Strawberry

1.41 is the average density of the entire sun, the surface's (photosphere) density is 10^-9. Id imagine you'd have the starship mostly in a fairing, with only the areas you'd need exposed exposed. Assuming this fairing is in a airfoil shape a drag coefficent of .05 should be achievable. With the same area, you get 20 thousand pounds of force, not a small amount of force mind you, but considering the first stage of a saturn V put out 7,500,000 pounds of square force, its definitely forces a rocket can handle. For a ksp comparision, the reliant engine puts out twice the force at sea level.

This thread is for things that someone will implement to the game but dont really fit what ksp2 is going for. Personally Id love for there to be a donut planet mod or a flat kerbin mod.

Sorry forgot to specify, used q = mcΔt (specific heat formula), q is the energy transferred in joules, m is the mass, c is the specific heat and Δt is the difference in temperature. Since we know that the energy transferred between both substances is the same, we can set the equations equal to each other and go from there.

There isn't really any direct scientific paper basis for this, researching how to capture gas from the sun will probably get you some odd looks from your colleagues and besides you have better things to do anyways. Fortunately for us however, we dont need a scientific paper to determine if this is possible, with "some" back of the napkin calculations, we should be able to make a pretty decent guess. You'd definitely need to carry cold hydrogen with you, you'd be using the heat transfer to perform work in the form of propelling your ship forward and to cool down the ship. The fact that mixing an equal amount of pure hydrogen will always equalize the temperatures, there's no engineering around this, this is just basic thermodynamics. Fortunately for us however, the sun isn't pure hydrogen. The sun has a specific heat of roughly 12 j/g K, compared to hydrogens 14.304 j/g K. This alone however, is only a ~20% difference however, likely not good enough with this alone. Fortunately for us, we don't need to cool it down all the way, as long as it doesn't melt the tank its in, and the tank is strong enough to handle the extreme pressure that this tank will likely have to save space, then we are golden. While the tank will conduct heat to anything touching it, since we are in space we don't need for it to touch the rest of the ship much, after all we have no gravity and can easily get a vacuum to get rid of most conduction. The question becomes now though, what material works best for the tank. We need a material that has both a high melting point, and a high ultimate tensile stress. Fortunately for us however, we already have a material more then capable of this. Graphene has a melting point of 4500 K and an ultimate tensile strength of 130 Gigapascals1. Lets assume that we want to cool down our gas to 4000k2, doing some back of the napkin calculation3, 4, we get that you need a ratio of 27.7% of cold 20K hydrogen and 72.3% star gunk to get hydrogen at 4000 K. This means that for every gram of hydrogen you use for cooling your collected gas, you get slightly over 2 grams of collected gas back5. You'll have excess gas to still use for cooling and manage to gain more at the end of the day. Keep in mind that these numbers are for our sun, for kerbol you'd get a smaller margin due to the increased temperatures, but considering that red giants have around half the temperature of our sun, they'd be relatively very easy to collect fuel from. 1. While I don't feel like bothering to calculate the maximum pressure this can hold, if someone wants to this walks you through all the equations you need to do in order to do that. 2. I don't feel like doing the math here for whatever the ideal temperature would be 3. This is assuming you're at the surface of the sun, the deeper down into the sun the more efficient cooling gets but also the more drag you'll get. Again someone else can do the math if they want specifics. 4. For the actual calculations here, assuming surface of the sun temperatures (these numbers are slightly off because they dont calculate in the heat added from a ship travelling at mach 10 slamming into it), and hydrogen at 20K, we get a Δt of 1778 for the gas that's being cooled and 3980 for the gas that's getting heated , if we have 1 be the cold gas we already have we know that q1 = m1*14*3980= q2 = m2*12*1778, doing some basic algebra we get 55720m1 = 21336m2, if we have m1 + m2 = 100, doing that thing I hated doing when I took algebra class, we can calculate the percentage of mass you'd need for each. 5. Around 1.5 grams of hydrogen and .5 grams of helium.

