Heat Protection Systems Research Articles

An Experiment to Determine Nose Tip Transition with Fluctuating Pressure Measurements

Theme A accurate assessment of the altitude at which nose tip boundary-layer transition onset occurs is required to design and evaluate the heat protection system of high performance re-entry vehicles. Theoretical approaches to the transition phenomena are lacking, consequently the re-entry vehicle designer has relied almost exclusively on experimental data. Although transition onset has been determined on the frustum of R/V's in both ground and flight test experiments, and nose tip transition has been obtained and detected in ground tests with thermal instrumentation, there is a noticeable lack of transition detection techniques based on pressure measurements for the nose tip region. The purpose of this paper is to present the results of an exploratory ground test program to assess possible flight pressure instrumentation concepts to detect nose tip transition for full scale R/V flight test applications. l Specific ground test objectives were: a) to determine the feasibility of detecting nose tip transition by fluctuating pressure measurements using a miniaturized solid-state pressure transducer, and b) to demonstrate that the solid-state pressure sensor can make both steady-state and fluctuating pressure measurements simultaneously in a wind tunnel test for possible flight test application. Simultaneous fluctuating and steady-state pressure measurements were made and transition could be detected on the nose tip frustum 3.3 nose radii aft of the stagnation point. Transition onset was not detected at more forward stations possibly due to a porous nose.

Reflectance and Unsteady Temperature Distribution of Diffuse Reflectors

The applicability of a previously derived solution of the Kubelka-Munk differential equations for the reflectance of an absorbing and scattering material for the case of a zero absorption coefficient to the description of the reflectance of a weakly absorbing, highly scattering material is examined. A solution for the transient heating of a one-dimensional volume reflector is obtained, and the error incurred in the use of the zero absorption coefficient solution is assessed for early times appropriate to the entry heat protection system application. It is found that the small difference in reflectance causes a significant difference in internal temperature.

Implications of maneuvering-range constraints on lifting-vehicle design.

Abstract : The effects of decreases in the maneuvering range angle on the design parameters for a lifting maneuverable spacecraft performing orbital plane changes aerodynamically are investigated. The design parameters considered here are the velocity or propulsion requirements, the heat transfer, accelerations, and total time of flight for the maneuver. The results indicate that these parameters become more critical as the maneuvering range decreases. Specified limits on these design parameters and constraints on the maneuvering range can be superimposed graphically on a single chart, thus defining an allowable maneuvering region. The high heating rates resulting from small-range-angle maneuvers severely restrict the extent of the maneuverability envelope. In order to extend the maneuvering capabilities for small range angles, the vehicle must be designed for high propellent capacity, high g-loading, and sophisticated heat-protection systems. (Author)

Laminar convective heating and ablation in the Mars atmosphere.

Mars atmospheric composition and laminar convective heating and ablation studied to predict performance of heat protection systems during entry