in game realism

[galactictaco]

is it possible to orbit at 40km (with fuel assist) to mirror the orbit of the ISS? this always bothered me, if KSP is 1/10th the scale, our orbits and speeds never mirrored real orbits and i always forgave it because i don't know jack about real orbital mechanics and maybe speed doesn't scale the same way so ok, our speeds aren't 1/10th real orbital speeds, but our baseline orbital height is 70km, almost twice as high as the space station. so it got me wondering, could a SSTO maintain a 40 something km orbit in a similar way to the ISS (occasionally speeding up every orbit or something right?) or is it still too much drag? i got an orbit or 2 with an apoapsis of 60 km, but 40km seems worrying low. the secondary question is, assuming its not possible, why not? is the KSP atmosphere more like an earth atmosphere in size and this threw it off? the way 10km is similar atmospheric density to earths 10km zone? still it begs the question why 40kms isn't enough to allow orbit tho.....

[Tyko]

Because it's not the SOL system. it's a completely different solar system. There are a lot of similarities between Kerbin and Earth, but Kerbin isn't just a 1/10th scale Earth.

To answer your question about a 40km "orbit". Anywhere below 50km a craft encounters serious atmospheric drag. At 40km you're really "flying", nor "orbiting"

Edited December 20, 2016 by Tyko

[regex]

Honestly, just install RO if you want realism. You'll run yourself in logic circles trying to make sense of KSP's toy solar system.

Edited December 20, 2016 by regex

[Nathair]

6 minutes ago, regex said:

Honestly, just install RO if you want realism.

Is RO working with 1.2.2?

[regex]

25 minutes ago, Nathair said:

Is RO working with 1.2.2?

No, but it is working with 1.1.3.

Edited December 20, 2016 by regex

[Sharpy]

1 hour ago, galactictaco said:

is it possible to orbit at 40km (with fuel assist) to mirror the orbit of the ISS?

ISS orbit is 400km, not 40 though!

[regex]

Just now, Sharpy said:

ISS orbit is 400km, not 40 though!

But the point being that 40 is 1/10th of 400 amirite? Better to base it off atmosphere height, or the Karman line, maybe, so the Kerbin ISS sits at 7/10 of 400km, or 280km.

[Snark]

Yes, but not only doesn't Kerbin's atmosphere have 1/10 the height of Earth's... it shouldn't, at least not unless it's made out of some freakishly dense exotic gases very different from nitrogen and oxygen.

Atmosphere pressure scales with height according to gravity, temperature, and atmospheric molar mass.  Kerbin has the same gravity as Earth, and approximately the same temperature, so it stands to reason that its pressure-versus-altitude profile would be pretty similar (i.e. not 1/10 scale).

Of course, since it's an imaginary solar system, they could have made the scale height 1/10 that of Earth (i.e. just posit that the atmosphere is really dense too, same as the planets) ... except if they did that, you'd be down to barely 1% atmosphere at an altitude of only a couple of kilometers, which wouldn't be a very natural game experience.

So the real reason that Kerbin's atmosphere height is comparable to Earth's and not a whole lot smaller is presumably due to playability.

[regex]

Let's face it, trying to compare anything in KSP to real life, aside from some basic physics laws that allow us to create a real solar system through mods, is a moot point. It's a toy solar system that makes zero sense. Seriously, just make up whatever justification you need to put your Kerbin ISS wherever it needs to be.

[crapstar]

KSP is 1/6th the size of real solar system.

[Jarin]

1 hour ago, regex said:

Let's face it, trying to compare anything in KSP to real life, aside from some basic physics laws that allow us to create a real solar system through mods, is a moot point. It's a toy solar system that makes zero sense. Seriously, just make up whatever justification you need to put your Kerbin ISS wherever it needs to be.

You can keep repeating this if you like, but there's quite a bit of internal logic to the design choices Squad made. Snark covered just a few. Sure, it's not all perfect, and plenty of sacrifices are made for gameplay, but you're not giving it nearly enough credit. 

[regex]

44 minutes ago, Jarin said:

You can keep repeating this if you like

Thanks, I will, because it's true.

Quote

plenty of sacrifices are made for gameplay

Yes, we know. This is why it's best to just make up your own justifications for where to place your Kerbal ISS "replica" in orbit instead of trying to make it mesh with real life.

Edited December 20, 2016 by regex

[Corw]

Regex being Regex after all these years, colour me shocked

 

galactictaco, Kerbin is not Earth. Kerbin is also not 1/10 model of the Earth. Kerbin is Kerbin, so place your station where it fits in Kerbin ruleset.

