HOUSTON - In labs at Johnson Space Center, away from the buzz about NASA's new spaceship and its new missions to the moon and Mars, a group of engineers are plodding away at another piece of the puzzle: spacesuits.

Astronaut apparel has evolved over the decades from Mercury's aluminum foil-looking outfits to the bulky, 275-pound whites now used on jaunts outside the space station. While it's too early in the process to know how the new suits will look, the space agency is hoping to make new suits both high-tech and low-maintenance.

"Finding the right balance is always going to be a challenge," said veteran astronaut Jeff Williams, who has donned both the complex American suit and the spare Russian suit. "It's trade-offs."

The U.S. suits are easier to work in for long periods of time, but their complexity causes more maintenance. The one-size-fits-all Russian suits are used a few times and thrown away, but they're also not as easy to work in.

Developing the new suits is easier than in the Apollo era, when designers had to rely on slide rules and drafting tables. The suits are designed and re-designed on computer screens before any hardware is used.

"There's a lot more capable tools and technology to get the job done -- a lot more knowledge, as well -- so we can capitalize on them," said Joe Kosmo, who participated in the design, development and testing of suits from the Mercury, Gemini, Apollo, Skylab and shuttle eras.

At the top of the list is making the next spacesuit smaller and lighter -- engineers are hoping to halve the 200-pound weight of the suit and life support backpack that Apollo astronauts lugged around.

NASA plans to use new, lightweight composite materials and take advantage of smaller electronics to shrink the life support backpacks. NASA also wants the astronauts to be able to move around easily.

Terry Hill, who's developing the new spacesuit, recalled the robotic-like hops of the Apollo astronauts broadcasting from the moon.

"Mostly, that was because of mobility -- they just didn't have it," he said.

NASA wants to make the new spacesuit usable for launch, at the space station and on the moon and Mars. Hill envisions swapping out the top part of the suit to fit the mission's needs. He hopes this feature will save money and cargo weight, because astronauts won't have to load up on several suits. Shuttle astronauts don bright orange suits for launch and re-entry and carry on the white spacewalking suits.

Some of the must-have features of a spacesuit are the ability to withstand extreme hot and cold temperatures, to shield radiation, and function on very low power because the spacesuit's oxygen-rich atmosphere can quickly turn sparks into fires.

Hill won't discuss the pricetag on the new suits because a production contract has yet to be awarded. "Nothing's cheap," Hill said.

NASA plans to award a contract in a year or so, produce the first prototypes by 2010 and certify the suit by 2012 in time for the new spaceship Orion's maiden voyage by 2014.

For Williams, who lived on the space station for six months last year, the space agency needs to dedicate the time and resources to get the suit right so the nation can enjoy the investment on going back to the moon and onto Mars.

"In the end," Williams said, "we'll be relying on these suits to go and do our exploration."