Thrustcurve Open Thread

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I think we are trying to solve two different problems in this recent thread.

One discussion is the user experience in Thrustcurve. I am not sure much, if anything, needs to be fixed on the website. I can say that, for my workflows, it works exactly like I want it to.

My main two use-cases are matching a number of viable motors to a rocket (the resulting list to be used in Rocksim of OpenRocket) or to look up the characteristics of a particular motor. In both cases, TC works great.

The other discussion is the user experience in OpenRocket, which is a different conversation entirely.
 
mtnmanak said:
I think we are trying to solve two different problems in this recent thread.

...

The other discussion is the user experience in OpenRocket, which is a different conversation entirely.
Click to expand...
Agreed. There is an overlap, though, in terms of filtering by "manufacturer." neil_w's post makes a good point that there are potentially valuable interpretations of legacy manufacturer names as product lines. Yes, there's only Estes, AT and CTI left, but there is still value in filtering by product lines.

Whether manufacturer is an appropriate way to do that, or whether we should create another field is an interesting discussion. Obviously the RASP file format is fixed now and we can't change that, but since ThrustCurve has a full DB we could maintain more metadata there if useful. (The RockSim file format is more extensible, since it's XML, but still might be dangerous to extend.)
 
For me, the filtering of motors has the same issue, whether in TC or RS. I have several Ceseroni cases and no Aerotech cases; when I search for HP motors I want to filter for Ceseroni. But it some are labeled Ceseroni and some are CTI, there's that extra step of doing two searches. No matter which environment I'm in.

I also agree with Neil about Q-Jets in particular, but that's secondary. As long as they are all tagged as Quest (first choice for me) or all tagged as AeroTech, it'll do.
 
davidshewitt said:
For anyone looking for the Android Thrustcurve app, I have it here:
https://cloud.davidshewitt.com/index.php/s/L8PFn6mpH2G37ar

The apk file is not modified in any way.

See the instructions in the README. Google how to install / enable adb for your computer and device. I'm happy to answer questions.
Click to expand...
I hadn't heard of adb until I googled it just now. As I don't do any app development, I don't have it installed. I downloaded the apk directly to my phone and tried to install it directly there, with Package Installer installer. But Package Installer blocks it, saying:
This app was built for an older version of Android and doesn't include the latest privacy protections.​

There's no "Install it anyway" button. Is adb what I need to get around this?

My phone is a Pixel 7 Pro, with Android 14.
 
jqavins said:
I hadn't heard of adb until I googled it just now. As I don't do any app development, I don't have it installed. I downloaded the apk directly to my phone and tried to install it directly there, with Package Installer installer. But Package Installer blocks it, saying:
This app was built for an older version of Android and doesn't include the latest privacy protections.​

There's no "Install it anyway" button. Is adb what I need to get around this?

My phone is a Pixel 7 Pro, with Android 14.
Click to expand...
That's correct. You need adb.
 
Since I haven't had the motivation to update this app, I have made the code available:
https://github.com/JohnCoker/TCTG

Google stopped supporting the version I was using, which would require a Cordova update, and so on.

To me, it's not a high priority because the new web site is responsive (will adjust to your phone or tablet size), but I can see the value of having an offline experience for those launch sites out of cell phone range.

Note that most of the hard stuff (database, simulation, etc) is done in the server, so this app is really just a front-end with a cache. Native apps would be better, but I can't see myself taking the time to rebuild it twice more. :)
 
Question about thrustcurve data: What's the most reliable and up-to-date data for estimating actual engine performance, out of what's available on the site?

For example, looking at the information on Estes A10 motors, at the top of the page it lists this:
2.4 N Avg. Thrust
12.6 N Max. Thrust
2.5 Ns Total Impulse
0.9 s Burn Time

In the plot below that on the page, it shows this:
1.8 N Avg. Thrust
9.8 N Max. Thrust
1.025 s Burn Time

Which would mean 1.85 Ns total impulse.

At the "Data Sheet" link, which goes to 1995 certification document, it lists this:
2.35 N Avg. Thrust
12.64 N Max. Thrust
2.50 Ns Total Impulse Certified
2.00 Ns Total Impulse Static Test
0.85 s Burn Time

The plot seems to match.

Meanwhile also linked is a more recent certification document from 2011 which lists this:
1.78 N Avg. Thrust
9.74 N Max. Thrust
1.88 Ns Total Impulse Certified
1.88 Ns Total Impulse Static Test
1.06 s Burn Time

Again, the plot matches.

