Rocket Motor Movers

A key element of NASA's Space Shuttle is the pair of solid rocket boosters (SRB) that provide more than two thirds of the required thrust to launch the Shuttle into space. Each SRB measures 149.16 feet long and 12.17 feet in diameter (45 x 3.7 m). The thrust is supplied by a modular Reusable Solid Rocket Motor (RSRM), that forms about two thirds of the length of a SRB. This rocket is believed to be the world's most powerful and is the first that is designed to be re-used.

ATK, a leading provider of advanced weapon and space systems, is the manufacturer of the RSRM. At its location in Promontory, Utah the segments are assembled and require moving on the plant and to the rail head in Corinne for transfer to rail for further transport to the Kennedy Space Centre in Florida.

When the solid rocket motor programme began in the 1970s, the company obtained a special vehicle that had been used to haul transformers to the bottom of Glen Canyon Dam. Now, some 45 years later, the time had come to replace that vehicle. ATK formed a Project Team that developed a list of requirements and that communicated with potential manufacturers of heavy and specialized transport equipment.

The concepts were evaluated by the team. Special emphasis was on safety, reliability and proven performance. In this respect the transporters being used in the shipbuilding industry formed the basis for the final design. The key ingredients consist of pendulum axles with hydraulic lift and steer and hydrostatic drive.

Out of a shortlist of three final manufacturers, Scheuerle, a member of the Transporter Industry International Group (TII), was selected to build the new RSRM Transporter. The team found the German manufacturer to have a proven track record in many heavy transport applications, including the ATK Transporter for the Titan Solid Rocket Motor.

After manufacturing the different parts and components of the transporter at Scheuerle's fabrication facilities in Hungary, Slovenia and Germany, it was fully assembled. The transporter consists of a six axle line front and rear unit. Each is self propelled and has a power pack on top of the transporter's deck. On top of that, and on both ends is an air conditioned cabin.

The engines have a combined output of 1,200 hp (894 kW). Top speed is 25 mph (40 km/h) but, when hauling RSRM segments, speed is restricted to 15 mph (24 km/h). A RSMR segment is loaded onto a platform that can be attached to a free-swing gooseneck, providing hydraulic lifting and lowering, on either transporter unit.

In this way the loaded transporter will be 124 feet (38 m) long. It is 14 feet wide and 17 feet high (4 x 5 m). Each transporter unit has a turning radius of 17 feet (5 m). Fully loaded the RSRM transporter brings 367 tons (333 tonnes) on to the road.

Safety and reliability were basic requirements for the new vehicle. Therefore, the transporter has some additional special measures:

■A spare diesel engine and hydraulic pump that can be lifted onto the vehicle to provide power if the vehicle engine or pump fails. Quick disconnect fittings are provided

■Hydraulic accumulators that store enough pressurized hydraulic fluid to maintain steering control in the event of an engine failure

■Critical hydraulic lines have redundant circuits and sensors that cut flow in case of a burst hose

■Goose neck lift system can still function with a failure in any one of the four hydraulic rams

■The vehicle suspension is divided into four zones allowing load position to be held if one zone fails

■Redundant hard wired and wireless communication andcontrol lines between the two vehicles and a fail safe braking system

■A camera system to give visual access to hard to see areas

■Cabins havestate-of-the-art communication systems

■Self-monitoring hydraulic system that checks flow rates for leaks and other problems in the lift cylinders and motors

■Four to one safety factor on load carrying parts. After Scheuerle completed assembly of the RSRM transporter it was put through a series of tests before being partially disassembled and shipped to the USA. After arrival in Corinne, Utah the transporter was reassembled and tested again before being put into full operation carrying RSRM segments on a daily basis.

■Fully loaded the RSRM transporter brings a total of 367 tons (333 tonnes) on to the road