Virtual Contest Reunion - New Prizes....

[EMRR]

I have uploaded all the new prizes available from our sponsors. Thank them by buying from them - AND - by participating in the Reunion.

So far it is looking to be a nice turn out of a lot of previous participants (guys, try to convince Dick Stafford to play) and currently four newbies.

I need help finding some of the folks (not marked with a (P)) and welcome all new comers as well!

Whether you can or can't participate, but still want to support EMRR, then you may contribute a prize to this contest. That will count toward the 2005 EMRR Challenge item #1.

So, check out the contest HERE

Nick

 

[teflonrocketry1]

Originally posted by EMRR
I need help finding some of the folks (not marked with a (P))

Nick,

Can't you get all the e-mail addresses off of the EMRR Yahoo group? I have moderator priviledges on my NAR Sections Yahoo group and I can view all the members e-mail addresses.

Why won't Dick Stafford participate? Did I send him too many RockSim files?

Bruce S. Levison, NAR #69055

 

[rstaff3]

Bah humbug. I spent sooo much time on the first few contests, only to fail miserably

 

[SwingWing]

Originally posted by rstaff3
Bah humbug. I spent sooo much time on the first few contests, only to fail miserably

See, this Virtual stuff really IS like real rocketry......

 

[EMRR]

Originally posted by teflonrocketry1
Nick,

Can't you get all the e-mail addresses off of the EMRR Yahoo group? I have moderator priviledges on my NAR Sections Yahoo group and I can view all the members e-mail addresses.

Why won't Dick Stafford participate? Did I send him too many RockSim files?

Bruce S. Levison, NAR #69055

Some people have dropped over the past several years. Some don't put their name associated with their e-mail, etc. I don't save e-mail addresses except for those I communicate with often.

Thanks for the idea though. I'm trying to reach everyone by searching RMR and TRF and Google, however, some folks have just vanished...

 

[EMRR]

Originally posted by rstaff3
Bah humbug. I spent sooo much time on the first few contests, only to fail miserably

Consider it an act of kindness... if you participate, then someone else will place higher

 

[BobCox]

I turned in my entry two weeks ago and it looks like nobody has submitted anything since then. C'mon, 9 prizes and 15 entries? Those look like pretty good odds.

 

[teflonrocketry1]

Originally posted by rstaff3
Bah humbug. I spent sooo much time on the first few contests, only to fail miserably

Dick,

I have created a few RockSim files and I still haven't managed to come in first yet. These contests aren't easy, just do it for the challenge! I did it for the challenge; there were only two prizes offered when I sent in my design. Since the odds are so good you might want to give it a shot; there are some really great prizes to be had.

Bruce S. Levison, NAR #69055

 

[EMRR]

Virtual Rocket Contest Reunion -

Entries are due by 9/4. There are still (7) folks that said they would participate and have not (+ Stafford <grin>). Let's get them in, we are wrapping up and starting to get ready for the flying portion of the contest.

Virtual Contest

- Nick

 

[BobCox]

It looks like the latest EMRR Virtual Rocket Contest has set a record for participation -- 27 entries, including 7 newbies.

Four people got bonus points for building and/or flying their designs. Bruce Levison has an especially interesting fin-less design called Twin Boomer. I wonder how it will fly in Virtual World.

Nick is teasing us by posting the names but not the pictures. I must say I don't care much for the name of Chan Stevens' entry.

 

[teflonrocketry1]

Bob,

I only spent a few hours on the Twin-Boomer design; it is a modification of a rack-rocket design I was working on at the time. Essentially, I took off the flat fins and included a ring fin which also doubles as a body tube. The two long thin "booms" are structural body tubes as well as tube fins, and also serve as launch lugs! The design flies stable in the real world. The awesome picture of the launch was taken by my wife Debbie; you can even see the lettering on the rockets home made decal and the drop away boom for the ignitor wires. I lost the nosecone and parachute on that flight (this designs third) the anchor in the nose cone broke away. There were some minor scratches in the paint on the body tubes. I put a new nose cone on but left it unpainted (white), so I could display the Twin-Boomer at the 2005 Cleveland National Air Show this past Monday.

