At the Paris Air Show, Raytheon and Northrop Grumman announced they have formally agreed to collaborate on building an air-breathing hypersonic weapon for DARPA and the US Air Force. Under the new partnership, the two companies will develop, produce, and integrate scramjet combustors built by Northrop into Raytheon's hypersonic tactical missiles.

Hypersonic weapons have been getting a lot of attention in recent years. This isn't surprising, because a tactical missile capable of traveling over five times the speed of sound would be able to breeze past any defense system currently deployed. It would so alter the battlefield of tomorrow and even, potentially, the balance of power that all the major powers and a few of the medium ones are actively developing research programs in the field.

One major problem is how to power such missiles. Currently, most hypersonic vehicles are rocket propelled, which means that they are boosted to speeds above Mach 5 (3,709 mph, 5,969 km/h) and then glide the rest of the way. That may work for test vehicles, but for a practical weapon, sustained powered flight is needed and that means some sort of air-breathing engine.

Under the new agreement that is part of a US$200 million Hypersonic Air-breathing Weapon Concept (HAWC) program contract with DARPA and the US Air Force, Raytheon and Northrop are concentrating on speeding up development of a new scramjet engine for the Raytheon missiles.

A scramjet is similar to a ramjet in that it uses the forward velocity of the vehicle to compress incoming air instead of relying on turbine blades. However, where a ramjet slows down the incoming air to subsonic speeds before using it to burn fuel, the scramjet keeps the airflow in the supersonic range. This allows it to operate at much higher speeds and altitudes while cutting down on heat because the air is compressed less.

According to the partners, using a scramjet means that hypersonic vehicles will have higher and sustained speeds, shorter flight times, and subsequent increased weapon survivability, effectiveness, and flexibility.

"The Raytheon/Northrop Grumman team is quickly developing air-breathing hypersonic weapons to keep our nation ahead of the threat," says Thomas Bussing, Raytheon Advanced Missile Systems vice president. "This agreement combines Raytheon's decades of tactical missile expertise with Northrop Grumman's extensive scramjet engine development experience to produce the best possible weapons."