Engineers reviewing options for a heavy-lift NASA Space Launch System (SLS) to replace the canceled Ares V will make their final selection no sooner than late June, a pace that is sure to add to the irritation among those in Congress who believe the U.S. space agency is moving too slowly on the big new rocket.

Doug Cooke, associate administrator for exploration systems, told the House Science subcommittee on space and aeronautics March 30 that the final design selected probably will not be able at first to lift the full 130 metric tons ordered in the three-year NASA Authorization Act that Congress passed and President Barack Obama signed last year.

Instead, it will evolve into a system capable of orbiting the full 130-metric-ton load, with incremental capabilities along the way. Even at the lower end — 70-100 metric tons — a backup using the planned SLS and its Orion-based deep-space crew capsule to carry astronauts to the International Space Station will be “inefficient” compared to the commercial vehicles now tapped for the job, Cooke says.

Pressed by Rep. Donna Edwards (D-Md.), at a hearing on the transition between the old Constellation program of exploration vehicles and the new approach, Cooke said the earliest NASA expects to settle on a final path for the new heavy lifter will be late June — and that would be “a success-oriented approach.”

So far, he told Edwards, the reference design announced in January is still holding up. That would be a hybrid of space shuttle and Constellation heritage hardware using five liquid oxygen/liquid hydrogen space shuttle main engines (eventually in a throw-away variant); an upper stage powered by the J-2X developed for Constellation upper stages that would match the 27.5-ft. dia. of the shuttle external tank; and twin five-segment versions of the four-segment shuttle solid-fuel boosters originally developed as the first stage of the Ares I crew launch vehicle.

However, engineering teams continue to study a kerosene-fueled alternative to the reference mission, and a “modular” approach that would mount three smaller-diameter main stages side-by-side, a configuration comparable to the Delta IV Heavy. And NASA is awaiting the results of 13 separate industry studies aimed at producing a better heavy lifter. “Right now we’re not altering the reference design,” Cooke says. “We are updating some of the approaches in the design that would make it more efficient. We are also studying alternative designs to make sure we challenge our own thoughts. At this point we’ve not made changes.”

Like their counterparts in the Senate, members of both parties on the House committee said they were frustrated with NASA’s approach, particularly as it is reflected in the fiscal 2012 budget request that emphasizes commercial cargo and crew and open-ended technology research over near-term, heavy-lift development.

“The debate is over,” says Rep. Ralph Hall (R-Texas), chairman of the full science panel. “This act is the law. NASA has its direction. The administration needs to acknowledge this, and act accordingly.”

The uncertainty is making it hard for NASA contractors to develop business plans, according to Jim Maser, president of Pratt & Whitney Rocketdyne, who testified on behalf of the corporate membership of the American Institute of Aeronautics and Astronautics. “We simply do not know what is next” (Aerospace DAILY, March 8).