K^2

And I'm saying that we're obviously not interested in something like Phobos or Deimos, because we'd industrialize Moon long before these rocks would become of any use. We are looking for places where we can place a long-term human habitat and do some science. Phobos and Deimos aren't it, because as people pointed out, we might as well just put a station in orbit with same success. As far as interesting places go, we're back to Martian surface or Venusian clouds. And a cloud base on Venus has a lot of advantages. Once built, it can be pretty much self-sustaining. The fact that internal pressure matches external means that a small leak isn't an instant suffocation risk to everyone on board. That means that we could build fairly extensive greenhouses without requiring special materials, and patch them up as necessary. There is also a matter of exploration. Building flying vehicles on Mars is tricky, and you can't exactly go at highway speeds on the surface. Meaning you'd be limited to working in immediate proximity of the base. You'll run out of interesting things in a hurry. Whereas on Venus, your options for flight are pretty much the same as on Earth, meaning you have access to large area for study. You wouldn't be able to land anywhere, but you'd be able to fly to location of interest and simply drop off a probe. If you need to retrieve something from the surface, all you need is a weather balloon.

Most of these we have on the Moon, which is much closer and easier to reach. Yet we're still to build any mining facilities there. And before you say anything, 10km of rail @ ~30g is enough to launch cargo directly from Moon to Earth (or LEO) for pennies on the pound.

There is one very important distinction that makes Venus a better destination for manned missions. Much shorter mission duration.

That is the correct way of doing it. You can also integrate fuel usage using similar technique to deriving rocket formula in the first place, and you will get the same answer.

On these scales, you have to drop Newtonian gravity and talk about General Relativity, which is a bit difficult without getting into jargon and mathematics of it, but I'll try. So the first thing to understand is that in GR there is no such thing as a force of gravity. It's like centrifugal force. It shows up as a force in a chosen reference frame because the frame of reference is accelerating. Thus it is called a fictitious or inertial force. If you aren't familiar with the concept, I strongly urge you to read the Wikipedia article on Centrifugal Force. It's one of the simplest fictitious forces, and one we are all familiar with, so it's very easy to get intuitive feel for it. Long story short, gravity in GR is also a fictitious force. So long as an object is in free fall, there is no net force acting on that object, according to GR. Which is where we get to the question of relative accelerations and relative velocities. When relativity is discussed, you've probably heard people talking about velocities being relative. That there is no such thing as absolute frame of reference for velocity. An object stationary according to one observer is moving according to another, and neither is wrong. Well, things get a lot worse in GR. Relative velocity between two objects isn't really a solid concept anymore either. Rotation is a good example, again. Put two objects on a turntable. According to an observer standing on that same table, two objects are at rest, and so their relative velocity is always zero. An inertial observer standing nearby will watch two objects turn around each other, so their relative velocity is constantly changing. I.e, there is no way to select an inertial observer so that relative velocity is always the same as that for rotating observer. Of course, in Newtonian physics, the rotation example isn't a problem. You can always choose a global reference frame that's inertial everywhere. Not so in GR, because of space-time curvature. You can always pick a frame of reference that is locally inertial, but if you try to extend that frame of reference, you quickly find that it's not inertial everywhere else. So there is no such thing as a "non rotating" frame of reference. Lacking such universal frame of reference, any frame of reference is as good as any other. I can take any collection of the objects buzzing through the universe, some of which in free fall, others accelerating, and simply declare that each one of them is stationary, regardless of any forces acting on them. I can them build a coordinate system in which this is true. So the question of two objects being stationary with respect to each other looses all meaning on intergalactic scale. You can always choose a frame of reference where it's true, and you can always choose a frame of reference where it's not.

Well, I moved to Pittsburgh from Ohio, and it wasn't nearly far enough. So now I live in Cali. Hope that does it. Getting into astronaut training is pretty hard.

