The Challenge

• The most critical element for focus & alignment on a Cassegrain telescope is the secondary mirror support tubes

• Composites dry out on-orbit for as long as 2 years which changes length of secondary mirror support tubes

• Long tubes with the smallest cross-section are required to reduce obscuration but must be very stiff to not drive system dynamically.

The Approach

•Boron with PITCH K13C2U tube has an axial Modulus of 55 Msi & a CTE of 0.0 +/- 0.06 ppm/0F*

•Boron increased the compression strength of the laminate by > 250%

•Extremely low CME & low moisture uptake resin resulted in very little change in length due to on orbit dry-out (less than 1 microinch per inch of tube length)*

*Based on US5593752A, low CTE/CME boron/carbon fiber laminates & method of making them, Pollata & Quinzi, status-expired 11/28/2015, https://patents.google.com/patent/US5593752A/en

The Result

• NASA Missions like WFIRST & JWST use Boron/K13C2U tubes for critical optical alignment
components

• Imaging Satellites used for Google Earth pictures use Boron/K13C2U tubes for
secondary mirror support tubes

•Boron increases compression strength of high modulus fiber by preventing microbuckling