Performance Analysis of Nested Inlet for Sampling Stratospheric Aerosol (NISSA) on a NASA WB-57 High Altitude Aircraft during SABRE 2025 Test Flights

NAGARAJAN RADHAKRISHNAN, Charles Brock, Suresh Dhaniyala, Clarkson university

     Abstract Number: 500
     Working Group: Instrumentation and Methods

Abstract
The interaction of stratospheric aerosol particles with solar radiation critically determines Earth’s temperature and climate. Stratospheric particles are often a result of gas-phase nucleation, but increasingly, primary emissions from rocket activities are observed. The characteristics of these particles and their evolution with time is critical to modeling long-term climate change. Accurate characterization of stratospheric aerosol properties requires aircraft-based measurements with research-grade instruments. High-speed aircraft-based sampling at high altitudes presents persistent challenges due to the combination of flow compressibility and turbulence in the inlet flow. Our limited ability to numerically model flow under these extreme conditions limits our ability to use computational fluid dynamics (CFD) for aircraft sampling studies. Recently, we developed a Nested Inlet for Sampling Stratospheric Aerosol (NISSA) for accurate aerosol sampling over a broad size range of 10 nm to 10 µm.

NISSA features a nested two-stage inlet design to mitigate turbulence effects and enhance isokinetic sampling across a range of flight conditions. NISSA was deployed on NASA’s WB-57 aircraft and flown during the SABRE 2025 test campaign. The seven high-altitude research flights allowed in-situ flow characterization using a miniature hot-wire anemometer for turbulence quantification, while absolute and differential taps/pressure sensors at several locations in the inlet allowed for flow validation. A DPOPS instrument sampled from the inlet, and the aerosol size distribution and concentration measurements with this instrument was compared against a balloon experiment conducted in the same air mass. In this presentation, we will report details of the inlet design and our results of performance characteristics obtained from the field campaign.