WASHINGTON — President Trump on Tuesday signed Space Policy Directive 4 at the Oval Office flanked by Vice President Mike Pence and top officials from across the national security establishment.

SPD-4 gives the Pentagon the official go-ahead to send a proposal to the White House recommending the establishment of a separate military branch for space. During the signing ceremony, Trump said a military branch for space is long overdue and “should have been done sooner. … We need it.”

Trump called the Space Force a “national security priority” as adversaries train their forces and develop technology to “undermine our security in space, and they’re working very hard at that.”

DoD has drafted a legislative blueprint to centralize military space activities under a Space Force that would be embedded within the Department of the Air Force. It will submit that document, along with a budget request to the Office of Management and Budget for approval before they are sent to Capitol Hill. It will be up to Congress to review the proposal and pass  legislation to authorize the creation of a new military service under Title 10 of the U.S. Code.

Pentagon spokesman Charles Summers said in a statement that DoD will deliver the legislative proposal “within the coming weeks.”

The U.S. Space Force would include uniformed and civilian personnel from all military departments. According to SPD-4, it will “assume responsibilities for all major military space acquisition programs; and create the appropriate career track for military and civilian space personnel across all relevant specialties — for example, operations, intelligence, engineering, science, acquisition and cyber.”

The administration wrote SPD-4 as a high-level policy memo, very light on details, leaving most of the nitty gritty planning to DoD’s legislative proposal and many specifics to be hashed out over the coming months by DoD and the congressional defense committees.

A senior administration official said Trump believes there is bipartisan support in Congress to do this. “Our priorities are clear,” the official said on Tuesday during a conference call with reporters. “I think there’s a lot of commonality on both sides of the aisle. And I am hoping that this is not a very heavy lift for everyone. It is an issue that has been around for a long while.”

In a statement following the signing of SPD-4, Rep. Mac Thornberry (R-Texas), ranking member of the House Armed Services Committee, noted that his committee “led the way in passing a similar measure several years ago, so this proposal has a record of attracting bipartisan support in Congress.”

But many fine points about how the Space Force will be staffed and how it will operate as the sixth branch of the armed forces have yet to be decided and could take years to sort through.

Up until about two months ago, Trump had been insistent that the Space Force should be a separate military department even though its size would be far smaller than any of the other branches of the military. Many lawmakers from both sides said they would not support a new department and DoD officials worried that the administrative costs would ensure the proposal would die on arrival.

SPD-4 does not kill the idea of a separate department but defers it to a later time, after the Space Force has a chance to mature as a service. “What we don’t want to do is do it all at once,” the senior administration official said. If the White House had pressed for a separate department, he said, “we would spend a lot of time dealing with bureaucracy and structure and not focusing on warfighting. We decided to leverage the capabilities and the expertise that is already resident in the Air Force.”

An Air Force spokesman said that if the draft legislative proposal is enacted, “it will be our responsibility to deter and defeat threats in space through the U.S. Space Force, which will organize, train, and equip military space forces.”

But while the Air Force has owned the space mission and has the technical expertise, it still faces enormous political and logistical challenges organizing a new branch that has to be independent and will have to be staffed with members from other services who must be qualified for space-related work.

“Personnel issues are critical,” the senior administration official said. “People in the space business tend to be very highly trained and specialized.” Key personnel issues are being addressed in the legislative proposal, which will suggest a process to transfer service members from other branches to the Space Force. “We’ll focus on the headquarters functions to begin with,” he said. So the Space Force initially would be a few dozen people and then would grow over time. “I think it will be probably fairly heavy with people with advanced technical backgrounds,” the official said. “But also we need people with strong warfighting skills. .. We’ll establish a framework in the legislative proposal and then move things gradually over  a number of years.”

The administration is pressing DoD to come up with a plan to delegate authorities down to space operators on the ground so they can make decisions in the face of incoming threats. Operational authorities for space operations are managed at a strategic level like nuclear command and control. “Space now is a much more dynamic environment,” the official said. “We  need to be able to respond faster.” The administration wants to delegate authorities to the lowest level possible to respond to urgent threats, he said. “We want to put more responsibilities with satellite operators, squadron commanders in the field who can take action and don’t have to wait for Washington if there’s an imminent threat.”

The details of how to do that can get very complicated, he noted, “so we want DoD to come back to us with some proposals so we can delegate authorities as we have in other commands.”

Sandra Erwin writes about military space programs, policy, technology and the industry that supports this sector. She has covered the military, the Pentagon, Congress and the defense industry for nearly two decades as editor of NDIA’s National Defense...