RockSIM 6.x bugs and work-arounds

RockSIM 6.x bugs and work-arounds

Post by EMR » Fri, 30 May 2003 15:37:28



Since we are starting to get entries for our 2nd Virtual Rocket
Contest, I've discovered two bugs in RockSim 6.x.  I also have two
work arounds:

Cluster Motor Problem: I specified a core motor tube, and then six
other tubes around it using the cluster wizard. They are all selected
as motor tubes, and they are all 29mm. However, when I go to load a
motor, it won't let me load the first tube on the list. If I use the
load all function, it will load properly, but if I wanted to do a
combination of different motors (e.g. H220T -> 2x H210R -> 2x I200W ->
2x G38BM), it won't let me. (note: this was how it was specific on
TRF)

Fix: I went in and edited your design. I deleted all the motor tubes.
I then created an inside tube, used LOC 1.14 5" long and marked it
29mm as motor tube. I then saved that component. I exited and selected
that tube and selected cluster wizard. Choose the 6 around pattern
(notice it does not leave one in the middle). I then added a new
center inside tube as a 29mm motor mount and they all worked and
loaded fine. I did nothing with component name changing.

2-Stage Problem: When editing a two-stage, going from booster to
sustainer makes the sustainer parts loose their data.  In other words,
open rocket for editing, start on booster fins, then go to sustainer
body tube, the sustainer will loose all length, location, etc.
information and come out and be on a no name component.

Fix: From the main viewer screen, select the 2-stage button, then go
in and edit only the booster stage.  Come back out.  From the main
viewer screen, then select the 1-stage button.  Go in and edit only
the sustainer.

http://www.rocketreviews.com/virtual_contest2.shtml

-Nick

 
 
 

RockSIM 6.x bugs and work-arounds

Post by AlMax7 » Fri, 30 May 2003 21:49:01


I noticed a funny problem ? (or feautre I don't understand)

I will fly a loc-iv on a g40-4. it will say optimum delay is 4.65
seconds.

I will then fly it on a g-40-10. it will say optimum delay is 7.65
seconds.

this anomily is the same for jsut about everthing I fly, a short
delay, a short optimum time. A long delay  , a longer optimum time.

Anyone know what I'm doing wrong ?

 
 
 

RockSIM 6.x bugs and work-arounds

Post by Jerry Irvin » Fri, 30 May 2003 22:36:06



Quote:

> I noticed a funny problem ? (or feautre I don't understand)

> I will fly a loc-iv on a g40-4. it will say optimum delay is 4.65
> seconds.

> I will then fly it on a g-40-10. it will say optimum delay is 7.65
> seconds.

> this anomily is the same for jsut about everthing I fly, a short
> delay, a short optimum time. A long delay  , a longer optimum time.

> Anyone know what I'm doing wrong ?

That is strange indeed.  Sounds like an obvious programming bug to me.

Jerry

--
Jerry Irvine, Box 1242, Claremont, California 91711 USA

Please bring common sense back to rocketry administration.
Produce then publish.  http://www.usrockets.com

 
 
 

RockSIM 6.x bugs and work-arounds

Post by Rick Dickinso » Fri, 30 May 2003 23:20:03



Quote:
>I noticed a funny problem ? (or feautre I don't understand)

>I will fly a loc-iv on a g40-4. it will say optimum delay is 4.65
>seconds.

>I will then fly it on a g-40-10. it will say optimum delay is 7.65
>seconds.

>this anomily is the same for jsut about everthing I fly, a short
>delay, a short optimum time. A long delay  , a longer optimum time.

>Anyone know what I'm doing wrong ?

I think that, if you select a specific delay, it *stops* simulating
when the delay finishes.  So, if you select a delay that is shorter
than the coast-time-to-apogee, the rocket is still moving fast, but
slowing down, at the end of the simulation.

"Best" delay time seems to be picked by looking for the time when the
rocket is moving the slowest.  For a sim that stops before apogee,
this will always be right at the end of the delay.

I haven't looked, but I'll bet you find that the G40-4 has a delay
time of 4.65 seconds in the .eng file you are using.

It's simply picking the "best" delay time *out of the values it
calculated*.