I tried to take a picture of the Twin-Boomer in flight the first two times I flew the design. I did this by myself since the design was unproven. I did manage to get the smoke trail on the second flight off the pad but I found it extremely difficult to launch and photgraph the rocket in flight and then recover it! On the second launch after quite a few pictures of just clouds, I finally got one that just showed the tail section at the extreme edge of the picture while the rocket was still in the air. See the attached .jpg.

Recently I figured out that RockSim over estimates the drag on ring finned designs. See the following thread:

https://www.rocketryforum.com/showthread.php?s=&threadid=20058

Because of this flaw in the software, I doubt I can win this contest. I wonder what the other designs look like, especially Bob's Retribution of Zeus.

Bruce S. Levison, NAR #69055

 

[chanstevens]

Originally posted by BobCox
I must say I don't care much for the name of Chan Stevens' entry.

Bob:

It's kind of hard to tell, but it's based on George Gassaway's "Sunchaser" design flown so breathtakingly at NARAM (had some type of solar sensor and active guidance so that the bird constantly adjusted and flew directly towards the sun). In my case, I have a gizmo that detects lightning bolts and heads directly towards them. It was developed by the same lab that came up with my negative drag fin design...

--Chan Stevens

 

[teflonrocketry1]

Bob,

Your design is also a lightweight rack-rocket! I wonder if my design is efficient enough to beat out some of the others like yours. There appears to be several other designs with tube or ring fins which is a new feature of RockSim version 8. It also looks like I am one of maybe three who used the Texture feature of the software to color their virtual design. I painted the Twin-Boomer model I built to match the color scheme and decal from the simulation file I created.

Bruce S. Levison, NAR #69055

 

[BobCox]

Originally posted by teflonrocketry1
It also looks like I am one of maybe three who used the Texture feature of the software to color their virtual design. I painted the Twin-Boomer model I built to match the color scheme and decal from the simulation file I created.

I like the decals on yours, Bruce. I think 'Da Hip Chicken' made the best use of the texturing feature. Then again, I'm kind of biased since that is my daughter's entry.

 

[PunkRocketScience]

Hmmm... I sent my decal files in to Nick, but I guess he must have had some problem with them, as they aren't on my model.

Ah well, having run one of these contests before, I won't quibble. I ran a smaller field than this and it was a HUGE amount of work... I can only imagine what a field of 27 would take to run (along with working and moving...)

Great designs people! I don't think mine will fare very well as it is somewhat big and heavy compared to the others...

 

[ccoffin]

Wow!

These results are very interesting. I didn't think the models would be simulated with such a high power motor. Looks like a lot of the rockets didn't hold up on M power. I am surprised mine held up actually, since in the real world, a 24mm M900 (if it existed) surely would have shreaded it.

I really thought that i would be on the heavy side compared to the others. I'm not even close... oh well.

Way to go Chan! Very solid performance!

 

[the freshman]

A 24mm M900?!! I don't think any of us saw that one coming. Looking at the flight results with the M, it's a good lesson in optimal mass.

 

[chanstevens]

Originally posted by ccoffin
Wow!

These results are very interesting. I didn't think the models would be simulated with such a high power motor. Looks like a lot of the rockets didn't hold up on M power. I am surprised mine held up actually, since in the real world, a 24mm M900 (if it existed) surely would have shreaded it.

I really thought that i would be on the heavy side compared to the others. I'm not even close... oh well.

Way to go Chan! Very solid performance!

Early results can be misleading--I was trying to max out in events 1 & 2, figuring a heavy but low drag design would benefit from the scoring methods. That proved out--featherweights got creamed. I'll get my due in the low & slow...

I'm curious how so many could fail on the M, given they had to be stable on the E9 to qualify. If using FinSim, none of the designs would make it.

To me the biggest surprise is the early deficit Zeus is facing. Getting beat by his own daughter?

