vjp
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I've noticed in a few of my rockets, a tendency for the hot exhaust gases to char the bottom of the rocket, sometimes severely.
The rockets which have this problem share some common design characteristics:
1. Wide, flat base (larger than the motor diameter), with no boattail. Baby Bertha, Fat Boy, etc.
2. Motor fits flush with the bottom of the rocket, or sticks out very little.
I think what is happening is that a vacuum is being created in the wake of the rocket, and the hot motor exhaust is accumulating in that wake, even being sucked back into the tail section of the rocket (the gap between the MMT and BT). In a Baby Bertha I just built, with a "D" motor it got so hot the innermost layer of the BT actually began to peel.
Anyone ever do any empirical research on this? I'm building a 5x cluster Saturn V with engine bells in place for flight, and I'm wondering how much the motors should protrude below the bells to prevent plastic meltdown.
The rockets which have this problem share some common design characteristics:
1. Wide, flat base (larger than the motor diameter), with no boattail. Baby Bertha, Fat Boy, etc.
2. Motor fits flush with the bottom of the rocket, or sticks out very little.
I think what is happening is that a vacuum is being created in the wake of the rocket, and the hot motor exhaust is accumulating in that wake, even being sucked back into the tail section of the rocket (the gap between the MMT and BT). In a Baby Bertha I just built, with a "D" motor it got so hot the innermost layer of the BT actually began to peel.
Anyone ever do any empirical research on this? I'm building a 5x cluster Saturn V with engine bells in place for flight, and I'm wondering how much the motors should protrude below the bells to prevent plastic meltdown.