Struts and Part Counts

[FastMINI42]

I've been working on some large ships and starting to work on being more efficient with part counts. What I started getting concerned about was all the leftover anchor points when a payload is connected to the final stage. Do those count as parts? Or does the strut itself count as the part and when it vanishes, the anchor points don't matter? Or does just the first anchor point count?

So I setup a simple experiment with a very simple 2 stage rocket and found that when final part counts are a concern, it's important to draw the strut from the lower stage to the upper stage as the part count originates from the first anchor point. The second anchor point just sits there, not counting as a part. Which makes sense, since the first anchor point is the piece that is grabbed from the part menu.

Some screenshots:

The final stage, only 7 parts:

The complete rocket. 16 parts including 4 struts and 2 gantries:

By drawing the struts from the de-coupler to the final stage, the part count for the final stage came to 0 struts and 7 parts:

By drawing the struts from the final stage to the de-coupler, the part count for the final stage came to 4 struts and 11 parts:

As aside note, after I got done, I got to wondering if the little thing could get up to a 70km orbit. Tried a couple times, didn't quite get there. Then I had MechJeb try and it was successful ... barely:

(10km turn, 40% path, limit to terminal velocity on)

[AlamoVampire]

that is 1. an awesome lesson that will come in very very handy! and 2. a cute lil can of a ship! Jebediah would be proud!

[Dispatcher]

Wow. I'll need to remember this when I make my next large rocket. No wonder half my debris was struts. Thanks for the info!

[Vanamonde]

Either way you run the struts, the next time you load that ship (either from a save or by switching back to it) after discarding the previous stage, the strut nubs will disappear. (By the way, the receiving end of a fuel line does not disappear, but remains for the life of the ship.)

Edited September 18, 2013 by Vanamonde

[KerbMav]

Either way you run the struts, -1- the next time you load that ship (either from a save or by switching back to it) after discarding the previous stage, the strut nubs will disappear. (By the way, -2- the receiving end of a fuel line does not disappear, but remains for the life of the ship.)

Which is -1- awesome to know and -2- a bug in my eyes!

[SRV Ron]

An interesting topic.

Your ship, as designed so far, probably doesn't need the struts. Some tweaking of the size of the first stage fuel tank would probably help in getting into orbit.

As far as struts, a lot depends on the part design. Examples I will post are all Nova Punch parts.

This ship, a stack of five 1.25 x 6 meter tanks, has no struts. One would think from past experience that it would wobble itself apart in flight if not on the launch pad. Yet, it was extremely stable from launch to Kerbal escape velocity.

This one you would think would also be extremely stable. NOT! It wobbled like a wet noodle until I strutted the hell out of it. Even then, I had to add small cubes in order to get anchor points for struts to connect the tapered sections of that rocket. It still is not totally stable but flew straight enough to send the probe directly into Kerban.

[I_do_robots]

Regarding strut work and some things I'd like to offer...

In my builds, if the payload is heavy enough or stands out larger than the main tube diameter, moving the CG up the main body tube, I like to get the engine / tank cluster out wider. To do that, I like to use the little black and white pylons, attached to radial mounts and girders if I need them out further. It's simplistic but leaves much to be desired when it comes to stability through the launch and ascent. To keep the part count down (And weight) and still get the job done, I like to run struts to the upper and lower ends of each tank tube and a single connector at the tops and bottoms around the cluster as well. Keeps everything reasonably light and adds some structural integrity.

Things I got used to in doing this often.

- Regardless of whether it's a single strut or 8 at a time (Or anything in between) I always mount the first anchor on the main tube side. I don't know why, but the game physics engine seems to get confused, especially if I am doing multiple mirror attachments, and tries to only "Wrap" them around the single tank I start with if I try to attach the fist strut end to the item I want mated to the main body. It will then only attach the first one and wrap that tank with as many anchors as I would've liked to wrap the whole cluster with and the game still counts them as parts, despite that the anchor point is the only thing visible. I also usually cannot "Grab" the exposed part, usually the "Focus" highlight hovering the mouse, will only let me select what the anchor is attached to, so, another reason I start from the main body out and save often...Much easier to go back and reload a build then to have to tear stuff back off and replace them with identical assemblies because I lost 7 anchors in a fuel tank body.

I always anchor from the main rocket body out.

Sometimes, if it's just not going to accept a multiple mirror because the cluster layout is odd or I want to only anchor every other one but the pie wheel default changes as soon as I get the anchor near a rocket body part., then I almost have no choice but to "Single" select and individually place them and avoid another mess.

Anchors are strong, no need to "bird nest" struts all over the place. As long as the top, bottom, and radial integrity has some form of balanced structural support, I can get it into orbit.

I hope these observations help too...

One digressing side note:

The further out from the main tube I mount engine clusters, the more of a bear the whole thing become to get to respond to turns, especially during ascent in the atmosphere stage, so, I treat it like sailing, work with the wind, not force or fight it into a turn...If I over-correct, the whole thing may keep on going on over and start right back down in an unrecoverable dive surface bound. Fins (especially with ailerons) and canards do help some, but, if you go that route, get your turns in while you're at atmospheric levels, There will be a steady (Obviously) decrease in response as the air thins. I count on well placed thrusters to manage maneuvering and attitude adjustments once in orbit.

[daffy]

Great thread. Thank you!