Overview of Experimental Investigations for Ares I Launch Vehicle Development

Abstract

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.

Overview of Ares-I CFD Ascent Aerodynamic Data Development And Analysis Based on USM3D

“…The emphasis will be placed on the correlations of CFD results with the available experimental data for selected configurations. This CFD paper complements two other aerodynamic overview reports with the focus on the Ares-I project from the aerodynamic panel perspective [6] and the experimental investigations [9]. Computational results are based on the three dimensional, Reynolds-averaged Navier-Stokes equations with the assumption that the flow is fully turbulent over the entire vehicle.…”

Detailed Uncertainty Analysis of the Ares I A106 Liftoff/Transition Database

“…= axial force coefficient in the body axis system (forebody; i.e., the effects of the aerodynamic forces and pressures on the base of the aft skirt have been removed) C i = generic force or moment coefficient C l = rolling moment coefficient in the body axis system (forebody); moment reference center located at the main engine gimbal point for the first stage C m = pitching moment coefficient in the body axis system (forebody); moment reference center located at the main engine gimbal point for the first stage C n = yawing moment coefficient in the body axis system (forebody); moment reference center located at the main engine gimbal point for the first stage C N = normal force coefficient in the body axis system (forebody) C Q = queried value of a force or moment coefficient by an end user of the database C TRUE = true value of a force or moment coefficient C Y = side force coefficient in the body axis system (forebody) d 2 = bias correction factor h = vehicle altitude, ft h=L = tower-relative vehicle altitude L = height of tower assembly, ft M = Mach number q wind = crosswind dynamic pressure (based on incident wind at vehicle center of gravity), lb=ft 2 q 1 = freestream dynamic pressure, lb=ft 2 R = range of data (maximum value minus minimum value) Re = Reynolds number U C;DBI = database query interpolation uncertainty for the Transition Database U C;DBM = database modeling uncertainty for the Transition Database U C;EXP = experimental uncertainty for the Transition Database U C;Q = uncertainty in the queried value of a database coefficient U C;DBI = database query interpolation uncertainty for the Tower Increments Database U C;DBM = database modeling uncertainty for the Tower Increments Database U C;EXP = experimental uncertainty for the Tower Increments Database U C;Q = uncertainty in the queried value of an incremental database coefficient = angle of attack, deg T = total angle of attack, deg = sideslip angle, deg = denotes an incremental coefficient or value C A = incremental axial force coefficient in the body axis system (forebody) C l = incremental rolling moment coefficient in the body axis system (forebody); moment reference center located at the main engine gimbal point for the first stage C m = incremental pitching moment coefficient in the body axis system (forebody); moment reference center located at the main engine gimbal point for the first stage C N = incremental normal force coefficient in the body axis system (forebody) C n = incremental yawing moment coefficient in the body axis system (forebody); moment reference center located at the main engine gimbal point for the first stage C Y = incremental side force coefficient in the body axis system (forebody) = estimate of the standard deviation a = aerodynamic roll angle, deg I. Introduction…”

“…The Ares I aerodynamics team, spanning several NASA centers, conducted extensive aerodynamic testing and computational simulations in support of the overall vehicle integration effort [1][2][3][4][5][6][7], and the papers in the Ares Special Section of this journal detail these efforts. The Ares I guidance, navigation, and control (GNC) team and other customers used uncertainty estimates provided with each aerodynamic database (DB) to perform dispersion analyses and risk assessment.…”

“…One possible source of bias error in the experimental data was the balance calibration curve fit, and so the UQ team included balance calibration uncertainty in the Transition DB uncertainty model. The balance engineers reported the standard errors of the mismatch between the actual loading and the measured loading based on the curve fit for the calibration as 95% confidence intervals (2) in percent of full-scale load for each balance component. The UQ team converted these values to aerodynamic coefficient uncertainties with 99.7% confidence (3) for the 14 22 T591 data at 40 psf.…”

Aerodynamic Characterization of a Modern Launch Vehicle

“…These vehicles include the Ares I vehicle, which is intended to deliver a crewed capsule to Earth orbit, the Ares I-X, which was the first developmental flight test of the Ares I vehicle, and Ares V, which is a heavy lift vehicle intended to boost other equipment that can be used to deliver the crew and capsule to the Moon and back. Other papers in the sessions of this conference devoted to the Ares project summarize the Ares I-X flight test, 1 the Ares I database development, 2,3 details of the experimental ascent flight program, [4][5][6][7][8] experimental descent program, 9,10 computational studies for both the Ares I [11][12][13][14][15][16] and Ares V projects, [17][18][19] stage separation simulation, 3,5 modeling the effectiveness of the roll control system (RoCS), 13,15 lessons learned concerning uncertainty quantification, 20 aero-acoustic quantification, 21 impact of real-gas effects, 14 plume effects, 22 testing techniques for launch tower interference, 6 venting, 23 flexible vehicle stability, 24 debris transport, 25 and other aspects of the development project. [26][27][28] The current paper gives the general background of the Ares project and includes examples of previous launch programs that experienced pitfalls in characterizing their aerodynamics, summarizes the Ares Aerodynamics Panel, overviews testing and computational strategies, summarizes the workings of both the database team and the uncertainty teams, presents highlights of both the experimental and computational efforts, and lists lessons learned.…”