The two models competing in the stealth motorcycle program of the U.S. Defense Advanced Research Projects Agency (DARPA) feature electric engines as quiet as a normal human conversation.  The engines can also be used to recharge mobile devices such as radios and battlefield laptops.

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Competing head-to-head for the lucrative contract to build the U.S. Army's stealth bike are SilentHawk by Logos Technologies based in Virginia and Nightmare from LSA Autonomy out of Maryland. DARPA funded both bikes to phase two development that saw the building of the prototypes.

Both bikes are powered by two engines: a hybrid multi-fuel engine and an electric engine. The hybrid engine runs on a wide variety of fuels such as ordinary gasoline, diesel, Jet A-01 and JP-8.  A lithium-ion electric battery powers the bike in its stealth mode and keeps engine noise down to 55 decibels, the sound of a normal human conversation. A quiet whisper is about 30 dB.

The Army intends to use the winning prototype on raids to be launched by U.S. Special Forces units.

SilentHawk is an upgraded RedShift MX dirt bike, which is an electric racing bike developed by Atla Motors in California. It uses the RedShift MX chassis and a special hybrid engine developed by Logos.

Both bikes feature a front-wheel motor and rear motor. Nightmare, however, runs on a larger horsepower: 17 in front and 135 in back. The Nightmare averages around 13 kilowatts in generated power against 7.5 kilowatts for the Silent Hawk, making them suitable for charging radios and other mobile devices.

TagsDefense Advanced Research Projects Agency, DARPA, SilentHawk, Logos Technologies, nightmare, LSA Autonomy, stealth motorcycle