Intakes

[jarmund]

Alright, I need loads of air, and i want my craft to look at least partially realistic, so no intakes inside intakes inside other parts.

From what I've understood, shock cone is the best stacked intake, so i always use that in front of tanks, engines, nose, etc. But which will give me the most air attached radially, compared to the drag it produces?

Bear in mind that i'm flying with FAR (or trying to, at least), so I'm assuming big parts such as the basoon thing will cause a lot of drag.

Edited March 17, 2015 by jarmund

[Taki117]

You shouldn't need a whole lot of air. I sue a couple Ram intakes, and a couple of small structural intakes, and that should be plenty. What is the problem you are experiencing?

[jarmund]

No problem in particular, I'm just lousy at flying. I just want to make sure that my turbojets last as long as they can.

Edited March 16, 2015 by jarmund

[GoSlash27]

jarmund,

The XM-G50 is the best radial- mount intake. The Ram air intake is the best stack mount intake.

http://forum.kerbalspaceprogram.com/threads/106114-Stock-KSP-90-intake-comparo-for-SSTO-turbojets

As taki said, you don't actually need a whole lot of intakes to achieve acceptable performance so long as you design and fly it correctly.

I'm running 4 xm-G50s on an 18 tonne single engine transport and my engine stays lit long enough to get me completely out of the atmosphere.

The less mass you're pushing, the less intakes you need.

Best,

-Slashy

[Starwhip]

Oh, you're using Ferram Aerospace?

I was going to suggest this:

Darn.

[Mister Dilsby]

I don't use FAR myself, but I find that a shock cone plus a pair of "bassoons" (and I do love that imagery you used) is enough to bring a single turbojet up to a reasonable departure altitude. For unreasonable altitude and I think a not too unrealistic look, here is the Kerbojump:

That's three shock cones and four bassoons feeding a single turbojet. Max altitude on jets is about 34km.

You (and FAR) will have to decide whether this sort of layout is shenanigans or not. My personal rule is simply no stacking, every intake has to be unobstructed.

ETA: Looking at @Slashy's research, I may just replace the outboard intakes with rams and see how much higher I can go

Edited March 16, 2015 by Mister Dilsby

[GoSlash27]

Derp!

Nevermind my last.

I missed the part where you said you were running FAR.

Apologies,

-Slashy

[Taki117]

No problem in particular, I'm just lousy at flying. I just want to make sure that my turbojets last as long as they can.

With FAR they will only last up to about Mach 3, regardless of altitude.

[jarmund]

With FAR they will only last up to about Mach 3, regardless of altitude.

Alright, so if I understood you correctly speed becomes an issue before thin atmosphere with FAR? So, if i can reach mach 3, then i have enough air?

----

Related question, when looking at this table: http://wiki.kerbalspaceprogram.com/wiki/Parts#Air_Intakes

How do i read this to figure out which intake is best for the various uses? How do i prioritize between intake area and the intake air initial/max? (Still primarily for FAR, but on a more general level too, i guess).

Also, with FAR, am i right to assume that the larger ones cause more drag, regardless of the 0.2 drag common to all of them?

Edited March 17, 2015 by jarmund

[Renegrade]

With FAR they will only last up to about Mach 3, regardless of altitude.

FAR's TurboJet nerfs reduce it's zero-thrust point to 1800m/s (vs 2400 for stock) - I whipped up a test craft, and was able to attain about Mach 4.7@35km.

How do i read this to figure out which intake is best for the various uses? How do i prioritize between intake area and the intake air initial/max? (Still primarily for FAR, but on a more general level too, i guess).

The intake area is the only stat that really matters there. The initial/max stuff is just how much IntakeAir can be stored - that's basically just leftover IntakeAir after the engines have been fed.

Also, with FAR, am i right to assume that the larger ones cause more drag, regardless of the 0.2 drag common to all of them?

You can determine the drag involved in FAR empirically fairly easily. Just place a plane to be tested on the runway, accelerate it up to a small, nonzero speed, and then multiply the Cd by the reference area for each design. That's your baseline drag for the whole craft. If you repeat those tests with different configurations, you can figure out which intakes have the least drag for a given craft configuration.

Note however that at different altitudes and speeds, the Cd will vary dramatically (particularly above 20k alt and supersonic speeds). That shouldn't be too hard to test either, although will be more time-intensive (once you have the reference area though, you can use the Data + Stability Derivatives to get an idea of the drag at various speeds and altitudes).

Your overall aero drag will be approximately Cd*Reference Area*Q (in Newtons).

jarmund,

The XM-G50 is the best radial- mount intake. The Ram air intake is the best stack mount intake.

http://forum.kerbalspaceprogram.com/threads/106114-Stock-KSP-90-intake-comparo-for-SSTO-turbojets

It's been a long time since I've flown stock - those drag values seem odd (they used to be capped at 2.0) - or are you pre-multiplying them by mass?

[Taki117]

FAR's TurboJet nerfs reduce it's zero-thrust point to 1800m/s (vs 2400 for stock) - I whipped up a test craft, and was able to attain about Mach 4.7@35km.

I've never been able to achieve this. Oh well.

[GoSlash27]

It's been a long time since I've flown stock - those drag values seem odd (they used to be capped at 2.0) - or are you pre-multiplying them by mass?

Aye. The stock lumberwagon aero multiplies by the mass of both the intake itself and the air it contains at the moment.

But again, this is stock rather than FAR...

Best,

-Slashy