275 and complexity . To date, all of Roccor’s deployers contain at least two roller support planes, an aft set near  the root end of the formation region and a forward end where the boom exits the box . The roller support s  for each plane come in two types , a ‘surface’ roller that contacts the composite radially around the cross  section and ‘edge’ rollers that guide and preload the open/exposed section of the slit -tube. In Figure 7, two  ‘DARPA Phoenix HIMast  Boom ’ units are stacked in tandem with the distal end partially deployed. Here the  difference between surface and edge rollers can be clearly seen. Each boom contains a maximum of two  edge rollers, whil e a variable number of  surface rollers are placed where the support is needed on both the  inside and outside of the open cross section . For all of Roccor’s boom deployers , the surface rollers are  simplistic  Delrin wheels that passivel y roll against the composite surface to provide support and low  parasitic drag. In the case of the ‘NASA  Cube Sat Magnetometer  Boom ’ the small envelope does not allow  volume for these rollers  so the composite runs along a smooth, low -friction contoured material interface.  

                                Figure 7.  ‘DARPA Phoenix HIMast  Boom ’ Boundary Condition Restraints  

The edge rollers within the Roccor family have evolved significantly as a need for  deployers with high  precision and robustness has been realized . The early design implemented for the ‘DARPA Phoenix   Camera Boom’  deployer is shown on the left side of Figure 8. Here a b all-bearing pulley was used and  preloaded against the composite edge with a spring- plunger system . This design concept worked well  however it was challenging to tune the pitch of the wheel in order to align it  to the composite edge . Slight  misalignments caused the side of the pulley to rub against the composite causing damage and  unpredictable performance. Furthermore, during the course of the deployment, slight changes in this angle  occurred as the distal end moved away from the deployer box leading to degradation  to the composite  edge . The magnitude of the edge preload was also very limited in order to prevent composite edge  degradation due to the small contact area between the circular edge pulley and the linear laminate edge.  In addition, when the boom was subjected to lateral loads, the spring- plunger was in this load path which  was often times too compliant and reduced  the overall deployed performance.  

The most current edge roller design is shown on the right side of Figure 8. This image is from the ‘NASA  ARM  Boom ’ deployer  system  however this concept has been implemented into the ‘DARPA Phoenix  HIMast  Boom ’ and the ‘NASA CubeS at Magnetometer  Boom ’ deployers . Here  the composite slides  directly  against a flat, hardened steel  block  enabling a rigid line -contact  interface along a defined length of laminate  edge . In addition, two surface rollers are immedi ately adjacent to align and hold the edge in place. This  system is designed to maintain the contact position even as the boom edge angle changes during the boom  deploy ment . In addition, there is no  compliance within this system other than a set screw to establish the  initial edge preload during tuning (in higher TRL versions, any set -screw adjustors have been replaced with  shim adjustment) . Instead, the compliance within this interface is transferred into the composite laminate  itself and the surface rollers locations are strategic ally placed to preven t undesired strains and binding. It is  important to ensure that the boom edges are properly trimmed to ensure minimal variance – and hence  change in edge preload - during the deployment of the slit -tube. In addition, proper edge treatments to