WASHINGTON — When NASA Deputy Administrator Lori Garver leaves her post in September to begin a new career as a labor leader, the Obama administration and its commercial space allies will have lost a passionate champion for leaving Apollo in the past and transforming the U.S. space agency into a model of 21st century innovation.

Whether her departure is viewed as good or bad for NASA depends on whether one thinks the politically savvy Garver has helped chart a sustainable new course for a U.S. space program that had been bent on returning to the Moon, or cast it adrift.

Commercial space advocates are among those who will be sorriest when she steps down Sept. 6 from the agency that has been central to her career for the past 30 years to become general manager of the Air Line Pilots Association, a labor union representing more than 50,000 commercial pilots in the United States and Canada.

“Lori made a real difference to the future of spaceflight,” Elon Musk, founder and chief executive of Space Exploration Technologies Corp. (SpaceX), told SpaceNews. “Most people put their career first, so they play politics and pander to the vested interests. But there are some who truly care about humanity’s future in space and will do the right thing in the face of immense opposition. We are fortunate to have several such people in NASA senior leadership and Lori was one of them.”

Hawthorne, Calif.-based SpaceX, builder and operator of the Falcon line of commercial rockets, is a central player in NASA’s Garver-championed effort to outsource crew and cargo transportation to and from the international space station.

NASA Administrator Charles Bolden, in a message sent to the agency’s 18,000 employees Aug. 6 — the day after Garver announced her impending departure — said that while he is “sorry to be losing such a talented and passionate co-pilot, I am happy that Lori is continuing to pursue her dreams and make her mark in the aerospace industry.”

Garver told SpaceNews in an Aug. 6 interview that the causes she has championed  for space policy will continue after she has left the NASA headquarters building at 300 E St. SW in Washington.

“I actually do feel like so much of what I set out to do is being accomplished,” said Garver, NASA’s highest-profile No. 2 in recent memory. “These jobs do tend to take their toll and I just couldn’t imagine being able to accomplish so much of what we set out to do four years ago.”

Garver, who assumed the post in July 2009, has spent most of her career working on space policy. She came to Washington in 1983 to work for then-U.S. Sen. John Glenn (D-Ohio), the first American astronaut to orbit the Earth. After Glenn’s failed 1984 presidential bid, Garver went to work for the National Space Society, rising to executive director, a job she held until joining NASA in 1996 as a policy adviser to then-NASA Administrator Daniel Goldin.

After President George W. Bush took office in 2001, Garver left NASA for the private sector, advising Lockheed Martin, Northrop Grumman and the Planetary Society, among others, as a vice president at the Washington-based consulting firm DFI International, which has since been renamed Avascent Group.

Garver served as lead space adviser to Democrat John Kerry’s 2004 presidential campaign as well as Hillary Clinton’s 2008 run. When Barack Obama defeated Clinton in the Democratic primary, Garver switched camps and went on to lead Obama’s Presidential Transition Agency Review Team for NASA.

The White House tapped Garver for the deputy administrator post well before it settled on its nominee for the top job. After members of Congress balked at the administration’s first choice, retired Air Force Maj. Gen. Scott Gration, Obama ultimately picked Bolden, a former space shuttle commander and retired Marine Corps major general. Bolden and Garver were formally nominated as package in May 2009, confirmed by the Senate two months later, and sworn in July 18, 2009, in a low-key ceremony at NASA headquarters.

The past four years have raised plenty of questions about who is truly calling the shots at NASA.

“Lori Garver has been the most influential deputy administrator in the history of the agency,” said Mike Gold, director of Washington operations for Bigelow Aerospace, the Las Vegas company building an inflatable storage module for the space station under a commercial agreement brokered by Garver. “In many ways she redefined the power and possibilities of the position.”

Even those on the opposite side of space policy debates with Garver readily acknowledged her outsize influence. Mark Albrecht, who served as the executive director of the National Space Council under President George H.W. Bush and advised Mitt Romney’s 2012 presidential campaign, called Garver “the clear administration leader for creating and sustaining commercial green shoots in space enterprise. … She has been a loyal and effective advocate for Obama administration space policies and clearly had significant influence in administration space policy development.”

Obama’s space policy came into sharp relief in 2010 when he canceled his predecessor’s Moon-bound Constellation program, which relied heavily on NASA’s heritage rocket hardware and traditional contractor base. Obama proposed refocusing NASA on developing “game-changing” technologies for deep-space exploration — starting with an asteroid visit by 2025 — while relying on entrepreneurial space ventures like SpaceX to slash the cost of sending cargo and crew to the space station.

