thousand miles from the Earth to the Moon, Horowitz said.

"And those lessons learned will be extended as we take ourselves a couple of hundred million miles away from Earth," Horowitz added, to the planet Mars.

Thick and thin

Getting boot prints on Mars won't be easy, suggested Lisa Porter, NASA's Aeronautics Research Mission Directorate Associate Administrator. A major challenge is Mars entry, descent and landing of large human-carrying spaceships.

"In a nutshell, this is an extremely challenging problem," Porter advised. The atmosphere of Mars is thick enough to become worrisome in terms of spacecraft heating issues during entry. But it is also thin...so thin that how to handle deceleration of large landing ships is a concern.

"So it's a very tricky atmosphere to deal with. Quite frankly, given where we are today, and the payloads we're talking about for humans, we can't get there from here right now given the knowledge that we have," Porter said. "We have a lot to learn...we have a lot to do in order to be able to put those kinds of payloads on Mars safely."