Precision High-Strain  Composite Hinges for Deployable Space Telescopes  Mark Silver* and Michael Echter*  Abstract  Future large space-based telescopes will require precision mechanisms for deployment or alignment after  they reach orbit. This research effort seeks to develop deployable primary-mirror telescope technologies  that leverage recent advances in mirror phasing, actuation and deployable structure technologies. One way  to obtain a precise deployed position of the optical components is with structures incorporating precision  High-Strain Composite (HSC) hinges. This paper focuses on characterizing the deployment precision of  individual HSC hinges and of a support frame utilizing multiple HSC hinges. Measurements of certain  individual HSC hinges demonstrate position precision as low as 0.6 µm and angular precision as low as  6 µrad. A deployable frame concept produced axial precision of 0.2 µm, piston precision of 2.3 µm and  angular precision of 6.3 µrad. A few modifications to the frame test setup are proposed that may improve  the piston precision results.  Introduction  The size of space-based telescopes with monolithic primary mirrors is limited by allowable launch vehicle  sizes. In order to have larger primary mirrors for a given launch vehicle size, some sort of on-orbit  deployment or assembly is required. One example of a deployable primary mirror is the James Webb Space  Telescope (JWST) primary mirror.1 The JWST primary mirror is an assembly of mirror segments. Two wings  with multiple mirror segments fold back when stowed to allow it to fit within the launch shroud. Besides  JWST, many deployed or assembled primary mirror concepts for space-based telescopes have been  considered for some time. 2-9 The key performance requirement for deployed or assembled primary mirrors is positional accuracy. The  deployment precision is how close the deployed shape of the structure matches the original shape of the  structure before folding. Many factors can lead to positional errors in telescope structures, including  assembly error, deployment precision, and shape change due to environmental loads. The level of  positional accuracy needed is telescope-, wavelength- and mission-dependent but is generally about onetenth to one-twentieth of the wavelength of interest and may vary in different degrees-of-freedom. The  degrees-of-freedom used to describe deployment precision for the structures used in this paper are defined  in Figure 1. In this figure, two displacement degrees-of-freedom are defined, Axial and Piston, and to  rotational degrees-of-freedom are defined, Roll and Pitch.  *MIT Lincoln Laboratory, Lexington, MA DISTRIBUTION STATEMENT A. Approved for public release. Distribution is unlimited.  This material is based upon work supported by the Assistant Secretary of Defense for Research and Engineering  under Air Force Contract No. FA8721-05-C-0002 and/or FA8702-15-D-0001. Any opinions, findings, conclusions or  recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of  the Assistant Secretary of Defense for Research and Engineering.  Proceedings of the 44th Aerospace Mechanisms Symposium, NASA Glenn Research Center, May 16-18, 2018  NASA/CP—2018-219887 417