Quantcast

Open Rocket doubt: flight event "exception"

The Rocketry Forum

Help Support The Rocketry Forum:

Eduardo

Member
Joined
Oct 16, 2020
Messages
18
Reaction score
1
Hello, everybody. I was using OpenRocket and when I launched my rocket, this result was given. The acceleration suddenly started to increase and the simulation ended. This moment was marked as an flight event: exception.
Please help me to understand what is going on: what's the fhysical phenomenon behind it? Why did it heppen? Is it something bad? How should I try to resolve this?
.
.
.
.
.
Please forgive me if it's a trivial question :)
 

Attachments

mooffle

Well-Known Member
TRF Supporter
Joined
Apr 20, 2020
Messages
135
Reaction score
81
Every sim I try regardless of engine after the first 2 shows this same exception. Did you change something in the design between flights sims 2 and 3? It almost seems like it's hitting terminal velocity.

The change in velocity might also be from the fins generating lift as it rotates. Not sure how OR sees that as a recovery method.

As an aside I hope you aren't planning on building this model. it clearly isn't safe, thought it makes for a neat simulated experiment.
 

0011001100

A Person
Joined
Jun 28, 2017
Messages
501
Reaction score
142
Location
Northern VA
I've ran into this issue as well when attempting to design a two stage rocket and it happens on second stage ignition. Stability graph works fine and shows it as stable throughout but it still occurs.
 

Eduardo

Member
Joined
Oct 16, 2020
Messages
18
Reaction score
1
Every sim I try regardless of engine after the first 2 shows this same exception. Did you change something in the design between flights sims 2 and 3? It almost seems like it's hitting terminal velocity.

The change in velocity might also be from the fins generating lift as it rotates. Not sure how OR sees that as a recovery method.

As an aside I hope you aren't planning on building this model. it clearly isn't safe, thought it makes for a neat simulated experiment.
I'm just testing some dynamics of OpenRocket. In simulations 1 and 2, the air pression was removed. The design of rocket has been constantly changed.
I don't intend to construct this rocket. The materials are visible hard, maybe impossible, to get and construct.
I was thinking if the drag had passed gravity, so the acceleration could have increased this amount. Althought, I don't know why the simulation stop when this happens.
Thanks for the comment
 

Eduardo

Member
Joined
Oct 16, 2020
Messages
18
Reaction score
1
I've ran into this issue as well when attempting to design a two stage rocket and it happens on second stage ignition. Stability graph works fine and shows it as stable throughout but it still occurs.
I think that's such an weird result.
I think it can be a consequence of the drag force.
Txs
 

neil_w

Chuffed as ninepence
TRF Supporter
Joined
Jul 14, 2015
Messages
9,769
Reaction score
2,889
Location
Northern NJ
I can't reproduce that, although I do get the "value out of range" error on simulation three. For what it's worth, this is a bug that is fixed in the forthcoming release. As 0011001100 mentioned, it usually afflicts multistage rockets, although the conditions on this one are so weird that you found a way to make it happen on a single stage. :)

Note that on sim 1 and sim 3, the launch rod length is set to 0. I'm surprised it gives any kind of reasonable result at all.
 

Eduardo

Member
Joined
Oct 16, 2020
Messages
18
Reaction score
1
I can't reproduce that, although I do get the "value out of range" error on simulation three. For what it's worth, this is a bug that is fixed in the forthcoming release. As 0011001100 mentioned, it usually afflicts multistage rockets, although the conditions on this one are so weird that you found a way to make it happen on a single stage. :)

Note that on sim 1 and sim 3, the launch rod length is set to 0. I'm surprised it gives any kind of reasonable result at all.
Yes, I'm making tests with the OpenRocket tools, and it's not such a good rocket to construct.
Happy (or not) that I could surprise you.
Thanks for the explanation.
 

Nytrunner

Pop lugs, not drugs
Joined
Oct 15, 2016
Messages
7,013
Reaction score
2,444
Location
Huntsville AL
Yes, I'm making tests with the OpenRocket tools, and it's not such a good rocket to construct.
Happy (or not) that I could surprise you.
Thanks for the explanation.
That rocket appears to break most of the underlying mathematical assumptions which OpenRocket uses for simulation of basic rocket flight.

As they say: Garbage in, Garbage out
 

JoePfeiffer

Well-Known Member
Joined
Jun 15, 2013
Messages
85
Reaction score
51
In this case, "exception" means it's getting an exception from the Java runtime system. In particular your yaw moment is going nuts (so your rocket is swinging side to side); the last value in for it in the simulation is about 10 to the 30th power.
Hmmm, if I run it under the development version it actually crashes the simulation. I'll need to look into that...
 
Last edited:

jrap330

Retired Engineer, NAR # 76940
TRF Supporter
Joined
Jan 25, 2020
Messages
420
Reaction score
116
Location
NJ
Hello, everybody. I was using OpenRocket and when I launched my rocket, this result was given. The acceleration suddenly started to increase and the simulation ended. This moment was marked as an flight event: exception.
Please help me to understand what is going on: what's the fhysical phenomenon behind it? Why did it heppen? Is it something bad? How should I try to resolve this?
.
.
.
.
.
Please forgive me if it's a trivial question :)
[/QUOTE
 
Top