Ye Olde Rocket Forum

Ye Olde Rocket Forum (http://www.oldrocketforum.com/index.php)

- SAM - Semroc Astronautic Modeler Team (http://www.oldrocketforum.com/forumdisplay.php?f=36)

- - Starlight (http://www.oldrocketforum.com/showthread.php?t=11320)

The Starlight is online now.

Sheryl@semroc

Very kewl!:cool:

Linky

Another

Quote:

Originally Posted by Sheryl@Semroc

The Starlight is online now.

Sheryl@semroc

Bring some to NARAM, I want one!

Hmm. The photo or artwork is not showing up for me.

Next order will have to include it. Man, I have a backlog to build down.

Order in ----- Hehehehehehehehe...this is so cool

Quote:

Originally Posted by Sheryl@Semroc

The Starlight is online now.

Sheryl@semroc

My order is in also.

I loaded the RockSim file into OpenRocket and found that I needed to increase the nose weight from .2 oz to .7 oz to get a the rocket to show as stable (Cal => 1.0) when any engines were installed.

Is this because OpenRocket does not understand the Rings?.. or should I trust it and add the extra weight?

I'd trust Semroc. I don't think they'd sell you an unstable rocket.

The Starlight is another old design that was probably marginal at the time. With no nose weight, Rocksim gave a margin of .54 using a C6-5 and a margin of 1.27 with the added .2 oz. weight. I never saw a Starlight back then that was unstable, but we still added the weight for margin in our release.

I have been trying OpenRocket on our designs and the results are always more conservative. I do not know where the differences are. We always select Rocksim stability equations instead of Barrowman equations for stability calculations. Perhaps OpenRocket uses the older, less accurate equations. Probably half of our kits would be marginal or unstable if we used Barrowman, yet they clearly are not. (Well the Mars Lander is clearly marginal and should never have been released. :D )

Semroc Groonies: *Marginally* stable?

Quote:

Originally Posted by Carl@Semroc

The Starlight is another old design that was probably marginal at the time. With no nose weight, Rocksim gave a margin of .54 using a C6-5 and a margin of 1.27 with the added .2 oz. weight. I never saw a Starlight back then that was unstable, but we still added the weight for margin in our release.

I have been trying OpenRocket on our designs and the results are always more conservative. I do not know where the differences are. We always select Rocksim stability equations instead of Barrowman equations for stability calculations.

Perhaps OpenRocket uses the older, less accurate equations. Probably half of our kits would be marginal or unstable if we used Barrowman, yet they clearly are not. (Well the Mars Lander is clearly marginal and should never have been released. :D )

The RockSim file for your Saki Groonie has had me shaking my head, given the following figures, *with* nose weight:

Empty -- 1.15 calibers
A8-3 -- 0.78 marginal
B6-4 -- 0.75 marginal
C6-5 -- 0.68 marginal

:eek:

But you *say* it flies okay "in the real world?" :o

It makes me want to push that motor mount back until the engine hook lines up with the main body tube, instead of having it recessed. :eek:

Just sayin'.

.

The Goonies and Groonies are all "short, squat" designs that somehow get "aerodynamic exemptions" from the one caliber rule. I have heard of people changing the engine mount in the old Goonies from 13mm to 18mm, not adding nose weight and having stable flights. Rocksim shows that to be impossible.