Boeing’s Starliner capsule poised for second try at first astronaut flight

NASA and Boeing officials are ready for a second attempt to launch the first crew test flight on the Starliner spacecraft Saturday from Cape Canaveral Space Force Station, Florida.

Liftoff of Boeing's Starliner, capsuled atop a United Launch Alliance Atlas V rocket, is set for 12:25 pm EDT (16:25 UTC). NASA commander Butch Wilmore and pilot Suni Williams, both veteran astronauts, will take the Starliner spacecraft on its first trip into low-Earth orbit with a crew on board.

You can watch NASA TV's live coverage of the countdown and launch below.

The first crew flight on a new spacecraft is not an everyday event. Starliner is the sixth orbital-class crew spacecraft in the history of the US space program, following Mercury, Gemini, Apollo, the space shuttle, and SpaceX's Crew Dragon. NASA signed a $4.2 billion contract with Boeing in 2014 to develop Starliner, but the project is running years behind schedule and has cost Boeing nearly $1.5 billion in cost overruns. SpaceX, meanwhile, won a contract at the same time as Boeing and started launching astronauts on the Crew Dragon four years ago this week.

Now, it is finally Starliner's turn. A successful crew test flight would set the stage for six operational Starliner flights to ferry astronauts to and from the International Space Station (ISS).

Assuming the test flight gets off the ground Saturday, the spacecraft is due for docking at the ISS at 1:50 pm EDT (17:50 UTC) Sunday to begin a stay of at least eight days. Once managers are satisfied the mission has achieved all its planned test objectives, and pending good weather conditions in Starliner's landing zone in the western United States, the spacecraft will depart the station and return to Earth for a parachute-assisted touchdown. If the mission takes off on Saturday, the earliest nominal landing date would be Monday, June 10.

Wilmore and Williams have been here before. On May 6, the astronauts were strapped into their seats inside Starliner's cockpit awaiting takeoff on a flight to the International Space Station. A valve malfunction on the Atlas V rocket prevented launch that day, and officials subsequently discovered a helium leak on Starliner's service module that delayed the mission until this weekend.

Flying as-is

After weeks of reviews and analysis, managers determined Starliner is safe to fly as-is with the leak. The spacecraft uses helium gas to pressurize its propulsion system and push hydrazine and nitrogen tetroxide propellants from internal tanks to the capsule's maneuvering thrusters.

"When we looked at this problem, it didn’t come down to trades," said Mark Nappi, Boeing's vice president and program manager for Starliner. "It came down to: Is it safe or not? And it is safe, and that is why we determined that we can fly with what we have."

Ground teams traced the leak to a flange on one of four doghouse-shaped propulsion pods around the perimeter of the Starliner spacecraft's service module. In a worst-case scenario, if the condition grew worse during the flight, ground controllers could isolate it by closing the manifold feeding the leak. If the leak doesn't worsen, engineers are confident they can manage it with no major impacts to the mission.

"We looked really hard at what our options were with this particular flange," said Steve Stich, manager of NASA's commercial crew program, which oversees the agency's contract with Boeing. The flange has a helium conduit and lines for the spacecraft's toxic fuel and oxidizer, which makes a repair "problematic," Stich said.

Starliner commander Butch Wilmore and pilot Suni Williams arrived back at NASA's Kennedy Space Center earlier this week to prepare for launch.

Credit: NASA/Cory Huston

In order to safely fix the leak, which officials believe is likely caused by a defective seal, ground teams would have to disconnect the capsule from the Atlas V rocket, take it back to a hangar, and drain its propellant tanks. This would probably push back the long-delayed Starliner test flight until late this year.

But the leak is relatively small and stable. "It’s about a half-pound per day out of 50 pounds of total capability in the tank," Stich said.

“In our case, we have margin in the helium tank, and we’ve looked really hard to understand that margin and to understand the worst cases, and we took the time to go through that data," Stich said. "We really think we can manage this leak, both by looking at it before the launch, and then if it got bigger in flight, we could manage it."

Starliner’s flight plan

ULA rolled the Atlas V rocket and Starliner spacecraft back to its launch pad Thursday at Cape Canaveral, following several weeks inside the company's Vertical Integration Facility just south of the pad. Earlier in the week, Wilmore and Williams flew back to Kennedy Space Center from their training base in Houston, where they waited for NASA and Boeing officials to complete their probe into the helium leak.

The launch countdown will begin early Saturday, at 1:05 am EDT (05:05 UTC), with the power-up and initial checkouts of the Atlas V rocket. ULA will begin loading cryogenic liquid hydrogen and liquid oxygen propellants into the Atlas V shortly after 6:30 am EDT (10:30 UTC). Kerosene fuel for the Atlas V's first stage engine is already loaded aboard the rocket.

While ULA fuels the Atlas V, Boeing engineers will activate and pressurize Starliner's propulsion system around 8 am EDT (12:00 UTC). At this point, the ground team will check the spacecraft's helium leak rate to ensure it hasn't changed.

