Hypersonic VTOL

I would like to propose radical design changes to the Hypersonic VTOL I had proposed earlier. As you may have recognized from my designs, I am in favor of increasing the L/D ratio of my designs. This results in a tandem bi-plane design. This may work up to a point for low supersonic flights. However, for hypersonic flights, the ideal aircraft has a much lower L/D ratio. I call its approximation a rocket flight, while classical rockets have almost no lift.

My latest aircraft resembles a shape from my earlier designs; it looks like a squished cone. However, only the nose and the tail of the aircraft follow the delta wing curve. In order to maximize the plane's wetted area hidden behind the shock waves, this design change had to be made. I propose a wide-body cabin with 8 seats per row. For 25 rows, we would get 200 passengers. Such planes benefit from single-class passengers; this simplifies servicing, lowers the cost for all, and makes the flight accessible to the masses.

The fuselage will feature a nose section resembling an F1 car's nose structure. This nose section will house the Liquid Natural Gas (LNG) tank. The lightweight LNG tank shifts the Center of Gravity toward the rear, which is optimal for this aircraft's stability loop. Additionally, this cryogenic fuel is utilized to cool the nose of the plane during high-speed atmospheric friction. The preheated fuel is then pumped to the rear core rocket engines and the nose VTOL engines. The cabin's floor will be placed very close to the flat underbelly of the plane. The LNG fuel is also routed to cool the heat generated at the flat underbelly due to compression shock waves. This preheating cycle simultaneously helps to pressurize the LNG tank without consuming additional onboard fuel.

Due to the plane's exposure to extreme stagnation temperatures at hypersonic speeds, the fuselage material must be carefully selected. I opted for the same stainless steel alloy architecture utilized by Starship. The plane will feature a thin external skin reinforced by corrugated sheets directly behind it. These corrugated sheets strengthen the fuselage frame and act as internal cooling channels allowing the LNG to flow and keep the skin structurally stable.

The plane will not have conventional wings. Instead, the top and the bottom profiles of the plane will be flat surfaces. In case of emergency, applying an angle of attack will generate sufficient compression lift on these flat surfaces. This flat layout, coupled with the high-profile nose LNG tank, leaves no visual forward sightline for the pilots. I am planning to attach an optical periscope to the nose of the plane to allow the pilots to have a direct frontal view in case of emergency. Normal flight operations will depend entirely on advanced external cameras and synthetic vision displays. The pilot cabin will be equipped with side windows for manual peripheral orientation.

The rear section of the plane, immediately after the cabin terminates, houses a trapezoidal extension that transitions the straight fuselage into a delta-wing-like tail. This trapezoidal section will house the Liquid Oxygen (LOX) tanks on either side, while the center section is allocated as a pressurized luggage bay.

The main propulsion block will be located at the upper section of the plane. It consists of a giant duct that runs from near the nose section to the absolute rear of the aircraft. The front of this duct is aerodynamically closed. Instead, the upper section functions as a porous intake skin featuring varying hole sizes and geometries (graded porosity). The holes close to the nose are larger and more densely packed, whereas the holes toward the rear become progressively smaller and less dense. The main thrust engines are placed at the entry threshold of the trapezoidal section. These rocket engines feature slit nozzles that eject their fuel-rich exhaust at a 15-degree angle toward the rear opening of the duct.

This ejected rocket exhaust gas violently entrains the atmospheric air sucked through the graded roof holes of the 12.5-meter intake plenum section. The cruise flight ceiling of the plane is set to 28 km altitude. This allows the plane to harvest sufficient air mass for entrainment as well as the necessary atmospheric oxygen to afterburn the fuel-rich exhaust gases. This drastically lowers the onboard LOX mass requirement for the cruise phase. The active air suction from the top of the plane creates a localized low-pressure zone that works efficiently from zero speed up to Mach 6.0. This is the primary lifting architecture that allows the plane to fly horizontally with a 0° angle of attack, significantly reducing wave drag and avoiding sonic blockages.

The duct will feature two vertical structural supports running from the leading edge to the trailing edge. The final part of the duct, where the hot exhaust gas is entrained and mixed with the ambient air, will house rudders on each vertical support for redundancy. This allows the plane to maneuver with almost zero external air drag, as directing the high-velocity exhaust gas provides rapid and precise thrust-vector control. The exit of the duct expands outwards, matching the divergent trapezoidal shape of the rear. This divergent duct geometry allows the entrained, burning air-fuel column to expand freely and exit the nozzle at maximum velocity. The absolute end of the duct houses dual flaps. They are utilized to divert the main exhaust thrust downward to generate vertical lift during VTOL operations, allow the plane to adjust pitch attitude during transition, and double as high-speed ailerons.

