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Fairings Experiment - Should You Use them


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I wanted to see if fairings made a difference as there was some discussion on Facebook in regards to their importance (or not importance due to added weight)

 

Here's the result of a short and simple scientific experiment:

 

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Interesting and informative, thanks.

Obviously this is only a single example, so results will of course vary depending on the ship and payload, but it's good to see the difference on this fairly simple ship as a quide.

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41 minutes ago, RokRoland said:

Could someone summarize the test and the result in writing for those of us who are reading the forum but can not view the video? Thanks!

The vid says: fairings are cool, but you should jettison them pretty early. 25km or thereabouts.

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Unfortunately I don't think the game is strong enough in this area.  Craft designed to only be used in space would not be able to survive the trip through the atmosphere.  Which is why they are used IRL.  Which is why I would disagree with this summarization, and for rp purposes I don't ditch until 50+ km.  I wish they would implement a damage model that would take this into consideration and not allow you to take your delicate science instruments screaming through the atmosphere without damaging them.

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Actually, in the video he dropped the fairings at 48km. Total savings on his ship (which was built to be a somewhat extreme example) was a measly 3% from using 2.5m fairings. *yawn*

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5 hours ago, AnTREXon said:

I wanted to see if fairings made a difference as there was some discussion on Facebook in regards to their importance (or not importance due to added weight)

Here's the result of a short and simple scientific experiment:

 

I believe your test has some bias. No one who understands KSP atmosphere physics would launch a rocket with those flat surfaces expecting better efficiency.

I did my own test. The payload is not nearly as "draggy", but it's not perfect either.  IMO this is a real in game situation where I ask myself "should I use a fairing?"

The only difference was the AE-FF2 Airstream Protective Shell (2.5m) fairing on the right was substituted for a Rockomax Brand Adapter on the left. Same launch methodology as as your tests - MechJeb to 80km. I let MJ automatically deploy the fairing at 50 km up.

xlrNRyX.jpg

So on this rocket, no-fairing slightly edged out fairing.

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7 minutes ago, MalevolentNinja said:

I believe your test has some bias. No one who understands KSP atmosphere physics would launch a rocket with those flat surfaces expecting better efficiency.

I did my own test. The payload is not nearly as "draggy", but it's not perfect either.  IMO this is a real in game situation where I ask myself "should I use a fairing?"

The only difference was the AE-FF2 Airstream Protective Shell (2.5m) fairing on the right was substituted for a Rockomax Brand Adapter on the left. Same launch methodology as as your tests - MechJeb to 80km. I let MJ automatically deploy the fairing at 50 km up.

xlrNRyX.jpg

So on this rocket, no-fairing slightly edged out fairing.

That looks like a rather blunt fairing though, I would make it more tapered.

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43 minutes ago, FishInferno said:

That looks like a rather blunt fairing though, I would make it more tapered.

Hmmm - I always wondered about that. I'm going to go test a more tapered fairing right now :)

Edit - tested.

Note: I had to redesign the rocket slightly to be more stable. A long pointy fairing on the short rocket was flipping. The new version uses an orange tank instead of the medium size Rockomax tank, but everything else is the same. This rocket does get to orbit on the first stage, unlike my previous test. Not that I think that matters for this test.

1nUFI7j.jpg

Uv2wCxK.jpg

No fairing is still best. Surprisingly, the stubby fairing is better than the long pointy fairing.

But if you think about it this makes sense - the more fairing material you use, the heavier the rocket. Overall weight matters more than drag on this rocket.

Personally, what I take away from these tests is this: "If you are going to use a fairing, keep it as small as possible".

Edited by MalevolentNinja
added new test
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As @MalevolentNinja just pointed out, sometimes the mass of the fairings outweigh any aero savings you may get.  But as a user of remotetech, most of my ships have antenna that cannot survive an exposed launch, so fairings are a must.  I've also found a use for fairings when I have a large/long unstable payload.  If I mount a few Quantum Struts on the payload facing the fairing, that helps steady it during launch. 

So it basically boils down to a per scenario answer.  Does the payload require protection from aero forces?  Does the payload have enough drag that the mass of fairings will result in a positive dv difference? 

This can also be offset by launch speed.  A fast launch will (I assume) incur more aero drag dv loss, while a slow launch (through the thicker atmo), will reduce it. 

As each ship we launch is different in many aspects, it's very very difficult to say yes or no to this question. 

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6 hours ago, gargamel said:

As @MalevolentNinja just pointed out, sometimes the mass of the fairings outweigh any aero savings you may get.  But as a user of remotetech, most of my ships have antenna that cannot survive an exposed launch, so fairings are a must.  I've also found a use for fairings when I have a large/long unstable payload.  If I mount a few Quantum Struts on the payload facing the fairing, that helps steady it during launch. 

So it basically boils down to a per scenario answer.  Does the payload require protection from aero forces?  Does the payload have enough drag that the mass of fairings will result in a positive dv difference? 

This can also be offset by launch speed.  A fast launch will (I assume) incur more aero drag dv loss, while a slow launch (through the thicker atmo), will reduce it. 

As each ship we launch is different in many aspects, it's very very difficult to say yes or no to this question. 

I'm getting way off topic here, but don't you use the Reflectron DP-10 for launch? Then you can activate your sensitive antennas once you are out of the atmosphere.

Edited by MalevolentNinja
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I believe, and it's been a few weeks since I launched anything, they do peel off even unopened.   I do use the DP-10 (that's the sideways stick in a block right?), but it stays on the stage that brings me to a circular orbit, so I ditch it once I stage.  It helps keep the part count down.    But the more I think about it, maybe they don't, but yes I do use the Dp-10 for launch and orbit, then open the bigger ones. 

I did make a version of the DP-10 that has more range, but is offset with more mass and power consumption.  I use that for unmannded landers and rovers where the comm sats are too high up for the regular one and I need constant communication during reentry.  

But there are things, not just antenna, that break off in the air, so sometimes fairings are required. 

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