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  #1  
Old 06-07-2009, 04:57 PM
blindeye2 blindeye2 is offline
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Posts: 28
Default Rocksim development suggestion

I would like to see added to the Simulation results listing
a calculated value of the delay required for max Altitude

Recovery system data
P: Parachute Deployed at : 7.554 Seconds
Velocity at deployment: 5.7303 ft/s
Altitude at deployment: 1525.78624 Ft.
Range at deployment: -55.29280 Ft.

Actual delay : 5 sec
Optimal delay: ? sec
Maxumum Altitude : ? ft

Given the the program knows the Velocity, Acceleration, & Altitude at deployment,
it should not be a difficult calculation to estimate the Optimal Delay for Max Altitude.

This would reduce the number of iterative simulations.

Just a thought
Bob
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  #2  
Old 06-07-2009, 07:34 PM
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CPMcGraw CPMcGraw is offline
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Quote:
Originally Posted by blindeye2
I would like to see added to the Simulation results listing
a calculated value of the delay required for max Altitude


Actually, it is available as one of the calculated data columns for simulations. It just has to be included in the list of displayed columns. I don't think it's included in the default list of columns, but it is available.

Menu path: EDIT | Preferences | Simulation Summary

Here's the list of available columns:
  • Simulation (Flight number in sequence)
  • Engines Loaded
  • Max Altitude
  • Max Velocity
  • Max Acceleration
  • Execution Time
  • Total Flight Time
  • Altitude At Deployment
  • Velocity At Deployment (This is our Dv number)
  • Optimal Delay (The optimal delay time for the engine selected)
  • Time To Apogee
  • Time To Launch Guide Departure
  • Time To Burnout
  • Velocity At Launch Guide Departure
  • Results
  • Comments (User notes for a given flight)
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  #3  
Old 06-08-2009, 03:59 PM
blindeye2 blindeye2 is offline
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Default Scaling Fins

I would be nice to be able to scale fins with seperate x and y direction
scale factors.

How hard would it be to be able to do simple math
in any of the value input fields:

Lenght: 18.000 * 1.5


Thanks;
Bob
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  #4  
Old 06-08-2009, 06:38 PM
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CPMcGraw CPMcGraw is offline
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Quote:
Originally Posted by blindeye2
I would be nice to be able to scale fins with seperate x and y direction
scale factors.

How hard would it be to be able to do simple math
in any of the value input fields:

Lenght: 18.000 * 1.5


Thanks;
Bob


In its current release, RockSim scales the fin plots in both 'X' and 'Y', but not individually. To do a one-directional scale-up, you'll have to generate all of the desired values manually and then change the plot points one at a time.

Now, if you're willing to do some programming work...

RockSim files are a form of XML, so the fin plot data would be a table of values contained between tags. The tags you would be looking for will start with: <Name>Fin Set</Name>, provided you have left the 'name' field with the default 'Fin Set'. If you have changed this name, then the string between the tags will be the name you gave it.

Then, you'll need to look for the plot points, <PointList>...</PointList>

It's saved in metric, not imperial, so be careful with the values. Math is math, so if you multiply the 'X' or 'Y' values by a given scale value, the results should still come out correctly.

If you can create a program that can read these values out of the XML, display the points, make the changes, and then save them back, that would be useful.

We have a few programmers here on YORF, so it's not out of the realm of possibility to accomplish this.
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  #5  
Old 06-09-2009, 01:13 AM
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Pyro Pro Pyro Pro is offline
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One of the little things that's been bugging me (I've been working on a Saturn 1B model, where this noticeably occurs, but it has come up in other cases too) is how RockSim handles fin placement over transitions. The fact that it can calculate the correct curvature for fin roots in these situations is nice for making patterns, but there are a few issues:

1) There isn't any way to turn off the feature that I can see, such as in the case of AMRAAM, where the rear fins overhang, but do not conform to, the boattail. I haven't tried using freeform fins for this yet, but from what I remember, it didn't help.

2) The conforming process seems to take one more iterative "step" after any other process. Ie, if a fin's position is set to a point there the conforming could be applied, it will remain unconformed until some other value (I usually add a bit to the span, then change it back) is adjusted, at which point it figures itself out. I've attached an example of what it looks like when this happens.

