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Segway HT

Inventor Dean Kamen demonstrates the Segway HT at the U.S. Department of Commerce on February 14, 2002.

The Segway HT is a self-balancing motorized scooter with two wheels on a single axle, invented by Dean Kamen. The name "Segway" is a homophone of "segue" (a transition); HT is an initialism for human transporter.

The scooter is designed to be used on sidewalks and other pedestrian areas, hence its footprint is not much bigger than that of a human being. The inspiration behind it came from the balancing technology of Kamen's innovative wheelchair, which can climb stairs, and prop itself up onto two wheels, to raise the user into a nearly-upright position.

The Segway HT has electric motors powered by batteries which can be charged from household current. It balances with the help of internal computers and gyroscopic sensors. (The gyroscopes do not affect the balance; they are merely used as sensors.) The motors rotate the wheels forwards or backwards as needed for balance or propulsion. The rider accelerates or decelerates by leaning forward or backwards in the direction she wishes to travel. Steering is controlled by a twist grip on the left handlebar.

The Segway HT's maximum speed is 12 mph (19 km/h). Maximum power is 2 horsepower (1500 watt).

Military applications

In December 2003, the Associated Press reported that The Pentagon had purchased several Segways, as part of a research program called Mobile Autonomous Robot Software, an attempt to develop more advanced military robots.


The Segway HT has been known by the names Ginger and IT in the past. There were various reports of a revolutionary invention, but no details were available until its unveiling on December 3, 2001.

As of September 2003 (when all Segways were voluntarily recalled), approximately 6000 of the devices have been sold.

The Segway HT resembles the motorized, gyroscopically stabilized unicycles in the science fiction short story by Robert A. Heinlein entitled "The Roads Must Roll".


An alternative power source currently being explored by Kamen's company is the use of a Stirling engine to power the Segway. Stirling engines use hot and cold in a phased rhythm to move a piston by gas expansion. Stirling engines could not "run themselves", as an external heat source must be provided somehow. Stirling engines do have zero angular momentum and reduced vibration and are thus well suited for two-wheeled vehicles.

A Segway with a Stirling engine might use the Peltier effect to provide the hot and cold zones a Stirling engine requires.

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