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19th of September 1962

59 years ago on the 19th of September, the great grand father of the modern-day large volume aircraft like the Beluga and Deramlifter made its first flight. The Aero Spacelines B-377PG Pregnant Guppy.

When more and more airlines phased out their piston aircraft in favour of the jetliners, also the Boeing 377 Stratocruiser was retired by many airlines. At the same time, NASA started to realise that transporting rocket parts via barge was not only time consuming but also expensive. Two men, Leo Mansdorf (Aircraft broker with plenty of Stratocrusiers in his yard) and John Conroy, an ex-USAF pilot, came up with the idea of modifying a Stratocruiser so that tot could transport rocket parts for NASA. When pitching their idea to NASA, where their idea was met with mixed feelings, and people stated it looked more like a pregnant Guppy than an aircraft. (A name that would stick!). After organising finances for the project Conroy founded Aero Spacelines with the intention to built and operate the aircraft.

Extensive modifications were performed on an ex PanAm Startocruiser. Besides the obvious bubble fuselage, with a diameter of nearly 20 feet (6 meters), the fuselage was also stretched, by inserting a 16 1/2 foot (5 meters) plug aft of the wing. This plug was a fuselage section of an ex British Airways Stratocruiser. Other parts of the aircraft, wings, cockpit, tail and engines remained untouched. To facilitate loading the entire tail could be removed from the aircraft

.An archive picture showing the loading of a 3rd stage Saturn V section with the complete tail removed.

During the first flight, the only difference observed by the crew was a somewhat lower speed of the aircraft as a result of the increased drag. Other handling characteristics were similar if not identical to the original Stratocruiser. For operations during warm days with heavy payload solid rocket fuel engines (4 in total) could be fitted to assist with the take-off

In the summer of 1963, the Pregnant Guppy began flying operationally for NASA. The savings for NASA using the Pregnant Guppy were huge, in today's currency, more the $130 per mile (1.6 km). As demand for the aircraft grew it was decided to develop more large volume aircraft, they would be known as the Super Guppies. (see our blog from the 31st of August, click here)

A comparison between the original Stratocruiser and the Guppy family

Specification for the Aero Spacelines B-377PG Pregnant Guppy:

  • Crew: 3

  • Capacity: 34,000 lb (15,422 kg)

  • Length: 127 ft 0 in (38.71 m)

  • Wingspan: 141 ft 3 in (43.05 m)

  • Diameter: 20 ft 4 in (6.20 m) cabin height

  • Height: 31 ft 3 in (9.53 m) to top of fuselage; 38 ft 3 in (12 m) overall

  • Wing area: 1,769 sq ft (164.3 m2)[citation needed]

  • Cargo compartment : volume: 29,187 cu ft (826 m3)

  • Cargo compartment : total length: 80 ft (24 m)

  • Cargo compartment : constant-section length: 30 ft (9 m)

  • Cargo compartment : max height: 19 ft 9 in (6 m)

  • Cargo compartment : max width: 19 ft 9 in (6 m)

  • Cargo compartment : max width: 8 ft 7 in (3 m)

  • Empty weight: 91,000 lb (41,277 kg)

  • Max takeoff weight: 133,000 lb (60,328 kg) (later increased)

  • Powerplant: 4 × Pratt & Whitney R-4360-B6 Wasp Major 28-cylinder air-cooled radial piston engines, 3,500 hp (2,600 kW) each

  • Powerplant: 4 × Aerojet-General 15KS-1000-A1 solid-fuel assisted take-off rocket engines, 1,000 lbf (4.4 kN) thrust each for 15 seconds

  • Propellers: 4-bladed Hamilton-Standard Model 34E60-387 constant-speed fully-feathering propellers


  • Maximum speed: 320 kn (370 mph, 590 km/h)[citation needed]

  • Cruise speed: 195 kn (224 mph, 361 km/h) normal operating speed

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