329 Refinement of a Low-Shock Separation System 

Chuck Lazansky* 

Abstract 

This paper discusses the design of Marman Clamp-band Separation Systems, and several lessons learned by SNC over 12 years and multiple programs. Historically, there have been enough failures associated with Marman band designs that practical design guidance is publicly available. Utilizing a shock-dissipating release device has allowed us to sidestep many of the typical challenges associated with Marman systems and helped create a highly robust design baseline that differs significantly from the traditional system.   An overview of the purpose, components, and function of a clamp-band system will be presented.  Common failure modes of this type of system will be discussed, and how these can be addressed. Early examples of successful SNC systems will be reviewed (NANOSAT, Orbital Express). Much of our early work on Clamp band systems and release devices was performed collaboratively with SAAB-Ericsson (now RUAG). The heritage design was refined recently to meet a challenging set of requirements for the EELV Secondary Payload Adaptor (ESPA Grande). By retaining the proven features of the design, we built an optimized sub-24 inch (61 cm) separation system with high stiffness, low-release shock, and a compact envelope.    Overview of Marman Clamp Separation Systems   A “Marman clamp” or “Marman ring” is a generic ring clamp used to join two cylinders butted together at the ends. “Marman Products” was the name of the company which first produced this type of clamp in the 1930s 1. The Marman clamp was a sensible choice for spacecraft separation in the 1960s, as spacecraft  stages are usually comprised of butted cylindrical structures of truss/beam construction covered with a skin. Separation of these structures normally entails severing the bolted connections. The advantage of the Marman clamp was to reduce the number of bolts to be severed for release, improving reliability.   The first Marman clamps were a flexible strap or band held around a series of circumferential V-wedges over the angled flanges of mated cylinders 2. Load was retained by tensioning the strap such that the  wedges could hold the ring flanges together with no gapping under the worst load case. A redundant release could be achieved by severing 1 or 2 (or more) bolts that hold the flexible band/strap in tension. This allows the V-wedges to move radially outward, freeing the mated flanges. Bolt cutters, pyrotechnic or frangible bolts are historically common choices for the release element. Release of these systems results in significant shock as the band strain energy (and pyrotechnic shock) is dissipated. Typically there are features to retract and “park” the band after release to prevent the band from interfering with release of the deployed payload. Marman Clamp separation systems (also known as “V-bands”) have been used successfully on many missions. A generic system is shown in Figure 1.  Other features typical of these systems include indication of positive spacecraft separation with switches  or continuity loops in electrical connectors, and kickoff springs sized and balanced to provide proper separation velocity and attitude. 

                                                               * Sierra Nevada Corporation Space Systems Group, Louisville CO 

Proceedings of the 41st Aerospace Mechanisms Symposium, Jet Propulsion Laboratory, May 16-18, 2012