Chinese capsule damaged by space-junk strike returns to Earth (video)

The first emergency operation in the history of China's human spaceflight program came to an end on Monday (Jan. 19) when an uncrewed Shenzhou 20 capsule parachuted into the Dongfeng landing site in north China's Inner Mongolia Autonomous Region.

The spacecraft had spent 270 days in orbit, docked for nine months to the country's Tiangong space station.

And that wasn't the plan.

Delayed due to damage from a space-junk strike

Shenzhou 20's original return date had been delayed due to concerns over tiny cracks found in the craft's viewport window. That damage was thought to be caused by a strike by space debris.

On-site inspection of the returned capsule on Monday found that its exterior was "generally normal" and the items secured inside the vessel were in good condition, the China National Space Administration (CNSA) said.

The recovery crew quickly took steps to protect the damaged porthole on the return capsule upon its touchdown on terra firma. That action was driven by the need for post-landing assessment work about the damage the Shenzhou 20 capsule suffered in space.

Emergency mission

The Shenzhou 20 incident sparked an emergency mission to launch the uncrewed Shenzhou 22 spacecraft to Tiangong on Nov. 24. Now docked to the orbiting facility, that vehicle will serve the currently orbiting Shenzhou 21 crew on their expected return at the conclusion of their six-month mission later this year.

The Shenzhou 20 crew returned to Earth on Nov. 14 aboard the Shenzhou 21 capsule, after Chinese space officials deemed it too risky to fly them down on the damaged Shenzhou 20 spacecraft.

"Furthermore, in conjunction with the emergency launch of the Shenzhou 22 spacecraft, a porthole crack repair device was expedited and sent to the launch site," CNSA officials said. "Astronauts installed it inside the Shenzhou 20 capsule, effectively improving the spacecraft's heat protection and sealing capabilities during reentry."

Unique factors

The state-run China Central Television (CCTV) reported that Xu Peng, the on-site commander at the Shenzhou 20 capsule touchdown site, said that this return to Earth was unique in a number of ways.

"This marks the first time the Dongfeng Landing Site has carried out a spaceship recovery mission during the coldest season of the year, with cold weather posing a test for both our search and rescue teams and equipment," Xu said. "We made special cold-protection preparations in advance to ensure that both personnel and the equipment remained in good condition throughout the mission."

Xu also noted another unique factor of this uncrewed return recovery operation: Ground recovery teams made use of new capsule recovery methods, such as drones and other high-tech equipment.

"Adjustments were made to our recovery forces," Xu said. "The helicopter unit did not participate in this mission, and the drone and unmanned ground vehicle units made their debut. This new model, combining unmanned search equipment with ground personnel, was applied in the recovery of the uncrewed capsule."

Landing parachute

Furthermore, Xu added that, as the Shenzhou 20 return capsule came down without astronauts, there was no onboard crew member to manually separate the landing parachute.

"As a result, the main parachute did not automatically detach upon landing, and in strong winds, it could have dragged the return capsule along the ground. This requires our ground personnel to reach the landing point and cut the parachute as quickly as possible," Xu said.

One of the items carried in the uncrewed Shenzhou 20 capsule was a retired spacewalking spacesuit. That spacesuit was used for more than four years in orbit, far exceeding its original design life, reported CCTV. Over that time, the suit had supported 11 Chinese astronauts across eight crewed missions, enabling 20 successful spacewalks to be conducted.

Heated discussions

The Shenzhou 20 crew inspected their vehicle after it sustained damage in orbit. They observed that the porthole had an unexpected mark on the edge of the outermost glass — a triangular shape, about two centimeters long, according to a report by the state-run Xinhua news agency.

The Shenzhou capsule porthole consists of three layers of glass. "The outermost layer is a heat-resistant window, which can withstand the high-temperature ablation caused by the spacecraft's high-speed motion and intense friction with the air during its reentry into the atmosphere," the Xinhua report stated.

"The middle layer is a pressure-bearing window, and the inner layer is a protective window, which can ensure the airtightness of the cabin and the stability of the spacecraft's structure, but their heat resistance is less than half that of the heat-resistant window," reported Xinhua.

A Shenzhou 20 "Problem Analysis and Safety Assessment Report" was written based on laboratory tests that addressed a key question: Can a cracked heat shield withstand the extreme environment of atmospheric reentry? The consensus? "Life comes first, and safety comes first."

Rolling backup mode

Since the Shenzhou 12 mission, China's human spaceflight program has adopted a "rolling backup mode" of "one launch, one backup."

But, as noted in the Xinhua report, that "standby" spacecraft mode has never actually been needed. "This time, the standby status unexpectedly turned into emergency combat, and the tests followed one after another," Xinhua reported.

Actions taken — from the crew report, followed by ground worry and appraisal, to launch of the uncrewed Shenzhou 22 — was completed in 16 days.

Meanwhile, a Shenzhou 23 spacecraft has arrived at China's Jiuquan Satellite Launch Center, and its Long March 2F Y23 booster is about to be shipped, the CNSA pointed out.

"With the return of the Shenzhou 20 spacecraft, the main tasks of this emergency space operation for the Chinese space station have been successfully completed," CNSA officials stated.