OR Q

[blackbrandt]

OK, so PM me as soon as you think I lost my mind.
I designed a High altitude, MD 2 stage rocket. Bottom Stage is a K185, or for a test flight an I285. Top stage is a D7. I light the bottom stage, then it burns out, coasts for 4 seconds, lights the top stage, drops away, and then deploys a streamer. The top stage, when it ignites, races up. Only problem is, I exceeded OR simulation limits. Could someone tell me what it would do with a program like RS? I am too cheap to get RS, and I already got Trial Version.
Thanks
Oh, PS, I am getting sponsored for this one.

View attachment High altitude 2-stage.ork

 

[eggplant]

There are many problems with the design, deeper than the fact that it won't work in OR. Such a long tube, especially one made of cardboard, will buckle under the forces. If you are going for altitude, why add extra weight and drag by making it longer? Also, I know this was probably a mistake, but cardboard fins just won't work. If you simulate just the booster with a nosecone on and shortened to a reasonable length, it can go to more than 10,000 feet. Do you have a tracker? The fins are huge for surface mount, and would likely be snapped off on a hard landing.

 

[jpummil]

Shouldn't actually be exceeding any OR limits...more likely a parameter that is conflicting.

Attached is a REALLY rough model I was using to look at some sim properties and it is similar in power...

View attachment Max-Alt-2-Stage.ork

 

[jpummil]

OK, so PM me as soon as you think I lost my mind.
I designed a High altitude, MD 2 stage rocket. Bottom Stage is a K185, or for a test flight an I285. Top stage is a D7. I light the bottom stage, then it burns out, coasts for 4 seconds, lights the top stage, drops away, and then deploys a streamer. The top stage, when it ignites, races up. Only problem is, I exceeded OR simulation limits. Could someone tell me what it would do with a program like RS? I am too cheap to get RS, and I already got Trial Version.
Thanks
Oh, PS, I am getting sponsored for this one.

Uhhh...why is your booster 180" long?!?! Just because you CAN do something in software (or in real life for that matter) doesn't mean you SHOULD...

 

[Sampo]

Hi,

The reason it's exceeding simulation limits is because the rocket is unstable. This is an extreme example of wind-caused instability, which is the stumbling block of long, skinny rockets.

At zero angle of attack the rocket has a stability margin of 3 cal, but already at 3 degrees AOA it's unstable by 0.5 cal, and at 10 degrees it's at -6 cal. You can see this by using the component analysis dialog. Skinny rockets may easily need 5-15 calibers of static stability margin to be truly stable, and this design takes it to a whole new extreme.

I'll investigate a bit further on what limits are being hit and why...

Regards,
Sampo N.

 

[Aksrockets]

Oh, PS, I am getting sponsored for this one.

:y::y::y: By who???!!!

Alex

 

[blackbrandt]

:y::y::y: By who???!!!

Alex

By a really nice guy who is L3 in both Nar and Tra, and lets me borrow casings all of the time.

 

[blackbrandt]

OK, here is the fixed model, but it is still exceeding sim values.View attachment High altitude 2-stage.ork