Houston, we have a problem.

More than two months into his presidency, Barack Obama has yet to name a replacement for former NASA Administrator Michael D. Griffin, leaving the 18,000-man space agency flying without a navigator.

As NASA faces burgeoning budget problems and prepares to retire its aging fleet of space shuttles, 3,500 jobs are at risk in the years preceding the launch of the shuttle's replacement.

That's got NASA employees and members of Congress itching under the collar.

"Our nation cannot afford to be without a NASA administrator at this time," said Rep. Bill Posey, R-Fla., whose district in Florida's "Space Coast" would be hard-hit by job losses. "This is a critical juncture in the manned spaceflight effort, and now it's up to President Obama to lead the way."

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Posey joined 13 other representatives from the House Action Team on NASA in writing to Obama last month, imploring the president to shore up support for the agency and to quickly appoint a permanent administrator.

"We believe it is imperative for NASA to have a leader who understands the implications of a five-year or longer hiatus in America's independent access to space," they wrote, addressing the urgency of the expected gap in U.S. spaceflight capability when the 30-year-old shuttle program ends next year.

NASA is facing yet another vacancy at the top after its longtime inspector general, Robert "Moose" Cobb, resigned his post April 2 under increased pressure from both houses of Congress, which for years have charged him with misconduct and failures in oversight of the agency.

Government inquiries have accused Cobb of stifling investigations, retaliating against whistleblowers and using abusive conduct and vulgar language with his staff. A Government Accountability Office report also found that his office was inefficient, saving only a fraction of the money other inspectors have saved their agencies.

Obama made human space exploration and research a major part of his science platform, but the economy and the challenges of shoring up other top advisers have diverted his attention from NASA, which had expected special consideration from the new administration.

"I will soon be appointing a new NASA director," Obama told reporters in March, noting that "it's important for the long-term vibrancy of our space program to think through what NASA's core mission is, and what the next great adventures and discoveries are under the NASA banner."

Four weeks later, NASA is still without a permanent chief, and its normal leading triumvirate remains an army of one — Chris Scolese, the former No. 3 who has been acting administrator since Jan. 20.

"It's not a very good situation," said James Logsdon, a former member of the NASA advisory council who helped craft Obama's space policy during the presidential campaign.

Logsdon said Scolese is hamstrung by not having deputies to help handle the triple tasks of management, engineering and politics that make up the administrator's job.

The delay is not for lack of effort on Obama's part. The administration floated potential nominees even before the inauguration, but they wilted under the withering glare of the Senate, which must approve the president's selection.

Retired Maj. Gen. Scott Gration, who campaigned for Obama and advised him on military issues, was being pushed for the post until Florida Sen. Bill Nelson, a key voice on space issues, sought a candidate with more experience at the agency.

The Swahili-spaeking Gration, who was raised by missionaries in Africa, was named instead on March 18 to be Obama's special envoy to Sudan.

Former NASA official Steve Isakowitz was also considered for the post but ended up as chief financial officer of the Department of Energy. He was likely hurt by a report that shined a negative light on his budget work at the space agency.

Those setbacks mean NASA continues to wait in limbo.

Its uncertain future and lack of direction is "driving folks crazy," said Michael Coats, director of NASA's Johnson Space Center in Houston.

"I know Chris Scolese, the acting administrator, is reluctant to make anything that might be perceived as policy decisions, and yet it's very hard when you're running an agency to make a decision that isn't perceived as policy in some way," Coats said, according to a report from Space News. "So Chris is kind of in a tough spot. He's doing a great job ... but he needs some help over there."

Not all experts are troubled about the agency's fate in the interim.

Former NASA administrator Sean O'Keefe, who preceded Griffin, told FOXNews.com that Scolese is an "extraordinarily competent guy" who has a deep knowledge of engineering and of the "pulse and the rhythm of the agency."

"He's got it — he's going to be in fine shape," said O'Keefe. "It's not like the wheels are going to come off the cart."

A spokesman for NASA said the Obama administration already has three appointees at the agency and that Scolese has plenty of guidelines for action from Congress and the previous administration.

"This is not the first time that the agency has operated for a period of time without politically appointed leadership," said NASA spokesman Bob Jacobs. "That has happened in our past, and the organizational structure of our agency provides for continuity of operations just in this situation."

But for NASA and for Obama, who lamented in March that "there's been a sense of drift to our space program over the last several years," the coming challenges remain clear and stark.

The next administrator will have to manage not only the shuttle's retirement, but the hastening of the Constellation program meant to replace it.

He or she will also have to manage and rein in a budget the Government Accountability Office and taxpayer watchdogs say has been spiraling out of control.

The top team of three appointees at NASA — administrator, deputy administrator and associate administrator — will have to combine technical skills, managerial skills and political connections, said Scott Pace, director of the Space Policy Institute at George Washington University.

Those three leaders will have to head up an agency that is "relearning how to fly again," he said, as it sets its sights on the moon and Mars for the coming decades.

Though Obama has delayed his appointment, and the Senate is wrangling for a leader with the scientific background to head up NASA, Logsdon pointed out that the next administrator doesn't necessarily have to be a lifelong engineer.

"In general, people think of the man that ran NASA [in the 1960s] during Apollo, Jim Webb, as the most successful administrator," said Logsdon, "and he was a lawyer."