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Atlas V N22 and Starliner at the launch pad in Cape Canaveral. Image Credit: United Launch Alliance.

Starliner to conduct second orbital flight test

On Tuesday, August 3, 2021 at 13:20 EDT (local time) / 17:20 UTC, the unpiloted Boeing CST-100 Starliner vehicle is scheduled to launch atop an United Launch Alliance (ULA) Atlas V N22 rocket. The two-stage, medium-lift launch vehicle will blast off from Space Launch Complex 41 at the Cape Canaveral Space Force Station in Florida, USA, carrying the Starliner into space and toward the International Space Station.

The mission, known as the Orbital Flight Test 2 or OFT-2, will be an uncrewed test flight of Boeing’s new crew vehicle. Once in orbit, the Starliner will rendezvous with the ISS and subsequently dock to the space station’s Harmony module’s forward docking port on August 4 at 17:37 UTC. After a couple of days at the orbiting laboratory, the Starliner will undock from Harmony and return back to Earth. If everything goes according to plan, the spacecraft will re-enter the planet’s atmosphere on August 8 and land at the White Sand Missile Range in New Mexico. The primary objectives of this test flight will be to demonstrate the Starliner’s ability to rendezvous and dock with the space station and to safely land back on Earth once the mission is complete.

Starliner’s launch to the ISS was originally scheduled to occur on Friday, July 30, but had been postponed to August 3 to allow ground controllers to conduct more checkouts of the newly arrived Russian Nauka laboratory module. Nauka arrived at the space station on July 29 and successfully docked to the ISS’s Zvezda module at 13:29 UTC. About three hours later at 16:45 UTC, the module’s thrusters inadvertently began firing, putting the International Space Station out of its attitude by about 45 degrees. The station later regained orientation, after a firing of the thrusters of the uncrewed Russian Progress MS-17 resupply freighter.

Nauka approaches the ISS. Image Credit: Oleg Novitsky.
Nauka approaches the ISS. Image Credit: Oleg Novitsky.

Mission profile

At T+1.1 seconds, the Atlas V N22 with the Starliner vehicle is expected to blast off from SLC-41 at the Cape Canaveral SFS on August 3, at 17:20 UTC. Once the rocket has cleared its launch tower, it will begin its pitch and yaw manuevers to obtain its proper flight trajectory. At T+41.8 s, the launch vehicle will pass through Max-Q, the point of maximum dynamic pressure. This will be followed by the breaking of the sound barrier at about a minute after liftoff. At T+2 min 22 s, the two AJ-60 solid rocket boosters will burn out and will be separeted from the vehicle’s core stage. 4 minutes 29 s after launch, propellant levels in the Atlas V’s first stage deplete and the two RD-180 rocket engines shut down ahead of stage separation and igniton of the Centaur upper stage’s two RL-10 engines at T+4 min 45 s. After almost seven minutes of firing, the two liquid oxygen/liquid hydrogen fueled RL-10 will shut down, completing the powered phase of the flight. Exactly three minutes after cut off, the CST-100 Starliner will be separated from the Centaur second stage, completing the Atlas V’s mission.

Because the Atlas V’s trajectory will be suborbital, Starliner will use its own onboard propulsion system to enter orbit and to slowly raise it, ahead of the rendezvous with the International Space Station about 24 hours later.

The Starliner spacecraft

The Boeing CST-100 Starliner is a partially-reusable spacecraft, theoretically able to carry up to seven astronauts, as well as cargo, into space and to the International Space Station. The spacecraft was developed by Boeing for NASA’s Commercial Crew Program and will carry up to four passengers and time-critical research equipment and experiments to the orbital laboratory, once Boeing has successfully conducted both test flight’s of the vehicle.

The spacecraft is 5.03 m in height, 4.56 m in diameter and consits of the crew capsule, as well as the service module.

If this week’s uncrewed test flight succeeds, Boeing must perform a crewed test flight of the Starliner, before the company is allowed to launch astronauts to the orbital laboratory on a regular basis.

The OFT-2 Starliner atop its Atlas V rocket. Image Credit: United Launch Alliance.
The OFT-2 Starliner atop its Atlas V rocket. Image Credit: United Launch Alliance.

The Atlas V rocket

The Atlas V is a two-stage, medium-lift launch vehicle operated by the United Launch Alliance. Depending on the configuration, the rocket is capable of carrying between 9,800 kg and 18,850 kg into a 28.7 degrees inclined 200 km low Earth orbit, or between 4,750 kg and 8,900 kg into a 27.0 degress inclined geostationary transfer orbit.

The Atlas V N22, the rocket to launch the Starliner, consists of a Common Booster Core (CBC) as a first stage, equipped with two Russian liquid oxygen/RP-1 fueled RD-180 rocket engines built by NPO Energomash. Attached to the CBC are to Aerojet Rocketdyne AJ-60 solid rocket boosters, which will provide additional thrust during the first 2 1/2 minutes of the flight. Atop the first stage sits the cryogenic Centaur upper stage, which will be powered by two liquid oxygen/liquid hydrogen fueled RL-10 rocket engines. The Starliner is attached to the Atlas V through a launch vehicle adapter mounted atop the second stage.

The Atlas V has first flown on August 21, 2002 and has since been launched 87 times. The Atlas V is most commonly used to launch satellites for the U.S. military, but has previosly also carried several NASA probes into the depths of the Solar System. Notable spaceprobes are the Pluto explorer New Horizons, the Jupiter probe Juno and the two Mars rovers Curiosity and Perseverance.

Atlas V N22 and Starliner at the launch pad in Cape Canaveral. Image Credit: United Launch Alliance.
Atlas V N22 and Starliner at the launch pad in Cape Canaveral. Image Credit: United Launch Alliance.


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