airstream protective shells?

[Cannon]

i find them completely useless since my rockets always work better without them, confirmed many times.

what's their purpose?

Edited August 24, 2015 by Cannon

[sal_vager]

Their purpose is to provide a protective shell from the airstream for non-aerodynamic and heat intolerant payloads.

[Geschosskopf]

What, the fairings? They protect delicate parts from atmospheric heating both during launch and when aerobraking at other planets. They also reduce drag and asymmetrical drag of lumpy payloads. However, really big fairings cause their own problems with rocket stability.

In general, fairings aren't needed all that much to launch from Kerbin except in extreme cases of lumpy payloads. However, they do help a lot when hitting another planet's atmosphere at interplanetary speeds.

[ForScience6686]

To protect the payload. Many payloads are designed only for spaceflight and would not withstand the aero forces of ascent. I would agree that it's not the most efficient method in game and the components aren't nearly as sensitive , but I enjoy using them myself. The added mass is easy enough to deal with.

[Starwaster]

They have too much mass per sq meter compared to real life fairings. I forget how much more but when the problem is corrected, they become much more valuable aerodynamically speaking.

[ajburges]

Even if the rocket is more efficent without it, fairings make rockets easier to fly. Having supersonic terminal velocity at launch means you don't have to alter throttle setting until Ap hits 50 km.

[Pecan]

...you don't have to alter throttle setting until Ap hits 50 km.

Why even then?

[Chakat Firepaw]

Because you don't want to overshoot your intended orbit?

[Pecan]

Because you don't want to overshoot your intended orbit?

Welcome to the forums, I am privileged your first post was a response to me :-)

Since the atmosphere on Kerbin extends to 70km, an Ap (Apoapsis, highest point of orbit) at 50km is too low to be 'overshooting' by quite a bit. Most importantly, you still need to build horizontal speed as quickly as possible. Certainly, by the time you've got a 50km Ap you've probably got all the 'up' you need, so you pitch-down towards the horizon, or even below it, so your Pe (Periapsis, lowest point of orbit) starts to raise as well. This way you can control exactly how quickly, or slowly, your Ap rises, with the maximum fuel-benefit for circularising Pe.

It's all about the gravity turn, and why "go straight up to space, then turn right" isn't a good way to orbit.

[ajburges]

Why even then?

To optimize your gravity turn.

At 50 km drag losses are minimal, so you want to focus on maximizing oberth effect and minimizing cosine losses to finalize orbit. Lock course to prograde (if it isn't already) and reduce thrust to barely advance Ap (the 45 sec to Ap rule). This keeps you speed up as you progress to Ap (Oberth effect) and keeps thrust aligned with velocity (to eliminate cosine losses). This slow burn also does most the circularization work, so once you get the Ap to your desired orbit and you reach it, you don't need to thrust off prograde at all (again, eliminating cosine losses).

A -300 x 70 km orbit needs 490 m/s to circularize, but you don't spend that much time on prograde. Get out of the soup too quick and you could be on a -500 x 70 km orbit which needs a 1125 m/s burn to circularize! (on a 13 min period)

On topic: with a fairing, once my Ap gets to 45-50 km I reduce throttle to 1/3 or less. This reduces the fuel I use to move the heavy fairing. The fairing itself is jettisoned between 38 and 50 km.

- - - Updated - - -

Welcome to the forums, I am privileged your first post was a response to me :-)

Since the atmosphere on Kerbin extends to 70km, an Ap (Apoapsis, highest point of orbit) at 50km is too low to be 'overshooting' by quite a bit. Most importantly, you still need to build horizontal speed as quickly as possible. Certainly, by the time you've got a 50km Ap you've probably got all the 'up' you need, so you pitch-down towards the horizon, or even below it, so your Pe (Periapsis, lowest point of orbit) starts to raise as well. This way you can control exactly how quickly, or slowly, your Ap rises, with the maximum fuel-benefit for circularising Pe.

It's all about the gravity turn, and why "go straight up to space, then turn right" isn't a good way to orbit.

Never thrust below the horizon. If you overshoot the desired Ap, either increase drag or Hohmann transfer down to desired orbit from Ap instead of circularizing. Both are more efficient than killing the energy you build up.

Horizontal speed as quickly as possible only applies if you are going for the cannon on the moon approach. Atmosphere complicates the issue. What you really want is to have orbital speed in the horizontal component (and zero in the vertical) when you reach Ap with minimal losses. Part of that is controlling when and where Ap is. Getting an "up" component is just about placing Ap so that you have time for trust and gravity to displace your velocity vector as you want.

Edited August 25, 2015 by ajburges

[Pecan]

To optimize your gravity turn ... eliminate cosine losses ... throttle to 1/3 or less ... reduces the fuel I use to move the heavy fairing.

