K^2

I have a feeling people here don't appreciate how long the tether has to be. Research done so far suggests that the angular velocity should not exceed 2rpm in the long term. From center of mass, that's over 22m of tether or other support for every .1G. If you want to have at least 0.5G on board of a rigid ship your ship is going to be longer than ISS. The advantage of the tether is that it can be extended and contracted in flight. With a rigid structure, you will have to build your ship in Earth's orbit, then navigate that long, clumsy thing to Mars, do the mission, and on the return trip, transfer the crew from the Mars lander to command module on the orbiter. Compared to that, tether seems safe, and that's saying something. Whenever we get to the point where we have routine missions to Mars, we'll have to figure out how to do this reliably and safely. But for the first few missions, there is really no good reason for this. There are enough things that can go wrong with a mission to Mars. Why add one more such thing? Personally, I'd do the mission to Mars in the following manner. 1) Living module with supplies is delivered to LEO without a crew. 2) Mars lander is delivered to LEO without a crew. 3) Command module and interplanetary rocket is delivered to LEO with the crew. 4) CM docks with living module. 5) Living module docks with lander. 6) Burn from LEO to escape and establish transfer orbit. 7) Burn to establish low Mars orbit. 8) Lander separates from living module and lands on the surface of the Red planet with the crew. 9) Lander takes off and returns to Mars orbit to dock. 10) Lander is abandoned and the rest of the ship performs a burn to leave Mars and enter transfer to Earth. 11) CM separates from the rest of the ship and re-enters the atmosphere. The rest of the ship crashes somewhere in the ocean. There are several advantages to staging mission like this. You deliver the ship to orbit in manageable chunks, but without significant risk of stranding the crew in orbit without means of re-entering. You also don't waste fuel on things you don't have to carry with you. A spacious living module is necessary for both legs of the trip, but there is no need to haul the lander back from Mars. Likewise, there is absolutely no need to make the living module capable of surviving re-entry. A small command module can carry the crew safely back to Earth. The only place I can think of where significant fuel savings can be made is if lander separates from living module still on approach to Mars and does direct entry while the orbiter establishes orbit. But this seems like an increased risk to the mission. Edit: I should do some estimates on the actual requirements for this mission. I'll be back with some numbers a bit later.

Matter-antimatter drive could also produce radioactive waste. In fact, anything with sufficient power output probably will. H-fusion won't work as realistic energy source for these kinds of ships even if you found a magic way of turning that energy directly into kinetic energy of the craft without any waste. Even to get to .1c the hydrogen you'd need for fuel would be much heavier than the ship itself.

The theoretical work is also plagued with errors. At best, Q-thruster is a crappy photon drive. Which means you'll need over 300kW per 1N of thrust, rather than 3kW that the Wikipedia article suggests. The final "exhaust" of such a drive is still going to be electromagnetic radiation with total energy and momentum conserved. There is no way around that in quantum field theory.

That's where inviscid assumption comes in. It eliminates any losses for gas going through the tube. For a more realistic estimate, you'd have to take into account the pressure differential across the tube. The thrust will then be equal to the pressure at the outer end of the tube times the cross section of the tube. And you compute pressure differential based on the flow rate. Unfortunately, things get a little complicated here. For incompressible fluid the solution is rather simple, but for a gas it's a bit more complicated. I would still expect the flow rate to be roughly proportional to the pressure differential, but any estimates I'd make on the proportionality constant are likely to be way off.

No. It doesn't work like that. Only relative velocities are relevant. Once you enter SOI, your velocity relative to Mun becomes your orbital velocity in Mun's SOI. And entering SOI with basically any velocity puts you on a hyperbolic trajectory that will return you to the edge of SOI going at the same speed and you are going to escape. Now, when you escape, you'll be traveling in different direction, so these speeds will add differently. Your orbital speed relative to Kerbin will change. For this reason, it's possible to get captured by Kerbin or any other planet with moons. But it's not possible to get captured by the Mun because there is nothing to adjust your velocity while in Mun's SOI.

Switch your navball to show orbital velocity instead of surface velocity. At about 8-10 km, when you begin your rotation, just get your prograde marker to point straight north. For a polar orbit, that will get you a perfect orbit regardless of anything else. If you want some other inclination, you might have to make some further adjustments, depending on how far your position has shifted, but you should still be able to get very close.