[diomedea]

Actually, Kerbin's atmosphere is almost right, the pressure scales pretty close to what would result by applying the Scale Height equation (the pressure curve is "only" about 0.902 times what would result from applying the ScaleHeight result in a barometric formula, with the same gravity, molar mass and temperatures). That, considering also the different geopotential height resulting from a gravity corrected by a very different centrifugal force than on Earth. The most striking difference is actually with the "cut" at 70 Km for Kerbin, a realistic atmosphere would still show effects at much higher altitude.

Playability certainly took its share with other bodies however. Eve's gravity and molar mass are such that realistic ScaleHeight would average 7778 m at sea level, instead the pressure curve "fits" a value of 17113 m (2.2 times) to make a sizable density with altitude. Realistically, Eve's atmosphere would be compressed in the very first KM of altitude leaving close to nothing at 90 Km (where the "cut" occurs). The opposite stands for Duna, a realistic ScaleHeight would be = 4703 m, the curve fits with a value of 2352 (~ 0.5 times).

Sorry if I'm sparing the process that brings to those values, it's quite complex to show.

[Wallygator]

8 hours ago, regex said:

amirite?

Didn't I study this element in 1st year chemistry?

Sadly there is no element 'Ro'.  But in a fantasy universe it would definatly lie somewhere outside of  K(19), S(19), and P(15).  I expect it would be an as yet unrealised heavy element with a weight of around 130.

[Wallygator]

6 hours ago, Snark said:

playability

@Snark - i'm not responding to / or disagreeing with your post, only a single word that sparked a thought 

Playability depends (in my opinion) on two things: 1) the game and 2) the player.

Give a strictly chess player a game of backgammon and they will likely say is not a playable game for them because of the luck factor.

Granted, not every game is designed for every player.

Still, When someone promotes a game with 'reality' (1/1) based physics along with a core tenet of a "non-reality" (1/10) based environment then it is totally fair for threads like this to pop up.

The only strategy left for players that are sympathetic to reality is for them to 'roll play' - or install mods (still with roll play required otherwise you actually need to go into space for real!)

[memes in space]

12 hours ago, regex said:

KSP's toy solar system.

Relevant video:

EDIT:

Speaking of RO: The tanks and engines didn't fit together last time I played. Could someone explain what even happened?

Edited December 20, 2016 by memes in space

[Jarin]

*snip* Arguments have long since been made and minds aren't going to be changed. There's plenty of ways to enjoy the game, so I'm leaving it alone.

Edited December 20, 2016 by Jarin

[Gianni1122]

@galactictaco

To simplify an answer to your question... Not sure why this hasn't been said yet...

The ISS' orbit averages around 400km; about 240km above the minimum for low earth orbit (~160km)

Using the same logic, 310km above kerbin would be a comparable altitude for an ISS replica to orbit in game.

EDIT: I.e., Kerbins minimum orbit is 70km. Earths is 160km. Adding 240km=ISS 400km/Replica 310km

Edited December 20, 2016 by Gianni1122

[Starman4308]

Which parameters to match is highly arbitrary, and for the most part, I'd agree with @regex in that it's moderately futile to directly map real solar system ideas onto the toy-scale stock system; I'd just go with "a smidge above Kerbin atmospheric boundary".

However, choosing an arbitrary pair of parameters, I would insist on periapsis of 4,175,551m above surface and apoapsis of 4,182,110m above surface. This will match the ISS's orbital period of 92.65 minutes and its eccentricity of 0.000686. I'm sure you will all 100% agree with me that you cannot have an ISS replica without a period of 92.65 minutes and eccentricity of 0.000686.

[Guest]

14 hours ago, Gianni1122 said:

@galactictaco

To simplify an answer to your question... Not sure why this hasn't been said yet...

The ISS' orbit averages around 400km; about 240km above the minimum for low earth orbit (~160km)

Using the same logic, 310km above kerbin would be a comparable altitude for an ISS replica to orbit in game.

EDIT: I.e., Kerbins minimum orbit is 70km. Earths is 160km. Adding 240km=ISS 400km/Replica 310km

I think it's better to do it by percentage so the height actually scales.

160 + 150% = 400km over Earth

70 + 150% = 175km over Kerbin

 

[Gianni1122]

On 12/21/2016 at 1:16 AM, String Witch said:

I think it's better to do it by percentage so the height actually scales

Even better

[wumpus]

On 12/19/2016 at 10:18 PM, Snark said:

Yes, but not only doesn't Kerbin's atmosphere have 1/10 the height of Earth's... it shouldn't, at least not unless it's made out of some freakishly dense exotic gases very different from nitrogen and oxygen.

