
Undocking at 6:04 PM, target landing time of 12:03 AM
NASA has announced its mission timeline for the Boeing Starliner spacecraft to depart from the International Space Station (ISS) and return autonomously to Earth on Friday.
After what was supposed to be a weeklong test flight to the ISS turned into an eight-month stay for two astronauts, it became a public-relations fiasco for Boeing. The Starliner experienced helium leaks and thruster malfunctions during the trip to the space station. Since their launch on June 5, NASA astronauts Barry “Butch” Wilmore and Sunita “Suni” Williams have been staying on the ISS alongside the Expedition 71 crew.
In August, NASA announced that the crew would return to Earth using the SpaceX Dragon spacecraft in February. Although it’s rare for missions to be extended due to unforeseen factors, the astronauts won’t be the first to return in a different spacecraft than the one they launched from.
During Starliner’s return, the performance of the craft’s systems will be closely monitored. Of specific concern are the four aft-facing attitude-control thrusters of the service module, which temporarily stopped working during the initial docking attempts. (A fifth malfunctioning thruster has been determined to be unusable for the remainder of the mission.)
The undocking is scheduled for 6:04 p.m. EDT, with a target landing time of approximately 12:03 a.m. EDT on Saturday, Sept. 7.
Starliner returns to Earth
NASA’s mission timeline, posted on Thursday, states that safety and mission success remain top priorities for teams during Starliner’s return.
As the first American capsule designed to land on solid ground, Starliner has a variety of available landing locations within the White Sands Missile Range in New Mexico, as well as in Willcox, Arizona, and the Dugway Proving Ground in Utah. Additionally, Edwards Air Force Base in California is available as a contingency landing site.
NASA analyzes weather predictions for different landing sites, considering factors such as winds, ground temperatures, cloud ceiling height, visibility, precipitation, and nearby storms. After undocking from the ISS, the Starliner spacecraft is expected to reach its landing site in as little as six hours, propelled gently by springs.
NASA has adjusted the planned series of thruster firings for Starliner’s departure from the ISS in an effort to reduce the use of the aft-facing thrusters. Steve Stich, the manager of NASA’s commercial crew program, explained in a press conference on September 4th that after undocking, the thrusters will be used in brief bursts to move the craft away from the station in what NASA refers to as a “breakout burn.” This simplified flight profile will slightly raise Starliner’s orbit, positioning it in front of the station and then above and behind it at a safe distance, in preparation for its deorbit burn.
Before the deorbit burn, a final weather check will take place. According to NASA’s mission timeline, winds must be at or below 10 mph (16 km/h). If winds exceed these limits, the deorbit burn will be postponed, and Starliner will aim for another landing attempt between 24 and 31 hours later.
Assuming the weather is favorable, Starliner will initiate its deorbit burn, lasting approximately 60 seconds, to decelerate and reenter Earth’s atmosphere for landing at its target site.
The deorbit burn will be the biggest test for the mercurial thrusters. The main burn will be conducted by a separate system, the Orbital Maneuvering and Attitude Control (OMAC) engines. However, the aft-facing thrusters will be used to help maintain the spacecraft’s attitude during the burn. Stich stated, “We’re going to let those thrusters fire as needed. We’ll use the thrusters judiciously when close to the station and save them for the deorbit burn at the very end of the flight, when we need them the most.”
Immediately after the deorbit burn, the spacecraft will reposition for service module disposal, which will burn up during reentry over the southern Pacific Ocean.
Reentry will see the capsule reach temperatures of up to 3,000 degrees Fahrenheit (1,650 degrees Celsius), which may interrupt communications with the spacecraft for approximately four minutes. After this, the forward heat shield on top of the craft will be jettisoned and several parachutes will be deployed at 30,000 feet (9,140 meters).
As the capsule continues to slow down, the base heat shield will jettison at 3,000 feet (900 meters) and cause six landing bags to inflate. The spacecraft will be traveling at approximately 4 mph (6.4 km/h) at touchdown.
Recovering Starliner
After landing, several NASA and Boeing teams near Starliner’s landing site will approach the spacecraft to carry out recovery procedures, according to NASA’s timeline.
- The gold team will use equipment to detect any hypergolic fuels that may not have fully burned off before re-entry and will also cover the spacecraft’s thrusters.
