The United Launch Alliance Atlas 5 rocket (AV023) carrying the NROL-38 classified military satellite will launch tomorrow (20th June 2012) in the 401 configuration. Sounds impressively scientific, but what EXACTLY does that mean?
The First digit indicates the diameter (in metres) of the payload fairing, and always has a value of either 4 or 5. For the NROL-38 mission the payload fairing is 4 metres in diameter.
The second digit indicates the number of solid rocket boosters attached to the base of the rocket, and can range from 0 through 3 for the 4 metre fairing, and 0 through 5 with the larger 5-metre fairing. The Atlas V carrying NROL-38 mission has no additional solid rocket boosters.
The third digit represents the number of engines on the Centaur upper stage. This can be either 1 or 2. This particular Atlas 5 has 1 Centaur upper stage engine.
The Atlas 5 rocket is a very capable and reliable rocket, having had 29 successes of its 30 flights so far. Atlas first stage propulsion is provided by an RD-180 engine. This engine provides a single engine with 2 thrust chambers. It burns RP1 (Rocket Propellant 1 – highly purified kerosene) and liquid oxygen and provides 3,827 kN (Kilonewtons) of thrust at sea-level.
The Atlas 5 rocket is capable of carrying between 9 and almost 15 tonnes into low Earth orbit, and between 4 1/2 and 7 1/2 tonnes into a geosynchronous transfer orbit (dependent on exactly which configuration is used). It’s two designated launch facilities are at Launch Complex 41 (LC-41) at Cape Canaveral Air Force Station in Florida and Launch Complex 3 (SLC-3) at Vandenberg Air Force Base in California.
Recent missions that have used an Atlas 5 rocket include, Mars Reconnaissance Orbiter, Solar Dynamics Observatory, Boeing X-37B, Juno,
and the Mars Science Laboratory