drag issue on fairing

[king of nowhere]

I was experimenting with a lightweight laythe rocket, but was twarted by an abnormal drag on the aerodinamic fairing.

I see people with aerodinamic fairings all the time, and I heard that if you make it the root part, it will have very little drag. well, I tried to do just that, here's the result.

drag is 4 times greater than gravity drag, and it's all on the fairing.

i tried by comparison with a mk1 pod, which is almost frictionless

only 0.08 kN, 250 times less drag than the fairing, despite having the same speed at lower altitude. there is still a significant drag, but it's mostly the flat bottom.

i experimented with a more pointy fairing, and with changing the root part, but got no improvement.

what's the issue with fairings and drag?  I see people flying vehicles made of an external chair inside a fairing all the time, they wouldn't do that if there wasn't a way to reduce drag.

Edited March 9, 2023 by king of nowhere

[Lt_Duckweed]

7 hours ago, king of nowhere said:

I was experimenting with a lightweight laythe rocket, but was twarted by an abnormal drag on the aerodinamic fairing.

I see people with aerodinamic fairings all the time, and I heard that if you make it the root part, it will have very little drag. well, I tried to do just that, here's the result.

drag is 4 times greater than gravity drag, and it's all on the fairing.

i tried by comparison with a mk1 pod, which is almost frictionless

only 0.08 kN, 250 times less drag than the fairing, despite having the same speed at lower altitude. there is still a significant drag, but it's mostly the flat bottom.

i experimented with a more pointy fairing, and with changing the root part, but got no improvement.

what's the issue with fairings and drag?  I see people flying vehicles made of an external chair inside a fairing all the time, they wouldn't do that if there wasn't a way to reduce drag.

The key here is that when a fairing is the root part, the fairing panels do not count for drag.  This means that making it pointier does not help.  What you have to do is occlude the fairing base via node attachment.
In your screenshot, the YN face OccA value is almost 0, as that is the bottom of the base and is attached to the fuel tank, which almost fully covers it.
However, the YP face (which is the top of the base) OccA is 1.03, which isn't very covered at all, and the Wdrg value is 0.91, which is very blunt.  You can fix this via enabling interstage nodes on the fairing and attaching parts to the forwards facing interstage nodes until the YP face OccA and Wdrg values are down to reasonable levels (a Wdrg under .4 should be the minimum target).  This can be many small parts, such as cubic struts, or one larger part, such as a 1.25m nosecone.

Edited March 9, 2023 by Lt_Duckweed

[king of nowhere]

2 minutes ago, Lt_Duckweed said:

The key here is that when a fairing is the root part, the fairing panels do not count for drag.  This means that making it pointier does not help.  What you have to do is occlude the fairing base via node attachment.

oh, I see.
when expressed like this it feels like bug exploiting though, just a step short of kraken engines. I will build something else.

[camacju]

2 hours ago, king of nowhere said:

when expressed like this it feels like bug exploiting though, just a step short of kraken engines

It doesn't need to be exploity. You can do something like attaching a 1.25 meter fuel tank to the front of the fairing, or a 1.25 meter nose cone. It'll occlude just as well.