Is it better to close air intakes?

[juvilado]

Hi, im not sure if we need to close air intakes once the jets arent breathing, is it worth?

[fourfa]

Nope. It's a vestigial feature from long ago. There is zero difference in drag open or closed

[GoSlash27]

juvilado,

 It doesn't improve your aerodynamics in KSP 1.1.3 to close the intakes, so I usually leave them open.
OTOH... it doesn't hurt anything to close them....

Best,
-Slashy

[David104]

Why have the intakes this option then? Is there another use?

[Val]

9 minutes ago, David104 said:

Why have the intakes this option then? Is there another use?

Because it used to make a difference and some day it will again, probably.

And yes, @juvilado. It is better to close your intakes. It means you can scoff at anyone who doesn't 

[Jaeleth]

13 hours ago, Val said:

Because it used to make a difference and some day it will again, probably.

And yes, @juvilado. It is better to close your intakes. It means you can scoff at anyone who doesn't 

 

How come a nica and realistic feature was scraped like that?

Are they working with FAR installed? I am asking this because I am yet to change to 1.1.3 since it will take me a lot of time to convert my rovers to go around the many bugs brought on by this new version regarding the dreaded wheels.

[Alshain]

It's a left over feature that simply hasn't been removed yet.

1 hour ago, Jaeleth said:

 

How come a nica and realistic feature was scraped like that?

Because it isn't all the nice or realistic.  It's actually meaningless.  Why would you close your air intakes in the atmosphere?   That is when you use them.  Why would you close them out of the atmosphere?  They can't cause drag there.  Even on the old system in the high atmosphere they made little effect at all.

Edited September 10, 2016 by Alshain

[Val]

10 hours ago, Jaeleth said:

How come a nice and realistic feature was scraped like that?

I think, it happened when the aerodynamic model was updated in 1.0.

And just to be clear. The open/close of intakes does have a function. It does exactly what it says.

It's the difference in aerodynamic drag, between open and closed, that was lost.

Which is why it no longer helps to close the intakes to reduce drag when they are no longer needed.

Edit: If I remember correctly, in the previous aerodynamic model drag was basically an arbitrary number set by the part designer, that was constant no matter which way the part faced.

The current aerodynamic model has drag based roughly on the part's shape and which way it is facing into the oncoming air.

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Are they working with FAR installed?

I don't know.

[Jaeleth]

On 10 September 2016 at 11:29 PM, Alshain said:

It's a left over feature that simply hasn't been removed yet.

Because it isn't all the nice or realistic.  It's actually meaningless.  Why would you close your air intakes in the atmosphere?   That is when you use them.  Why would you close them out of the atmosphere?  They can't cause drag there.  Even on the old system in the high atmosphere they made little effect at all.

It is, actually, meaningful and critical:

 

(Note: "Atmosphere" is comprised of Troposphere, Stratosphere, Mesoshpere, Thermosphere, Exosphere, which fades, gradually into vacum, which never is, actually, absolute. It does not ends all of a sudden, although it does have separation layers between these I mentioned, relatively thin (called the xxxxxpauses) which, still, are continum, not abrupt). The ISS, space shuttle and foreseeable space planes with hybrid engines, for instance, orbit in the thermosphere, "space", the Karman line, is considered, nowdays, to be 100km high, some 50km above the beginning of thermosphere). In an hybrid engine you will switch to closed cycle way before "space" is reached.

 

 

1. In the ascent phase, there will be a point when the air is thinner than the necessary to produce thrust, you switch to closed cycle (rocket), but the intakes will still produce some drag, you optimize it by closing them. And I am not even considering the problems of hypersonic air hitting the blades of the turbine... We will see to it next...

 

2. In the reentry phase is ABSOLUTELY critical to close the intakes... It would be the death sentence of a reentry vehicle to enter Earth's surface at mach 29 with an open intake. How would you coat the blades? How would you solve the problem of hypersonic air hitting them at mach 10+, I am already assuming air speed is reduced to subsonic before hitting the blades as normal in supersonic / hypersonic aircraft. 

