# New and Improved: Elliptical Transfer Orbits determination procedure.

1. Jan 14, 2008

### Jenab2

I was "Jenab" who wrote the "Transfer Orbits for Dummies: A Hillbilly Tutorial" that was stickied in this forum. I've written an improved procedure. The main improvements are:

1. A more straightforward calculation of the true anomaly at the non-apsidal endpoint of the intended trajectory (i.e., either departure or arrival). In my previous paper on this subject, I missed the obvious fact that this angle can be found quite earlier in the procedure (and with much less rigmarole).

2. A more immediate solution for the calculated transit time, dt, which must be equal, or very nearly equal, to the required transit time t2-t1. This saves the user time, since he shouldn't bother with solving for the angular orbital elements if the hypothetical orbit isn't going to work out due to a mismatch in required and calculated transit times.

3. A consolidation of the four "cases" for calculating the eccentricity of the hypothetical transfer orbit into a single equation containing a sign toggle variable.

The time of departure, t1, and the time of arrival, t2, are selected by the user at the beginning. The required transit time may be found immediately, since it is simply their difference. The calculated transit time, on the other hand, is a function of the change in mean anomaly in the transfer orbit between departure and arrival, and the transfer orbit's mean motion.

Also of interest is the fact that I've found an asteroid that can be diverted into a collision with Earth with a departure delta-vee of only ~83 meters per second. The asteroid has the generic name of 2001-YB5, and I use it as my example in the new, improved procedure, which you can find at

http://jenab6.livejournal.com/12053.html

Jerry Abbott

Last edited by a moderator: Apr 23, 2017