Real-Time Fuel Chemistry Analysis for Hypersonic Propulsion System Ground T&E Using Ion Trap Mass Spectrometry

We propose a novel tandem mass spectrometry approach for in situ chemical analysis of neat fuels (1300 °F, 1200 psia) in scramjet heat exchangers (HEX).  This real-time method will reveal the (1) extent of cracking, (2) chemical composition, and (3) amount of each cracking product in the fuel.  We will perform tandem mass spectrometry using a linear ion trap (LIT) to distinguish between the thermal cracking products formed directly in the HEX and the electron-impact (EI) ionization fragments.  The technique will have high sensitivity (< 1% differences in abundance) and short analysis times (<100 ms per sample) and will be calibrated using NIST-traceable standards.  Using the LIT, we will eliminate the need for off-line chromatographic techniques (LC- or GC-MS) that are time-consuming and introduce sampling errors.  Furthermore, our method will have much greater specificity than low-resolution condensed-phase optical spectroscopy (e.g., FTIR, Raman, and UV/Vis).  In Phase II, we will (1) construct a mass spectrometer for use as an integrated system component at AEDC, (2) quantify cracking products in a HEX simulator, and (3) develop compact electronics for commercial use.  We will work collaboratively with AEDC towards future experimentation that leads to the rational design of endothermic fuels for hypersonic flight.