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

One key feature that distinguishes the flowfield around vehicles flying in supersonic and hypersonic regimes is the bow shock wave ahead of forebody. The severe drag and aeroheating impacting these vehicles can be significantly reduced if the bow shock wave ahead of the vehicles forebodies is controlled to yield weaker system of oblique shocks. Benefits of forebody shock control include increasing flight ranges, economizing fuel consumption, reducing dead weights, and thermally protecting forebody structure and onboard equipment. Forebody shock control that has been widely studied since the early 1900s is achievable in numerous techniques that vary according to the mechanism of control. While some of these techniques have already been implemented in real systems, other techniques involve serious complications and tough trade-offs. The present paper is intended to serve as the first comprehensive survey on the field of forebody shock control devices. The objectives of the present paper are multifold. The paper categorizes the various forebody shock control devices in a physics-based manner, explains the underlying physics for each device, and surveys the key studies and state-of-the-art knowledge. The paper also addresses the existing gaps in knowledge, highlights the existing systems implementing these devices, and discusses the associated practical implementation issues and design-tradeoffs.