Exploring New Ways to Solve Old Problems; the Hunt for Alternative Stability Tests

Abstract

The 80 °C self‐heat test (formally known as the silvered vessel test) is one of the methods the UK uses to assess if nitrate ester based solid rocket propellants are sufficiently stable for service use. However, it uses a large mass of propellant – of the order of 70 g – and so there have always been safety concerns with regards to this technique. Further to this, it is not an internationally recognised test. There has been a desire to find a replacement for the 80 °C self‐heat test since at least the 1980s. One of the key advantages of the method is that it uses a significant mass of material and so is more representative of stabiliser depletion reactions in a solid rocket motor compared with smaller scale ageing tests. It is also considered a reliable method as it will accurately show if a nitrate ester based propellant is sufficiently stable for service use or not. This research, using three nitrate ester based propellants, has shown that the technique which is colloquially named “extreme heat flow calorimetry” offers an alternative to the 80 °C self‐heat test. Further, this method appears to be a new way of assessing the stability of nitrate ester based propellants and it has also been shown to be able to detect changes upon ageing for a particular propellant.