3) When the fins, even when owned by a body tube, are moved forward of that body tube onto a transition in front of that tube, they will conform to it, but instead of simply dropping an extended portion of the fin to do this, the entire front of the fin drops along the transition, while the rest of the fin is "cut" to fit what lies behind. This can be worked around with a bit of trig to compensate for how far the span is reduced, but my main issue is with the fact that RockSim will continue to print out the original fin span of the rocket, even when that span is noticeably reduced by the conforming process. As shown in the diagram, the rocket, with fins straight on the tube, has a span of 4". When the fins are moved forward, their effective span decreases, and yet the span is still, reportedly, 4". You can see that RockSim is still using the span assumption in the way it resizes the window (pictures 2 and 3 are shown at the same scale, even though picture 3 ought to be able to be zoomed in more due to the decreased span), and I worry that it would not be handling stability calculations correctly in these cases, if it is assuming a large fin span than is actually present.
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  #6  
Old 06-09-2009, 11:48 AM
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Quote:
Originally Posted by Pyro Pro
One of the little things that's been bugging me (I've been working on a Saturn 1B model, where this noticeably occurs, but it has come up in other cases too) is how RockSim handles fin placement over transitions. The fact that it can calculate the correct curvature for fin roots in these situations is nice for making patterns, but there are a few issues:

1) There isn't any way to turn off the feature that I can see, such as in the case of AMRAAM, where the rear fins overhang, but do not conform to, the boattail. I haven't tried using freeform fins for this yet, but from what I remember, it didn't help.

2) The conforming process seems to take one more iterative "step" after any other process. Ie, if a fin's position is set to a point there the conforming could be applied, it will remain unconformed until some other value (I usually add a bit to the span, then change it back) is adjusted, at which point it figures itself out. I've attached an example of what it looks like when this happens.

3) When the fins, even when owned by a body tube, are moved forward of that body tube onto a transition in front of that tube, they will conform to it, but instead of simply dropping an extended portion of the fin to do this, the entire front of the fin drops along the transition, while the rest of the fin is "cut" to fit what lies behind. This can be worked around with a bit of trig to compensate for how far the span is reduced, but my main issue is with the fact that RockSim will continue to print out the original fin span of the rocket, even when that span is noticeably reduced by the conforming process. As shown in the diagram, the rocket, with fins straight on the tube, has a span of 4". When the fins are moved forward, their effective span decreases, and yet the span is still, reportedly, 4". You can see that RockSim is still using the span assumption in the way it resizes the window (pictures 2 and 3 are shown at the same scale, even though picture 3 ought to be able to be zoomed in more due to the decreased span), and I worry that it would not be handling stability calculations correctly in these cases, if it is assuming a large fin span than is actually present.


David,

Items two and three are close to being bugs in the program, both in the calculation routine and in the rendering routine. I know they're using the Qt library for the GUI, but I don't know about the renderer. You probably should send Tim a note asking about what's happening.

Item one might be the addition of a simple button for toggling the contour feature in or out.
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  #7  
Old 06-10-2009, 11:53 AM
peter_stanley peter_stanley is offline
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Quote:
1) There isn't any way to turn off the feature that I can see, such as in the case of AMRAAM, where the rear fins overhang, but do not conform to, the boattail. I haven't tried using freeform fins for this yet, but from what I remember, it didn't help.

There is a work around for this. You edit plan-points, and leaving the first one, make another along the x axis to the right the distance of your overhang. This becomes your new (0,0) value. The other one is still there but you don't see it. Then adjust all the other points x-axis values that same difference. Not sure if I'm explaining it very well, but attached an example. It's in rocksim 9. If you have 8, try opening it anyway. Not sure if it will work but not using any features of 9 in this file. I know the work around works in both versions.
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  #8  
Old 06-10-2009, 01:21 PM
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Pyro Pro Pyro Pro is offline
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Yep, that's exactly what I had in mind, glad to see it works (when I did it before, on the AMRAAM (maybe 1-2 years ago), the fins had to be freeform anyway [to model the step on the leading edge], but I still had the root edge as a single piece). That's a neat design, by the way.


I thought of something else. Is it just me, or does RockSim start in windowed mode (albeit, the window is as large as it can be) for everyone? I compulsively maximize it on startup, but it would be nice if it just started that way (perhaps an option on one of the setting pages "Start windowed" [check on/off]).
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  #9  
Old 07-04-2009, 09:56 AM
blindeye2 blindeye2 is offline
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Default Ouputing fin points

It would be nice if there were an option to output fin point pairs to a file.
It would be nice if you were able to copy the point pairs and past them into a spread sheet. It is tedious to copy them coordinate by coordinate even for very simple fin design.
This is usefull for keeping the fins shape, but just want to scale or shift in one direction.
Bob
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