04-10-2023, 11:59 AM
|
 |
Master Modeler
|
|
Join Date: May 2021
Posts: 965
|
|
Quote:
|
Originally Posted by SolarYellow
I've seen anecdata (launch reports on the other forum) suggesting the Majestic may be marginally stable by itself. My hypothesis is that skinnying the fins up to make them more or less triangular gives away too much area compared to the fins on the Ascender, which AFAIK are the same as those on the booster. I bought a couple of those fin cans and some of the 2-inch tube before Estes closed it out that will be combined into single stage rockets when I get around to it.
|
The Rocksim file for the Majestic (without booster) which I believe I got from:
https://www.rocketreviews.com/rocks...x-majestic.html
shows an "overstable" 2.57 stability margin with an F15-6 loaded.
Attached is an image of the issue. Rule of thumb, if I recall correctly, for safe rod departure is 40 fps. Note where that velocity is obtained in the simulation with an Estes F15. The 29mm Estes BP motors have a very slow thrust buildup.
However, the launch details indicate "Velocity at launch guide departure: 31.7952 ft/s" for a 4 foot rod. That doesn't seem to match the graphed velocity versus altitude plot.
__________________
The other day I sat next to a woman who has a profound fear of flying. I wanted to comfort her, so I said, "Don't worry, we're not gonna' crash. Statistically, we got a better chance of being bitten by a shark." Then I showed her the scar on my elbow from a shark attack. I said, "I got this when my plane went down off of Florida." - Dennis Regan
|