NASA’s Super Guppy
NASA 941, or N941NA, is the last flying Guppy transport in the world. Technically speaking, it is a B377SGT-F, sometimes referred to as a B377SGT-201 Super Guppy Turbine. This is the youngest of the eight Guppies that were manufactured between 1962 and 1980 by a California company called Aero Spacelines Inc.. Originally, a civilian Boeing B377 Stratocruiser aircraft was modified to carry outsized cargo for the fledgling U.S. space program. Nicknamed the Pregnant Guppy (after a NASA official's description that stuck to it), the impetus for the design was that it took eighteen or more days to transport large rocket boosters and other assemblies by barge from the West Coast of the U.S. to Cape Canaveral Florida through the Panama Canal. An outsized cargo aircraft could do it in eighteen hours.
While the first 4 Guppies were extended and enlarged Boeing Stratocruiser and military C-97 Stratofreighter fuselages, the final 4 aircraft were new fuselages mated to reclaimed wings and modified tail sections, fitted with a relatively short pressurized cockpit section of a C-97. When this final Super Guppy was being built, parts had to be taken from the original Pregnant Guppy, which had already been retired and disassembled. It seemed that all of the world's C-97 and B377 airframes had been scrapped and there were few spare parts to be found when this last-of-the-line aircraft was manufactured in 1980. Interestingly enough, the Pregnant Guppy used pieces from the third prototype Stratocruiser, and it can rightfully be said that one of the last flyable Boeing B377 versions has some parts in her tail assembly from one of the original Boeing B377 Stratocruisers!
NASA acquired this Super Guppy Turbine from Airbus Industries in 1997. Airbus had purchased a fleet of four of these outsized cargo carriers in the 1970s to haul partially completed A-300 and A-310 fuselages around Europe between different factories. After replacing the four Super Guppies with their in-house designed Beluga jet transports, a surplus aircraft was offered in a barter agreement between the European Space Agency and NASA to offset some of NASA's cost of carrying European-built equipment to Florida for a pair of Space Shuttle flights to the International Space Station.
Rick Hill, NASA's sole Examiner Pilot for Super Guppy operations, took some time to discuss a few operating quirks that the Super Guppy has while it was on static display at Joint Base Andrews MD in May. There's no power assisted flight controls, and you hand-fly the aircraft all of the time. Maximum flight endurance is around 6 hours, and many times it is limited by the exertions of the pilot and co-pilot. The Super Guppy has a service ceiling of 25,000, and pilot Hull said he only got up to the maximum altitude once, in an empty airplane. It's normal cruise is in the low teens of thousands of feet in altitude. The Super Guppy cruises at around 220 knots at low altitude, 210 knots at and above 15,000 feet. It has anti-ice protection on its inboard wings from an engine bleed air system, but the old fuel-fed heater used to de-ice the outboard wing has been removed. Rick described the large black stripe towards the wing tip as the aircraft's "largest unpowered gauge", used to show if ice is building up on the airframe. The black prop spinners are another useful ice detection device, as it tends to collect there and on windshield wipers first.
There's actually a Mach number restriction placed on the Super Guppy... because the large volume of air moving around the wide frontal area can reach supersonic speeds well before the rest of aircraft can. Although there's not a Mach meter on the aircraft, it's slightly higher than half the speed of sound, or Mach .50.
To load or unload cargo inside the huge fuselage, the aircraft's nose is swung open to the left, on a giant hinge, propelled by a mobile "drive wheel" that extends from the belly of the aircraft. This wheel, attached to the end of a screw jack, works in conjunction with the nose landing gear to support the entire nose. Three fixed screw jacks on the rear of the aircraft hold the rest of it in place. There's no laser readings nor leveling devices to help mate the nose to the rest of the aircraft, which for all intents and purposes is roughly cut in two parts when the nose is swung open. A small red circle the size of an old silver dollar is overlaid on the seam where the fuselage and nose sections join. When apart, this creates two semi-circles, which must align to make a perfect circle before completely mating the two parts of the airplane. Minute adjustments are made to the screw jacks while the parts are inched closer to each other. A small miscalculation could result in a bent airplane. Windy conditions make the task even more difficult, as the open nose section can act like a giant sail. Due to experience, there's a twenty five knot wind limitation to opening the nose. When the two semicircles line up, a hydraulic nose-locking mechanism is employed.
I got a first-rate tour inside the Super Guppy courtesy of NASA flight engineer Michael Robinson. One enters from a fold-down stairway on the right front part of the belly, and immediately must duck down (I'm six feet four inches tall) to avoid a collection of red wires with plugs running through the ceiling joists. These are the aircraft's control cables, with quick connect-disconnect fasteners that allow the nose to detach and rotate to the left. To the right was the drive wheel and screw jack in the stowed position, and ahead is a pair of short stairways up to the cockpit. The cockpit is roomy, with the main flight engineer's console arranged in an "L" behind the copilot station. The control yokes are big and basic, with lots of round gauges, levers and wheels around the panels in front of the pilots. Some of the placards in the cockpit are in French language too, leftover from the Airbus Industries' days of operation. Stepping back into the unpressurized cabin, I was amazed at the size of the fuselage. Wires and cables ran along the sides of the aircraft, with a series of "U" joints in the black cabling to allow for the door to open with the cables still attached. Although it was rather dark inside, a few rivet holes allowed bright sunlight to shine through. The vast amount of ribs and stringers that make up the fuselage are all exposed, looking akin to the inside of a barn. In the tail , a pair of louvers allow outside air (and pressure) to be transferred into and out of the fuselage, as the cargo area is unpressurized. All I could think of was the interior of a blimp hangar as I looked ahead and behind me. Looking forward, you could easily see where Aero Spacelines engineers "plugged in" the C-97 nose section into their fuselage.
As for future uses of the NASA Super Guppy, there are many interesting options being investigated. NASA seems ready to exploit the outsized cargo capacity of the aircraft, and is actively looking for work that it's star airlifter can provide. Now that the Space Shuttle program is done, and the International Space Station is nearly complete, there is little business connected with those programs. The aircraft is registered as a Public Use aircraft, and can be used by other government agencies besides NASA for outsized cargo transport. NASA has hauled a pair of military T-38 jet trainers inside the aircraft, and it has transported V-22 Osprey fuselages too. With Commercial Space a reality, the Super Guppy could conceivably carry civilian spacecraft, assemblies and freight. The process would require an FAA Letter of Agreement for civilian operations, a process that NASA is in its initial stages of investigation right now.
NASA's attention-grabbing Super Guppy is entering its fourth decade of successful oversized cargo transport. On the inside, it looks fragile with its enormous structure and exposed cables and wires. On the outside, it looks big and beefy, with powerful engines and imposing bulk. Some of the anecdotes about the aircraft spoke about the delicate movements needed while closing her massive nose, while another noted the requirement of physical strength to fly her for hours on end. And, a relatively slow aircraft has a speed restriction so some parts of her won't go supersonic. All contradictions aside, there are many reasons when the justification of operating of a one-of-a-kind aircraft is difficult, but the outsized freight-carrying capability that the Super Guppy gives NASA has made it indispensible, and should be for a long time to come too.
Story and Photos By Ken Kula