# Velcro Rockets

#### sputnik

Donator
Yes, it sets the orientation of the attach point, so changing it will rotate the booster about the attach point.

And, as you've seen, if the orientation vector isn't normalized, strange results ensue.

Yes, trig is going to be required.

To quote myself, choosing 1 0 0 puts the thing along the X-axis; 0.877 0.5 0 is 30 degrees off from that; 0.5 0.877 0 is 60 degrees off, and so on. To put 8 boosters around, they'd be at 1 0 0, and .707 .707 0, and 0 1 0, and -.707 .707 0, and so on.

##### New member
Yes, it sets the orientation of the attach point, so changing it will rotate the booster about the attach point.

And, as you've seen, if the orientation vector isn't normalized, strange results ensue.

Yes, trig is going to be required.

To quote myself, choosing 1 0 0 puts the thing along the X-axis; 0.877 0.5 0 is 30 degrees off from that; 0.5 0.877 0 is 60 degrees off, and so on. To put 8 boosters around, they'd be at 1 0 0, and .707 .707 0, and 0 1 0, and -.707 .707 0, and so on.

Never did take trig :facepalm:

So, if the first booster is in the right place at 4 0 1, what should it's rotation #'s be, and what should be the #'s of the next booster?

#### sputnik

Donator
Well, trig is what you need here.

Sigh. If the first booster is at (4,0,1), its orientation should be (1,0,0).
The next one, at 45 degrees around, well, the sine and cosine of 45 degrees is 0.707, so the position should be 0.707*4, or (2.828, 2.828, 1) and direction should be (0.707, 0.707, 0).
The third booster would be at (0,4,1) and direction (0,1,0).
The fourth would be at (-2.828, 2.828,1) and direction (-0.707, 0.707, 0).
The fifth would be (-4,0,1) and direction (-1,0,0).
The sixth would be (-2.828, -2.828,1) and direction (-0.707, -0.707, 0).
The seventh is (0,-4,1) and direction (0,-1,0).
The eighth is (2.828, -2.828,1) and direction (0.707, -0.707, 0).

#### Donamy

Donator
Beta Tester
That's what I like about AC3D. Just place two vertices and it gives you the normalized angle.

#### sputnik

Donator
I need to explore AC3D some more, then. I didn't know it could do that.

#### Donamy

Donator
Beta Tester
I'm thinking of using your velcro rockets for my Jason Mars lander. I like the fact that you can use the VC during launch, which multistage2 does not.

#### DaveS

Donator
Beta Tester
That's what I like about AC3D. Just place two vertices and it gives you the normalized angle.
Donamy, could you PM me with the exact procedure to obtain the normalized vectors?

#### Donamy

Donator
Beta Tester
To set the normal angles in the console and

clipboard.

goto the tcl folder, open the ac3d.tcl file

find:

set cent [ac3d get_selection_centre]

}

display_message "axis: $axis" puts "axis:$axis"
clipboard clear
clipboard append $axis It should look like this: set cent [ac3d get_selection_centre] display_message "axis:$axis"
puts "axis: $axis" clipboard clear clipboard append$axis
}

Then while in vertex mode select 2 vertices, select rotation mode, click C then set axis. You should see the three numbers in the bottom center of the screen.

One thing to remember is that the X axis in AC3D is opposte from Orbiter, so if the first number negative, change it to positive and visa versa.

##### New member
Well, trig is what you need here.

Sigh. If the first booster is at (4,0,1), its orientation should be (1,0,0).
The next one, at 45 degrees around, well, the sine and cosine of 45 degrees is 0.707, so the position should be 0.707*4, or (2.828, 2.828, 1) and direction should be (0.707, 0.707, 0).
The third booster would be at (0,4,1) and direction (0,1,0).
The fourth would be at (-2.828, 2.828,1) and direction (-0.707, 0.707, 0).
The fifth would be (-4,0,1) and direction (-1,0,0).
The sixth would be (-2.828, -2.828,1) and direction (-0.707, -0.707, 0).
The seventh is (0,-4,1) and direction (0,-1,0).
The eighth is (2.828, -2.828,1) and direction (0.707, -0.707, 0).

Thank youuuu!

Sorry, math was never one of my strong points... if you need literary analysys & copy editing of a manual, or mechanical work on an actualrocket,that I can help you with.:blush:

Almost finished here... now that the boosters are in the right place, I'd like to get them to jettison in pairs a couple seconds apart. I figured I could just set each pair with a little less fuel than the final pair. I thought this would be thru the PRPLEVEL line, but that doesn't seem to affect anything. Is this even possible without a .cfg for each pair, or do the booster need the FUEL line for that?