 

3. In game terms why would you want excess drag ascending, even if little, or lots of excess drag when descending, when you no longer have any fuel left to use the turbines?

 

in short... A nice and realistic feature... Gone

 

Edited September 12, 2016 by Jaeleth
Expand information

[Sharpy]

There's also the matter of how to meaningfully close some intakes.

Look at most jet planes. In fighters, they are closed after landing, to protect the engines and air ducts from dust, birds and pests. In heavy transport/airliners the intakes are closed with big flaps of tarp if the plane is to sit on the runway for a couple weeks. In flight? One might close the intakes, causing the engine to stall, and significantly increasing the drag, as the air instead of passing through the intake and engine, ends up trapped in the shallow pits the intakes now form. There are very few real airplanes where the intake valves closing cause any aerodynamic gain.

In KSP? The stack-mounted and the radial adjustable ramp intakes are built in a way where closing them might make sense. But how do you imagine physically building a closing mechanism for the circular intake, the shock cone, the XM-G60 radial intake, or the engine nacelle in such a way as to reduce drag instead of increasing it?

[Sereneti]

To close the intakes, it was usefull (*a little bit) a long time ago

The engines dosnt flame out by seed/high, they flame out by "to less air".

If you closed the intakes, you saved some air for the engines, - a little more dv.


 

[Jaeleth]

41 minutes ago, Sharpy said:

There's also the matter of how to meaningfully close some intakes.

Look at most jet planes. In fighters, they are closed after landing, to protect the engines and air ducts from dust, birds and pests. In heavy transport/airliners the intakes are closed with big flaps of tarp if the plane is to sit on the runway for a couple weeks. In flight? One might close the intakes, causing the engine to stall, and significantly increasing the drag, as the air instead of passing through the intake and engine, ends up trapped in the shallow pits the intakes now form. There are very few real airplanes where the intake valves closing cause any aerodynamic gain.

In KSP? The stack-mounted and the radial adjustable ramp intakes are built in a way where closing them might make sense. But how do you imagine physically building a closing mechanism for the circular intake, the shock cone, the XM-G60 radial intake, or the engine nacelle in such a way as to reduce drag instead of increasing it?

What you are referring to is not closing the intakes (at least in a usefull aerodinamic sense). What we do in real aircraft when parked at the apron or hangar is to put intake covers, radiator covers, pitot tube cover in place. Often a bit of foam covered in leather, usually painted in red, with a "remove before flight" sticker attached to it.

The purpose of this is to avoid bugs, birds to get inside and even make nests in those orifices, in case of the jets also to protect the sensitive turbine blades from damage.

The discussion here is how to close the intakes, aerodinamically, in flight. I know of no aircraft who does this since there are not yet operable hybrid engine aircraft, althout there are, at least, 2 hybrid engines under testing, the british SABRE and a russian engine. But, to be effective, the intake doors would have to be an extension of the fuselage and engines must be mounted in such a way that, during reentry, would be protected from the shock wave, probably at rear, above (and protected by) the wings.

So, in game terms, this last approach is the one we should be talking about. It has not yet been done, but it is close future, like many features on this game. It is not necessary, in game terms, to imagine the engineering of such an intake, just to admit that it is there and it makes a difference.

 

Edited September 12, 2016 by Jaeleth

[Sharpy]

4 minutes ago, Jaeleth said:

What you are referring to is not closing the intakes (at least in a usefull aerodinamic sense). What we do in real aircraft when parked at the apron or hangar is to put intake covers, radiator covers, pitot tube cover in place. Often a bit of foam covered in leather, usually painted in red, with a "remove before flight" sticker attached to it.

There are some airplanes with these built in.

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I know of no aircraft who does this

AFAIK, a few VTOL close the intakes that are close to the ground, leaving the 'roof' ones open; Harrier being a prime example. That's to prevent sucking dust and other crap inside - but at these speeds, the aerodynamics loss is negligible.

