332 General Design considerations  Good design practices for any highly loaded system also apply to Clamp band systems:  Stress-Corrosion Cracking : These systems will be preloaded to the flight load, and remain  loaded, possibly for months, until launch and deployment. Stress corrosion cracking has caused  sudden failure in clamp band systems, so using materials with an A-rating for Stress-corrosion cracking is essential. Minimizing potential stress concentrations with controlled fillet radii, controlled thread roots, and rolled threads on loaded bolts is normal practice.   Minimizing Thermal Effects: Thermal strains can cause changes in band preload. Load drift  should be avoided by using materials with similar coefficients of thermal expansion for rings and  band, and shoes (to a lesser extent). Aluminum is a typical choice for rings. Shoes are typically titanium or CRES steel, and band is normally CRES steel. An all-aluminum design (with the exception of titanium in the more highly loaded shoes at the band ends) is preferred by SNC as will be discussed further.   Control of friction:  This is critical at moving interfaces, especially between shoes and band, and  shoes and rings in order to prevent lockup, equalize loading in band and prevent cold welding  between rings and shoes. Surface finish (roughness) and solid-film / dry-film lubricants (DFL) MoS 2 (µ ~ 0.1-0.15) and Dicronite® DL-5 (µ ~ 0.05) are commonly seen in clamp band systems.  With aluminum rings, chromate conversion coating followed by DFL provides µ ~0.1. One tradeoff is that reduced friction between the rings, and between shoes and ring lips increases the required band load, but improves release performance and reliability.  Release Device  Traditional Marman clamp systems have used explosive bolt technology to load and release the band. The obvious disadvantages of these for this application are high release shock and inability to test the flight unit. While these devices have been used with success in clamp band systems, they present a number of other design issues to be solved which can complicate the design.   Multiple release points on the band have been recommended with pyro-bolt technology:  2 release points  for systems up to 18 in (46 cm) and 3-4 for 60 in (152 cm) or greater 3. This is primarily to add redundancy  for release in the event of a pyro failure. Multiple release points also are recommended to allow more symmetric expansion of the band, to help it clear the rings. However, this approach increases chance for non-uniform loading of band/rings, and complicates release dynamics as multiple devices must operate simultaneously. More release points also increases the need for extraction features or added hardware to actively pull the band away from the rings such as springs and tethers. This adds parts and complication to the design, and increases system weight (more bolts, trunnions, tethers, springs). That weight may be better used to improve margins elsewhere in the system to improve stiffness (rings, band, etc.).  Inadvertent bending loads are common in Marman clamp systems and have been responsible for flight  failures (overload, stress corrosion, or concentration in roots or creep of explosive bolts). Some technical literature suggests that despite good trunnion design, the failure mode may be inherent in the perpendicularity tolerancing of bolt head and nut threads and seats. Previous failures in these areas have been addressed with the addition of spherical seats or other misalignment features, and use of greases at the bolt attachments.  4  Explosive bolts have other well-known drawbacks. Flight units cannot be tested. Margins are determined statistically, through lot testing. There are also safety concerns of unintended release. NASA design guidelines state that all debris from pyro-technic release should be contained – as in the case of exploding bolts, bolt cutters, etc.    During our early work with these systems, we developed a release device specifically for clamp band  separation. The Clamp Band Opening Device (CBOD) uses patented FASSN (Fast-Acting Shockless Separation Nut) technology to dissipate stored strain energy resulting in extremely low shock to