Countdown proceeding for Boeing’s Crew Flight Test
Boeing’s CST-100 is L-1 hour from launching NASA astronauts Butch Wilmore and Suni Williams to the International Space Station at 12:25 p.m. EDT. The test-pilot crew is strapped into their seats inside Starliner and working with mission operations teams in Houston and Florida to complete final pre-launch procedures.
Right now, the “T-minus” clock is holding at T-4 minutes. Roughly eight minutes before liftoff, launch control teams will conduct a final go/no-go poll to lift the hold on the T-minus clock exactly four minutes before liftoff. Before the count is resumed, the CFT crew will lower their visors and seal their spacesuits.
When the hold is lifted, launch teams officially enter what’s known as the terminal count. A number of important milestones will occur, including transitioning Starliner to internal power and arming the launch abort system, which would send the astronauts to safety if there was an issue with the rocket.
At T-0, the Atlas V RD-180 main engine and two solid rocket boosters will ignite to generate more than a million and half pounds of thrust to lift the rocket away from the pad. The RD-180 main engine burns 48,800 gallons of liquid oxygen and 25,000 gallons of RP-1 fuel, a highly refined kerosene, to generate 860,300 pounds of thrust.
The Centaur is powered by two RL10A-4-2 engines that consume 12,300 gallons of liquid hydrogen and 4,150 gallons of liquid oxygen to generate a combined 44,600 pounds of thrust to shape the desired trajectory for Starliner. During the flight, Atlas V will accelerate Starliner to 17,475 mph.
The powered flight of Atlas V to launch Starliner’s CFT lasts about 11 minutes and 55 seconds. The first stage of flight will last about 4 minutes and 30 seconds. The single burn of the Centaur lasts about 7 minutes and 10 seconds. Roughly 15 minutes after liftoff, Starliner will separate from the top of the Centaur.
About 15 minutes later, Starliner will fire four of its aft-facing 1,200-lb thrust-class Orbital Maneuvering and Attitude Control thrusters for approximately a minute, circularizing and stabilizing Starliner’s orbit and sending Wilmore and Williams en route to the ISS.