[roc-chat] Re: Stability: Time to Use the Mojo
- From: Jack Garibaldi <jackgaribaldi@xxxxxxx>
- To: <roc-chat@xxxxxxxxxxxxx>
- Date: Thu, 18 Aug 2011 17:23:42 -0700
Put a K in that mother and the booster will come off automatically
LOL!!!!!!!!!!!!!!
Jack G
From: roc-chat-bounce@xxxxxxxxxxxxx [mailto:roc-chat-bounce@xxxxxxxxxxxxx]
On Behalf Of Richard Dierking
Sent: Thursday, August 18, 2011 5:09 PM
To: roc-chat@xxxxxxxxxxxxx
Subject: [roc-chat] Re: Stability: Time to Use the Mojo
Thank you for this offer, and I apologize for the delay in my reply. I'm
continuing to work on the Delta II and will be entering info into Rocksim 9
in a couple weeks. I have the Delta X file that had a 4" dia core and 4
strap-ons of the same dia, so I'm just going to modify this data for the
sim.
I'll post how the build is going and perhaps bring the rocket under
construction to the Sept launch.
Thanks again for all the help,
Richard Dierking
_____
Date: Fri, 12 Aug 2011 11:25:12 -0700
From: indanapt@xxxxxxxxx
Subject: [roc-chat] Re: Stability: Time to Use the Mojo
To: roc-chat@xxxxxxxxxxxxx
If you'd like I can punch the numbers into ROCKSIM with and without
shadowing. I just need the basic dimensions to get you a CP (not CG but CP).
Just ask.
---------------------------------------
Jeff Gortatowsky, Redondo Beach, CA | Twitter: JeffGortatowsky | Yahoo:
indanapt
"(Scientific) Skepticism is not a set of beliefs, it is a set of methods for
asking questions about reality." -- Doctor Steven Novella
_____
From: Richard Dierking <redierking@xxxxxxxxxxx>
To: roc-chat@xxxxxxxxxxxxx
Sent: Thursday, August 11, 2011 8:36 AM
Subject: [roc-chat] Re: Stability: Time to Use the Mojo
Not at all; very good question. I considered this. I wanted to keep the
fin number down to a minimum because the strap-ons are ejected (with pyro
bolts) and I don't want them hitting the fins. The first six strap-ons that
are ejected are on opposite sides of each fin. This will leave the last
three airstarted strap-ons centered between the three fins and should help
to provide fin area for the correcting force during the last part of powered
flight.
Richard
_____
Date: Wed, 10 Aug 2011 21:01:58 -0700
Subject: [roc-chat] Re: Stability: Time to Use the Mojo
From: rubr.duky@xxxxxxxxx
To: roc-chat@xxxxxxxxxxxxx
Silly question... Why not six?
On Wed, Aug 10, 2011 at 20:46, Richard Dierking <redierking@xxxxxxxxxxx>
wrote:
Thank you! After reading the first couple of replies I was beating my head
against my desk and saying "why did I make the fins pink and blue!" and "why
did I ask those guys!" I did appreciate the humor.
If I showed the rocket core without the strap-ons (I'll use different
colored paper next time), you might say the blue fins are large enough.
But, the strap-ons hide the size. For one side, the pink fin is 120 cm^2
and the blue fin is 90 cm^2. So, the pink fin has about 25% more surface
area but only sticks-out 3/4" more. 4" Goblin fins have about 85 cm^2 per
side There are 4 fins on a Goblin and I usually build with 4 fins. I can't
do that with a 9 strap-on configuration.
As usual, as the mass of the solid engines is consumed, the CG will move
forward. But, the strap-ons will shed during the flight and change the CP
and keep in mind that each of the core fins are between strap-ons that will
be released during powered flight. This really complicates things.
I thought about adding fins to the strap-ons but this creates some
additional problems like re-contact after deployment and the possible roll
force on the attachment points.
(one hour later...)
I'm going to use the pink-sized fins.
Thank you, and I'm going to blame all of you if the rocket's overstable or I
become unstable. :)
Richard
> Subject: [roc-chat] Re: Stability: Time to Use the Mojo
> From: allen.farrington@xxxxxx
> Date: Wed, 10 Aug 2011 13:49:29 -0700
> To: roc-chat@xxxxxxxxxxxxx
>
> Pink, definitely. You know, how big should they be if the pods had no CP
effect, but still have the mass? I think that they look small.
>
> Allen
> --------------------------------------------------------------------
> Allen H. Farrington
> 818-653-2284
> web: http://www.allenfarrington.org
>
> On Aug 10, 2011, at 12:58 PM, Richard Dierking wrote:
>
> > When you're working on something like this Delta II you start to develop
mind roll. I realized that I need to make a decision on the fins before I
become a really old man.
> >
> > So, please look at the two photos showing a blue and pink fin. There
will be 3 fins and they will be transparent and the rocket's about 6' tall.
As Barney would say, "time to use our imagination..." Please provide your
vote.
> >
> > Thank you. I'm going off to do something simple like work.
> >
> > Richard
> > <bluefin.jpg><pinkfin.jpg>
>
>
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