From: Henry Spencer <henry@zoo.toronto.edu> Newsgroups: sci.space.science,sci.space.tech Subject: Re: Navigation and Charting Date: Tue, 23 Jul 1996 22:50:08 GMT In article <01bb7676$c53c4320$374004c7@nbn.com.nbn.com> "Jeffery T. White" <zellion@nbn.com> writes: >...What >systems are currently available for charting and navigation that are not >dependent on the Earth horizon relationships or distances from Earth? For >example coordinate systems? Are all of these "Sectors" and "Quadrant" >things you see on TV just that much sci-fi or is there some basis in any >real system? Are there any books or materials I could obtain? Any good astronomically-oriented orbital-dynamics book, for example Roy's "Orbital Motion", will talk at least briefly about galactic coordinate systems. (There is, alas, more than one.) The sectors and quadrants are basically fiction, but there is some reality behind them. -- ...the truly fundamental discoveries seldom | Henry Spencer occur where we have decided to look. --B. Forman | henry@zoo.toronto.edu

From: Henry Spencer <henry@zoo.toronto.edu> Newsgroups: sci.space.tech,sci.space.shuttle Subject: Re: SSTO numbers Date: Mon, 8 Apr 1996 16:59:22 GMT In article <4k11ju$6mj@access5.digex.net> mheney@access.digex.net (Michael K. Heney) writes: > Calculating drag losses... > Calculating gravity losses... > Inclination-related computations... > Altitude changes... > Plane changes... > >I know that this can be found in a good orbital mechanics textbook, but >I'm not an orbital mechanic... Inclination, altitude changes, and plane changes you can indeed find in an orbital mechanics textbook; I'd recommend Prussing&Conway's "Orbital Mechanics" for starters. Beware of simple one-line answers, because in real life the answers depend on assumptions. (For example, any formula for plane changes which uses a single burn is relevant only for small changes; there are better ways to do big ones.) Drag and gravity losses are harder, and you won't find them in orbital- mechanics books -- normally they are the output of complex computer programs. One good place to look for approximations is the Handbook of Astronautical Engineering (Koelle, ed.); try a good library. There is a disadvantage, alas, in that HAE's approximations tend to be charts (rather than formulas, which are easier to put on-line). -- Americans proved to be more bureaucratic | Henry Spencer than I ever thought. --Valery Ryumin, RKK Energia | henry@zoo.toronto.edu