--Chan Stevens

 

[BobCox]

Originally posted by chanstevens
Early results can be misleading--I was trying to max out in events 1 & 2, figuring a heavy but low drag design would benefit from the scoring methods. That proved out--featherweights got creamed. I'll get my due in the low & slow...

Wow, did I guess wrong on the strategy. I was going for ultra-light and low drag to get max alititude. I did pretty well on the altitude, but my weighted score was awful. Last place on all three flights -- ugh!

I'm curious how so many could fail on the M, given they had to be stable on the E9 to qualify. If using FinSim, none of the designs would make it....

That's not aerodynamic instability, it is numerical instability in the RockSim simulation. Under extreme accelerations, some of the calculations exceed the range that their variables can handle, and the results suddenly change sign. Once that happens, game over.

I sent Nick a PM about this.

To me the biggest surprise is the early deficit Zeus is facing. Getting beat by his own daughter?

I'm hanging my head in shame.

Getting beat by his own daughter?

You can be sure that she is rubbing it in my face, too!

 

[EMRR]

TRF won't send me UPDATES on threads anymore! Software bug... bah-hum-bug!

There, now that is said...

I'm missed all these comments. I'll catch up and try to fix the decals (Todd).

Bob pointed out a bug in RockSIM and I just thought is was really good calculations... some rockets being unstable with the M900.

Anyhow, I have posted a note that I need to re-run the M900's with a higher sample rate. That will change the rankings.

I will do that in them morning.

In the mean time, Event #2 is posted.

Nick

 

[EMRR]

Events 1-3 posted with event 1 correct.

Have not fixed Mullin's decals.

Out of time... gotta go!

Nick

 

[EMRR]

Originally posted by teflonrocketry1
Recently I figured out that RockSim over estimates the drag on ring finned designs. See the following thread:

Bruce S. Levison, NAR #69055

That is proving true in VC#8, isn't it? It really shocked me and expected better results.

Here's an experiment for you. Add two small fins inside the tubes to see what that does for drag.

Nick

 

[BobCox]

Oh man, this is just plain embarrassing. Last place in Event 3, 2nd to last in Event 1. Oh, how the mighty have fallen.


It looks like a real dog-fight for the top few spots, though. The drag race results should be interesting.

 

[chanstevens]

Originally posted by BobCox
It looks like a real dog-fight for the top few spots, though. The drag race results should be interesting.

How can there be a dog fight without the Red Baron (of Zeus)? With blind motor selections, this one was pretty much a crap shoot, so other than getting beat by your daughter, which you've avoided so far, I wouldn't sweat it.

I just looked over the scoring and rules at the beginning and figured the typical ultra-light design would get roughed up. Remember--those ultra-light materials weigh the same as the heavy birds in event 2, and in event 1 I think ounces times feet favors slightly the heavier designs. I basically flew the same design as contest #1, just tweaked for a bit more weight and a bit lower drag.

Oh yeah--I also learned how to look for the best motors for drag races, after getting the [poop] zapped out of me by a few lighting bolts in the early contests. Seeing all the F72's out there, I'd agree that the drag races are going to have some incredibly close rod clearance times, which in my view has always been the key to winning that event.

 

[PunkRocketScience]

My rocket looks oh so much more spiffy with it's decals on!

 

[PunkRocketScience]

Sorry to post two in a row here... I was just taking a peek at the results from event #1... What a huge margin between my end of the field and the high end! Nick/Bob/Bruce or any other rocksim whiz.... whereas I realize that there would be some variation in the flights, would you care to speculate why there would be such a enormous range even in the non-adjusted altitudes? I find it interesting that with the variation in weights was only a few ounces and the immense thrust of a M class motor that the differences would be so great.

These are NOT complaints from a sore-loser!!! I want to make that VERY clear. I am NOT disputing the results...I'm just interested in how/what/why....

