stability of a saucer

[user 13]

Silly question, but I assume that in a saucer shaped rocket the C/P still needs to be below the C/G. The reason I ask is that I'm building a saucer rocket from a '60s tv show. As it is now it is 7 inches in diameter and 2 inches high fitted with a 24mm motor mount. The end of the motor sticks out the bottom. This will make it hard to keep the C/G above 1/3 of the way up. I made it with 24mm thinking it will have very high drag so I don't really want to add a lot of top weight to slow it down even more, but it needs to be stable.

Any Ideas?
Thanks

Mark

 

[Handeman]

I don't know where it is, but search the threads for spools. There is an equation for adjusting the rocksim CP for base drag. This is what the saucer is and IIRC the CP is actually below the saucer.

 

[boris katan]

By having a sharp outer edge, saucers achieve an extreme base drag effect. The Cp is actually below the body of the saucer, not like a conventional rocket.

Some Cp values listed on Art Applewhite's site:

https://www.artapplewhite.com/cp.html

Great saucers.

 

[user 13]

Thanks very much guys! That sets my mind at ease. I have no experience with saucers, I just decided to try this scratch build.

I'll post some photos soon.


Thanks again
Mark

 

[lessgravity]

Saucer from a TV show?
Wouldn't happen to be one of these?

 

[user 13]

Nope.

Wrong country, and a few years to late, But some have speculated....

That is a good idea though.

It won't take this group long to figure it out.

it began one lost night....

 

[lessgravity]

Oh
The Invaders

for those who are unfamiliar with the series
The Intro

 

[user 13]

Man that was fast!

I expected it to take at least 1/2 an hour!

I've been watching the series on DVD. It holds up not to bad.

Mark

Here is the major parts in a rough fit.

 

[WillCarney]

Generally the saucers have the CP below the body of the saucer. Any CG
from the center or forward of the center of the body will be fine. CG's closer
to the bottom will arc into the wind. For round suacers RocSim will simulate it
somewhat. The body of the round part is simply a round transition.

William