The gist here is that the models of intakes we have in KSP shouldn't be closable at all, with exception of the two I had mentioned. They can't be closed in a way that would reduce the drag, and the option to reduce drag by closing the circular intake was a fantasy by early developers of KSP, that was quite reasonably (but not thoroughly enough) scrapped.

[Alshain]

4 hours ago, Jaeleth said:

It is, actually, meaningful and critical:

<snip>

 

None of that explains how it is meaningful in KSP.  The answer is, it isn't.

[Jaeleth]

2 hours ago, Alshain said:

None of that explains how it is meaningful in KSP.  The answer is, it isn't.

 

If it increases realism, it is, by itself, meaningfull in KSP. KSP is not an ordinary "game", it is, or at least it is supposed to be, a space flight simulator, and as any simulator it should simulate reality as best as it can. If it can't, it can't, but removing a feature that was already implemented and contributed to realism, not good policy.

 

Why having all those types of engines then? One single "super engine" like a rhino with a NERV isp, dual cycle, and weighting 1t would do the job... But hey... It's not realistic, right? Are all of them "meaningfull" to KSP? As meaningfull as closing the intakes... They add realism... Because if it's just about orbital mechanics a single type of engine would do the job...

 

And, in terms of KSP (game only) if I can reduce drag when climbing or in a powerless glide with no fuel, back to KSP, I definitely want to, and it is definitely meaningful...

 

Edited September 12, 2016 by Jaeleth

[Alshain]

28 minutes ago, Jaeleth said:

If it increases realism, it is, by itself, meaningfull in KSP.

Incorrect. Gameplay trumps realism.  If it can be somewhat realistic while maintaining good gameplay, then that is great, however good gameplay is more important.

28 minutes ago, Jaeleth said:

SP is not an ordinary "game", it is, or at least it is supposed to be, a space flight simulator

Incorrect.  The creator of KSP never wanted a simulator, he always said it was a game first not a simulator.

28 minutes ago, Jaeleth said:

If it can't, it can't, but removing a feature that was already implemented and contributed to realism, not good policy.

Incorrect.  It wasn't removed outright, it was rendered ineffective by changes to the way engines function.  Changes that were very good for gameplay. (and keep in mind when I say 'made ineffective', that went from barely effective, closing the intakes was never in the history of KSP very effective at reducing drag)

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Why having all those types of engines then? One single "super engine" like a rhino with a NERV isp, dual cycle, and weighting 1t would do the job... But hey... It's not realistic, right?

Incorrect, it's not good gameplay.  That is the reason.  The fact that it makes it more realistic is just a secondary benefit.

Edited September 12, 2016 by Alshain

[severedsolo]

@Jaeleth Can you actually point me to an aircraft that can close it's intakes for aerodynamic efficiency? I did a bit of digging earlier, but so far have not come up with a single example. A google search for "close air intake planes" mainly brings up KSP results.

The closest I can find is several mentions of supersonic jets using their inlets to "divert" the majority of the fast moving air (I'll admit my knowledge of this is a bit shaky though)

[Corona688]

On 9/10/2016 at 2:42 PM, Jaeleth said:

How come a nica and realistic feature was scraped like that?

They didn't decide "oh hey, let's break this nice feature people are using and twiddle our evil mustaches, mua hah hah hah hah".  They ripped out the old aero model.  They redid aerodynamics from the ground-up.  Intakes and air-breathing engines and the atmosphere itself changed fundamentally.

In some ways the old intake model was more complete, but it had nasty unintended side-effects -- like 2-engine flameouts sending you into a hyper speed death spin.  Now dual engines flameout simultaneously, without you having to manually choke them.  This is a good thing in a game where you might not be able to afford action groups yet.

I'm not sure intake closing will return or not.  It was almost necessary in the old model, but isn't as useful anymore.

