This bill, titled the "BOOST for Engines Act," mandates that the Administrator of the National Aeronautics and Space Administration (NASA) continue a program to modernize federal rocket propulsion test infrastructure at its facilities. The primary goals of this modernization are to increase capabilities , enhance safety , support propulsion development and testing, and foster the improvement of both government and commercial space transportation and exploration. Projects funded under this program may include infrastructure for test stands, enhancements to facility capacity and flexibility, and other relevant initiatives. The Administrator is required to prioritize investments in projects that improve test and flight certification for large thrust-level engines and multi-engine integrated test capabilities. Furthermore, the bill ensures that underutilized test facilities remain available for commercial use on a reimbursable basis and that no modernization project adversely impacts existing government programs, such as the Space Launch System.