Thrustcurve Open Thread

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JohnCoker

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I went through and updated the 38mm Loki reloads this morning. Now the delays on ThrustCurve.org match what's in the individual instruction sheets.
 

smstachwick

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Hey there!

Not sure if this is the right place to put this, but I've confirmed via Aerotech's Master Motor Matrix, updated 8/24/21, that the E15W has gone out of production. Availability on the site is still listed as regular. Is this because of a recent discontinuation (and theoretically still some stock possibly lying around) or is that an error?

Side note: I've found the site really useful so far for planning some future fights, thank you @JohnCoker for taking the time to create it and keep it updated.
 

neil_w

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For a while the E15 and E20 have been the same motor (perhaps someone from AT can explain how this came to be). So the E15 has ended, but the E20 continues.

I love this motor.
 

smstachwick

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Oh, good to know. Yeah, I've been running Goblin simulations in RockSim using every 24 x ~70mm motor in the book and that airframe is an impressive performer with the E20. I'm getting estimates in the range of 2400 ft for that little rocket. And Thrustcurve is a great resource

I have, however, noticed a few things that don't line up with the certification documents and information from the manufacturers' websites. Is this thread a good place to pose questions about these or would comments on the site itself be more fruitful?
 

JohnCoker

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Hey there!

Not sure if this is the right place to put this, but I've confirmed via Aerotech's Master Motor Matrix, updated 8/24/21, that the E15W has gone out of production.
Thanks for letting me know; I marked it as OOP.
 

AeroTech

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For a while the E15 and E20 have been the same motor (perhaps someone from AT can explain how this came to be). So the E15 has ended, but the E20 continues.

I love this motor.
It was a marketing thing, long story.
 

jqavins

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John, I know you get lots of feature requests, some easier or more practical to implement than others. Just add this one to the pile for consideration:

For some of the search parameters, it would be nice to be able to specify ranges. "I'm looking for I motors in either 38 or 54 mm." "I want all motors of about 600 N average thrust; let's say 550 to 650." And so on. Some of the existing parameters (like diameter) could get this, and some (like average thrust or total impulse) don't make any sense when a specific value is to be given, but do make sense for a range.

On some other parameters, multi-select plays a similar role. Diameter could be that way or a range; either way works. Multi-select would be good for propellants. And so on.
 

heada

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I know when you create an account you can save rocket designs for future use but can you list your motor inventory and run motor match simulations against your inventory?
 

Buckeye

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I know when you create an account you can save rocket designs for future use but can you list your motor inventory and run motor match simulations against your inventory?
Yes. Favorites.
 

mtnmanak

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John - Maybe this has been addressed elsewhere, but is there a way to model fly-away rail guides in Thrustcurve? I can't seem to find it if it does exist. If not, how hard would it be to implement?

Maybe I am not thinking this through correctly, but the fly-away guides would seem to add a significant weight while on the rail and should be modeled for "slow off the rail" calculations, correct?

For example, the pad weight of my Wildman Wild Child Mini (38mm diameter rocket) is about 700-1000 grams.

These fly-away guides I have from Additive Aerospace are 135 grams:


It would seem that adding 10-20% of the weight while on the rail would have a significant effect on the speed when the rocket exits the rail.

Or maybe I am overthinking this?
 

jqavins

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You could simply adjust the mass of the rocket for that of the FARG to get more accurate speed off the rail. Of course, that would make for less accurate apogee, so take your pick or run two simulations.

I can't speak for John, but it seems to me that ThrustCurve's simulations are not really aimed at that level of accuracy. It does sound like a good feature request for OR and RS, though.
 

mtnmanak

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You could simply adjust the mass of the rocket for that of the FARG to get more accurate speed off the rail. Of course, that would make for less accurate apogee, so take your pick or run two simulations.

I can't speak for John, but it seems to me that ThrustCurve's simulations are not really aimed at that level of accuracy. It does sound like a good feature request for OR and RS, though.
Running the sim twice is not a bad idea. Mainly I use TC as a way to weed out motors that won't work, then go back to RS/OR to run the more accurate sim. Considering the main disqualifier in TC is "slow off the rail", I guess the answer would be to sim it with the fly-away-guide weight since I am not really using TC as a "flight sim".

