andrewas

The phase angle is needed if you want to do a hohmann transfer, since if your transfer orbit exactly touches the destination orbit, theres only one time you can launch and have the target planet be there when you get there. But if you are willing to burn more deltaV, you can launch anytime. If you have a decent grasp of orbital mechanics, you can just play with the maneuver nodes until you get an intercept. Some angles will require an huge amount of deltaV, but you can usually get where you want to go if you have a reasonably powerful ship.

The math is on the forum somewhere, it turns out that if you transmit enough, you get all the possible science points, exactly the same as if you returned every experiment for 100% value. But for an experiment with a 20% transmit rate, you need 50 transmissions to get all those science points, so I'd rather fly there and back a couple of times. Transmission makes more sense for more distant targets, so grab a beer and keep cycling your science bay and goo container while sitting on Eve or the moons of jool.

Fell off a Mun rocket during ascent. Turns out you need additional ladders to hold on to if you want to get an EVA report from the low atmosphere. Who knew? I think the rocket is still up there somewhere.

Different experiments have different transmit percentages. This is to represent the difference between, say, getting a Duna rock back to kerbin for analysis, and sending pictures of a Duna rock so the scientists can look at them. That said, if you transmit enough, you will eventually get all the science points that experiment can return, though it takes a lot of transmission to get all the science from an experiment with 20% transmission efficiency, almost 50 transmissions IIRC. The exact figures are somewhere on the forum.

Most engines generate power while they run - so transmit during burns. Manoeuvring and transmitting burn power, so be very light on the controls, do not let SAS run for a long period on a large ship, and be very careful when it comes to sending data home. You should be able to get enough science on and around Kerbin to unlock solar panels. You can get 29.9 just by sending a command pod to the launchpad and taking a crew report, EVA report of the launchpad, KSC and 'flying over kerbin's shores' (IE, standing on the command pod ladder), and take samples of the launchpad and KSC itself. The runway may or may not supply more science, I cba walking that far and I haven't done any spaceplanes yet. Next up .. polar orbiter, be patient and get EVA reports over all of Kerbin's biomes. Take some goo canisters along, they don't react to biomes but you have launchpad, lower atmosphere, upper atmosphere and space. That should get you enough to get you to at least the basic solar panel. If not, a munar flyby should do the trick.

A USB socket isn't the ideal way to do this. Inductive power transfer would be better. Phones and MP3 players and such tend to live in your pocket the majority of the day, so implant a fuel cell and inductive charger and never have a flat battery again.

That pin is for the serial interface, theres no radio functionality there. Servo PWM is .. well, not actually PWM for starters. They look at the width of the high pulse rather than the duty cycle. Any stream of pulses between about 40hz and 200hz will trigger them, and mains voltage is 50 or 60 hz depending on where you are, so its not surprising that theres some random noise about thats suited to triggering a servo randomly.

Tell me you're not talking about e-cat?

That depends on the difference in binding energy between the atoms you start with and the atoms you wind up with. You're talking about fusing two protons into a diproton, then the diproton is decaying into two protons. End result - zero net energy change. The second step releases exactly the heat consumed in the first step.

You think you can fuse H1+H1 -> diproton, then let the diproton decay back to H1, and you get energy out of it? No. Thats like generating power by electrolysing water and burning the products. Its a perpetual motion machine. Even if cold fusion was workable, this reaction isn't.

Amongst people who care to learn, yes. Most of the people I know are only interested in football teams or stupid celebrities. Anything real, and they aren't interested.

So if you start with a pair of deuterium nuclei, and end of with a pair of deuterium nuclei, where is the energy coming from? And, for that matter, what takes apart the He4? He4 is stable. Or maybe you meant to fuse regular hydrogen-1 into helium-2. Problem is, He2 immediately collapses back into a pair of H1, again leaving you with no net energy change. On very rare occasion He2 instead undergoes beta decay into deuterium. That is an energy producing reaction, but its one that runs very slowly even under the conditions found in the core of the sun, so its not a good candidate for any type of fusion reactor.

The idea is that you carry a portal to destination. But since its already been demonstrated that you can fire a portal to the moon, its probably easier to fire just a portal at the destination planet, at least for in-system work, leaving the portal drive to be used for interstellar travel. Although, some planets may not have a portal-compatible surface like the moon does. Johnson never does really explain how that works.

A given reaction will have the same products no matter how you trigger it. There are reactions that produce less radiation than simple deuterium fusion, but they are all much harder to trigger and thus even less plausible for cold fusion, or even hot fusion, than deuterium. Maybe in the future we'll have reactors running the proton+b11 reaction, but right now we can't even get net energy from simple H2+H2.

