AF01-140
Deployable Reflectors
TITLE: Processing of Tough, Fracture and Puncture Resistant Thin Films for Space
TECHNOLOGY AREAS: Materials / Processes
OBJECTIVE: Develop processing methods for polymeric thin films with improved tear resistance for deployable
optics applications.
DESCRIPTION: AFRL has demonstrated the feasibility of using reflective (i.e., metal coated) polymeric films as
parabolic reflectors for optical imaging telescopes in which the film is opposed by a clear polymer film and the
structure then inflated to a parabolic shape. While small high quality polymeric reflectors are available, AFRL studies
have shown that the use of mechanically isotropic films of uniform thickness intrinsically suffer from shape aberrations
which cannot be corrected with state-of-the-art adaptive optics. In addition, the thin film tear resistance is
unsatisfactory due to pin holes, scratches, and contaminants acting as fracture initiation sites, or tear resistance is poor
due to puncture during deployment of the toroidal structural components. The purpose of this SBIR topic is to develop
polymer processing and fabrication techniques for the production of very tough and puncture resistant, precision optical
quality thin films (10 - 100 microns +/- 1%) which are parabolic in shape and possess a relatively small focal number (f
# < 2), such that deployment will unfold the packaged film to yield the optically satisfactory shape. The films should
possess a uniformly glossy surface with surface roughness less than 0.5 micron. This effort should focus on the
processing of the tough reflector thin film using homopolymer and copolymer compositions as physical or chemical
blends, fabrication processes for neat or reinforced systems, and metallization techniques. Material selection should
consider stability in low earth orbit (atomic oxygen, ultraviolet, thermal cycling in eclipse), resistance to creasing
incurred on polymer film packaging, resistance to creep deformation and impact from micrometeorite episodes.
Consideration must also be given to the ability to scale the proposed processing and fabrication methods to large
diameters (D > 8 meters).
PHASE I: The contractor shall develop processing schemes for the parabolic reflector material which result in
improved tear resistance and fracture toughness in comparison to state-of-the-art polymeric materials. For the use of
novel polymeric materials, the characterization shall include, but not be limited to, basic physical properties of the
polymer, such as molecular weight determination and solution viscosity. Secondly, accepted test methods to determine
the performance of the material in low earth orbit shall be employed. Characterization of the thermal and thermal
analytical properties of any of the polymers proposed shall be conducted as well as profiling of the optical quality
surface for planarity and surface roughness. Third, accepted test methods shall be invoked which evaluate the tear
resistance, puncture resistance, and fracture toughness of thin films at low and high test velocities, similar in process to
the deployment of the reflector structural supports at varying rates. Characterization of the perfection of the reflector’s
parabolic shape shall be demonstrated on the prototype deployable parabolic reflector using precision optical test
methods and computational analysis. Products of this Phase I effort shall be data and a proof of concept deliverable
with a diameter between 10-25 cm.
PHASE II: Based on the results of Phase I research, the contractor should further develop the reflector processing
methods to be implemented for the production of a mirror with a diameter of greater than one meter. The process
model should be modified, as needed, to account for scale-up issues. The process should be altered, with guidance
from the process model and characterization results, to yield the desired precision. Products of this Phase II effort shall
be data and one deliverable with a diameter greater than one meter.
PHASE III DUAL USE APPLICATIONS: The processing of large, deployable, mirrors will have significant military
and commercial applications. These include: surveillance, communications, target designation, imaging through
clouds, space-based laser satellite characterization system, remote sensing, wind profiling, target illumination,
nighttime imaging, assessing soil conditions and vegetation types, camouflage detection, detection of cruise missiles,
ballistic missile defense, ground-based laser relay mirror and space-based counterforce.
REFERENCES:
1. a. J. R. Rotge, D. K. Marker, R. A. Carreras, and D. Duneman, poster presentation (paper F09) OSA 1998 Annual
Meeting, Baltimore, MD, October 4-9, 1998. b. D. K. Marker, J. R. Rotge, R. A. Carreras, C. H. Jenkins, J. M.
Wilkes, C. B. Hogge, and D. Duneman, “Optical evaluation of membrane mirrors with curvature,” Proc. SPIE – Int.
Soc. Opt. Eng. 1998, vol. 3430, p. 202-208.
c. J. R. Rotge, D. K. Marker, R. A. Carreras, J. M. Wilkes, and D. C.
Duneman, “Large optically flat membrane mirrors,” Proc. SPIE – Int. Soc. Opt. Eng. 1999, vol. 3760 p. 207-212.
2. A. G. Evans and F. A. Leckie The Processing and Mechanical Properties of High Temperature/High Performance
Composites. Book 1. Constituent Properties of Composites. DTIC AD-A266394; final report for Contract # N0001492-J-1808, 1993, 336p.
3. P. Schuler and R. Haghighat, “Space durable polymeric films: advanced materials for inflatable structures and
thermal control applications,” Int. SAMPE Symp. Exhib. 1999, vol. 44(I) p. 382-392.
4. E. M. Wooldridge, Proc. SPIE – Int. Soc. Opt. Eng. 1998, vol. 3427 p. 65-73.5. M. J. O’Neill and M. F. Piszczor,
“Inflatable lenses for space photovoltaic concentrator arrays,” IEEE Photovoltaic Spec. Conf. 1997, 26th p. 853-856
(Cat. No.97CB36026).
KEYWORDS: polymers, membranes, polymeric thin films, membrane mirrors, fracture toughness, parabolic films,
tear resistance