You mean like a souposphere?  If you happen to have KSP .9 or so lying around you could try that.  Just be warned that the souposphere has weird alchemical properties such that aerodynamics depends on individual parts and not the whole.

Just kidding, the souposphere was one of the least realistic bit of early KSP (although likely an important hack that made it at all possible and lasted way longer than it should have.  Not to mention had its own brand of mad science fun).  Don't go there if you want realism (although you could probably play with the density constants and make Kerbin more like Eve).  If you want realism, you pretty much need Realism Overhaul in its entirety, KSP had to make a lot of changes to get Kerbin to work, it takes an equal amount to make Earth work.

[Snark]

19 minutes ago, wumpus said:

the souposphere was one of the least realistic bit of early KSP

Agreed.  Was really happy when it went away.

19 minutes ago, wumpus said:

lasted way longer than it should have

That's a harder call.  "Should have" is a tricky thing.

Longer than it should have, from a player's perspective?  Absolutely.  Any time greater than zero would be longer than it should have. 

However, longer than it should have, from a software developer's perspective?  That's hard to say, unless you are, 1. a software developer yourself, and 2. a developer on this project.

I'm a developer, but don't work for Squad, so I meet #1 but not #2.  So I can't make any authoritative pronouncements about exactly why Squad did this or that, in what order, but I can speak to how software development works in general.

Software development is a zero-sum game.  You only have a certain finite amount of resources to produce the software with:  people, time, money.  And there's always more stuff to do than you have people, time, and money to do it with.  Always.  Working on one thing means not working on something else.  This means that there's always some dearly-desired feature that has to get cut, or delayed, because something else more important had to come first.

And deciding how to prioritize that sort of thing is a tricky balancing act.  You have to take into account not just how important the feature is (i.e. "how bad is it if we don't have this?"), but also how expensive the feature is (i.e. "how much time and money is it going to take to produce?")  It's all about bang for the buck.  Sometimes it's actually best to defer a very-important but very-expensive feature, if it means you can slip in a whole bunch of much cheaper features in the meantime.

I think we all agree that "better aero" was a really, really important feature.  But it's also a really, really expensive one.  Lots of code to write, lots of testing to do, lots of fertile ground for bugs.

Yes, as a KSP player, I agree that the Souposphere Era went on for a lot longer than I would have liked it to.  On the other hand... during that era, I also got a lot of features that I love about this game.  More part variety.  Science.  Career mode.  Contracts.  Biomes.  Tweakables.  Subassemblies.  Asteroids.  Lots of fine-tuning of game physics other than aero, such as joints.  Difficulty options.  And so forth.

If Squad had made the decision to go for improved aero back around, say, 0.22 instead of in 1.0, they would have to give up a lot of that stuff, or at least defer it until much later.  A lot.  And I gotta say... if KSP had had super-realistic aero back when I joined, but missed out on all that other stuff?  I probably would have gotten bored with it and wandered away.  After all, I'm a rocket guy rather than a spaceplane guy, and the vast majority of my interactions with the game happen in a vacuum anyway, so the suboptimal aero, while annoying, was tolerable for a game that was very much a WIP.

Of course, the interesting question there is, suppose they'd done that (gone for better aero sooner), just how much of that other stuff would have had to been delayed, and for how long?

Well, unless you work for Squad, there's simply no way to know.  But I think it's safe to say that they're not idiots, and they do have a clue about how to do their jobs, so if it were actually a slam-dunk that "aero should come sooner", that's what they would have done.  It may or may not have been a "mistake" (hey, nobody's perfect), but it's unlikely to have been a seriously egregious one.

TL;DR:  anyone who doesn't work for Squad is not in a position to say whether they made the right choice or not, because you don't have any visibility into the relative costs involved.

[wumpus]

4 minutes ago, Snark said:

[lots of words]

This is all true, but I can't help but think there was plenty of support for the souposphere in the community and Squad.  While there might have been other ragequit posts over the years, the ones I remember were from the changes in stability from .9 ->1.0, which was not something to be taken lightly.  So while a good part of the issue was just how hard it was to write (and presumably Farram not willing to give FAR away) [although wasn't there something called "NEAR"?  Were they that hard to write if there were competing aero fixes?], another part was the inevitable unwillingness to break legacy systems.

And so the souposphere lumbered on.