Surface Step Induced Gap Heating in the Shuttle Thermal Protection System

Abstract

An analytical study has been performed to investigate the excessive heating in the tile-to-tile gaps of the Shuttle Orbiter Thermal Protection System due to stepped tiles. The excessive heating was evidenced by visible discoloration and charring of the filler bar and strain isolation pad that is used in the attachment of tiles to the aluminum substrate. Two tile locations on the Shuttle Orbiter were considered: one on the lower surface of the fuselage and one on the lower surface of the wing. The gap heating analysis involved the calculation of external and internal gas pressures and temperatures, internal mass flow rates, and the transient thermal response of the Thermal Protection System. The results of the analysis are presented for the fuselage and wing location for several step heights. Nomenclature A c = cross-sectional area for flow B = width of flow path h = tile step height k = thermal conductivity K p = permeability constant m = mass flow rate M = Mach number P = pressure q = conduction heat flux Re c = Reynolds number for base pressure correlation s = straight line length between points T = temperature w = tile-to-tile gap width X, Y = Shuttle Orbiter coordinates AJf = longitudinal coordinate measured in the downstream direction from the point of separation kXff = longitudinal coordinate measured in the upstream direction from a forward-facing step <5= velocity boundary-layer thickness 6* = boundary-layer displacement thickness 6 eff = d for laminar flow, 1.56* for turbulent flow A = sweep angle of a tile with respect to the local flow \L = viscosity coefficient p = density

Experimental Investigation of the Mechanical Behavior of the Strain Isolation Pad in Thermal Protection Systems under Tension

“…Large-scale, heavy-duty launch vehicles, reusable space-to-ground transportation systems, and hypersonic vehicles have emerged as global research hotspots. This type of aircraft suffers from severe aerodynamic heating issues due to its hypersonic flight speed [1][2][3]. As a result, a thermal protection system (TPS) is one of the critical structures that insulates high heat flow, resists the impact of loads such as aerodynamic noise, and ensures the aircraft fuselage's integrity.…”

Numerical investigation of heat flux distribution in a deep gap based on chemical equilibrium

“…Experimental work in this area focused on ground tests (Avery, 1978, 1985; Throckmorton, 1976; Wieting, 1970; Weinstein and Avery, 1975). So far, there have been some disputes about the heat transfer mechanism in a gap (Brewer et al , 1973; Pitts and Murbach, 1982; Petley et al , 1984). The narrow geometry of a gap makes it hard to observe flow characteristics in the gap by experiments.…”

Length-to-Depth Ratio Effects on Aerodynamic Surface Quantities of a Rarefied Hypersonic Gap Flow

“…For instance, the thermal protection systems of the space shuttle orbiter require gaps between the used protection elements to account for thermal expansion. 1,2 For the optimized design of gaps and protection elements, it is necessary to predict the flow conditions and thermal loads as accurate as possible. In the case of reentry vehicles, the boundary layer transition prediction is a requirement to define the thermal protection system.…”

“…1 Moreover, the gap flow structure can become even more complex if the gap dimensions are deformed by thermal or mechanical loads. 3,4 A lot of experiments and numerical simulations 1,2,3,4,5,6,7,8,9,10,11 have already been conducted to investigate the flowfield structure on gaps. The majority of these research studies on gaps has gone into considering laminar or turbulent flow over a wide range of Mach numbers in the continuum flow regime.…”