Fix the Mk3 non-occlusion bug! The drag is pulling craft out of the sky! (pictures) (Discussion)

[HafCoJoe]

This very aerodynamic shuttle isn't capable of gliding with anything more then a 45 degree tilt.

Here's why:

Everything from the front of the craft to the back is attached by nodes. The only parts that should be giving drag is the cockpit, and the probe core on the back, but every single piece in the line is creating massive amounts of drag. Literally the only way to safely land this shuttle is by coasting at a 45 degree angle, and pulling up at the last second, hoping that the craft converts downward momentum to forwards before it stalls from drag and crashes.

- Please, please fix this soon.

Please ask me for a craft file download if you need one moderators/devs. I don't want to post straight it as I'm quite proud of it's design.

Edited May 5, 2015 by Avera9eJoe

[thereaverofdarkness]

If it is creating extra drag, wouldn't that make it easier to land it safely? If you must put it at a high angle of attack to slow it to a safe speed, does that not indicate that when it is pointed into the wind, the fuselage is not creating drag? Perhaps you need more wing surface or better landing gear, or I am not understanding the problem correctly.

[HafCoJoe]

If it is creating extra drag, wouldn't that make it easier to land it safely? If you must put it at a high angle of attack to slow it to a safe speed, does that not indicate that when it is pointed into the wind, the fuselage is not creating drag? Perhaps you need more wing surface or better landing gear, or I am not understanding the problem correctly.

The extra drag is causing the craft to fly so slowly that it stalls if you attempt to level out. The problem isn't with wings either, it has plenty. Landing gear isn't an issue either.

[thereaverofdarkness]

The extra drag is causing the craft to fly so slowly that it stalls if you attempt to level out.

Okay, I get it now.

I haven't flown with Mk 3 parts after the full release, but at a glance it looks like your craft has a very low density. Is it possible that you've simply got too much attack surface compared to its mass? Have you tried swapping the cargo bays for fuel tanks, or putting something heavy in the cargo bays? I'd also suggest more wing surface, you really don't have much there. And then you might need more engine power for the increased load, but that's just part of flying Mk. 3 parts.

If that doesn't work, I don't know, sorry.

[Murph]

The extra drag is causing the craft to fly so slowly that it stalls if you attempt to level out. The problem isn't with wings either, it has plenty. Landing gear isn't an issue either.

That doesn't make sense to me, as a real world pilot. A high angle of attack is one of the ways to enter a stall. Reducing the angle of attack, to level out, or even dive, is how you avoid the stall or recover from it. It sounds to me like you're actually flying it right on the edge of a stall, if the nose is 45° above horizon for level flight.

It's hard to be certain, but I'm guessing you mean that it won't maintain altitude without having the nose very high? If that's the case, you're either too slow, or have insufficient wing. From the pictures, I don't see very much wing at all, for the size of the craft. It looks to me like you've got the wings of an Aeris 4A on a much larger and heavier craft. On the Aeris 4A, the wings are about right for normal atmospheric flight from subsonic to mach 3, including 50–100m/s gliding and landing.

You might be trying to emulate NASA's Shuttle, but that had quite terrible atmospheric flight characteristics (compared to a normal aircraft). It was often described as a "flying brick", bordering on being unflyable. It basically had just enough flight capability to do a single pre-calculated direct approach and bleed off enough speed to land safely. There was no scope for a missed approach (expected result: crash), or a mis-calculated re-entry and descent (expected result: crash). The error margins were very small, and got progressively smaller as you got closer to the ground. If you want good atmospheric flight characteristics, do not copy the Shuttle.

The red drag lines that you are seeing might be coming off the body sections of the craft, not the occluded contents. It's hard to tell from the pictures.

[Wanderfound]

Yes, its a bug, and I'm sure it will be fixed in 1.0.3.

For now, the Stock Bug Fix mod has you covered: http://forum.kerbalspaceprogram.com/threads/97285-KSP-v1-0-Stock-Bug-Fix-Modules-%28Release-v1-0-0-27-Apr-15%29-Misc-Utilities-%2818-Jan-15%29

[HafCoJoe]

That doesn't make sense to me, as a real world pilot. A high angle of attack is one of the ways to enter a stall. Reducing the angle of attack, to level out, or even dive, is how you avoid the stall or recover from it. It sounds to me like you're actually flying it right on the edge of a stall, if the nose is 45° above horizon for level flight.

The red drag lines that you are seeing might be coming off the body sections of the craft, not the occluded contents. It's hard to tell from the pictures.

Edited May 5, 2015 by Avera9eJoe

[thereaverofdarkness]

I tried flying something vaguely similar to your craft. It doesn't have most of the extra bits on the back or in the cargo bay, and I tossed in some engines because I don't even see any on yours aside from the SRBs on the wingtips. It looks like you clipped a Mk. 2 cockpit with a Mk. 3 to 2.5m adapter, but I didn't want to deal with that so I just slapped a Mk. 3 cockpit on it. I have the fuselage and wings basically the same as yours.

Here's how it turned out for me:

http://imgur.com/a/iTSZU#0 (link in case the embed doesn't work)

<iframe class="imgur-album" width="100%" height="550" frameborder="0" src="//imgur.com/a/iTSZU/embed"></iframe>

I didn't experience the craft falling at steep angles, rather it flew reasonably straight. What did happen, however, was that it flipped out of control at very moderate angles of attack. I had to add a Mk. 3 Monopropellant tank to the front just to bring the center of mass far enough forward for it to fly, but maybe that mimics whatever that is you had in the cargo bay.

[HafCoJoe]

Alrighty I'm awake again! I tried one last thing last night which worked surprisingly well. I added a set of Elevon 3's to either side of the nose and the gliding greatly improved. I find this interesting as I haven't needed to add frontal flaps to anything after 1.0 dropped. I had to do so all the time before, but it greatly helped out this one.

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I'm not sure why this worked this time - I usually don't need extra lift like that in the front (at least in 1.0+). The drag occlusion is still a big issue though.