Atmospheric entry heating?

[chuckie001]

So, when I am flying from space down to a planet's surface, there are these atmospheric entry effects (basically the front of my ship burning), and as I'm decelerating, they keep occurring down to the speed of about 170u (whatever “u” means).

But then, when I'm flying low over the surface, I sometimes even exceed that speed (to about 180u), and no heating occurs. But I'm flying at a higher speed, and in at least as dense -- if not denser -- part of the atmosphere as before. Why no effects? Any physicist that can explain?

[Aries the Grinning]

You cratt is entering an atmosphere froma vacuume, that creates friction (basically your hull is hitting more particles) which creates the heating you see (just check re-entry vids of space shuttles to see the real life equivalent)... once you're in the atmosphere you'll not see it again as basically you've adapted to it, though there is still heat being generated it isn't as bad as the initial entry shock... Think of how a jet plane usually doesn't propel itself as a ball of fire when it hits Mach speeds or above (provided it wasn't exploding, of course xD)

[chuckie001]

Actually, reading about it on Wiki, I've learned that even jet planes experience this, but in lower intensity (since they're not flying at Mach 20, but much slower). See https://en.wikipedia.org/wiki/Concorde#Heating_problems or https://en.wikipedia.org/wiki/Sprint_(missile) . So it really should depend on the current speed and air density, there's no additional "adaptation" of a craft.

[Maverick]

Interesting. Didn't expect that much realism from a game like this.

[chuckie001]

Well, looking into it, it seems quite unrealistic, if you consider the info linked from Wiki, or even games like Kerbal Space Program. I'm wondering whether it might be some sort of that “special atmosphere physics and chemistry” that was mentioned in some of the developer interviews.

[Maverick]

170u is something like 170kph. I think when you're coming in from space, you're going really fast, thousands of u.

[chuckie001]

Well with thousands of kph, that could be realistic, but if you look at the game, it's completely different. Just try it yourself, or look at this video:

https://www.youtube.com/watch?v=h0WtN6cyYLU

• 0:46, speed at 114u, burning.
  
• 1:09, speed at 174u, burning.
  
• 1:10, speed at 174u, no effects, all of a sudden.
  
• 1:14, speed at 152u, burning again.
  
• 1:26, speed at 103u, no effects.
  
• 1:28, speed at 98u, burning again.

How am I supposed to make any sense of that?

[Maverick]

Originally posted by chuckie001:

How am I supposed to make any sense of that?

Looks like it's just a trigger or something, based on height, angle or speed maybe. Maybe they were going for what Aries was saying, idk the science of it. Maybe he knows.

[Von Pink]

Originally posted by chuckie001:

Well with thousands of kph, that could be realistic, but if you look at the game, it's completely different. Just try it yourself, or look at this video:

https://www.youtube.com/watch?v=h0WtN6cyYLU

• 0:46, speed at 114u, burning.
  
• 1:09, speed at 174u, burning.
  
• 1:10, speed at 174u, no effects, all of a sudden.
  
• 1:14, speed at 152u, burning again.
  
• 1:26, speed at 103u, no effects.
  
• 1:28, speed at 98u, burning again.

How am I supposed to make any sense of that?

it's just an animation that gets applied when above a certain angle on re-entry. there's no physics or anything being calculated.

[chuckie001]

Originally posted by Von Pink:

it's just an animation that gets applied when above a certain angle on re-entry. there's no physics or anything being calculated.

Hmm, now that you mention it, it does look like it only depends on the angle, yes... But wouldn't that be a really stupid programming decision, when literally all you'd have to do to make it realistic would be to switch the formula from “angle > 50 degrees” to “speed > 200 u”?

[Von Pink]

Originally posted by chuckie001:

Originally posted by Von Pink:

it's just an animation that gets applied when above a certain angle on re-entry. there's no physics or anything being calculated.

Hmm, now that you mention it, it does look like it only depends on the angle, yes... But wouldn't that be a really stupid programming decision, when literally all you'd have to do to make it realistic would be to switch the formula from “angle > 50 degrees” to “speed > 200 u”?

can't really comment on their thinking as to why they did it the way they did it, but it certainly does make more sense to have the animation triggered by speed than angle. maybe they didn't think of it.

[boxman]

Originally posted by Aries the Everdying:

You cratt is entering an atmosphere froma vacuume, that creates friction (basically your hull is hitting more particles) which creates the heating you see (just check re-entry vids of space shuttles to see the real life equivalent)... once you're in the atmosphere you'll not see it again as basically you've adapted to it, though there is still heat being generated it isn't as bad as the initial entry shock... Think of how a jet plane usually doesn't propel itself as a ball of fire when it hits Mach speeds or above (provided it wasn't exploding, of course xD)

But that is all because of the friction caused by the speed you are reentering at. If he is going at same speed above surface, then the effects should be stronger. This is just another unrealistic aspect of the game.

[Red Eagle LXIX]

The atmospheric entry effect appear to me to be based on Speed+height+angle, and are only active for ships only (note you can jetpack to space (unlimited fuel cheat), re-enter atmosphere, and allow yourself to plummet to the planet without seeing the effect).
With Low flight you'll notice this height trigger sometimes as you fly over mountains and valleys, as you cross over a mountain and pass the valley if you stay the mountain's height for a bit (rather then hug the terrain after cresting), then try slowly lowering to the valley.

[morph113]

Since neither the planets nor the height of the atmosphere are anywhere in relation to real planets they stuck with a simplified model. Because if you would would have reentry speed 10x faster than your low atmospheric flying speed, then you would hit the terrain in 1 second because of the wrong planet size and atmosphere height proportions. As you might have noticed, NMS is pretty much unrealistic in almost every regard when it comes to real science.

Now I don't mind myself since I get my realism kicks out of Elite Dangerous or KSP. But just so you aren't wondering why there are no orbits, the distances between planets are way off, flora and fauna surviving 300 degrees or minus 100 degrees. How a moon could possibly have a high atmosphere and lush life and the planet it "orbits" is barren.

There is mistakes around every corner but they aren't there because the devs didn't know any better but because the game is a rather casual arcade space game and it works in my opinion. At least I'm not really bothered by all those things. From a gameplay perspective it works.

[Mike]

I honestly don't know why people are bothered by things like this since it is not supposed to be a space or flight simulator, but here is a possible explanation that might satisfy those who are bothered by it.

When you enter the atmosphere from space, you are going very fast and it makes your heat shield very hot, and it doesn't start cooling down until you get under 170. If you are merely travelling in the atmosphere at say 200, you don't get the heat effect because that is not fast enough to generate the heat. The heat you see on re-entry was generated at a higher speed, and just didn't dissipate until you got down to 170 or so. How's that?

[Red Eagle LXIX]

Originally posted by Mike:

I honestly don't know why people are bothered by things like this since it is not supposed to be a space or flight simulator, but here is a possible explanation that might satisfy those who are bothered by it.

When you enter the atmosphere from space, you are going very fast and it makes your heat shield very hot, and it doesn't start cooling down until you get under 170. If you are merely travelling in the atmosphere at say 200, you don't get the heat effect because that is not fast enough to generate the heat. The heat you see on re-entry was generated at a higher speed, and just didn't dissipate until you got down to 170 or so. How's that?

Fine except when I am already in atmosphere traveling 170, fly over a mountain, then descend to the valley on the other side and get the heat effect.