Also, is there any easy way to view the various fairings & interstages in the Velco parts bin, other than creating each one manually with the scenario editor & guessing?

#### sputnik

Donator
You certainly SHOULD be able to set the PRPLEVEL in each booster's paragraph (not the one for Energia-M), but if you're starting on a launch pad the auto-refuel feature of the launch pad might be defeating your intent. You could try giving each booster a location that's out in space, and then it would only click into place when you ignite the engines, but that's not very reliable.

You could try tweaking with a Maxfuel =
Or, you could keep the fuel where it is and adjust the burn rate slightly by tweaking the thrust (MaxMainThrust = ) instead.

To see what's in the Velcro toolkit, best way is to browse the folder and read the .cfg's. Hopefully they explain a bit what they do. That doesn't show you what they look like, though.

##### New member
You certainly SHOULD be able to set the PRPLEVEL in each booster's paragraph (not the one for Energia-M), but if you're starting on a launch pad the auto-refuel feature of the launch pad might be defeating your intent. You could try giving each booster a location that's out in space, and then it would only click into place when you ignite the engines, but that's not very reliable.

You could try tweaking with a Maxfuel =
Or, you could keep the fuel where it is and adjust the burn rate slightly by tweaking the thrust (MaxMainThrust = ) instead.

To see what's in the Velcro toolkit, best way is to browse the folder and read the .cfg's. Hopefully they explain a bit what they do. That doesn't show you what they look like, though.

What's the proper syntax for the PRPLEVEL call?

If I set up fairings as "stages," parallel burn to the Energia-M, JETT_ON_EMPTy 0, will they then separate along with it?

#### sputnik

Donator
PRPLEVEL 0:1.000
...to set the first tank (tank 0) to full. Just cut and paste; it's certainly used elsewhere in the scenario.

If I set up fairings as "stages," parallel burn to the Energia-M, JETT_ON_EMPTy 0, will they then separate along with it?

I can't say I've ever tried that. But it certainly ought to work.
But what's wrong with doing it the usual way?

##### New member
PRPLEVEL 0:1.000
...to set the first tank (tank 0) to full. Just cut and paste; it's certainly used elsewhere in the scenario.

I can't say I've ever tried that. But it certainly ought to work.
But what's wrong with doing it the usual way?

I'm trying that now, but not sure how to make it work right. My payloads are strapped to both sides of the Energia core. So I need pairs of fairing to jettison in the same direction. ie, two to the "left," two to the "right," as opposed to "left, right, up and down" like a normal 4-part fairing would. Make sense?

#### N_Molson

Donator

##### New member
I'm trying that now, but not sure how to make it work right. My payloads are strapped to both sides of the Energia core. So I need pairs of fairing to jettison in the same direction. ie, two to the "left," two to the "right," as opposed to "left, right, up and down" like a normal 4-part fairing would. Make sense?

OK, nevermind about the fairings, figured out how to get it to work like I wanted, disgustingly easy too with how I had it set up. :facepalm:

So my last problem, if you please, is that the autopilot seems to have a mind of its own now. No matter what I set the launch azimuth to, whether in the .scn or with the U key in-sim, it always puts me into a polar orbit with a heading of around 150? Here's the finished (mostly) working .scn:

Code:
BEGIN_DESC
The Energia booster
END_DESC

BEGIN_ENVIRONMENT
System Sol
Date MJD 39307.95
END_ENVIRONMENT

BEGIN_FOCUS
Ship Energia-M
END_FOCUS

BEGIN_CAMERA
TARGET Energia
MODE Extern
POS 9.73 -0.51 -123.30
TRACKMODE TargetRelative
FOV 50.00
END_CAMERA

