1 Challenges in Spacecraft Reflector Technologies – A Few Potential Applications of Smart Materials B. S. Munjal * Scientist / Engineer-SG / Head, Structures Systems Division * Space Applications Centre (SAC), Indian Space Research Organization Ahmedabad. 380015. INDIA Email: [email protected]1.1 Introduction Intelligent / Smart / Adaptive structures are the state-of-the-art technologies being used for a few ground & some space borne structures and structural systems. Although intelligent materials systems and structural concepts may be applied to the design and implementation of buildings, dams, bridges, pipelines and ground based vehicles but recent efforts have shown the possible applications in potential domains of advanced aircrafts, launch vehicles, spacecraft antennas and large space borne systems. Until now, this has remained as an area not fully explored although, as a matter of fact, it has lot of built–in future potential. Smart structural systems, a buzz word of today, have the tendency to get adapted to the new environment by changing their shapes and sizes respectively by using the concept of sensing, actuation and control almost, as smart as, human body having the reflex action using nerves, muscles and brain. Smart materials should be able to both sense and communicate with outside intelligence in order to meet functional requirements. In SAC, efforts are being made to develop Smart spacecraft reflectors and Light weight spacecraft reflectors for futuristic applications. 1.2 Advances in Space Domain Weight and power consumption are at premium in satellites, hence there is always a requirement of state-of-the-art light weight, high specific stiffness, high specific strength and low thermal expansion materials for spacecraft reflectors. Size of the component is also a major consideration in spacecraft,
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Challenges in Spacecraft Reflector Technologies –
A Few Potential Applications of Smart Materials
B. S. Munjal*
Scientist / Engineer-SG / Head, Structures Systems Division * Space Applications Centre (SAC), Indian Space Research Organization
Efforts are also being directed toward the development of "smart," or
responsive, materials. Representing another attempt to mimic certain
characteristics of living organisms, smart materials, with their built-in sensors
and actuators, would react to their external environment by bringing on a
desired response. This would be done by linking the mechanical, electrical, and
magnetic properties of these materials. For example, piezoelectric materials
generate an electrical current when they are bent; conversely, when an electrical
current is passed through these materials, they stiffen. This property can be
used to suppress vibration.
1.3 A new era
Certain materials possess a property by which they experience a dimensional
change when an electrical voltage is applied to them. Such materials are known
as piezoelectric because of the converse effect; that is, they generate electricity
when pressure is applied. Perhaps the best-known such material is Lead-
Zirconate-Titanate (PZT); in fact “PZT” is commonly used to refer to piezoelectric
materials in general, including those of other compositions.
When manufactured, a piezoelectric material has electric dipoles arranged in
random directions. The responses of these dipoles to an externally applied
electric field would tend to cancel one another, producing no gross change in
dimensions of the PZT specimen. In order to obtain a useful macroscopic
response, the dipoles are permanently aligned with one another through a
process called poling.
A piezoelectric material has a characteristic Curie temperature. When it is heated
above this temperature, the dipoles can change their orientation in the solid
phase material. In poling, the material is heated above its Curie temperature
and a strong electric field is applied. The direction of this field is the polarization
direction, and the dipoles shift into alignment with it. The material is then cooled
below its curie temperature while the poling field is maintained, with the result
that the alignment of the dipoles is permanently fixed. The material is then said
to be poled.
When the poled ceramic is maintained below its Curie temperature and is
subjected to a small electric field (compared to that used in poling), the dipoles
respond collectively to produce a macroscopic expansion along the poling axis
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and contraction perpendicular to it (or vice versa, depending on the sign of the
applied field).
The working temperature of the PZT is usually well below its Curie temperature.
If the material is heated above its Curie temperature when no electric field is
applied, the dipoles will revert to random orientations. Even at lower
temperatures, the application of too strong a field can cause the dipoles to shift
out of the preferred alignment established during poling.
1.5 Research Element
Presently, in space segment domain, all the spacecraft components including
antenna feed chain components, mounting brackets for satellite reflectors, mast
mounted long wave guides / plumb lines, spacecraft reflectors etc, are all opted
for frequency based designs, basically, with a view to decouple the fundamental
system level frequency of the spacecraft w.r.t the sub-system frequencies
respectively.
Adequate stiffness ( frequency > 50 Hz) is provided for all subsystems including
the flimsy composite spacecraft reflectors to cater to launch conditions. All
these sub-systems face severe during launch vibration loads (in plane 20 g and
30 g out of plane ) approx., depending upon the launch vehicle. They are also
subjected to post launch thermal loads coupled with milli g vibrations
generated due to movement of three axis gyros of the spacecraft, altitude
correction exercises and thermal load variations.
