During the year or so following the announcement of what became known as the VSE - the Vision for Space Exploration - by President Bush in January-2004, a number of studies were conducted that looked at a variety of launch vehicle options. Existing launch vehicles including EELVs and Shuttle derived systems were the most favored. While Shuttle derived systems started to gain an edge over expendable launch systems prior to Mike Griffin's arrival, they quickly pulled ahead when Griffin arrived at NASA.

The ESAS (Exploration Systems Architecture Study) came up with two launch vehicles - both of which rely heavily on designs that utilize modified versions of current space shuttle systems. The architecture was designed with the notion of supporting Mars missions in the long term, lunar exploration in the mid term, and ISS support in the near term. Two launch systems emerged: a Crew Launch Vehicle (CLV) designed to launch the CEV and a heavy-lift Cargo Launch Vehicle (CaLV) designed to launch large payloads to the moon and Mars. While the functions of crew transport and cargo transport have been separated - something the Columbia Accident Investigation Board recommended, options exist for putting humans atop the CaLV and using the CLV to launch unmanned cargos.

The CLV will be built using a standard 4 segment Solid Rocket Booster (SRB) currently used by the space shuttle. This is actually one of the safest human launch systems - one with 200 flights (two per shuttle launch) since the Challenger post-accident redesign. The SRB will have a second stage powered by one Space Shuttle Main Engine (SSME) which will be discarded whereas its first stage will be recoverable and reused as has been the case in the shuttle program. Atop the CEV will be a launch escape system modeled after the one used on Apollo. Unlike the current shuttle system where escape modes are not available for all portions of the launch and ascent sequence, there are no "black areas" - the crew can escape from the launch vehicle at any point. While the Shuttle has a 1/200 loss rate (crew and vehicle) on ascent, NASA has calculated the CLV/CEV system as having a 1/2000 loss rate.

The CaLV - also based on shuttle derived hardware - will use a modified Shuttle external tank, 5 Block II SSMEs and two 5 segment SRBs. The second stage will have two J2X engines - modified versions of Apollo's Saturn V second and third stage engines. This second stage will also function as the Earth Departure Stage (EDS) to place the hardware needed for lunar missions on its way to the moon much as the Apollo program's SIV-B stage did. This vehicle will be able to place over 120 metric tons of payload into low earth orbit. While the vehicle will be used to support lunar missions, its was sized such that it could loft the several 100,000+ pound elements needed to construct a Mars exploration ship.

The target date for the availability of the CEV/CLV is somewhere between 2011-2012 - a year or two after the targeted retirement of the space shuttle fleet. Coming online in the middle of the next decade will be the CaLV.

Update:

NASA announced on 30-June-2006 the names of the next generation of launch vehicles that will return humans to the moon and later take them to Mars and other destinations. The crew launch vehicle will be called Ares I, and the cargo launch vehicle will be known as Ares V.

Since the original CLV and CaLV plans were announced in 2005, several design modifications have been made to both launch vehicles. These changes are outlined below.

Ares I (CLV):