AERODUCT

AERODUCT (Air-Augmented Ejector Ram fairing & Drag-mitigating Flow Controller) originated while evaluating atmospheric rocket launch dynamics. To minimize aerodynamic drag, conventional rockets maintain high aspect ratios, resulting in a slender, pencil-like geometry. However, this layout severely restricts usable fairing volume. Consequently, vehicles like the Falcon 9 opt for a larger fairing with a blunter forebody, whereas the Saturn V utilized a sharper forebody profile reminiscent of the Concorde. AERODUCT merges these structural approaches to optimize both volume and aerothermal performance.

The AERODUCT architecture features a forebody intake similar to classic jet engine configurations. Its primary function is to ingest ram air, heat and accelerate the stream internally, and discharge it at an angle over the aft shoulder of the fairing. This fluidic ejection forms a protective boundary-layer shield around the rocket body, altering the detached bow shock into a weaker oblique shock structure and significantly reducing pressure drag.

The conical nose section accommodates Liquid Hydrogen (LH₂) and 98% High-Test Peroxide. These propellants feed micro-combustion chambers acting as primary ejector drivers to entrain the incoming ram air—extending the fluidic entrainment principles previously applied to hydrogen VTOL airframes. Hydrogen's unique combustion kinetics and low density enable efficient momentum transfer that heavy hydrocarbon fuels cannot match.

In this cycle, the 98% HTP acts as an auto-ignition driver. Catalytically decomposed HTP produces superheated steam and oxygen, raising the fuel-rich (H₂-heavy) driver exhaust above the ignition threshold. Upon mixing in the duct, the hot steam preheats incoming ram air, causing unburned hydrogen to auto-ignite spontaneously with ambient atmospheric oxygen without requiring mechanical or electrical igniters. By utilizing atmospheric oxygen for secondary combustion, the vehicle bypasses the need to carry massive onboard oxidizer reserves within the fairing, operating similarly to an air-augmented turbofan. The consumable propellant mass yields an active fluidic drag shield at a minimal overall mass penalty.

Trajectory and Performance Advantages

The primary objective of the AERODUCT shield is to enable an earlier, more aggressive gravity turn, directly reducing ascent gravity losses. Standard launch trajectories delay pitching over to avoid severe Max-Q dynamic pressure and wave drag in the lower atmosphere. By actively mitigating the shock wave, AERODUCT allows high-speed atmospheric flight while maintaining acceptable structural loads on the fuselage.

The nose shield operates strictly within the dense, oxygen-bearing layers of the atmosphere, terminating near 25 km altitude as the allocated LH₂ supply depletes. Beyond 25 km, the exponential drop in atmospheric density (less than 3.5% of sea level) ensures that the vehicle experiences negligible aerodynamic drag, even as the fluidic shield deactivates. The unpowered intake forms a stagnant air cushion at the apex, behaving like a standard nose fairing while the vehicle coasts through the upper atmosphere at high velocity (Mach 6+). Once dynamic pressure drops near zero, residual HTP is vented to split and self-jettison the fairing halves without pyrotechnics.

Following hydrogen depletion, the AERODUCT assembly functions as a standard payload fairing and is jettisoned. Residual HTP or compressed steam trapped in the forebody manifold is vented through separation nozzles, supplying the kinetic impulse required to split and push the fairing halves away cleanly without adding pyrotechnics or dedicated separation hardware.