Propellants Ben Keefe Benjamin.Keefe100@mod.gov.uk Dr Jocelyn Peach - - PowerPoint PPT Presentation

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Propellants Ben Keefe Benjamin.Keefe100@mod.gov.uk Dr Jocelyn Peach - - PowerPoint PPT Presentation

Nov 10, 2022 209 likes •421 views

DOSG Science & Technology Developing an Understanding of Variables that Impact on Unknown-to-Detonation Transitions (XDT) in GAP/Nitramine Propellants Ben Keefe Benjamin.Keefe100@mod.gov.uk Dr Jocelyn Peach

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DOSG Science & Technology

Developing an Understanding of Variables that Impact on Unknown-to-Detonation Transitions (XDT) in GAP/Nitramine Propellants

Ben Keefe – Benjamin.Keefe100@mod.gov.uk Dr Jocelyn Peach – Jocelyn.Peach108@mod.gov.uk DOSG Science & Technology – Energetics Vulnerability Insensitive Munitions and Energetic Materials Symposium – Seville, 2019

OFFICIAL

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Overview

  • Introduction
  • Trials Hypotheses
  • Trials Programme
  • Outcomes
  • Conclusions
  • Further Work
  • Questions

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Introduction

  • Following previous work on propellants and booster materials – the UK

commissioned work to investigate the XDT effect in Rocket Motor propellants

  • Specifically on a GAP/Nitramine Propellant
  • Programme put together to investigate whether XDT can be ‘turned off and
  • n’ with minor changes
  • Looking at:

– Bore size – Bore geometry OFFICIAL

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Trials Hypotheses

  • Two main hypotheses to be tested:
  • Changing the bore geometry (including slots) will ‘turn off’ XDT
  • Changing the bore size will ‘turn on and off’ XDT

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XDT No XDT XDT No XDT

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THESE HYPOTHESES QUICKLY WENT OUT OF THE WINDOW

Spoiler alert:

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Trials Programme

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Target Type Notes A Plain smooth-bore motor section, 60 mm long B Stellated-bore motor section, 60 mm long C Smooth-bore half section at the impact side, and slotted half-section downstream D Slotted-bore half-section at the impact side, and smooth half-section downstream E Smooth-bore half-section at impact side, and inert Lexan plate downstream. The separation between the Lexan plate and the half- section was 15, 30 and 45 mm F Smooth-bore half section at impact face and Lexan back plate. In-fills used to simulate an inert down-stream section of the same bore diameter as the live motor G Aluminium cover plate 6 mm thick at impact face, in contact with a solid cylindrical pellet (cylindrical axis in-line with impact direction) and with a Lexan plate downstream. The spacing between the rear face of the pellet and the Lexan plate was 20, 30, 35, 38, 40 and 63 mm H Smooth-bore half-section at impact side, with in-fill inert simulated bore, backed by a solid cylindrical pellet I Smooth bore half section at impact side, with smooth-bore half section at the downstream side, separated by an air gap of 5 mm I’ Smooth bore half section at impact side, with smooth-bore half section at the downstream side, separated by a foam in-fill of 5mm thickness J Slotted bore half-section at the impact side, and Lexan inert plate downstream. The spacing between the Lexan plate and the impact section was 30, 45 and 60 mm

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Outcomes

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XDT No XDT

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Configurations that XDT

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What do all of these have in common?

  • Smooth bore internal

towards when the fragment is striking

  • Energetic impact surface
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Examples of Ignition vs. XDT

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Configurations that DO NOT XDT

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Can broadly fit into two categories:

  • Slotted bore internal towards

when the fragment is striking

  • Inert impact surface
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Example of Slotted Bore

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Slotted Bores

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  • Slotted bore Rocket Motors

do not appear to XDT

  • Hypothesis – The jetting

effect pre-ignites the ‘XDT cloud’ – meaning it has not developed the correct density for XDT to occur

  • Previous work with this work

seems to confirm this hypothesis

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Inert Impact Surfaces

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  • Hypothesis – XDT requires

an energetic secondary surface for XDT to occur

  • Previous work DOES NOT

seem to confirm this hypothesis

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XDT Example Video

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‘Sore Thumb’ Result

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Has the exact same two features seen in the configurations that XDT:

  • Smooth bore internal

towards when the fragment is striking

  • Energetic impact surface

BUT DOES NOT XDT

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New Hypotheses

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So what could be happening? We have two ideas:

  • The nitramine level could have

an impact on whether a material with XDT with less material present

  • The XDT does not happen

directly and the base of the cloud – it could need to happen where the red ‘X’s are to the left

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Conclusions

  • Smooth Bore Rocket Motors have a propensity to XDT
  • Slotted Bore Rocket Motors do not have a propensity to

XDT

  • We have limited ideas as to why the other configurations

did not XDT:

– Low percentages of nitramines in propellants can ‘turn off’ XDT – XDT can sometimes occur further round the bore

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Further Work

  • Further trials to try to understand what is actually

happening

  • Other materials to investigate whether the nitramine level

has a larger impact than previously though

  • Try to model the phenomena

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QUESTIONS

Thank you for listening.

Ben Keefe – Benjamin.Keefe100@mod.gov.uk Dr Jocelyn Peach – Jocelyn.Peach108@mod.gov.uk DOSG Science & Technology – Energetics Vulnerability Insensitive Munitions and Energetic Materials Symposium – Seville, 2019

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