The two bikes, the Logos Silent Hawk and the LSA Autonomy Nightmare (shown above), blend dramatic versatility with stealth characteristics. Their gas engines reportedly can run using either spark or compression ignition, meaning they can burn just about anything – gasoline, jet fuel, propane, you name it. Alex Dzwill, an engineer with Logos, told Defense One that it could even "theoretically" run on lipids, like olive oil. That's good news for special forces operating behind enemy lines, where supplies are low. Out of gas? Just raid the local shawarma joint.
But the bikes also have a stealthy hybrid powertrain. Flip a switch, and instead of an 80-decibel combustion engine, the bike switches over to an electric motor/lithium-ion battery that drops the noise level to just 55 dB. According to D1, that's about as loud as an indoor conversation. Aside from making the bikes quieter, the hybrid systems can also power communications equipment in a pinch. That's the kind of versatility the military loves.
But why bikes? They don't exactly offer a lot of protection in combat, after all. The idea, as Popular Science explains, is that the motorcycles won't necessarily enter combat – this is not a modern version of horse cavalry. Instead, they can be dropped in with special operators, who can use them to get to places quicker and quieter than traditional vehicles.
According to PS, DARPA's bike competition is midway through its three-phase development program. While the two bikes show a lot of promise, they aren't quite ready to hit enter service yet. Sorry, special operators.