Yes, Jupiter, the moon and various other bodies tend to perturb objects that would otherwise hit Earth. This conversation is about the exceptional body that is on the perfect trajectory to actually hit us. Jupiter deflecting 99% of all asteroids does us no good if the one that gets through is massive enough. Also, theres no natural end to the 'planet killer' period - we'll never run out of asteroids large enough to cause major damage. Sooner or later one of them will hit us. Hypothetically, if we got into asteroid mining in a big way, we could locate and control all threatening asteroids as part of the mining process. But, right now, it doesn't look like we'll ever bother with anything off Earth again, so we're going to have to stop one of them on relatively short notice or go extinct. And even in the best case, where off-world industry generates the infrastructure to easily detect and redirect and threatening asteroid, there's always the slim chance of something coming in from the Oort cloud on an impact trajectory. Consider C/2013 A1, which came from nowhere and will pass very close to Mars. Its estimated to be about 4Km across and will pass at 56Km/s - a similar rock on an impact trajectory with Earth would kill everything on the planet.

Its the RTG Cask - it stored the fuel element for the radiothermal generator during flight.

Short answer - yes. Longer answer - Conservation of angular momentum. If you have an external force applying a torque on the spacecraft, the CMGs or reaction wheels absorb the angular momentum and keep the craft stable. If the force is on-going, as with radiation pressure or gravity torque generally are, then your CMGs or reaction wheels will eventually saturate and you will need to dump the momentum using RCS or some other interaction with the outside universe. Depending on the mission, it may be possible to rotate the craft and reverse the external effect, in which case you can avoid saturating the CMGs in the first place. But if you need to keep a constant orientation than you need thrusters. Or you could do something clever, like pumping fuel around the craft to alter the effect of gravity torque, or moving solar panels to alter radiation pressure, but those are more complex solutions and additional points of failure, so they are not used in the real world to my knowledge.

In theory it is, but the wheels would have to be very heavy or very fast to provide enough control authority. Since launchers have very tight mass budgets, and there are limits on how fast a wheel can spin, its not practical in reality.

Um. No. When you jump, you still have the velocity you had when you were on the floor, plus the velocity you had when you jumped, which puts you on a straight line trajectory (when viewed from a non-rotating reference) which brings you back into contact with the ground, and when viewed from inside the habitat looks very much like a jump and landing performed under normal gravity.

True, we can't completely duplicate the martian environment on Earth, but we can at least build a contained colony on Earth, allowing it only resources that could be found on Mars, and seeing how the equipment and personnel cope over a few years. The costs are trivial compared to a martian colony. Also, the last time we tried this, it was a major failure. Granted, we learned from biosphere 2's mistakes, and a lot of the problems were down to the people running it rather than any technological failure, but still, we can't yet build a contained ecosystem that will remain stable for a few years, even with humans there to manage it. And while this is going on, a rotating habitat in LEO would allow us to examine the long-term effects of martian gravity. Or perhaps long-stay missions on the moon are a better option, we could get some research done while monitoring the health of the crew. Short version - martian colonisation is a long term goal, attempting to do it right now will end catastrophically, but there are steps towards it we should be taking.

Simple enough. Your craft picks up some unwanted rotation, usually from a tiny but on-going force. Tidal forces from Earth, radiation pressure. To keep orientation, the reaction wheels spin up and transfer angular momentum from the craft to the wheel - but you can't spin them down again without dumping that momentum back into the craft. Since the external force is continuous, the reaction wheels have to constantly accelerate to counter is and eventually hit their safety limit and, without thrusters, you lose the ability to maintain orientation.

In freefall?

That one is true, in that the manhole cover was launched at several times escape velocity. They don't think it actually made it out of the atmosphere with enough velocity to escape, though. Story: http://professionalparanoid.wordpress.com/the-fastest-man-made-object-ever-a-nuclear-powered-manhole-cover-true/

Its linear to the area of the 'chute. Double the radius and it takes four times the mass to drag it down at the same rate. That said, mass of the 'chute is another problem, you need to use stronger fabric and lines on a larger 'chute, so the mass does grow faster than linear.

Up to a point. Mirrors aren't perfect, so if you hit one with enough energy it'll melt and start to absorb more of the laser. It gets worse, mirrors don't reflect all frequencies evenly, a silver-coated mirror is brilliant for most of the visual spectrum but just below that it drops to about 50% reflectivity. Metals which aren't as bad at low frequencies don't have as good performance overall. Throw in dirt and damage to the mirrors, which will happen in any operational environment, and mirrors can only make it slightly harder for a laser to destroy a ship. And that's assuming the laser is in the visual spectrum.