# Transfer orbits for dummies! A hillbilly tutorial.

by Jenab
Tags: dummies, hillbilly, orbits, transfer, tutorial
 Sci Advisor P: 1,182 Ah, the good old days of science fiction, when any scientist worth his salt could design an interplanetary spacecraft, and build it in his basement or back yard.
 P: 5 I thought that this thread had been closed. Oh well. 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
 P: 11 My LiveJournal article on how to calculate a hyperbolic transfer orbit is now published! Improved procedure for Elliptical Transfer Orbits http://jenab6.livejournal.com/12053.html Improved procedure for Hyperbolic Transfer Orbits (NEW!) http://jenab6.livejournal.com/15054.html Jerry Abbott
 P: 4 Question... what math level, in general, is this all working with? Hah... I feel so empowered, with all this knowledge and all, but I don't understand half the calculations in this thread.
 P: 768 Hi Jerry Like you I wanted to learn Astrodynamics after reading Heinlein since his figuring always seemed so precise. He wasn't always accurate though since he had to work hard with a slide-rule back in the pre-Calculator days of SF, but usually he was right. One orbit I've never been able to figure out is how the "Mayflower" in "Farmer in the Sky" could fly on a hyperbolic orbit to Jupiter and be high enough over the ecliptic plane to avoid the Asteroid Belt. Any thoughts? In that same book he mentions the Ganymede Colony was slowly built up via a fleet of small ships flying 1,000 day orbits out to Jupiter... back in the day when we didn't know how bad cosmic ray damage could be and knew nothing of solar flares.
 P: 91 Heinlein is my personal hero. I am a writer and I am on my first book, I am emulating him by learning my physics. Regrettably my book is almost done so I have to get some friends to help me finish up my equations lol. And BTW I resent the term "Hillbilly" especially when refering to it as an insult on intelligence. I have news for everyone, country people really aren't as portrayed on TV, believe it or not we have colleges, dentists, and we don't wear coveralls or straw hats. If you guys ever make it to NASA, AMES, or anywhere where the best and brightest are assembled you will find a hillbilly among them.
P: 11
 Quote by Nietsnie314 Question... what math level, in general, is this all working with? Hah... I feel so empowered, with all this knowledge and all, but I don't understand half the calculations in this thread.
Algebra, trigonometry, vectors, and occasionally a little bit of calculus. The ease of doing the calculations, or in finding out which calculations are right to do, is as much dependent on being able to visualize the goings-on as it is understanding the math.
P: 11
 Quote by qraal Hi Jerry Like you I wanted to learn Astrodynamics after reading Heinlein since his figuring always seemed so precise. He wasn't always accurate though since he had to work hard with a slide-rule back in the pre-Calculator days of SF, but usually he was right. One orbit I've never been able to figure out is how the "Mayflower" in "Farmer in the Sky" could fly on a hyperbolic orbit to Jupiter and be high enough over the ecliptic plane to avoid the Asteroid Belt. Any thoughts? In that same book he mentions the Ganymede Colony was slowly built up via a fleet of small ships flying 1,000 day orbits out to Jupiter... back in the day when we didn't know how bad cosmic ray damage could be and knew nothing of solar flares.
If a spaceship first enters an orbit that takes it above or below the ecliptic, it can then do a course adjustment that makes the departure point (or trajectory adjustment point) the perihelion of a hyperbolic transfer orbit to Jupiter that avoids the ecliptic until arrival. It just can't begin in the ecliptic with a hyperbolic transfer orbit and reach Jupiter, avoiding the ecliptic along the way. So a course correction would be required. But I think Heinlein probably suffered a lapse of thinking that time.
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 Quote by emc2cracker Heinlein is my personal hero. I am a writer and I am on my first book, I am emulating him by learning my physics. Regrettably my book is almost done so I have to get some friends to help me finish up my equations lol. And BTW I resent the term "Hillbilly" especially when refering to it as an insult on intelligence. I have news for everyone, country people really aren't as portrayed on TV, believe it or not we have colleges, dentists, and we don't wear coveralls or straw hats. If you guys ever make it to NASA, AMES, or anywhere where the best and brightest are assembled you will find a hillbilly among them.
Right. The reason I used the term hillbilly was to make that very point. I'm a hillbilly living in the West Virginia Allegheny Mountains. I'm a celestial mechanic. I have been employed as a defense contractor physicist. My last job, before I retired, was book editor for a small publishing company run by another hillbilly, who happened to be a retired physics professor.

I prefer an Adams cotton denim fishing hat with a 2.5 inch wide brim. I do sometimes wear overalls, but more often it's blue jeans and a blue denim cotton or tencel button shirt, with Merrell Primo Moc shoes. In the summer, that is. In the winter, I'm usually wearing Woolrich wool hunting pants (with suspenders), a Brooks Brothers cashmere sweater, a Columbia Titanium Omnitech windbreaker, a Carhartt pullover acrylic facemask hat, Woolrich "Big Woolly" merino wool socks, and Montrail Torre boots.

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