Delta II rocket

The Boeing Delta II family of launch vehicles has been in service for over 10 years and has successfully launched 90 projects including the last six NASA missions to Mars:

• Mars Global Surveyor in 1996
• Mars Pathfinder in 1996
• Mars Climate Orbiter in 1998
• Mars Polar Lander in 1999
• Mars Odyssey in 2001
• Mars Exploration Rovers (MER-A and MER-B) in 2003

Deltas are expendable launch vehicles (ELVs), which means they are only used once. Each launch vehicle consists of:

• Solid rocket motors: Used to increase engine thrust; 9 total, 6 of which are lit at liftoff, 3 a minute into flight
• Stage I: Fuel and oxygen tanks that feed an engine for the ascent
• Stage II: Fuel and oxidizer and the vehicle's "brains"; fires twice, once to insert the vehicle-spacecraft stack into low Earth orbit and then again to orient the third stage prior to it firing
• Stage III: Solid rocket motor provides the majority of the velocity change needed to leave Earth orbit and inject the spacecraft on a trajectory to Mars; connected to the spacecraft until done firing, then separates
• Payload fairing: Thin metal shroud or nose cone to protect the spacecraft during the ascent through Earth's atmosphere