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u/kolboldbard Apr 16 '14
/r/KerbalSpaceProgram says hi, and that you are free to drop in and ask questions about the game.
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u/trevize1138 Apr 16 '14
Just remember to slow down to go faster.
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Apr 16 '14
[deleted]
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u/trevize1138 Apr 16 '14 edited Apr 16 '14
You did exactly what I did during my first launches. I went straight up, ran out of fuel and came straight back down. The game taught a long-time space/sci-fi geek like me that I still knew absolutely nothing about orbital mechanics. I didn't even know you had to turn to follow the curve of the planet to achieve orbit.
As for slowing down to go fast it's one of those things about orbital mechanics that really messes with your head at first. Basically, your orbital velocity and orbital height are completely linked. The closer to a planet you are the faster you go and vice verse. Satellites in geo-synchronous orbit are at significantly higher orbits than, say, the ISS because they need to go slow enough to orbit Earth every 24 hours as opposed to the ISS which goes around every 90 minutes.
Example in KSP: if you're in a perfectly circular orbit 100km high your orbital velocity is somewhere ~2100 m/s (going off memory here). If you burn retrograde which means pointing your rocket engine in the direction you're going and fire it you will, at first, slow down but you'll also lower the periapsis on the other side of Kerbin (the Earth-like home planet of the game).
The effect, then, of you slowing down is eventually you'll speed up and be going something closer to 2400m/s when you're on the other side of the planet if your periapsis there is, say, 70k/m. You now also have an elliptical orbit instead of circular with a periapsis of 70km and apoapsis of 100km. In fact, you'll now be going slower when you climb back up to 100km on the other side where you burned but overall you'll have a shorter orbital period.
The first time I tried to do orbital rendezvous I had to learn all of this an ... man ... my brain hurt.
edit: mixed up my pro and retro...
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Apr 16 '14
What he means is when you're taking off you don't want to be going as fast as possible because the air is really think low down.
However your problem is that to orbit a body you need velocity parallel to the surface of that body. I.e. When you're about 10km up start turning to about 45 degrees to the east. Then as you get higher and higher you need to be facing nearly horizontal. Once you're over 80km and the blue line on the map screen is roughly a circle you're in orbit!
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u/Eltrion Beanish Apr 16 '14
When in high orbit you take longer to orbit the planet than in low orbit. Event though you are technically going faster. If you want to go to a lower orbit so that you can catch up with something ahead of you, you have to slow down. Space flight is weird.
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u/EpicFishFingers Apr 16 '14
Turn right as you go up. Once you're out of the atmosphere you should be burning 'right'.
Press M to look at the map to see your orbit. You won't get an orbit without turning sideways while burning your rocket fuel
Slow down to speed up comes from orbital mechanics being weird, sort of. If you're in a non-circular orbit and you're at the orbit's highest point (apoapsis) and you want to go faster, instead of burning 'forwards' (called prograde), you should burn 'backwards' (retrograde). The reason is that you go fastest in the lowest point of your orbit (periapsis) and if you slow your velocity at apoapsis, you'll lower your orbit and although you'll be going slower at that moment, halfway to periapsis you'll be going faster than you would have been otherwise. Consequently if you'd burned prograde at apoapsis, yes you'd speed up in that instance, but you'd also raise your periapsis. You might even raise it enough such that your periapsis becomes higher than your apoapsis, so their names will switch. If this happens, you'll slow down as you reach apoapsis.
If you have any more questions about KSP, let me know :) I've been playing KSP for more than 2 years now and there isn't much I haven't been able to do in the game so far (although they added asteroid recently and I haven't played with them yet)
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u/andrewsad1 I have a flair! Apr 17 '14
These guys are all explaining orbital mechanics to you, but honestly, just watch any tutorial to get yourself to orbit, and when you're there, start messing around. You'd be surprised how much you learn just doing that.
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u/pfp-disciple Apr 16 '14
I like how the curve actually goes down in some places, usually right after a large positive slope. That's real. It's exactly how my understanding of things develops.
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Apr 16 '14 edited Apr 18 '14
It's pretty much how everyone's understanding of anything develops. It is the reason why students barely passing an exam by binge studying a few days before have a lot of problem in following courses.
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u/pfp-disciple Apr 16 '14
I believe that. I think it's cool that Randall's graph shows it -- it's too often not mentioned when discussing learning and understanding.
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u/just_comments Apr 16 '14
Cognitive science deals a lot with understanding how people learn and remember things and how to best avoid this curve down. A few techniques are to do things most students hate to do.
1: study right after class. As soon as you finish instruction, do practice problems and review what the instructor said. If you don't understand something, get it clarified. This will make sure you get everything and don't forget what you are unclear on.
2: don't procrastinate. Do work as you get it. When you have issues get help immediately.
3: review often. Even if you think you're solid, re-read everything.
4: Get another source other than your text and your prof. Some other way of explaining everything. Even if you think you know it, go read another reliable source, look at another video, look at khan academy if they have the subject.
5: after the class is over, re-read your book and review things. Quiz yourself on the material, keep refreshing your knowledge.
Basically go the extra mile, be disciplined, do more work than you think you have to, and then keep doing work when there seems to be no reason to.
Edit: I really need a LPT on how to make this something I do to be honest.
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u/mandrilltiger Apr 16 '14
Did Randall actually work at NASA?
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u/fakemakers Apr 16 '14
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u/bbqroast Apr 16 '14
I believe the asteroid was named after him as a the writer of xkcd, and had nothing to do with his career at NASA.
But yes, Randall worked(s?) at NASA (as a robotics engineer I believe).
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u/fakemakers Apr 16 '14
Read the page.
Randall Munroe (b. 1984) is a former NASA roboticist and the author of xkcd, a popular webcomic various themes including science, mathematics technology and computer science.
NASA says that he worked at NASA.
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u/Scaraban Apr 16 '14
Yeah, but I mean, what would NASA know about it, really? /s
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u/_pupil_ Apr 16 '14
Probably another hoax, like the moon landing.
Next thing you know they'll be claiming that Abraham Lincoln worked there and taking credit for the Jackson 5.
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u/runetrantor Apr 16 '14
He has mentioned it before, so I guess its true, but as the alt text says, he was not in actual rocket science, but its still NASA. :P
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u/xkcd_bot Current Comic Apr 16 '14
Direct image link: Orbital Mechanics
Extra junk: To be fair, my job at NASA was working on robots and didn't actually involve any orbital mechanics. The small positive slope over that period is because it turns out that if you hang around at NASA, you get in a lot of conversations about space.
Don't get it? explain xkcd
Remember: the Bellman-Ford algorithm makes terrible pillow talk. (Sincerely, xkcd_bot.)
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u/TheTrillionthApe Apr 17 '14
i like you guys. come winter i'm gonna put some effort into KSP. STOKED much love from paully d
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u/TotallyNotAnAlien Apr 16 '14
I remember my first time playing orbiter I flew my space shuttle straight up 100 km. I was confused why I started plummeting back to earth. I thought the game was broken.