- The silver team will then electrically ground and stabilize the Starliner capsule.
- The green team will supply power and cooling to the crew module since the spacecraft will be powered down.
- The blue team will then document the recovery for public relations and future process review.
- The red team — which includes Boeing fire rescue, emergency medical technicians, and human factors engineers — will then will open the Starliner hatch.
The teams will commence unloading time-critical cargo from Starliner. Subsequently, the spacecraft will be relocated to Boeing facilities at NASA’s Kennedy Space Center in Florida for refurbishment.
NASA’s official timeline
As NASA and Boeing prepare to return the company’s Starliner spacecraft uncrewed from the International Space Station to Earth, safety and mission success remain as top priorities for the teams. Mission managers will complete a series of operational and weather checks before the spacecraft undocks from the orbital complex.
The Starliner spacecraft is the first American capsule designed to touch down on land, supporting expedited astronaut and cargo recovery on future missions and to aid the company in spacecraft refurbishment. For Starliner missions, NASA and Boeing will use potential landing locations in the White Sands Missile Range, New Mexico; Willcox, Arizona; and Dugway Proving Ground, Utah. Edwards Air Force Base in California also is available as a contingency landing site.
Twenty-four hours before undocking, NASA analyzes weather predictions for the various landing sites. Winds at the selected landing site must be 6 mph (approximately 6 knots) or less when flying with crew, and approximately 13 mph (12 knots) or less when uncrewed. Ground temperatures must be warmer than 15 degrees Fahrenheit, and the cloud ceiling must be at least 1,000 feet. One nautical mile of visibility is required, and the area must be clear of precipitation, thunderstorms, and lightning within approximately a 22-mile (35-kilometer) radius.
When teams proceed with undocking, Starliner will complete a series of departure burns, allowing it to reach its landing site in as little as six hours. A final weather check also occurs before the spacecraft’s deorbit burn. Winds must be at or below 10 mph (9 knots). If winds exceed these limits, teams will waive the deorbit burn, and Starliner will target another landing attempt between 24 and 31 hours later.
Once clear to proceed, Starliner executes its deorbit burn, which lasts approximately 60 seconds, slowing it down enough to re-enter Earth’s atmosphere and committing the spacecraft to its targeted site. Immediately after the deorbit burn, Starliner repositions for service module disposal, which will burn up during re-entry over the southern Pacific Ocean.
Following service module separation, the command module maneuvers into re-entry position. During re-entry, the capsule experiences plasma buildup – reaching temperatures up to 3,000 degrees Fahrenheit – that may interrupt communications with the spacecraft for approximately four minutes.
Once Starliner re-enters Earth’s atmosphere, the forward heatshield – located on the top of the spacecraft – is jettisoned at 30,000 feet, exposing the two drogue and three main parachutes for deployment. The parachutes will continue to slow the spacecraft down as the base heatshield is jettisoned at 3,000 feet, allowing the six landing bags to inflate. At touchdown, the spacecraft is traveling at approximately 4 mph.
The NASA and Boeing landing and recovery team is stationed at a holding zone near Starliner’s intended landing site. After landing, a series of five teams move in toward the spacecraft in a sequential order.
The first team to approach the spacecraft is the gold team, using equipment that “sniffs” the capsule for any hypergolic fuels that didn’t fully burn off before re-entry. They also cover the spacecraft’s thrusters. Once given the all-clear, the silver team moves in. This team electrically grounds and stabilizes Starliner before the green team approaches, supplying power and cooling to the crew module since the spacecraft is powered down.
The blue team follows, documenting the recovery for public dissemination and future process review. The red team, which includes Boeing fire rescue, emergency medical technicians, and human factors engineers, then proceed to Starliner, opening the hatch.
The landing and recovery team begins unloading time-critical cargo from Starliner. The spacecraft is then transferred to Boeing facilities at NASA’s Kennedy Space Center in Florida for refurbishment ahead of its next flight.
NASA’s Commercial Crew Program is working with the American aerospace industry through a public-private partnership to launch astronauts on American rockets and spacecraft from American soil. The program’s goal is to provide safe, reliable, and cost-effective transportation on space station missions, which will allow for additional research time. The space station remains the springboard to NASA’s next great leap in space exploration, including future missions to the Moon and, eventually, to Mars.