Launch Vehicle

Photo of Mars Odyssey launch.
Photo of Mars Odyssey launch.
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Launch Vehicle

What is a launch vehicle?

A launch vehicle provides the velocity needed by a spacecraft to escape Earth's gravity and set it on its course for Mars.

Launch vehicle for this mission:

Odyssey launched on Boeing's Delta II 7925 that uses nine strap-on solid rocket motors. Each of the nine solid rocket motors is 1 meter (3.28 feet) in diameter and 13 meters (42.6 feet) long; each contains 11,765 kilograms (25,937 pounds) of hydroxyl-terminated polybutadiene (HTPB) propellant and provides an average thrust of 485,458 newtons at liftoff. The casings on the solid rocket motors are made of lightweight graphite epoxy.

The main body of the first stage houses the Rock LR101-NA-11 vernier engines. The vernier engines provide roll control during main engine burn and attitude control after main engine cutoff before the second stage separation. The RS-27 main engine is a single start, liquid bipropellant load that carries 96,000 kilograms (211,000 pounds) of RP-1 (rocket propellant 1, a highly refined form of kerosene) as its fuel and liquid oxygen as an oxidizer.

The second stage is 2.4 meters (8 feet) in diameter and 6 meters (19.7 feet) long, and is powered by a AJ10-118K engine. The propellant is 6000 kilograms (13,228 pounds) of Aerozine 50 fuel, a 50/50 mixture of hydrazine and unsymmetric dimethly hydrazine and nitrogen tetroxide as the oxidizer. The engine is restartable and will perform two separate burns during the launch.

The third and final stage of the Delta II 7925 will provide the final velocity required to place Odyssey on a trajectory to Mars. This upper stage, called a PAM-D, consists of a spin table to support, rotate and stabilize the spacecraft/PAM-D combination before separating from the second stage, a Star-48B solid rocket motor for propulsion, and active nutation control system to provide stability after ignition of the PAM-D motor, a payload attach fitting to mount the spacecraft to the Star 48B motor and a yo-yo despin system designed to decrease the spin rate of the spacecraft/PAM-D combination stack prior to spacecraft separation.

During launch and ascent through Earth's atmosphere, the spacecraft PAM-D upper stage combination is protected from aerodynamic forces by a 2.9 meter (9.5 foot) diameter payload fairing, that is jettisoned from the launch vehicle during second stage powered flight at an average altitude of 131 kilometers (81 miles).

Launch Facts

Launch Date: April 7, 2001, 11:02 AM EST
Launch Site: Cape Canaveral Air Force Station, Florida
Launch Vehicle: Delta II 7925