Boom Supersonic released the latest design of their ‘Overture’ supersonic passenger aircraft at the Farnborough Airshow back in July.

Designed to carry 65-80 passengers at Mach 1.7 and enter service in 2026 will the Overture aircraft be a boom or bust?

Boom Overture Aircraft

Figure 1: Boom Supersonic Overture

There have been no supersonic passenger aircraft in service since the arguably early retirement of Concorde in 2003. The Anglo-French aircraft was first flown in 1969 and entered service in 1976, technically Concorde was an engineering marvel, commercially it was considered a failure, and in the end only 14 production aircraft were made all entering service with British Airways and Air France.

Concorde was restricted to subsonic flight over land due to the sonic boom generated at supersonic speeds, which severely limited the routes available to fly. A relatively low passenger capacity together with high fuel consumption (at a time of inflating fuel prices) meant that airlines cancelled their orders in favour of high capacity subsonic aircraft such as the Boeing 747.

Concorde only ever flew profitably for part of its service life offering a very expensive niche service primarily between London or Paris and New York.

British Airways Concorde Aircraft

Figure 2: British Airways Concorde G-BOAG

So… What are the challenges?

Many of the challenges encountered by Concorde still exist today, for example sonic booms, high fuel consumption relative to subsonic aircraft and aerodynamic heating of the structure due to friction.

Since the design of Concorde in the 1960s there have been significant advances in materials, the overture design will make extensive use of carbon composites for the wing, fuselage and vertical tail which are lighter, stronger and more thermally stable than traditional metallic materials such as the Aluminium alloys used on Concorde.

A significant problem to be overcome is the high fuel consumption associated with supersonic flight. When in level flight at a constant speed the thrust provided by the engines is balanced by the drag of the aircraft. Drag increases with the square of speed, i.e if you double the speed, the drag increases by a factor of 4. This means 4 times the thrust is required from the engine and that thrust is generated by burning fuel.

Due to the unique operating conditions (sustained supersonic cruise) the engines required for the Overture aircraft are very different to those used on any other in-service aircraft. Boom Supersonic and Rolls-Royce worked together for 2 years to identify a propulsion system to suit the Overture aircraft, but Rolls-Royce have recently decided not to continue the partnership and will instead concentrate on other projects. This leaves Boom Supersonic with no engine supplier and no suitable engines available on the market.

The Sonic Boom
As with Concorde, the Overture aircraft will be unable to travel at supersonic speeds over land due to the environmental impact of noise created by the sonic boom, instead it will travel at high subsonic speeds over land (Mach 0.95) and increase to its supersonic cruising speed of Mach 1.7 over water.

The sonic boom is a continuous ‘bang’ produced when an object travels through the air fastener than the speed of sound, typically a sonic boom sounds like an explosion and is similar in volume to the human ear as a thunderclap.

NASA and Lockheed-Martin are currently working on the X-59 Quiet Supersonic Technology (QueSST) program. The aim of the project being to design and test a supersonic aircraft that reduces the level of a sonic boom to a quiet thump and assess acceptability for supersonic flight over land. The X-59 is due to make its first flight later in 2022.

Nasa X-59 QueSST

Figure 3: NASA X-59 QueSST

What’s next?

Boom have gathered a significant number of pre-orders for their Overture aircraft (as did Concorde), they also have an interest from the US government and Northrop Grumman for a special missions variant of the aircraft.

There are significant technical challenges to be overcome, an engine supplier to be found and with the current high fuel prices and push for sustainability whether the project will ultimately go on to become a commercial success remains to be seen…!

Written by: Principal Stress Engineer, Tom Handford