The constellation program is already underway with the development of the Orion Crew Module (OCM), Orion Service Module (OSM) and the Ares 1 rocket. But, all of this effort is with the ultimate goal of returning to the Moon, and later to land astronauts on Mars. For that, a great deal more is needed.
The Altair Lunar Lander
The OCM will rendezvous with another vehicle called the Altair Lunar Lander in low Earth orbit. Once coupled, the tandem will fly to the Moon's orbit together. Altair is named for the 12th brightest star in the night sky which appears in the constellation Aquila.
Once the OCM docks with the Altair Lander and the two systems travel to the Moon, the astronauts will be able to freely move between the two components. However, once they reach the Lunar orbit, the Altair will separate from the OCM and begin its descent to the Lunar surface.
Up to four astronauts will be able to travel down to the Moon's surface on Altair. Once there, Altair will provide life support systems for the astronauts for up to a weeks stay. It will be the base of operations on the surface, as the astronauts will venture out to collect samples and conduct scientific experiments.
The Altair Lander will also serve as a support system which will be vital as construction of a future Moon base commences. Unlike previous Moon missions where the sole goal was to explore and conduct short term experiments, future Moon missions will focus on more long term research. To accomplish this, a long term Moon base will need to be established. The Altair Lander will be able to bring components to construct the Moon base. It will also serve as a base of operations during the construction phase.
The Altair will also carry the astronauts back to orbit and reattach with the OCM. And like with the previous Apollo missions, only a jettisoned part of the lander will return to space, leaving part of the Lander on the Moon's surface. The combined system will then begin its trip back to Earth.
Ares V Rocket
Another piece of the puzzle is the Ares V rocket, which will be used to launch the Altair into the Moon's orbit. The Ares V rocket is the big brother to the Ares I rocket currently under development. It will be specifically designed to carry large payloads into low Earth orbit, contrasting with the smaller Ares I rocket which will carry human payloads.
Compared with past rockets and technologies, the Ares V rocket will be a cost effective way of getting large payloads into low Earth orbit. In addition to getting large items, such as construction materials and the Altair Lander into space, it will also transport necessities like food to astronauts that are spending extended periods of time once the Moon base is constructed. It is considered a long term solution for meeting NASA's needs when it comes to large payloads, and therefore is designed to meet a broad range of needs.
The rocket system is a two staged, vertically stacked launch vehicle. It will be capable of delivering 414,000 pounds of material into low Earth orbit, or 157,000 pounds to Lunar orbit. The first stage of the rocket consists of two reusable solid rocket booster. These rocket boosters are derived from the similar units found on the current space shuttle.
The solid rocket boosters are attached on either side of a larger central liquid-fueled rocket. The technology for the central rocket is based on the old Saturn V rocket. The rocket feeds liquid oxygen and liquid helium to 6 engines -- upgraded versions of the engines found on the Delta IV rocket -- that ignite the fuel.
Atop the liquid-fueled rocket resides the Earth departure stage of the rocket system. After separation from the first stage of the rocket, it is propelled by a liquid-oxygen and liquid-hydrogen rocket, called the J-2X. On top of the Earth departure stage is a protective cover that encapsulating the Altair Lander (or other payload).
We are still years away from the next mission to the Moon, but preparations are already underway. The technology needed is close at hand, but there is a considerable amount of testing that needs to be completed. Traveling to the Moon is a very complicated endeavor, but we have been there before, and we will be there again.