A United Launch Alliance (ULA) Atlas V rocket launched Boeing's Crew Space Transportation (CST)-100 Starliner spacecraft on its Orbital Flight Test-2 (OFT-2) to the International Space Station at 6:54 p.m. on 19 May 2022 from Space Launch Complex-41 at Cape Canaveral Space Force Station. OFT-2 is the second uncrewed flight of the Starliner that will demonstrate the spacecraft's human transportation capabilities. This test flight is the last major step before the Atlas V and Boeing's Starliner capsule take American astronauts to the International Space Station as part of NASA's Commercial Crew Program.

Part of NASA’s Commercial Crew Program (CCP), the uncrewed OFT is the second launch of the CST-100 Starliner. The second uncrewed test flight will demonstrate end-to-end performance of the Atlas V rocket and Starliner spacecraft, including performance of the guidance, navigation and control systems, ground systems and operations teams, as well as on-orbit, docking at the International Space Station (ISS), re-entry and landing operations.

For OFT-2, Starliner will spend about five to 10 days in space and deliver more than 500 pounds of NASA cargo to the space station. This includes food and crew preference items for the current expedition crew members on station, and provisions, like clothes and sleeping bags, for CFT astronauts. The spacecraft will return to Earth in the western United States with more than 550 pounds of cargo, including reusable Nitrogen Oxygen Recharge System (NORS) tanks that provide breathable air to station crew members.

ATLAS V LAUNCH VEHICLE [TEXT & IMAGE: UNITED LAUNCH ALLIANCE]
Spacecraft
Modified specifically for the Boeing CST-100 Starliner spacecraft, the Atlas V Starliner configuration does not include a payload fairing. Instead, the Starliner’s insulated surfaces take the place of the fairing to protect the uncrewed spacecraft during ascent. The vehicle’s height with the Boeing CST-100 Starliner is approximately 172 ft (52.4 meters).

The CST-100 Starliner is attached to the Atlas V using a launch vehicle adapter (LVA), which also includes an aeroskirt to reduce the aerodynamic loads on the vehicle. The aeroskirt is jettisoned for improved performance following booster stage separation.

Centaur
The Centaur second stage is 10 ft (3 meters) in diameter and 41.5 ft (12.6 meters) in length. Its propellant tanks are pressure-stabilized and constructed of corrosion-resistant stainless steel. Centaur is a cryogenic vehicle, fueled with liquid hydrogen and liquid oxygen. The Atlas V configuration for this mission is powered by dual RL10A-4-2 engines, each producing 22,600 lbs (100.5 kilo-Newtons) of thrust. The cryogenic tanks are insulated with a combination of helium- purged blankets, radiation shields and spray-on foam insulation (SOFI). The Centaur forward adapter (CFA) provides structural mountings for the fault-tolerant avionics system and electrical interfaces with the spacecraft. The Centaur also includes an Emergency Detection System (EDS) that monitors for critical hazards to detect an imminent or occurring failure. The EDS also provides critical in-flight data which supports jettison of the ascent cover and initiates CST-100 Starliner spacecraft separation.

Booster
The booster is 12.5 ft (3.81 meters) in diameter and 106.5 ft (32.4 meters) in length. The booster’s tanks are structurally rigid and constructed of isogrid aluminum barrels, spun-formed aluminum domes and intertank skirts. Booster propulsion is provided by the RD-180 engine system (a single engine with two thrust chambers). The RD-180 burns RP-1 (Rocket Propellant-1 or highly purified kerosene) and liquid oxygen and delivers 860,200 lbs (3.83 mega-Newtons) of thrust at sea level. Two solid rocket boosters (SRBs) generate the additional power required at lifto!, with each SRB providing 348,500 lbs (1.55 mega-Newtons) of thrust. The Centaur avionics system provides guidance, flight control and vehicle sequencing functions during the booster and Centaur phases of flight.