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Open Source Construction Techniques for Craft Aesthetics

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sgt_flyer

sgt_flyer

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Posted (edited)

@Majorjim

what i can't do with no open end is shifting the SRB upwards to move the COM :)

granted, for classic rocket designs COM's position is not a problem, but for shuttle style the COM position is a big deal for controlling a shuttle design with offset thrust (by limiting the shuttle's liquid engines angle, you end up lowering your DeltaV losses and sideways drift  :) (and the COM should also move less when you drop your SRB's)

and with the SRB shifted upwards that much, i need an opening ;) to let the thrust out (be it by simply closing the fairing around the skirt, very close to your design, or by creating an open ended nozzle to create the nozzle's shape underneath for aesthetics purposes.

 

in the end, it's a different point of view on the problem, between pure aethetics and low part count and trying to add a bit more versatility to the design :) both are valid depending on the design you are pursuing :) (it the end, it's nitpicking on optimisation for a given design, but heh :) they also sometimes nitpick in real life to gain every little d/V they could :)

 

on another problem, i can confirm that adding nosecones to any additionnal kickback clipped in helps :) (with 10 additionnal kickbacks with varying amounts of fuel (so the liftoff TWR is higher, but limits itself during ascent as the SRB's with less fuel burn out), i've gone from 900 km altitude to 1100km by putting nosecones on the additionnal kickbacks - same amount of fuel & thrust between the two boosters)

 

Edited by sgt_flyer
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Majorjim!

Majorjim!

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Just now, sgt_flyer said:

@Majorjim

what i can't do with no open end is shifting the SRB upwards to move the COM :)

granted, for classic rocket designs COM's position is not a problem, but for shuttle style the COM position is a big deal for controlling a shuttle design with offset thrust (by limiting the shuttle's liquid engines angle, you end up lowering your DeltaV losses and sideways drift  :) (and the COM should also move less when you drop your SRB's)

and with the SRB shifted upwards that much, i need an opening ;) to let the thrust out (be it by simply closing the fairing around the skirt, very close to your design, or by creating an open ended nozzle to create the nozzle's shape underneath for aesthetics purposes.

 

in the end, it's a different point of view on the problem, between pure aethetics and low part count and trying to add a bit more versatility to the design :) both are valid depending on the design you are pursuing :) (it the end, it's nitpicking on optimisation for a given design, but heh :) they also sometimes nitpick in real life to gain every little d/V they could :)

 

on another problem, i can confirm that adding nosecones to any additionnal kickback clipped in helps :) (with 10 additionnal kickbacks with varying amounts of fuel (so the liftoff TWR is higher, but limits itself during ascent as the SRB's with less fuel burn out), i've gone from 900 km altitude to 1100km by putting nosecones on the additionnal kickbacks - same amount of fuel & thrust between the two boosters)

 

OK, that's a bit clearer. I see that in order to have some fancy additions you need another fairing. I just know I could design out issues with lower COM SRBs. I am working on a shuttle at the moment.

 I will put one together for that maybe a see if I encounter any issues.

At least does knowing yo can cover more of the SRB help at all with your version?

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sgt_flyer

sgt_flyer

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@Majorjim

yup, it helped :) i've rebuilt a new version using only two fairings, and no more need for the MK1 structural fuselage. (the same 'open ended' one with nozzle from the bottom, and a long one pulled from the top like yours (it's the one i used as the COM shift example a couple posts back) - allowed me to shave a bit of dry weight :)

Edited by sgt_flyer
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Majorjim!

Majorjim!

Posted
Posted
Just now, sgt_flyer said:

@Majorjim

yup, it helped :) i've rebuilt a new version using only two fairings, and no more need for the MK1 structural fuselage. (the same 'open ended' one with nozzle from the bottom, and a long one pulled from the top like yours (it's the one i used as the COM shift example a couple posts back) - allowed me to shave a bit of dry weight :)

Huh, that's great! I'm standing on your shoulders in this case but I am happy I could help. I'm sorry it took me a few posts to see. I still find understanding written instructions difficult. Dat dyslexia.. Very frustrating. Ho hum, It's a great technique man.

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  • 4 weeks later...
drewscriver

drewscriver

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How to achieve a really smooth looking rear engine, like the following: 

screenshot92.png

This particular combination works beautifully for nukes, but the same approach may work for other engines as well.

