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The development and proof testing of many types of medium-caliber ammunition entails measuring the round's performance while it is moving inside the gun barrel. These in-barrel events--propagation of the propellant pressure wave, acceleration, balloting, spin, and electronic functions--occur at very high speeds. (Balloting refers to off-boresight movement of a round in a gun, typically due to gas leakage around the ammunition and the elasticity of both barrel and round under the high pressures associated with firing.) RF-based telemetry techniques do not work well inside a gun's metal barrel. An onboard recorder (OBR) is the only way to collect the desired performance data.
While large OBRs have been used to obtain data on larger rounds , it is not a trivial matter to pack the necessary functions into a volume small enough to fit inside medium-caliber ammunition such as a 25 mm round. Controlex has accomplished this with the CM346 miniature solid-state recorder (see Figure 1, page 22).
Other Technical Challenges
The short time that the fired round is in the barrel, accelerating from rest to supersonic speeds in a few milliseconds, creates very short …