Overview of Experimental Investigations for Ares I Launch Vehicle Development

The Ares I vehicle architecture was the design outcome of the Exploration Systems Architecture Study (ESAS) in response to the Vision For Space Exploration challenge provided by President George Bush in 2004. The Ares I vehicle was designed to carry astronauts into low-Earth orbit to support the International Space Station as well as provide transportation to destinations beyond low-Earth orbit including the Moon and Mars. As part of the Ares I vehicle development, numerous technical disciplines have been conducting analyses on the architecture to evaluate its mission performance and viability. Since 2005, an extensive aerodynamic experimental wind tunnel testing program has been conducted for a series of Ares I vehicle configurations as the vehicle design matured. These investigations have utilized multiple aerodynamic research facilities across the United States. Wind tunnel testing has been conducted on the Ares I launch vehicle from low speed lift-off conditions to post-separation supersonic conditions. Facilities have included the Langley Research Center (LaRC) Unitary Plan Wind Tunnel (UPWT), the Boeing Polysonic Wind Tunnel (PSWT), the LaRC National Transonic Facility (NTF), the LaRC 14X22 Low- Speed Wind Tunnel, the Arnold Engineering Development Center (AEDC) Von Karman Facilities, and the Marshall Space Flight Center (MSFC) Trisonic Wind Tunnel. Each of the facilities was utilized based on their size, Mach number capability, cost, and productivity. A number of varied test techniques have been utilized during Ares I aerodynamic characterization experimental investigations. Most of the aerodynamic wind tunnel testing utilized internal strain gauge balances to measure integrated forces and moments. Major concerns to the Performance and Guidance and Control disciplines were the axial force and aerodynamic induced rolling moment components of the vehicle. Specifically protuberance effects on rolling moment and roll control authority are a concern during lift-off and ascent. Another test technique that has been utilized in the Ares I vehicle development has been the use of surface pressures to measure distributed loads on the vehicle. One percent scale models have been tested in typical 4-foot subsonic/transonic and supersonic facilities. The slenderness of the vehicle has been a challenge in both the integrated force/moment testing as well as in the distributed loads testing. Distributed pressure loads are used by the Structures and Loads disciplines to assist in the design of the external panels and internal structure of the vehicle. In addition to the ascent aerodynamic experimental testing, some other specialized aerodynamic wind tunnel tests have been conducted. An investigation was conducted to evaluate ground wind loads, launch tower effects, and transition aerodynamics from lift-off to ascent flight. This test provided a database of proximity aerodynamics in the presence of the launch that reduced the risk of vehicle contact to the launch tower. Another specialized stage separation aerodynamic wind tunnel test was conducted in the AEDC Von Karman Facility Tunnel A specifically addressing proximity aerodynamics of the upper stage relative to the first stage. This test provided a more refined stage separation proximity aerodynamic database to eliminate some risk to the program regarding recontact between the two stages during ascent. This paper will provide an overview of the experimental aerodynamic characterization of the Ares I vehicle and detail the impacts the experimental program had on the development of the vehicle. It will also discuss the facilities and rationale for choosing specific facilities. In addition, the different experimental test techniques employed in the experimental program will be described.