US President Donald Trump's Space Force, a new military department dedicated to fighting war in space, would cost the Pentagon between US$1.5 to US$2.7 billion ($4bn) in additional money over five years.
That's according to a study released this week by the Centre for Strategic and International Studies, a Washington think-tank.
That estimate is far below the US$13bn price tag that Air Force Secretary Heather Wilson recently reported to Pentagon leaders and is certain to continue to fuel the debate over the cost and necessity of what would become the first new military service branch since the Air Force was created in 1947.
While the White House has pushed aggressively for the establishment of the Space Force, which Trump has championed in rallies, a new military department would need to be approved by Congress.
It is unclear whether there is enough support for it to pass.
Many in the Pentagon, including Defence Secretary Jim Mattis, initially said they were against the idea.
Leaders of the Air Force, which now runs most of the Pentagon's space operations and would have the most to lose if a new service were to be created, also came out against the proposal.
Speaking last week at a conference held by DefenceOne, Wilson said the US$13bn estimate "was the cost of a fully fledged, stand-alone department and also a unified combatant command".
But she added that the level of funding would ultimately be dictated by the legislation proposed by the White House. "The costs will be really based on what are the elements in the model in that proposal," she said.
Last week, Deputy Defence Secretary Patrick Shanahan told reporters that the cost to create a Space Force would be much lower than that, possibly as little as US$5bn, which is closer to the think-tank's estimate.
In presenting the report, Todd Harrison, a defence analyst at the Centre for Strategic and International Studies, said that the Space Force would mostly pluck people from across various departments in the Pentagon who work on space issues and gather them under a new department.
"Most of this is a simple matter of reorganisation," he said. "I don't think cost should have a big factor in [Congress'] decisions. I think a bigger factor is whether or not you think it is needed."
Harrison estimated that the annual budget of a Space Force would be about US$21.5bn, which is more than the Coast Guard's US$11.7bn budget but less than that of the Marine Corps, US$29.2bn.
Its total work force would be less than 50,000 - or about the same size of the Coast Guard.
NASA ORDERS SAFETY REVIEW
Nasa has ordered a safety review of the two companies it has hired to fly astronauts to the International Space Station, a months-long assessment that would involve hundreds of interviews designed to assess the culture of the workplaces, the agency said.
The review, to begin next year, would look at both Boeing and SpaceX, the companies under contract to fly Nasa's astronauts, and examine "everything and anything that could impact safety" as the companies prepare to fly humans for the first time, William Gerstenmaier, Nasa's associate administrator for human exploration, said.
The review was prompted by the recent behaviour of SpaceX's founder, Elon Musk, according to three officials with knowledge of the probe, after he took a hit of marijuana and sipped whiskey on a podcast streamed on the Internet.
That rankled some at Nasa's highest levels and prompted the agency to take a close look at the culture of the companies, the people said.
Nasa spokesman Bob Jacobs declined to comment on what prompted the review. But in a statement, he said it would "ensure the companies are meeting Nasa's requirements for workplace safety, including the adherence to a drug-free environment".
Nasa Administrator Jim Bridenstine said in an interview that the agency wants to make sure the public has confidence in its human-spaceflight programme, especially as the companies are getting closer to their first flights, scheduled for next year.
"If I see something that's inappropriate, the key concern to me is what is the culture that led to that inappropriateness and is Nasa involved in that," he said.
"As an agency we're not just leading ourselves, but our contractors as well. We need to show the American public that when we put an astronaut on a rocket, they'll be safe."
SpaceX said in a statement that "human spaceflight is the core mission of our company. There is nothing more important to SpaceX than this endeavour, and we take seriously the responsibility that Nasa has entrusted in us to safely and reliably carry American astronauts to and from the International Space Station."
The company noted that it has worked alongside Nasa for years. And that it "actively promotes workplace safety, and we are confident that our comprehensive drug-free workforce and workplace programs exceed all applicable contractual requirements."
Boeing said in a statement that its corporate culture "ensures the integrity, safety and quality of our products, our people and their work environment. As Nasa's trusted partner since the beginning of human spaceflight, we share the same values and are committed to continuing our legacy of trust, openness and mission success."
So far this year SpaceX has launched 18 times - tying its record from last year - and says it is getting close to launching Nasa's astronauts.
The companies are working towards flying crewed missions from US soil for the first time since the space shuttle was retired seven years ago. Russia's Soyuz spacecrafts are used to transport astronauts.
In 2014, Nasa awarded contracts - US$4.2bn to Boeing and US$2.6bn SpaceX - to fly its astronauts under what is known as the Commercial Crew Programme.
Since then, the companies have faced setbacks and delays as they work to develop their spacecraft.
Twenty years ago today, construction began on the greatest international science & engineering project in human history - the @Space_Station. We marked the occasion by talking to the crew currently living & working in space. Take a look: https://t.co/NjT9U5TIfD #SpaceStation20th pic.twitter.com/Czq8KfCLWc
— NASA (@NASA) November 21, 2018
Earlier this year, Boeing had a propellant leak during a test of its emergency abort system. A safety advisory panel also found recently that Boeing still has a number of key tests that it has not yet completed, included tests of its spacecraft's heat shield and parachute systems.
It also found that SpaceX is struggling with "difficulties and problems" with the spacecraft's parachute system. "Clearly crew cannot be risked without complete confidence in the parachute design," the panel found.
Given the problems both companies are facing, the panel concluded their schedules to fly crews "have considerable risk and do not appear achievable given the number of technical issues yet to be resolved."
Those technical issues are separate from the safety review.
And SpaceX said it has made real progress in the development of the version of its Dragon spacecraft that is designed to fly humans.
SpaceX is planning to a launch its spacecraft without crew in January and plans to fly with astronauts on board by June 2019.
Boeing has said its first flight without crew would be in March 2019, and with astronauts by the following August.
NASA spacecraft's journey to Mars comes down to the final six minutes. Read and watch: https://t.co/JXWBlaP7HA pic.twitter.com/ILbS8hxdtd
— AP Health & Science (@APHealthScience) November 21, 2018
More than 60 fighter jets hit alleged missile production sites in Tehran.