BEGIN_HUD
TYPE Surface
END_HUD

BEGIN_MFD Left
TYPE Surface
END_MFD

BEGIN_MFD Right
TYPE Orbit
PROJ Ship
REF Earth
END_MFD

SCREENHEIGHT 150
PITCHMULTIPLE 0.15
MINPITCH 50

BEGIN_SHIPS
Energia:Velcro/EnergiaCore
STATUS Landed Earth
BASE Doberai:6
FUEL 0.9
CONFIGURATION 0
PAYLOAD Zvezda /ISSR/ISS_Zvezda /ISSR/Zvezda 0 6.5 -6 118000.0 0 0.0 1.0
PAYLOAD Zarya /ISSR/ISS_Zarya /ISSR/Zarya 0 -6.5 -6 118000.0 0 0.0 1.0
DELAYSTART 5
END
Energia-M:Velcro/EnergiaMCore
STATUS Landed Earth
BASE Doberai:6
FUEL 1.0
CONFIGURATION 0
SERIESBURN 0 Energia 0.0 0.0 -30  0.0 1.0 0.0
PAYLOAD Interstage Velcro/Shuttle_ACC Velcro/Shuttle_ACC 0 0 14.5 1500 0 1
END
Booster1:Velcro/EnergiaBooster
STATUS Landed Earth
BASE Doberai:6
CONFIGURATION 0
PRPLEVEL 0:0.5 1:0.5
PRIMEBOOSTER 0
CENTERTHRUST 1
PARALLELBURN 1 Energia-M 4 0 1  1 0 0
NAVFREQ 21 50
XPDR 20
TIPOFF 2
END
Booster2:Velcro/EnergiaBooster
STATUS Landed Earth
BASE Doberai:6
CONFIGURATION 0
PRPLEVEL 0:1.0 1:1.0
PRIMEBOOSTER 0
CENTERTHRUST 1
PARALLELBURN 1 Energia-M 2.828 2.828 1  0.707 0.707 0
NAVFREQ 21 50
XPDR 20
TIPOFF 2
END
Booster3:Velcro/EnergiaBooster
STATUS Landed Earth
BASE Doberai:6
CONFIGURATION 0
PRPLEVEL 0:1.0 1:1.0
PRIMEBOOSTER 0
CENTERTHRUST 1
PARALLELBURN 1 Energia-M 0 4 1  0 1 0
NAVFREQ 21 50
XPDR 20
TIPOFF 2
END
Booster4:Velcro/EnergiaBooster
STATUS Landed Earth
BASE Doberai:6
CONFIGURATION 0
PRPLEVEL 0:1.0 1:1.0
PRIMEBOOSTER 0
CENTERTHRUST 1
PARALLELBURN 1 Energia-M -2.828 2.828 1  -0.707 0.707 0
NAVFREQ 21 50
XPDR 20
TIPOFF 2
END
Booster5:Velcro/EnergiaBooster
STATUS Landed Earth
BASE Doberai:6
CONFIGURATION 0
PRPLEVEL 0:1.0 1:1.0
PRIMEBOOSTER 0
CENTERTHRUST 1
PARALLELBURN 1 Energia-M -4 0 1  -1 0 0
NAVFREQ 21 50
XPDR 20
TIPOFF 2
END
Booster6:Velcro/EnergiaBooster
STATUS Landed Earth
BASE Doberai:6
CONFIGURATION 0
PRPLEVEL 0:1.0 1:1.0
PRIMEBOOSTER 0
CENTERTHRUST 1
PARALLELBURN 1 Energia-M -2.828 -2.828 1  -0.707 -0.707 0.0
NAVFREQ 21 50
XPDR 20
TIPOFF 2
END
Booster7:Velcro/EnergiaBooster
STATUS Landed Earth
BASE Doberai:6
CONFIGURATION 0
PRPLEVEL 0:1.0 1:1.0
PRIMEBOOSTER 0
CENTERTHRUST 1
PARALLELBURN 1 Energia-M 0 -4 1  00 -1 0
NAVFREQ 21 50
XPDR 20
TIPOFF 2
END
Booster8:Velcro/EnergiaBooster
STATUS Landed Earth
BASE Doberai:6
CONFIGURATION 0
PRPLEVEL 0:1.0 1:1.0
PRIMEBOOSTER 0
CENTERTHRUST 1
PARALLELBURN 1 Energia-M 2.828 -2.828 1  0.707 -0.707 0.0
NAVFREQ 21 50
XPDR 20
TIPOFF 2
END
ACC1:Velcro/Shuttle_ACC
STATUS Landed Earth
BASE Doberai:6
CONFIGURATION 0
PRPLEVEL 0:1.0 1:1.0
PRIMEBOOSTER 0
CENTERTHRUST 1
PARALLELBURN 0 Energia-M 0 6.5 38  0 1 0.0
Fairing 2 0.0 0.0 5.0 0.0
PAYLOAD fairing1 Velcro/parts/EnergiaMFair_1 Velcro/parts/EnergiaMFair_1 0 0 7 1250 0 1 0.0
PAYLOAD fairing2 Velcro/parts/EnergiaMFair_2 Velcro/parts/EnergiaMFair_2 0 0 7 1250 0 1 0.0
END
ACC2:Velcro/Shuttle_ACC
STATUS Landed Earth
BASE Doberai:6
CONFIGURATION 0
PRPLEVEL 0:1.0 1:1.0
PRIMEBOOSTER 0
CENTERTHRUST 1
PARALLELBURN 0 Energia-M 0 -6.5 38  0 1 0.0
Fairing 2 0.0 0.0 5.0 0.0
PAYLOAD fairing3 Velcro/parts/EnergiaMFair_1 Velcro/parts/EnergiaMFair_1 0 0 7 1250 0 1 0.0
PAYLOAD fairing4 Velcro/parts/EnergiaMFair_2 Velcro/parts/EnergiaMFair_2 0 0 7 1250 0 1 0.0
END
END_SHIPS

