MA-5A was an American liquid fueled

rocket A rocket (from it, rocchetto, , bobbin/spool) is a vehicle that uses jet propulsion to accelerate without using the surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely fr ...

stage. It was manufactured by

Lockheed Martin The Lockheed Martin Corporation is an American aerospace, arms, defense, information security, and technology corporation with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta in March 1995. It ...

for use on the

Atlas II Atlas II was a member of the Atlas family of launch vehicles, which evolved from the successful Atlas missile program of the 1950s. The Atlas II was a direct evolution of the Atlas I, featuring longer first stage tanks, higher-performing engines ...

rocket, derived from the MA-5 used on the

Atlas I The Atlas I was a US expendable launch system manufactured by General Dynamics in the 1990s to launch a variety of satellites. In June 1987, General Dynamics committed $100M to acquire long-lead procurement items to support build of 18 vehicles f ...

Design

MA-5A functioned as the "half stage" in the Atlas's "stage-and-a-half" design, meaning they functioned as a booster attached to a central sustainer core, but did not include their own fuel tanks. Instead, fuel was drained out of the tanks of the sustainer core, until partway through the launch the booster segment was jettisoned. Similar to the booster segments on previous Atlas rockets, MA-5A consisted of a thrust structure with attachment points and fuel lines for two RS-56-OBA rocket engines, each contained in a nacelle for aerodynamic reasons. The middle was left empty to accommodate the RS-56-OSA engine of the sustainer stage. The two booster engines shared a common

gas generator A gas generator is a device for generating gas. A gas generator may create gas by a chemical reaction or from a solid or liquid source, when storing a pressurized gas is undesirable or impractical. The term often refers to a device that uses a ...

, but separate

turbopump A turbopump is a propellant pump with two main components: a rotodynamic pump and a driving gas turbine, usually both mounted on the same shaft, or sometimes geared together. They were initially developed in Germany in the early 1940s. The purpos ...

s, combustion chambers, and other hardware. The stage also contains ten bottles of pressurized

helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...

, used to drive the

pneumatics Pneumatics (from Greek ‘wind, breath’) is a branch of engineering that makes use of gas or pressurized air. Pneumatic systems used in industry are commonly powered by compressed air or compressed inert gases. A centrally located and elec ...

for the engines and for tank pressurization. On the Atlas IIAS configuration, MA-5A also featured attachment points for four Castor 4A solid rocket boosters. MA-5A was based on the design of the previous MA-5 stage, used on Atlas I. The main difference between the two designs was the replacement of the MA-5's two LR-89-7 engines with RS-56-OSAs.

References

{{Reflist Rocket stages