Current reusable launch systems—such as SpaceX’s Falcon 9 and Super Heavy—rely heavily on propulsive retro-burns (boostback, entry, and landing burns) to return first-stage boosters to the launch site. While effective, reserving propellant for return maneuvers imposes a severe payload fraction penalty, forcing heavy missions to rely on expensive downrange drone-ship logistics.
This article presents a mass-efficient alternative: a Tension-Stayed Hollow Airfoil Architecture. By utilizing high-altitude hypersonic lift-to-drag (L/D) dynamics, an empty booster stage can execute a fuel-free 180° aerodynamic U-turn at 40-50 km altitude. By replacing traditional cantilever spar structures with internal pure-tension fiber cables enclosed within a pressure-equalized, low-drag aerodynamic fairing, structural mass overhead is reduced from 25-35% down to 6-9% of stage dry mass.
1. System Structural Architecture
Classical aircraft wings rely on cantilever spars and internal ribs to resist high root bending moments. Scaling this to a 30-ton dry booster stage yields excessive dead weight. The proposed design decouples structural load-bearing from aerodynamic shaping.
Load-Path Resolution
Internal Cable Network: High-tensile carbon or continuous basalt fiber cables resolve 100% of aerodynamic lifting forces into pure axial tension. Tensile loads anchor directly into the booster's internal aluminum-lithium or carbon-composite ring bulkheads.
Upper Composite Membrane: Takes primary compression-lift and vortex-lift loads during high-angle-of-attack entry, transferring structural forces into the tension cable network.
Lightweight Lower Fairing: A non-structural, thin ceramic/composite textile shell that closes the underside cavity. It prevents supersonic cavity pressure drag on ascent while remaining structurally un-stressed.
Internal Pressure Equalization: Passive microporous venting channels connect the internal wing volume to reference pressure zones. This ensures the pressure differential across the lower skin remains near zero, protecting the lightweight lower fairing from ballooning or collapsing under ascent crosswinds.
2. Flight Envelope & Aerodynamic Dynamics
The winglets utilize a Concorde-inspired compound delta planform (ogival geometry) with high leading-edge sweep (65°-75°) and a root chord of approximately 4.0-6.0 meters, projecting outboard by 0.4-1.5 meters.
Ascent Phase (Mach 0 → 6): At zero angle of attack, the winglets sit behind the vehicle's nose bow shock envelope. The swept profile minimizes wave drag while providing passive aerodynamic roll damping and shifting the aerodynamic center of pressure rearward for enhanced static stability.
High-Altitude Re-Entry Phase (Mach 6 → 2): At staging altitude (h ≈ 40-50 km), the empty booster pitches to high angle of attack (α = 25°-35°). The windward face generates an oblique compression shock and leading-edge vortex sheet, achieving a hypersonic Lift-to-Drag ratio of L/D ≈ 1.5-1.8.
Required Lift Force: To execute a 2.5g turn on a 30-ton dry booster stage in thin atmosphere (q ≈ 4.5 kPa), the system generates approximately 735 kN of lift, reversing the velocity vector without firing main engines.
3. Comparative Architecture Analysis
Key Conclusions
1. Elimination of Boostback Fuel: Reversing a booster's velocity vector using atmospheric lift saves tens of tons of propellant, directly bypassing the exponential penalization of the Rocket Equation.
2. Structural Efficiency via Pure Tension: Utilizing internal carbon/basalt tension cables enclosed within a pressure-equalized hollow fairing captures the structural strength of cable-stayed load paths while eliminating parasite drag on ascent.
3. Default RTLS Capability: The high-altitude glide extension converts Return-to-Launch-Site (RTLS) into the standard operational recovery mode for nearly all mission profiles, eliminating ocean-going drone-ship logistics and saltwater corrosion risks.
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