NASA's Hypervelocity Free Flight Range: The Biggest Gun in the West

The Hypervelocity Free Flight Range

• 🚀 NASA's facility in Mountain View, California, is the only one of its kind in the US, designed to test hypersonic re-entry vehicles.
• 💡 Unlike traditional wind tunnels, this range uses free-flying models launched at extreme speeds to capture transient effects.
• 🎯 The facility was visited by various YouTube creators, including Joe Barnard, Alpha Phoenix, and astronaut Matt Dominic.

The Two-Stage Light Gas Gun

• 💥 The system utilizes a two-stage light gas gun where conventional propellants accelerate a plunger, which then compresses hydrogen to launch the projectile.
• 📏 Projectiles are precision-machined models, some with adjusted centers of mass, and can be made from various materials to simulate heat shields or catalytic reactions.
• ⚠️ A plastic sabot is used to propel the projectile, but its failure to separate cleanly can lead to dramatic impacts at orbital velocities.

The Test Section and Imaging

• 📸 The test range is approximately 1 meter in diameter and 75 feet long, with 16 imaging locations, each featuring two orthogonal cameras.
• 🔬 A shadowgraph system, using parabolic mirrors and fast shutters (tens of nanoseconds), captures shockwave structures and projectile dynamics.
• 📈 The atmosphere within the test section can be precisely controlled to simulate various re-entry conditions, including adjusting pressure to match Reynolds numbers.

Control Room and Legacy Technology

• 🕹️ The control room houses a blend of 1960s and 1990s technology, including a chain-driven cam sequencer for firing control and older tube-based electronics.
• 📊 Data from digital cameras and slow-motion cameras is processed in a more modern section of the facility.
• ⚙️ The system requires careful sequencing of vacuuming, gas filling, and atmospheric modification for each test, often taking days to set up.

The Counterflow Shock Tunnel

• 🚀 An unused section of the facility features a counterflow shock tunnel, originally designed to simulate velocities similar to lunar return missions.
• 🧱 This system used large tubes, potentially from battleship gun barrels, with burst discs to manage extreme pressures and gas flows.
• ⏳ Although not operational for decades, the remnants of this facility highlight the advanced and unique capabilities NASA has developed for aerodynamic testing.