In order to handle the design challenges of the futuristic small size, high
precision ,radio frequency Satellite Communication reconfigurable antennas of
the space segment for the Indian space research programme in particular, the
need was felt for investigating the applications of smart materials to meet the
structural, mechanical and electrical design specifications in a practical and
feasible way; purely from the realistic applications point of view.
Efforts, have been envisaged in understanding tomorrow’s design challenges for
developing a high precision, thin, space qualified futuristic reflector for high
Radio Frequency signals (Q/V bands) with following desirable design
specifications :
Diameter of Spacecraft reconfigurable reflector, say less than 1.0m,
First Eigen frequency of ~ 50 Hz (pre-launch – stowed condition)
Preferable total mass of < 3 Kg
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In-orbit stability RMS < 30 μm
Pointing error < 0.01o
These futuristic mechanically active reflectors may also modify the radiation
pattern by actively changing the shape of the reflector when on-orbit thermal
distortions deform the reflector shape.
As per the above design specifications, the geometry of the high precision thin
reconfigurable shells can be something as shown in Fig 1.18 :
Fig 1.18 Basic layout of the high precision thin shell
References [1] Gregory Washington , Design, Modeling and Development of Precision Apertures ,
Intelligent Structures and Systems Laboratory , Ohio State University , Columbus , Ohio 43210-1107.
[2] Ganguli A , Jhawar S and Seshu P , Shape Control of Curved Beams using Piezoelectric Actuators , Proceedings of ISSS-SPIE 2002 , December 12-14,2002 , Indian Institute of Science , Bangalore , India, pp (247-254).
[3] Brij N Agrawal and Kirk E Treanor , Shape control of a beam using piezoelectric actuators , Smart Materials Structure 8 (1999) pages 729-740, Printed in the UK .
[4] Hwan-Sik Yoon and Gregory Washington , Piezoceramic actuated aperture antennae, Smart Structure 7 (1998) 537-542 , Printed in UK .
[5] V K Gupta, P Seshu and K Kurien I ssac , Finite Element and Experimental Invstigation of Piezoelectric Actuated Smart Shells, AIAA Journal , Vol. 42, No. 10, October , 2004 .pp (2112-2123).
[6] E J Breitbach, R, Lammering, J. Melcher, F Nitzsche, Smart structures research in Aerospace Engineering (Invited paper) 2nd European conference on smart structures and materials , Glasgow scotland , 12-14,1994, SPIE Vol. 2361 on Page 11-18.
[7] ATILA Software User’s Manual ver 5.2.2
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[8] Verification Manual For ATILA ver 5.2.2
[9] Fukashi Andoh, Gregory Washington , Hwan-Sik Yoon ,& Yadim Utkin , Efficient Shape Control of Distributed Reflectors with Discreet Piezoelectric Actautiors
[10] Su Huan Chen, Guo Feng Yao and Hua Dong Lian , A new piezoelectric shell element and its applications in static shape control , Structural Engineering and Mechanics , Vol. 12, No 5 (2001 ) 491-506 .
[11] R. Lammering, ‘Smart strcuture with shape memory Alloy actuators 2nd European conference on smart structures and materials, Glassgow scotland , 12-14, Oct 1994, SPIE Vol. 2361 page 90-93.
[12] D Allaei , Vibration and noise control in civil strucutres by smart design, 2nd European conference on smart structure and materials, Glasgow scotland 12-14, Oct 1994, SPIE Vol. 2361 page 198-201.
[13] WB , Wu Dynamic analysis of smart materials, 2nd European conference on smart structures and materials Glasgow scotland 12-14 Oct, 1994 , SPIE Vol. 2361 page 269-272.
[14] T W Duerig, K N Melton , D stockel, CM Wayman, ‘Engineering aspects of shape memory alloys, Butterworth - Heinemann Ltd., 1990.
[15] Tadakazu Katayama , Yoshihiko sugiyama , Satoshi Kawashima & Kohji Nishino, shape ,memory alloy wire actuated hinge mechanism for deploying segmented plates’, Reprinted fromBulletin of University of Osaka Prefecture series A- , vol 45 No.2, 1996 Page 119-124.
[16] Ysugiyama, T. Katayama & E-Kanki, stabilization of cantilevered - flexible structure by means of an internal flowing fluid, journal of fluids & structures (1996) 10, P. 653-661.
[17] Robert E Newnham smart, very smart and intelligent materials, MRS Bulletin/ April 1993.
[18] James S Sirkis, smart ,materials and structures research centre (SMSRC) , MRS Bulletin, April 1993.
