Delta II
The Boeing IDS 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:
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; nine total, six of which are lit at liftoff, three lit one 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
