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Basics of Space Flight: Orbital Mechanics

236 点作者 dodders超过 9 年前

15 条评论

antognini超过 9 年前
We are actually very fortunate that the Earth is not very spherical, because without that satellites on the high inclination orbits like the polar orbits and the Molinya orbits would crash into the Earth.<p>Due to perturbations of the Moon, high inclination orbits have a tendency to be pushed from low eccentricity to very high eccentricity. (This is known as the Kozai-Lidov mechanism.) However, the fact that the Earth&#x27;s gravitational potential is not exactly spherical (it has a quadrupole moment) makes these orbits precess, and this precession happens to be fast enough to suppress the eccentricity oscillations.<p>There is a very good and very readable article by Scott Tremaine on this subject here: <a href="http:&#x2F;&#x2F;arxiv.org&#x2F;abs&#x2F;1309.5244" rel="nofollow">http:&#x2F;&#x2F;arxiv.org&#x2F;abs&#x2F;1309.5244</a>
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exDM69超过 9 年前
This page is mostly a digest of the book &quot;Fundamentals of Astrodynamics&quot; by Bate, Mueller and White (known as the &quot;BMW&quot; after the authors). This page is useful as a reference but not really good for learning material. I find the Wikipedia pages on this subject a bit shallow too (one of these days I&#x27;ll contribute improvements to the Wikipedia pages), so if you intend to learn this stuff, obtaining a book is the only viable option (if you know of other good online resources, please share with us. I don&#x27;t). The 1st edition BMW book from 1971 is available for dirt cheap (15-20 USD), the 2nd edition came out just a month ago but it&#x27;s poorly available (I&#x27;m still waiting for my copy from Amazon).<p>There&#x27;s a few more pages (incl. interplanetary mission planning) if you go up one level: <a href="http:&#x2F;&#x2F;www.braeunig.us&#x2F;space&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.braeunig.us&#x2F;space&#x2F;</a><p>Finally, here&#x27;s a project of mine that implements a bunch of algorithms for two body orbital mechanics: <a href="https:&#x2F;&#x2F;github.com&#x2F;rikusalminen&#x2F;twobody" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;rikusalminen&#x2F;twobody</a><p>These algorithms are mostly based on the BMW book as well as a bunch of research papers from the 1960s to 1990s. Look around in different branches for some of the more advanced algorithms (including a search for closest approaches and sphere of influence transitions like Kerbal Space Program and a boundary value problem solver for interplanetary travel), they&#x27;re still work in progress.<p>One day I&#x27;ll turn this into a mission planner software for space simulator games (or some kind of game, not sure yet). If you happen to need some orbital mechanics algorithms, take a look of the above and I&#x27;m happy to answer any questions or help with this.
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dvh超过 9 年前
Couple months ago I started working on space shooter&#x2F;simulator, just for fun. Newtonian physics, html canvas. It had 2D top view (F2 key) and 3D view (F3 key), but because canvas is quite slow on fullscreen I usualy switched rendering off (F1 key) and then I spent most of the debuging time there. I only needed few data to be displayed so I only rendered speed, distance fuel etc. as numbers. Then I added yaw pitch roll indicator and even though it was on canvas, because only small part was changing it was kinda fast, so I started adding more and more avionics and eventually the instrument flight [1] aspect of it become much more interesting that realistic planet renderings and I completely neglected 3D view [2]. The most fun so far was programing docking autopilot. So if you haven&#x27;t make your own space simulator, you should, it&#x27;s fun. (unfortunately it&#x27;s not finished and not even in publishable state)<p>[1] <a href="https:&#x2F;&#x2F;drive.google.com&#x2F;file&#x2F;d&#x2F;0B5SCh06PKpVtZHowN1l0TEw3cGs&#x2F;view" rel="nofollow">https:&#x2F;&#x2F;drive.google.com&#x2F;file&#x2F;d&#x2F;0B5SCh06PKpVtZHowN1l0TEw3cGs...</a><p>[2] <a href="https:&#x2F;&#x2F;drive.google.com&#x2F;file&#x2F;d&#x2F;0B5SCh06PKpVtUzMxSGNhRy1vVlE&#x2F;view" rel="nofollow">https:&#x2F;&#x2F;drive.google.com&#x2F;file&#x2F;d&#x2F;0B5SCh06PKpVtUzMxSGNhRy1vVlE...</a>
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runholm超过 9 年前
I can either read this for an hour, or play Kerbal Space Program for 50 hours and learn most of it. Pft, easy choice.<p>(I will then read the article and realize what I was doing wrong the whole time.)
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VLM超过 9 年前
