Orbital Mechanics

Is basically the application of ballistics and celestial mechanics (separate post coming later) to practical problems, such as the motion of rockets or other spacecraft. Newton’s laws of motion and universal gravitation are used in calculation of these problems.

Main focus of orbital mechanics is spacecraft trajectories. There’s plenty of mathematical formulae for different situations, but for these purposes I’m just going to skip the maths (I’m really bad at math, so I’d just screw things up if I tried). You can find them online if you want to know. The practical applications of all the math are mostly orbital maneuvers, orbit plane changes and interplanetary transfers.

If two spacecraft want to dock in orbit the trailing craft cannot just fire its engines to go faster (because the trajectory will change). Multiple precisely calculated engine firings in multiple orbital periods may be required (may take anything from hours to days).

Basic transfer orbit is ellipticalAlso other options available (bi-elliptical, general).

There are a few basic points I’m going to put up here just so I have them on hand, as follows:

  • Kepler’s laws of planetary motion (abridged)
    • orbits are elliptical with the heavier body always at the center (think of the Earth and Moon) – circles are also a special case of ellipse!
    • the square of a satellite’s orbital period is proportional to the cube of it’s average distance from the planet (or sun or whatever one’s orbiting)
  • without applying force the period and shape of the satellite’s orbit won’t change
  • a satellite in a low orbit moves faster than one further out
  • if thrust is applied at only one pointin the satellite’s orbit it will return to that same point on each subsequent orbit, though the rest of it path will change
  • from a circular orbit, a thrust applied in a direction opposite to the satellite’s motion changes the orbit to an ellipse
    • it will then reach its lowest orbital point at 180 degrees away from the firing point
    • if thrust is applied towards the direction of motion, highest point is 180 degrees away

Nifty pictures may be edited in on a later date. No promises.


Reading journals

Several times over the years I’ve tried to write down thoughts about whatever it is I’ve been reading. That always ends up in a disaster, as at some point I just get very immersed and forget I was supposed to write about what I was reading.

Long time ago one of my teachers gave out an assignment to us to write a reading journal and then an essay about the book using the journal as basis. I read the book alright, but my notes took the entirety of five lines in my notebook and were pretty much useless in my essay.

“This book starts off mighty boring.”

While writing the sentence above it might feel like the most observant thing anyone has said about the literary work described. It’s really of no use, though.

Although the book might be boring as f***, there ought to be something more you can say about it. Off the top of my head at least a ‘why’-question might be necessary. Yeah, that never pops up when I’m actually doing one of these journals.

“Pace picks up at page X.”

So what happens then? Then you actually start getting engrossed in the book. This is usually the point when I stop writing for about 100 or so pages, just because … I’m actually reading the book.

This is usually the point where I totally forgot the point of the entire reading journal thingie. I mean, if you want to get kids to read, just give them an interesting book they’re likely to like and let them read it. If you want to make sure they don’t really enjoy it but also to make sure they’ve got proof they sorta read it, make them write a journal about it.

“I like how Y behaves about themselves.”

Don’t get me wrong, I’d really want to be able to write one of these analytical, witty reading journals that some of my classmates were able to write at 6th grade. I just can’t.

Just analyzing what I read can be a bit of a hassle sometimes. Honestly, more often than sometimes. Fiction is one of those things I just can’t make myself analyze in too much depth. In my weird inner world, works of fiction are made to be enjoyed (or loathed, like the Paul Auster books I had to read for my entrance exams one year while trying to apply into a university) as they are. They aren’t supposed to be thought about too much. Too much analyzing can destroy the image the writer wanted to portray by writing it just so.

Scientific literature is easier that way. What is written is supposed to make sense and stand up to peer review. If you can’t make sense of it, think of it a bit more, read the sentence again. If you still can’t figure it out, maybe it’s not your field or it really doesn’t make sense. Easy.

“I didn’t really understand this book.”

Yet another one of those sentences that really tells everything and nothing. Bit like that so called essay I wrote about that book. I guess I hid really well that my journal was a stub. The essay didn’t betray the fact, and thank goodness the teacher wasn’t interested in the actual journals.

One book I have to admit (to my immense shame) of falling into this category is Tuntematon sotilas (The Unknown Soldier) by Väinö Linna. Sure, I know what it is about, I know the general flow of the story (show me a Finn who doesn’t know the story at least through the movie and I’ll show you a liar) and I know the central characters. But there is this one spot towards the end of the book where I always get confused who was who and did what. I’ve read Tuntematon maybe five or six times over the years (three times for school) and that same spot always confuses me.

