Cranes for lifting and lowering heavy objects are an important and sometimes essential tool in modern industries such as construction, transportation, and manufacturing. NASA uses overhead and mobile cranes for assembly of load lines employed in full-scale testing of its Space Launch System (SLS), a super-heavy-lift launch vehicle for deep space human space exploration. Structural testing of the SLS requires precision placement of heavy objects with soft contact during mating connections, which proved to be problematic with the relatively coarse control available with motor-driven overhead cranes and the existing rigging devices.
In response, NASA Marshall designed the Soft Mate lifting device to incorporate an adjustable pneumatic soft spring into the lift rigging of a crane that can maintain a neutral load while connections are assembled or disassembled. Soft Mate is a below-the-hook tool that provides initial and gentle contact between mating connections while using a crane. The device utilizes a set of rolling lobe airbags to add a pneumatically adjustable soft spring into the lift rigging of a crane.
The current state of the art in precision placement of objects by cranes is a below-the-hook hydraulic system that does not add any elasticity in the lift rigging and requires the user to constantly adjust the hydraulic pressure to maintain a neutral force on objects being joined. By virtue of the pneumatic core, the Soft Mate lifting device provides the needed elasticity while minimizing necessary user interaction during lifting and placement.
Although designed particularly to aid in NASA’s SLS threaded load line assembly, the extra compliance provided by the Soft Mate system may also benefit other applications where additional control and precision are required for placing or mating heavy components. The design has undergone extensive stress analysis and is based on commercially available components that can be scaled and optimized for different weight requirements. The system provides the flexibility needed to assemble heavy components with threaded connections or other precision crane placement applications where greater compliance is needed.