[19] Intelligent network for science and technology MIMR 95, MATETOPIA, 21 (JAPAN) [20] Alaster McDonach, Peter T. Gardiner, RON 5 Mc Ewen, Brian culshaw , second
european conference on smart structures and materials held at the Glasgow Hilton Glasgow scotland, 12-14, Oct 1994, SPIE,P SPIE, proceedings series, volume 2361.
[21] K P Gowd Adaptive materials for aerospace Manufacturing Technologies, proceedings of the 13th national Convention of Aerospace Engineers , Edited by NK Naik , Kanchan Biswas, G C Popli , page 23-30.
[22] Jim Scragg, Development of Intelligent structures , Proc. ESA symp. Space applications of Advanced structural material Noordwijk (NL) 21-23 March 1990.
[23] Y Furuya and H Shimada , Shape memory Actuators for Robotic applications, Materials processing engineering Tohoku University, sendai, 980 Japan.
[24] B S Munjal, H V Trivedi and P V B A S Sarma, ‘Vibration Damping on Graphite and Kevlar Composites using Piezoceramic Powder coatings: A Review’, The Shock and Vibration Digest, Vol. 39, No. 1, January 2007,pp 3-18, SAGE publications.,UK.
[25] B S Munjal, H V Trivedi and P V B A S Sarma “Concept of Parabolic Reflectors made up of Composites with thin hybrid PZT coated layers”, JIMSS (An international Journal of Intelligent Material Systems & Structures) ,Vol.19,Nov.11,pp 1281-1294(2008)DOI 10.1177/1045/39X07085515, SAGE Publications, UK
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[26] B S Munjal, A C Mathur, S B sharma, D subramanyam, ‘Development Efforts w.r.t. Mechanically Active Antenna Reflector using PZT Patches for IC-EC Coverage- A Novel Futuristic Concept’, Proceedings of the 59th International Astronautical Congress, IAC-08-B2.1.12,29TH September-3rd October 2008, Glasgow, Scotland, UK.
[27] B S Munjal, ‘Finite Element Analysis of Smart Skin Spacecraft Reflectors using Smart / Intelligent materials and Smart structural Systems’, PhD Thesis submitted to Gujarat University, Ahmedabad , India in April 2006.
[28] B S Munjal, H V Trivedi and P V B A S Sarma Parabolic Spacecraft
Reflectors -A Shape Deformation Investigation Using Discrete Unimorph PZT Actuators’, Journal of Structural Engineering Structural Engineering Research Centre, CSIR Campus , Taramani, vol. 34, No.5 December 2007-January 2008 pp.
[29] B S Munjal, H V Trivedi and P V B A S Sarma “Investigation of MLF for PZT powder coated Composite laminates using ASTM Standard”`,Journal of Spacecraft Technology, Thermal Systems Group, ISRO Satellite Centre, Vol.18, No.1 January 2008, ISSN 0971-1600, pp 48-60.
[30] B S Munjal, H V Trivedi and P V B A S Sarma ‘Piezo actuated Parabolic
Aluminum reflectors- A Shape deformation Investigation’, National conference on Smart structures and MEMS systems for Aerospace Applications, Research Centre Imarat (RCI), Vigyanakancha, Hyderabad. session 6, AB50, 1-2, December 2006.
[31] B S Munjal, H V Trivedi and P V B A S Sarma ‘An experimental
investigation of composite loss factor for CFRP/GFRP Laminates with smart material coatings at ambient temperature’, National conference on current trends in technology (NUCONE-2006) Nov 30- Dec 2,2006) pp49-53.
[32] B S Munjal, H V Trivedi, A C Mathur and P V B A S Sarma ‘Finite Element
& Experimental shape studies of parabolic antenna reflectors using discreet piezoelectric actuators’, session XIX (19th ) Mechanical Design of Antennas session , International Conference on Antennas Technology (ICAT-2005), Feb 23-24, 2005, Space Applications Centre, ISRO, Ahmedabad.
[33] B S Munjal, H V Trivedi and P V B A S Sarma ‘Graphite and Kevlar Composites with thin Piezoceramic Powder (SP4 & SP-5A) coatings using RF Plasma Etching Technique for vibration Damping benefits’, Plasma Processing Update, Golden Jubilee Issue, July 2006, pp 41-42.
[34] B S Munjal, H V Trivedi and P V B A S Sarma, ‘Surface Activation of Hydrophobic Graphite Composite Laminates by RF Plasma Etching for Piezoceramic Powder Coated Spacecraft reflector’, Proceedings of the CASST-2007 Symposium IISc Bangalore, Jan 18-20, 2006.
[35] B S Munjal, H V Trivedi ‘Shape Investigations of Parabolic Antenna Reflectors using Piezoelectric Actuators – FEA using ATILA ’, National conference on current trends in technology (NUCONE-2007) Nov 30- Dec 2,2007.