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NASA, Boeing prepares its Starliner OFT to dock with ISS

Updated: May 20, 2022

Spacecraft will make a second unmanned flight, and it should dock with the ISS

Atlas V N22 AV-082

NASA and Boeing will launch the Starliner CST-100 spacecraft, (designated number S2.1) designed to transport astronauts to the International Space Station, on its second unmanned test flight. The liftoff time today, May 19, 2022, has been established for the Atlas V rocket to send Starliner into convergence orbit with the International Space Station. Based on the most recent calculations of when the station's orbital plane will pass over the Cape Canaveral platform, the launch will take place at 18:54:47 EDT (22:54:47 UTC). Liftoff will be from Space Launch Complex-41 at Cape Canaveral Space Force Station, Florida. The United Launch Alliance Atlas V N22 Rocket (with tail number AV-082) assigned for this OFT-2 mission, will launch the Boeing spacecraft.

Part of NASA's Commercial Crew Program (CCP), the unmanned OFT is Starliner's second launch. The second uncrewed test flight will demonstrate the end-to-end performance of the rocket and spacecraft, including the guidance, navigation and control systems, ground systems and operations teams, as well as in orbit, docking, entry and landing operations. Starliner will land at one of five designated locations in the western United States.

The mission, called Orbital Flight Test 2, OFT-2, is a redo – this time complete, it is expected – of the OFT-1 launched in December 2019 and which suffered software glitches that prevented docking with the station. This test flight is the last major step before the Atlas V and Starliner capsule will take American astronauts to the ISS as part of NASA's Commercial Crew Program.

Atlas V atop Starliner SC2.1 poised at LC-41, Cape Canaveral (Photo Credit: NASA)

The rocket will take the spacecraft on a suborbital trajectory of 181.496 km. The first stage will follow a trajectory that will place the Centaur stage in a 182 km x 73 km orbit, with the spacecraft making a perigee lift thrust 16 minutes after separation. In an animation by the ULA of last May 12, the altitude at which the separation of Starliner from Centaur would occur would be even lower: 162 km at the moment of Tcp + ~ 890 seconds.

Risk factor; The specific impulse of OMAC engines, which perform orbital maneuvers, is about 288 seconds, with a thrust of 7,000 newtows (7 kN). The time to reach 90% thrust is less than 5 milliseconds. With a launch weight of the spacecraft at around 13,250 kg, the propellant consumption should be more than enough for the docking with the ISS and still allow clearance in subsequent maneuvers.

After the separation of the Atlas V, the engines of Starliner will be activated, taking it for the rest of the trajectory in orbit to the space station, docking with the PMA-2/IDA-2 forward docking port on the American module Harmony.

ATLAS V N22/ CFT-100 Starliner Factsheet (Credit: NASA)

Modified specifically for the CST-100, the Atlas V configuration does not include a payload fairing. Instead, the craft's insulated surfaces replace the usual head fairing to protect the unmanned spacecraft during ascent. The length of the rocket with the spacecraft is approximately 52.4 meters.

The Starliner is integrated into the Atlas V using a launch vehicle adapter (LVA), which also includes a skirt to reduce aerodynamic loads on the vehicle. This aeroskirt is discarded for better performance after center stage separation.

The second stage Centaur is 3.05 meters in diameter and 12.61 m in length. Its propellant tanks are pressure stabilized and constructed of corrosion-resistant stainless steel. The Centaur is a cryogenic vehicle, powered by liquid hydrogen and oxygen. The Atlas V configuration for this mission is powered by two RL10A-4-2 engines, each producing 10,251,188 kgf (100.5 kilonewtons) of thrust. Cryogenic tanks are insulated with a combination of helium purged blankets, heat shields, and spray foam insulation (SOFI). The Centaur Forward Adapter (CFA) provides structural mounts for the fault-tolerant avionics system and electrical interfaces to the spacecraft. The Centaur also includes an Emergency Detection System (EDS) that monitors hazards to detect an impending or ongoing failure.

