K^2

[quote name='sashan']EDF, or electric ducted fan are very popular among modelists who want an RC jet without the danger and expenses of mini jet engine. THe main downside is that the efficiency is 2x lower of the propeller of the same thrust.[/QUOTE] This is because of the scale and low speeds. On the scale and typical cruise speed of commercial airliners, ducted fan is actually more efficient than a prop. Hence the use of high-bypass turbofans in aviation. [img]http://www.homebuiltairplanes.com/forums/attachments/aircraft-design-aerodynamics-new-technology/33926-ducted-fan-aircraft-propulsive-efficiency.jpg[/img] As indicated, efficiency drops once you approach sonic speeds. It's hard to tell how much efficiency you can still squeeze out of an EDF in supersonic. It's entirely possible that if you're looking for an electric supercruise, you are going to be better off with some sort of a variation on thermal jet.

[quote name='wumpus']Depends. Do you mean they decode the image for you or you simply feed the random number generator to your image browser.[/QUOTE] You can provide it with the image, and it will give you a seed that generates it. You can also use random seed, which does, indeed, produce static. But that's exactly the same behavior as the text version.

[quote name='Dieselpower']If you would have any understanding on how the scientific progress works, you would not have a doubt on the strength of the consensus that global warming is caused by humans. [/QUOTE] No, I'm sorry. That is not the consensus. The consensus is that anthropogenic global warming cannot be rejected. There is a big difference. It means we should be working on reducing our impact, because if this change is caused by humans, we are in deep trouble. But we also need a lot more careful, unbiased research. We still don't have a good model for greenhouse effect that doesn't make completely wrong predictions. Unless you are happy with going to stone age based on "everything we do causes global warming," we need to put research into generating less impact. And to do that, we need actual scientific work, and not alarmists running around trying to win elections with it. The more political you people make it, the less chance there are that scientists will actually figure out how to have technological growth and not ruin the environment.

[quote name='parameciumkid']So. I have an awesome KSP ship and I want to convert it into a 3D model (digital I mean, not a real life model) for use in cinematics, porting to games like SpaceEngine, etc. Where can I find a plugin or converter that does this?[/QUOTE] So first of all, someone might have written one that's specifically designed for KSP, which would probably be way easier. You can try asking about it in modding section. Failing that, there are two general options. 1) Unity runs via DirectX on PC. There are tools specifically for ripping 3D models from DX games. 3D Ripper DX is pretty popular, and apparently, people have used it successfully with KSP. So that might be a good way to start. 2) There are some Unity specific tools for ripping models, which might make it easier to get model and corresponding textures together. [url=https://github.com/ata4/disunity/releases][u]Disunity[/u][/url] came up after a brief search, but it is Java, so I don't know if you want to bother. Personally, I'd give 3D Ripper DX a try, since it's something that people have been using for years to rip models from all sorts of games. It usually has the downside of not handling animations, but that's not a problem for KSP. Oh, keep in mind that pretty much regardless of what you use, you'll end up with individual modules, not the whole rocket/plane. You'll have to assemble these together yourself in your favorite 3D editor.

Inertial frame does have a few advantages. The following three come to mind. 1) Old style INS would inherently be locked into inertial frame. This is no longer relevant, since we don't really rely on INS and modern computers can recompute to whatever coordinate system is more convenient, but this was a limitation for Apollo era missions. 2) External forces aside, once you have a hold on a given attitude in inertial frame, you'll stay on that attitude without taxing attitude control. This is not generally true of an arbitrary attitude in orbit frame. 3) It's convenient to do physics in an inertial frame. This is rarely relevant for ship in flight, but it's very convenient in simulation. So if you want to save a conversion step, you might want to stick to inertial frame.

I was thinking something along these lines as well. Though, you'll probably have a lot of trouble punching through transonic region. You might have to do what supercruise-capable jets usually do and have an afterburner for passing the sound barrier. Then you can kill the afterburners and continue on electric.