The VTOL architecture of the plane is composed of dual, redundant rocket engines placed at the bottom rear section of the nose cone, balanced by the main engine's thrust-vectoring trailing flaps.

The plane will take off vertically in a nose-up attitude, and the main engine's rearward vector component will immediately allow the plane to gain horizontal speed, rapidly transitioning the weight of the aircraft onto the aerodynamic lift loop to minimize the fuel burn of the VTOL engines. Sucking air through the top of the plane generates a structural lift force even at a complete standstill, enabling a highly energy-efficient takeoff and landing profile. The plane's cruise parameters are locked at an altitude of 28 km and a cruise velocity of Mach 6.0.

Architectural Addendum: Scaled Engineering Parameters

1. Unified Mass & Geometric Dimensions

Maximum Takeoff Mass (MTOM): Estimated in the 200,000 to 220,000 kg range. This accommodates a 20,000 kg passenger/baggage payload, internal cabin pressurization, and a wide-body layout.

Fuselage Width: Scaled to 9.0 meters to allow an 8-seat abreast twin-aisle commercial seating configuration.

Upper Deck Porous Plenum: Spans a 12.5 meter length over the cabin, yielding a total upper deck footprint of 225 m².

2. Air-Augmented Suction & Lift Logic

By maintaining a 20% Porosity Ratio, the roof provides approximately 45 m² of actual open hole area.

At Cruise (Mach 6, 28 km): The rear engine block maintains a low-pressure expansion inside the duct. Because this suction acts on the exterior skin, it generates a steady vertical lift vector that allows the wide-body fuselage to maintain level flight at a perfect 0° Angle of Attack, drastically minimizing wave drag.

At Sea Level (VTOL Lift-off): The system does not wait for ram air. The dense ambient atmosphere (1.225 kg/m³) is actively vacuumed through the roof holes by the ejector action of the core engines. This provides an immediate aerodynamic lift cushion right on the launch pad, reducing the vertical workload and fuel strain on the main VTOL thrusters.

3. Integrated Propulsion Efficiency (Iₛₚ)

Because the 12.5-meter plenum captures a massive, continuous stream of atmospheric air, the engine functions as a Dual-Mode Air-Augmented Rocket.

The onboard Liquid Oxygen (LOX) is restricted strictly to the internal 40-bar core pilot torches to ensure flame stability.

The vast majority of the combustion oxygen is harvested directly from the atmosphere via the upper deck holes to feed the afterburner phase. This leverages the incoming air mass as free working fluid, lifting the net methane specific impulse (Iₛₚ) into the 1,800 to 2,400 second envelope—far exceeding any conventional rocket.

4. Reliable Performance & Range Estimates

Because the aircraft is air-breathing from the ground up to 28 km, it avoids the massive propellant penalties of traditional space-launch vehicles.

Thrust-to-Mass Decay: As the plane cruises and burns methane, it becomes lighter. A lighter airframe requires less engine vacuum to sustain lift, meaning the fuel burn rate automatically tapers down and optimizes over the course of the flight.

True Operational Range: Factoring in the highly efficient air-breathing climb, a steady Mach 6 stratospheric cruise, and a high-speed subsonic helical descent, this wide-body architecture safely commands a realistic global range of 11,000 to 13,000 kilometers.

This performance baseline ensures reliable, non-stop intercontinental city-pair transits (e.g., London to Tokyo) inside an operational flight window of roughly 60 to 75 minutes.

Emergency Parasail & Low-Altitude Recovery Architecture

For standard recovery operations, the aircraft executes a high-velocity helical (spiral) descent profile to manage its high subsonic stall speeds (516 km/h passive / 357 km/h active). By maintaining a continuous, banked spiral glide well above its aerodynamic breakdown limits, the wide-body fuselage safely bleeds altitude while keeping the active upper-deck suction loop engaged. The final transition to vertical VTOL mode occurs strictly within the last few hundred meters of descent, keeping the terminal thruster burn down to a brief 30 to 45 seconds to optimize landing fuel.

In the event of a catastrophic system anomaly—such as a total loss of propulsive suction during approach—the aircraft relies on a multi-stage Emergency Parasail System housed within the upper spine of the trapezoidal tail. Because the pressure-fed liquid methane/LOX VTOL thrusters have minimal moving parts, an un-executable landing is statistically rare, making a deployable textile asset a highly acceptable safety trade-off.

When triggered, high-energy mortar charges deploy a series of drogue chutes to rapidly stabilize the 130-ton hull and drop forward velocity below 250 km/h. At this gate, a cluster of ultra-high-strength synthetic parasails deploys to establish a stable vertical descent rate of less than 7 m/s. The flat, reinforced underbelly matrix acts as a sacrificial structural crumple zone during a paraglided ground impact, ensuring total passenger cabin survivability without requiring an operational landing pad.