K^2

This is basically along the same lines as question that someone asked about grabbing onto the space station while passing it by on a re-entry trajectory. I'm guessing, that thread got lost with many others in the crash. Basically, yes, relative velocities are too high. But if, say, you used a really long and really strong bungee chord to attach yourself (or your ship) to the station, if nothing breaks, you'll end up with a weighted average of the two velocities (weighted by mass due to conservation of momentum). Whether that puts you and the station on re-entry path or if you stay on orbit will depend on exact trajectories and masses. But station's orbit will most certainly change.

after the fact. Naturally, that would let them filter what does and does not become public, but to merely remark "lets roll" during the liftoff of the first human launch must have taken some restraint. And there are no do-overs there. So I'm guessing, the cosmonauts were also instructed to keep language clean in event that party does decide to make the recordings public for PR purposes.

That's the black sphere result, isn't it? Albedo of most objects results in lower values because they tend to be "ligher" in visible light and "darker" in infrared. Of course, the atmosphere tends to drive the equilibrium the other way.

That doesn't really make a difference. Logic is similar to pendulum fallacy. Now, if control systems varied thrust of individual engines to maintain balance, then spreading engines out would help.

There are a number of issues with VTOL. Biggest one is that the vectoring on engines becomes less and less efficient as the center of thrust is moved higher up towards center of gravity. If center of thrusts ends up above, you actually get engines actively trying to flip the craft over. So first thing is that if there is room at all, move the lifter jets down. Second issue is that gimballing initiates when you fire a stage. If you just activate the engines via action groups, you get no gimball control. So fire all of your engines in one stage, then shut down these you don't need with action groups. When you re-activate these with action groups, they'll work as supposed to. Finally, as fuel is used up, center of mass shifts. Your VTOL might start out perfectly balanced and hover steady, and then a few seconds later start turning over. Before you can properly react, the thing is flipping over. You have to make sure that fuel is being used up symmetrically around center of mass. Not an easy task, but that's the only way you'll get a good VTOL. P.S. Which mod is that cockpit from?

That is the correct relationship for a black body, by the way. Distance should be measured from center, by the way. So if you have distance from surface, add the radius in.

Point mass approximation only works for approximately spherical objects. For a perfectly spherical object, it is exact. Edit: Sorry, didn't notice the post right above mine.

Nozzle diameter also depends on the fuel. You'll probably only get it by trial and error. And avoid metal parts. Once you start getting close to reasonable nozzle sizes, you WILL have explosions.

And what do these "other" titanians feed on? Any food chain on Titan will start with acetylene. That means any life will be found where acetylene is plentiful.

I don't think kerbal's mass is added to the rocket when he's inside. When on EVA, however, you can get a rough idea of the kerbal's mass by using rocket pack to get some speed, and colliding head on with capsule, or some other light object, and seeing how the speeds of the two change after collision. Having tried the "get out and push" solution to trajectory correction after running out of fuel in orbit, I can definitely say that a kerbal is considerably lighter than even the Mk I capsule. But I have not done the math to try and find the exact value.

That would be pointless. Acetylene, which is going to be primary nourishment for these things, is going to be concentrated on surface and in methane pools. Most of the life, if any, is likely to be found in these methane pools. Some might live on rocks and in the sand in "humid" valleys as a thin layer of organic slime.

If that doesn't become an in-joke easter egg in some form, the world will be a little bit less than it could be.

I only understand the effect qualitatively, so I can't tell for sure. But dimensions of the lattice might make a difference. The biggest problem is that I don't know how you'd get rid of all the other emission modes, so it's kind of hard to tell what sort of side effects the non-existing technique would have.

Nope. We are dealing with hard gamma radiation. Can't manipulate that with magnetic field like you can with particle exhaust of any other type of rocket. The only field that can deflect hard gamma radiation significantly is the gravitational field. A gravitational nozzle would certainly help. Ball's back in your field, Stochasty. But in terms of any sort of science we understand, that's basically the absolute limit for a matter-antimatter photon drive. Ok, I can think of one possibility. There might be a way to utilize Mössbauer Effect. That would let you receive recoil from annihilation event by an entire lattice, minimizing heat production. If you can figure out how to emit photons exclusively with this zero-phonon recoil, you can make 100% (or near enough) efficient photon drive of legend. That would be the most efficient reaction drive physically possible. Unfortunately, our current understanding of relevant physics is akin to understanding of aerodynamics available to a caveman who is running in the field flapping two animal skins and wondering why he isn't flying like the birds. Either way, we are missing some very important fundamental science background in order to even approach the engineering problem of practical matter-antimatter engine. But I am surprised to see that some sort of not-entire-useless device could be built with 1960's tech, have we had sufficient stock of antimatter.

Dual-strand provides no real protection against mutation. On the contrary, twice as many places for something to go wrong. RNA, on the other hand, has stronger bonds in the backbone, if memory serves.