Newsgroups: sci.space.shuttle From: Henry Spencer <henry@zoo.toronto.edu> Subject: Re: Trajectory Calculations: Need text book recommendation. Date: Mon, 14 Apr 1997 19:10:26 GMT In article <334d20fe.7101472@nntp.ix.netcom.com>, Christopher P. Winter <cpwinter@ix.netcom.com> wrote: >Do you have an opinion on Victor Szebehely's work? (He has about 6 >books out on the subject, IIRC.) Haven't seen his work, I'm afraid. Limitations of local libraries. :-( >Also, I just learned that you've made some book reviews available in >the past. Would you consider re-posting these? Let's see, here's what I posted a while back, slightly updated: A while back, I happened to have cause to read half a dozen books on orbital dynamics. (Don't ask, long and trivial story -- I'd been meaning to read them anyway so it didn't take much...) Herewith some reviews based on that... (Sorry, I don't have exact prices on hand, but I've tried to give a rough idea with "$", "$$$", etc.) I should note that these are all fairly technical books on a technical subject. To read them you need to be at least on speaking terms, and preferably comfortable with, both vectors and calculus. (There is just no way around this, really -- Newton *invented* calculus for orbital dynamics!) If you cringe at the sight of equations, these books are not for you. Also, a general comment: the books' material on numerical methods should be taken with a large grain of salt. That field has advanced a great deal recently, and most of these books are well behind the times. For example, most any discussion of "multistep" or "predictor-corrector" integration methods can safely be skipped -- today's Richardson methods are better than most predictor-corrector schemes, certainly better than any you'll find discussed in an introductory book (and far superior to Runge-Kutta methods for most orbital-dynamics work). For numerical stuff I recommend "Numerical Recipes", 2nd ed., Press et al, Cambridge U Press, ISBN 0-521-43064-X, $$$ but worth it. Orbital Mechanics; John E. Prussing & Bruce A. Conway; Oxford U Press 1993; ISBN 0-19-507834-9, $$. I bought this a year or two, more or less sight unseen, on speculation. When it came, I was disappointed: it was *thin*, only a couple of hundred pages, and the list of topics covered was not overly large. I put it aside for later reading. I grudgingly decided to look at it when I was reading the other books, and revised my opinion steeply upward. This book is *still* too thin. It badly needs to be twice the length so it can cover more topics. Within its limited scope, however, it does an excellent job on the basics. Even some of the things that look drab at first glance acquire more interest on closer inspection. It's up to date and well focused on spaceflight; for example, you'll find a fairly complete discussion of gravity assists. Even the notes on numerical methods are reasonably current. I recommend this as the first orbital- dynamics book for serious space cadets (those who don't plan to stop with one book). Its coverage is a bit limited for those who do want only one book, but at the moment I can't think of a better choice. Orbital Motion, 3rd ed.; A.E. Roy; Adam Hilger 1988; ISBN 0-85274-229-0 (softcover), $$. This used to be my first-book choice, and now I think I'd call it the recommended second book. This one isn't thin; although it's billed as a student text, like P&C, the author clearly has a rather more energetic type of student in mind. The coverage isn't encyclopedic but it's broad. This is the book I tend to use as a reference for everything but the really deep stuff. The one negative thing I have to say about this book is that it's a very *classical* orbital-dynamics book. The emphasis is on astronomy, not spaceflight. For example, rendezvous is barely mentioned, and although you are given the tools you need to figure out gravity assist, it's not actually discussed. On the other hand, there's a whole chapter on the evolution and stability of the solar system, and another on many-body star systems. This book is wonderful as a supplementary source but is not a good first book for a space cadet. Fundamentals of Astrodynamics; Roger R. Bate, Donald D. Mueller, Jerry E. White; Dover 1971; ISBN 0-486-60061-0 (softcover), $. This book is very widely known and it's cheap. It tends to be the first book people mention in this connection, especially in North America. I've never liked it, and finally I've figured out why. This book was written as a text for the USAF Academy a quarter of a century ago, and *that* is the root of its problems. It is completely restricted to things that the USAF Academy considered to be of immediate relevance in about 1970. You get the basics of orbits, okay, and the stuff on lunar trajectories is interesting (that was the heyday of Apollo, remember)... but other than that it falls flat. Close to *half the book* is spent on orbit determination, which to my mind is a specialist problem that deserves one short chapter in an introductory book -- if I want to know all the gory details, I'll read Escobal's book on it (see below). There's a whole chapter on ballistic-missile trajectories. And there's little on anything even slightly advanced: nothing on rendezvous, nothing on multi-body dynamics, one terse look at interplanetary trajectories, a minimal discussion of perturbations. I don't recommend this book; get P&C instead. Methods of Orbit Determination, updated edition; Pedro Ramon Escobal; Krieger 1976; ISBN 0-88275-319-3, $$$. This is *the* book on determining orbits from observations. Moreover, its early chapters are an introduction to orbital dynamics and related topics, rather terse but with unusually broad coverage (for example, it discusses how to determine when a satellite passes into the shadow of a planet, and how to determine rise and set times of a satellite orbiting a planet which is oblate rather than perfectly spherical). It's mildly useful in that regard, although I wouldn't recommend actually buying it unless you want the orbit-determination material. As I've mentioned above, in my opinion orbit determination is a specialist topic (and I would caution that it's one I'm not intimately familiar with). Nearly twenty years after this book's updating -- thirty after its first publication -- it is still considered the authority on the subject. Most good orbital-dynamics books will cover one or two methods; this book tries to cover *all* of them, and mostly succeeds. It could use another updating, as there are brief allusions to (and an added appendix on) a few topics that the original didn't cover. The comments on numerical methods could undoubtedly use updating, although the comparisons of the numerical aspects of the different methods should still be valid. But it's still the book to buy to learn about the subject. Methods of Astrodynamics; Pedro Ramon Escobal; John Wiley & Sons 1968; no ISBN; almost certainly out of print. This book is intended not as a stand-alone book, but as a followup to the orbital-dynamics material in Methods of Orbit Determination (see above). It skips the elementary material entirely, and goes straight into selected topics in optimization, interplanetary and lunar trajectories, and some related issues. A very interesting reference if you can find it, but don't buy it as an introductory book. An Introduction to the Mathematics and Methods of Astrodynamics; R.H. Battin; AIAA 1987; ISBN 0-930403-25-8. This book I've skimmed rather than read closely. (Once you read three or four of these books, you reach the point where you can just skim the table of contents looking for new topics, and rarely find any.) I'd say that this book is mostly of historical interest. There's not much here that isn't in the other books, and some of it seems rather dated, although the book does sometimes go into rather more mathematical depth than the others. The best parts are the prolog and epilog, which talk about Battin's involvement with missile guidance problems and the design of the Apollo on-board navigation system, and how crucial problems were solved. Find the book in your local technical library and read those bits. Orbital Mechanics; Chobotov (ed); AIAA 1991; ISBN 1-56347-007-1, $$$. Another book skimmed rather than read, because it's mostly redundant with the earlier ones. It goes into a little more depth on a number of topics, but only a little. More current than Battin. Might be worth considering as an alternative to Roy: less breadth, but more of a spaceflight slant. Somewhat expensive. There's a second edition now, which I haven't seen. Space Vehicle Design; Michael D. Griffin & James R. French; AIAA 1991; ISBN 0-930403-90-8, $$$. This is not strictly an orbital-dynamics book, but it is worth mention nevertheless. It's one of the two best books about spacecraft hardware, and has unusually broad and practical coverage. It's got a substantial and fairly good section on orbital dynamics, and might be just the thing if you're interested in the rest of the book as well. A bit expensive but well worth it. (The other really good hardware book is "Spacecraft Systems Engineering", Fortescue&Stark, 2nd ed., which goes much deeper into each area of hardware design, but has less coverage of broader pragmatic issues. For example, F&S2 spends 20-odd pages talking about design of spacecraft mechanisms -- things with moving parts -- while G&F say almost nothing about that... but G&F talks about nitty-gritty like how to transport spacecraft, and why air transport is not always the right choice. Both books are worth having.) That's it for my reading at the moment. Comments and additions welcome. -- Committees do harm merely by existing. | Henry Spencer -- Freeman Dyson | henry@zoo.toronto.edu

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