Staging. What you're saying is that all that work is just because you have way too much thrust available, which in turn means you're wasting a lot more than you gain by carrying engines you aren't using.

(And you hid the rest of your post with colour, so I won't take that up - as you say, we ought to get back on topic ^^)

Something funny with forum-update when you edited your post there. Anyway, nothing we need discuss here.

On topic - if fairings help then use them, if they don't then - like everything else - leave them off and save part-count, mass, funds and fuel.

Edited August 25, 2015 by Pecan

[ajburges]

True, reduced staging lifters trend to have too much thrust after 20 km.

Unless I am dealing with a tricky payload, my lifters trend to be a LFO core ringed by Kickbacks. I can build a new one per payload in 10 minutes and they all fly similarly with some decent recovery on top.

[Skorpychan]

They help wonderfully when launching bulky, aerodynamically dirty payloads. Such as a cluster of probes, or station parts with docking ports and girders sticking out all over the place.

[MadChris48]

I use them all the time. In fact, almost never launch without them. Then again, I usually do pretty aggressive launches, turning early and pushing the limits of speed and heat.

I'd really like to see an inter-stage fairing, it would really open up the building design options.

[Fearless Son]

I'd really like to see an inter-stage fairing, it would really open up the building design options.

You can do that:

[MadChris48]

You can do that:

bless you.

[Sharpy]

One suggestion: Build a spaceplane/glider, with a preset AoA of its canards (angled upwards). Stick it on top of your rocket and try to deliver it to the orbit. See how far you go without fairings.

Probably you'll go somewhere past VAB and hit the administration building.

[felcas]

I know this is old, but if someone get here like I did it would be nice to find updated info. 

I am using KSP 1.3 and at this moment, I made several tests and Fairing does influence aerodynamics. I read on several places that this wasn't the case in the past but if you come here looking for information, I guess things changed.

[bewing]

They certainly influence the aerodynamics. The question is whether they are worth their mass and cost. I personally don't think so in 90% of the cases. Because it's only for the first 20km of most of your trips that you are even in an atmosphere that has any real substance.

[maceemiller]

I'm using 2 of them in my Jool 5 challenge for my landers and they are so much lighter than a storage bay. 

[Lelitu]

19 hours ago, bewing said:

They certainly influence the aerodynamics. The question is whether they are worth their mass and cost. I personally don't think so in 90% of the cases. Because it's only for the first 20km of most of your trips that you are even in an atmosphere that has any real substance.

They're quite useful on assymetric satellite designs, where symmetry may be hard to arrange, or result in carrying more massive comms arrays than needed. The aero forces can be enough to make the first 20km impossible without a fairing.

[Spricigo]

20 hours ago, bewing said:

They certainly influence the aerodynamics. The question is whether they are worth their mass and cost. I personally don't think so in 90% of the cases. Because it's only for the first 20km of most of your trips that you are even in an atmosphere that has any real substance.

So, in your opinion, they are worth in 10% of the cases?  Which cases? 

I found it essential for some satellites,  the ones light enough to be placed in space by a single Hammer or Thumper.  Which may be half of my launchs in early career. 

Resource scanners also comes to my mind,  but I don't launch many of those. 

 

[Wanderfound]

Handy on spaceplanes, BTW:

That one has a fairing stashed just in front of the RAPIER, stuffed full of low-heat-tolerance science gear.

[Foxster]

About the only time I use them is when I am trying to get something that has parts with lift and control surfaces (e.g. a spaceplane) into orbit on top of a rocket. These can be a real pain to loft without a fairing because they can handle very badly and may even flip. 

Fairings are, basically, too heavy and most other parts are forgiving enough not to need protection from heat.  

[felcas]

On 2017-6-10 at 4:08 AM, bewing said:

They certainly influence the aerodynamics. The question is whether they are worth their mass and cost. I personally don't think so in 90% of the cases. Because it's only for the first 20km of most of your trips that you are even in an atmosphere that has any real substance.

I understand there are lots of ways to play this game, for example, there are people who thinks ridiculous contraptions are totally valid, it is indeed a way to explore the game mechanics and have lots of funs, other people play the game as it not as a simulator of reality and try to get most efficiency out of game mechanics (maybe you are in this category?) and some other like myself likes to play the game as a simulation of reality, I know there is a LOT missing, but I love the feeling of space exploration and I try to imerse and imagine I am really doing it, because of this I like to use fairings a lot, I actually find satisfaction on deploying them in space, it even brings me some space movies scenes.

Thats it...if you don't like fairings or don't see a good reason to use them, don't use, but most important, HAVE FUN