WASHINGTON — In his April 15 speech at NASA’s Kennedy Space Center, Fla., U.S. President Barack Obama said the space agency would spend the next five years studying new technologies and materials before settling on a heavy-lift rocket design. But NASA documents and comments from agency officials  suggest the White House already has a design firmly in mind.

On May 3 NASA issued a request for information that gives U.S. aerospace firms roughly three weeks to volunteer ideas for a versatile, liquid-fueled heavy-lift rocket that incorporates a first-stage engine that burns a mixture of liquid oxygen (LOX) and kerosene to produce at least 1 million pounds of thrust.

The document also requested industry input on an in-space engine demonstration program that would focus on flight testing a new LOX/hydrogen or LOX/methane upper-stage engine that could be used on the heavy-lift rocket.

A few hours later, NASA posted a revised solicitation that eliminated all references to LOX/kerosene or any other specific liquid propellant and now gives industry the leeway to submit information on a wider range of heavy-lift architectures that could meet NASA, U.S. Defense Department and commercial needs.

Cris Guidi, deputy director for NASA’s Constellation Systems Division, said the initial request for information — drafted in response to White House budget guidance — was posted by mistake. “The guidance that we originally received based on the president’s budget submit was to focus on a large LOX-hydrocarbon engine,” Guidi told Space News May 7. She added that the White House felt that a LOX/kerosene first-stage engine would be more affordable than other propulsion capabilities, including the type of solid-rocket motors used on the space shuttle and long planned for the Ares 1 and Ares 5 rockets the president has marked for cancellation along with the rest of the Moon-focused Constellation program.

But Guidi said after several “meetings and negotiations” with the White House Office of Management and Budget (OMB) and Office of Science and Technology Policy (OSTP), it was clear the president’s primary goal was to lower the cost of launch. Now, with the modified solicitation in mind, Guidi said NASA intends to evaluate myriad heavy-lift concepts and base its choice on cost and reliability.

“We’re going to go with the most affordable system,” she said. “And OMB and OSTP actually agreed to that.”

OMB spokesman Tom Gavin said May 7 “the primary focus for first-stage propulsion [research and development] under the new effort is on hydrocarbon engines that are likely to play a key role in an affordable and sustainable heavy-lift rocket, as well as potentially in future rockets for commercial and national security purposes.”

Gavin said NASA also will fund “foundational propulsion research” that could address a wider range of rocket technologies and propellants, including solid propellants.

Guidi said studying the spectrum of heavy-lift engine options  helps NASA remain in compliance with a law passed in December that requires the agency to keep working on Constellation until Congress explicitly approves a new direction. Lawmakers opposed to abandoning Constellation have accused NASA of slowing work on the program in preparation for pulling the plug later this year.

“NASA is currently in a very odd position that we are straddling [fiscal 2010] appropriations as well as what the president recommended for [fiscal 2011], which has not been approved,” she said.

In the meantime, Guidi said the broader study of engine options leaves the door open for a future heavy-lift architecture that incorporates solid-rocket motors, an option that should help appease lawmakers seeking to sustain the U.S. solid-rocket-propulsion industrial base.

“Is there a future? Possibly,” she said. “Again, it all depends on the vehicle concepts we study, and how they pan out as far as from an affordability figure of merit.”

Two days after NASA posted and then revised an RFI specifying a LOX/kerosene engine for the nation’s next heavy-lift launcher, Guidi’s boss — NASA deputy associate administrator for exploration systems Laurie Leshin — briefed an industry gathering here on a plan to develop a LOX/kerosene prototype engine by 2016 and field an operational version by 2020.

But Guidi said that plan is likely to change in light of Obama’s April 15 call for NASA to finalize a heavy-lift rocket design no later than 2015 and then begin to build it.

“The original guidance we got Feb. 1 was purely just engine development,” Guidi said, referring to NASA’s 2011 budget request.

Guidi said the White House also expects NASA to focus on propulsion development that could satisfy multiple customers, including the Defense Department, which currently relies on  Atlas 5 and Delta 4 rockets operated by Denver-based United Launch Alliance.

“The whole reason for that is so that the government gets the best price,” she said, adding that the Defense Department would be closely involved with NASA’s heavy-lift development plans. “We’re going to do this system analysis jointly where we’re going to determine what’s the best approach and does it make sense to have a common upper stage between NASA and Air Force.”

Guidi said that if NASA chooses to pursue development of a liquid first-stage engine, the goal would not be to produce a U.S. clone of the Russian-built RD-180 engine currently used to power the Atlas 5.

“Our goal is not to replicate the RD-180, our goal is to build a hydrocarbon engine that both NASA and [the Defense Department] and hopefully commercial can use,” she said, adding that NASA and the Pentagon would study thrust levels and other engine characteristics capable of satisfying civil, military and commercial needs. Guidi said NASA is looking for an engine that would exceed the 860,000 pounds of thrust the kerosene-fueled RD-180 delivers.

“We’re not Americanizing the RD-180 is the bottom line, but we are building a large hydrocarbon engine,” she said.

Guidi said the goal of NASA’s heavy-lift research and development effort — budgeted at $3.1 billion between 2011 and 2015 — is to make space launch more affordable, not necessarily produce the kind of technological breakthroughs called for in other parts of Obama’s space exploration plan.

“It’s to drop the cost of launch, and the propulsion system is the predominant cost factor in any launch system,” she said. “But it’s more to stabilize the industrial base and maintain the critical skills of propulsion-system development in the U.S.”

While NASA is not ruling out building a heavy-lift solution that incorporates solid-rocket motors, Guidi said affordability, reliability, and the flexibility to serve multiple users are paramount.

“Obviously we don’t have the budget to maintain the current course of Constellation,” she said, adding that the Ares 5 design — promising more lift than the Apollo program’s Saturn 5 rocket — emphasized performance over cost. “Our goal is affordability. Let’s not build that Maserati. Let’s make do with maybe a Toyota, as long as we get our mission accomplished in an affordable, reliable, operable manner. That’s our best approach rather than having a system that operates on the margins and is very intricate.”

Whether Ares 5 — or something like it — makes the cut remains to be seen.

“That’s not to say that an Ares 5 may not fall out to be a more affordable option than” a LOX/kerosene option, she said. “That’s why we wanted to open up the trade space and say, ‘Let’s not just focus on [LOX/kerosene]. Let’s do the entire spectrum now that we’ve got a new focus on affordability.’ And if we find that some options just continue to be too expensive for us, we just won’t address them.”