- posted
17 years ago

I am trying to get some feedback from people in the aerospace industry

or engineering in general, to help get readmitted to the University of

Texas at Austin Aerospace Engineering Ph.D program. All you need to do

to help me is to answer the following short questionare and send your

comments to the University:

Consider the following facts:

(1) The minimum energy interplanetary trajectory is called a Hohmann

Transfer. This orbit is characterized by a specific total amount of

fuel used and the total time of flight. Those two parapeters alone

define the minimum trajectory between any two given planets.

(2) The Earth to Mars trajectory is an extremely difficult problem to

solve numerically and is usually solved by a genetic algorithm, which

generates many random trajectories; chooses the best solution; then

generates another family of trajectories; etc, until a solution is

found.

(3) Non linear problems are typically solved by using a third party

optimization routine to generate the best solution - i.e. in addition

to the genetic algorithm, which is itself operated by the optimization

routine with each trial.

Now consider if a computer optimization of the Earth to Mars trajectory

would be worthwile if:

(1) It finds a trajectory from Earth to Mars that uses 25% less fuel

than the Hohmann Transfer, arriving at Mars in the Hohmann Transfer

time of flight; OR arrives 30 days faster than a Hohmann Transfer using

the Hohmann Transfer amount of fuel. The routine itself has 24 degrees

of freedom, which are solved simultaneously.

(2) The computer program arrives at a solution without use of a genetic

algorithm (and is fully integrated from start to finish in a seamless

path; i.e. there are no tricks), is less than 1000 lines long, uses a

varuable step Runge Kutta 7/8 integrator and is accurate to at least 10

significant digits.

(3) The optimal solution of (1) is achieved without the use of a third

party optimization routine; although use of same would presumable

generate an even better solution.

Please state whether or not you believe this would be a good research

project and, if done to completion, would be adequate for a graduate

research project.

Send your answers to snipped-for-privacy@mail.utexas.edu which is Dr. Lee Smith, JP

the UT Austin Vice President for Legal Affairs.

Thanks very much!

WH Clark