On May 19, 11:24 pm, Pat Flannery wrote:
kevin willoughby wrote:
If two of three versions agree, that doesn't mean those two are correct.

Though in this case you do get feedback by observing where exactly the
satellite's orbit ended up in reality versus what one or more programs
predicted.
Subtle problems in a program may not manifest themselves fully until
something in the program is pushed out to the edge of its abilities.*
Tell them to figure out the launch trajectory into a orbit with a apogee
of 500 miles and a perigee of 450 miles and most all of the programs
will probably give you almost the same exact answer.
Toss one with a apogee of 1,000,000 miles and a perigee of 50 miles at
them and have them figure in the influence of the gravity of the Moon
and Sun during each orbit, as well as air drag at the perigee and that's
influence on future orbits...and I'll bet different answers start to
emerge from different programs.

The physics of the scenario is pretty much known, and
programmable, to levels of accuracy depending on including
tinier and tinier factors being placed into the program.
Also, skirting the atmosphere has a degree of randomness
such as a Bell curve between error bars because the
atmosphere fluctuates unpredicatably, but that is why
course corrections are expected.

Even small things like a change in the mass of polar
ice will affect Ballistic trajectories, which I think is referred
to in mil-speak as CEP for ICBM's.

A famous NASA unprogrammed anomaly is this one,
http://en.wikipedia.org/wiki/Pioneer_anomaly
where s/c navigation is concerned, involving a high speed
hyperbolic orbit.
Regards
Ken S. Tucker