 - Rick "But, yes, I'd still consider it a bug"***inson

--
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mathematicians for ongoing projects in communications research.
If you are interested and would like a brochure, just pick up
your phone and call anybody.

 
 
 

RockSIM 6.x bugs and work-arounds

Post by Doug Sam » Fri, 30 May 2003 23:48:27


Quote:

> I noticed a funny problem ? (or feautre I don't understand)

> I will fly a loc-iv on a g40-4. it will say optimum delay is 4.65
> seconds.

> I will then fly it on a g-40-10. it will say optimum delay is 7.65
> seconds.

> this anomily is the same for jsut about everthing I fly, a short
> delay, a short optimum time. A long delay  , a longer optimum time.

> Anyone know what I'm doing wrong ?

While there are some bugs in Rocksim, this isn't one. I had
to get this same question answered a while back.

While you might assume the optimum delay is based on when the
rocket reaches apogee without deployment, the actual method
simply looks at the actual (well, simmed) flight (with deployment)
and determines when apogee occurs.

With the short delay (-4), it is still moving up
quite fast at deployment, so it will continue to coast upward
under (above) the chute until it reaches apogee, where the
optimum delay is then established - ie, 4 secs plus coast time.

The best way to use the feature is to simply enter a very long
delay (when you select the motor), then see what it calculates
for optimum delay.  Basically, in this case, any number 7.65
or greater should return 7.65 secs as optimum.

HTH,
Doug

--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG

 
 
 

RockSIM 6.x bugs and work-arounds

Post by Larry W. Hardi » Fri, 30 May 2003 23:57:51


Strange... I ran the LOC-4 (don't know where I picked up the
file) and got an optimum delay of 6.10 seconds when I ran both
G40-7 and G40-10.  There was no G40-4 in the list.

Larry

Quote:

> I noticed a funny problem ? (or feautre I don't understand)

> I will fly a loc-iv on a g40-4. it will say optimum delay is 4.65
> seconds.

> I will then fly it on a g-40-10. it will say optimum delay is 7.65
> seconds.

> this anomily is the same for jsut about everthing I fly, a short
> delay, a short optimum time. A long delay  , a longer optimum time.

> Anyone know what I'm doing wrong ?

 
 
 

RockSIM 6.x bugs and work-arounds

Post by Bob Kapl » Sat, 31 May 2003 02:47:15


Quote:

> I noticed a funny problem ? (or feautre I don't understand)

> I will fly a loc-iv on a g40-4. it will say optimum delay is 4.65
> seconds.

> I will then fly it on a g-40-10. it will say optimum delay is 7.65
> seconds.

> this anomily is the same for jsut about everthing I fly, a short
> delay, a short optimum time. A long delay  , a longer optimum time.

> Anyone know what I'm doing wrong ?

While I can't speak for RockSim, you definitely want the -4 for a LOC-IV.

        Bob Kaplow      NAR # 18L       TRA # "Impeach the TRA BoD"
                >>> To reply, remove the TRABoD! <<<
Kaplow Klips & Baffle:      http://www.pleimling.org/le/Phantom4000.pdf
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RockSIM 6.x bugs and work-arounds

Post by Bob Kapl » Sat, 31 May 2003 02:56:30


Quote:


>>I noticed a funny problem ? (or feautre I don't understand)

>>I will fly a loc-iv on a g40-4. it will say optimum delay is 4.65
>>seconds.

>>I will then fly it on a g-40-10. it will say optimum delay is 7.65
>>seconds.

>>this anomily is the same for jsut about everthing I fly, a short
>>delay, a short optimum time. A long delay  , a longer optimum time.

>>Anyone know what I'm doing wrong ?

> I think that, if you select a specific delay, it *stops* simulating
> when the delay finishes.  So, if you select a delay that is shorter
> than the coast-time-to-apogee, the rocket is still moving fast, but
> slowing down, at the end of the simulation.

> "Best" delay time seems to be picked by looking for the time when the
> rocket is moving the slowest.  For a sim that stops before apogee,
> this will always be right at the end of the delay.

> I haven't looked, but I'll bet you find that the G40-4 has a delay
> time of 4.65 seconds in the .eng file you are using.

