Gemini titan scratch build.

I have the 2.6 inch printed Gemini capsule and interstage. I need to know the body tube lengths for the 1st and 2nd stages. Help! Thanks, Mark.


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According to Rockets of the World, the real dimensions are:

Diameter: 120"
Stage 2 height: 223.17"
Interstage height: 149.73"
Stage 1 height: 569.92"
Stage 1 engine extends 122.66"

Your exact scale heights will vary based on which 2.6" tube you use- typically the inside diameter is always 2.56" but the outside diameter varies between manufacturers.

Does that help?

LithosphereRocketry said:

According to Rockets of the World, the real dimensions are:

Diameter: 120"
Stage 2 height: 223.17"
Interstage height: 149.73"
Stage 1 height: 569.92"
Stage 1 engine extends 122.66"

Your exact scale heights will vary based on which 2.6" tube you use- typically the inside diameter is always 2.56" but the outside diameter varies between manufacturers.

Does that help?

Click to expand...

It gives me a good place to start from. I’m using the Estes bt-80 tube. Thanks, Mark.


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Titan was 10' or 120" in diameter. If the base of your part is 2.6" then your scale factor is (new size/old size) 2.6/120 = .021

Use this image to get the measurements you want, multiply by the scale factor.
https://spacemodels.nuxit.net/gemini1.jpg

kj

kjohnson said:

Titan was 10' or 120" in diameter. If the base of your part is 2.6" then your scale factor is (new size/old size) 2.6/120 = .021

Use this image to get the measurements you want, multiply by the scale factor.
https://spacemodels.nuxit.net/gemini1.jpg

kj

Click to expand...

Thanks, KJ. I believe the scale is 1:45.


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Yeah, pretty close. If you flip the equation around and do old size/new size you get 46. So you could either divide all your source dimensions by 46 or multiply by .021 to get there.

I like to make spreadsheets of major dimensions for scale projects, so making a formula that figures out the scale factor and then applying that to the prototype measurements really helps. Since you already know your tube based on the part you have, you get to miss the fun of plugging in different tube diameters to find a close scale. :wink:

Can't wait to see what you come up with. BT-80 is a great size for a GT.

kj

Hi, Kj. I'm finally getting all the parts together for my GT. Boyce capsule, shapeways interstage and nozzles, acurr8 wraps, and twin aerotech 18/20's. I also have the parts for the ICBM version with twin 24/40's. I almost forgot, I have the Boyce 4inch capsule and shapeways interstage. I think I'll do that one with twin 29/40/120's.

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You probably will need good ignitors to get two 24 mm composite motors to fire simultaneously.

aerostadt said:

You probably will need good ignitors to get two 24 mm composite motors to fire simultaneously.

Click to expand...

A better approach might be to use a pair of D12 motors, ignited with Q2G2 igniters.

James

aerostadt said:

You probably will need good ignitors to get two 24 mm composite motors to fire simultaneously.

Click to expand...

I’ve clustered CTI E22 / E31 motors with 100% success (so far!), using the supplied igniters.

dpower said:

I’ve clustered CTI E22 / E31 motors with 100% success (so far!), using the supplied igniters.

Click to expand...

Dpower, that sounds encouraging. Small composite motors like the AT 24 mm are known to be difficult to ignite. Does the CTI E22 and E31 have the pyrogen pellet like the bigger motors?

aerostadt said:

Dpower, that sounds encouraging. Small composite motors like the AT 24 mm are known to be difficult to ignite. Does the CTI E22 and E31 have the pyrogen pellet like the bigger motors?

Click to expand...

Yes they do. I’ve flown mixed clusters using up to 7 motors (3xE22+4xD12, and 3xE31+4xD12). The CTI motors seem to light as fast as the BP motors. Only once did one motor fail to light, and that was one of the D12s, probably due to clay in the nozzle. The E31 seems to start a hair faster than the E22, but that’s probably just my perception due to their thrust curve.