NASA, Boeing ready for long-delayed, high-stakes Starliner test flight

Boeing’s Starliner spacecraft was hoisted on top of ULA’s Atlas 5 rocket May 4 at Cape Canaveral Space Force Station. Credit: United Launch Alliance

Running years late, Boeing’s Starliner crew capsule program is poised for a crucial unpiloted test flight to the International Space Station set for launch Thursday, a do-over of an abbreviated 2019 demo mission that has cost the aerospace contractor nearly $600 million.

The Starliner crew capsule is scheduled for liftoff on the Orbital Flight Test 2, or OFT-2 mission, from Cape Canaveral at 6:54 p.m. EDT (2254 GMT) Thursday on top of a United Launch Alliance Atlas 5 rocket.

ULA, Boeing, and NASA, which oversees the Starliner commercial crew contract, gave a green light Tuesday to proceed with final launch preparations. Managers convened for a launch readiness review and gave a “go” to press on with the mission.

The review “went really well,” said Steve Stich, NASA’s commercial crew program manager. “It was short. It was very clean. There are really no issues that ULA, Boeing, or NASA are working for the launch coming up.”

The test flight is intended to gather data and prove the readiness of Boeing’s Starliner spacecraft to transport astronauts to and from the space station. It’s a redo of the OFT-1 mission in December 2019, which was cut short by software woes that caused the Starliner capsule to burn through propellant shortly after launch.

Developed in a public-private partnership, the Starliner spacecraft will give NASA a second human-rated capsule capable of ferrying astronauts to and from the space station, alongside SpaceX’s Dragon spaceship, which launched with a crew for the first time in May 2020.

The problems on the 2019 flight prevented the Starliner spacecraft from reaching the space station, and Boeing commanded the capsule to re-enter the atmosphere and land in New Mexico two days later.

After rewriting parts of the Starliner software code and running it through more extensive testing, Boeing and NASA moved forward with preparations for the OFT-2 mission — a test flight added to the Starliner schedule at Boeing’s expense.

The spacecraft was rolled to the launch pad last August at Cape Canaveral atop its Atlas 5 rocket. But on the morning of the scheduled launch, tests revealed 13 stuck isolation valves in the Starliner propulsion system.

Boeing and NASA agreed to remove the Starliner from the Atlas 5 rocket and postpone the mission to investigate the valve problem. Boeing says testing showed corrosion inside the valves — caused by a chemical reaction between moisture, nitrogen tetroxide propellant, and the valves’ aluminum housing — caused the components to stick inside the plumbing on the spacecraft’s service module.

For the OFT-2 mission, engineers improved seals on the valves to prevent moisture intrusion, and added nitrogen purges to keep atmospheric humidity out of the propulsion system. Boeing also swapped the balky service module from last summer’s launch attempt with a brand new propulsion section, with a fresh set of valves and thrusters.

The company says it is considering design changes to the oxidizer isolation valves — potentially reducing the amount of aluminum in the valve housing — for future Starliner missions, but officials are “confident” in the mitigations introduced to prevent moisture intrusion before the OFT-2 launch.

Boeing took an accounting charge of $595 million to pay for the delays, rework, and the unplanned OFT-2 mission. NASA’s fixed-price contracts for the Starliner commercial crew program total about $5 billion, an arrangement where the government and contractor shared costs in developing the spacecraft.

NASA signed a similar, less expensive contract with SpaceX in 2014 for development, testing, and operations of the human-rated Dragon spacecraft. After running into its own series of shorter delays, SpaceX launched its first astronaut mission to the space station in 2020.

While Boeing has wrestled with delays on the Starliner program, SpaceX has notched seven crew missions on its fleet of reusable Dragon capsules — five for NASA and two for private customers.

Boeing’s contract with NASA covers the unpiloted OFT-1 and OFT-2 missions, and a Crew Flight Test that could blast off with a team of two or three astronauts late this year or early next year, assuming a successful outcome to the upcoming demo flight. After the test flights are accomplished, NASA has booked operational six crew rotation fights with Boeing using the Starliner spacecraft.

Mark Nappi, Boeing’s Starliner program manager, said the delays haven’t zapped the focus of the Starliner team.

“This is very difficult to build and develop and launch this type of vehicle, so they are laser focused on doing this right, and that’s really where their minds are,” Nappi said, adding that Boeing wants to make the program the “safest and best quality possible.”

“When we launch, we launch,” Nappi said.

