NichG

I have been doing it and reporting the results so far. But nothing that can make it to orbit, for the reasons I gave.

You can easily lift a NERVA and tank with an ion glider on Eve. Where 'easily' means '20 minutes in game time to ascend 1km'. With Eve's atmosphere, you can glide just fine even with a TWR of 0.02. That's not the problem. The problem is that once you get up to altitude you won't get any horizontal speed of note. Which means that even where the ISP is close to 800 you're going to need a TWR greater than 1 with the NERVA. Which means you need something like 3-4 NERVAs to a single one of the long 1.5m tanks. Which is no good. The maximum single-stage delta-v you can get while still maintaining Eve TWR>1 is actually much higher for the tiny probe engines than for the NERVAs, taking into account engine mass - its somewhere in the vicinity of 4km/sec.

I like maneuver nodes... but I'll admit, I also like thinking about how one might navigate by dead reckoning without any sort of trajectory prediction, and whether there are rules of thumb one can use to figure things out. So I've managed to get to the Mun without looking at map mode at all before (using about 8km/sec of delta-v from launch due to messing it up quite a bit). Roughly speaking, what it looks like is that the Mun starts a bit ahead of you, then falls back (you're going around your orbit faster than it is at that point), and then appears to 'catch up' from behind as you reach apoapsis. I've tried to use this idea for interplanetary trips, but even if you wait for a launch window and keep track of how much delta-v you use up to get the burns close, the accuracy needed is a bit too large to pull it off with a single shot. Instead I think the best bet is the 'get the apoapsis right, keep periapsis a bit tighter in, and wait to catch up' method - of course this means several decades of going around Kerbin. I tried unsuccessfully with Duna, but Jool is probably easier since it has a huge SOI.

At that point I'd say just have them use the Unity engine with specifically configured physical scenarios. In KSP, if you're in space you aren't going to generally be in an inertial reference frame, which means that things like Newton's Laws, gravitational acceleration, and kinetic energy end up getting complicated by the effective forces from the non-inertial frame.

So messing around with Hyperedit, I've confirmed that the following at least is theoretically possible - an 'atmosphere dipper' that drops down to 30km and ~1km/sec, and then makes it back to a sub-orbital flight that leaves the atmosphere for about 4 minutes. The NERVAs aren't actually great for this because you still need a good TWR in order to actually make it up from the layers where atmospheric drag is killing your velocity. I was only able to recover to about 50km altitude with the NERVAs, but with the 48-7S engines I was about to get an apoapsis of about 140km. The design I ended up with was two FL-T800 tanks, six of the 48-7S engines in a VTOL configuration, and eight of the swept wings inclined at a 45 degree angle from prograde. The gimmick is that you can point prograde and thrust vertically, but still get significant lift from the wings due to your 1km/sec residual speed. So in principle, if you could ion-glide up to 30km, and if during the ion glider phase you could attain a horizontal speed of around 1km/sec, and if on top of that you had another craft intercept on a sub-orbital flight to capture the ship as it left the atmosphere, then you could actually make this work. The big problem is getting the ion glider phase to give you a 1km/sec horizontal speed in that part of the atmosphere - I can't see any way to pull that off. There might be a more efficient engine combo, or maybe you can get away with using more wings or something, but its looking somewhat unlikely that this will be possible even with an ion glider.

My tests with ion gliders suggest you might be able to get them up to 20km or so before they can't climb further, but it'd be painfully slow (and the fact you can't drop the empty xenon containers would really hurt your rocket performace). Also, you're going at something like 70m/s at best at 20km, so you're going to need a rocket with Eve TWR significantly greater than 1 to actually get into orbit (air resistance there means you won't get significant vertical assistance from horizontal speed). What I mean by painfully slow is, it took about 2 in-game hours to get to 5km altitude.

That is going to be pretty hard to beat with an ion glider . My first test attempts took about 2 in-game hours to get to 6km from sea level, with an Eve TWR of 0.02. Ascending at 3 degrees with an airspeed of 12m/s is painful. On top of that I'm sure I'll need to add more mass for the rocket ascent stage once you get above the pea soup part of the atmosphere since it only had something like 3km/s once the ions run out of xenon.

With KSP Interstellar, its relatively easy using an upgraded plasma thruster and lots and lots of beamed power. An antimatter spaceplane will also do the trick fairly easily. Also probably a small ship using a DT Vista. For the stock challenge, a rocket-assisted, massless-battery-pack ion glider seems like it'd be worth trying though. Suggested scoring system: minimal time to orbit for an SSTO, each extra stage costs you 20 minutes.

Delta-v calculation might be a reasonable thing to do, though atmospheric effects/variable ISP for Kerbin launches mean that there are extra fudge factors to add on top which aren't so good for educational purposes. Maybe use staging/a prepared game file and only have them calculate it for the second stage once it's already in orbit? Calculations of the delta-v requirement for apoapsis/periapsis adjustment might be reasonable. You could also do something with looking at how the orbital period depends on the various orbital parameters, and check that it follows Kepler's Laws. Given that a highschool physics lab is generally going to be 45 minutes to an hour and a half in length, you'd want to make sure that the students don't waste too much time on e.g. failed launches and things like that. From launch to orbit in KSP is generally about 5 minutes if everything goes well, but kraken attacks, bad TWR, things like that may mean you have to try that a couple of times before it works (certainly if you're new to the game), so I'd guess that for the lab itself you'll burn 20 minutes teaching the basics of how to use the game interface, 30-40 minutes getting them to figure out how to get into orbit, etc, and then you can actually start doing things which have simple calculations. I'd start with Kepler's Laws, go over them in a class before the lab, spend 10 minutes at the start of the lab reviewing them, and have them set up a series of different orbits and measure them in game. Maybe something like: - Get your craft as close as you can to a 100km x 100km orbit. Write down the apoapsis and periapsis from in-game here. Wait for your ship to go around (using time acceleration) and measure the orbital period. - Put your craft into a 100km x 400km orbit. Write down the actual apoapsis and periapsis here. What is the semi-major axis of this orbit? Measure the orbital period. - Put your craft into an inclined orbit. Write down apoapsis, periapsis, inclination, and semi-major axis. Measure the orbital period. - Put your craft into two more orbits of your choice, write down the orbital parameters, and measure the orbital period. - Now we will see if these results follow Kepler's Third Law. Compute the ratio T^2/r^3 for each of these orbits. Using the gravitational constant G, estimate the mass of Kerbin. Compare with the values from the in-game dialog. To make it more fair (especially if the lab is being marked), it'd be reasonable to provide a save state with a craft with ample delta-V or infinite fuel cheats enabled sitting in Kerbin orbit, but part of the fun would be designing your own experimental craft and getting it up there yourself so I'd have that as a fallback option if people are having trouble - maybe check on everyone at the 50 minute mark and if they aren't in orbit yet, switch them to the save file.