Edited September 12, 2016 by Corona688

[Jaeleth]

18 hours ago, severedsolo said:

@Jaeleth Can you actually point me to an aircraft that can close it's intakes for aerodynamic efficiency? I did a bit of digging earlier, but so far have not come up with a single example. A google search for "close air intake planes" mainly brings up KSP results.

The closest I can find is several mentions of supersonic jets using their inlets to "divert" the majority of the fast moving air (I'll admit my knowledge of this is a bit shaky though)

No there isn't, I just mentioned that it in my previous post. No jets doing that, the only hybrid engines in testing haven't yet a fully working aircraft (read: spaceplane) to be assembled on. When they do, they'll have to find a workaround for closing them and/or diverting the flow of hypersonic air from them (blades). Unless they use a statoreactor at some point, but there must be a turbine somewhere for working at lower speeds.

And yes, supersonic air cannot hit the turbine blades, that's why the design of supersonic jet engines is much more complicated, the faster they go, the harder it gets to do this.

 

Correction: Another forum member pointed me out some VTOL examples, actual planes that close intakes, although not exactly for the same reasons we were discussing it here, it is a good example.

Edited September 13, 2016 by Jaeleth

[Jaeleth]

4 hours ago, Alshain said:

Incorrect. Gameplay trumps realism.  If it can be somewhat realistic while maintaining good gameplay, then that is great, however good gameplay is more important.

Incorrect... In a simulator realism prevails, that's why it's called a... "simulator". Anyway... I can't see the point, closing intakes never bothered me, lol... Speaking of gameplay, infinite loading screen times and crashes every 4 or 5 screen loads, in a bad day, DO BOTHER me!!! But hey... I can live with that, if I wanted simply a game I'd be playing EVE online, here, I come for science and simulation! With some fun to it, of course... 

 

 

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Incorrect.  The creator of KSP never wanted a simulator, he always said it was a game first not a simulator.

Well... Have you never heard the creation, often, overtakes the creator? That happened with Dungeons and Dragons, now that I remember old times...

If it was a game first, the lasers, starfleets and empire building system are missing... And why did the upgrades (and many mods available) so far, increase realism (improving of reentry and drag models, for instance) and did not add blasters and star destroyers?

KSP is an outstanding simulator and a good teacher of what is flying in space. Keep it that way! Making it "just a game" puts it head to toe with the likes of Eve Online, or Stellaris, just to name a few, do you really want to do that?

Let it be good at what it is: science and simulation, with a fun side to it, that makes it cool learning, do not try to force it into something it wasn't born to be, or else it will loose...

 

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Incorrect.  It wasn't removed outright, it was rendered ineffective by changes to the way engines function.  Changes that were very good for gameplay. (and keep in mind when I say 'made ineffective', that went from barely effective, closing the intakes was never in the history of KSP very effective at reducing drag)

Well... That's an acceptable explanation. So, I will rephrase... They should add it back whenever possible, together with more damage to parts exposed to shockwave in reentry and not coated in ablative material.

 

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Incorrect, it's not good gameplay.  That is the reason.  The fact that it makes it more realistic is just a secondary benefit.

Incorrect approach... It should be: "As realistic as possible without compromising gameplay (particularly frame speed) or, at least, let the users decide how realistic it gets"

 

As for gameplay there are other... Issues... Which should be addressed much more urgently. For instance, the dreaded wheels that got completely messed up with the new unity engine. Now they are neither realistic, neither playable... But we have patience, for a unique simulator, that we wouldn't... For a simple game.

Edited September 12, 2016 by Jaeleth

[Alshain]

12 minutes ago, Jaeleth said:

Incorrect... In a simulator realism prevails, that's why it's called a... "simulator". Anyway... I can't see the point, closing intakes never bothered me, lol... Speaking of gameplay, infinite loading screen times and crashes every 4 or 5 screen loads, in a bad day, DO BOTHER me!!! But hey... I can live with that, if I wanted simply a game I'd be playing EVE online, here, I come for science and simulation! With some fun to it, of course... 

