Rocket Artillery Systems
(Source: TM 9-500, Data Sheets for Ordnance Type Materiel, September 1962)
Heating and Tie Down Unit, 762-mm Rocket, Truck-Mounted, M78 and M78A1
See below for general description (TM 9-500)

HEATING AND TIE DOWN UNIT, 762-MM ROCKET, TRUCK-MOUNTED: M78A1, is composed of the 762-mm rocket heating and tie down kit and the TRUCK, CARGO: 5-ton, 6 x 6, M55.

The kit consists of an engine-generator housing assembly containing a gasoline engine generator set X125, one front and one rear warhead saddle assembly, one front and one rear rocket motor saddle assembly, three container supports mounted in the truck, and five socket and support assemblies mounted on the right side of the truck. The unit is designed to transport the 762-mm rocket M31A1 or M31A1C from the ammunition supply point to the assembly and transport section either in containers or mounted on the saddles. During travel, the engine generator set M25 supplies alternating current for heating the 762-mm rocket electric blanket M2. It also supplies direct current for operating the Sandia tester and special warhead assembly.