I. Introduction

The Hypervelocity Wind Tunnel No. 9 located at White Oak, Maryland, site of the Arnold Engineering Development Center (AEDC, formerly the Naval Surface Warfare Center [NSWC]) has long been recognized as a unique world-class, ground-test facility. Tunnel 9 is one part of the AEDC hypersonic complex that includes the von K rm n hypersonic wind tunnels, ballistic Range-G, arc-jet facilities and the aeropropulsion test unit (APTU). The facility differs from conventional "perfect gas" wind tunnels in that it provides naturally turbulent hypersonic boundary layers and, with the new Mach 7 capability, matches velocity directly. For this reason, it is included in this volume of hypervelocity facilities.

The facility was developed in the early 1970s as the latest in ground-test facilities to provide critical low-altitude, high-Mach-number data in support of the Navy's reentry development programs. Since its inception, Tunnel 9 has maintained a leading role in hypersonic ground testing by continually expanding its operational capabilities to match the needs of current and projected programs, maintaining data quality, and understanding customer requirements. Many recent, requirements-driven upgrades have been completed at Tunnel 9 and are the subject of this chapter.

Tunnel 9 started with a unique design built around a state-of-the-art, high-pressure supply heater that provided a clean, high-pressure, high-temperature nitrogen supply fluid. Initial operation realized a Mach 10 and 14 aerodynamic simulation...