271 DARPA Phoenix  Camera Boom   This boom was designed to deploy  and retract a camera (hundreds of cycles) in support of the DARPA  Phoenix program . This boom utilizes a thin carbon fiber HSC  laminate and was designed to be neutrally  stable (same strain energy in deployed and stowed configurations)  upon rolling. As a result, during  operations the spool passively rolls / coils  without requiring additional constraints . The boom geometry is  circular with a 2.5” (6.35- cm) diameter with roughly  a 300º included angle . The deployer volume is set so  that the boom geometry is near fully recovered prior to exiting the front of the box to maximize structural  efficiency . This system also ut ilizes  a preloaded friction drive- wheel to deploy and retract the boom as well  as radial roller supports to enable rigid boundary conditions of the deployed boom . Finally, thin copper wires  are embedded into the composite mat erial to allow for power and data transmission to a camera located at  the distal end . A slip -ring is  implemented into the spool to electrically connect the boom wires with the  deployer . This feature eliminated the need for a separate, pull -out wiring harness.  

DARPA Phoenix HIMast  Boom   This boom was designed as a deployable building block element  for re -configurable satellites, and provides   improved structural performance, power transmission and deployed stability/precision as compared with  the ‘DARPA Phoen ix Camera Boom ’. In addition, this system was designed to fit within the mechanical  envelope of  the ‘HISat ’, a low -cost, modular satellite architecture that allows for rapid reconfiguration and  on-orbit assembly  under development by NovaWurks  of Los Alamit os, California. The options for  reconfigurability and potential to use multiple ‘ HIMast ’ deployers in tandem led to the development of a  unique, non- circular cross sectional shape shown in Figure 2. This shape is also convenient as it enables   a flat surface to embed large copper wire traces to supply power at the distal end. This boom is  composed  of a combination of carbon and glass fiber materials to enable high strength, precision and thermal stability.  

Figure 2.  ‘HIMast ’ Slit-Tube Cross -section  

Perhaps one of the most challenging aspects of the ‘HIMast ’ design was the 20x20x10 cm mechanical  envelope availab le for the deployer mechanism . This coupled with the required structural performance of  the deployed boom  forced this design to have component -level proportions not typically seen in slit -tube  systems . For example,  a large spool  was required that  occupied roughly  1/3rd of the available volume which  was not fully compatible with the natural spooling diameter of the composite. As a result, a preload on spool  was required during retraction to ensure proper coiling. In addition, in order to ensure that the boom  deployed perpendicular to the box, the composite had to be back -bent as it came off of the large  spool .  This required additional focus on the laminate design to ensure high strain levels and robustness . Another  example of the high compactness of the syst em relates to the drivetrain design. Here the  ‘HISat ’  architecture ena bled external motor driving which eliminated the need for a dedicated motor . However this  created several subsequent requirements  such as the need to pass this mechanical power to adjace nt  ‘HISat ’ / ‘HIMast ’ boxes as well as the need to mechanically sequencing the systems . This led to a drivetrain   design consisting of multiple gears, chains and slip- clutches shown in Figure 3. Here the mechanical  input/output is shown as black wheels on the top and bottom while the elastic wheels interfacing the  composite are shown in orange . Further details on this system designed are available within the literature  [8,9].