The 6th Observable

[Dotini]

If that were true... most real finned rockets would have ring fins.

My theory as to why the simulation shows a lower altitude than your altimeter showed during actual flights is that the actual motor thrust is higher than the thrust used in Open Rocket. If you look at the spec's, motor thrusts can vary by a pretty wide margin.

Most "real" rockets are not on the same scale of size and speed as our model rockets. Thus, the Reynolds numbers are incommensurable.

But, as you say, Estes model rocket engines can and do have disturbingly variable operating characteristics.

You have a choice to make. Either build and test your own model and drive towards reconciling its anomalous performance with accepted wisdom, or write the whole business off as a misidentification of the planet Venus, and double down on what the authority figures tell you to think.

 

[lakeroadster]

Most "real" rockets are not on the same scale of size and speed as our model rockets. Thus, the Reynolds numbers are incommensurable.

But, as you say, Estes model rocket engines can and do have disturbingly variable operating characteristics.

You have a choice to make. Either build and test your own model and drive towards reconciling its anomalous performance with accepted wisdom, or write the whole business off as a misidentification of the planet Venus, and double down on what the authority figures tell you to think.

Ok, then, I'll modify my previous comment..

Conjecture: This ring fin gathers up detached or turbulent flow, reconnecting it as more laminar flow, thus greatly reducing drag.

If that were true... all model rockets that are built for maximum altitude would have ring fins.

I guess it's possible that you've stumbled upon a phenomenon previously unknown to model rocketeers... but I'm thinking that's not the case.

 

[Dotini]

Ok, then, I'll modify my previous comment..



If that were true... all model rockets that are built for maximum altitude would have ring fins.

I guess it's possible that you've stumbled upon a phenomenon previously unknown to model rocketeers... but I'm thinking that's not the case.

You are saying that one anomalous launch doesn't mean anything. Especially if it violates a computer sim. Agreed! Now, what does your sim say is the altitude my model should reach with the ring installed?

How many flights significantly above that figure would it take to convince you and @neil_w that the cause is not an anomalous Estes motor? Would three suffice?

To paraphrase Ian Fleming; "Once is happenstance. Twice is coincidence. The third time it's enemy action."
In other words, if I can prove to you it's not defective motors, then you'll know there are bugs running loose on your sim.

 

[lakeroadster]

You are saying that one anomalous launch doesn't mean anything. Especially if it violates a sacred computer sim. Agreed! Now, what does your precious say is the altitude my model should reach with the ring installed??

How many flights significantly above that sacrosanct figure would it take to convince you and @neil_w that the cause is not an anomalous Estes motor? Would three suffice? How about 30? Must I do 300?

To paraphrase Ian Fleming; "Once is happenstance. Twice is coincidence. The third time it's enemy action."
In other words, if I can prove to you it's not defective motors, then you'll know there are bugs running loose on your sim and maybe even in your mind.

Have a great day.

 

[neil_w]

How many flights significantly above that figure would it take to convince you and @neil_w that the cause is not an anomalous Estes motor? Would three suffice?

Hey, how did I get dragged into this?

To be sure, it is always interesting if observed flight behavior diverges significantly from the sim, especially when it comes to tail rings. Basically, we have that one POF article which everyone pretty much takes as gospel it seems (and I assume that's the model that's built into Rocksim). If there's a problem in the sim algorithm, it is good to know about it and fix it. I don't believe a new low-drag tail ring configuration has been discovered, but I also don't have blind trust in the sim with regard to tail rings. I actually use my own home-made methodology, and haven't the slightest idea if it's accurate. It is soothingly intuitive so I'll stick with it until it leads me astray.

 

[Dotini]

On 7/27/21 under conditions of light wind at Dahl field, a flight was made of the the 6th Observable with the following notes:
1) Motor C11-3
2) Altitude, altimeter, 319'
2b) Altitude calculated, 288'
3) Descent duration 17 seconds, 25 fps - chute did not fully deploy
4) Landing, somewhat horizontal, no damage
5) Video, 28 seconds, fair quality

Comment: Flight did not live up to expectation set by first flight of 492' calculated altitude on launch earlier in July. Speculated reasons include different atmospheric conditions, variability of motors, additional weight of rocket due to altimeter and packaging.