Stratolaunch’s Roc—the biggest airplane in the world—returned to the sky Sunday, completing its first test flight in more than eight months.
The four-hour and 23-minute mission expanded Roc’s proven test envelope, including a higher altitude, as well as retracting and extending one of Roc’s main landing gear in flight for the first time.
In addition to setting a Roc record for flight duration, the mission pushed its proven test envelope for altitude and speed. The behemoth reached a maximum altitude of 23,500 feet and a top speed of 180 kias, Stratolaunch said, making it Roc’s most productive test flight so far.
During previous flights, the airplane climbed to about 17,000 feet and accelerated to 165 kias. Roc was designed to fly to altitudes around 35,000 feet, reaching a top speed of 500 keas.
“Today’s successful flight demonstrates and validates improvements to the carrier aircraft’s systems and overall flight performance,” Stratolaunch president and CEO Zachary Krevor said in a statement.
Eventually, owners expect the one-of-a-kind, six-engined, twin-fuselage jet to serve as a carrier to air-launch reusable hypersonic aircraft for testing and research.
The test flight—the third in the plane’s history—was wheels up at 8:47 a.m. PT on the 12,500-foot Runway 30 at California’s Mojave Air & Space Port (KMHV). On the flight deck in the right fuselage: pilots Evan Thomas and Mark Giddings, as well as flight engineer Jake Riley.
As you might expect, piloting Roc from a flight deck on the right fuselage makes landing a bit of a challenge.
“You cannot land on the [runway’s] center line,” Thomas told FLYING last December. “The last thing you want to do is swerve back to the center line or try to line up on the center line.” As a result, Stratolaunch pilots train on the sim to offset the airplane to the right side of the runway.
“One of our key parameters for landing is to line up the fuselages with the runway, because our main landing gear are in line, kind of like two big in-line skates.”
Another challenge: the pilots can’t see the entire left wing.
Thomas said Roc’s twin rudders have proved very effective during previous tests for lining up with the runway.
During Sunday’s test, the flight crew retracted and re-extended Roc’s middle main gear on the left fuselage. Remarkably, it was the first time the airplane had retracted landing gear in flight. This initial in-flight gear test was limited as a precautionary measure. Remaining gear will be tested on future flights. Its 8 landing gear and 28 wheels—like its avionics system and its Pratt & Whitney PW4056 turbofan engines—were obtained from retired Boeing 747-400s.
“The partial gear retraction seen during today’s flight is a graduated approach to building confidence in the landing gear and gear door hardware,” Krevor said. “Testing the left main landing gear individually mitigated risk and provided our aircrew with options for landing the aircraft in the event the hardware didn’t perform as expected.”
The team is rounding out a successful Roc carrier aircraft test flight with two low approach maneuvers before landing. We’re excited to get the aircraft on the ground and start analyzing all of the great data we collected today! #LetsRoc pic.twitter.com/FcwHbv8qmo— Stratolaunch (@Stratolaunch) January 16, 2022
In the weeks leading up to this latest test flight, Roc flight crews practiced taxi test runs, operating the airplane’s communications, airworthiness, and all of its subsystems to ensure proper functionality.
Surprisingly, during initial ascent, the winged behemoth packs some actual get-up-and-go. During Roc’s historic first flight in April 2019, the flight crew discovered that the airplane gains altitude much more quickly than expected. Thomas says those initial seconds of flight feel like riding on an elevator.
The Story Behind the Airplane
Roc, built by Scaled Composites, founded by Burt Rutan, was designed as an in-flight launch platform.
Originally, a key purpose for the airplane was to launch small satellites into low Earth orbit from the air, much like Virgin Orbit’s modified 747-400. (Coincidentally, that airplane, nicknamed Cosmic Girl, successfully air-launched seven satellites on Thursday, after taking off from Mojave.)
But Roc’s mission changed after the tragic 2018 death of Stratolaunch founder Paul Allen. After ownership of the company transitioned to Cerberus Capital Management, Roc’s focus shifted to launching hypersonic test vehicles.
Currently, Stratolaunch is developing a reusable, hypersonic, testbed vehicle called Talon, which will be used for flight testing contracts and aerospace research. “We’re intently focused on a hypersonic flight test service and executing the Talon-A flight at the end of this year,” Stratolaunch spokesperson Kate Squires told FLYING.
“We’re well into the double digits for both government and commercial agreements,” Stratolaunch president and CEO Zachary Krevor told FLYING last month. “So there’s clearly a strong market for our services.”
Plans for a fourth flight test are already underway. After that, engineers plan to install a pylon that will enable Roc to carry various launch vehicles. Stratolaunch expects Roc to begin commercial operations later this year.
Eventually, the Pentagon’s Missile Defense Agency is expected to use Talon to provide “threat replication” to help scientists understand how to engage and intercept hypersonic weapons.
Thomas says it took more than eight months to resume flight testing due to the transition to new ownership as well as a “considerable amount” of developments made to the aircraft, including a command-by-wire system on Roc’s massive outboard ailerons and some adjustments to the leading edge of the enormous wings.
How Big Is Roc?
For those who may be a little late to the party, Roc’s wingspan measures 385 feet, which outstretches any of the largest aircraft in aviation history. That includes the Antonov An-225, the Boeing 747-8, the Airbus A380, and Howard Hughes’ H-4 Hercules, aka the Spruce Goose.
Its payload is rated above a half-million pounds and its MTOW is rated for more than a million.
In fact, it’s so big that the middle part of Roc’s wing, between the two fuselages, is 95 feet wide. Also, because the flight deck is located in the right fuselage, pilots are unable to view the entire left wing on the far side of the airplane.
But for Stratolaunch, this third test flight represents something of a new era. Armed with fresh leadership and a new mission, 2022 offers the company a chance to fully prove the aircraft is ready and able to become much more than just “the world’s largest airplane.”