#### sputnik

Donator
You probably have a little stage trying to turn a great big stack, and it's trying for 090, it's just not getting there.

Try setting them up with alternate headings. Try 270.0, for a start. You'll probably have better luck.

##### New member
You probably have a little stage trying to turn a great big stack, and it's trying for 090, it's just not getting there.

Try setting them up with alternate headings. Try 270.0, for a start. You'll probably have better luck.

Thank you, that worked nicely.

Sigh. Just when I think I'm getting it figured out. I'm trying to get that "Dome1" to sit "flat" on the stage, just rotate it 90* about the Z axis, and the trig has me stymied again. Lil' help please?

Code:
Dome1:BCP01
STATUS Orbiting Earth
RPOS -1786799.05 -2531921.25 5566561.37
RVEL -445.851 52.424 -119.326
AROT -24.46 16.28 179.80
VROT 0.09 -0.10 -0.00
ATTACHED 3:0,TransStage
AFCMODE 7
NAVFREQ 0 0
END
TransStage:TransStage-L
STATUS Landed Earth
BASE Doberai:6
AFCMODE 7
PRPLEVEL 0:0.999889
THLEVEL 7:0.003136 8:0.003136 9:0.003492 10:0.003492 15:0.000006 16:0.000006
NAVFREQ 0 0
CONFIGURATION 0
PRIMEBOOSTER 1
CENTERTHRUST 0
COUNTINGDOWN 1
SERIESBURN 0 Dome1 0.0000 0.0000 -2.0000 0.0000 0.0000 -1.0000 0.0000 1.0000 0.0000
END

#### N_Molson

Donator
Vector problem : the cross product of those two vectors _V(0,0,-1) and _V(0,1,0) isn't equal to _V(0,0,0). I think.

SERIESBURN 0 Dome1 0.0000 0.0000 -2.0000 0.0000 0.0000 -1.0000 0.0000 1.0000 0.0000

Here the result is _V(1,0,0). Try values that give you _V(0,0,0).

Last edited:

#### sputnik

Donator
Nah, that's easy. You need it to say:

SERIESBURN 0 Dome1 0.0000 0.0000 -2.0000 0.0000 0.0000 -1.0000 1.0000 0.0000 0.0000

No trig involved. You just needed to tell it, instead of head-up being out the +Y direction (last three numbers _V(0, 1, 0)) they should be 90 degrees off that, head-up being +X direction such as _V(1, 0, 0). -1 would work as well.

But what's that
ATTACHED 3:0,TransStage
doing in the Dome definition? That shouldn't be there, ever, and will certainly cause errors. Velcro Rockets does use attachments, but it has to make them itself, and it's supposed to break them before quicksaving. If it starts the scenario already attached, confusion will ensue.

##### New member
Nah, that's easy. You need it to say:

SERIESBURN 0 Dome1 0.0000 0.0000 -2.0000 0.0000 0.0000 -1.0000 1.0000 0.0000 0.0000

No trig involved. You just needed to tell it, instead of head-up being out the +Y direction (last three numbers _V(0, 1, 0)) they should be 90 degrees off that, head-up being +X direction such as _V(1, 0, 0). -1 would work as well.

But what's that
ATTACHED 3:0,TransStage
doing in the Dome definition? That shouldn't be there, ever, and will certainly cause errors. Velcro Rockets does use attachments, but it has to make them itself, and it's supposed to break them before quicksaving. If it starts the scenario already attached, confusion will ensue.

That seems to be coming from Orbiter if I save the .scn in-sim. Popped up in another .scn too, but doesn't seem to be causing any trouble there.

Rotation still not right here. Tried 1 & -1 in both the first & second positions of the last 3 digits, it just rotates the dome around the vertical. Lesse if I can get a screenshot working here, should be more obvious what I'm trying to do...

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