The IMpulsive Phase Rapid Energetic Solar Spectrometer (IMPRESS) is an NSF-funded 3U CubeSat in development via a collaboration between the University of Minnesota, Montana State University, the University of California, Santa Cruz, and the Southwest Research Institute. The mission’s primary goal is to measure subsecond spikes in solar flare hard X-ray flux. These spikes can aid in the study of particle acceleration in flares by correlating the spikes’ properties with the properties of particle acceleration mechanisms. The mission will also carry secondary goals: perform stereoscopic X-ray directivity measurements in conjunction with the STIX instrument onboard Solar Orbiter and to demonstrate a new, high dynamic range X-ray detector that is optimized for high count rates and fast time resolution. IMPRESS will be a full sun spectrometer producing high cadence time profiles and 4 second spectra in the 4-100 keV energy range. The detector will feature 4 CeBr3 crystals with SiPM readout and an Amptek X123 X-ray detector, allowing it to constrain both the thermal and nonthermal properties of solar flares, independently. IMPRESS is targeting an early 2023 launch.