Liftoff and Transition Aerodynamics of the Ares I (A106) Launch Vehicle

Abstract

An investigation has been conducted in the NASA Langley Research Center 14-by 22-Foot Subsonic Wind Tunnel to obtain the liftoff and transition aerodynamics of the Ares I (A106) Crew Launch Vehicle. Data were obtained in free-air at angles of attack from -10° to 90° at various roll angles and at roll angles of 0° to 360° at various angles of attack. In addition, tower effects were assessed by testing with and without a mobile launcher/tower at all wind azimuth angles and at various model heights to simulate the rise of the vehicle as it clears the tower on launch. The free-air data will be used for low speed high angle of attack flight simulation and as a bridge to the low angle of attack ascent database (0.5 < Mach < 5.0) being developed with data from the Langley Unitary Plan Wind Tunnel and Boeing Polysonic Wind Tunnel. The Ares I Database Development Team will add incremental tower effects data to the free-air data to develop the database for tower clearance.

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

“…Section VI describes the final results of the uncertainty model and compares the database and uncertainty model to previous data. [9] describe the test and the data acquired in detail. The objectives of the test were to measure the aerodynamic forces and moments on the Ares I CLV during the liftoff phase of the flight before the vehicle cleared the tower assembly as well as during the transition from high to low angles of attack at low Mach numbers (M < 0:3).…”

“…The limited time and resources available did not allow for a full grit strategy investigation across the entire domain during the 14 22 T591. Instead, the grit study phase of the test provided some information on the effect of the grit configuration on the data and established a reasonable approach to use for the remainder of the test based on available data and previous grit strategy best practices [9]. The WT test team tested five different grit strategies on the CLV model during this phase and selected a uniform grit application to serve as the baseline grit strategy for the other phases of the test.…”

“…The transition phase of the 14 22 T591 acquired data with the sting-mounted CLV model attached to the tunnel support system with a variable pitch-offset mechanism that allowed testing throughout the entire database domain of the total angle of attack ( T from 0 to 90 deg) and the aerodynamic roll angle ( a from 0 to 360 deg) [9]. The variable pitch-offset mechanism had two fixed angles (0 and 45 deg) for the sting-balance-model assembly to attach to the tunnel support system.…”

“…The UQ team could not definitively determine the underlying cause of those differences, but the most likely explanation was that the highly unstable, complex vortical shedding characteristics present in this flow regime for long, axisymmetric bodies [20] led to hysteresis effects in the pitch sweeps using the different setups. The pitch sweeps for the two pitch-offset setups were acquired in opposite directions (one going from lower T to higher T values, whereas the sweeps for the other setup started at T 90 deg and decreased the T values) because of significant model dynamics in 14 22 T591 in the middle of the T domain [9]. The estimated uncertainties for the overall experimental data reproducibility were smaller than the estimated experimental repeatability for T 50 deg, and so the reproducibility term was reduced to zero for that T domain.…”

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.…”