This manuscript presents an ultrafast-laser-absorption-spectroscopy (ULAS) diagnostic capable of providing calibration-free, single-shot measurements of temperature and CO at 5 kHz in combustion gases at low and high pressures. Additionally, this diagnostic was extended to provide 1D, single-shot measurements of temperature and CO in a propellant flame. A detailed description of the spectral-fitting routine, data-processing procedures, and determination of the instrument response function are also presented. The accuracy of the diagnostic was validated at 1000 K and pressures up to 40 bar in a heated-gas cell before being applied to characterize the spatiotemporal evolution of temperature and CO in AP-HTPB and AP-HTPB-aluminum propellant flames at pressures between 1 and 40 bar. The results presented here demonstrate that ULAS in the mid-IR can provide high-fidelity, calibration-free measurements of gas properties with sub-nanosecond time resolution in harsh, high-pressure combustion environments representative of rocket motors.
This content will become publicly available on May 1, 2025
Transient plasma enhanced combustion of solid rocket propellants
We demonstrate the use of nanosecond pulse transient plasma (NPTP) to improve the control (and acceleration)
of the combustion of solid rocket propellants. Here, we fabricate end-burning propellant samples (i.e., grains)
with a co-axial center wire electrode using hydroxyl terminated polybutadiene (HTPB), isodecyl pelargonate
(IDP), modified diphenyl diisocyanate (MDI), and ammonium perchlorate (AP) as the fuel, plasticizer, curative,
and oxidizer, respectively. High voltage (20 kV) nanosecond pulses (20 nsec) produce a streamer discharge that
provides electronic throttling of the solid rocket propellant. These studies are carried out over a wide range of
oxidizer mass fractions, including those considered insensitive munitions (IM). In addition, real time imaging is
performed characterizing the plasma-formation, evolution of the ignition process, and plasma enhanced flamefuel
coupling. We believe the plasma-based mechanisms of enhancement are 3-fold: 1.) The plasma provides
highly energetic electrons that drive new chemical reaction pathways via highly reactive atomic species such as
H, O, and Cl, 2.) The plasma sputters chunks of the solid fuel material up into the flame where it is combusted,
producing an agitated flame profile. 3.) The plasma provides increased turbulence and multi-scale mixing due to
hydrodynamic effects (i.e., ionic winds), which further improves the combustion process. Having electronic
control of the burn rate introduces the ability to “throttle” solid rocket motors and introduce new flight profile
options beyond a pre-selected profile such as the typical boost-sustain profile. While we are unable to quantify
the burn rate or thrust from these relatively simple observations, we observe clear evidence of the effect of the
plasma on the combustion of these solid rocket fuels even at high oxidizer content.
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- Award ID(s):
- 1954834
- PAR ID:
- 10553563
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Aerospace Science and Technology
- Volume:
- 148
- Issue:
- C
- ISSN:
- 1270-9638
- Page Range / eLocation ID:
- 109107
- Subject(s) / Keyword(s):
- t
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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