It seems like the smallest compounds of abundant things are either solid or gaseous at the relevant temperatures. It'd be interesting to e.g. search a chemical database for all compounds of C,H,O,N,Si,S, Fe, Mg, (Ne, He - yeah right) containing no more than 5 atoms, to see if any of them would actually be liquid in the conditions on Eve's surface (water would be, just barely). I've been poking around a bit in searchable databases, but I haven't found something that quite lets me specify that particular search yet. I'm curious what the distribution of melting and boiling temperatures (at 5atm or 1atm or whatever) would look like, and if there'd be some obvious gaps or structure; it might let one make a sort of HR-diagram-equivalent for planetary oceans (e.g. if you plot temperature and pressure, plausible oceans only form over certain regions of the entire diagram). How about Cyanamide? It decomposes at 260C, but at Eve surface conditions the boiling point is pretty close to 150C. It's also a somewhat smaller molecule than other proposals so far, so abundance-wise it's probably more reasonable. Producing it looks hard though - requires 2000C processes industrially. Sulfuric acid could work too (bp of ~300C) I guess.

Yeah, mostly I suggest the biomass thing because it's pretty evocative. A secondary reason is, whatever you have oceans of, you need some process pervasive and thorough enough to produce oceans of that material at the surface (either through generating it within the planet and then migrating it preferentially to the surface, or generating it at the surface, or having it come in via impact events). For large hydrocarbons its kind of a delicate balance to get them via chemical equilibrium, since at high temperatures its preferable to have many smaller molecules rather than one big one (pressure goes the opposite way, which is what's going on with diamond), but at low temperatures its hard to get over the energy barrier to form covalent bonds. Maybe something like a 'cold' (e.g. significantly less than 500C), high-radiation environment would be ideal for that kind of process? E.g. something that creates a lot of chemically active things that can drive condensation reactions, but which doesn't create an environment where cracking of large hydrocarbons occurs naturally. This kind of chemistry is getting far outside of my realm of comfortable speculation though.

Water wouldn't work at -50C though, even at 5atm. But if its never that cold on the ground then that changes a lot. At that point, it could be pretty much anything whose 1atm boiling point is somewhere around/above 110C I think, since the boiling point vs pressure adds from 40-90C to the boiling point going from 1atm to 5atm for the usual small molecule culprits (e.g. things with a small enthalpy of vaporization). For the more tightly-bound options (8-carbon stuff, liquid metals, things that form highly charged ions, etc) you get to add about 30C to the boiling point, so you'd want to look around 130C for those. Water is interesting because its just barely at the boiling point at 5atm (152C). That would suggest that the temperature and pressure at the surface of Eve would be very strongly buffered if it had water oceans, because not only is the heat capacity of the water resisting temperature variation but it also boils off as needed (resisting both pressure variation and also adding the enthalpy of vaporization to the energy budget to resist a temperature change). So this might mean that the day-night cycle would be very muted as far as temperature swings. I guess the other possible thing to look at would be temperature at the poles versus temperature at the equator, and the distribution of ocean over the surface. It seems like I'm going to need to send a number of probes now (unless due to biomes for Eve not being in yet, the temperature readings are the same everywhere on the surface?) Edit: Surface temperature of Eve in game is 150C regardless of time of day or location I think; at least, a sample at the equator and at 70S both gave the same result.

So I decided to look for non-extreme things Eve's oceans could be made of that are actually consistent with the surface temperature range (-50C to 150C) and pressure (5atm). A few random shots in the dark and I found a possible contender: Toluene boils at something like 160C at 5atm, and melts at -95C. So the question would be, what natural processes might produce toluene oceans? Its basically carbon, hydrogen, and a tiny bit of oxygen, but its a fairly large molecule compared to the usual ocean-forming stuff (methane, ammonia, etc). Wikipedia says it forms at some fraction in crude oil, so perhaps Eve was once a lush world covered with biomass, which then got broken down due to high temperatures in a runaway greenhouse process and slowly degraded into a number of large organic molecules, out of which leaked all the stuff which happened to be liquid over the entire range of Eve's day-night cycle. The stuff that straddles the cycle (and there's a lot of it) would form some sort of very complex daily pattern of evaporation and condensation that I don't really know how to think about. I guess it would probably end up creating density bands in the atmosphere, staying just high enough that the local pressure means that it remains in vapor phase, like you'd get in fractional distillation. Alternately, it might create mid-atmosphere rain storms where something hits a combination of temperature and pressure sufficient to condense high in the atmosphere and then rains down to an area of the atmosphere where it reverts to vapor phase as the temperature increases. Anyone have a handy dandy atmosphere calculator we can put the components of crude oil into and see what we get?