A Roc Rises

Stratolaunch test flies the world's largest airplane—by many metrics—with a view towards air-to-launch operations.

After seven test flights, Stratolaunch’s Roc—the world’s largest airplane by wingspan—is well on its way to achieving operational status as an air-to-launch carrier platform. 

Based at California’s Mojave Air and Space Port (KMHV), Roc is the brainchild of the late Microsoft co-founder Paul Allen. You might say the airplane is steeped in myth and legend. Its nickname was inspired by a mythical bird of Middle Eastern lore, and the airplane was designed and built by Scaled Composites—the company founded by legendary aerospace engineer and designer Burt Rutan.

Roc’s wingspan measures approximately 385 feet—longer than that of any other airplane, including Howard Hughes’s H4 Hercules, the recently destroyed Antonov An-225 Mriya, the Boeing 747-8, and the Airbus A380. To give you additional perspective, the wingspan stretches longer than an NFL football field or the orbiting International Space Station.

Since Roc’s first test flight on April 13, 2019, Scaled Model 351—as it’s officially designated—has consistently met mission goals for altitude, speed, and various systems tests.

Piloting such an unusual aircraft presents unique challenges, as you might expect. Stratolaunch test pilot and director of flight operations Evan “Ivan” Thomas tells FLYING that Roc has a very slow yaw rate that “just keeps going” and requires constant rudder inputs during turns.

“Because of Roc’s unusual Dutch-roll characteristic, you can’t just keep the rudder the same, you have to change it as you’re in the turn because 10 to 15 seconds later, instead of trying to yaw this direction, it’s trying to yaw that direction,” he says.

Roc never flies alone. A Cessna Citation Bravo chase airplane shadows it during every test flight, providing a much-needed observation platform for such a gigantic aircraft.

Although it has plenty of original components, some of Roc’s most critical systems have been salvaged from retired Boeing 747-400s, including the flight deck console, its six Pratt & Whitney model PW4056 turbofan engines, and its landing gear.

“We haven’t modified the gear in any way, but we have modified the systems and how they interact with our airframe,” Stratolaunch lead sub-systems engineer Stuart Yun says. “The original design is incredibly robust.”

Additional elements for Roc were manufactured by Textron Aviation, Gulfstream, and other OEMs.

Roc’s operations tempo is expected to increase as the company works to simultaneously develop an autonomous, hypersonic testbed vehicle. Eventually, the testbed—dubbed Talon-A—will be attached to a sophisticated carrier pylon on Roc’s center wing and launched at an altitude of about FL350.

Because this jet was designed to serve as a carrier, it comes with an especially impressive maximum take off weight (MTOW): 1.3 million pounds.

Expected to achieve operational status sometime in 2023, Stratolaunch has already contracted with the Pentagon to launch Talon-A to provide “threat replication” during planned hypersonic missile tests.

Roc emerges on April 21 from the Stratolaunch hangar at KMHV sporting a carrier pylon for the first time. With the pylon attached under the airplane’s 95-foot-long center wing, pilots put Roc through a series of low-speed taxi tests to gather data on aerodynamic flow and vibrations. [Courtesy: Stratolaunch]
Pilot Evan ‘Ivan’ Thomas says that during takeoff, instead of slowly moving away from the ground, Roc immediately gains altitude. During landing, pilots say ‘the last thing you want to do’ is land wheels down on the runway’s center line. “We actually will train to offset onto the right side,” says Thomas. [Courtesy: Stratolaunch]
Roc’s record-setting wingspan is evident, and its twin fuselages are made mostly of very strong, light-weight carbon fiber materials. The flight deck is located at the front of the right fuselage so the left-seat pilot can have the best vantage point. Roc is so large that the left-seat pilot cannot see the airplane’s entire left wing. [Courtesy: Stratolaunch]
The pylon’s importance is difficult to overstate. The Stratolaunch business model is launching small, autonomous, rocket-powered, hypersonic testbeds for missile research. Measuring 15 feet by 15 feet, the 8,000-pound pylon is made mostly of metallic materials. Components include a wing with a canoe-shaped adaptor—the attach point for hypersonic vehicles. The pylon has a winch that lowers the adaptor to the ground for mating with a payload—the center wing can carry up to 550,000 pounds. [Courtesy: Stratolaunch]
Stratolaunch director of flight operations Evan ‘Ivan’ Thomas, left, and co-pilot Mark ‘Gidro’ Giddings are pictured at the controls during Roc’s second flight on April 29, 2021. Roc’s engine throttles, overhead panel, and flight deck windows were acquired from retired Boeing 747-400s. [Courtesy: Stratolaunch]
Wearing their green flight suits, pilot Chris ‘Duff’ Guarente, left, flight engineer Jake Riley, center, and pilot Evan ‘Ivan’ Thomas, right, crewed Roc’s first flight in 2019. Lessons learned on that first flight? During approach to landing, pilots should give each other more flight cues to keep the airplane lined up during a wing-low landing. Also, based on the flight crew’s findings, engineers made a few flight control changes to adjust for the airplane’s adverse yaw characteristics, including the addition of yaw augmentation. [Courtesy: Stratolaunch]
Pilots test the empty carrier pylon in flight for the first time during Roc’s fifth test flight on May 4. Test cards also included cycling through all landing gear in flight—repeating a test that first took place during a previous flight. Other tests included the yaw augmentation system and autopilot. [Courtesy: Stratolaunch]


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