With the launch readiness review complete, ULA’s ground team is preparing to roll the 172-foot-tall (52.4-meter) Atlas 5 rocket out of the 30-story Vertical Integration Facility at 10 a.m. EDT (1400 GMT) Wednesday. Two “trackmobile” units will carry the Atlas 5 and the Starliner spacecraft on rail tracks for the 1,800-foot (550-meter) journey from the VIF to pad 41 at Cape Canaveral.

Teams stacked the Atlas 5 rocket’s core stage, two strap-on solid rocket boosters, Centaur upper stage, and the Starliner capsule inside the VIF over last few weeks.

Once on the launch pad, the Atlas 5 and its mobile launch platform will be connected to auto couplers to load propellants into the rocket. Kerosene fuel will be pumped into the first stage Wednesday afternoon, setting up for the start of the launch countdown at 7:34 a.m. EDT (1134 GMT) Thursday.

The launch team will load cryogenic propellants into the Atlas 5 beginning early Thursday afternoon, followed by an extended hold. On future missions carrying astronauts, the crew members will board the Starliner spacecraft through the capsule’s hatch during the four-hour pause in the countdown.

The Starliner spacecraft set for launch Thursday on Boeing’s OFT-2 mission won’t have an astronaut crew on-board. An instrumented test dummy named for “Rosie the Riveter” from World War II sits in the commander’s seat on the spacecraft.

An instrumented anthropometric test device, named Rosie, inside the Starliner spacecraft. Credit: Boeing

The Starliner will also carry more than 500 pounds (227 kilograms) of food and other supplies for the seven-person crew on the space station, according to NASA. At the end of the mission, the spacecraft is slated to return to Earth with more than 600 pounds (272 kilograms) of cargo.

There’s a 70% chance of favorable weather for liftoff of the Atlas 5 rocket with the Starliner spacecraft Thursday. The primary weather concerns are associated with thunderstorms that could fire up west of Cape Canaveral. Anvil clouds at the top of the storm cells could blow back toward the launch site, creating a threat of lightning that could be triggered by the rocket as it climbs through the atmosphere.

On Friday, the backup launch opportunity, there is a 40% chance of good weather for launch, with higher chances of thunderstorms in the launch pad area.

The Starliner team will also assess wind and sea conditions along the Atlas 5’s flight corridor northeast from Cape Canaveral. The capsule could splash down in the Atlantic Ocean along the offshore flight path if an emergency triggers a launch abort, in which the Starliner’s abort engines would propel the ship away from the Atlas 5 rocket.

The capsule’s launch abort system will be active for the first time on the OFT-2 mission. It operated in a “shadow” mode on the OFT-1 launch in 2019, collecting data for analysis by engineers after the flight.

For a Starliner mission with astronauts on-board, the abort weather constraints would factor in to the decision on whether to proceed for a launch. On this unpiloted test flight, teams will monitor the conditions but would not hold the launch if they were out of limits.

If the OFT-2 mission doesn’t take off Thursday, the next opportunity to launch would be Friday at 6:31 p.m. EDT (2231 GMT). The launch times are determined by when Earth’s rotation brings the launch pad at Cape Canaveral under the space station’s flight path.

After liftoff, the Atlas 5’s two strap-on boosters and Russian-made core engine will generate 1.6 million pounds of thrust to send the Starliner spacecraft toward space. Once their roles are complete, the boosters and core stage will jettison to fall into the Atlantic, leaving two hydrogen-fueled RL10 engines on the Centaur upper stage to propel the Starliner spacecraft on an arcing trajectory just shy of the velocity required to enter a stable orbit around Earth.

The Atlas 5 is programmed to fly a flatter, less steep trajectory that it flies on typical satellite delivery missions, increasing opportunities for the Starliner crew capsule to safely escape from the rocket in the event of a failure.

Once it is flying free of the Centaur upper stage, the Starliner’s four on-board maneuvering will finish the work of placing the spacecraft into orbit with a burn about 31 minutes after liftoff. That burn is the first of multiple engine firings to guide the Starliner spacecraft toward an automated docking at the space station’s Harmony module.

The orbital linkup is scheduled for 7:10 p.m. EDT (2310 GMT) Friday, assuming the OFT-2 mission takes off Thursday.

The astronauts on the space station will open hatches and enter the Starliner spacecraft Saturday, remove the cargo inside the pressurized crew cabin, and perform communications checkouts in the cockpit.

If all goes according to plan, and assuming good weather at the landing zone, the Starliner would undock from the space station May 25 and head for re-entry, targeting a parachute-assisted, airbag-cushioned touchdown at White Sands Space Harbor in New Mexico.

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