OhioBob

Yeah, there's no need to modify the curves if you like the way it behaves with atmosphere = 1.25. The 0.8 factor came from Squad when they released KSP 1.0. That's when they completely redid the drag and atmosphere models. Prior to that atmospheres assumed a constant scale height. They ended when the atmospheric pressure dropped to some percentage of the sea level value. Kerbin's atmosphere ended up being somewhere around 70 km. With the release of KSP 1.0, Kerbin's atmosphere was now modeled on the U.S. Standard Atmosphere, which goes to a height of 86 km. I'm pretty sure the decision to factor the model by 0.8 was just to keep the atmosphere at about the same height it had been in the beta version, i.e. 86 x 0.8 = 68.8 km rounded off to 70 km. I use that same factor for all my atmospheres to be consistent with the Kerbin model.

Unfortunately it is not as simple as just giving you the scale heights because the scale heights are not constant. Each atmosphere was given a temperature-height profile, a surface pressure, and molar mass. The pressure-height curve was then computed from gas laws using numerical integration. If you want to know all the details, you can read about it here: However, you really don't need to concern yourself with all that. My method for a producing realistic atmospheres is to size up the KSP body to life-sized proportions (10x radius, 100x mass), develop an atmospheric model to fit the characteristics of the life-sized body, and then scale the atmosphere down to a height more appropriate for KSP. The height factor that I use is 0.8 (this is because stock Kerbin is based on 0.8 times Earth's standard atmosphere). So what you are trying to do is just reverse the process that I already went through. To reverse the 0.8 factor, you want to have Sigma Dimensions use an atmosphere factor of 1.25. This will make my atmospheric models perfectly suited for bodies resized by a factor of 10. However, you may need to add another step. The upper atmospheres in stock-sized KSP are designed for spacecraft entering at velocities much slower than real life. At Kerbin or Gael you might hit the atmosphere going 3.5 km/s, while at 10x you'll be entering at 11 km/s. At that speed you may find that it's like hitting a sudden wall of air. You may want to extrapolate my pressure curves farther out to provide a deeper atmosphere so that the heat and pressure builds up more gradually. Below is Gael's pressure curve: pressureCurve { key = 0 101.325 0 -0.0150837 key = 1000 87.2020 -0.0132081 -0.0132081 key = 3000 63.9899 -0.0101333 -0.0101333 key = 6000 38.9849 -0.00673315 -0.00673315 key = 9000 22.6271 -0.00429191 -0.00429191 key = 12000 12.5591 -0.00253586 -0.00253586 key = 15000 6.81764 -0.00138393 -0.00138393 key = 20000 2.54022 -0.000487144 -0.000487144 key = 25000 0.998086 -0.000181456 -0.000181456 key = 30000 0.412750 -7.07098E-05 -7.07098E-05 key = 35000 0.180048 -2.89531E-05 -2.89531E-05 key = 40000 0.0818694 -1.27710E-05 -1.27710E-05 key = 45000 0.0370931 -6.02348E-06 -6.02348E-06 key = 50000 0.0159849 -2.79241E-06 -2.79241E-06 key = 55000 0.00644408 -1.21769E-06 -1.21769E-06 key = 60000 0.00242266 -4.88645E-07 -4.88645E-07 key = 63000 0.00131259 -2.70937E-07 -2.70937E-07 key = 70000 0 0 0 } From 0 to 63000 meters the atmospheric pressure decreases naturally with increasing height. It is only the last part, from 63000 to 70000 meters, that the pressure is forced to taper off to zero. What you may want to do is add more keys above 63000 and take the atmosphere out to whatever height you want to make it. I don't know what the right answer is, but let's say we push the upper edge out 20% to 84000 meters. And let's add one key between 63000 and 84000, say at 75000 meters. You can estimate the pressure at 75000 by extrapolating from the given data. You'll probably end up with something that looks this: pressureCurve { ... key = 63000 0.00131259 -2.70937E-07 -2.70937E-07 key = 75000 0.0001 -2E-08 -2E-08 key = 84000 0 0 0 } Recall now that these altitudes are going to factored by 1.25, so the above atmosphere will end at a height of 84000 x 1.25 = 105,000 meters. You may have to experiment to find the atmosphere height that provides the behavior that you're looking for. If you do this, be sure to also extrapolate temperatureCurve and temperatureSunMultCurve, which also end at 70000 meters, out to the new height. Also change the attitude parameter. The example here was for Gael, but the steps will be the same for the other bodies.