Lead chromate dissociates according to the following equilibrium equation. PbCrO[sub]4[/sub] ⇌ Pb[sup]2+[/sup] + CrO[sub]4[/sub][sup]2-[/sup] Any time you see dissociation of the form A[sub]p[/sub]B[sub]q[/sub] ⇌ pA + qB, you can write down K[sub]sp[/sub] = [A][sup]p[/sup][B][sup]q[/sup]. Because you just end up with one of each ion here, you have a very simple case p = q = 1. K[sub]sp[/sub] = [Pb[sup]2+[/sup]][CrO[sub]4[/sub][sup]2-[/sup]] Solubility is defined as number of moles of original compound A[sub]p[/sub]B[sub]q[/sub] that can dissolve in a liter of water. Therefore, by definition, solubility S = [A]/p = [B]/q. Solving this together with the general expression for K[sub]sp[/sub] above, one may derive the general expression for solubility. S = (K[sub]sp[/sub] / (p[sup]p[/sup] q[sup]q[/sup]) ) ^ (1/(p+q)) I hope you can substitute in the numbers and get the answer yourself. I would also strongly advise trying to solve this problem for other compounds, where p and q are not 1. If you can't do these, you should talk to you teacher/professor/TA, because otherwise, you'll be in serious trouble at the exam.

You do realize that people who have made that site have already made an image version of it, right?

[quote name='SomeGuy12']1. Can you control the rate of energy release? If it's uncontrolled decay, like RTGs, it doesn't work for flying cars or SSTOs because the reaction can't be stopped (such as when the car lands or the SSTO reaches orbit and needs to reduce heat load) 2. Does it always release gamma rays and neutrons? If yes, then the mass of shielding and the danger makes it unfeasible.[/QUOTE] There is no fission. The decay is from an excited state to a ground state. The only radiation released is gamma, which is easy to shield from. The only radiation that's really hard to shield is neutron, which isn't released, since you don't change the isotope. And yes, you can control the decay rate. That's the whole point. So lets go over this again. 1) Easy to shield. 2) Releases energy on demand. 3) Long shelf life (~30 years half life). 4) Energy density approximately 10,000 times of chemical fuels. Unfortunately, current costs are closer to million times higher than these of chemical fuels, making it impractical for pretty much any application. But there have been some developments in greatly reducing these. In other words, don't hold your breath just yet, but it's the sort of technology that might be coming in the next few decades.

[quote name='wizzlebippi']Wave drag is due to shockwave formation, transonic or supersonic, anywhere on the aircraft.[/QUOTE] Right. But the important feature of wave drag is that it is at its worst near transonic. So slightly bellow to slightly above speed of sound. Hence the ability of some fighters to punch through the transonic with afterburners, then switch off to supercruise and not waste the fuel. Ignoring variations in density with altitude, changes in flight configurations, etc. Typical C[sub]d[/sub] profile is fairly constant until transonic, rise sharply in the transonic region, then fall back to a value "somewhat" higher than sub-sonic, where again, it remains almost constant until you hit hypersonic speeds and it starts to ramp up.

Done this way? Yeah. But there are techniques and tools for encoding data into images that are very secure. As in, if you don't know the key, it will look like compression noise, and you won't even know there is hidden data there.

Pro tip: .com executables are just raw image files loaded at cs:0x100, with es=ds=cs. So you can write your own .com in machine language using a hex editor, then run it with something like DOSBox. It's a good way to learn more about computer architecture as you're learning Assembly.

Quite likely. So we're still going to need to figure out good energy storage if we want to use all that energy for something we're not doing with it now. I still have high hopes for nuclear isomer energy. If someone can figure out a reactor that produces necessary isomers in large quantities without costing too damn much, maybe we can start building flying cars and maybe even electric SSTOs finally.

No, it used to be fifty. Then it was ten for a while. We've only leveled off on 25 in the last 20 years or so.

