Live coverage of the countdown and launch of a United Launch Alliance Atlas 5 rocket from pad 41 at Cape Canaveral Space Force Station in Florida. The mission will launch Boeing’s human-rated Starliner spacecraft on its second unpiloted Orbital Flight Test. Text updates will appear automatically below. Follow us on Twitter.

The countdown for liftoff of a United Launch Alliance Atlas 5 rocket and Boeing’s Starliner crew capsule began Thursday morning at Cape Canaveral. Launch is set for 6:54 p.m. EDT (2254 GMT) to begin the Starliner spacecraft’s second unpiloted test flight to the International Space Station.

You can watch our live launch coverage on this page.

The Starliner test flight is a precursor for future crew missions on the Boeing-owned capsule. The spacecraft was developed under the auspices of a multibillion-dollar commercial crew contract with NASA.

But the Starliner program is running years late, and the Orbital Flight Test 2 mission set for liftoff Thursday is a do-over of the first uncrewed test flight in December 2019. Officials called off the OFT-2 mission’s first launch opportunity last August due to stuck valves in the spacecraft’s propulsion, adding another nine-month delay to the program.

The Atlas 5 countdown began at 7:34 a.m. EDT (1134 GMT) Thursday with the power-up of the rocket’s computer for testing. The Atlas 5 rolled out to Space Launch Complex 41 at Cape Canaveral Space Force Station on Wednesday morning from ULA’s Vertical Integration Facility about a third of a mile south of the pad.

ULA’s launch team loaded rocket-grade kerosene into the Atlas 5’s first stage Wednesday. Super-cold liquid oxygen will be pumped into the Atlas 5’s first stage during the countdown Thursday, along with liquid hydrogen and liquid oxygen for the Centaur upper stage.

ULA has extended the countdown timeline for Starliner missions. The Atlas 5 countdown typically lasts about seven hours for a satellite launch. For Starliner missions, the countdown runs more than 11 hours.

Fueling of the Atlas 5’s first stage and Centaur upper stage with cryogenic propellants will commence around six hours prior to liftoff at at 12:54 p.m. EDT (1654 GMT). A built-in countdown hold at T-minus 4 minutes, which normally lasts 15 minutes, will extend for four hours, a change to give astronauts time to board the Starliner spacecraft on crew missions.

ULA is following the same countdown timeline for the unpiloted OFT-2 mission, giving teams an opportunity to practice for the presence of astronauts on future flights.

A “blue team” comprised of fewer than 10 Boeing and ULA employees will help the astronauts into the Starliner spacecraft during countdowns for crewed missions. The team’s job will be similar to the closeout crew from the Apollo and space shuttle eras.

During the OFT-2 countdown, the blue team will travel to the launch pad and run through their launch day procedures during the four-hour countdown hold, just as they would if astronauts were flying. The blue team will close the Starliner hatch and evacuate the pad before the resumption of the countdown. The crew access arm will retract from the Starliner spacecraft about 11 minutes before liftoff.

Then the countdown clock will start ticking again at T-minus 4 minutes, and the Atlas 5 will switch to internal power, pressurize its propellant tanks, and prepare for ignition of its RD-180 main engine.



Liftoff is timed for exactly 6:54:47 p.m. EDT (2254:47 GMT). There is one instantaneous launch opportunity per day for the OFT-2 mission.

If all goes according to plan, the Starliner spacecraft will arrive at the space station for an automated docking at 7:10 p.m. EDT (2310 GMT) Friday. Undocking and landing in New Mexico is scheduled for May 25, weather permitting.

The launch of the 172-foot-tall (52-meter) Atlas 5 rocket Thursday will kick off the critical test flight. Liftoff is timed for roughly the moment Earth’s rotation brings the launch pad under the flight path of the International Space Station.

The Atlas 5 will fire off the pad with 1.6 million pounds of thrust from its Russian-made RD-180 main engine and two solid rocket boosters supplied by Aerojet Rocketdyne. Steering northeast from the seaside launch complex, the Atlas 5 will surpass the speed of sound in 65 seconds, then shed its strap-on boosters at T+plus 2 minutes, 22 seconds.

The RD-180 engine, burning kerosene and liquid oxygen, will fire until T+plus 4 minutes, 29 seconds. The RD-180 will throttle back late in its four-and-a-half minute burn to limit acceleration loads on the Starliner to no more than 3.5 Gs, just as it will on future astronaut missions.

Six seconds after engine shutdown, the bronze first stage will separate from the Atlas 5’s Centaur upper stage to fall into the Atlantic Ocean, then a disposable aerodynamic cover will jettison from the nose cone of the Starliner capsule.

Two Aerojet Rocketdyne RL10 engines will ignite at T+plus 4 minutes, 45 seconds, to begin a seven-minute burn. A few seconds later, the Atlas 5 will jettison an aerodynamic skirt extension under the Starliner spacecraft. The Centaur stage’s RL10 engines will generate 44,600 pounds of thrust to place the Starliner spacecraft on an arcing, suborbital trajectory.

