WSHINGTON — NASA is considering slowing development work on a congressionally mandated crew capsule to better align its schedule with a heavy-lift launch vehicle the agency was ordered to build in the same law, according to a senior NASA official.

The 2010 NASA Authorization Act directs the agency to field the heavy-lift Space Launch System by 2016, but NASA has said it cannot meet that schedule.

Douglas Cooke, head of NASA’s Exploration Systems Mission Directorate, said the agency is considering how both the Multi Purpose Crew Vehicle (MPCV) and Space Launch System fit within the agency’s lower-than-expected funding profile. NASA’s 2011 budget is $18.4 billion, which is $600 million less than both the agency’s request and what was recommended in the authorization act.

“We’re … looking, from an integrated standpoint, how all this fits within the budgets that are called out and looking at whether there are advantages to slowing down the work on MPCV or picking it up later,” Cooke told members of the NASA Advisory Council’s exploration subcommittee April 26. “We’re looking at how we meter the progress on the crew vehicle in conjunction with this development of the launch vehicle.”

The NASA Authorization Act of 2010 directs the agency to begin building the Space Launch System this year while continuing work on an MPCV based on the Orion Crew Exploration Vehicle under development by Denver-based Lockheed Martin Space Systems. Orion is among the surviving elements of the Moon-bound Constellation program, which was canceled last year by President Barack Obama.

The law directs NASA to make the most of its aging space shuttle infrastructure and the billions of dollars invested in Constellation, which also includes the Ares family of rockets. The Ares 1 rocket was designed to launch Orion, initially to the international space station; the heavy-lift Ares 5 was designed for manned missions to the Moon.

But in a preliminary report sent to lawmakers in January, NASA said it could not build the heavy-lift launcher by 2016 for the roughly $11 billion one key U.S. lawmaker, Sen. Bill Nelson (D-Fla.), pledged to provide between now and then. Orion, which has been in development since 2005, completed a preliminary design review last year.

“Obviously at this point we are ahead on design of the crew vehicle,” Cooke said. “We’re regrouping to develop the heavy-lift vehicle, which now has to go through the various programmatic steps with development of requirements.”

Cooke said NASA recently determined its existing Orion contract with Lockheed Martin could be leveraged to continue work on the MPCV. However, the agency is still settling on a design for the Space Launch System and evaluating whether space shuttle and Ares rocket contracts are suitable acquisition avenues.

In the meantime, he said NASA is considering different options for launching the MPCV to low Earth orbit, including using existing or commercially developed rockets. But for missions to deep space destinations such as the Moon or an asteroid, a heavy lifter comparable in capability of the Space Launch System would be needed, he said.

“We’ve looked at whether or not you try to use commercial crew vehicles to put people in orbit and then have a vehicle that takes them out beyond that,” he told the panel. “There are some big differences in requirements, basically [that] at this point drive you to launching it probably with the heavy-lift vehicle.”

Regardless, Cooke said, at some point the operational capability of the Space Launch System and MPCV should coincide.

“We’ve talked about … whether or not you get to a certain point on one and kind of go into a holding pattern,” he said. “One of the things that we’d like to be able to do is fly … a flight test of the crew vehicle to make sure we’re where we need to be on those systems. We’d like to have them come together for that sort of capability.”

However, putting Orion in a holding pattern while work progresses on the heavy-lift launch vehicle could end up costing more in the long-run, Cooke said.

“Definitely as things stretch out you carry a workforce longer, so those get to be factors in the cost,” he said.

Lockheed Martin spokeswoman Joan Underwood did not respond by press time to requests for comment.