Condign volumes 1 to 3

Read from the scan by GLM-OCR; expect the odd misread word.

# UNCLASSIFIED UK RESTRICTED

## LINKED VORTEX RINGS

1. Quite apart from the possibility of water spouts, dust eddies, whirlwinds and similar atmospheric vortex phenomena, which can be reported as UAPs, there is the possibility of linked vortex rings, such as those filmed from the US spacecraft Challenger on its post-launch ascent. It is suggested that aerial formations of this kind may be related to the UK sightings of the type shown at Working Paper No.11, Figures 2 to 7.

## 2. Experimental Vortices

Experimental work has been done on linked vortex rings and this phenomenon has been modelled. Initially the vortex rings are formed separately. Under certain conditions, when collisions occur, linking is possible of distinctively separate rings. Some results shown at Figures 1(a) and (b). The appearance of linked vortices to an observer clearly depends:

- The viewing aspect.

- The relative position of the viewing light source.

3. If the ring assembly is rotating slowly then the component strands might be visible. The Challenger example cited shows the complex component strands (which, overall, could be described as being contained in a cylindrical volume) rotating (rolling) about its radius at an estimated rate of about 50-60 times a minute. However, if the structure was not rotating and viewed, for example, end-on, it would appear as either a solid ball, reflecting light according to the scattering of its component particles or as a dark spherical

silhouette if between the sun (or light source, such as light cloud background) and the observer.

4. Challenger Spacecraft Video Recording The few extant reports on this topic (which were fortuitously connected with the Challenger incident only because the Department had collected open-source material on this space-launch) are not connected with UAPs, since the unusual effects are studied purely from the interest of fluid physics. However, the brief footage taken by the Challenger crew seems to be very similar indeed to a number of UAP reports received by the Department. Some examples are at Figure 2. Unfortunately the imagery taken from the video does not do justice to the original, which can clearly be seen 'rolling', or 'tumbling', as described above.

5. No attempt has been made in this brief investigation to correlate the 'linked vortex' postulation with the conditions for their formation in the atmosphere or of a possible combination of this effect with an electrical/charged particle or EM field effect.