I don't use quicksaves. I try to build all of my craft with enough redundancy for a safe landing in event that something goes wrong. I've had quite a few kerbals stranded somewhere because of this, requiring complex rescue missions, but I've actually lost very few.

Under assumption of inviscid fluid, your best bet for an estimate is force balance. You know that the thrust is given by F = PA. But you can also derive thrust from exhaust velocity. F = vm', where m' is the mass flow rate equal to AvÃÂ. In other words, PA = F = ÃÂAv². For an ideal gas, you can also express density in terms of pressure. à= PM/(RT), where M is molar mass of the gas, 0.044kg/mol for CO2. So we have PA = PAMv²/(RT). Or v² = RT/M. Of course, you should keep in mind that temperature is going to drop as pressure does, with PVγ remaining constant if the contents are just gas. At room temperature, the exhaust velocity will start at 238m/s and it's going to drop as the contents cool down. Naturally, all of this is true for operation in vacuum. When operating in atmosphere, pressure differential will enter into all of this and things will be a little different.

Your CoL needs to be closer to CoM. Having it too far behind makes it difficult to take off. The other problem is landing gear, as Snooze said. It's ok to have too much, but the further back the rear-most gear is the harder it is to rotate for takeoff. Your rear-most landing gear should be only slightly behind CoM as well.

Yeah, save for glitches with warp, it's a violation of KSP physics to be gravity-captured by another object. You have only two options. Either you enter and leave SOI at the same speed, or you physically encounter the object or its atmosphere, which will certainly end in you crashing on that object sooner or later. It might be possible to lithobrake into the tallest point on the body and bounce just right to establish an extremely low orbit, but even that should eventually lead you into crashing into the same point. Though, it's possible to match periods in a way that it'd take almost forever to happen. That is the only way to end up "captured" into an effectively stable orbit without exploiting any glitches in physics.

Yes, it's definitely possible with good timing and staging. You will have to have at least two stages, because while RT-10 does have delta-V reserve that would be sufficient for a good rocket to reach orbit, its TWR is too high to make use of that delta-V reserve efficiently, meaning you wouldn't be able to ride one to orbit. With two stages you can build a craft that has more than sufficient delta-V at whatever TWR you end up with, so what you'll actually end up having to do is turn around at just the right moment and use the remaining SRB fuel of the second stage to slow you down. Then you might have to do a few more flips to make sure you don't overshoot either way. Alternatively, you can build the whole thing to allow it to jettison the second stage boosters once in proper orbit. I might have to try this. I'll post back if I get anything cool out of it. P.S. I'd buy a beer for whoever first came up with term "lighobraking".

You can do gradual thrust control with a hybrid. But then you sacrifice fuel efficiency, so it's not really worth it. With proper TWR, there should not really be a reason to do anything other than full throttle or nothing. Edit: In fact, from the very page you linked. "Start/stop/restart and throttling are all achievable with appropriate oxidizer control."

Fyrem, just to be clear, the "fake" L3-L5 of KSP are completely unstable. The real L4 and L5 are stable and the L3 is only radially unstable. So while you can probably place a satellite close enough to where these poitns would be in KSP, given enough time, they will drift off. With real Lagrangian points, there is some stability you can utilize.

It does actually work in real life. If you have a star with a single planet and no moons, a ship reasonably close to L4/5 will actually stay there indefinitely. In a system with more than two bodies, fixed Lagrangian points do not exist at all. Not even as mathematical equations.

You are completely wrong. L4 and L5 are stable. That means that if you put something sufficiently close, it will stay there indefinitely. The only reason things fall out of real L4/5 is that real systems are not 3-body systems. We don't have just Sun and Earth. We also have the Moon in Earth's orbit and all the other planets. The other objects will cause equilibrium points to shift periodically and that does, occasionally, knock something out of the L4/5. This is not a matter of precision. Something precisely at that point would still be knocked out. And without such perturbation, something practically close would never be knocked out. The other Lagrangian points are not stable, but they have stable orbits around them. So again, you can put something very close and make it stay there. And again, the reason these orbits aren't permanent is largely due to other objects. Ultimately, none of these are "just points". While true equilibrium only exists at a point, there is an attractor region around that point. So in practice, you are interested in a finite region of space. Not in just one point.

