NASA's Constellation program is a new spaceflight program which aims to develop the technologies and experience needed to open new frontiers in space, including sending astronauts back to the moon and possibly even to Mars. It will replace the current Space Shuttle program, which will be retired after assembly of the International Space Station (ISS) is complete.
With the planned retirement of the space shuttles, Constellation will need a new launching and space transportation system. Three booster rockets are currently in the testing stage. Ares I, which is intended to launch mission crews into space, completed its first test launch on October 28, 2009. The Ares IV and V, designed to launch all other hardware, have not yet been test launched. The Ares IV will be a medium-heavy launch vehicle, while the Ares V will be the most powerful rocket ever built: capable of lifting up to 188 tonnes into Low Earth orbit.
Orion, the planned crew compartment for the Constellation program, is being designed in three parts: a crew module similar to the previous Apollo Command Module but nearly three times as large, a service module which will hold consumable supplies as well as the primary propulsion systems, and a launch abort system which can separate the crew module from the booster rocket in an emergency. Unlike Apollo, the planned Orion module actually has a real toilet and even a food warmer. NASA plans to design several versions of Orion. Block I will be used exclusively for ISS and other orbit missions, while Block II and Block III are intended for deep space missions. Each crew module will be reusable for up to ten flights.
For lunar missions, Constellation will use the Altair lunar lander. The name is a link to Apollo 11's Eagle: Altair is a bright star in the constellation Aquila, or 'Eagle'. Like the Eagle, Altair will be in two parts: the descent stage and the ascent stage. Unlike the Eagle, all of Aquila's crew will be able to go down to the lunar surface, without the need to leave one person behind in orbit. No Altair spacecraft have yet been built. They will not be reusable.
All space expenditures these days are controversial, and the Constellation program is no exception.
The original planned retirement of the space shuttles in 2010, four years before the earliest that Ares/Orion can be made operational, has created a logistics dilemma. The only space vehicle available to fill the gap is the Russian Soyez spacecraft, which has limited return payload capacity, not to mention some heavy political baggage.
One possibility is to keep the shuttles flying past 2010, but because the shutdown had already been underway, many specialty contracts have already been terminated. In many cases, the businesses involved have also shut down, since the Space Shuttle program had been their only customer. At best, former Space Shuttle program director Wayne Hale believes that there would have to be at least a year without any shuttle flights whatsoever while the program reboots.
It goes without saying that this won't be cheap. An initial $2.5 billion USD to keep the shuttles flying until all planned missions have been completed, regardless of date, was approved by the U.S. Senate Budget Committee on March 30, 2009. The final bill may be higher still.