 

screenshot101.png

Basically, attach the engine to the node as usual.  Then attach the nosecone to the rear nozzle of the engine.  Go to the engine and disable the shrouds.  Then offset the nosecone forward until it covers the part of the engine you want (in this case, I have shifted the Aerodynamic Nose Cone forward until the curve precisely meets the curve of the atomic motor).  Then offset the engine forward until the nosecone is flush with the rear of the tank.

This also has the side-effect of eliminating the rear node of the rocket; I'm not sure if there are aerodynamic benefits to this or not anymore.

Edited by drewscriver
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Rune

Rune

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On 27/1/2016 at 4:27 AM, drewscriver said:

This also has the side-effect of eliminating the rear node of the rocket; I'm not sure if there are aerodynamic benefits to this or not anymore.

From a very informative conversation with @NathanKell here, I learned yesterday that engines make surprisingly good nosecones. Apparently, the aero model takes their aerodynamic "dragginess" from the taper angle of the cone it can draw around it, and here comes the weird part: due to a bug the game doesn't discern between cones and funnels, it just takes their angle as an absolute value and goes with it. So the funnel of the engine bell looks to the game the same as a very sharp cone, and engines end up with attached bow shocks and very low drag coefficients.

 

Rune. More than likely to be fixed at some point in the future.

Edited by Rune
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drewscriver

drewscriver

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3 hours ago, Rune said:

From a very informative conversation with @NathanKell here, I learned yesterday that engines make surprisingly good nosecones. Apparently, the aero model takes their aerodynamic "dragginess" from the taper angle of the cone it can draw around it, and here comes the weird part: due to a bug the game doesn't discern between cones and funnels, it just takes their angle as an absolute value and goes with it. So the funnel of the engine bell looks to the game the same as a very sharp cone, and engines end up with attached bow shocks and very low drag coefficients.

 

Rune. More than likely to be fixed at some point in the future.

Interesting and useful post.  I guess Rapiers must be a special case, as I believe the benefit of adding a rear-facing small nosecone has already been established.  I agree that the funnel/cone bug is likely to be addressed (as is the rear-facing open node issue, and reversed nose-cone exploit for that matter).  Still, I play the current version, and not the next, so thanks for the heads up!

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NathanKell

NathanKell

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@Rune technically what happens is that the drag cube is created by rendering the part from each of the six (three +, three -) axes. The basic drag coefficient (modified later) is just the average of, for each pixel, the dot of the normal with the axis (so flat = 1, totally sideways = 0, 45 degree angle = 0.707 etc). There's no easy way to tell whether that's sloping in or out.

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Rune

Rune

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28 minutes ago, NathanKell said:

@Rune technically what happens is that the drag cube is created by rendering the part from each of the six (three +, three -) axes. The basic drag coefficient (modified later) is just the average of, for each pixel, the dot of the normal with the axis (so flat = 1, totally sideways = 0, 45 degree angle = 0.707 etc). There's no easy way to tell whether that's sloping in or out.

And that makes a lot of sense. Also, it is more complicated than I thought! And barring these cases, it should actually give good results. I'm sure there are ways to patch the edge cases... in this case, modeling engine bells as the solid cones they behave like IRL, would actually do the trick, and the intakes would still drag less.

 

Rune. Very nice to have this kind of stuff explained, BTW. :)

Edited by Rune
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Mad Rocket Scientist

Mad Rocket Scientist

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1 hour ago, Natskyge said:

Landing leg cargo bays,

Well, I found this:

http://forum.kerbalspaceprogram.com/index.php?/topic/39663-open-source-construction-techniques-for-craft-aesthetics/&page=22#comment-1315964

ETA:
The post below that, actually.

 

Edited by Mad Rocket Scientist
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sgt_flyer

sgt_flyer

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i'm wondering, would it be a good thing to start a new thread once 1.1 goes live ? (it would have a link to this thread in the new one of course) a lot of techniques here were created on older versions of KSP, from even before the translation tools were avaible, and several even use parts that are no longer the same in game.

plus, the links in the thread's OP were broken during the forum switch to IPS, leaving it really difficult to find anything :)

Edited by sgt_flyer
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Mad Rocket Scientist

Mad Rocket Scientist

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13 hours ago, sgt_flyer said:

i'm wondering, would it be a good thing to start a new thread once 1.1 goes live ? (it would have a link to this thread in the new one of course) a lot of techniques here were created on older versions of KSP, from even before the translation tools were avaible, and several even use parts that are no longer the same in game.

plus, the links in the thread's OP were broken during the forum switch to IPS, leaving it really difficult to find anything :)

That seems like a good idea.  With new wheel physics, I'm sure there will be loads of new construction techniques, too.

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