Nikolai

Prussing and Conway. Prussing and Conway. http://www.amazon.com/Orbital-Mechanics-John-E-Prussing/dp/0199837708/ref=sr_1_cc_1?s=aps&ie=UTF8&qid=1386619845&sr=1-1-catcorr&keywords=prussing+conway I've read several texts on orbital mechanics, and this one seems more thorough and organized than most.

Some of them can be recycled. If you've got enough know-how to make your cycler out of a hollowed-out asteroid, they can even be made out of the materials in your ship; you could hollow it out more and more as you go. True. But if you only had to accelerate, say, 200 metric tons to your new velocity, that's going to cost you a lot less than accelerating that mass and the mass of everything you need for the trip to your new velocity. Note that asteroids need not be diverted with lots of fuel. If you have time, you can use a gravitational tug to move it and keep it in the right trajectory, for example. Or you could use solar-powered lasers to vaporize parts of it and divert it into a new course without any fuel expenditure at all (assuming the asteroid has enough gravity to keep dragging you along for the ride). Intially, sure. But if they're recycled or refined on-site, you don't have to change the velocity of enough stuff to take you on the entire trip and back every time you go. That's what's key. You're also assuming that the crew would be returning each trip, and that each new trip would have a new crew. If you have a sufficiently large cycler, why wouldn't they live and work on it in a more permanent way?

Yes, except that the shuttle only has to carry enough consumables for the trip to the cycler. The rocket equation shows you that mass is very, very important in terms of total delta-v gained from a given amount of fuel. Saving the considerable mass needed to carry all the consumables needed from start to finish at each launch is no small thing.

Translational velocity is relative. Rotational velocity is not. If you could cancel all rotational velocity, you'd orbit as in Diagram A. However, many spacecraft in orbit set themselves to rotate with a period as close as possible to their period of revolution around their primary, so in practice, most satellites orbit as in Diagram B. Any satellite left on its own for long enough -- where "long enough" is an amazingly long time -- will eventually be tidally locked with the heavy end pointed towards the center of mass of the primary.

Stellar aberration. http://en.wikipedia.org/wiki/Stellar_aberration

Presumably the same thing the Chinese were thinking when they did it. http://en.wikipedia.org/wiki/2007_Chinese_anti-satellite_missile_test I completely agree that it's kind of a foolish idea. But that doesn't mean that no one will do it.

Yes, they ignored orbital mechanics difficulties, but that's because without doing that, you have no movie. If the disaster that kicks the movie off actually happened, there'd be no survival story. Everyone would be done. The end. No movie. If you want to write a survival story like this, in other words, there are certain things you need to make more convenient than real life. This isn't something that's true of, say, TIE fighters banking, or firing the Icarus II at the Sun to get it to hit the Sun. Those latter ones are simply details that they got wrong and which don't serve the story in any way. I think I'm also more forgiving of errors in Gravity because it's obvious that they were so danged careful to get the physics right where they could in many places(*). All I ask for is an acknowledgement in that regard. It's like the fact that I find a transporter with "Heisenberg compensators" more satisfying than a transporter used without any acknowledgement of the physics that would make a transporter impossible. It's like the writers are saying, "Look, we know this is a problem; but we need it for the story we want to tell, so we'll just agree that it's hard and move on, okay?". --- (*) And yeah, even so, a nitpicker could find a few things wrong that they didn't have to get wrong. I don't think they get in the way while you're watching the movie, though YMM obviously V.

Saw it in IMAX 3D last night also, but had to crash afterward. Amazing movie -- stunning, tense, inspiring. Going to stop now so that I don't accidentally let spoilers slip.

I have an advance ticket to see the movie in IMAX 3D at 10 PM EDT Thursday. I'm eager to see it.

Eighteen days. Yeah, when it came to science, they just. Didn't. Care. You're not going to move an asteroid that the movie called "the size of Texas" (about 1250 km across, larger than 1 Ceres) that far in a year with one nuke. Let's say the thing is made of rock, roughly 2500 kg/m^3. That gives us a total mass of 2.56e+21 kg. If you want to move that at the minimum speed necessary to miss the Earth from a head-on strike in a year, you need to change its speed by 0.202 m/s. That means your nuke, if you could direct all of the energy to asteroid deflection, needs to yield 5.22e+19 joules, or about 12,500 megatons. The largest nuclear bomb ever constructed, the Soviet "Tsar Bomba", had an estimated 50 megatons of explosive yield. I can show you the math if you like.

At the level of science displayed by Armageddon, electricity is magic. So, in the movie, your plan would work. So would hitting it with a wrench. So would squinting at it until the switch felt intimidated. If you're trying to make an RC circuit for real out of the material you just mentioned, you'd need a long wire. The decay time of an RC circuit is proportional to the resistance times the capacitance, and your resistance is pretty close to zero -- meaning that the timer would elapse really, really quickly.

(1) Irrelevant. The general public also probably thinks that heavier objects fall faster, or that you have to point your rocket at the ground to get back down from orbit. (2) If you showed this "general public" a picture of Earth taken from space, would they associate that first with space or with something not-space?

