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VOOZH | about |
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VOOZH | about |
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From the beginning, the point of the Space Shuttle was that it could land like an airplane on a conventional runway. And it did not need to be a runway at the Kennedy Space Center; it could be a runway in California, or in Spain, or even on Easter Island if circumstances called for it. But to be launched again, the Shuttle would need to be returned to KSC.
As explained by Scott Lowther in his book Boeing B-47 Stratojet & B-52 Stratofortress Origins and Evolution, for most of the development period of the Shuttle, the answer was clear: the Shuttle orbiter would use turbofan engines to fly itself back home. If these were not the jet engines that the orbiter would carry onboard throughout the mission for crossrange extension or go-around capability, then they would be engines that could be bolted onto the orbiter as required.
The problems with this plan were many and, in the end, insurmountable (or at any rate not worth the bother of surmounting). So, an orbiter that could fly itself was off the table; no jet engines would be carried onboard and no mounting attachments for jet engines would be provided. Instead, the orbiter would be transported by a large carrier aircraft.
The Boeing 747 was selected as the Shuttle Carrier Aircraft and served in that role successfully for decades. Lockheed, unsurprisingly proposed to use its C-5 Galaxy cargo jet for the role. Both Lockheed and Boeing also proposed highly modified twin fuselage variants of their C-5 and 747 carriers: the twin fuselage versions would have greater lift capability and would suspend the orbiter underneath the wing centre section.
This arrangement had the advantage of letting the carrier simply drop the orbiter during development tests. The sudden loss of weight would cause the carrier to spring upwards while gravity dragged the orbiter downwards; separation would be assured, and was presumed to be safer than releasing the orbiter off the top. Additionally, by suspending the orbiter, the need for additional lift equipment would be reduced. Instead of a massive crane to place the orbiter atop the aircraft, winches inside the carrier aircraft’s wing centre section could simply haul the orbiter up to where it could be latched in place.
Lockheed and Boeing were not the only ones to realize the potential advantages of the multi-body approach for the Shuttle carrier aircraft. Another such design was put forward by John Conroy, designer and builder of the Guppy’ series.
In 1968, Conroy formed another company following the sale of Aero Spacelines the previous year. This new firm was Conroy Aircraft and it gained success by converting a Canadair CL-44 into a large-capacity transport. This was done by adding a larger diameter fuselage, much as was done with the Guppy series, to create the ‘Conroy Skymonster’. Conroy Aircraft also delved into the turboprop conversion of numerous piston engined aircraft, but went out of business in 1972.
One of the conversions was of the Douglas DC- 3, forming the “Turbo-Three`. This aircraft gave the name to yet another company founded by Conroy, the Turbo-Three Corporation. It was at this company in 1974 that Conroy proposed his most audacious aircraft conversion project: the Conroy Virtus.
While several versions of the Virtus were drawn up, the design that seems to have been studied in greatest detail used major fuselage elements from Boeing B-52s. Giants of the sky in their day, in the Virtus the B-52 elements would end up as little more than landing gear pods. These would be connected by means of very stout pylons, to a large rectangular wing of 450ft span (aspect ratio of 9, surface area 22,166sq ft), and to a twin-boom tail. The Shuttle Orbiter, External Tank, two solid rocket motor cases or a dedicated cargo pod could be carried under the centre of the wing, between the pylons.
Ceiling for the Virtus was 35,000ft; cruise speed was 300mph, with a maximum range of 3,000 miles. Four Pratt & Whitney JT9D-3A turbofans provided 160,000lb of thrust. Maximum payload was 375,000lb; gross takeoff weight was 850,000lb.
The Virtus would have been easily capable of either ferrying the Shuttle Orbiter from place to place, or hauling it up to 35,000ft for drop tests. Unlike the 747 carrier aircraft, for those tests the Virtus would not need to dive out from underneath the orbiter; it would simply drop it. Additionally, the large volume between the pylons would permit the transport of all manner of outsize cargo that could not otherwise get proper transportation. A special cargo pod could be carried; shaped much like the Shuttle External Tank, the pod had an interior diameter of 35ft and an overall length of 184.8ft. It could comfortably fit the External Tank within. Empty weight of the pod was 60,000lb; it could contain 3 15,000lb of cargo.
At the time the Virtus received some publicity and even spent time in a NASA-Langley wind tunnel as a 0.0293 scale model, but nothing more than that came of it. Despite the advantages, the negatives were quite large… an essentially all-new, gigantic aircraft is going to be trickier than simply modifying an existing jetliner. Around 1990, the Myasishchev Design Bureau produced the M-90 series of outsize cargo lifters that followed much the same design practices, but these were never built either.
Boeing B-47 Stratojet & B-52 Stratofortress Origins and Evolution is published by Mortons Books and is available to order here.
Photo credit: NASA
Dario Leone: All articles