> It's simply picking the "best" delay time *out of the values it
> calculated*.

>  - Rick "But, yes, I'd still consider it a bug"***inson

Again, I don't know nuttin 'bout RockSim, but a LOC-IV will reach apogee
LONG before 7.65 seconds. The 4.65 number sounds close: I calculated about
4.4, but it depends on what you pick for the mass and CD which the original
poster didn't specify.

        Bob Kaplow      NAR # 18L       TRA # "Impeach the TRA BoD"
                >>> To reply, remove the TRABoD! <<<
Kaplow Klips & Baffle:      http://www.FoundCollection.com/
    www.encompasserve.org/~kaplow_r/    www.nira-rocketry.org    www.nar.org

 Save Model Rocketry from the HSA!   http://www.FoundCollection.com/

 
 
 

RockSIM 6.x bugs and work-arounds

Post by Bob Kapl » Sat, 31 May 2003 02:57:35



Quote:
> The best way to use the feature is to simply enter a very long
> delay (when you select the motor), then see what it calculates
> for optimum delay.  Basically, in this case, any number 7.65
> or greater should return 7.65 secs as optimum.

If RockSim thinks that a LOC-IV with a G40 is still coasting upward at 7.65
seconds, then there IS a problem here...

        Bob Kaplow      NAR # 18L       TRA # "Impeach the TRA BoD"
                >>> To reply, remove the TRABoD! <<<
Kaplow Klips & Baffle:      http://www.pleimling.org/le/Phantom4000.pdf
    www.encompasserve.org/~kaplow_r/    www.nira-rocketry.org    www.nar.org

 Save Model Rocketry from the HSA!   http://www.space-rockets.com/congress.html

 
 
 

RockSIM 6.x bugs and work-arounds

Post by Bob Kapl » Sat, 31 May 2003 03:00:44



Quote:
> Strange... I ran the LOC-4 (don't know where I picked up the
> file) and got an optimum delay of 6.10 seconds when I ran both
> G40-7 and G40-10.  There was no G40-4 in the list.

Even 6.something sounds long to me. More like 4.something...

        Bob Kaplow      NAR # 18L       TRA # "Impeach the TRA BoD"
                >>> To reply, remove the TRABoD! <<<
Kaplow Klips & Baffle:      http://www.pleimling.org/le/Phantom4000.pdf
    www.encompasserve.org/~kaplow_r/    www.nira-rocketry.org    www.nar.org

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RockSIM 6.x bugs and work-arounds

Post by Doug Sam » Sat, 31 May 2003 03:09:06


Quote:

> If RockSim thinks that a LOC-IV
> with a G40 is still coasting upward
> at 7.65 seconds, then there IS a problem
> here...

Hi, Bob,

I don't know the LOC-IV off the top of my head,
but I've see this optimum delay phenomenon with
Rocsim before.

As for Rocsim's accuracy, I've found it to be a
useful tool.  But being a longtime user of
computer simulation tools, I've developed some
instinct for knowing when to trust them and
knowing when to pad, and which way to pad :)

Doug

--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG

 
 
 

RockSIM 6.x bugs and work-arounds

Post by Eric Ellingto » Sat, 31 May 2003 03:20:50


Quote:



>>>I noticed a funny problem ? (or feautre I don't understand)

>>>I will fly a loc-iv on a g40-4. it will say optimum delay is 4.65
>>>seconds.

>>>I will then fly it on a g-40-10. it will say optimum delay is 7.65
>>>seconds.

>>>this anomily is the same for jsut about everthing I fly, a short
>>>delay, a short optimum time. A long delay  , a longer optimum time.

>>>Anyone know what I'm doing wrong ?

>>I think that, if you select a specific delay, it *stops* simulating
>>when the delay finishes.  So, if you select a delay that is shorter
>>than the coast-time-to-apogee, the rocket is still moving fast, but
>>slowing down, at the end of the simulation.

>>"Best" delay time seems to be picked by looking for the time when the
>>rocket is moving the slowest.  For a sim that stops before apogee,
>>this will always be right at the end of the delay.

>>I haven't looked, but I'll bet you find that the G40-4 has a delay
>>time of 4.65 seconds in the .eng file you are using.

