ACP Composites

The Rocketry Forum

Help Support The Rocketry Forum:

TRFfan

Well-Known Member
Joined
Aug 5, 2015
Messages
1,211
Reaction score
2
If the nozzle is up inside the boattail it will reduce thrust because of something called Krushnic Effect. Even if it's not in contact with the flame.
I heard that it happens when the nozzle is inside the BT by more than 1 tube diamiter. The nozzle would be inside by only about 7-10 mm.

“Krushnic Effect: A very dramatic phenomenon where your rocket makes a tremendous amount of noise and smoke but doesn’t go anywhere! This happens when the motor is recessed into the body tube by more than one tube diameter. If so recessed, the cylindrical volume below the motor forms a secondary expansion chamber which allows the exhaust gasses to expand below atmospheric pressure before leaving the rocket. Surrounding air aspirated into the exhaust stream causes turbulence which negates much of the thrust, along with creating the characteristic roar. A multi-stage model that ejects its booster motor, but not the airframe, is a perfect example. Very damaging; it almost always destroys the lower body tube beyond use. Named for Richard Krushnic, the rocketeer who characterized the effect in the late ’60s. “


And the closure is "custom" but not modified? Anything other than the exact part from CTI would not be legal for a record. And that part can't be modified in any way, otherwise it's an EX motor, and not legal for records.
I'm not modying the organal closure but making a new one. So I don't know if that would be legal for a record.

Many people make male molds from styrofoam and dissolve it with gasoline.
I heard it can also be done with 3D printed molds.
 

dhbarr

Amateur Professional
Joined
Jan 30, 2016
Messages
7,236
Reaction score
1,652
Replacing a manufacturer's certified part with one of one's own devising almost certainly counts as modified / EX.

I -really- wish CTI would put out tailcone closures for 24 & 38 as they have for 29 & 54, but they had no plans in that regard last time they write back.

Possibly a third party could submit their own hardware to TMT w/ CTI loads, but that person would then be a manufacturer and thus ineligible for a record.
 

watheyak

Barnstormer
TRF Supporter
Joined
May 11, 2009
Messages
987
Reaction score
781
Location
Arizona
And if it's EX you'd also have to be Tripoli level 2 to fly it.
 

TRFfan

Well-Known Member
Joined
Aug 5, 2015
Messages
1,211
Reaction score
2
Replacing a manufacturer's certified part with one of one's own devising almost certainly counts as modified / EX.

I -really- wish CTI would put out tailcone closures for 24 & 38 as they have for 29 & 54, but they had no plans in that regard last time they write back.

Possibly a third party could submit their own hardware to TMT w/ CTI loads, but that person would then be a manufacturer and thus ineligible for a record.
Oh ok.
 
Top