Atlas V

Atlas V is an active expendable launch system in the Atlas rocket family and is now operated by the Lockheed Martin-Boeing joint venture United Launch Alliance.Atlas V rocket uses a Russian-built RD-180 engine burning kerosene and liquid oxygen to power its first stage and and a Centaur Upper Stage. Thrust can be augmented with up to five  strap-on solid rocket boosters, each providing an additional 1.27 meganewtons (285,500 lbf) of thrust for 94 seconds.

Each Atlas V booster configuration has a three-digit designation that indicates the features of that configuration. The first digit shows the diameter (in meters) of the payload fairing, and always has a value of "4" or "5". The second digit indicates the number of solid rocket boosters attached to the base of the rocket, and can range from "0" through "3" with the 4-meter fairing, and "0" through "5" with the 5-meter fairing. The third digit represents the number of engines on the Centaur stage, either "1" or "2". Atlas V 401 is the smallest of the Atlas V Launcher Family featuring no Solid Rocket Boosters and a 4.2-meter Payload Fairing. The 401 configuration has two stages, a Common Core Booster and a Centaur Upper Stage. Centaur can make multiple burns to deliver payloads to a variety 

of orbits.

 The first Stage of the Atlas V 401 is an Atlas Common Core Booster that is 32.46 meters long and has a diameter of 3.81 meters.  It has a empty mass of  21,054 Kilograms . It is equipped with a single

 RD-180  engine. RD-180 is being manufactured by NPO Energomash. It is a two-chamber staged combustion engine that provides 3,827 Kilonewtons of liftoff thrust and 4,152 Kilonewtons of vacuum thrust. RD-180 maintains a high-pressure staged combustion cycle employing an Oxygen-rich preburner. RD-180 is capable of being throttled from 50% to 100% of rated performance. First Stage control is accomplished by gimbaling the RD-180 nozzles by up to 8 degrees. 

Centaur is a cryogenic rocket stage using Liquid Hydrogen and Liquid Oxygen as propellants. A total of 20,830 Kilograms of propellants can be filled into the vehicle’s pressure stabilized stainless steel tanks. The LOX and LH2 Tanks are separated by a common  bulkhead. The engine uses an expander cycle and operates at a chamber pressure of 39 bar. It is 3.53 meters in length, 1.53 meters in diameter and features a Nozzle Extension. RL-10 has a certified burn time of up to 842 seconds and can make multiple engine starts.