Good to know. That just happens to be the surface pressure of Hadrian's new atmosphere.

We took your suggestion and gave Hadrain liquid nitrogen oceans. Between its lower albedo and a thicker atmosphere, I was able to warm it up from 58 K to 65 K.

I thought so as well, but Catullus and the Gauss system was already interesting enough. The Otho system needed something to spice it up. It is only half about being scientifically accurate. Making the game fun to play by providing some interesting places to go is just as, and maybe more, important. Hadrain is below the freezing point of nitrogen, so that's why I figured a thinner atmosphere.

A low orbit plane change to a zero inclination orbit takes about 340 m/s. I don't know if you noticed, but it's possible to get to Ceti with very little plane change. The launch site is at 8.5 degrees latitude, and Ceti's orbit is inclined 9 degrees. So if you time the launch correctly, a due east launch will put you almost into Ceti's orbital plane. A 1/2 degree tweak only take 20 m/s.

I wish it were possible to create mountain lakes.

Wow, I had no idea there were plateaus that high. At 9 km we're already 20% of the way to orbit, and the atmospheric pressure at that height is only 0.4 atm. Still got the high gravity to deal with, but otherwise it should be a snap to launch from there. Right. I saw several of areas that looked like they were 2+ km high and reasonably flat, but they were all pretty small.

I tested out launching from Tellumo yesterday. From sea level it is practically impossible with stock engines. The only engine that produces any appreciable thrust at 10 atm pressure is the Aerospike. But its TWR is so low that all it can do is lift itself and a small fuel tank. It has virtually no payload capacity at all. However, Tellumo's atmospheric pressure decreases so quickly as we ascend that if you can launch from higher terrain it's really not too bad. I slapped together a two-stage liquid fueled rocket and got to orbit from a starting altitude of 2000 meters with surprising ease. It took less than 6000 m/s delta-v. The trick is finding a high flat spot that's large enough to hit when you come in to land.

Those travel times are for a Hohmann transfer orbit. It's possible to reduce the flight time, but the faster the transfer, the more delta-v it will take. It becomes a trade-off.

Niven's solar constant is about 1.8 times Earth. That makes sense.

My calculations gave me a molecular weight of 20 for the lightest gas that Niven can retain. But that is only a ballpark estimate. I used a root-mean-square speed that's 10% of the escape velocity.

It's borderline at best. The locations where I placed the lakes is where the surface temperature ranges between the freezing and boiling points of water. Unfortunately I figured the boiling point at 0.1 atm pressure, which means the atmosphere would be 100% water vapor. (Is that right?) I probably ought to compute it for a pressure of something like 0.005 or 0.01 atm (5%-10% water).

OK, that will give me plenty of time to study it to see if we can keep any of the lakes or if they all need to go. My gut feeling is that any lakes that can remain might be too small to bother with. I'll let you know. I'm sure I made the same mistake when I figured the methane lakes on Augustus. Augustus has enough atmospheric pressure though that I think at least some of the lakes can probably stay.

Yeah, I think you might be right. I computed it based on the total atmospheric pressure and not the partial pressure of water. There may still be a narrow band of latitude where water can exist, but I need to study it closer. @Galileo, sorry but it looks like I goofed. How hard would it be to take out the lakes? Do you still have the old textures from before we added them?

Oh, I think I understand your question now. Were you asking if it were really possible for lakes to exist on Niven? The answer is yes. I actually performed a fairly detailed study of surface pressure, temperature, and boiling points. I was able to identify specific latitudes and elevations at which liquid water could exist. That's where we placed the lakes.

