BOULDER, Colo. — With NASA’s human spaceflight plans in limbo following an independent study’s conclusion that the current U.S. strategy for lunar exploration is unaffordable, asteroids are getting increased attention from both agency scientists and industry as a potential destination for astronauts.

Among the exploration options now under consideration by U.S. President Barack Obama is one dubbed Flexible Path that features astronaut flybys of near-Earth asteroids or Martian moons such as Phobos. Although just one of five alternatives devised this summer by the Review of U.S. Human Spaceflight Plans Committee, an independent panel led by former Lockheed Martin chief Norm Augustine, Flexible Path is favorably viewed within the White House, according to government and industry sources.

Studies outlining the merits of a human mission to a so-called near-Earth object (NEO) were detailed here Nov. 18 during a two-day meeting of the Small Bodies Assessment Group. Established by NASA in 2008 to identify scientific priorities and opportunities for the exploration of asteroids, comets, interplanetary dust and other objects, the group also provides scientific input about the utility of these bodies in support of human spaceflight.

The new studies are viewed as an iterative process — to be weighed by both NASA and the White House, said Paul Abell, a research scientist at the Planetary Science Institute detailed to the space agency’s Johnson Space Center in Houston. “It’s going to take a bit of time,” he said of the White House’s deliberations on NASA’s future human spaceflight program. “I don’t think there’s going to be a quick decision.”

But while nobody knows which direction the White House ultimately will choose, an asteroid mission had gotten the attention of one major contractor, Denver-based Lockheed Martin Space Systems, which is building NASA’s Orion Crew Exploration Vehicle.

Orion is a central component of NASA’s current hardware architecture for replacing the space shuttle and returning to the Moon. Although that architecture, which also includes the Ares 1 crew launcher and Ares 5 heavy-lift rocket, is now in question, Orion in some variation could survive a White House-ordered shakeout.

“We have been looking at what other interesting science missions could be done with Orion … and asteroids were one of the ideas that percolated to the top,” said Josh Hopkins, who works in the advanced programs for human spaceflight division at Lockheed Martin Space Systems. He made it clear that the firm’s study was done using corporate funds and does not imply that NASA has endorsed company results.

Initial looks at the NEO venture involve the coupling of two Orion spacecraft.

In this situation, a two-person Orion would link up with an unpiloted sister craft loaded with extra fuel, food, water and oxygen. The second craft, along with an Earth departure propulsion stage, would be launched by NASA’s planned Ares 5 heavy-lift booster.

A number of issues, including safety, trash management, radiation protection and abort scenarios, must still be addressed, Hopkins said at the meeting. But given the core attributes already designed into the Orion system, “we think it does make sense for the human spaceflight program to be investigating this,” he said.

The studies indicate astronaut missions to a NEO could occur in the 2020-2025 timeframe, with round-trip missions lasting some six months.

There would be no landing on the asteroid. Rather, the astronauts would park their vehicle in close proximity, then use personal propulsion devices — such as a jetpack — to reach the object. Once there, the astronauts would deploy science gear and gather samples of the space rock for detailed examination.

“We assume staying at the asteroid for five days. They could stay a week or two. But staying for a month gets hard,” Hopkins explained. While on duty, astronauts would engage in gathering data useful to understand the internal makeup of the asteroid. That, in turn, is helpful in dealing with space rocks on a potential collision course with Earth, he said.

Today, there are a handful of candidate asteroids that could be visited a couple of decades from now, said Clark Chapman, an asteroid expert at the Southwest Research Institute here. That number will grow as more ground- and space-based instruments enter into operation, increasing the discovery rate of NEOs, he stated.

“We’d really like a larger pool of candidate targets so that we could visit an NEO that has cool properties and would have the greatest scientific return,” Chapman said.

Science by itself does not drive human exploration, said Mark Sykes, chairman of the Small Bodies Assessment Group and director of the Planetary Science Institute in Tucson, Ariz. However, “we can benefit scientifically from this,” Sykes said. “We’ll take advantage of whatever opportunities come our way.”

Sykes said he had briefed the Augustine committee on the possibilities of missions to NEOs. He said he underscored the point that NEOs are a potential source of resources that could have a profound impact on expanding sustainable human operations beyond low Earth orbit. They could contain water, for example, which in addition to being necessary to sustain life could be used to produce hydrogen fuel, he said.

”It’s within the realm of consideration. Of course, a lot more homework needs to be done,” Sykes said.

Leonard David has been reporting on space activities for nearly 50 years. He is the 2010 winner of the prestigious National Space Club Press Award and recently co-authored with Apollo 11’s Buzz Aldrin the book “Mission to Mars — My Vision for Space...