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%**********************    REFRENCES     *************************** 

\begin{thebibliography}{9.9}


\bibitem{med_thrust}
Borowski, S.K., ``The Rationale/Benefits of Nuclear Thermal
RocketPropulsion for NASA'a Lunar Space Transportation System,''
Proceedings of 27th Joint Propulsion Conference, {\em AIAA} Paper
91-2052, Jun 1991.

\bibitem{aviation}
Include the reference from aviation week.

\bibitem{nuclear}
Borowski, S.K., Clark, J.S., McIlwain, M.C., and Pelaccio, D.G., 
``Nuclear Thermal Rockets: Key to Moon-Mars Exploration,'' 
Aerospace America, July 1992, pp. 34-37.

\bibitem{electric}
Turchi, P.J., Curran, F.M., Andrews, J.C., Beattie, J.R., and Gilland, J., 
``Electric propulsion: The future is now,'' Aerospace America, July 1992, pp. 38-41, 49.

\bibitem{manned}
Nitta, Keiji, and Ohya, Haruhiko, ``Lunar base extension program and
closed loop life support,'' Acta Astronautica, Vol 23, Humans in Earth
orbit and planetary exploration missions, Pergamon press, Oct 1990,
pp. 253-262.

\bibitem{bryson}
Bryson, Arthur Earl Jr.,  and Ho, Yu-Chi, {\em Applied Optimal Control:
Optimization, Estimation and Control}, Hemisphere Publishing
Corporation, Washington, D.C., 1975.


\bibitem{lewis}
Lewis, Frank L., {\em Optimal Control}, John Wiley \& Sons, New York,
1986.

\bibitem{kleuver}
Kleuver, Craig Allan, ``Optimal and sub-optimal, low thrust, Earth-Moon
trajectories using Sequential Quadratic Programming,'' Thesis,
Iowa State University, Ames, 1990.

\bibitem{brazil}
Include the reference from Brazil.

\bibitem{katragadda} Katragadda, L. K.,``Genetic Algorithms and Nonlinear Programming for
Optimal Low-Thrust Spacecraft Trajectories'',Thesis, Parks Library, Iowa State University,
ISU, 1991, K 157.

\bibitem{moyer}
Moyer, Gardner H. and Pinkham, Gordon, ``Several trajectory
optimization techniques (Part II: Application),'' {\em
Computing Methods on Optimization Problems}, edited by Balakrishnan
and Neustadt, Academic Press, New York, 1964.

\bibitem{battin}
Battin, Richard H.,{\em An Introduction to the Mathematics and Methods
of Astrodynamics}, AIAA Education Series, New York, 1987.

\bibitem{ascher} Ascher,U., Christiansen,J. and Russell,R.D.,
 ``Colsys - A collocation code for boundary value problems,''
proceedings, {\em Conference for codes for bvp-s in ode-s}, Houston,
Texas, 1978.

\bibitem{holland} Holland, J. H., {\em Adaptation in Natural and
Artificial Systems}, The University of Michigan Press, Ann Arbor, 1975. 

\bibitem{dejong} De Jong, K.A., ``An analysis of the behavior of a
class of adaptive systems,'' Doctoral Dissertation, University of
Michigan, Ann Arbor, 1975. 

\bibitem{goldberg} Goldberg, D.E., {\em Genetic algorithms in Search,
Optimization and Machine Learning}, Addison-Wesley, Massachusetts, 1989.

\bibitem{lawerence} Davis, Lawerence, {\em Handbook of Genetic
Algorithms}, Van Nostrand Reinhold, New York, 1991.

\bibitem{ssrao} Rao, S.S., Pan, T.S., Venkayya, V.B., ``Optimal
placement of actuators in actively controlled structures using genetic
algorithms,'' AIAA Journal, Vol 29, Jun 1991, pp. 942-943.

\bibitem{hajela} Hajela, Prabhakar, ``Genetic search- An approach to
the Nonconvex Optimization problem,'' AIAA Journal, Vol 28, Jul 1991,
pp. 1205-1210.

\bibitem{krishnakumar} Krishnakumar, K. and Goldberg, David E., ``Control System Optimization
Using Genetic Algorithms,'' Journal of Guidance, Control, and Dynamics, Vol 15, No. 3, 1992,
pp. 735-740.

\bibitem{gear} Gear, W.C.,{\em Numerical initial value problems in
ordinary differential equations,} Prentice Hall, New Jersey, 1972.

\bibitem{fletcher} Fletcher, R., {\em Practical Methods in Optimization},
John Wiley \& Sons, New York, 1987.

\end{thebibliography}