At the end of the day, for TC, this would be a "nice to have feature" and agree that it would make a whole lot of sense in RS/OR. Kind of odd that those sims don't have that feature, actually.

If this is a pretty simple tweak, it would be cool to have. If it requires a lot of programming, then it would have to be way low on the feature list.
 

Buckeye

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Running the sim twice is not a bad idea. Mainly I use TC as a way to weed out motors that won't work, then go back to RS/OR to run the more accurate sim. Considering the main disqualifier in TC is "slow off the rail", I guess the answer would be to sim it with the fly-away-guide weight since I am not really using TC as a "flight sim".

At the end of the day, for TC, this would be a "nice to have feature" and agree that it would make a whole lot of sense in RS/OR. Kind of odd that those sims don't have that feature, actually.

If this is a pretty simple tweak, it would be cool to have. If it requires a lot of programming, then it would have to be way low on the feature list.
This is actually a very good, appropriate request for Thrustcurve. Like you said, rail speed and motor sorting are TC's raison d'être.

The programming is pretty simple, probably just need an added "if" statement. if altitude < rail length, then mass = rocket + flyaway guide, else mass = rocket. There is already a provision for the mass of an optional motor adapter in the code.

There are not many flights that use the flyaway guides, so it is easy to overlook this aspect, I guess. OR has been dead for over 6 years, and while RS is active, they have their hands full with a new developer and v10.
 

JohnCoker

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An interesting idea. I hadn't thought that their mass would be significant so it never occurred to me. I'll add it to the to-do list.

As discussed, it's probably best to just add the mass to your rocket for motor selection purposes. (The RS and OR simulations are going to be much more accurate for apogee because they have more realistic drag models.)
 

jqavins

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The programming is pretty simple, probably just need an added "if" statement. if altitude < rail length, then mass = rocket + flyaway guide, else mass = rocket. There is already a provision for the mass of an optional motor adapter in the code.
It would also require adding a field to the rocket definition for the mass of the guide, and the associated interface feature.
OR has been dead for over 6 years, and while RS is active, they have their hands full with a new developer and v10.
For the record, OR seems to be more comatose than dead. There's work happening, and a new version with substantial improvements is imminent. But, it seems to have been "imminent" for a good couple of years now.

There's likely a way to fenagle this in RS. There is a feature that allows pods to be ejected, and there is a way to define flight events at particular moments. So it may be possible to add a pod with a mass object representing the FARG, and set its ejection to occur when the launch guide is cleared. I haven't tried it yet. I'll report back soon. But maybe not in this thread, since that's getting pretty far off of anything to do with ThrustCurve. (I've gone rather far off already, so I'll stop now.)
 
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jqavins

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Here's another feature wish list item. It may well be more trouble than you want to take on, which would be totally understandable.

I'd like to see simulations and combined thrust-time curves for clusters of multiple engine types. 1×D12 + 2×C5, for example. Create the combined thrust curve by using the union of the sets of times in the multiple motors' individual curves, and get thrust values for the other(s) by interpolating between their points on either side.

Incidentally, I started on the RS attempts from my post directly above. I need to work in EngEdit, which wants to verify my license; my internet connection at home, which is "spotty" to put it kindly, was not up to the task that day. I haven't forgotten about it.
 

JohnCoker

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I'd like to see simulations and combined thrust-time curves for clusters of multiple engine types. 1×D12 + 2×C5, for example. Create the combined thrust curve by using the union of the sets of times in the multiple motors' individual curves, and get thrust values for the other(s) by interpolating between their points on either side.
Is this because RS/OR don't do a good enough job of clustering/staging?
 

jqavins

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No. It's because such simulations would be as handy at launch sites as those for clusters of a single engine type, and because RS (I don't know about OR) doesn't do a good job of producing nice printable thrust curves. (You have to "build" a rocket an launch it then plot the thrust as flight data from a simulation.)

I've got a spreadsheet showing what I'm talking about with the resulting curve. It shows a D12 plus 2×A10, which would be a nice combination to get a heavy rocket off the rod fast without pushing it very high. Please forgive the lack of annotation in the computations.
1633005380575.png
 

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