The Pitch Drive is a space drive that somehow induces a localized slope in scalar potential across the vehicle and eliminates the need to use a pair of point sources, in contrast to the Diametric Drive, possibly by employing a disjoint field to eliminate the need for the field to be directly generated aboard the vehicle. Possible implementations of the Pitch Drive include the Bias Drive and some Disjunction Drives.
Because some implementations require disjoint fields, the Pitch Drive is currently thought to be impossible for the same reasons as the simpler Disjunction Drive.
An illustration of the space-time distortion generated by a pitch drive can be found at http://www.geosoc.org/schools/adult/docs/Image25.gif
Information on space drives: http://www.grc.nasa.gov/WWW/PAO/html/warp/ideachev.htm