A superpower suddenly faced with the threat of an ICBM nuclear attack by another superpower during a cold war standoff. When Soviets have launched Gagarin into space in '61, they've demonstrated capability of delivering a nuclear strike without relying on bombers. I don't recall if USSR has made it public at the time, but at least two Vostok rockets were standing ready to deliver nuclear weapons by '62. US needed a way to defend against a nuclear strike, and they were trying every option. Including detonating their own nuke on the path of an incoming missile. Given the sudden emergence of a threat that, at the time, was absolutely impossible to defend against, you can bet these tests were done hastily.

I haven't looked at the original article, but I can think of at least two ways. First, there is a pretty good pool of stars with precisely known masses. There are close binaries, where we can measure semi-major axis and period rather precisely, and there are some systems with enough exoplanet data to get a fine estimate on star's mass. These can be used to calibrate the model, but I don't know if there are enough such stars to get a good enough sigma on it. Second method is purely statistical. We have a set of estimates of stellar masses from their brightness. The variance is high, but the data set is huge. We also have measurements of periodical variations in brightness. This is a direct measurement, which is far, far more precise than our estimate of the masses. We now have a parametrized model that links the later to the former. Simple Bayesian analysis of our mass estimates with some large σ and the model gives us an estimate on model's parameters. Here is the kicker. Because the data set is huge, so long as the model is working, the variance on parameters is going to be far, far smaller. And for large data set, goes to a quantity related to the variance of indirect data. Plug that back into the model, and you get a new estimate for stars' brightness, which is far tighter than original σ. This gives you the new error bars. If these guys did their homework, they have done both. Probably the statistical analysis first, since it gives better control of the errors, and then tests against known stars for better confidence.

Without air resistance and with short burn time (long coast time), maximum distance traveled when fired at 45° angle is twice the maximum height achieved when fired straight up. However, that's hardly reasonable assumption for a model rocket. Unfortunately, there is no formula you can simply plug this into to get the distance. Even if we ignore the engine thrust profile, and you simply shoot model rocket from a slingshot, air resistance is significant, and there is no analytic solution for ballistic trajectory with drag. That means, the only thing you can do is plug the numbers into a computer model and run a simulation. Quadratic drag with constant drag coefficient gives reasonable approximation for a model rocket. Drag coefficient can be acquired by simply playing with the number until you get correct altitude for the given rocket motor. Of course, that assumes a known thrust profile, which you can usually get from rocket motor's manufacturer.

Short term, maybe. Long term, very doubtful. Russia still has an edge on heavy lifters. They should focus on that. Ideally, I would say, while also developing cheaper alternative for manned launches, but my hopes aren't particularly high there. There were enough problems with corruption and shortage of skilled professionals to begin with. But with economic situation being what it is, expecting them to turn it around in the next decade is silly.

The unique advantage of a QC is parallel computation. Which is precisely the feature the shader code is designed for. Except, in graphics card, we achieve parallel computation by having thousands of identical cores running this code in lockstep. QC can do all of this with a single core.

Do you happen to know how graphics hardware works? I'll give you a hint, exactly like a Quantum Computer.

Sure, a QC won't help you to add two numbers together, but if you have a thousand pairs of numbers, QC can compute all of the sums in one operation. Since that's where all of our computational technology is going, especially in graphics, this is actually very valuable. There are very serious physical limitations in building practical QCs. If we were to overcome them, they would make absolutely fantastic general purpose computers, allowing us to do things we couldn't dream of with ICs. But I wouldn't hold one's breath. So QCs don't suck at general purpose computation. We just haven't learned how to build ones that don't. There is some fantastic work on Quantum Error Correction out there, though. That's severely oversimplified, but not wrong. The more complex a quantum system is, the more sensitive it becomes to errors due to random interactions. Currently, it means that for general purpose QC, we are limited to something between 10 and 15 qubits. And that's just not very useful. Although, specialized QCs exist with hundreds of qubits, that is achieved by extremely narrow specialization. D-Wave QCs are a good example. While it can't solve general problems, it's catching up fast with computational clusters on ability to crunch out artificial neural nets, and is expected to surpass them in near future.