Obama’s proposal received a cool reception from U.S. lawmakers, especially those heavily vested in the status quo. Lawmakers from Alabama, Florida and Texas — home to NASA’s traditional manned spaceflight centers — banded together on legislation directing NASA to build the Space Launch System heavy-lift rocket and an Orion Multi-Purpose Crew Vehicle optimized for deep-space missions. Both systems were envisioned under the Constellation program.

Scott Pace, a Romney adviser who left a senior NASA post in 2008 to become director of the Space Policy Institute at George Washington University here, said Garver — as the most visible face of Obama’s space policy — is not only blamed for canceling Constellation but for “creating a sharp and ongoing conflict” with a Congress that feels it has been repeatedly blindsided by NASA.

“That’s not totally her fault,” Pace said. “But certainly she’s a visible face and associated with that.”

“She planted seeds of change at an agency that badly needed to change, and in the process was very controversial,” said John Logsdon, the former Space Policy Institute director who has known Garver since she earned her master’s degree in science, technology and public policy under his tutelage. “One litmus test of how strongly the Obama White House is committed to the kind of change Lori was trying to put in place is whether they replace her with a deputy who shares those views.”

While there is no guarantee the White House will nominate a replacement — Goldin ran NASA for nearly a decade without a deputy — Garver said one of the reasons she is leaving now is to give the president time to put a successor in place.

“It does involve being able to leave at a time where there really can be a second deputy in the Obama administration,” Garver said. “There’s every indication that will happen.”

Whoever that happens to be will face the challenge of defending a commercial crew transportation initiative that has struggled to win full funding since its inception and convincing the public that sending astronauts to an asteroid — one that NASA, since April, has been planning to capture and relocate to lunar space — is a worthwhile goal for a world-class space program.

“I do hope that people recognize that I truly do care about those things I championed,” Garver said. “It’s true that … it doesn’t make you popular, but it’s something that’s worth doing. I’ve never shied away from stepping up and being able to defend those things that the administration and NASA set out to do.”

Some of the Names That Have Emerged as Possible Garver Replacements

Pam Melroy 

The second woman to command a space shuttle mission, Melroy joined the U.S. Defense Advanced Research Projects Agency, so she’s still in Washington and hasn’t given up on public service.

She was deeply involved in Columbia accident investigation and recovery efforts before finishing her five-year NASA stint as  chief of the Orion branch of the Astronaut Office. From there she went to Lockheed Martin as deputy program manager for space exploration initiatives.

Melroy spent the past two years at the Federal Aviation Administration’s (FAA) Office of Commercial Space Transportation  working closely with the very companies NASA is counting on to transport astronauts to and from the international space station.

Patti Grace Smith

The former longtime head of the FAA’s Office of Commercial Space Transportation and current member of the NASA Advisory Council is another strong candidate for the job. She knows the territory, supported President Barack Obama during his 2008 and 2012 campaigns, earning an appointment last year to the National Air and Space Museum’s advisory board.

Dave Radzanowski

Currently NASA’s chief of staff, Radzanowski knows the lay of the land and presumably has NASA Administrator Charles Bolden’s trust. Deputy administrator would be a good promotion for the former Office of Management and Budget branch chief. The White House, however, might want to use Radzanowski to fill the vacancy that will be left by NASA Chief Financial Officer Beth Robinson when she takes the Department of Energy’s No. 3 job.

Ann Zulkosky

The former marine biologist is the top Democratic aide on the Senate Commerce Committee, where she served as the point person for Sen. Bill Nelson (D-Fla.) in drafting the 2010 NASA Authorization Act that directed the agency to build the Space Launch System heavy-lift rocket.

Richard DalBello

Although he has not formally announced that he will be stepping down as vice president of legal and government affairs at Intelsat General Corp., it’s a poorly kept secret in Washington space circles that DalBello has been tapped to fill a vacancy at the White House Office of Science and Technology Policy (OSTP). What’s left some people scratching their heads is why DalBello would leave the private sector to take a relatively low-profile post he held from 1993 to 1997..

One possible explanation is that he’s not — the OSTP space and aeronautics post will be just a temporary gig that allows DalBello to ride herd on NASA while the nomination and confirmation process runs its natural course.

DalBello certainly has the right qualifications, knows everybody there is to know in space policy circles and has no obvious interest conflicts since he has spent the last eight years working for a firm that is not among NASA’s stable of contractors.

Brian Berger is editor in chief of SpaceNews.com and the SpaceNews magazine. He joined SpaceNews.com in 1998, spending his first decade with the publication covering NASA. His reporting on the 2003 Space Shuttle Columbia accident was...