MOSCOW -- On August 29, disturbing data from a Soyuz MS-09 spacecraft docked at the International Space Station (ISS) reached the mission control centers in Houston and Moscow. The shuttle was losing oxygen, flight operators noted, and pressure inside the cabins was dropping. None of the crew members on board -- three Americans, two Russians and a German -- could provide an explanation.
After a thorough search of the spacecraft, the astronauts traced the oxygen leak to a tiny hole, around 2 millimeters in diameter, located in the Russian section of the ship, the orbital compartment that is cast off before atmospheric reentry.
Working with flight controllers on the ground, they covered the hole using heat-resistant tape as a temporary fix. To stabilize oxygen levels, they connected the shuttle to another spacecraft docked at the station, the Progress 70, according to a NASA statement.
In the hours that followed, Russian crew members followed instructions from Moscow and stopped up the hole with a cloth saturated in epoxy. In the process, they noted existing traces of glue inside the hole, according to Russian media reports. Crew members agreed with mission control to wait for the seal to harden and take a day to devise a longer-term solution.
NASA was quick to issue a statement and call for calm. The leak on board the spacecraft was "tiny" and placed no lives at risk, the agency said on August 30. The Russian space agency Roskosmos, for its part, convened a commission to investigate the incident and ascertain responsibility.
News of the incident spread fast, with media reports speculating on the cause of the oxygen leak. Explanations cited by space-industry sources and Russian journalists ranged from collision with space debris, mostly likely a micrometeorite, to deliberate sabotage by a crew member.
A photo of the small hole, published by Russia's space agency, Roskosmos, appeared to show impact marks caused by attempts to insert a drill bit into the hull.
On September 3, Russian state news agency RIA Novosti cited reports that the hole was drilled by a worker at Energiya, the corporation that manufactures Soyuz rockets. Upon noticing the error, the employee allegedly plugged the hole with glue, which explained why it was discovered neither during preflight testing nor during the first two months of the space mission.
The MS-09 space shuttle had been docked at the ISS since June.
Within hours of the report's publication, Roskosmos head Dmitry Rogozin appeared before journalists. He said that investigators had discarded the chance of collision with space debris and were looking into the possibility of sabotage.
"There's clear evidence of tampering with the spacecraft's hull," Rogozin told journalists. "We're checking whether this was done on Earth. But there's another version, which we're not discounting: deliberate interference in space."
The search for the culprit is a "matter of honor" for Energiya, Rogozin added.
In an interview with the U.S. television network ABC from on board the ISS, station commander Drew Feustel pointedly dismissed claims of sabotage.
"I can unequivocally say that the crew had nothing to do with this on orbit," he said.
"We certainly don't want to ever see that happen again," he added. "And I hope the teams on the ground do proper due diligence in trying to solve this problem because the implications are enormous to the whole space program, not only to us in the U.S. but also in Russia and internationally for all the partners."
NASA has been reserved in its response.
In comments to RFE/RL, agency spokeswoman Stephanie Schierholz said NASA was awaiting the results of the Roskosmos probe.
"We work closely with our Russian partners to identify the source and the solution," she said, adding that the incident should not be seen as evidence that Russia-U.S. space cooperation was under threat.
"We've been able to maintain a successful relationship through all sorts of things," she added, citing almost two decades of bilateral cooperation on the ISS.
Roskosmos declined requests for comment until the agency's commission concludes its investigation.
With relations between Russia and the United States at their lowest since the Cold War, the space industry has remained one of few areas in which cooperation continues. American astronauts still rely on Russian spacecraft to get to the ISS, a dependence that's set to end in coming years.
Efforts by Space X and Boeing, the two companies NASA commissioned to develop U.S. space transportation, have met obstacles, and neither will be certified for regular flights until at least late 2019, according to a U.S. government report released in January. Nevertheless, Russia's prominent role in space exploration is under threat from aspiring players China, India, and Japan.
Compounding the woes of Russia's space industry is the drop in financing and the aging of equipment since the fall of the Soviet Union. Following a cut in funding announced by Prime Minister Dmitry Medvedev in March 2016, NASA's annual expenditure almost equals the Roskosmos budget for the next 10-year cycle.
Planned reforms to Roskosmos, which was restructured in 2015 amid efforts to revive the industry, have been slow to yield progress. In May 2015, following another in a series of rocket failures later tied to issues at Energomash, the state company that produces Proton rocket engines, Rogozin cited a "systemic crisis" in the space industry and pledged to make the necessary changes.
There's been little evidence of that, according to Ivan Moyseyev of the Institute of Space Policy, a Moscow-based think tank. In a telephone interview, Moyseyev ridiculed the notion that a crew member aboard the Soyuz MS-09 would endanger the lives of colleagues and placed the August 29 discovery in the broader context of declining production standards at Roskosmos.
"Measures are not being taken to improve discipline at production plants, and this has gone on for a long time," he said. "It's a general problem."
In the meantime, all appears calm aboard the Soyuz MS-09. On September 10, shuttle commander Sergei Prokopyev recorded a video from the affected section in which he showed viewers the hole at the center of the controversy and the substance used to seal it.
"Everything is calm. We live as always, in peace and friendship," he said, before signing off with a wide grin. "Huge cosmic greetings to you all."