DARPA wants fast aircraft that don’t need runways

DARPA invites designers to redefine aircraft that can fly quickly and take off and land without runways. Earlier this month, DARPA announced an upcoming “Proposal Day,” to be held March 23, when the Pentagon’s blue-sky project wing will offer input to designers and companies on an initiative it calls SPRINT, which stands for Technologies Independent Speed ​​and Runway Technologies (SPRINT) X-Plane Demo Program. In 42 months, or three and a half years, DARPA hopes to have a demonstration flight of a new plane through the program.

As the name suggests, SPRINT is looking for a fast aircraft, or at least a plane capable of going fast over short distances. The program specifically seeks to develop an aircraft that can travel at 400 knots or 460 mph. This is much lower than the cruise speed of a fighter like the F-16, although it is much faster than the cruise speed of Black Hawk helicopters, which may be the most relevant issue. That’s because the other aspect of SPRINT is that the aircraft should be able to hover in austere environments, such as fields or deserts, without the specific paved infrastructure of a runway or a helipad.

“The objective of the SPRINT program is to design, build, certify and fly an X-plane to demonstrate enabling technologies and integrated concepts necessary for a transformative combination of aircraft speed and runway independence for the next generation of air mobility platforms” , DARPA reports. announcement.

While the open sky is vast, runways remain one of the most demanding parts of flight infrastructure. Once built, a runway is relatively easy to repair after an attack, provided no planes were destroyed at the time of the incoming bombs and missiles. But clearing runway and hangar space, as well as crew and aircraft maintenance, creates a durable target visible from space. As United States war planners explore options should war break out in the Pacific region, the known and fixed locations of existing runways could leave aircraft vulnerable to a surprise attack. Even without the surprise, once airplanes are in the air, they will need a runway, and the loss of that surface can lead to, at best, hard landings on unprepared terrain that damage the airplane and endanger the pilot.

[Related: Bell wants to soup up tilt-rotor aircraft by adding jet engines]

DARPA announced SPRINT on March 1st. The shape of the new vehicle is unspecified, Defense One’s Patrick Tucker reported. “It could be a new form of helicopter, or perhaps a vertical takeoff and landing aircraft that could fly even faster.” Tucker also noted that the DARPA director “deliberately avoided calling the program a vertical lift effort, and an accompanying slide showed two artists’ concepts that did not look decidedly like a helicopter.”

Helicopters, of course, have long been the most reliable form of vertical takeoff, although their design comes with significant limitations in speed and efficiency. Matching a helicopter’s runway independence with the speed and endurance of fixed-wing flight is a problem the military has tried to solve for decades. The most successful variations followed one of two paths. There are tilt-rotor planes, such as the V-22 Osprey and the upcoming V-280 Valor, which have high-mounted wings and rotors that rotate parallel to the ground for takeoff, before turning at a different angle for forward flight. The Osprey can land in austere environments, provided there is clearance for the rotors, although in normal conditions the planes fly and land on special pads at military bases.

The other path, seen on the Harrier Jump Jet and the F-35B stealth fighter, uses an exhaust vent from a jet engine to lift the plane into the sky, before rotating for forward thrust. This enormous amount of heat and power has led to speculation, especially in F-35 development, that the engine would destroy all but the most specially prepared landing pads.

The program is called SPRINT. DARPA

None of the designs presented by DARPA commit to these traditional vertical take-off or landing (VTOL) approaches. One, a silver-shiny image of an airplane with jet-like ducts and folded blades at the ends, has wings arranged like a tilt. In high-flying concept art, the engines used for vertical lift are idle, leaving even more powerful systems to propel the plane into the sky. The V-22 Osprey has a cruising speed of 310 knots, while the V-280 Valor has a cruising speed of just over 280 knots. Both planes have higher terminal speeds for, er, sprinting, but getting to higher cruising speeds will likely mean abandoning rotor motors as the primary form of propulsion, even if they can tilt.

In the other DARPA concept drawing, the image appears as a rendering of a flying wing, reminiscent of the B-2 or B-21 bombers, but with a V-shaped tail. The engines are suggested to be even larger than seen here, with space for fans or rotors that provide vertical lift to the vehicle body, while jet intakes suggest a means of forward propulsion.

This concept art is a type of vision board for what DARPA is trying to achieve. Acquiring a new kind of plane that can fly without runways, helipads or other external infrastructure could extend to where planes operate. Making sure the plane flies fast could make it useful for more tasks than those already performed by helicopters, expanding the scope of what the military can do. And, ultimately, DARPA’s mission isn’t to design finished products—it’s to explore new spaces, believing that once the technology demonstration hurdle is cleared, others will figure out how to bend that new technology into useful form.

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