"If it has changed, we can go isolate the manifolds and then take a look at this specific manifold and understand the leak rate there," Stich said. "We've got criteria in place that says when we’d stop and talk about it or whether we were ready to go fly."

Once the Atlas V is fully fueled, managers will give a "go" for Wilmore and Williams to travel from NASA's crew quarters to the launch pad at around 9:05 am EDT (13:05 UTC). Wearing solid blue pressure suits, the astronauts will ride in a modified Airstream touring coach. Once at the pad, Wilmore and Williams will take an elevator up the tower to climb into their seats at the top of the 172-foot-tall (52.4-meter) Atlas V rocket.

The launch pad crew will close the hatch to the Starliner capsule around 11:15 am EDT (15:15 UTC), then evacuate the launch site. After a pressure check of Starliner's crew cabin, the launch pad's crew access arm will retract away from the capsule about 11 minutes before liftoff. The final preflight readiness poll of the Atlas V and Starliner teams should occur seven minutes before launch.

The Atlas V's propellant tanks will be secured and pressurized for flight in the final four minutes of the automated countdown. At T-minus 75 seconds, Wilmore will arm Starliner's launch abort system, which would push the capsule off the top of the Atlas V rocket in an emergency.

The rocket's Russian-made RD-180 engine will flash to life at T-minus 2.7 seconds, followed by ignition of the Atlas V's two strap-on solid rocket boosters to propel Starliner off the launch pad. Heading northeast, the Atlas V will surpass the speed of sound in 65 seconds and shed its spent solid-fueled boosters about 2 minutes and 20 seconds after liftoff.

An overview of the launch timeline from United Launch Alliance is embedded below.

The RD-180 main engine will fire for nearly four-and-a-half minutes, followed by staging and ignition of two hydrogen-fueled RL10 engines on the Centaur upper stage. The RL10s will burn for seven minutes, and the Centaur upper stage will deploy Starliner into space just shy of the 15-minute mark in the mission.

A maneuver with Starliner's own engines will place the spacecraft into a stable low-Earth orbit about 31 minutes into the flight. At that point, Wilmore and Williams can get out of their pressure suits and change into more comfortable clothing for the rest of the flight to the space station.

Each astronaut will take turns testing Starliner's manual flight controls a few hours into the flight, and then again early Sunday on approach to the space station. They will also downlink status reports on conditions inside the spacecraft, but these updates will be audio-only. Starliner does not yet have the ability to beam live video from orbit back to Earth.

If all goes according to plan, Starliner will dock on autopilot at the forward port of the station. A couple of hours after arriving at the outpost, Wilmore and Williams will open a hatch and float inside the sprawling research lab to join the six astronauts and cosmonauts living there. While Starliner is docked at the station, the crew members will transfer several hundred pounds of cargo. Wilmore and Williams will bring two of the station astronauts into the Boeing capsule to simulate the living conditions for a full crew complement of four people, as Starliner will carry on future missions.

At the end of the mission, Starliner will back away from the station, and the astronauts will again conduct manual flying demonstrations using hand controllers inside the cockpit. Then, Starliner will fire braking rockets to drop out of orbit and head for landing in the western United States, likely at a site in New Mexico or Arizona.

Last-minute changes

Aside from the helium leak, NASA and Boeing officials worked through a couple more issues in the final week before the crew test flight.

One of those involved a parachute malfunction on Blue Origin's suborbital crew capsule on May 19. One of Blue Origin's three main parachutes failed to fully inflate during the craft's final descent over West Texas, but the company's six private passengers landed safely.

The parachutes are supplied by Airborne Systems, the same contractor that provides main chutes for Boeing's Starliner, SpaceX's Dragon, and NASA's Orion capsules. The chute on the Blue Origin flight deployed and was supposed to inflate in stages to reduce structural loads on the capsule.

"In this case, one of the parachutes was sort of stuck in what I would call the first stage," Stich said. "Some amount of the mouth of the parachute wasn’t fully open."

Cutters were supposed to snip a reefing line to allow the parachute to fully open, but for some reason, that didn't happen. "It turns out we use a very similar cutter that Blue Origin uses, so it was important for us to look at that data," Stich said.

Engineers reviewed test data from the cutters used on Starliner and found no issues. "All the testing was really superb with cutting the reefing line, so that’s why we’re proceeding," he said.

A recent hardware failure on the International Space Station also prompted a late addition to the cargo manifest flying on the Starliner spacecraft. A pump malfunctioned on the station's urine processing assembly, part of the lab's intricate closed-loop life support system that converts urine into purified drinking water. Without the processor operating, astronauts have to store their urine on the station.

Earlier this week, NASA decided to launch a replacement pump on Starliner rather than wait for the next cargo flight to the station in August. The roughly 150-pound pump is about the size of a mini-refrigerator. Boeing had to pull two suitcases with the crew's personal clothing to accommodate the pump without disrupting the spacecraft's center of gravity.

Stich said NASA and Boeing teams showed a "lot of agility in the last week dealing with these things as they come up, which tells me that we’re really ready to go fly."