I'm afraid I don't understand the question. I don't know what "situation" you are talking about.

Surface gravity appears in the scale height equation, H = (R × T) / (M × go) Here go is the surface gravity of your planet, not standard earth gravity (9.80665 m/s2) as is used in some other equations. As far as determining the maximum height of an atmosphere, there is a section in my tutorial that explains this. See the section with the bold heading "Ending an Atmosphere." Admittedly I may have over complicated my method for finding the upper edge of an atmosphere. Surely there are simpler ways of doing it, but my method works even if it's not the easiest.

Realistic Atmospheres is nothing but revised temperature and pressure curves. I don't think there is anything that I can do that would help Trajectories make better use of that data to make better predictions. I probably should start a conversation with the maker of Trajectories to see if we can figure it out.

When I first set Eta's orbital parameters, I unwittingly placed it in an elliptical orbit that sometimes took it outside Thalia's SOI. Although Eta orbited Thalia OK, whenever the moon moved outside the SOI, any spacecraft in orbit around it would just drift away and go into a solar orbit. To fix the problem I had to decrease Eta's size and move it closer to Thalia.

As JadeofMaar explained, the black numbers above the line are the maximum plane change. The numbers on the line represents the Δv for a simple Hohmann transfer with zero plane change. In practice you could never achieve this unless the launch window had absolutely ideal conditions. The plane change value is the Δv it would take to perform a mid-course plane change when 90-degrees from intercept (see image below). The maximum plane change angle is equal to the planet's inclination. Yes, it is. Thalia has a really small sphere-of-influence, and Eta is barely inside it. By the time we insert into an elliptical orbit with an apoapsis inside the SOI, we're practically already in an orbit that will intercept Eta. It just takes a very tiny tweak to lower the apoapsis to intercept Eta.

The formula is, P = ρRT where P is pressure, ρ is density, R is the specific gas constant, and T is temperature. The specific gas constant is the universal gas constant divided by the molar weight, i.e. R = 8.3144621 / M. In your example we're given only 2 of 4 variables, so we can't solve it without more information. However, we can find the relationship between pressure and temperature. P = 2.6238 * (8.3144621 / 0.05908684) * T P = 369.21 T So if you define either temperature or pressure, we can compute the other. (edit) In the Pandora example I had 3 of 4 variables - P, ρ, and R.

I'm not familiar with "rescaled atmospheres", is that a mod? If you are referring to using Sigma Dimensions to rescale the height of the atmosphere, then yes, it will work.

The pressure of Duna's atmosphere at the surface is the same as it is in stock (1/15 atmosphere). The main purpose of this mod is to make sure that atmospheres vary with increasing height in a realistic way, not to change the surface conditions. For that reason I didn't turn Duna into Mars (Duna's surface pressure is about 11 times greater than Mars'). The biggest difference between this mod and stock is that Duna's atmospheric pressure decreases with increasing height at a much lower rate than it does in stock. Therefore, at high altitudes this mod's atmosphere is definitely denser than stock Duna. That's just the way it would be in real life for a planet Duna's size with it's given surface conditions. The planet's low gravity causes its atmosphere to expand and fade more slowly than it would for a larger planet. Despite the fact that Duna's air is much thinner at the surface, it is actually denser than Kerbin air at altitudes above about 22 km.

I'd still prefer to see some of those numbers rounded off (as per our private message), but other than that I like the way it looks. I'm not sure what to put in there for the "low orbit <> planet" value for the gas giants. Obviously we can't land, so it doesn't really make much sense to compute an ascent Δv. Pretty much any descent into the atmosphere of a gas giant is going to be one-way, so I'm leaning toward just putting in the amount of Δv required to produce a safe deorbit and atmospheric entry. For Nero this might only be about 50 m/s or so (it doesn't take much just to drop the periapsis down into the atmosphere).