And it doesn't throw an exception on being used with a real variable, rather than integer? That's just silly. Good catch, though.

This is terribly inefficient, because point_direction computes atan2, and then you run and compute sin and cos from that. You should work out how to avoid this. Hint: What are the definitions of sin and cos and can you compute them from your data? Otherwise, everything looks good. Precession you are seeing is almost certainly the result of time increment being too large and your use of Euler Method for integration. Try reducing time step by re-writing your position update as xx = vx*dt + 0.5*ax*dt*dt. Then try different values for dt starting with 1 and going down. By the way, your missing factor of 0.5 is also wrong, but it just works as arbitrary increase of planet's gravity, which won't affect the types of orbit you get. To get even better results, you can try using better integration method. Nothing works great for gravity, but almost anything will be better than Euler Method. Velocity Verlet is always my first recommendation, because it's really easy to implement and it gives great improvement.

It'd be nice to see your code to actually compute the forces and update the position of the satellite. I have a few guesses on what might be causing this, but I can't be sure on which one it is without seeing the code.

We are still talking about things that are built that way because that's the conditions under which they are being used. None of these are limitations of a particular lifting surface configuration or engine type. A fixed prop will also only work well at certain air speeds. But these can be anything from an ultralight trike speeds to transonic high-altitude transports and bombers. And you can build a biplane that'll handle a reentry from orbit if you were set on it. So what I'm really missing is how any of this factors into discussion of lifting bodies. Especially when we clearly see lifting bodies used both for hypersonic flight and for very slow takeoffs/landings. These are very differently looking lifting bodies, but you kind of expect that.

What? Now Mars is going to get a ring too? This is a conspiracy by other planets against Earth. I say we keep launching crap into space until we have a ring of our own.

That's just Reynolds number doing its thing, though. If we design an aircraft to fly at 250kts clean at sea level, it will need to fly at 500kts clean at 36k feet, because dynamic pressure needs to stay the same. Consequently, former is the typical early approach speed, while later is minimal cruise. Again, not a whole lot you can do here in terms of aerodynamics. If you wanted to design an aircraft for slow maneuvering at FL400, you absolutely could. It'd be extra slow and clumsy at sea level, however, which isn't what you want with a commercial aircraft.

Any aircraft traveling at 500kts doing a 30° turn, which is max bank set by FAA for commercial flights, will make a circle nearly 25km in diameter. This has nothing to do with flight characteristics of an aircraft, though. You can't make a tighter turn at that speed without increasing the bank angle.

That's what flying ever is. Applying thrust is equivalent to changing the angle of gravity, at which point, you just happen to be "gliding down" at a constant altitude.

That is a somewhat oversimplified view of lift. The reason lift is generated on any body is due to circulation. The precise statement is in Kutta-Joukowski Theorem. Circulation is generated in the air stream by combination of body geometry and angle of attack. A brick will generate lift given proper angle of attack. The main reason for all the curves on the wing is actually to reduce drag and increase the critical angle of attack, which allows for much better flight characteristic. Camber on a wing can also allow for positive lift with zero angle of attack, which may be convenient, but isn't strictly necessary. Many jet fighters have symmetrical wings and generate lift purely due to angle of attack. A body can also have a negative lift due to camber, and still have net positive lift due to high angle of attack. M2-F1 appears to be such a case. All of the pictures have it flying with significant nose-up attitude, which is probably necessary for it to generate lift. IIRC, such aircraft tend to have pretty lousy flight characteristics at high speeds, but allow for very low speed landings/takeoffs, making them of some interest to navy.

Which is consistent with "universe has no volume" claim. Although, I also found it to be oddly phrased.

It's more precise to say that it's a mathematical construct with some useful dualities to the observable reality. But it absolutely should not be taken at face value, yes. It is not a scientific theory in the way that components of Standard Model are. Everything I've mentioned about Big Bang in this thread is based on Standard Model, however.