The Atlas 5 rocket’s configuration for Starliner crew flights is unique from the launcher variant used for satellite missions. The dual-engine Centaur upper stage, once a mainstay of older versions of the Atlas rocket, has only flown once on an Atlas 5 — the first Starliner test flight in 2019.

The dual-engine upper stage has the power required to place the Starliner spacecraft at the proper altitude and speed, while flying a flatter and throttled back trajectory, maintaining safe abort options for astronaut crews throughout the climb into space. The flight profile also minimizes g-loads on the Starliner spacecraft and astronauts inside.

The Atlas 5 will release the Starliner spacecraft nearly 15 minutes after liftoff on a 112-mile-high (181-kilometer) suborbital trajectory, just shy of the velocity needed to enter a stable orbit around Earth. After separating from the rocket, the Starliner’s own engines, mounted on the ship’s service module, will boost the spacecraft into orbit to begin the trek to the International Space Station.

The suborbital trajectory is unusual for a satellite launch, but it is similar to the technique used by the space shuttle. The shuttle’s three main engines, fed by cryogenic propellants from an external fuel tank, accelerated the orbiter into space, reaching a velocity just short of that required to enter orbit.

After jettisoning the expendable external tank, the shuttles fired their in-space maneuvering engines around a half-hour after launch to enter orbit. Otherwise, the shuttles would have cut short their missions and re-entered the atmosphere.

Credit: United Launch Alliance

The Starliner will follow a similar launch profile on the OFT-2 mission, and on the subsequent crewed flights. The Starliner’s orbit insertion burn is scheduled to begin about 31 minutes into the mission.

The Atlas 5’s Centaur upper stage will continue on the suborbital path for re-entry into the atmosphere. Debris from the upper stage will impact in the Indian Ocean southwest of Australia.

The Starliner spacecraft’s launch abort engines will be armed during the ride into space Thursday. On Boeing’s OFT-1 mission in 2019, the abort system operated in a “monitor” or “shadow” mode to avoid an inadvertent abort trigger.

The Atlas 5 rocket carries an Emergency Detection System, consisting of two redundant computers, to monitor key health parameters on the launch vehicle. If a safety limit is tripped, the Starliner will automatically command an abort, and the capsule’s escape engines would push it away from the failing rocket.

ROCKET: Atlas 5 (AV-082)

MISSION: Starliner OFT-2

PAYLOAD: Starliner spacecraft for Boeing and NASA

LAUNCH SITE: SLC-41, Cape Canaveral Space Force Station, Florida

LAUNCH DATE: May 19, 2022

LAUNCH TIME: 6:54:47 p.m. EDT (2254:47 GMT)

WEATHER FORECAST: 80% chance of acceptable weather; Primary concerns are cumulus clouds and anvil clouds

BOOSTER RECOVERY: None

LAUNCH AZIMUTH: Northeast

TARGET ORBIT: Suborbital trajectory at spacecraft separation with an apogee or 112 miles (181 kilometers); Starliner will perform an orbit insertion burn at T+plus 31 minutes

LAUNCH TIMELINE:

T-00:00:02.7: RD-180 ignition T+00:00:01.1: Liftoff T+00:00:06.1: Begin pitch/yaw maneuver T+00:00:41.8: Maximum aerodynamic pressure (Max-Q) T+00:01:05.8: Mach 1 T+00:02:22.0: Solid rocket booster jettison T+00:04:29.0: Atlas booster engine cutoff (BECO) T+00:04:35.0: Atlas/Centaur stage separation T+00:04:41.0: Ascent cover jettison T+00:04:45.0 Centaur first main engine start (MES-1) T+00:05:05.0: Aeroskirt jettison T+00:11:54.5: Centaur first main engine cutoff (MECO-1) T+00:14:54.5: Starliner spacecraft separation

MISSION STATS:

675th launch for Atlas program since 1957 376th Atlas launch from Cape Canaveral 264th mission of a Centaur upper stage 241st use of Centaur by an Atlas rocket 510th and 511th production RL10 engine to be launched 99th flight of an RD-180 main engine 93rd launch of an Atlas 5 since 2002 2nd flight of a Starliner spacecraft on an Atlas 5 rocket 27th flight of an Atlas 5 rocket in support of a NASA mission 130th and 131st AJ-60 solid rocket boosters flown 77th launch of an Atlas 5 from Cape Canaveral 3rd Atlas 5 launch of 2022 135th Evolved Expendable Launch Vehicle flight 150th United Launch Alliance flight overall 85th Atlas 5 under United Launch Alliance 108th United Launch Alliance flight from Cape Canaveral 2nd Atlas 5 to fly in the N22 configuration 104th launch from Complex 41 77th Atlas 5 to use Complex 41 21st orbital launch attempt overall from Cape Canaveral in 2022