Turbines have alternating stator and rotor stages, which cancel out the torque. Otherwise, torque would be quite significant. In propeller aircraft, there is no such mechanism, and torque from the prop has to be countered by control surfaces of the aircraft. But as I pointed out above, the only reason this matters is because angular momentum is being passed to the outflow.

Doesn't matter. SomeGuy123 summarized it already. For angular momentum of the rocket to change, something must carry it away. Unless exhaust itself is angled and/or rotating, you can't come up with any sort of internal piping that will cause the rocket to rotate. This is no different than trying to accelerate a rocket without having some sort of an exhaust. Just like linear momentum, angular momentum has to go somewhere.

Betelgeuse is frigin' bright. If you can't see it through the twilight, you ain't lookin' right. And if the Sun's right in it, then the Sirius should be visible. Not the same constellation, but it will guide you to the belt.

If all goes right, significantly less debris. We should be establishing stations, with all of the Earth-to-Orbit hops being very low energy, leaving debris to decay. Something like a launch loop would be ideal, of course, but either way, we can't be leaving this sort of mess behind even in the 21st, let alone consecutive centuries.

What it conveys to me, and dare I say, what it is meant to convey, is that we've been waaaaaaaaaay busier in space than most people seem to think. Yes, a disclaimer might be nice, because a few people might get confused. But calling it rubbish is absolutely unfounded.

In Southern latitudes, it's basically a year-round constellation. Sun passes very close to it during part of the year, but it's a large constellation. So some part of it is going to be visible at dawn/dusk anyways. In contrast, from arctic circle, you'd hardly ever see Orion.

It represents quantity and expanse occupied by debris. The only thing it doesn't represent is the actual density, but that's not very relevant. And if you think this representation is rubbish, you must also think that every single representation of Solar System is equally rubbish. When you talk about things on cosmic scale, even this close to home, maintaining proportion between objects is a fool's task. You can't come up with anything useful by doing so.

I really, really wish we could talk about anything to do with Russian Space Program that doesn't land us knee-deep in politics. Not quite to same extent, I wish the same for other space programs. But fair enough. Consider me off the topic.

As an American, you should take a note of garbage Trump says and his standings in the polls. We have a very serious backwash from religious groups right now. Partly because of the aging population. Blame the baby-boomers. People tend to get somewhat irrational and dogmatic in the later years, and right now they happen to have quite a big sway, both in politics and in pols like this. Don't mind it, though, we just need to ride it out for another decade or so, tops. It's already getting better. The fact that radicals are getting crazier and more aggressive is a good sign. Death throws of sorts. The bigger problem is the dent they are leaving in our education system. I swear, the students I was getting in Physics labs were getting dumber semester to semester between 2008 and 2012.

Laws of heavenly motion. Earth is at the center of creation, and heaven revolves around an axis passing through it at a constant rate. All bodies in heaven are attracted to each other by a force proportional to the product of their masses and inversely proportional to the distance between them. All bodies in heaven are attracted to Earth by a force proportional to their mass and inversely proportional to distance from Earth. All bodies in heaven are repelled from the axis of rotation by a force proportional to their mass and distance from the axis. All bodies in heaven are acted on by the force that is proportional to their mass and speed perpendicular to the axis and is directed on the line perpendicular both to their velocity and axis of rotation. All bodies in heaven are pushed along the line connecting Sun to Earth by a force proportional to the mass of the body. That covers the dominant forces. Should be sufficient to stand up to the test by any lay person with a telescope and a lot of spare time. Doesn't account for Sun's wobble or Earth Sun orbit's eccentricity, but that requires more careful observations done by scientific community, and these guys are obviously a part of the grand conspiracy to keep the truth hidden.

That's not how extending the logic works. In fact, that's not how logic works.

Basically, easier to embezzle budget money. When you have a federal agency doing the launches, there is no middle man and there is a lot of transparency. When you have a state corporation doing the launches, the later can pad the bill, and cut a kickback to the gov't officials to have that excess approved. Of course, since it's a state corporation, nobody is actually competing for the contract. So there is no chance of being underbid, and no transparency. Everybody wins. Except the tax payers.