Quotations can be used to indicate that a word or phrase isn't meant to be taken literally. I did not mean to misrepresent an already existing thing, only using that term once was a very intentional aspect on my part. I used that word to exist as a primer to explain a concept that unlike bussard ramjets a lot of people here may not be familiar with due to this concept being found mostly in niche internet sci fi. This is a simple and understandable misunderstanding that should be moved past.

I used the term bussard ramjet in quotation initially due to there not really being a word to describe this (just ramjet we tend to think of for producing thrust instead of collecting gas and scoop is a bit vague). I am very much not saying that Bussard ramjets are a term used for scoops for gases from asterial bodies, I am using bussard ramjets as an analog to explain what this thing is, I am not using the term to explain what bussard ramjets are, if you think in any way we were describing bussard ramjets you should reread what we said.

You dont really need to have a heat pump to do this, graphene is a really good thermal conductor and has a very high melting point. If you have graphene with a good thermal insulator underneath, you can easily get the heat to where you want it to go due to graphene transferring the heat where you want it to. Your best bet would be a special graphene coated chamber to where the gas enters, gets heated up here instead of the large tank, and then expelled. You don't need to transfer all of the heat, just enough.

That's why you fly through a less thin part, there's a careful tightrope that has to be walked here, however considering you're likely going very fast and very far you'll inevitably encounter a lot of gas. You'll probably need to fly below the surface of the sun if you want a fair bit of gas, which while difficult is definitely possible. Due to hydrogens high specific heat (in fact the highest unless you get into some truly exotic stuff like storing the heat in fundamental particles like neutrinos or electrons (the more degrees of freedom per mass the better, you do not want to do this, this will mess up your materials if they touch them.)), storing the specific heat in the form of heat sinks probably wouldn't be viable all the way (while you do get a high amount of energy from fusion, you'll have to carry a lot of heat sink mass per hydrogen). Your best bet of dealing with the heat (assuming you don't result to truly exotic stuff like using the heat to store the energy in nuclear/chemical bonds) is expelling it, and ironically enough due to the previous mentioned stuff, hydrogen would be your best fuel here. Transferring this heat to hydrogen and sweating it out (ideally through a thruster) should be more then capable of allowing you to deal with enough heat to where once you get to space you can radiate out the excess in space and turn a profit.

Im not saying, "why wouldnt it" as in, "why wouldnt it be practical to use" Im saying "why wouldnt it" as in "why wouldnt this be an interaction the game has" it doesnt need to be a useful interaction, but it does need to be an interaction because it works like how players would consider it to work (it consumes air spits out resources, so why would some planets with oxygen or other resources that are collectible just refuse to work), and also its a neat little detail that would probably be a one or two line change per planet. The thing about the corona is due to coronal heating, its way hotter then the surface, but also way less dense. There are actually plenty of materials that can exist in the corona of the sun, in fact the parker space probe has already been in the corona of the sun! Of course, that was the outer corona, however 2 million degrees sounds like a lot, but when you realize that its basically a vacuum, its not as hard as one would assume. The confusing thing about the sun is that the wattage output per area is less then that of a reptile. Assuming the sun is actually realistic unlike ksp 1, the main thing is, the big quirk about the sun is the lower you get, the colder it is, however the more dense the gas gets as well. Despite this however, while the sun is very hot, its also very big and very undense. Even when you get to the surface of the sun it's 5778 K (for comparision graphene has a melting point of ~4500k and iirc that was confirmed to be a heat shield option and is also very thermally conductive which actually helps here as it spreads out the heat), however the surface density is only 10^{-9} g/cm^3, by terrestrial standards a vacuum. Of course, when you're travelling at thousands of kilometers a second, this gets dense fast, however again you can just go to higher altitudes if its too much. This is assuming we dont get rid of this heat, which we are very capable of doing, say through using the heat to heat up propellant, however even without this, flying through the sun is surprisingly practical with future tech (which considering that the majority of fuel you'll be collecting is for fusion fuel, this is definitely a late game strategy), especially considering our sun is ~75% hydrogen in mass and ~25% for helium (keep in mind too that lighter elements tend to be closer to the surface).