>>It's simply picking the "best" delay time *out of the values it
>>calculated*.

>> - Rick "But, yes, I'd still consider it a bug"***inson

> Again, I don't know nuttin 'bout RockSim, but a LOC-IV will reach apogee
> LONG before 7.65 seconds. The 4.65 number sounds close: I calculated about
> 4.4, but it depends on what you pick for the mass and CD which the original
> poster didn't specify.

RockSim calculates a pretty low Cd for a LOC-IV, around 0.29. wRASP uses
0.60 by default. The real Cd is probably somewhere in the middle,
depending upon building techniques, finish, etc.
 
 
 

RockSIM 6.x bugs and work-arounds

Post by Bob Kapl » Sat, 31 May 2003 03:37:48



Quote:
> I don't know the LOC-IV off the top of my head,

Probably the most popular L1 cert rocket. 4" diameter 3FNC with a 29mm MMT.

Quote:
> As for Rocsim's accuracy, I've found it to be a
> useful tool.  But being a longtime user of
> computer simulation tools, I've developed some
> instinct for knowing when to trust them and
> knowing when to pad, and which way to pad :)

True of ANY simulation tool. If you don't know about what result to expect,
you don't know when it's telling you garbage.

GIGO!

        Bob Kaplow      NAR # 18L       TRA # "Impeach the TRA BoD"
                >>> To reply, remove the TRABoD! <<<
Kaplow Klips & Baffle:      http://www.pleimling.org/le/Phantom4000.pdf
    www.encompasserve.org/~kaplow_r/    www.nira-rocketry.org    www.nar.org

 Save Model Rocketry from the HSA!   http://www.space-rockets.com/congress.html

 
 
 

RockSIM 6.x bugs and work-arounds

Post by Bob Kapl » Sat, 31 May 2003 03:39:06


Quote:

> RockSim calculates a pretty low Cd for a LOC-IV, around 0.29. wRASP uses
> 0.60 by default. The real Cd is probably somewhere in the middle,
> depending upon building techniques, finish, etc.

That's just absurd for this rocket! I'd go with something in the 0.6-0.8
range depending on construction and finish.

        Bob Kaplow      NAR # 18L       TRA # "Impeach the TRA BoD"
                >>> To reply, remove the TRABoD! <<<
Kaplow Klips & Baffle:      http://www.pleimling.org/le/Phantom4000.pdf
    www.encompasserve.org/~kaplow_r/    www.nira-rocketry.org    www.nar.org

 Save Model Rocketry from the HSA!   http://www.space-rockets.com/congress.html

 
 
 

RockSIM 6.x bugs and work-arounds

Post by Jerry Irvin » Sat, 31 May 2003 03:54:27


In article


Quote:

> > I noticed a funny problem ? (or feautre I don't understand)

> > I will fly a loc-iv on a g40-4. it will say optimum delay is 4.65
> > seconds.

> > I will then fly it on a g-40-10. it will say optimum delay is 7.65
> > seconds.

> > this anomily is the same for jsut about everthing I fly, a short
> > delay, a short optimum time. A long delay  , a longer optimum time.

> > Anyone know what I'm doing wrong ?

> While there are some bugs in Rocksim, this isn't one. I had
> to get this same question answered a while back.

> While you might assume the optimum delay is based on when the
> rocket reaches apogee without deployment, the actual method
> simply looks at the actual (well, simmed) flight (with deployment)
> and determines when apogee occurs.

> With the short delay (-4), it is still moving up
> quite fast at deployment, so it will continue to coast upward
> under (above) the chute until it reaches apogee, where the
> optimum delay is then established - ie, 4 secs plus coast time.

> The best way to use the feature is to simply enter a very long
> delay (when you select the motor), then see what it calculates
> for optimum delay.  Basically, in this case, any number 7.65
> or greater should return 7.65 secs as optimum.

> HTH,
> Doug

So it needs an early ejection warning so the user does not perceive a
bug that does not exist.

Jerry

--
Jerry Irvine, Box 1242, Claremont, California 91711 USA

Please bring common sense back to rocketry administration.
Produce then publish.  http://www.usrockets.com