Design, Analysis, and Tests of a Shuttle-Type Heat-Pipe-Cooled Leading Edge

Abstract

A one-half-scale heat-pipe-cooled leading edge model was designed and fabricated to verify feasibility and performance of a full-scale Shuttle-type orbiter design. Model performance was investigated experimentally by radiant heating and aerothermal tests and analytically by using a simple technique which predicts heat pipe startup from the frozen state and also predicts transient and steady-state thermal behavior. Analytical results agree well with experimental results for startup and steady-state heat pipe operation. The results indicate that variations in angle of attack and roll orientation had a negligible effect on heat pipe performance. The heat pipes effectively isothermalized the leading edge, and reduced peak temperatures to levels compatible with the use temperatures of superalloys. Results of these tests demonstrated the durability of the heat-pipe-cooled leading edge in withstanding Earth-entry thermal and mechanical loads and indicate that the use of heat pipes in leading edge structures is a reliable concept for fully reusable hypersonic cruise and space transportation systems. a D So h I I T -M m P R Rn T r* 7 X Nomenclature speed of sound inside diameter of heat pipe gravitational constant latent heat of vaporization chordwise surface distance measured from nose total chordwise surface distance measured from nose to end of leading edge Mach number molecular mass of working fluid pressure heat flux sonic heat transport rate universal gas constant Reynolds number temperature temperature above which continuum flow conditions are assumed to exist in the vapor space time temperature difference angle of attack angle of roll ratio of specific heats mean free path viscosity density P = Subscripts c =combustor / = liquid max = maximum s = stagnation t = total v = vapor oo = free stream

Thermal Management at Hypersonic Leading Edges

“…by heating fuel). Several heat pipe concepts have been explored [33], [34], [35], [36], including the development of a heat pipe leading edge for the Space Shuttle Orbiter [33]. ________________________________________________________________________ Because passive concepts suffer from both excessive mass (case 1) and low fracture toughness (case 2), and the added complexity of an active concept is not desirable, we limit further discussion here to the passive concepts of cases 3 to 5; namely ablative, hot structure, and heat pipe TPS, which are most suited for the thermo-mechanical stress state at a hypersonic vehicle's leading edges.…”

“…The concept of coupling heat pipes to leading edges has received only limited investigation [34], [35], [36], [75], [76]. Nearly all leading edge heat pipe concepts employed arrays of hollow circular tubes or channels either metallurgically joined to a high temperature skin or embedded in a wedge-shaped composite [33], [34], [35], [36].…”

“…Nearly all leading edge heat pipe concepts employed arrays of hollow circular tubes or channels either metallurgically joined to a high temperature skin or embedded in a wedge-shaped composite [33], [34], [35], [36]. The heat pipes were bent to conform to the radius of the leading edge.…”

“…Iso-Mach lines ( ) have been added for reference. Flight data compiled from [3], [7], [20], [21], [22] (a) An Orbiter leading edge developed by NASA using a Hastelloy X and sodium working fluid [33], and (b) a Mo-Re heat pipe embedded in a RCC leading edge skin [35] Carolina, mankind has aspired for faster flight vehicles which push the limits of engineering.…”

Heat-balance Thermal Protection with Heat Pipes for Hypersonic Vehicle

“…4). This model was tested by a series of radiant heat and aerothermal tests at NASA LaRC from 1977 to 1978 to verify heat-pipe transient, startup, and steady-state performance [12][13][14]. In 1979, to optimize a heat-pipecooled wing leading edge for a single-stage-to-orbit vehicle, Peeples's [15] study indicated that the mass of a shuttle-type heat-pipe-cooled leading edge could be reduced by over 40 % by use of a more efficient structural design.…”