Month: April 2022

Ottawa’s Top Secret Balls

During the peak of the Cold War in the 1950s and 60s, Ottawa was the scene of some high-level, top secret operations involving the latest designs for fighter jets, rockets and computer technology. Most of the research for these “secret weapons” occurred at the National Research Council out on Montreal Road. Shrouded in secrecy, two large spherical structures were assembled that looked like something from a science fiction movie of the time. These were Ottawa’s Top Secret Balls, designed for classified experimentation for the Canada’s ill-fated Avro Arrow program.


A group of scientists that worked on the top secret wind tunnel experiments for the Avro Arrow with the newly constructed Large Vacuum Balls in the background. (image courtesy Emma R. Collection)

At the conclusion of World War II under Operation Paperclip, hundreds of German scientists and engineers were brought to North America to continue their work on rocket propulsion and advanced aviation designs that were being developed in Europe for use against the Allies in the final months of the conflict. Russia had also taken a number of German engineers into their advanced weapons research programs, so the race was on for each superpower of the Cold War to create the latest and greatest in aviation and rocket designs.

German aeronautical engineers during World War 2 had had developed the swept wing design for the first operational fighter jet, the Messerschmitt 262. (image Wikipedia)

Canada’s own Royal Canadian Air Force began looking for a supersonic, missile-armed replacement for the obsolete CF-100 Canuck even before it had entered service and in March 1952, a request for a design was submitted to Avro Canada. 

A supersonic fighter had a whole new set of design challenges for the engineers as it had to overcome the sound barrier, with its inherent “wave drag”.

German research during the Second World War had shown the onset of wave drag was greatly reduced by using airfoils in a swept wing configuration. This provided many of the advantages of a thinner airfoil while also retaining the internal space needed for strength and fuel storage. Another advantage was that the wings were clear of the supersonic shock wave generated by the nose of the aircraft.

The delta wing configuration of the Avro Arrow. (image Wikipedia)

This is when the C-105 Avro Arrow took its shape as a delta wing aircraft design, but in order to study the new “supersonic flight” capabilities a special wind tunnel had to be built to create scale supersonic speeds for test models to be studied. This is when Ottawa’s NRC stepped up and built a whole new complex for supersonic aircraft testing using two immense spherical air chambers, called “vacuum spheres”.

A newspaper article from the 1950s describing the new wind tunnel facility in Ottawa. (image Emma R. Collection)

Designed and built under extreme secrecy in 1950 and with details classified, it didn’t take long for the prying and inquisitive eyes of the media back in the day to report on the two giant iron balls being built out on Montreal Road at the NRC compound. Recently, I was given the classified details of this secret project in the form of a binder of old photos and clippings by a former colleague, Emma Rayana of whom I’d like to thank for the information discussed in this post. (Thanks Emma!)

The binder belonged to a gentleman who worked on the Avro Arrow wind tunnel project who kept a record of the program, of which we will briefly take a look at. 

Article describing the top secret Avro Arrow testing…note the wind tunnel model that the engineer asked to be covered up before photos could be snapped. (image Emma R. Collection)

It seems Canada did not have a supersonic wind tunnel test facility at the time, and likely under the request of Avro, the plans were made to build one at the NRC. The design called for two 35ft diameter welded steel spherical air chambers, that contain air that is then pumped down to create a vacuum off air that was 1/10th the density of normal air. Then air is allowed to rush back into the spheres at speeds of Mach 2.0 as it goes through a wind tunnel that housed the scale aircraft models. The whole process lasted only 30 seconds when the spheres then filled with regular air. 

Plans for the Supersonic Test Lab at the NRC. (image Emma R. Collection)
The Vacuum Spheres under construction in Ottawa at the NRC. (image Emma R. Collection)

Construction was completed in 1951 and the supersonic wind tunnel soon began its testing of the scale models of the Avro Arrow at supersonic speeds, from which data was used to build the full size production Avro Arrow at an accelerated rate without a prototype, only relying on the results from the scale models to go straight into production. During a media interview about the facility, orders were hastily shouted by scientists for NRC staff to quickly cover up the test models so their design was kept classified. 

The completed facility at the Montreal Road campus of the NRC. (image Emma R. Collection)
Newly disclosed government files reveal the scale model testing done at Ottawa’s Supersonic Wind Tunnel on the C-105 Avro Arrow. (image NRC Digital Repository/Library
Test reports and the internal newsletter describing the new Supersonic Wind Tunnel for Arrow testing.

The Avro Arrow was subsequently given the green light in 1955 to be built and then successfully flown on its inaugural flight in March of 1958. The Avro Arrow program was then cancelled a year later in 1959 and orders were given for all 6 Arrows and their plans to be destroyed. An attempt was made to give the completed Arrow jets to the National Research Council of Canada as high-speed test aircraft, but the NRC refused, stating that without sufficient spare parts and maintenance, as well as qualified pilots, the NRC would have no use of them.

Five of the Avro Arrows photographed before destruction. 3 more were under construction but their fate was not photographed.
The Avro Arrows being cutup on the tarmac after the project was cancelled.

Thus, all 6 Arrows were cut up for scrap metal, but rumours circulated that one of the Arrows was taken away to be saved for posterity. These rumours were given life in a 1968 Toronto Star interview with Air Marshal Curtis from the RCAF, who stated he could neither confirm nor deny the rumour. The legend endures that one of the prototypes remains intact somewhere, perhaps in England where an ejection seat from an Arrow surfaced on Ebay.  

An Arrow ejection seat that appeared on Ebay in 2011.

It is not known how much longer the special wind tunnel balls remained in operation at the NRC, or if they are still being used today, but they are clearly still visible on a 2021 Google Satellite image. They remain hiding behind some newer building additions around them at a site called “Building 10”.

This 1965 sateliite image shows the test balls. (image GeoOttawa)
In 1991 the Vacuum Balls are still there…(image GeoOttawa)
A recent satellite image shows the Top Secret Balls still in place, now surrounded by other buildings and obscured from view on the ground. (Image GeoOttawa)

The giant sphere’s may no longer be used for secret Avro Arrow testing, but continue to be part of the enduring mystique surrounding the ill-fated Avro Arrow. 

Andrew King, April, 2022



The Emma R. Collection