It's not called a "simulator".  So....? Yeah Gameplay above realism as I said.

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Well... Have you never heard the creation, often, overtakes the creator? That happened with Dungeons and Dragons, now that I remember old times...

Certainly hasn't happened with KSP.

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If it was a game first, the lasers, starfleets and empire building system are missing... And why did the upgrades (and many mods available) so far, increase realism (improving of reentry and drag models, for instance) and did not add blasters and star destroyers?

Why would you assume a game has to have all that?  Not all games have lasers and empires.  This is a tycoon style game.  Hint: RollerCoaster Tycoon isn't a simulator either.

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KSP is an outstanding simulator and a good teacher of what is flying in space. Keep it that way! Making it "just a game" puts it head to toe with the likes of Eve Online, or Stellaris, just to name a few, do you really want to do that?

 No it's not.  You might learn the basics, but there is a lot it doesn't teach.

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Let it be good at what it is: science and simulation, with a fun side to it, that makes it cool learning, do not try to force it into something it wasn't born to be, or else it will loose...

Let it be good at what it is, a tycoon game.

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Well... That's an acceptable explanation. So, I will rephrase... They should add it back as soon as possible, together with more damage to parts exposed to shockwave in reentry and not coated in ablative material.

I disagree, they should just remove that tweakable option.

 

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Incorrect approach... It should be: "As realistic as possible without compromising gameplay (particularly frame speed) or, at least, let the users decide how realistic it gets"

Incorrect or not, it's what KSP is.  Don't like it?  Orbiter is a simulator.  I highly recommend it if you want a simulator.

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As for gameplay there are other... Issues... Which should be addressed much more urgently. For instance, the dreaded wheels that got completely messed up with the new unity engine. Now they are neither realistic, neither playable... But we have patience, for a unique simulator, that we wouldn't... For a simple game.

Wheels are being fixed in 1.2.  I'm not sure what justification you are using for assuming people are more patient for a unique simulator than they are for a unique game like KSP.

Edited September 12, 2016 by Alshain

[Jaeleth]

3 hours ago, Corona688 said:

They didn't decide "oh hey, let's break this nice feature people are using and twiddle our evil mustaches, mua hah hah hah hah".  They ripped out the old aero model.  They redid aerodynamics from the ground-up.  Intakes and air-breathing engines and the atmosphere itself changed fundamentally.

In some ways the old intake model was more complete, but it had nasty unintended side-effects -- like 2-engine flameouts sending you into a hyper speed death spin.  Now dual engines flameout simultaneously, without you having to manually choke them.  This is a good thing in a game where you might not be able to afford action groups yet.

I'm not sure intake closing will return or not.  It was almost necessary in the old model, but isn't as useful anymore.

I liked the assimetric flameout of the engines... It forced you to be on your toes when flying the aircraft, which was at it should be. And you could easily avert that by switching off both engines before starving the engine out of air...

 

what do you mean by not afford action groups yet? Action groups are in place since a long time now.

Edited September 12, 2016 by Jaeleth

[fourfa]

@Jaeleth in career mode, you have to purchase upgrades to the VAB and SPH in order to have access to action groups.  This costs money you have to earn with missions; on harder difficulty settings, these can be outlandishly expensive.

[Jaeleth]

1 minute ago, fourfa said:

@Jaeleth in career mode, you have to purchase upgrades to the VAB and SPH in order to have access to action groups.  This costs money you have to earn with missions; on harder difficulty settings, these can be outlandishly expensive.

Ok then I remember this now... It was so long ago I started my career I didn't remember this any longer  but still... If I still remember, one also has to be pretty far up the career ladder to start building space planes (the only craft where we have this problem) so, maybe, by that time you already have the action groups anyway, maybe.

[fourfa]

Disagree - even with the default Hard settings, it's likely that you will have the tech tree completely filled long before finishing upgrading the facilities.  And increasing financial pressure with difficulty settings pushes you into 100% recoverable craft earlier, not later.