Initial Concept and Setup

• Saw U-Haul advertisement claiming aerodynamic design while walking in Austin
• Decided to test U-Haul aerodynamics at hypersonic speeds (Mach 7)
• Traveled to University of Texas San Antonio hypersonic wind tunnel facility
• Facility managed by Dr. Chris Colmes ("laser eyed Hypersonic Professor")

Hypersonic Vehicle Control Challenges

• Dr. Colmes explanation of high-altitude control difficulties:
  • At high altitude, traditional control surfaces (flaps, fins) don't work
  • Not enough air drag/aerodynamic force
  • Must use control jets/RCS thrusters instead
  • Middle ground altitude creates problems: flaps ineffective but aerodynamic forces still present
  • Hypersonic airflow can rip control jets apart
  • Complex interactions can cause jets to push vehicle in same direction as firing (opposite of Newton's laws expectation)

Hypersonic vs ICBM Comparison

• ICBMs travel faster than hypersonic vehicles (up to 7.8 km/s)
• ICBMs exit atmosphere, travel through space, then dive on targets
• Lofted trajectory gives enemies more detection/intercept time
• Hypersonic missiles cruise within atmosphere at ~half ICBM speed
• Low trajectory means sudden horizon appearance with minimal detection time
• Previously hidden by Earth's curvature

Wind Tunnel Operation Mechanics

• Uses pressure differential between vacuum chamber and pressurized tube
• Separated by metal diaphragm designed to burst at target pressure
• Mach number (7.2) fixed by nozzle geometry, not pressure
• Pressure changes only affect Reynolds number, mass flux, equivalent altitude
• Nozzle works like rocket nozzle: converging section accelerates to Mach 1, diverging section accelerates further
• Physics reversal at Mach 1 throat - like traffic lanes (narrow = slow, wide = fast)
• Could expand further for higher Mach but limited by pressure/temperature constraints

Temperature and Heating System

• Air heated to 700K (800°F) to prevent freezing
• Electric heaters wrapped around pipe with insulation
• Expansion process saps energy from temperature
• Freestream equivalent temperature: 60K (minus hundreds of degrees)
• Cryogenically cold, just above liquefaction point
• True flight enthalpy would require 2,000K heating (material limits prevent this)
• Most facilities operate as "cold tunnels" due to material constraints

Test Preparation and Technical Issues

• U-Haul model: original $7 price, purchased for $40
• Pressure gauge malfunction caused trigger box failure
• 40-minute window during vacuum pump-down to fix issue
• Mad scramble to find short circuit source
• Faulty microcontroller board identified and replaced
• Manual trigger backup plan prepared (1-second camera buffer window)

Safety Procedures

• Laboratory lockdown for pressurization
• "Laser bell" notification system for surrounding labs
• Safety check before reviewing footage

Test Results

• Diaphragm burst at expected pressure (around 300-320 PSI)
• Sound described as "prolonged fart" rather than expected boom
• U-Haul model showed brief stable flight before tipping
• Cab vibrated significantly during static test
• Plastic model survived hypersonic air blast
• Two bow shock waves created complex shock interactions
• Small viewing window limited observation

Future Plans and Model Graveyard

• Potential free flight test discussed
• Models accumulate in vacuum tank bottom
• Periodic undergraduate retrieval missions
• Custom vacuum tank from Ohio company
• Access flanges sized for student arm reach
• Dr. Colmes jokes about fitting misbehaving grad students inside

Content and Platform Discussion

• 27-minute uncut tour available on Nebula
• Nebula subscription: $2.50/month discounted rate
• Platform allows more in-depth content without YouTube algorithm constraints
• Can include complete equation explanations without losing 50% of audience
• Early access and ad-free content for supporters