Observations of drag at the back of craft

[Sky_walker]

and it maxed out at 305k and around 1300 m/s. Crazy.

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Interestingly, using a fairing in place of the two nose cones on the radial got me to 315k.. even though the fairing is about twice the mass of the two nose cones.

Already tried it. Just inverted it and built down.

It was poor. The drag of it is relatively high and the extra mass negates any other usefulness. It made my little test rocket perform worse than putting nothing on the back end.

That's very interesting.

So fairings on top of the rocket seems to be working as expected, perhaps even better, further increasing your drag (I guess fairings shape plays a huge factor here),

but fairings at the bottom of the rocket work worse than having an inverted nose cone or even nothing at all.

[NathanKell]

Don't separate the fact that fairings are heavy. If fairings massed only a few kg, they'd help on the bottom too, but the aerodynamic savings of fairings on the bottom are outweighed by the loss to total delta V.

[Franklin]

See, I thought drag was going to be all about making sure that the front of your craft was pointy. Seems the back is just as important.

At 1km on this craft the fuel tank has a drag of 13.03...

http://i.imgur.com/TsOd1x4.png

Stick a nose cone on the bottom and the tank drag is now 1.54 but the cone has a drag of 7.9, total drag of 9.44 and carrying an extra 0.2t.

http://i.imgur.com/TnLFp1m.png

Swapping out the tail streamlining for an adapter and small nose cone, the tank drag is about the same (1.56) and the total drag of the three parts is 6.6, with 0.13 extra mass.

http://i.imgur.com/4pgOWbZ.png

So, the shape of the back end does have a very significant effect on drag, especially of the parts above it. I haven't figured out what is optimal yet though.

Launching the first and last craft straight up until out of fuel revealed the lowered drag has made a difference despite the extra mass:

No back end streamlining: 36,031km @ 1095.5m/s

With back end streamlining: 37,162km @ 1117.3m/s

Anyone else optimised a rear end? (*snarf snarf*)

I'm kind of curious what the drag is with this build without the landing I beams. I mean this is how it should behave, but part of me thinks it's a bug that just happens to otherwise make a profile behave like it should.

Either way, really interesting find.

[NathanKell]

Try this. Push a boat shaped like this:

<=>

through the water.

Then try something shaped like this:

|>

Gee, I wonder which will have lower resistance? Air is a fluid. It isn't light beams that only care about the front.

[Foxster]

Try this. Push a boat shaped like this:

<=>

through the water.

Then try something shaped like this:

|>

Gee, I wonder which will have lower resistance? Air is a fluid. It isn't light beams that only care about the front.

I think it was decided a little while ago that we all understand why it works as it does. That's not the issue. The slight surprise is that it was actually implemented. There are so many other oddities and inconsistencies with the new aero model that including this was unexpected.

[One Wheeled Panda]

Can't really test how a rocket engine would affect it sadly, as there are none that come close to matching the radials in TWR/Isp and the drag created by the radials is also an issue.

You could just mod one engine or another to produce the required conditions.

[rkman]

The one thing that i am surprised about is that an adapter+small nosecone reduces total drag more than a single large nosecone even though the shape is the same. That seems just wrong.

[Varsi]

The one thing that i am surprised about is that an adapter+small nosecone reduces total drag more than a single large nosecone even though the shape is the same. That seems just wrong.

Not to mention they have less mass... I had never thought about this since there's pretty much always an engine at that node.