billdz
Well-Known Member
- Joined
- Feb 10, 2017
- Messages
- 1,377
- Reaction score
- 121
Hello,
I'm planning to launch a Big Nuke 3E this Saturday on a K600 motor. However, on Open Rocket my sim says that stability with this motor is just 0.526. Even adding a kilogram in the nose cone does not get stability over 1.0.
I started with the stock file downloaded from https://www.rocketreviews.com/unknown-locprecision-pk-82-3e-big.html and modified the values to match my actual build, the values were fairly close. I am thinking that the issue is with the CP value in the file. The Rocket Reviews page says:
"CG: 49.6559 inches from front
CP: 63.8747 inches from front
Margin: 2.59 Overstable"
The actual file, however, says the CP is 149 cm (58.66") from the front, with "no motor" stability at 1.66.
My actual "no motor" CG is 49.7, about the same as what the web page says it should be. So it seems the question is whether the CP is 63.87", as the web page states, or 58.66", as the file states. Or am I missing something? If CP is 63.87", how to override the CP value in the file?
Another flier posted a similar question about the original Big Nuke (not the 3E) at https://www.rocketryforum.com/threads/big-nuke-stability.55495/, there was also an issue about the file.
Any thoughts on which CP value is correct? And has anyone encountered any stability issues flying a K600 or similar motor on a Big Nuke 3E?
Thanks,
Bill
I'm planning to launch a Big Nuke 3E this Saturday on a K600 motor. However, on Open Rocket my sim says that stability with this motor is just 0.526. Even adding a kilogram in the nose cone does not get stability over 1.0.
I started with the stock file downloaded from https://www.rocketreviews.com/unknown-locprecision-pk-82-3e-big.html and modified the values to match my actual build, the values were fairly close. I am thinking that the issue is with the CP value in the file. The Rocket Reviews page says:
"CG: 49.6559 inches from front
CP: 63.8747 inches from front
Margin: 2.59 Overstable"
The actual file, however, says the CP is 149 cm (58.66") from the front, with "no motor" stability at 1.66.
My actual "no motor" CG is 49.7, about the same as what the web page says it should be. So it seems the question is whether the CP is 63.87", as the web page states, or 58.66", as the file states. Or am I missing something? If CP is 63.87", how to override the CP value in the file?
Another flier posted a similar question about the original Big Nuke (not the 3E) at https://www.rocketryforum.com/threads/big-nuke-stability.55495/, there was also an issue about the file.
Any thoughts on which CP value is correct? And has anyone encountered any stability issues flying a K600 or similar motor on a Big Nuke 3E?
Thanks,
Bill
Last edited: