Imaging spectroscopy of polymer ablation plasmas for laser propulsion applications

Long Jiao, Benjamin S. Truscott, Hao Liu, Michael N R Ashfold, Honghao Ma

Research output: Contribution to journalArticle (Academic Journal)peer-review

8 Citations (Scopus)
360 Downloads (Pure)

Abstract

A number of polymers have been proposed for use as propellants in space launch and thruster applications based on laser ablation, although few prior studies have either evaluated their performance at background pressures representative of the upper atmosphere or investigated interactions with ambient gases other than air. Here, we use spatially and temporally resolved optical emission spectroscopy to compare three polymers, poly(ethylene), poly(oxymethylene), and glycidyl azide polymer, ablated using a 532 nm, nanosecond pulsed laser under Ar and O2 at pressures below 1 Torr. Emission lines from neutrally and positively charged atoms are observed in each case, along with the recombination radiation at the interaction front between the plasma plume and the background gas. C2 radicals arise either as a direct fragmentation product or by a three-body recombination of C atoms, depending on the structure of the polymer backbone, and exhibit a rotational temperature of ≈5000 K. The Sedov-Taylor point blast model is used to infer the energy release relative to the incident laser energy, which for all polymers is greater in the presence of O2, as to be expected based on their negative oxygen balance. Under Ar, plume confinement is seen to enhance the self-reactivity of the ejecta from poly(oxymethylene) and glycidyl azide polymer, with maximum exothermicity close to 0.5 Torr. However, little advantage of the latter, widely considered one of the most promising energetic polymers, is apparent under the present conditions over the former, a common engineering plastic.

Original languageEnglish
Article number013303
Number of pages8
JournalJournal of Applied Physics
Volume121
Issue number1
Early online date6 Jan 2017
DOIs
Publication statusPublished - 7 Jan 2017

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