Earth is in space.

Finding out how to use different patched conics modes while focusing on other bodies in the Kerbal system to make planetary approaches much more precise. (Before that, I had to wait until I was near or in a target planet's SOI and spend extra fuel to get the approach I wanted.)

You may recall Stardock as the people who came out with the Galactic Civilizations series -- a 4X game that rivals Master of Orion in depth, with absolutely astounding AI. (Most of what they do is Windows add-ons.) The owner mentioned a fondness for Star Control way back. They had the winning bid for the rights to the "Star Control" name. And they've hired new people to start working on a new game this fall. http://www.stardock.com/about/newsitem.asp?id=446966 I've got my Hunam fingers crossed. Star Control II is one of my favorite games of all time (now freely available as "The Ur-Quan Masters"; you can download it at sc2.sourceforge.net). It will be nice to see more after the name was stuck in IP limbo for so many years; and it just might be good. (I have no idea whether the original creators, Toys for Bob, are at all involved.)

Actually, they left that in. Listen for a reference to a "burst helium disc". ADDING IN EDIT: From the script: JACK SWIGERT - How's it going, Fred. FRED HAISE - I'm okay. [EXPLOSION] JACK SWIGERT - What the hell was that? JIM LOVELL - Let's hope it was just the (helium) burst disk. JIM LOVELL - Houston, can you confirm a burst helium disk? ANDY (CAPCOM - WHITE) - We confirm that, Jim. JIM LOVELL - Houston, is that gonna affect our entry angle at all? ANDY (CAPCOM - WHITE) - Negative. Your entry angle is holding at 6.24, Aquarius. JIM LOVELL - Houston, uh... we sure could use the re-entry procedure up here. When can we expect that?

Or approximately 1.16 miles south of the geographical north pole. Seriously, though, I understand your pain. If you want to see technical screw-ups, all you have to do is watch CNN cover a launch(*). I can still remember when they explained the procedures following a launch postponement by saying that they needed to "remove the fuel from the external tank and the solid rocket boosters". Remove the fuel from the SRBs? With what? A corkscrew? (An understandable slip of the tongue, but it still made me giggle.) (*) I eventually switched to NASA TV. The PAO still talks over the interesting ground-crew chatter, but not in as a consistently intrusive manner as cable news reporters.

Challenger, actually; the MMU's final mission was STS-51A (November 1984). After the accident, investigation showed that missions done with MMUs could also be done effectively with the RMS or traditional tethered EVAs; the extra risk posed by the MMU was considered unnecessary. http://history.nasa.gov/SP-4219/Chapter13.html, page 319

According to the YouTube page, this fan-made trailer was made by stitching together the other trailers that have already been linked in this thread.

I'm thinking this is supposed to happen in some alternate universe where there was a shuttle named Explorer.

I think you're expecting that only things that look like our Moon are "realistic". I agree with your first point -- that the craters seem a bit uniform in size. I haven't actually measured. But if the lava plains were created before the Heavy Bombardment -- or if there was no Heavy Bombardment, so a lot of the craters we see are uniformly distributed in time -- then heavily-crated maria would be realistic for Mun. And the color of the crater floors depends on the underlying material, which may or may not be the same as the Moon's. (Look at Hyperion for a real-life example of dark-bottomed craters.)

I wonder if that "Detached" trailer (thatk you, deadshot462) gives an answer to NovaSilisko's question about why Sandra was ordered to detach, even though it would seem to fling her further away. Here's the order of relevant events as it appears to me in one, continuous take: 1. Sandra complains that her clip is stuck after being ordered to get inside. 2. Debris separates the RMS from the Explorer. For the first few seconds after separation, it seems like Sandra is the most massive part of the new rotating system -- the center of rotation is close to her. Then the camera moves to emphasize her motion and show her disorientation. 3. George orders her to detach, telling her that "the arm will take you too far". He may have seen that the center of mass of the system was moving away too fast, and was hoping that Sandra would time her unclipping to fling herself back towards him so that she would have a shot at rescue. 4. Between Sandra's disorientation, panic, and stuck clip, she releases at the wrong time instead, flinging herself further away -- at least, based on the camera angle, it seems that way. Is that a rationalization too far? Anyone?

KSP as a roguelike, maybe? With significantly more investment into the role-playing aspects of the game, persistent planetary damage, and so on? I'm thinking Dwarf Fortress several dozen times over. The main hurdle for players to overcome, ISTM, would be having to learn to read numbers quickly and efficiently so that piloting could be done in real time.

Different strengths and weaknesses, it seems to me. It doesn't look like SPM would let you fly things directly, or let you slap together a completely new design that the developers hadn't thought of. OTOH, KSP doesn't have a tech tree and research mechanics. (Not yet, anyway; I'm still kind of interested to see how the "discovery" system that they're planning will work.) I'm eager to try SPM. And it should be obvious that I love KSP. But I don't think one has to be exclusive to, or even compete directly with, the other.

All right, thanks. I'll mark this as "Answered", then.