Smoke and Mirrors

 "Tactical-technical characteristics for design and production of a removable smoke device for the BT-20 tank

Purpose: the smoke device will be installed on a regular BT-20 tank to create smoke screens from standstill or on the move that cover the tank's movement.

Special requirements:

1. The volume of the fluid tank(s) must be at least 120 L.
2. The consumption of fluid must range from 12 to 20 L per minute. The nozzle design must be adjustable to configure the consumption. It is permissible to use two removable nozzles.
3. The smoke device must be slight and compact. The design must be simple, easy to install and remove. It may take no longer than 2 hours for the tank's crew to install or remove.
4. The smoke device must be completely safe for the crew to use. The crew must be able to work without the use of protective equipment (rubber gloves, gas masks, gas suits). The fluid lines must run outside of the vehicle.
5. Installation of the device must not lower the vehicle's tactical-technical characteristics (maneuverability, speed, ability to fire the gun all-round, crew function).
6. The controls for the device must be located in one place and be operated by one person from the fighting compartment. It must be easy, simple, and convenient to operate either in motion or on the move.
7. The device must permit starting and stopping at any moment.
8. The device must work if the tank is tilted (within the tank's characteristics).
9. 90-95% of the fluid tank(s) must still be accessible even if the tank is tilted in the least favourable angle.
10. The smoke device must be flawless in function (no jamming of valves or taps, flawless work of the regulator, ability to purge the lines).
11. The device must permit complete draining of the tank(s) and lines.
12. The smoke device must be sealed completely. The joints must be simple, reliable, and easy to connect and disconnect.
13. The working pressure should not exceed 6-8 atmospheres.
    NOTE: during calculations, assume pressure in air tanks is 140 atmospheres. Take 30% of the general air use to purge the lines.
14. The fluid tank filling neck(s) must allow the tanks to be filled either manually or using a pump.
15. To maintain effectiveness of the device, it is desirable for the smoke fluid to be heated. Using the exhaust gases for this purpose is permitted. 
16. The smoke device must have a fluid level indicator. 
17. The smoke device must be protected by armour, same as the tank.
18. The device must allow for decontamination without disassembly.
    Note: take into experience the design of analogous smoke devices developed by factory #185.

Chief of the Red Army Chemical Directorate, Corps Commander Stepanov

Acting Military Commissar of the Chemical Directorate, Regimental Commissar Dmitriyev

May 11th, 1938"

RGVA F.31811 Op.2 D.842 pp.81-83