You dont really need to get "that" close to stars , skimming the corona at very fast speeds will lead to more then enough lightweight gases to do fusion (hydrogen and helium seem to be the two in game) (yes it would still be far more practical to have a specialized vehicle for this, and most players will probably do just this, but that is not nearly as cool). You can always go outwards to get less of the heat of a star. Gas giants though I do see as by far the main application for this, collecting hydrogen and helium. The reason for why this would work on other smaller planets even though it wouldnt be nearly as useful (unless people need to do special trips to collect a fuel as mundane as oxidizer) is because why wouldnt it, once you got the system hard adding this capability to other planets should be trivial, and also I think you could add a lot of nice little details like being able to collect monopropellant from eves atmosphere.

A semi common sci fi trope Ive encountered is civilizations harvesting gases from atmospheres for there spacecrafts, I think this absolutely rocks and is super cool. In order to not only save code work, but also for cleanliness purposes, assuming air serves similar to ksp1 where intake air itself is a resource, really all that needs to be added is some additional air intakes, air tanks (in order for you not to be able to create bootleg RAPIER engines with air tanks just have intake air be converted into compressed air and have jet engines not be able to run on this), and an isru part that refines air (and maybe additional heat shielding to where you can design something like this), with different fuels granted for different atmospheres. This would 1. Encourage high risk high reward aeromanuvering by having increasing rewards for risking your vehicle burning up. 2. Add a way for spaceships to refuel up on fuel without landing on a planet by sending probes down there to collect these gases, 3. Encourage space plane designs even when not planning on exploring planets with atmospheres due to this capability (and spaceplanes are cool) and most importantly 4. Encourage and enable radically different and highly complex vehicle design. Instead of playing it safe why not fly that interstellar vehicle directly into the sun with enough heat shields to make the rage a middle aged women gets when her order is wrong feel like a winters breeze.

While SLAM aircraft sound amazing, I dont want all non off station jet engines to be nuclear hellburners going at several mach, I want there to be "slow" and versatile air breathing engines that work on all atmospheres, without the use of fuel directly. Fortunately, we have that in real life, using electricity to convert air directly into thrust. The most simple are propellers, assuming that there isnt robotics in ksp2, having propellers as preexisting engines as very early game flight tech seems fitting. Honestly you really only need one engine of this type, but a thunderscreech style engine seems amazing. Early game these would be used for early science gathering on kerbin, and for vehicles on laythe and eve (duna presumably has too light of an atmosphere for these engines). For a mid game electric "all air" engine just before you leave kerbin, an ionic wind airplane engine seems good as a highly energy efficient yet slow engine, these should be energy efficient enough to run on solar panels to make "eternal" airplanes (since I assume the way different types of procedural wings that have different materials work for things like heat shields is by having them all be the same part with a setting you can love with, an option for solar wings seems cool mostly for this engine). Finally, for your late game electric you have plasma aircraft engines. This is an incredibly niche technology that has yet to taken off (both literally and figuratively). These work by using microwaves to ionize gas. With current technology, these engines can achieve similar thrust density to jet engines (the gas is really hot though so its a bit out of reach under current engineering designs). These would serve as both highly energy efficient (though energy intensive) and fast electric engines, capable of acting in any atmosphere (maybe have a ramjet style one that can work in thin atmospheres at very fast speeds, or just have a single plasma thruster with all those niches) with high efficiencies and no need for fuel. Plasma aircraft engines could also easily serve as an advanced RAPIER engine which can use any fuel (no need to carefully manage ratios of oxygen and jet fuel anymore!) and can air breath, however at the cost of electricity consumption.

Arcjet thrusters, these are a pretty niche technology, however they make electric arcs through there propellant (hydrazine is the main one) and expel it which I think slaps. Gameplay wise these would serve as an early game rocket filling the niche of a micro ion engine, useful for microdrones and maybe later on you get to use these things as really energy efficient but slow rcs thrusters, for things like long distance travel where turn rate doesnt matter much.