As a granddaughter of a war veteran this is especially embarrassing to admit…

So why do I care about them stupid journals?

I wanted to study language and literature in a university once. I gave up on that dream after I had tried and failed the entrance exams four times for two different universities. While I never got to know what exactly I could have done better for three of those, I know exactly why I failed the fourth one.

I told you earlier about the Auster books I loathed. In the exam I was to write an analysis of the books (The New York trilogy I believe it was). As I absolutely hated them, I of course said so in the essay. I believe that combined with my lack of skill in analysis got me to fail (along with the fact I don’t belong in a certain minority of Finland that is somewhat favored in said university). I never really learned to analyze anything during my Finnish classes in high school – I really didn’t (and still don’t, really) see the point and I wrote prettily enough to hide my lack of skill whenever we had a test on the subject.

After my first failed exams I pushed myself to study the subject twice more for the next time. During that studying it dawned to me I have no idea how to analyze literature. Reading has always been to me a thing of pleasure, and now I was supposed to figure out all those whys and hows. Needless to say that wasn’t taught in any book and I failed twice more. After that I gave up and figured university wasn’t a place for me after all. (Or maybe I should have listened to my English teacher, majored in English and gone to Bruxelles to work for the EU as a translator. Oh well, bygones.)

When I was done wallowing in self pity I thought it’d still be a useful skill to know if I really wanted to write a book (being modest is very me, but being modest about writing isn’t). If I wanted to be a successful writer I should know what really made a good book, right? That got me back to that old task of writing a reading journal. Except that I still didn’t know how I was supposed to do that either.

I get those moments of revelation (you know “Ohhh, I see what you did there, you sly fox you!”) from time to time, but if I intentionally try and read a book and understand why this part is in there or why we’re told about this thing Y, I usually just draw a blank and move on. Dwelling on a specific subject is something I’m definitely not good at, at least when I can think of nothing remotely relevant. You may have noticed something of the sort from my random ramblings…?

Anyway, having forgotten and rethought the point of this blog post for a few times now… Have you written reading journals? How’d you do? Teach me how to do it?

No, really, tell me how you do that.

Happy New Year and stuff

First off, Happy New Year to all and everyone.

My unofficial but very real holiday break is now over. Unofficial because I really didn’t say anything about it to anyone, and real because I spent both Christmas and New Year’s eve in places without internet connection.

(I also had no recollection how stressful and tiresome my line of work is during the holidays, even after 6 years on the job. If you think shopping before Christmas is bad, try working retail.)

First post for 2016 then! I don’t have anything really new to post – my parents made a point of not letting me bury myself in books over the Christmas weekend and my husband’s drunk friends aren’t really conductive for doing research either. I’m sure you know how someone pushing a beer can your way and insisting you go out for a smoke and shoot rockets is way more fun. At least until the next morning arrives.

So, I figured I’d write a word or two about Goodreads. I’m sure you’re all familiar with the site, but here are some of my thoughts on the matter.

Few months ago I finally got around to registering. I’ve no major beefs with the site, per se, just that when you’ve over 460 books and you’ve read maybe three times as many the managing of said literature turns out to be a bit of a hassle.

I downloaded the app for my tablet (I think it’s unofficial? Hasn’t been updated in ages…) and tried adding books while watching TV. Well, the app goes unresponsive after 4-6 searches. Don’t use it unless you really buy your books one at a time. Or if you only want to use it to see what you already have (that you’ve put up with something other than the app).

Unsurprisingly, there are no apps (at least any that seem trustworthy) for Windows phone. That really is not a surprise, but it would have been handy to have a list of your books wherever you go to. You know, because of all those inspiring conversations you have with people until you can’t remember the name or author of that one killer book. You never have that happen? Well, aren’t you the first person ever – or just equipped with way better memory than me (either way, I’m jelly).

But yeah. So I’ve been procrastinating adding my books (160/463~?) because when I add them on the tablet I have to go over them on my PC to make sure stuff is where it should be and making sure I’ve got the correct edition chosen out. Work in progress, at this pace never to finish.

Maybe someday I will have all my books up (even those I haven’t found in the database yet). Until then, if you’re interested, my shelf can be found over here.

If you happen to have any useful tips send them this way. Could really use some.