AeroBD | The AERO news Company…FEB 15, 2016, PALMDALE : Amid signs of growing U.S. Air Force and Navy interest in a sixth-generation combat aircraft, Northrop Grumman is accelerating studies of key technologies for directed energy weapons and thermal management, which it says will be fundamental to future capability.

The company, whose last venture into the air dominance arena in the 1980s, the YF-23, lost out to Lockheed Martin’s F-22 in the advanced tactical fighter contest, has unveiled new  images of a pair of optionally manned, tailless concepts aimed at replacing the Raptor and the Boeing F/A-18E/F. While acknowledging there are still more unknowns than knowns about future requirements for the next generation air dominance (NGAD) aircraft, Northrop says technology to cope with dramatic growth in heat loads will be a key enabler to whatever needs emerge.

The increase in heat loads is driven by the development of advanced weapons, particularly airborne lasers, as well as more powerful electronics, sensors and propulsion systems.  The issue, which has already been a factor in early test and operations of the F-35, is expected to challenge all NGAD concepts. Under Northrop’s NGAD umbrella this includes the U.S. Air Force’s F-X requirements (now set to embrace an F-15C replacement in addition to the F-22), as well as the Navy’s F/A-XX mission.

Unlike any previous generation of air dominance aircraft at this embryonic stage, the configuration will be directly impacted by the integration challenges of directed energy weapons. “One of the unique things that happened (on NGAD) is the convergence of aircraft and weapons,” says Tom Vice, Northrop Grumman Aerospace Systems president.  Despite the miniaturization of laser technology and the switch from bulky chemical-based systems to solid-state, electric lasers, Vice says thermal management is still key.

“Even as good as our most advanced lasers are today they’re still only 33% efficient. So if you have a 100kW laser you’ll have to do something like 200kW with an enormous amount of heat.  What do you do with two megawatts, where do you put it without making the aircraft glow?” Mastering this challenge will be the deal breaker for the winning NGAD design, says Vice. “Thermodynamics will be the key discriminator on who wins the next generation of air dominance aircraft,” he says, while adding that superiority in electromagnetics, advanced energy weapons and survivability will all play major roles.

Answers to the heat management problem are being sought by the U.S. Air Force’s Integrated Vehicle Energy Technology (Invent) program, which is working with Boeing to develop adaptive, smart aircraft power systems using model-based design.  “We’ve been tracking Invent,” says Chris Hernandez, sector vice president of the company’s Research, Technology and Advanced Design unit. However he notes that the “work that one contractor is doing in that is supposed to be shared with industry. We are still waiting to see some of that sharing.”

Northrop is therefore working in parallel on its own thermal management technology. “We can’t wait,” Hernandez says. “We have a laboratory with all the power elements in it that are needed to make the laser work running in the lab today.”

Vice adds: “that’s why we are not relying on somebody else and we are inventing new ideas on how to deal with huge amounts of heat.” Although Vice declines to offer specifics, he says the technology will not be in the form of electric accumulators under study as part of Invent.

“If you are accumulating heat at some point you have to got to get rid of it. But it also provides your ‘shot doctrine’,” he adds, referring to the number of shots that could be fired by the laser. “Our idea is if you have a laser onboard, to get a truly limitless magazine you don’t want to have to invoke some limitation of how fast or how far you can fire. That’s why we are thinking through thermodynamics in terms of what if I want to have continuous lasing capability. What if I want to be able to shoot when needed versus, ‘Oh my accumulator is full, now I have to dissipate heat. Bad guys please don’t come next to me airplane until I can figure out how to reject the heat.’ The accumulator, to me, limits thinking, and I want to remove ourselves from that,” says Vice.

Some heat from the weapons and electronics will also be rejected via heat exchangers located in the “third stream” of adaptive engines, also under study by the Air Force Research Laboratory. “The engine technology is going to get advanced by the Vaate (Versatile Affordable Advanced Turbine Engine) program. Until we know how far and how fast, we don’t know what the engine is,” says Hernandez. “We’re assuming that the technologies that will get advanced in Vaate will be transportable to the core of what we decide we need.”

According to Hernandez, much of the NGAD design space therefore remains wide open. “There are things we know about this and things we do not. How far should it go; how fast, weapons, survivability, how maneuverable? None of those answers are known.”

In lieu of firm answers, Northrop’s Advanced Design group, now headed by former Scaled Composites boss Kevin Mickey, has been “building up modeling and simulation capabilities and playing with different solutions to the problem, which is maintain control over a specific area of the sky for a specific amount of time,” says Hernandez.

However with the lessons of the cost of the F-35’s one-size-fits all approach fresh in the memories of both the services and industry, a key focus is also on affordability.  “Everything you want it to do to make it better makes it more expensive. For affordability you can’t make this the be-all to everybody,” Hernandez.  “Our focus has been on looking at technologies and designs and the effectiveness of those solutions against the cost.”

Range will be another important design driver, though perhaps not for the usual reason. “We anticipate limited basing in the future,” says Hernandez. “If range is important, then you’ll need to carry a lot of weapons. The other thing we know is that the adversaries have been increasing their defensive capabilities. So survivability is going to be really important. So this looks like a little baby B-2. That’s Northrop’s sweet spot,” he adds.