I flew Orbiter to Mars from earth, docked with the ISS, also made a game of trying to visit each of Jupiter&#x27;s satellites about 10-15 years ago<p><a href="http:&#x2F;&#x2F;orbit.medphys.ucl.ac.uk&#x2F;" rel="nofollow">http:&#x2F;&#x2F;orbit.medphys.ucl.ac.uk&#x2F;</a><p>Its interesting to look at the MFD design for mission planning as an applied version of the linked page.<p>I have not played much KSP, is there anything as realistic as orbiter? From what little I&#x27;ve seen it tended toward comical set of pants, like comparing ChopperLifter to MS flight sim.<p>Orbital docking dynamics are weird. If you undock from the ISS and thrust up a little bit, in half an orbit you&#x27;ll come right back. Increasing or reducing your speed along the orbit (moving front or back) will eventually affect your altitude. Docking isn&#x27;t as simple as &quot;if you wanna go forward, thrust forward&quot;. All the control mix; like hovering a helicopter but slower. Flying &quot;in formation&quot; can be very expensive in terms of fuel depending on the formation, or it can be free if in a favorable geometry. There is a classic very hard sci fi story along the lines of extorting someone who doesn&#x27;t know orbital mechanics by literally throwing them off a space station, and the victim panics not knowing he&#x27;ll be back in half an orbit seeing as escape velocity is a little faster than a human shove!<p>One amusing anecdote is for an inclination change greater than 60 degrees or so, its cheaper to land and take off again or go on a very high orbit into deep space and change your inclination there. The ISS is at a very high inclination and at least energetically, to put the thing into a GTO around inclination 0 or so, it would be cheaper to land and re-launch the thing.
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jcadam超过 9 年前
I remember getting a basic primer on this stuff when I attended a USAF Space Operations course back when I was in the Army Reserve.<p>Our textbook (and an excellent book for the layperson interested in this sort of thing) was Understanding Space [1]. It&#x27;s still sitting on my bookshelf at work and I occasionally have a reason to crack it open.<p>As a software engineer in the aerospace industry, I was once working on a project to create a simulator for a new satellite program. I got stuck with writing a simulation model for the Attitude Determination and Control system (rather than something non-physics-y like the communications system). A lot of my job involved taking matlab scripts from the scientists and translating them into Ada code. An understanding of the basics of orbital mechanics came in very handy, as otherwise I would really not have had any way of knowing if my model was generating nonsensical output. Not to mention the onus was always on <i>me</i> to prove to a scientist that there was a bug in his algorithm.<p>[1] <a href="http:&#x2F;&#x2F;www.amazon.com&#x2F;Understanding-Space-Introduction-Astronautics-Technology&#x2F;dp&#x2F;0073407755&#x2F;ref=sr_1_1?ie=UTF8&amp;qid=1444234742&amp;sr=8-1&amp;keywords=Understanding+Space" rel="nofollow">http:&#x2F;&#x2F;www.amazon.com&#x2F;Understanding-Space-Introduction-Astro...</a>
yoha超过 9 年前
In case it might be of some use to anyone, I started a guide for beginners on the subject: <a href="https:&#x2F;&#x2F;airsick.guide&#x2F;" rel="nofollow">https:&#x2F;&#x2F;airsick.guide&#x2F;</a> . For Python fans (or anyone with a computer, really), there is also a (very simple) library designed with KSP in mind: <a href="https:&#x2F;&#x2F;github.com&#x2F;qsantos&#x2F;spyce" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;qsantos&#x2F;spyce</a>.
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ghaff超过 9 年前
Another classic book in the field is An Introduction to the Mathematics and Methods of Astrodynamics by Richard Battin of Draper Labs who passed away fairly recently. He developed and led the design of the guidance, navigation, and control systems for the Apollo flights at Draper. <a href="https:&#x2F;&#x2F;www.bostonglobe.com&#x2F;metro&#x2F;2014&#x2F;02&#x2F;23&#x2F;richard-battin-developed-and-led-design-guidance-navigation-and-control-systems-for-apollo-flights&#x2F;vxP9iIEfKuKpR7eCfes4fO&#x2F;story.html" rel="nofollow">https:&#x2F;&#x2F;www.bostonglobe.com&#x2F;metro&#x2F;2014&#x2F;02&#x2F;23&#x2F;richard-battin-...</a>
Gladdyu超过 9 年前
Great! A manual to Kerbal Space Program.
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unchocked超过 9 年前
There&#x27;s another interesting approach to orbital mechanics using geometric algebra. Paper below is from 1983, has anyone come across a later application?<p><a href="http:&#x2F;&#x2F;adsabs.harvard.edu&#x2F;full&#x2F;1983CeMec..30..151H" rel="nofollow">http:&#x2F;&#x2F;adsabs.harvard.edu&#x2F;full&#x2F;1983CeMec..30..151H</a>
brennankreiman超过 9 年前
Mike Bostock&#x27;s D3 can do some interesting visualizations based on satellite.js<p><a href="http:&#x2F;&#x2F;bl.ocks.org&#x2F;syntagmatic&#x2F;6c149c08fc9cde682635" rel="nofollow">http:&#x2F;&#x2F;bl.ocks.org&#x2F;syntagmatic&#x2F;6c149c08fc9cde682635</a>
ececconi超过 9 年前
The book Fundamentals of Astrodynamics&quot; by Bate, Mueller and White, where it seems like these notes come from was my Orbital Mechanics textbook in college.<p>Our final project was to program a crude missile defense system. Great book. It&#x27;s an old one, but I highly recommend it. It&#x27;s one of the few textbooks I saved from college.
Cheyana超过 9 年前
While getting ready for work this morning I was thinking about this very thing while I was brushing my teeth. I was thinking it would be nice to learn what the actual orbits of all 8 planets are, relative to the sun, and here I get into work and this is posted.<p>Now granted, I just wanted to know just the orbits as this stuff is way over my head, but I guess it would be good to learn it.
swagopopotamus超过 9 年前
Nice reference. Maybe now more of the stuff I hear on the orbital mechanics podcast (<a href="http:&#x2F;&#x2F;www.theorbitalmechanics.com&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.theorbitalmechanics.com&#x2F;</a>) will make sense.
blkhawk超过 9 年前
its amazing for how many of the diagrams i think - &quot;heh i did that and sorta know how to wing that by hand in KSP&quot;.
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