BMP-1 with prototype side skirts

In the 1970's and early 80's, Soviet AFV engineers were tasked with developing countermeasures to a new emerging detection threat: radar systems used to detect ground-based targets. Existing solutions, such as radiation-absorbing paint, were no longer deemed effective. One of the theoretical solutions was to design mountable louvre-type sideskirts. The layout was arranged to create a wave-like pattern, with each slat strip to be placed vertically at an angle. With this type of layout, the panel would diffract incoming waves within a high degree of asymmetry, scattering the wave. 

General design of the proposed louvre-style panel

To confirm the theoretical results, full-scale measurements of the BMP-1's radar characteristics were done. One measurement without the louvre-style panels and the other with them. Only 70% of the new sideskirt was covered with louvre-style grills, which accounts for roughly 25% of the BMP-1's total side profile. 

The average effective surface was considered in the ±7.5° sector, relative to azimuth angles a = 60, 75 and 90°. 

Simplification of results: 

    Results showed that the average wave attenuation parameter, especially at 90°, was reduced by about 2,5 times. Maximum reduction was detected at roughly 6x wave attenuation. More detailed numeric and explanatory results can be found in the references.  

Based on the results, it is also possible to use such a panel-based louvre-grill layout to dissipate thermal radiation. To improve wave disruption and attenuation, the grills could theoretically be made out of different materials that have properties beneficial in regard to absorbing radio waves. Providing a universal masking solution for various detection spectrums. 

Taken from: 

1. Вестник бронетанковой техники, № 5, 1980 - Повышение маскировки машины экранами типа жалюзи