Deployable Aeroshell Flexible Thermal Protection System Testing

Abstract

Deployable aeroshells offer the promise of achieving larger aeroshell surface areas for entry vehicles than otherwise attainable without deployment. With the larger surface area comes the ability to decelerate high-mass entry vehicles at relatively low ballistic coefficients. However, for an aeroshell to perform even at the low ballistic coefficients attainable with deployable aeroshells, a flexible thermal protection system (TPS) is required that is capable of surviving reasonably high heat flux and durable enough to survive the rigors of construction handling, high density packing, deployment, aerodynamic loading and

In-Flight Aeroelastic Stability of the Thermal Protection System on the NASA HIAD, Part I: Linear Theory

“…Frequency, Hz f crit Critical frequency, at the flutter or divergence boundary, Hz G yθ Shear modulus, P a h Shell thickness, m k Circumferential wavenumber k crit Critical circumferential wavenumber, at the flutter or divergence boundary K s Spring stiffness for the circumferential elastic supports, P a K P Y R Pyrogel spring stiffness, P a/m m Shell mass per area, kg/m 2 m P Y R Pyrogel mass per area, kg/m 2 M Mach number n Axial mode number n crit Critical axial mode number, at the flutter or divergence boundary N a y,tot Total applied in-plane force in y-direction, N/m N a y Applied tension in y-direction, N/m N a θ,tot Total applied in-plane force in θ-direction, N/m N a x , N a y , N a xy In-plane forces applied to the square woven fabric sample, N/m p Complex frequency in the aeroelastic problem, rad/s p s Static pressure differential, P a q Dynamic pressure, P a q crit Critical dynamic pressure, at the flutter or divergence boundary, P a r 1 , r 2 Shell radii at the minor and major ends, respectively, m u, v, w Shell displacements, m w N , w K Out-of-plane displacements of the Nextel and AKK shells, respectively, m U ∞ Free-stream flow velocity, m/s y Coordinate along the shell meridian y 1 , y 2 Locations of the shell minor and major ends, respectivelȳ y Dimensionless shell coordinate, (y − y 1 )/(y 2 − y 1 ) α…”

Advanced High-Temperature Flexible TPS for Inflatable Aerodynamic Decelerators

“…The sled has two sample locations, one "flat" and one drafted up at 5°, allowing for two test conditions (heat rates and pressures) during a single tunnel run. 9 Three video cameras capture each test run, and are mounted to provide coverage of the fore and aft sled test coupons, as well as a three-quarter view of the sled. Test runs are recorded on video, and pre-and post-test pictures are taken of the test coupons in the test fixture as well as photo-documentation of the decompiled layups.…”

Flutter Analysis of the Thermal Protection Layer on the NASA HIAD

“…Specifically, the proposed TPS configuration consisting of Nextel 440-BF20, Pyrogel 6650, and Kapton Kevlar Laminate was studied. Three theoretical structural models were developed based on photographic observations of the experimental test setup as described in previous conference proceedings 1,2 . The piston theory hypersonic flow approximation was used for the aerodynamic pressure in all cases.…”

“…The test article is a multi-layer structure consisting of Nextel 400-BF20, Pyrogel 6650, and Aluminized Kapton Kevlar Laminate. Curvature was estimated based on photographs of the test samples in an earlier AIAA report by Hughes, et al 2 . In all cases, piston theory is used for the aerodynamic pressure.…”