Administrator commissioned that a 90-day study be conducted known as the NASA's Exploration Systems Architecture Study (ESAS, Ref. 1) in the period May - July 2005. A major focus of the study was the launch architecture necessary to support a lunar mission. Recommendations of ESAS included a “1.5-Launch Architecture”. A heavy payload launcher (subsequently called Ares V) would place a Lunar Surface Access Module (LSAM) attached to a large Earth Departure Stage (EDS) into low-Eart h orbit. A smaller payload launcher (subse quently called Ares I) would launch the smaller mass Crew Exploration Vehicle (CEV) into orbit for rendezvous with the EDS+LSAM. Following docking the EDS stage would perform the necessary trans-lu nar injection (TLI) burn for the combined vehicle st ack sending the elements int o lunar space. A number of major design changes have been made in these launchers si nce the original ESAS recom mendations. Many have been propulsion system changes where SSME engines have been replaced with RS-68B engines for the Ares V main propulsion, 5-segment SRBs have been replaced by 5.5-segment SRBs, a new J-2X engine has replaced the upper-stage propulsion systems recommended in the ESAS study, and the replacement of the existing 4-segment Solid Rocket Booster (SRB) on Ares I with a new design 5-segment SRB. The Ares I and Ares V designs continue to evolve in efforts to meet the original lunar mission performance objectives to the degree that they are nearly all-new designs, retaining little of the Shuttle-derived heritage recommended in the ESAS study or as authorized by Congress in 2005. Such all-new desi gns can reasonably be expected to follow lengthy and costly development processes. Other launch vehicle options were exam ined in the ESAS study. One of these was a Shuttle-Derive d Vehicle based on “Shuttle-C” concepts which were studied extensively in the 1980's at NASA Marshall Space Flight Center (Ref. 2). In the Shuttle-C approach (Fig. 1), the reusable Shuttle Orbiter was replaced by an expendable cargo carrier wit h an attached SSME and orbit maneuve r propulsion package . The NASA MSFC studies had progressed to the point that a mockup was built of the cargo/propulsion element in the 1980s. Payloads to low-Eart h orbit of up to 60 mt were examine d. However, the approach fell out of favor because of budgetary pres sures at the time. A survey of t he ESAS Final Report indicates that the only side-mount SDVs described were of this "Shuttle-C" variety where the entire cargo carrier is placed into orbit by the SSME main propulsion – in essence flying a Shuttle-type mission with the Orbiter replaced by an expendable cargo carrier. Since before the President’s Vision for Space Exploration was announced, John Frassanito & Associates, Inc. (JF&A), has been studying launch concepts for Earth-to-orbit heavy-lift missions that make extensive use of present Space Shuttle elements. JF&A participated with the Industry Team, in collaboration with NASA, which was formed i n 2004 to study VSE im plementation. The team examined several concepts in detail including an updated version of the Shuttle-C called Concept B (see Fig. 2, Ref. 3) that could deliver 68 mt to LEO, an improvem ent over Shutt le-C. The ESAS study, by comparison, used a similar configuration that could deliver 66 mt to the same circular low-Earth orbit.

Figure 1. Example of Shuttle-C Configuration (Ref. 2)

Subsequent to Industry Team efforts, however, JF&A in 2006 re- examined the Shuttle-C operational approach of orbiting the entire payload carrie r and SSME main propuls ion. It was note d that the Ares V stages the Earth Departure Stage suborbitally and utilizes that stage in two distinct steps to attain a low-Earth orbit as well as conduct a trans-lunar injection ( TLI) propuls ive burn. The ESAS report, however, does not depict a similar suborbital stage approach with propulsion recovery module for the SDV as shown in Fig. 3. 2 American Institute of Aeronautics and Astronautics