Copyright © 2015 United Launch Alliance, LLC. Unpublished Work. All Rights Reserved.

United Launch Alliance CAV-2015

Matthew Bloom

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Formed in December 2006 by a joint venture between Lockheed Martin and The Boeing Company

Locations across the United States: – Headquarters in Denver, Colorado – Manufacturing, assembly and integration

operations in Decatur, Alabama and Harlingen, Texas

– Launch operation in Cape Canaveral Air Force Station, Florida and Vandenberg Air Force Base, California

ULA employees approximately 3,400 employees

Since ULA’s formation, there has been a perfect record of 95 successful launches between the Atlas and Delta vehicles

United Launch Alliance Background

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ULA is actively developing the Next Generation Launch System, which has been named Vulcan

ULA and The Boeing Company are working to provide a Cryogenic Propulsion Stage (ICPS) for NASA’s Space Launch System (SLS) rocket

ULA on December 5, 2014 launched the Exploration Flight Test (EFT-1), which carried the Orion capsule into space

ULA is working with The Boeing Company to launch their manned capsule, CST-100 as part of NASA’s CCtCap contract

Emerging Programs Within ULA

http://www.universetoday.com/102582/boeing-commercial-space-taxi-and-atlas-v-launcher-move-closer-to-blastoff/

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Goal: To predict component vibration on the launch vehicle due to the buffet environment induced during transonics flight

Tested a 7% model inside of a transonic wind tunnel

– 11 ft x 11 ft wind tunnel test section – Mach numbers ranging from 0.6 to 1.4 – 25 angles of attack tested at each mach

number – Instrumented with ~300 dynamic pressure

transducers sampled at 100,000 samples per second

Post processed the wind tunnel pressure measurements for all test points, configurations and sensors

– ~1000 test points per configuration

Applied a turbulent boundary layer (TBL) excitation to the model to predict vibration and internal acoustic responses, using results from the wind tunnel data

Recent Wind Tunnel Analysis

Flow

Flow

Results from this zone shown throughout this package

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Angle of Attack Sensitivity

Figure shows no large variation in angle of attack over this portion of the model

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Mach Number Sensitivities at a Given Zone

Plots show how the spectral shape changes with mach number, with a peak occurring around 20 Hz and Mach 0.83

Both plots show the same data, just presented in two different forms

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TBL Definition

VA-One Application of Corcos Model – The narrowband spatial correlation function R takes the following

normalized form:

Boundary Layer Correction term

Fluctuating Pressure Field, Generalized – Corcos Model - separates in-flow and cross-flow parameters

Convection Velocity/ Phase Velocity

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TBL Phase Velocity Results Summary

The figure above shows the method for calculating the phase velocity at a given tunnel condition and vehicle station

Coherence threshold

Coherence region above the threshold

Calculated slopes of the phase

Least squares best fit of the phase in the region of acceptable coherence

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Mach Dependent Phase Velocity

The figure to the right shows the results from the previous slide plotted for every Mach number

Figure shows the phase velocity converges to a relatively small range of values over all Mach numbers

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TBL Decay Coefficient Analysis

Used transducer pairs (both azimuthally and longitudinally) and calculated decay coefficients

For the analysis, assumed UP was 0.7*free steam velocity

– This assumption is valid, since the term is found in both the exponential equation and the normalized frequency

Boundary layer thickness corrections were ignored, because for large thicknesses the correction is negligible

– Boundary layer thickness was not measured during the wind tunnel test

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TBL Decay Coefficient Example

Up

X

e

∆−αω

Square root of coherence

Normalized Frequency Vector

The black lines plotted are the exponential equation shown with varying alphas, from 0.1 to 0.7

Data collected from this test configuration did not completely fit the standard decay coefficient model over the entire frequency range

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Determining a better mathematical fit to the decay coefficients

Expanding the frequency range where the TBL parameters are applicable

Studying predicted model vibration sensitivities due to variations in the defined TBL parameters

Collecting more closely spaced transducer data from wind tunnel tests to better understand the TBL coefficients

Continuing Work on this Topic