This information on the Lockheed Terrastar is from Fred W. Crismon's book:
U.S. Military Wheeled Vehicles
Published by Crestline Publishing Co. Inc. in 1983
One of the most fascinating vehicles found anywhere was the Lockheed Terrastar, which was built in numberous applicated, including the self-propelled artillery included in Chapter 17. The U.S. Army Land Warfare Laboraty commissioned the construction of this version in 1967, and was extensively involved in the subdwquent testing. The concept involved a major wheel mode and a minor wheel mode. When the vehicle moved on firm ground, only the eight wheels on the surface were used for driving. This was the minor wheel mode. When the Terrastarr went into muddy, marshy or swampy terrain, the major mode took over and the entire three-wheel assembly began to turn, essentially creating a 4x4, walking the vehicle through nearly impassable areas. A gear train was enclosed in the hosuing of the hub and spokes on the inside of the star assembly. Operation was by simple controls including steering levers and a conventional clush, brake and accelerator. Cross-country speeds were up to 20 miles per hour and the water speed exceeded four miles per hour with a full 1500 pund payload. Pivot steer was used in both water and ground operation. The wheels up in the top position could always be considered as working spares. Terrastar weighted 2500 punds, was 10 feet, 10 inches long, 80 inches wide, and 60 inches high with windshield. Angles of approach and departure weere 60 and 56 degrees respectively. An unidentified 50 to 60 horsepoewr engine was used. Although the Terrastar was very versatil3e and could literally climb stairs, none were purchased.