Airbus Sees a Future Where Jets Have Rocket Engines

A prediction of what the airliner could look like. (Photo courtesy of PatentYogi/YouTube.)

Airbus recently filed a second patent for an airliner that includes a rocket engine. The addition of the rocket engine could potentially enable travel at more than four times the speed of sound. This would be fast enough to travel from London to New York in one hour.

The design uses rear fuselage mounted turbojets with novel anti-drag flaps ahead of the intakes.

Shaped much like speed brakes, the flaps deflect air flow around the turbojet compressor faces during supersonic flight. This reduces that amount of drag that would otherwise make the concept impossible.

Four decades ago, the Concorde pioneered supersonic air travel, but was restricted to subsonic flight over populated areas due to the problem of sonic booms.

The Airbus design cleverly eliminates this problem by achieving supersonic flight in a vertical, rocket powered climb, which generates a horizontal sonic boom that doesn’t reach the ground. The Airbus proposal indicates the engines could push the aircraft to the near reaches of suborbital space.

Once at cruising altitude, the turbojets would be restarted and high-speed cruise would continue until the descent for landing.

There are some unanswered questions. How will the Airbus design deal with airframe heating at near hypersonic speeds? How will it handle the difficulty of using conventional turbojets at very high altitudes and high speeds?

One solution may be a clever intake design such as the one used in the Lockheed SR-71. The SR-71 used Pratt and Whitney J58 engines that generated the majority of high speed thrust by exploiting ram air flowing around the engine core.

Another issue is fuel efficiency. The SR-71 required expensive, specially blended fuel, and was refueled in mid-air to achieve transcontinental range.

Whether the Airbus design could be scaled up to the point where the internal fuel tanks would be sufficient for transatlantic range seems problematic. There is also the question of how to insulate the rocket oxidizer tank which would likely be fueled with liquid oxygen.

Hypergolic rocket fuels (those that can ignite spontaneously on contact) are a possibility, but the oxidizers have historically been highly toxic and corrosive.

Faster than Concorde speeds at reasonable operating costs and minimal environmental damage seems like an impossible specification, but Airbus engineers appear to be thinking about real world solutions.

For more information, visit the Airbus website.