NASA Project Constellation
Project Constellation is a NASA program to create a new generation of spacecraft for human spaceflight, consisting primarily of the Ares I and Ares V launch vehicles, the Orion crew capsule, the Earth Departure Stage and the Altair lunar lander. These spacecraft will be capable of performing a variety of missions, from Space Station resupply to lunar landings.
Most of the Constellation hardware is based on systems originally developed for the Space Shuttle, although Orion's two-part crew and service module system is heavily influenced by the earlier Apollo Spacecraft, and it uses engines derived from the Saturn V and Delta IV rockets. Proposed Constellation missions may employ both Earth Orbit Rendezvous and Lunar Orbit Rendezvous techniques.
Constellation Program
NASA has formed the Constellation Program to achieve the objectives of maintaining American presence in low Earth orbit, returning to the Moon for purposes of establishing an outpost, and laying the foundation to explore Mars and beyond in the first half of the 21st century. The Constellation Program's heritage rests on the successes and lessons learned from NASA’s previous human spaceflight programs: Mercury, Gemini, Apollo, Space Shuttle and the International Space Station (ISS).
Spacecraft
Orion will consist of two main parts, a Crew Module (CM) similar to the Apollo Command Module capable of holding four to six crew members, and a cylindrical Service Module (SM) containing the primary propulsion systems and consumable supplies. The Orion CM will be reusable for up to 10 flights, allowing NASA to construct a fleet of Orion CMs.
Current plans call for the phased introduction of Orion variants tailored for specific missions. The Block I Orion will be employed for ISS crew rotation and resupply and other Earth orbit missions, while the Block II and III variants will be designed for deep-space exploration.
Launch vehicles
As currently envisioned, the Orion spacecraft will be launched into a low earth orbit using the proposed Ares I rocket (the "Stick"). Formerly referred to as the Crew Launch Vehicle (CLV), the Ares I consists of a single Solid Rocket Booster (SRB) derived from the boosters used in the Space Shuttle system, connected at its upper end by an interstage support assembly to a new liquid-fueled second stage powered by an uprated Apollo-era J-2X rocket engine. The Orion spacecraft would be lifted into orbit atop this "stack", while a larger launch vehicle (the proposed Ares V) would be used to launch the heavier Earth Departure Stage and Altair.
In January 2007, NASA announced that a different launch vehicle design, the Ares IV, was actively under consideration for the program. If chosen, the Ares IV might replace both the Ares I and the Ares V launch vehicles for some Constellation launches at later dates, or all of them altogether.