The first stage is 3.81 meters in diameter and 32.4 meters in length. The tanks are structurally rigid and constructed with isogrid-style aluminum barrels, shaped aluminum domes and inter-tank skirts. Propulsion is produced by the RD-180 engine system (a piece of single turbo machinery with two thrust chambers). The RD-180 burns RP-1 (Rocket Propellant-1 or highly purified kerosene) and liquid oxygen, and provides 390,180.155 kgf (3.83 meganewtons) of thrust at sea level. Two solid-propellant boosters (SRBs) generate the additional energy needed at takeoff, with each SRB producing 158,076.94 kgf (1.55 meganewtons) of thrust. The Centaur's avionics system performs guidance, flight control and sequencing functions during the first stage and Centaur phases of flight.


Though no crew will be onboard the spacecraft for OFT-2, the Starliner commander’s seat will be occupied by Rosie the Rocketeer, the company’s anthropometric test device. During OFT-1, Rosie was outfitted with 15 sensors to collect data on what astronauts will experience during flights on Starliner. For OFT-2, spacecraft data capture ports previously connected to Rosie’s 15 sensors will be used to collect data from sensors placed along with the seat pallet, which is the infrastructure that holds all the crew seats in place.

During Starliner’s approach to the space station, NASA and Boeing will verify data links and command capabilities by the station crew, including a hold during approach commanded from the station by NASA astronaut Kjell Lindgren aboard the station. Starliner also will demonstrate its ability to perform an automated retreat in the event an issue arises during the approach.

Starliner’s vision-based navigation system (LIDAR) will be tested as it autonomously docks with the space station at around 7:10 p.m. (2310 UTC) Friday, May 20, or about 24 hours after launch.

After a successful docking, Starliner brings some cargo, and it will spend five to 10 days aboard the orbiting laboratory before returning to Earth in the western United States. The spacecraft will return with nearly 600 pounds (273 kg) of cargo, including reusable Nitrogen Oxygen Recharge System tanks that provide breathable air to station crew members.

OFT-2 will build on the mission objectives achieved during Starliner’s initial flight test, including:

  • In-orbit operation of the avionics, docking system, communications and telemetry systems, environmental control systems, solar arrays, electrical power systems and propulsion systems;

  • Performance of the guidance, navigation & control systems of the Starliner and Atlas V through ascent, on-orbit, and entry;

  • Acoustic and vibration levels, and loads across the Starliner exterior and interior;

  • Launch escape trigger monitoring;

  • Performance of the Starliner system, end-to-end mission operations.

OFT-2 also will test the changes and improvements made to Starliner, and prove the system is ready to fly astronauts. NASA and Boeing engineers, technicians and flight control teams have all been working together to get Starliner back to space safely and efficiently for OFT-2. Following a successful flight test and subsequent data reviews, NASA and Boeing will set a target launch date for the Crew Flight Test (CFT) with astronauts on board.

Atlas V/Starliner Ascent Profile

Launch and Ascent: The ascent phase of the test flight starts after ignition of the Atlas V’s RD-180 main engine and two solid rocket boosters. As the Atlas V continues to climb, it will work its way through various launch milestones, including Max Q, solid booster jettison, booster stage separation, and Centaur ignition. Following orbital insertion, Starliner will separate from the Centaur upper stage, followed several minutes later by an adjust maneuver setting it on its path to rendezvous and dock with the station.

Rendezvous and Docking: Once in a stable orbit on course for the space station, Starliner continues its rendezvous maneuvers designed to mirror the same orbit as the station. After it gets closer to the station, it will pause before entering the 656-foot (200-meter) “keep out sphere” while flight controllers evaluate the alignment and readiness to proceed with docking. Starliner then begins the docking process, pausing once more at about 33 feet (10 meters)

away, before final approach and autonomously docking to an International Docking Adapter.

Undocking, Reentry, and Landing: Starliner is designed to land at one of five landing sites in the western United States—two on the White Sands Missile Range in New Mexico, one on the Dugway Proving Ground in Utah, one on the Willcox Playa in Arizona, and one on Edwards Air Force Base in California. When cleared to leave the space station, Starliner undocks, performs a flyaround maneuver, and positions itself for the deorbit burn to slow from orbital velocity in preparation for atmospheric reentry, where it is met with reentry heating of 3,000 degrees Fahrenheit (1,650 degrees Celsius). Starliner will

jettison the forward heat shield around 30,000 feet (9 km) above the ground, followed by deployment of a series of parachutes. First, two drogue parachutes continue to slow Starliner, followed by extraction of the three main parachutes. At 3,000 feet (.9 km) from the ground, airbags inflate to further absorb the initial forces of landing, cushioning the crew for a soft, safe return to Earth.


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