WASHINGTON — The U.S. Air Force appears to have cooled on a space architecture concept that entails distributing capabilities across a larger number of satellite platforms.

The philosophy, known as disaggregation, has been in vogue among U.S. Defense Department officials and in think tanks for years. Air Force and industry officials have viewed it as a major factor as the service plans its next-generation satellite programs.

Currently, U.S. national security space capabilities are heavily concentrated on large, multimission satellite platforms that some view as increasingly vulnerable to attack. Disaggregation theory holds that dispersing these capabilities will make them harder to target.

Just over 18 months ago, an Air Force Space Command white paper explained that idea: “Disaggregation is an innovative opportunity to stay ahead of our adversaries, to change their targeting calculus, and to mitigate the effects of a widespread attack on our space assets,” the report said. “In addition, resilience serves as a deterrent, which may be the best way to preserve our capability by avoiding an attack.”

But after an exhaustive review of the military space environment carried out last summer, known as the Space Portfolio Review, the Air Force appears to be leaning toward a broader theory informally known as “space protection.” The idea is to assure that the Defense Department and intelligence community can make use of their satellites at any time.

Lt. Gen. Ellen Pawlikowski, the military deputy to the assistant secretary of the Air Force for acquisition, told reporters here April 22 that disaggregation is now seen as just one element of a broader space-protection solution. Other ideas have emerged during the last three years as the service has analyzed options for next-generation satellite systems, and these ideas are now “playing out” as the studies continue, she said.

“I think there’s a recognition, there’s only so far you can go with”  disaggregation,  Pawlikowski said during a breakfast here. “It’s not the be-all, end-all answer.” She declined to discuss the other space protection concepts the service is studying, but said they include an “all-government” approach from multiple federal departments.

“When we think of how we’re going to protect space, there’s going to be some level of community protection the government is going to need to define,” Pawlikowski said.

Pawlikowski declined to detail how exactly the Air Force might protect its space capabilities against a growing array of threats, calling her speech “the G-rated” version of the Space Portfolio Review results. The Pentagon provided a full, “R-rated,” classified briefing to some Capitol Hill staffers earlier this year, she said.

The review formed the basis for what Pentagon officials say is a proposed $5 billion spending increase over the next five years for space protection activities. Pawlikowski said most of that proposed spending is on the classified side.

Pawlikowski said the Space Portfolio Review, which Defense Secretary Ashton Carter cited this year in his confirmation hearings, included participation from the Joint Chiefs of Staff, the National Security Council, the State Department and the White House.

Senior U.S. national security officials have upped their rhetoric in recent months about growing threats to U.S. space capabilities. Specifically, these officials have cited a nondestructive anti-satellite test by the Chinese in 2014, launches of suspicious-looking satellites by Russia and increased satellite jamming efforts.

Congressional staffers say the Pentagon has held more classified space briefings in the last year than at any time in the last decade.

An unclassified executive summary of the review, thought to be the most comprehensive examination at the space environment in a decade, was not immediately available.

Mike Gruss covers military space issues, including the U.S. Air Force and Missile Defense Agency, for SpaceNews. He is a graduate of Miami University in Oxford, Ohio.