 

[chanstevens]

Todd:

Without the files, I'm only guessing here but I'd say comparing your design to Layne's (similar weight, very different design), your rocket suffers badly from body drag. Like a SuperRoc, long/slender body without any transitions leads to high drag/low performance. Believe it or not, some of the lowest drag designs out there are basic egg lofters, with capsule at the top and a tapered shroud down to minimum diameter motor tube. Even the basic "egg on a stick" designs are low drag thanks to the cone acting as a transition over the first part of the body.

Try going one or two sizes larger on your lower body tube, with about a 1" transition/boattail DOWN to your motor mount at the aft end. I'll bet you get something like a 20-25% improvement in your altitude.

Note--this is based on real rocketry, not RockSim. I don't pretend to be a RockSimScientist, just lucking out in a few VC's thanks to optimizing for the events/scoring and, of course, the discovery of negative drag fins.

--Chan Stevens

 

[BobCox]

Originally posted by RocketmanTM
I was just taking a peek at the results from event #1... What a huge margin between my end of the field and the high end! Nick/Bob/Bruce or any other rocksim whiz.... whereas I realize that there would be some variation in the flights, would you care to speculate why there would be such a enormous range even in the non-adjusted altitudes? I find it interesting that with the variation in weights was only a few ounces and the immense thrust of a M class motor that the differences would be so great.B]

I did not want to keep pestering Nick about it since he is pretty busy with his real life, but since you brought it up...

I spotted that, too, and pointed it out to Nick in a PM.

The spread on the rocket weights is about 15:1. The spread on the C11 altitudes is about 7:1. On the E6 alititude, the range is about 4:1. There is no way that the spread on the M900 altitudes should be over 150,000:1. That is a flaw in the way RockSim calculates the flights, not the way the rocket were designed.
----------------------
I've seen situations similar to what you show, and the instability is not aerodynamic, it is numerical. Sometimes increasing the simulation rate from 800 to 2000 samples/sec solves it. If the instability was aerodynamic, that would make no difference.

If you single-step through the flight profile with the flight profile details enabled, it will show that something hinkey is going on just before it goes unstable. For example, the static stability margin gradually changes from 5 to 10 as the fuel is consumed, then suddenly changes to >100 in 0.02 seconds. Watch the angular acceleration as it goes crazy and changes sign abruptly. There are several other variables that do the same thing.

Based on this, Nick re-ran the simulations with a higher sample rate (2000 vs 800). Several of the flights cleaned up, so the range betwen high and low is only 1255:1, an improvement of more than 100x. However, there are still many flights that look screwy to me. (Basically, I am suspicious of any flight that did not reach 10,000,000 feet.) I have not seen the actual flight profiles so I cannot say with certainty that that is the problem, but my gut says that many flight simulations are still numerically (not aerodynamically) unstable.

 

[BobCox]

Originally posted by chanstevens
Without the files, I'm only guessing here but I'd say comparing your design to Layne's (similar weight, very different design), your rocket suffers badly from body drag.

I believe Chan is right for the C11 and E6 flights, but I believe the huge range in the M900 results is the result of numerical instability in the calculations.

When I plotted the altitude vs. weight, the C11 and E6 flights show a basic trend that lighter weight generally leads to higher altitude, and the data fits to a downward-sloping line. Any deviation from that line is probably caused by differences in drag. For example, both of Bruce Levison's flights are well below the line and Jeff Lane's is well above the line, but just about everybody else fits in a fairly narrow band along the line.

On the other hand, most of the M900 flights have a similar curve, but there are ten flights (all below 10M feet) that are completely out of whack with the rest of the M900 flights and are not correlated to the flight results for those same rockets on smaller engines. I suspect these are still having numerical stability problems in the simulations.


(As a separate topic, the ones that lie farthest off the line used a ring fin and tube fins. I think RockSim 8 does a poor job of modeling the drag of ring fins and the stability of tube fins. Bruce and I have discussed this in other TRF threads. I have much more trust in the "Levison Method" of simulating tube fins.)

 

[EMRR]

Check out the latest update...

Let event #1 go... sorry, but I need to move on...

Regards,
Nick