Back to Basics: The Spitfire Logic in Hypersonic Age

Modern commercial aviation has been dominated by the circular pressure vessel. While a cylinder is ideal for distributing hoop stress in a pressurized cabin, it creates an aerodynamic and structural compromise at the wing-to-fuselage junction. The design of the the BtBC (Blade the Ballistic Cruiser), allows returning to the foundational engineering principles seen in the Supermarine Spitfire.

The Spitfire featured a profile that was essentially an inverted ovoid with a flattened bottom. This allowed the wing to be integrated as an extension of the fuselage belly rather than a separate attachment. For the BtBC, I have implemented a similar "base-box" architecture.

The bottom of the craft is now a continuous flat surface, dictated by the geometry of the hexagonal LNG and Oxygen tanks. By making the lower tandem wings a single-piece spar that crosses the absolute bottom of the plane, I achieve two critical engineering goals:

1. Structural Continuity: The lift loads from the wing tips are transferred directly across a single member, reducing the bending moments on the fuselage frames.

2. Aerodynamic Cleanliness: At hypersonic speeds, any protrusion creates a shockwave. A flush, flat belly allows the entire aircraft to function as a lifting body, riding the compression shockwave with minimal drag.

While the Spitfire used its flat belly for aerodynamic smoothing, the BtBC utilizes it as a pressure containment plate. Because this aircraft is a VTOL with only 35 cm of ground clearance, the proximity to the tarmac is a benefit, not a penalty.

The unified Tesla valve rocket engines exhaust through a slit geometry integrated into this flat belly. During the initial lift-off, the expanding gases are trapped between the flat lower wing spar and the ground. This creates a high-pressure "fountain lift" effect. At 35 cm, the aircraft sits on a rigid aerostatic cushion, maximizing thrust efficiency before the nose-up clearing maneuver transitions the craft into horizontal flight.

By flattening the fuel tanks to create this Spitfire-inspired belly, I also solved the internal layout problem. The interface between the hexagonal cryogenic tanks and the cabin becomes a perfectly flat floor. This allows for modular avionics and payload systems that are impossible in a circular cross-section. The upper wing, situated less than one meter above the lower wing at this interface, completes a high-rigidity structural plank that supports the entire weight of the craft.

In "back to basics," we aren't moving backward. We are using the proven geometric advantages of 1940s fighter design to solve the most complex problems of 2026 hypersonic VTOL travel.