"Lighter" won't do you any good. Thickness is determined by absorption, and absorption, at these energies, is pretty much determined by density. So TWR does not depend on how light-weight the material is. Melting point is the only factor. If you could increase that, you'd have more thrust. But alloys always have lower melting point than any constituent, and the only pure material with higher melting point is graphite. The melting point for graphite is only a little higher, and it tends to evaporate away quite easily at high T. So Tungsten is pretty much as good as it gets.

Nah. Looking at accelerations we can get, magnetic confinement of anti-hydrogen will do just fine. I did some estimates on mission times, by the way. 1,500 years to the nearest star. 2% of ship's mass will have to be fuel, with about 95% being the tungsten dome for the engine. That leaves 3% for payload, confinement, and the ion guns. I would propose using pellets of magnetically-confined anti-hydrogen placed in the center of the dome. Pellets will have to be microscopic, so that they don't overheat from their own radiation. But it shouldn't be a problem if we bombard these using an ion gun. So now, the only unsolved challenge is getting enough anti-hydrogen. If we want to get 300kg of equipment to Alpha Centauri, we'll need 200kg of antimatter. Which is slightly more than 309 atoms of hydrogen that made up the largest batch ever made.

[Accidental double-post. Sorry.]

Hm. That leads me down an interesting thought path. I've always considered "ideal" photon drive. One that converts energy into momentum. That assumes you have a "perfect" mirror handy, and none of the heat dissipation factors are a problem. Instead, suppose that we burn matter-antimatter in the middle of a hemisphere. No reflection, pure absorption, so we don't need to worry about parabolic shape. We get À/4À = 1/4 of maximum thrust. That brings us up to 1.2GW / 1N of actual thrust. Now, what are we going to make the "engine" shell out of? It's going to be hot. Really hot. I'm going with Tungsten. We'll need about 1cm thick shell to block all the radiation. Stuff will melt at 3695K, so lets set temperature at 3690K. We'll also be losing heat from 3ÀR² of the surface. (2À from outer surface, À from inner.) Mass will also scale as R², which tells us that TWR of this engine will be a constant regardless of the size. Converting all of this to metric, and introducing density of Tngsten and Stefan-Boltzmann constant, we have the following. Mass: 1.194x103 R² kg. Max power: 99.1x106 R² W. So that's 6.92x10-5 N/kg, or TWR of 7.6x10-6. And that's actually not all that horrible. It is comparable to modern ion thrusters. And while ion thrusters will probably improve significantly in TWR department, the fact that scientists found uses for them even with that TWR suggests that matter-antimatter engines might actually be plausible propulsion method for future space probes. Because Isp of gc/4 is really good if you want to cross interstellar voids.

Depends on how fast you want to go. Each atom/ion you capture is going to impart -γvm of momentum. If you then use matter-antimatter reaction to power an ideal photon drive, you can get at most 2mc of momentum out of it. In other words, you are going to reach terminal velocity when 2c = γv. That's v = 2c/Sqrt(5) = 0.894c. Realistically, of course, your photon drive is not going to be perfect, and your limiting velocity is going to be even lower. In contrast, photon drive that carries its own matter and antimatter follows relativistic rocket formula. It can travel much, much faster. Edit: It might not seem like a big deal. 90% is already almost as fast as you can go. True, from perspective of these remaining on Earth, travel time is not going to be much different if you go 90% or 99% of the speed of light. From perspective of ship's clock, however, this is more than 3x difference. Whether that matters or not depends on application. So again, it's all about how fast you want to go. For an even slower ship, one might consider capturing interstellar medium and using it as fuel for an ion drive powered by matter-antimatter reactor. Then a very small amount of antimatter can go a very long way. Of course, if you do that, you might get away with hydrogen fusion as your power source and then you don't need to bring any fuel.

It's not even just about leaks. Air will diffuse out if there are no leaks. And even metal of which the craft is built will eventually evaporate away. But like Awaras said, these things take really, really long time.

Frozen hydrogen would make a crappy material for magnetic suspension. It is diamagnetic, so it's possible, at least, but its susceptibility is less (by magnitude) than that of water. So against even 1g of acceleration the field strength required would be enormous. Considering the catastrophe that containment failure would result in, I would not pick H2. Unless, of course, you manage to create it in the hypothetical MSMH state. That one should be superconductive, and then it would be fantastic for storage. Of course, existence of MSMH would have so many other applications, it's not even funny. If it does, indeed, exist, I wouldn't be surprised if we one day end up mining comets for it. Out of known materials, for magnetic confinement, the best options are either a superconductor, or at least, some ordinary conductor. For a superconductor, Aluminum is probably the best choice. For conductor, I'd go with Lithium.

Good to know. Thanks. If you ever figure out relationship with lift, let us know.

Yeah... Until we figure out superluminal travel, interstellar conflicts are pointless. Either one civilization outguns the other by so much that it'd be like declaring a war on one of the newly discovered tribes in the Amazon, or warships one side sends will become outdated by the time they reach the other.

Real f(AoA) is also smooth for most surfaces, because separation doesn't happen throughout the entire wing all at once. The stall is just the place where lift starts to decrease rapidly. But yes, it's more abrupt for real wings than in KSP. What about drag, by the way? Does it depend on AoA at all?