jebbe

I believe experimental physicists are by now down to a few hundred attoseconds: http://en.wikipedia.org/wiki/Ultrashort_pulse

Not exactly a paradox, but: #define true false

There's already a very similar challenge, somebody went to Duna and back: http://forum.kerbalspaceprogram.com/threads/52043-The-Tech-Level-1-Orbital-Challenge?p=687458&viewfull=1#post687458 My entry - mun and back: http://forum.kerbalspaceprogram.com/threads/52043-The-Tech-Level-1-Orbital-Challenge?p=686870&viewfull=1#post686870 Edit: Ninja'd...

This was fun! After around twenty attempts and never less than 100m I got lucky:

Oh right! I got so caught up in doing things old style, that I completely forgot about that option! So, back to the drawing board!

Pretty awesome! Although - are you sure you are not using fuel lines?

This is awesome, feels just like the old times! Mun and back: http://imgur.com/a/zuMOa#0 ----- Achieve a stable Low Kerbin Orbit (Periapsis 70km+) with one Kerbal: +20 points - forgot the screenshot in the final attempt that made it though... Achieve a stable High Kerbin Orbit (Periapsis 100km+) with one Kerbal: Nope, Pe was below 80 all the time, on Kerbin as well as on the Mun Achieve either orbit with two or more Kerbals: No again, just one, although I did carry six empty pods to LKO. Successful reentry to Kerbin atmosphere: +5 points Pilot(s) survives return journey: +10 points Rocket is completely undamaged after landing: I actually exploded almost all of it, it's called "staging"! Total: 35 points Additional awards: Mk1 Decoupler (External Combustion Engine) - Excessively! Extra-Vehicular Propulsion - Jeb tried on a previous attempt, but it wasn't enough to return to Kerbin. He's stranded now. The BobNova Award for Gallantry in the face of Common Sense - Is the Mun's sphere of influence outside of Kerbin's SOI?

Wixhausium. Because Europium, Germanium, Hassium, Darmstadtium - what has to be next? Of course! (GSI) Edit: Darmstadtium = Bowel-city-ium, Wixhausium = Masturbation-town-ium. Towns have great names here!

A simple way to do something similar at home is to use a CD and a laser pointer. Point the laser to the data side of the CD and watch the reflection pattern. Careful - only look from the front side of the CD, such that the laser points roughly in your direction (not into your eyes!), with the CD in front of you. Project the reflection pattern e.g. to a white wall. A CD is basically a fine refelctive grid rather than a single/double slit, so all the reflection patterns from all the "slits" overlay and give you very distinct maxima, and wide minima. A CD works better than a DVD (let alone a bluray), because the coarser the grid, the closer the maxima. And modern technology produces such fine grids, that the maxima can be really far apart.

Hm ok, true, if you consider the dry mass of the fuel tanks. Yeah, I guess that's how it should be done.

Sorry, but I have to disagree: delta-v is proportional to the logarithm of your initial fuel, and the logarithm doesn't converge - it grows very slowly, but it never reaches a limit.

Actually, there is no limit: To increase your delta-v linearly you need exponentially more fuel. Or, in other words: Increasing your mass linearly only increases your delta-v logarithmically, but you will always get some additional delta-v, without any upper bound. You just need more and more fuel for less and less delta-v, which is probably what you have noticed. So there's only the practical limit of how large a rocket you can design without it getting unstable, or your computer lagging too much. However, I have built rockets with more than 30km/s delta-v, well capable of doing a grand tour, and there's a neat trick to it: Make your spacecraft as lightweight as possible, ideally it's just a probe core with a minimalistic propulsion system (tiny fuel tank and ant engine / ion propulsion system). The gain from small decreases in the spaceships mass is enormous, try to get rid of everything you don't absolutely need; for example put ASAS and RCS to lower stages and dump them before activating your leightweight spaceship, or even better, don't take them along at all. Actually, if you could make your ship infinitely light, then you would get infinite delta-v. All this is just inferred from the rocket equation; try to understand it, it will help a lot with building rockets.

I have browsed through the optimal ascent thread again, and dug out this: The optimal TWR is 2+2*a/g, where a is your current acceleration, and g is the accelaration due to gravity. This will actually increase from two to something like 5 for most designs during the first tens of kilometers of the ascent. Afterwards you are basically out of the atmosphere, and these considerations do not matter any more - as said before, for the orbital insertion you should try to stick with light-weight, high-efficiency engines.

