OpenRocket Streamer Issue

[Who_Cares]

I am currently in the middle of designing a rocket in OpenRocket that uses duel deployment. I was thinking about maybe using a streamer instead of a drogue chute. However, it seems to be acting weird when I put the streamer in. For example, if I don't put any recovery devices in the rocket at all OpenRocket says the rocket will fall slower than if I deploy a streamer at apogee. Does anyone know why this?

 

[K'Tesh]

I'm not an expert the mathematics behind OR, but perhaps the streamer would make the rocket fall in a more streamlined arrangement (hanging straight down) than if it didn't have the streamer (both segments flopping around, mostly sideways).

Of course having the .ork file might help those who do have the mathematics to answer the question.

 

[dhbarr]

I think that's right, it's no longer tumbling. You should be able to plot stability with no recovery; with streamer; with a small drogues and see the tradeoffs.

 

[Buckeye]

I don't think OR is smart enough to understand drogue-less dual deploy with two ends flopping around. No recovery device means the rocket stays intact. If the CP/CG is large, the rocket will nose over and return to earth ballistic. This seems fine. If the CP/CG is smaller, then OR will get cute and try to simulate some bizarre gliding with lots of side motion. Look at side profile and vertical orientation to see what OR is trying to do. I played with it and got unrepeatable, flakey results. I don't trust it.

If a recovery device is included, then its drag characteristics take over when deployed in the simulation. Streamers are notoriously hard to quantify/simulate. Use a parachute instead. Use a very small parachute and tune it to simulate drogue-less.

 

[dhbarr]

Bizarre gliding, lots of side motion, unrepeatable, flakey are all what I would expect to see from a tumbling sack of parts.

Fully agree, enough drogue to line it up.

 

[Buckeye]

Bizarre gliding, lots of side motion, unrepeatable, flakey are all what I would expect to see from a tumbling sack of parts.

No. Open Rocket does not simulate a tumbling stack of parts. How could it? If there is no streamer/parachute in the design, then there is no recovery event available in the "configuration." It is greyed out. So, I assume this to mean a prang return to earth. Only if it is extremely nose-heavy, it will simulate as a classic parabolic impact. Otherwise, OR attempts some crazy backsliding, I think. This is what I find unreasonable. Most "normal" rockets will nose-over and lawn dart, right? Try it and see.

 

[dhbarr]

I say: some of this stuff can't be reasonably simulated.

You say: OR should stop pretending to simulate some of this stuff.

I think we're pretty much on the same page