An artist rendering of what NASA's Space Launch System rocket would look like. (Courtesy of NASA.)

The powerful new rocket NASA has been developing for years in its quest to get to the moon and Mars will require a massive amount of additional funding that would double the initial cost of the project to nearly $9 billion, according to a scathing government report released Wednesday.

NASA’s Office of the Inspector General found that Boeing, the main contractor, has already spent $5.3 billion on the rocket program and is expected to burn through the remaining contract funds by early next year, three years ahead of time and without delivering a single rocket stage.

The rocket also is suffering production delays, the IG found. The first flight of what’s known as the Space Launch System rocket and Orion spacecraft was supposed to be a test mission without astronauts by the end of last year, with the first crewed mission expected in 2021. But those launches have now been delayed by 2½ years and may be set back further, the report said.

The report is a slamming indictment for a program that for years has suffered delays and cost overruns and has been derided by critics as a “Senate Launch System” that serves more as a jobs program in key congressional districts.

Despite those setbacks, NASA and members of Congress have stood by the project, saying it is vital for the agency’s long-term goals to get humans into deep space.

During a recent tour of NASA’s rocket factory in New Orleans in August, Jim Bridenstine, the agency’s administrator, praised the project. “What we’re doing here is something that’s never been done before,” he said. “We’re launching the biggest rocket carrying the heaviest payload capacity that’s ever flown. It’s going to send our crew vehicles into deep space to areas we have never flown humans before. It’s a brand-new, very large project that is unmatched in the world and will remain unmatched for a very long time.”

In a statement, Boeing said “an unprecedented rocket program has inherent challenges. But it added the “program described in the OIG’s report does not represent the Space Launch System program today.”

Boeing has already implemented the recommendations from the report, the company said. The aerospace contractor said it has “restructured our leadership team to better align with current program challenges, and we are refining our approaches and tools to ensure a successful transition from development to production.”

A growing commercial space industry has made progress in building and flying rockets more efficiently than the government. Earlier this year, SpaceX, the firm founded by Tesla chief executive Elon Musk, launched its Falcon Heavy rocket, the most powerful rocket operating in the world. And Blue Origin, Jeffrey P. Bezos’s company, is also developing a powerful rocket called New Glenn. (Bezos owns The Washington Post.)

Both those rockets are reusable, meaning their booster stages fly back to Earth, either on land or on a ship at sea, so they can be used in other launches. The SLS, by contrast, would be used once, and its booster stage would fall into the ocean after its flight.

The increased competition could mean growing scrutiny for SLS.

“As the quiver of rockets the United States has continues to grow, whether they are private- or government-owned and -operated, there will be an increasing level of comparison about which rocket can do each mission, and for what cost,” said Phil Larson, a former SpaceX spokesman and now a dean at the University of Colorado Boulder’s College of Engineering.

The IG said NASA “lacks visibility” into the contracting costs of the program because Boeing has combined all its activities — the construction of two booster stages and the upper stage — into the same contract line number. As a result, the report, said “the agency is unable to determine the cost of a single core stage,” which makes it difficult to determine how much it should be spending on future stages.

The report also faulted NASA for “inflating” Boeing’s performance scores “leading to overgenerous award fees.” According to the report, “Boeing’s poor performance is the main reason for the significant cost increases and schedule delays.”

It said the company “consistently underestimated the scope of the work to be performed” and the staffing required to perform it. At one point, as Boeing tried to hire more staff, NASA increased funding by $10 million a month to pay for additional labor shifts. “However, despite the increased labor hours, the project’s schedule remains delayed,” the report said.

The SLS rocket grew out of an earlier NASA program known as Constellation under the George W. Bush administration. That program was ultimately killed by President Barack Obama after an independent commission found cost increases and schedule delays made it “unsustainable.”