Diesel cycle engine air independent systems having all of the following: (a) Chemical scrubber or absorber systems, specially designed to remove carbon dioxide, carbon monoxide and particulates from recirculated engine exhaust; (b) Systems specially designed to use a monoatomic gas; (c) Devices or enclosures, specially designed for underwater noise reduction in frequencies below 10 kHz, or special mounting devices for shock mitigation; and (d) Specially designed exhaust systems that do not exhaust continuously the products of combustion;