So... Which would you use? The 2011 certification document data, and ignore the data listed atop the main page?
 
Different question: Because a black powder booster motor blows through its upper surface as it burns out, as contrasted with how on a regular motor the delay/election charge/clay cap act as a pressure bulkhead, is the total impulse less? Even if the thrust element is manufactured exactly the same?

In the example above of the Estes A10, the 2011 NAR test report indicates that a sample of 10 A10-0T's were tested, with an average impulse of 1.88 Ns. So maybe the A10-3T has an impulse closer to a full 2.5 Ns A? Not that we would know, because we don't have NAR test data for it?
 
ReynoldsSlumber said:
Question about thrustcurve data: What's the most reliable and up-to-date data for estimating actual engine performance, out of what's available on the site?

For example, looking at the information on Estes A10 motors, at the top of the page it lists this:
2.4 N Avg. Thrust
12.6 N Max. Thrust
2.5 Ns Total Impulse
0.9 s Burn Time

In the plot below that on the page, it shows this:
1.8 N Avg. Thrust
9.8 N Max. Thrust
1.025 s Burn Time

Which would mean 1.85 Ns total impulse.

At the "Data Sheet" link, which goes to 1995 certification document, it lists this:
2.35 N Avg. Thrust
12.64 N Max. Thrust
2.50 Ns Total Impulse Certified
2.00 Ns Total Impulse Static Test
0.85 s Burn Time

The plot seems to match.

Meanwhile also linked is a more recent certification document from 2011 which lists this:
1.78 N Avg. Thrust
9.74 N Max. Thrust
1.88 Ns Total Impulse Certified
1.88 Ns Total Impulse Static Test
1.06 s Burn Time

Again, the plot matches.

So... Which would you use? The 2011 certification document data, and ignore the data listed atop the main page?
Click to expand...
@ReynoldsSlumber --

Yes, the A10 is an interesting case.

As you noted, there are actually two certification docs:

1 - A10T certified 1995-06-24 = 2.50 N-sec / 0.85 sec
2 - A10-0T certified 2011-02-14 = 1.88 N-sec / 1.06 sec

And there are also two entries are also listed in the Combined CAR/NAR/TRACertified Rocket Motors List ( EDITED for grammar )

So which one is correct ?

Does the A10-0T produce lower thrust because it has an open forward end ?

Should these be stored as separate entries in our Sim Programs ?

Another thing that confuses me is burn time and average thrust ...

What are the official definitions of burn time and average thrust ?

How does the 5% rule factor in ?

It seems self-referential: average thrust depends on burn time and vice versus ...

I am not complaining, just confused :)

The motor testing teams and John Coker perform an ESSENTIAL service -- where weould we be without them ?

-- kjh

EDIT: I am too slow ... I was wondering the same thing about the A10-0T -vs- the A10-3T motor ( does the open forward end affect impulse ? )
 
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Oh interesting, I neglected to check what NAR itself lists, thanks. In their document, there are separate lines for the Estes A10-0 versus the A10-3, the latter of which is listed as a full 2.5 Ns A. Similarly, the 18mm A8 and B6 boosters are listed separately from the sustainer motors, with different total impulses. But then the C6’s, C11’s, D12’s, E12’s, E16’s, and F15’s aren’t separated out. One would think that especially the 24mm C11-0 would have a different total impulse compared to one with a delay charge etc. Unless Estes puts a little extra black powder into a C11-0 compared to a sustainer C11? But then weirdly in the document it’s listed on the same line as the C11-7, with the C11-3 and C11-5 on the next line.
 
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ReynoldsSlumber said:
Oh interesting, I neglected to check what NAR itself lists, thanks. In their document, there are separate lines for the Estes A10-0 versus the A10-3, the latter of which is listed as a full 2.5 Ns A. Similarly, the 18mm A8 and B6 boosters are listed separately from the sustainer motors, with different total impulses. But then the C6’s, C11’s, D12’s, E12’s, E16’s, and F15’s aren’t separated out. One would think that especially the 24mm C11-0 would have a different total impulse compared to one with a delay charge etc. Unless Estes puts a little extra black powder into a C11-0 compared to a sustained C11? But then weirdly in the document it’s listed on the same line as the C11-7, with the C11-3 and C11-5 on the next line.
Click to expand...
+1

Yes I was looking for patterns and I saw the same -- some of the Estes BP booster motors and sustainer motors are listed separately ...

