Shuttle Orbiter boundary-layer transition - A comparison of flight and wind tunnel data

9th AIAA/ASME Joint Thermophysics and Heat Transfer Conference

Merski

et al. 2006

An overview is provided of the experimental wind tunnel program conducted at the NASA Langley Research Center Aerothermodynamics Laboratory in support of an agency-wide effort to prepare the Shuttle Orbiter for Return-to-Flight. The effect of an isolated protuberance and an isolated rectangular cavity on hypersonic boundary layer transition onset on the windward surface of the Shuttle Orbiter has been experimentally characterized. These experimental studies were initiated to provide a protuberance and cavity effects database for developing hypersonic transition criteria to support on-orbit disposition of thermal protection system damage or repair. In addition, a synergistic experimental investigation was undertaken to assess the impact of an isolated mass-flow entrainment source (simulating pyrolysis/outgassing from a proposed tile repair material) on boundary layer transition. A brief review of the relevant literature regarding hypersonic boundary layer transition induced from cavities and localized mass addition from ablation is presented. Boundary layer transition results were obtained using 0.0075-scale Orbiter models with simulated tile damage (rectangular cavities) of varying length, width, and depth and simulated tile damage or repair (protuberances) of varying height. Cavity and mass addition effects were assessed at a fixed location (x/L = 0.3) along the model centerline in a region of near zero pressure gradient. Cavity length-to-depth ratio was systematically varied from 2.5 to 17.7 and length-to-width ratio of 1 to 8.5. Cavity depth-to-local boundary layer thickness ranged from 0.5 to 4.8. Protuberances were located at several sites along the centerline and port/starboard attachment lines along the chine and wing leading edge. Protuberance height-to-boundary layer thickness was varied from approximately 0.2 to 1.1. Global heat transfer images and heating distributions of the Orbiter windward surface using phosphor thermography were used to infer the state of the boundary layer (laminar, transitional, or turbulent). Test parametrics include angles-of-attack of 30 deg and 40 deg, sideslip angle of 0 deg, freestream Reynolds numbers from 0.02x10 6 to 7.3x10 6 per foot, edge-to-wall temperature ratio from 0.4 to 0.8, and normal shock density ratios of approximately 5.3, 6.0, and 12 in Mach 6 air, Mach 10 air, and Mach 6 CF 4 , respectively. Testing to simulate the effects of ablation from a proposed tile repair concept indicated that transition was not a concern. The experimental protuberance and cavity databases highlighted in this report were used to formulate boundary layer transition correlations that were an integral part of an analytical process to disposition observed Orbiter TPS damage during STS-114.

Section: Motivation and Backgroundmentioning

confidence: 99%

Section: Test Techniquementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Shuttle Damage/Repair from the Perspective of Hypersonic Boundary Layer Transition - Experimental Results

Horvath

9th AIAA/ASME Joint Thermophysics and Heat Transfer Conference

Merski

et al. 2006

“…An equivalent roughness (K EQ ) method accounts for TPS tile steps and gaps, 7 within each zone, for instance in Zone 3 the allowable pre-flight normalized K EQ is approximately 0.11-in. 8 Unfortunately, this approach was never intended for use during missions to assess damage to the outer mold lines (OML). Tile damages and subsequent repairs represent a significant deviation from the applicability of the existing K EQ framework.…”

Section: Rtf Requirement For On-orbit Assessmentmentioning

confidence: 99%

Overview of Boundary Layer Transition Research in Support of Orbiter Return to Flight

9th AIAA/ASME Joint Thermophysics and Heat Transfer Conference

Horvath

Greene

et al. 2006

A predictive tool for estimating the onset of boundary layer transition resulting from damage to and/or repair of the thermal protection system was developed in support of Shuttle Return to Flight. The boundary layer transition tool is part of a suite of tools that analyze the aerothermodynamic environment to the local thermal protection system to allow informed disposition of damage for making recommendations to fly as is or to repair. Using mission specific trajectory information and details of each damage site or repair, the expected time (and thus Mach number) at transition onset is predicted to help define the aerothermodynamic environment to use in the subsequent thermal and stress analysis of the local thermal protection system and structure. The boundary layer transition criteria utilized for the tool was developed from ground-based measurements to account for the effect of both protuberances and cavities and has been calibrated against select flight data. Computed local boundary layer edge conditions were used to correlate the results, specifically the momentum thickness Reynolds number over the edge Mach number and the boundary layer thickness. For the initial Return to Flight mission, STS-114, empirical curve coefficients of 27, 100, and 900 were selected to predict transition onset for protuberances based on height, and cavities based on depth and length, respectively.

“…Several authors have analyzed the data from these flights to validate designs assumptions. For an initial review of the flight heating results, see Lee and Harthun. 4 Further reviews 5,6,7 of the early flight data (including the first five flights), along with a discussion of the times that boundary layer transition occurred, were first provided at the Shuttle Performance Lessons Learned Conference held at NASA Langley Research Center in 1983. Additional analyses of these early orbiter flight transition results continued and were reported by Poll 8 and Hartung and Throckmorton.…”

Section: Introductionmentioning

confidence: 99%

Review of Orbiter Flight Boundary Layer Transition Data

McGinley

9th AIAA/ASME Joint Thermophysics and Heat Transfer Conference

Kinder

et al. 2006

In support of the Shuttle Return to Flight program, a tool was developed to predict when boundary layer transition would occur on the lower surface of the orbiter during reentry due to the presence of protuberances and cavities in the thermal protection system. This predictive tool was developed based on extensive wind tunnel tests conducted after the loss of the Space Shuttle Columbia. Recognizing that wind tunnels cannot simulate the exact conditions an orbiter encounters as it re-enters the atmosphere, a preliminary attempt was made to use the documented flight related damage and the orbiter transition times, as deduced from flight instrumentation, to calibrate the predictive tool. After flight STS-114, the Boundary Layer Transition Team decided that a more in-depth analysis of the historical flight data was needed to better determine the root causes of the occasional early transition times of some of the past shuttle flights. In this paper we discuss our methodology for the analysis, the various sources of shuttle damage information, the analysis of the flight thermocouple data, and how the results compare to the Boundary Layer Transition prediction tool designed for Return to Flight. Nomenclature