OpenRocket Issue: "Forward end of airframe is open (radius is > 0): 'transition'"

[JustinRocketry]

Hey all,

Was fiddling around with Openrocket and I couldn't seem to fix this issue of my rocket's forward end of airframe being open? I've swapped out the transition section and redone it several times but the error won't seem to go away. All the measurements of the transition section and surrounding body tubes seem to match. Does anyone have any tips on how to fix this issue?

Also just to be transparent I'm a complete novice so I apologize if I made a really dumb mistake.

Thanks,
Justin

 

[Art Upton]

I remember a post about this before, and it was marked as a bug.

 

[Art Upton]

Yep, here it is: https://www.rocketryforum.com/threa...open-when-it-clearly-isnt.189008/post-2651088

 

[Art Upton]

Hey all,

Was fiddling around with Openrocket and I couldn't seem to fix this issue of my rocket's forward end of airframe being open? I've swapped out the transition section and redone it several times but the error won't seem to go away. All the measurements of the transition section and surrounding body tubes seem to match. Does anyone have any tips on how to fix this issue?

Also just to be transparent I'm a complete novice so I apologize if I made a really dumb mistake.

Thanks,
Justin

On a second note, did you try adding a defined recovery device and it's deployment?

 

[neil_w]

The problem, specifically, is with the booster stage after separation. At that point, it is an open-ended tube, and simulation thereafter will not be accurate, which *sometimes* matters.

We'll do something more user-friendly in the next release vs. throwing up that error. It's a little trickier than it seems.

 

[lr64]

Good to know. I ran into that bug last night.

 

[Art Upton]

@JustinRocketry , your sim with the error on the stage Begs the Question; why is this defined as a two stage rocket with only one motor mount?

This looks like a (T)ARC egglofter rocket to carry two eggs sideways, needing the BT80 payload tube. Using F motors with a target near 780 feet?

So why two stages defined in the sim? Also look at your Feet Per Second off the rail. Have you left the default rail length at 3 feet in the sim or did you put the real length of the rail in the sim? Looks like you should have at least a 6 foot rail if not an 8 foot one.

Note here my Egg Crater only has one stage

 

[neil_w]

@JustinRocketry , your sim with the error on the stage Begs the Question; why is this defined as a two stage rocket with only one motor mount?

Entering such rockets as 2-stage is necessary to simulate the front and rear sections coming down under their own parachutes, common for TARC designs. I don't know if that applies to this design but I've seen so many like this that it's my first assumption.

 

[JustinRocketry]

Entering such rockets as 2-stage is necessary to simulate the front and rear sections coming down under their own parachutes, common for TARC designs. I don't know if that applies to this design but I've seen so many like this that it's my first assumption.

@Art Upton Yeah like Neil said I assumed we'd need to split up the rockets as 2-stage to simulate the detachment of both parts for recovery. I decided to do this because I remember seeing a thread a while back utilizing this approach but to be honest I'm not sure if the software can correctly simulate it this way

 

[neil_w]

but to be honest I'm not sure if the software can correctly simulate it this way

That is how it's done. The only potentially significant inaccuracy is the trajectory of the booster after separation. If you're close to apogee at separation then it doesn't matter.

 

[Art Upton]

Entering such rockets as 2-stage is necessary to simulate the front and rear sections coming down under their own parachutes, common for TARC designs. I don't know if that applies to this design but I've seen so many like this that it's my first assumption.

Thanks, I had not known that part was a reason.

 

[neil_w]

@JustinRocketry Would you be willing to provide us your ORK file so we can see what's happening? If you don't want to post it publicly then send it to me as a DM.

 

[JoePfeiffer]

@JustinRocketry Would you be willing to provide us your ORK file so we can see what's happening? If you don't want to post it publicly then send it to me as a DM.

Also, anybody else with a (T)ARC rocket showing the problem.