1:37PM EST May 18th atop an Atlas V rocket from Space Launch Complex 41
Now that the mission has been deemed a success lets take a closer look at the timeline of events chronicled before, during, and after launch of the Atlas V in the 421 configuration. Today’s SBIRS GEO-5 mission had a forty minute window of opportunity, meaning it had only forty minutes during the entire day for the launch to occur for the satellite to get into the desired orbit by the department of defense. Our timeline started at 1:31 PM Est this afternoon and the launch occurred just six minutes after that opening at 1:27 PM EST.
- T-minus 0 the RD-180 main engine ignites along with twin SRBs (Solid Rocket Boosters). These give the rocket, which has its first stage fueled by liquid oxygen & rocket grade kerosene (RP-1) up to 1.6 million pounds of thrust. It slowly starts to rise off the pad and gains speed the higher it climbs.
- T-plus 47seconds, the rocket has passed through the sound barrier and passes through what’s called Max Q, or when the rocket goes into the area of maximum dynamic pressure during its ascent through the lower atmosphere.
- T-plus 2minutes 9 seconds, The two SRBs are jettisoned from the rocket. Designed by Aerojet Rocketdyne these boosters burn HTPB to help propel the rocket. Having run out of fuel about forty seconds prior the rocket waits until it’s passed through the Max Q before releasing the to give less chance of an issue arising.
- T-plus 4minutes 10 seconds, the RD-180 main engine has finished it’s supply of that liquid oxygen and kerosene and shuts off. Five seconds later the Common Core Booster first stage of the Atlas V rocket separates from the Centaur upper stage.
- T-pluse 4minutes 19seconds, the Centaur RL10C-1-1 engine starts up using it’s liquid hydrogen and liquid oxygen fuel system. This stage of the rocket will continue to propel the SBIRS GEO-5 into the initial parking orbit. After another eight seconds go by the faring halves that enclose the payload will also separate and fall of the upper stage.
- T-plus 15minutes 6seconds, the Centaur upper stage shuts down in a LEO (Low Earth Orbit) that is planned or considered the parking orbit. During this time the vehicle coasts for about sixteen minutes until it arrives at the location required in orbit for the second burn to take place. At this point in the mission two small suitcase sized satellites of the U.S. Air Force Academy will deploy.
- T-plus 31minutes 6seconds, Centaur ignites again while raising the orbit’s low point and reduces the orbital inclination for the spacecraft before shutting down the final time just under five minutes later. When the RL10C-1-1 engine shuts off SBIRS GEO-5 will be somewhere between 925kilometers and 35,753kilometers with an inclination angle of 21.14 degrees towards the equator. (the exact height is not know to protect the satellite)
- A short time later the upper stage and payload separate as the satellite is now in its new home where it will live for the duration of it’s lifespan protecting our soil by detecting missile launches, support ballistic missile defense and expands our technical intelligence gathering to bolster situational awareness on the battlefield.