In this thread we had an extensive discussion about optimal ascent profiles. Bottom line: If you are aiming for fuel efficiency, you should stay close to terminal velocity (as stated before), and that is achieved by a TWR of roughly 2:1 in the beginning. However, while fuel drains, the TWR increases, and fortunately that is exactly what you need to keep up with the terminal velocity. For the orbital insertion you want to use a TWR as low as possible (light, high efficiency engines) - just high enough that you get into orbit without burning away from the prograde vector too much.

I'm actually very sceptical about our ability to communicate with alien species. Let's stay on Earth: There are intelligent beings down here on Earth, with complex communication patterns, able to communicate over geat distances, and we have no idea what they could possibly be "talking" about: dolphins and whales. These guys might be just as smart as we are, they grew up in an environment very close to ours, they are even mammals just like us, and yet we do not understand them at all. So how would we ever get around to communicate with somebody that has evolved in a completely different chemical environment?

Hey Leon - this time it's not the moderators who clean after our mess, I'll do it instead!

I like to think of it this way: The total energy of the system rocket+fuel+exhaust has to be conserved (basic physics, conservation of energy). Now if you dump your fuel somewhere near a planet, your exhaust gas has a very small potential energy, because it's deep inside the gravity well. Therefore, you must get a lot of kinetic energy for the rocket. On the other hand, burning far away from a planet leaves your exhaust gas with quite some potential energy, which you in return will not have available for your vessel. This is also why we usually use delta-v to measure a rockets performance and not energy: delta-v is constant, but the kinetic energy you can get out of this delta-v depends on where you burn.

64. Can we have a sperm whale and a bowl of petunias to smash into planets?

xkcd has thought about just that - it's a great read: http://what-if.xkcd.com/30/ Short answer: Yes, it's possible, but much harder than on Earth. You have to be very fast, with all the complications that brings. Has anyone tried on Duna?

Yummie .

Nope, first equation is wrong already - see my earlier post: Thrust = (fuel rate in L/s) * density * g * Isp so you get Isp = Thrust / ((fuel rate in L/s) * density * g) where density = (Mfuel/Vfuel). Plugged in you have Isp = Thrust * Vfuel / ((fuel rate in L/s) * Mfuel * g)

There has been a challenge that resulted in quite sophisticated physical models for the Kerbal universe; some of the results found their way into MechJeb. It covers what you were asking for in great depth, including several numerical codes to solve the equations: http://kerbalspaceprogram.com/forum/showthread.php/6664-Mini-challenge-max-altitude-with-this-supplied-spacecraft In there we had a lot of references to this thread about drag - unfortunately, the links don't work anymore in the new Forum, so here you go: http://kerbalspaceprogram.com/forum/showthread.php/5235-Atmospheric-drag The problem with this is not computational power; all you'd have to do is add a number for each celestial body. The issue is the prediction of the trajectories, which are useful in itself, but become essential for time warp: For the patched conics, there are analytical solutions you can apply, while with the n-body problem you'd have to run a complete numerical simulation over the whole trajectory at each frame to keep the trajectories up to date. And that is not an option even if you had a super computer.

Yep, that sounds right: The 20.4 is basically 1000 / ( g * fuel_density ). The 1000 comes in because you are using kN instead of N.

As far as I know, the original definition of the specific impulse is the velocity of the exhaust, given in m/s. Think about firing a gun: the higher the velocity of the bullet, the higher the recoil, or, in our case, the thrust you get out of a given mass of fuel. Now, Americans don't like metric units, so in order to make the specific impulse globally comparable, the rocket scientists did something arbitrary: They divided the specific impulse by the gravitational acceleration g, and got a specific impulse that is now measured in seconds (for which one can also come up with some physical meaning as Harvester showed above). Of course, this only makes sense at the Earth's surface, because g is not a universal constant. But they don't care, they always divide by g, no matter if the rocket is on the Earth's surface or somewhere in outer space. Now, assuming that the Kerbals have made the same choice to scale with g as we here on Earth, we can extract the density of their fuel from the equation stated by Tamerlane: Thrust = (fuel rate in kg/s) * g * Isp which we can convert to Thrust = (fuel rate in L/s) * density * g * Isp or density = Thrust / ((fuel rate in L/s) * g * Isp) = 60,000N / ( 1.5L/s * 10m/s^2 * 800s ) = 60,000kg*m/s^2 / ( 1.5L/s * 10m/s^2 * 800s ) = 5 kg/L which is five times the density of water. That's a lot, but given the huge density of Kerbin itself, I have no trouble believing that they're able to find some very dense combustibles on their planet. edit: Would be interesting to check if this is consistent with the rest of the game - firstly of course, the other engines (which it should if ISP is supposed to be meaningful), but also densities taken from the specifications of the fuel tanks. Also, what about SRB's?