Exploration Systems Architecture Study

The Exploration Systems Architecture Study (ESAS) is the official title of a large-scale, system level study released by the National Aeronautics and Space Administration (NASA) in November 2005 of his goal of returning astronauts to the Moon and eventually Mars — known as the Vision for Space Exploration (and unofficially as "Moon, Mars and Beyond" in some aerospace circles, though the specifics of a crewed "beyond" program remain vague). The Constellation Program was cancelled in 2010 by the Obama Administration and replaced with the Space Launch System, later renamed as the Artemis Program in 2017 under the Trump Administration.

Scope

NASA Administrator Michael Griffin ordered a number of changes in the originally planned Crew Exploration Vehicle (now Orion MPCV) acquisition strategy designed by his predecessor Sean O'Keefe. Griffin's plans favored a design he had developed as part of a study for the Planetary Society, rather than the prior plans for a Crew Exploration Vehicle developed in parallel by two competing teams. These changes were proposed in an internal study called the Exploration Systems Architecture Study, whose results were officially presented during a press conference held at NASA Headquarters in Washington, D.C. on September 19, 2005.

The ESAS included a number of recommendations for accelerating the development of the CEV and implementing Project Constellation, including strategies for flying crewed CEV flights as early as 2012 and methods for servicing the International Space Station (ISS) without the use of the Space Shuttle, using cargo versions of the CEV.

Originally slated for release as early as July 25, 2005, after the "Return to Flight" mission of Discovery, the release of the ESAS was delayed until September 19, reportedly due to poor reviews of the presentation of the plan and some resistance from the Office of Management and Budget.

Shuttle based launch system

The initial CEV “procurement strategies” under Sean O’ Keefe would have seen two “phases” of CEV design. Proposals submitted in May 2005 were to be part of the Phase 1 portion of CEV design, which was to be followed by an orbital or suborbital fly-off of technology demonstrator spacecraft called FAST in 2008. Downselect to one contractor for Phase 2 of the program would have occurred later that year. First crewed flight of the CEV would not occur until as late as 2014. In the original plan favored by former NASA Administrator Sean O'Keefe, the CEV would launch on an Evolved Expendable Launch Vehicle (EELV), namely the Boeing Delta IV Heavy or Lockheed Martin Atlas V Heavy EELVs.

However, with the change of NASA Administrators, Mike Griffin did away with this schedule, viewing it as unacceptably slow, and moved directly to Phase 2 in early 2006. He commissioned the 60-day internal study for a re-review of the concepts — now known as the ESAS — which favored launching the CEV on a shuttle-derived launch vehicle. Additionally, Griffin planned to accelerate or otherwise change a number of aspects of the original plan that was released last year. Instead of a CEV fly-off in 2008, NASA would have moved to Phase 2 of the CEV program in 2006, with CEV flights to have commenced as early as June 2011.

The ESAS called for the development of two shuttle-derived launch vehicles to support the now defunct Constellation Program; one derived from the space shuttle's solid rocket booster which would become the now cancelled Ares I to launch the CEV, and an in-line heavy-lift vehicle using SRBs and the shuttle's external tank to launch the Earth Departure Stage and Lunar Surface Access Module which was known as Ares V (this design was reused for the Space Launch System). The performance of the Cargo Shuttle Derived Launch Vehicle (SDLV) would be 125 to 130 metric tons to Low Earth Orbit (LEO). A SDLV would allow a much greater payload per launch than an EELV option.

The crew would be launched in the CEV atop a five-segment derivative of the Shuttle's Solid Rocket Booster and a new liquid-propellant upper stage based on the Shuttle's External Tank. Originally to be powered by a single, throw-away version of the Space Shuttle Main Engine, it was later changed to a modernized and uprated version of the J-2 rocket engine (known as the J-2X) used on the S-IVB upper stages used on the Saturn IB and Saturn V rockets. This booster would be capable of placing up to 25 tons into low Earth orbit. The booster would use components that have already been man-rated.

Cargo would be launched on a heavy-lift version of the Space Shuttle, which would be an "in-line" booster that would mount payloads on top of the booster. The in-line option originally featured five throw-away versions of the SSMEs on the core stage, but was changed later to five RS-68 rocket engines (currently in use on the Delta IV Heavy rocket), with higher thrust and lower costs, which required a slight increase in the overall diameter of the core. Two enlarged five-segment SRBs would help the RS-68 engines propel the rocket's second stage, known as the Earth Departure Stage (EDS), and payload into LEO. It could lift about 125 tons to LEO, and was estimated to cost $540 million per launch.

The infrastructure at Kennedy Space Center, including the Vehicle Assembly Building (VAB) and Shuttle launch pads LC-39A and 39B was maintained and adapted to the needs of future giant launch vehicle. The new pad LC-39C was later constructed to support small launch vehicles with the option of constructing LC-39D or resurrecting the former LC-34 or LC-37A pads at the nearby Cape Canaveral Air Force Station used by the Saturn IB for the early Apollo earth orbital missions.

CEV configuration

The ESAS recommended strategies for flying the crewed CEV by 2014, and endorsed a Lunar Orbit Rendezvous approach to the Moon. The LEO versions of the CEV would carry crews four to six to the ISS. The lunar version of the CEV would carry a crew of four and the Mars CEV would carry six. Cargo could also be carried aboard an uncrewed version CEV, similar to the Russian Progress cargo ships. Lockheed Martin was selected as the contractor for the CEV by NASA. This vehicle would ultimately become the Orion MPCV with its first flight in 2014 ( EFT-1), its first crewed flight in 2022 (Artemis 2), and first lunar landing flight in 2024 (Artemis 3). Only one version of the vehicle was constructed to support deep space missions with ISS crew transfers being handled by the Commercial Crew Program.

The CEV re-entry module would weigh about 12 tons — almost twice the mass of the Apollo Command Module — and, like Apollo, would be attached to a service module for life support and propulsion (European Service Module). The CEV would be an Apollo-like capsule, with a Viking-type heat shield, not a lifting body or winged vehicle like the Shuttle was. It would touch down on land rather than water, similar to the Russian Soyuz spacecraft. This would be changed to splashdown only to save weight, the CST-100 Starliner

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