Conceptual study on non-ablative TPS for hypersonic vehicles

Abstract

In order to achieve efficient wave drag reduction under non-zero attack angles and avoid the severe aerodynamic heating, a new concept of the Non-ablative Thermal Protection System (NaTPS) for hypersonic vehicles was proposed based on the idea that the conical shock wave angle can be enlarged by lateral jets to push the conical shock away from the blunt body surface. In the NaTPS, a spike-blunt body structure and lateral jets are combined together to develop a new shock-reconstructing system in front of hypersonic vehicles. When the spike acts to recast the bow shock in front of a blunt body into a conical shock, the lateral jet works to protect the spike tip from overheating and push the conical shock away from the blunt body when a pitching angle exists during flight. The experimental flow visualization and the pressure measurements were conducted in a hypersonic wind tunnel for both the conceptual demonstration and CFD validation. Numerical simulations were also carried out to examine the complex flow around the NaTPS. Both experimental and numerical results show that the NaTPS works well for shock drag reduction and thermal protection. The shock/shock interaction on shoulders of the blunt body is avoided due to lateral jet injection and the peak pressure at the reattachment region is reduced by 65% under a 4• attack angle. The lateral jet could be powered either by high pressure gas stored in the tank or by the water evaporation process in which water absorbs the heat from the hot walls of the blunt noses. The jet pressure needed for producing lateral jet is much smaller than for the forward-facing jet from the stagnation point. The advantages of this concept are well demonstrated and its practical application appears promising. Nomenclature

Drag reduction investigation for hypersonic lifting-body vehicles with aerospike and long penetration mode counterflowing jet

“…Also from previous research [44], it was observed that even with smaller angles of attack (< 5°), the long penetration mode vanishes rapidly. Jiang et al [45] argued that even a 2° attack angle will cause large reduction of its performance. However, Daso et al [43] observed that the LPM jet can be present even for angles of attack up to 10°.…”

Forebody shock control devices for drag and aero-heating reduction: A comprehensive survey with a practical perspective

“…By pushing the shear layer laterally away from the spike, the lateral jet significantly reduced the reattachment pressure yielding a better drag reduction. Jiang et al confirmed their findings numerically and proved that lateral spike further enhanced the aeroheating reduction capabilities of the plain spike [304,306]. They recently confirmed that the favorable role of adding the lateral jet diminishes for longer spikes and that freestream Mach number has insignificant impact on the hybrid device effectiveness [307].…”

“…Previous research has shown that adding a jet to the mechanical spike is indeed beneficial. In addition to further modifying the flowfield in the favorable manner, tip and lateral jets can act to reduce thermal loads on the spike/aerodisk tip [306,327]. By this augmentation, a jet can compensate short spikes while a spike can compensate low pressure jets [309].…”

“…Hence, for a given effect, lateral jets require much lower pressure and mass flow rates than tip jets with no thrust penalty [328]. It was even suggested that evaporating water (used as a spike coolant) can be adequate as a source for lateral jet [306]. The main concern with lateral jets is their impact on vehicle flight stability at incidence.…”

Review of wave drag reduction techniques: Advances in active, passive, and hybrid flow control

“…Though for longer spike length, the lateral jet performance was reduced, and drag reduction might be negligible. 318,319…”