A paper by AAE Professor Timothée Pourpoint and his team was selected for the 2021 AIAA Liquid Propulsion Best Paper Award from the Propulsion and Energy Forum held virtually this past August.

AIAA celebrates the authors of innovative research presented at its various forums, which also include the areas of aviation and defense.

Professor Timothée Pourpoint

The technical paper, "Chemical Composition of Mixed Oxides of Nitrogen using Raman Spectroscopy," outlines the development of an in-situ technique to measure the chemical composition of different Mixed Oxides of Nitrogen (MON), a class of oxidizers most often used to hypergolically ignite (i.e. auto-ignite) monomethylhydrazine in space vehicle propulsion systems.

"The non-destructive method developed in this work will be useful in determining unknown MON compositions, whether in-situ, in propellant feed systems, or for further characterization of MON properties where accurately knowing composition is critical," the authors wrote.

Other team members include Alicia Benhidjeb-Carayon, mechanical engineer II at the NASA Jet Propulsion Laboratory, California, who earned her PhD under Pourpoint at Purdue; Jason Gabl, senior test engineer; Robert Orth, consulting chemist; and AAE master's student Catriona M. L. White, all part of Pourpoint's Aerospace Propulsion and Energy Conversion Systems laboratory; and Victoria M. Boulos, a Ph.D. candidate in Purdue's Department of Chemistry.

"What's exciting to me is the recognition that understanding these MON propellants and their properties is very important for upcoming moon missions, even upcoming missions to Mars," Pourpoint said.

The work is sponsored by the NASA Marshall Space Flight Center Office of the Chief Technologist and the NASA Game Changing Development Program under NASA's Space Technology Mission Directorate.

"The key aspect of this paper is to understand exactly how the composition of the oxidizer changes with conditions as simple as temperature and pressure. It matters because some of the components in MON are liquids at room pressure and temperature, others are gases, and — like any chemical species — all can change phase with pressure and temperature," Pourpoint said. "If the composition changes, then all the properties like density, viscosity, thermal conductivity, etc. of any given MON mixture change. Really, what we've been tasked by NASA to do is to measure these properties as a function of MON composition, all the way from the freezing point to the boiling point of the oxidizer.

"Many of the rovers and the systems that are being planned by NASA and private companies to land on the moon in the next 10 years will use these propellants. That's a lot of my work."

His team's work also is grabbing the interest of others in the space industry.

"We are in talks right now about making a device that could be used by various entities to check the quality of the propellant in-situ, thereby verifying its concentration as it is going to the rocket engine," Pourpoint said. "Perhaps even better, since it is expensive to synthesize MON, we could check the concentration of the propellant and even the presence of impurities in it as it is being produced. This could save a lot of time and money for future space missions."

Pourpoint, who serves as the principal investigator for Aerospace Propulsion and Energy Conversion Systems at Purdue, is an associate fellow with AIAA.

"It's really nice to be recognized by peers in this venue," he said.