When Neil Armstrong died in 2012, it was officially put down to complications arising from heart surgery. But seven years on, more murky circumstances have come to light.

The New York Times said Tuesday it had received by mail 93 pages of documents revealing a dispute between the family of the most famous astronaut in history and the small Ohio hospital where he was treated and operated on.

The Cincinnati Enquirer also received the documents, which were sent anonymously.

According to the newspapers, the family had threatened to publicly accuse the hospital of medical malpractice.

They ultimately reached a secret settlement that avoided a scandal, with the hospital paying $6 million, of which $5 million went to Armstrong's two sons, Rick and Mark, in exchange for their silence.

In a July 2014 email, Mark's wife Wendy, a lawyer, threatened to go public during the 45th anniversary of the Apollo 11 mission which saw Armstrong become the first person to set foot on the Moon.

"If this matter becomes public, the resulting damage to your client's reputation would come at a much greater cost than any jury verdict we can imagine," she wrote, according to the Cincinnati Enquirer.

"No institution wants to be remotely associated with the death of one of America's greatest heroes," Bertha Helmick, a lawyer for Armstrong's grandchildren, argued in probate court proceedings, according to the Times.

But Armstrong's widow Carol, his second wife, wanted it known she was not a part of the agreement.

The case concerned the decision by the hospital in Fairfield, Ohio, now a member of the Bon Secours Mercy Health group of hospitals, to not transfer Armstrong immediately to surgery when he began to show rapid internal bleeding, several days after a coronary bypass.

The original decision to perform the bypass surgery has also been questioned.

A hospital spokeswoman told the Enquirer the publication of the details was "very disappointing".

Read also: Neil Armstrong's Apollo 11 spacesuit unveiled at Smithsonian

Cashing in?

Settlements for medical malpractice suits are commonplace in the United States: only about five percent end up in court, according to Michelle Mello, a law professor at Stanford. Hospitals are insured against the risk.

According to Mello, the biggest settlement by a doctor in 2018 involving the death of a male in his 80s was for $1.49 million and the median was $145,000.

All such cases are reported to the National Practitioner Data Bank, but settlements by hospitals, which are rare, are not.

According to another expert, William Sage of the University of Texas at Austin, "a $6 million settlement involving the death of a national here does not strike me as unusually large."

The case highlights the brand value of the Armstrong name, but also more generally of astronauts from NASA's golden era.

When Armstrong's sons sold off thousands of personal items belonging to their father in three recent auctions, the proceeds exceeded $12 million, according to Heritage Auctions.

They told AFP in an interview last year they wanted to create a foundation and would donate a portion to charity.

Other Moonwalkers have also cashed-in.

Buzz Aldrin, who followed Armstrong on the Moon, commands a $50,000 to $75,000 fee to participate in conferences, according to the site speaking.com.

"He'll ask for a private jet, he'll ask for VIP accommodation, and he'll get it because people want to meet Buzz Aldrin," Francis French, the author of several books on space history including one on the crew of Apollo 15, who were reprimanded for trying to make money from the sale of autographed postmarked envelopes that were taken to the Moon.

According to French, it's no secret, and not considered underhanded, that ex-astronauts look for ways to make money after their careers are over. They would otherwise have to rely solely on their relatively paltry military or civil service pensions.

French added that he knew the Armstrong family, and they are not motivated by money.

Charlie Duke, one of the four living Moonwalkers, asked AFP in April for $5,000 for an interview.

"There's a market. They charge what they can get," John Logsdon, founder of the Space Policy Institute at George Washington University told AFP. "These guys risk their lives after all, and I see nothing wrong with them profiting from it."

In his own post-astronaut career, Armstrong lived a life outside of the limelight and less renumerated. If he used his fame, it was mainly for the benefit of his almamater, Purdue.

Thanks to a major fundraising campaign he co-chaired in the 1990s, Purdue raised $ 250 million, the university told AFP.