Jeremy T. Pinier

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.

Space Launch System Ascent Static Aerodynamic Database Development

This paper describes the wind tunnel testing work and data analysis required to characterize the static aerodynamic environment of NASAs Space Launch System (SLS) ascent portion of flight. Scaled models of the SLS have been tested in transonic and supersonic wind tunnels to gather the high fidelity data that is used to build aerodynamic databases. A detailed description of the wind tunnel test that was conducted to produce the latest version of the database is presented, and a representative set of aerodynamic data is shown. The wind tunnel data quality remains very high, however some concerns with wall interference effects through transonic Mach numbers are also discussed. Post-processing and analysis of the wind tunnel dataset are crucial for the development of a formal ascent aerodynamics database.

Constellation Program Lessons Learned in the Quantification and Use of Aerodynamic Uncertainty

The NASA Constellation Program has worked for the past five years to develop a re- placement for the current Space Transportation System. Of the elements that form the Constellation Program, only two require databases that define aerodynamic environments and their respective uncertainty: the Ares launch vehicles and the Orion crew and launch abort vehicles. Teams were established within the Ares and Orion projects to provide repre- sentative aerodynamic models including both baseline values and quantified uncertainties. A technical team was also formed within the Constellation Program to facilitate integra- tion among the project elements. This paper is a summary of the collective experience of the three teams working with the quantification and use of uncertainty in aerodynamic environments: the Ares and Orion project teams as well as the Constellation integration team. Not all of the lessons learned discussed in this paper could be applied during the course of the program, but they are included in the hope of benefiting future projects.

New Aerodynamic Data Dispersion Method with Application to Launch Vehicle Design

This paper describes a new generalizedmethod for implementing aerodynamic data dispersions in the framework ofMonteCarloflight simulations. As opposed to the traditional pure-bias type dispersionmethods, the newproposed model is a general mathematical approach based on truncated Fourier series that, when combined with physical modeling tailored to the aerodynamic quantity of interest, enables the generation ofmore realistically dispersed data with magnitude, phase, slope variations, and a controlled amount of bias. The new method is also presented in a particular example, as applied to the Ares I-X Flight-Test Vehicle and the Ares I Crew Launch Vehicle rolling moment data. It is shown how the adoption and implementation of this newmethodwithin these projects has resulted in significant increases in predicted roll control authority and has lowered the induced risks forflight-test operations. A direct impact on launch vehicles is a reduced size for auxiliary control systems and the possibility of an increased payload. This technique has the potential of being applied to problems inmultiple areaswhere nominal data together with uncertainties are used to produce simulations using Monte Carlo type random sampling methods. It is shown that physics-based dispersion models, together with nominal data and uncertainties, can make flight simulations more realistic and allow for leaner spacecraft designs.

Space Launch System Booster Separation Aerodynamic Database Development and Uncertainty Quantification

The development of the aerodynamic database for the Space Launch System (SLS) booster separation environment has presented many challenges because of the complex physics of the ow around three independent bodies due to proximity e ects and jet inter- actions from the booster separation motors and the core stage engines. This aerodynamic environment is dicult to simulate in a wind tunnel experiment and also dicult to simu- late with computational uid dynamics. The database is further complicated by the high dimensionality of the independent variable space, which includes the orientation of the core stage, the relative positions and orientations of the solid rocket boosters, and the thrust lev- els of the various engines. Moreover, the clearance between the core stage and the boosters during the separation event is sensitive to the aerodynamic uncertainties of the database. This paper will present the development process for Version 3 of the SLS booster separa- tion aerodynamic database and the statistics-based uncertainty quanti cation process for the database.

Sonic Boom Pressure Signature Uncertainty Calculation and Propagation to Ground Noise

The objective of this study was to outline an approach for the quantification of uncertainty in sonic boom measurements and to investigate the effect of various near-field uncertainty representation approaches on ground noise predictions. These approaches included a symmetric versus asymmetric uncertainty band representation and a dispersion technique based on a partial sum Fourier series that allows for the inclusion of random error sources in the uncertainty. The near-field uncertainty was propagated to the ground level, along with additional uncertainty in the propagation modeling. Estimates of perceived loudness were obtained for the various types of uncertainty representation in the near-field. Analyses were performed on three configurations of interest to the sonic boom community: the SEEB-ALR, the 69 Delta Wing, and the LM 1021-01. Results showed that representation of the near-field uncertainty plays a key role in ground noise predictions. Using a Fourier series based dispersion approach can double the amount of uncertainty in the ground noise compared to a pure bias representation. Compared to previous computational fluid dynamics results, uncertainty in ground noise predictions were greater when considering the near-field experimental uncertainty.

Space Launch System Booster Separation Aerodynamic Testing in the NASA Langley Unitary Plan Wind Tunnel

A wind-tunnel investigation of a 0.009 scale model of the Space Launch System (SLS) was conducted in the NASA Langley Unitary Plan Wind Tunnel to characterize the aerodynamics of the core and solid rocket boosters (SRBs) during booster separation. High-pressure air was used to simulate plumes from the booster separation motors (BSMs) located on the nose and aft skirt of the SRBs. Force and moment data were acquired on the core and SRBs. These data were used to corroborate computational fluid dynamics (CFD) calculations that were used in developing a booster separation database. The SRBs could be remotely positioned in the x-, y-, and z-direction relative to the core. Data were acquired continuously while the SRBs were moved in the axial direction. The primary parameters varied during the test were: core pitch angle; SRB pitch and yaw angles; SRB nose x-, y-, and z-position relative to the core; and BSM plenum pressure. The test was conducted at a free-stream Mach number of 4.25 and a unit Reynolds number of 1.5 million per foot.

Space Launch System Liftoff and Transition Aerodynamic Characterization in the NASA Langley 14- by 22-Foot Subsonic Wind Tunnel

Analytical Mechanics Associates Inc., Hampton, VA, 23666Notice to the ReaderThe Space Launch System, including its predicted performance and certain other features and character-istics, has been defined by the U.S. Government to be Sensitive But Unclassified (SBU). Information deemedto be SBU requires special protection and may not be disclosed to an international audience, such as the au-dience that might be present at the 2015 AIAA SciTech Conference. To comply with SBU restrictions, detailssuch as absolute values have been removed from some plots and figures in this paper. It is the opinion of theauthors that despite these alterations, there is no loss of meaningful technical content. Analytical methodolo-gies and experimental capabilities are discussed; significant technical results are presented; and meaningfulconclusions and lessons learned are provided.

Ares I Aerodynamic Testing at the Boeing Polysonic Wind Tunnel

Notice to Reviewers The Ares I launch vehicle, including its predicted performa nce and certain other features and characteristics, have been defined by the U.S. Government to be Sensitive But Un classified (SBU). Information deemed to be SBU requires special protection and may not be disclosed to an in ternational audience, such as the audience sure to be present at the 2011 Aerospace Sciences Meeting. To comply wi th SBU restrictions, details have been removed from some plots and figures in this abstract. It is the opinion of th e authors that despite these alterations, there is no loss of meaningful technical content. Analytical methodologie s and capabilities are discussed; significant and interesti ng technical results are obvious and still present; and meanin gful conclusions are still present.