Re: I need some help with a research project

whclark2@xxxxxxxxxxx wrote: 
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.


There are relatively few places in engineering where getting the last
one percent is needed.  As I understand it there may be use for reducing
the friction on airplane wings by one percent, but not so many others.

As for celestial mechanics, there presumably is a curve describing the
minimum time for a given amount of fuel, or minimum fuel for a given
amount of time.  One must then make time/fuel cost tradeoffs to
determine which one actually is used.  Consider that there is a cost,
especially in added weight for food, of taking a longer time.
That cost is probably not known to better than 10% or maybe 20%.

I am not in the aerospace industry, but my feeling is that there
isn't any demand for better orbit calculations than currently
exist.

There is a story in the book "The Darwin Awards" about someone
who calculated the exact amount of water required to hike across
death valley.  It seems, though, that his calculation was off by
a few percent.  Most people would add 10 or 20 percent to their
water supply just to be safe.  There is, then, no need for a
calculation much better than that, and certainly not to
ten significant digits.  (A new meaning for down to the last drop.)

-- glen

.

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