I'm not sure what you are trying to say, but if you are saying that they have no practical use, it is incorrect. L1 of Earth-Sun system is used by some solar observation stations, and L2 is going to be used for Webb telescope. Other points are, indeed, not terribly practical. They do, however, have some astronomical significance. The L4 and L5 of Jupiter, for example, hold a lot of asteroids. While one of such points for Earth-Sun system may have been the source of the object resulting in Giant Impact. And you wouldn't be able to use conic sections to describe trajectories of other ships and debris, which might actually be a bigger issue. You might throw more processing power at predicting path of one simulated ship, but if you had to simulate all of the ships and debris in the system it'd be a huge hike in necessary computational power.

This isn't exactly right. The forces in the rotating frame balance out. In other words, you stay in the same place in relation to the two bodies. This doesn't mean that the gravitational force is zero, since staying at the same point relative to two orbiting objects requires acceleration. These points aren't all stable, either. So you wouldn't stay at that point indefinitely. A very small perturbation would result in you eventually leaving the Lagrange point. There are, however, some dynamically stable arrangements, like the Halo Orbits and Lissajous Orbits.

I wrote a tutorial before the big crash. It has now gone the way of the dodo. Basically, think of fuel drain order as fulfilling a request. Here is the loose algorithm. 1) Part is asked for fuel. 2) Are there any fuel lines to the part? If so, ask the connected parts for fuel. If more than one respond, fuel is split equally. 3) If no fuel came in from fuel lines (or no fuel lines) ask any parts directly connected to this one for fuel. If more than one is connected, same drill, split the fuel. 4) If no fuel came from connected parts either, fulfill request from this part. 5) If you got to this point and there is no fuel in the part either, then the request is not fulfilled. Naturally, you start this chain of requests from the engine and any part that's been already requested fuel from will not be requested a second time. So naturally, requests are fulfilled from furthest tank from the engine, with fuel lines given priority over direct connections. So in order for drop tanks to deplete first, you need a fuel line that runs from drop tanks to the tanks that currently deplete first. P.S. Your TWR is a bit low. Even with a space plane you generally want something over 1.0. Preferably, something closer to 2.0.

The only standard maneuver involving these is the inclination change done with normal/anti-normal burn. The formula is delta-V = 2 V * Sin(f/2), where V is your current velocity and f is the angle by which you want to change the inclination at a given point. For radial/anti-radial it all depends on maneuver you want to perform. They are never efficient, however. The only time you should do radial/anti-radial is for small corrections to meet the target at an intercept. In all other situations, you should be trying to use prograde/retrograde burns instead. Edit: Docking and landing are a different story, of course.

Diffraction experiments are easy to set up. But diffraction isn't the point of double-slit experiment. The point is that diffraction effect goes away when you observe which slit the particle passed through.

Yourself is absolutely correct about this one. The interaction between observed and observer alters the dynamics. There is nothing "magical" about Quantum Physics. It's very straight forward field mechanics. Same deal with Quantum Zeno. They are not, strictly speaking, discrete, either. You can store "half" of an electron in a box. You simply can't measure "half" of an electron. Any measurement is going to result in a discrete quantity, and so the overall dynamics is such that we can talk about superposition of discrete states instead. You do change the experiment. That's not the point, however. The statement is far more fundamental. You cannot make an observation that does not alter the outcome in such a way. In other words, any interaction sufficient for you to make a determination is sufficient to offset the balance in the system. The proof of quantum mechanics, however, is not in such qualitative experiments so much as it is in quantitative measurements. Certain predictions of Quantum Mechanics are among the best tested predictions of physics.

There are going to be enough toxic compounds in the atmosphere to make you not want to breath the air even if you warm it up and add some oxygen. You don't need a pressure suit on Titan, but you do need a full breathing apparatus. And something really warm to wear.

It will strip the valence electron off sodium, and you'll end up with sodium ions in chamber instead of xenon ions. No bonds will be made.

KSP rockets are tiny compared to the real thing. And large things appear to be moving much slower. The real rockets lift off at right around 1G, however, about the same as a KSP rocket.

There is one line in the .craft file that specifies if it's meant to be a VAB or SPH vehicle. I don't know if it matters, but it's easy enough to edit in notepad. There can be some glitches with CoM/CoT/CoL markers and symmetry modes, so be prepared for it.