Complex sentence: Therefore, for the DASS Engine to operate beyond the target 30 km and Mach 5 operating conditions, it will be modified to store onboard oxidizer to be used with a rocket motor in its flow path.
Split into simpler sentences: Therefore, for the DASS Engine to operate beyond the target 30 km and Mach 5 operating conditions, the design will be modified. At even higher altitudes, the DASS engine will need to store onboard oxidizer to be used with a rocket motor in its flow path.