If you would like to see more articles like this please support our coverage of the space program by becoming a Spaceflight Now Member . If everyone who enjoys our website helps fund it, we can expand and improve our coverage further.

Two cosmonauts living aboard the International Space Station plugged a small hole in the hull of a Soyuz ferry craft with gauze and sealant Thursday, stabilizing the air pressure inside the orbiting research outpost after engineers detected a minor leak.

Working inside the Soyuz MS-09 spacecraft docked with the station’s Earth-facing Rassvet module, cosmonauts Oleg Artemyev and Sergey Prokopyev sealed the 2-millimeter (0.08-inch) opening with a wipe saturated in an epoxy sealant, stemming what NASA described as a “minute pressure leak.”

Ground controllers detected the slight loss in air pressure around 7 p.m. EDT (2300 GMT) Wednesday, but they did not wake the crew after determining the station was in no immediate danger.

When the crew woke up at their normally-scheduled time Thursday, mission controllers directed them to search for the cause of the leak. After extensive checks, the station crew traced the leak to the orbital section of the Russian Soyuz MS-09 crew capsule, which ferried a Russian cosmonaut, a European astronaut and a NASA flight engineer to the orbiting complex in June.

The orbital module, at the forward end of the Soyuz spacecraft, provides a habitation area for the crew during the trip to the station, and is jettisoned before re-entry to burn up on the atmosphere. Station crews return to Earth inside a separate compartment of the Soyuz, the landing module.

Two Soyuz capsules are currently docked at the station. The Russian spaceships also serve as lifeboats to evacuate the station’s crew during an emergency.

Officials did not immediately say Thursday what caused the air leak, but it could have been created by a collision with a fragment of space junk or a micrometeoroid, or some type of malfunction inside the Soyuz capsule.

“Roscosmos (the Russian space agency) has convened a commission to conduct further analysis of the possible cause of the leak,” NASA said in a statement.

The cosmonauts covered the tiny hole with Kapton tape, then downlinked detailed endoscope imagery damage site to experts at Russia’s mission control center in Korolev, near Moscow, who recommended the crew apply an epoxy over the opening to seal it.

After some debate between NASA flight controllers, station commander Drew Feustel, and Russian engineers on the best way to plug the hole, the cosmonauts were directed by managers in Russia to use a strip of cloth saturated in a sealant on both sides.

Russian mission control instructed the crew to push the gauze into the hole, then tape the edges and let it settle and dry.

A few minutes after 1 p.m. EDT (1700 GMT), the cosmonauts radioed down to Earth that the hole was plugged. The crew reported a bubble where they applied the sealant, but they detected no further signs of a pressure leak when listening for the rush of air with a sensitive microphone.

Russian mission control then told the crew to stop their repair work for the rest of the day.

“It looks like it’s in a stable configuration now with a mixture of epoxy and a wipe — like a cloth wipe — partly in the hole and partly above the hole,” said European Space Agency astronaut Alexander Gerst. NASA’s spacecraft communicator at mission control in Houston radioed the crew that they saw stable air pressures inside the station after the cosmonauts applied the sealant.

“OK, sounds great,” Gerst replied. “If there is anything that you see that changes that, please let us know. Otherwise, we’ll just consider that as stable now.”

“We are not going to do anything else with it today,” a member of the Russian control team said through a translator. “Let it set, and then tomorrow we are going to run a leak check and everything else.

“Let it set first, let it solidify, then we’ll call you up tomorrow, and we will make a final decision on that tomorrow.”

“Work to restore the integrity of the ISS is complete,” tweeted Dmitry Rogozin, head of Roscosmos.

The station crew repressurized the atmosphere inside the research lab using air tanks aboard a Russian Progress supply freighter, replacing the air lost during the leak.

Email the author.

Follow Stephen Clark on Twitter: @StephenClark1.