I am still confused :)

-- kjh

EDIT: grammar -- I need more coffee :)
 
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From basic principles, yes, of course, some of the fuel in a -0 engine is "wasted" by sending material forward, so there has to be less total impulse. Until now, I'd have happily assumed it was insignificant. But after reading the above, I see that is not necessarily so. If the loss is roughly constant, it could be a significant fractional loss on a low impulse engine and insignificant on larger ones.
  • For the A10, it seems to be 0.62 Ns, or a 25% loss from the -3.
  • The cross sectional area of the propellant in a 24 mm engine is in the ballpark of four times as great, so let's suppose that the lost impulse is four times as great, 4×0.6 Ns = 2.4 Ns.
  • The total impulse of a C11 is 8.8 Ns, so 2.4 Ns is a 27% loss. Yikes, that should be listed as different, if my assumptions hold (a big "if").
  • On the other hand, a D12 packs 16.8 Ns, so 2.4 is a 16% loss, and maybe not worth separating.
  • And what about the 18 mm engines? The cross sectional area on those is about twice that of the 13 mm engines, so the loss (under my assumptions) is about 1.2 Ns.
  • The A8 has 2.5 Ns, so the loss would be 48%. YIKES!!
  • The B6 has 4.3 NS, so the loss is 28%.
  • And the C6 as 8.8 Ns, so the loss is 14%.
But my assumption of constant impulse loss per area could very easily be way off. If, for example, the loss is constant regardless of area, the relative losses would be:
  • A8 24%
  • B6 14%
  • C6 7%
  • C11 7%
  • D12 4%
Maybe the truth lies in between? Maybe I'm all wet?
 
@jqavins --

I can't find a real pattern in the combined cert list I linked above.

Sorry anout my hi-lighting ... my browser can only hi-lite a region and not individual rows in the PDF ...

Examples: Estes A8-0 -vs- A8-3,5 seems to match the pattern.

Screenshot_20240425_121345.png

And so does the B6-0 -vs B6-2,4,6:

Screenshot_20240425_122357.png

But there is only one entry for the Estes C6-0,3,5,7

Screenshot_20240425_122253.png

Another Mystery of Rocket Science :)

-- kjh
 
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ReynoldsSlumber said:
Question about thrustcurve data: What's the most reliable and up-to-date data for estimating actual engine performance, out of what's available on the site?

For example, looking at the information on Estes A10 motors, at the top of the page it lists this:
2.4 N Avg. Thrust
12.6 N Max. Thrust
2.5 Ns Total Impulse
0.9 s Burn Time

In the plot below that on the page, it shows this:
1.8 N Avg. Thrust
9.8 N Max. Thrust
1.025 s Burn Time

Which would mean 1.85 Ns total impulse.

At the "Data Sheet" link, which goes to 1995 certification document, it lists this:
2.35 N Avg. Thrust
12.64 N Max. Thrust
2.50 Ns Total Impulse Certified
2.00 Ns Total Impulse Static Test
0.85 s Burn Time

The plot seems to match.

Meanwhile also linked is a more recent certification document from 2011 which lists this:
1.78 N Avg. Thrust
9.74 N Max. Thrust
1.88 Ns Total Impulse Certified
1.88 Ns Total Impulse Static Test
1.06 s Burn Time

Again, the plot matches.

So... Which would you use? The 2011 certification document data, and ignore the data listed atop the main page?
Click to expand...
Do not use the Certified total impulse. Use the Average total impulse from the test data.
 
Very interesting observations!

In the case of the A10, it's less clear because of the difference in time between the tests, but maybe the entries should be split in two for the "-0" motors.
 
JohnCoker said:
maybe the entries should be split in two for the "-0" motors.
Click to expand...
I'd be in favor of that. Looking at the total impulse column in the Estes F15 raw data, on page 2 of the test report, it's more than 1 Ns different between the typical booster and sustainer. Similarly with the E16 and E12 raw data. I didn't notice there being raw data included in any of the other Estes test reports (other than the A10-0T, which is already separate from the A10-3T/A10-PT test report). Really we should ask NAR to certify boosters separately, since the propellant burn-through/burnout mechanics are different, right?

Meanwhile, other than on the newest entries, there's no apparent rhyme or reason to the total impulse numbers given on the certified motors list compared to the test results. And methinks three decades is a bit too long to let a motor go un-re-tested! Also the older initial mass measurements seem to vary by more than a gram.

Anyone have the ear of someone with the NAR who might be interested in pursuing this? It would be helpful to folks trying to optimize contest models, plus it would improve simulation accuracy.

(As an aside, I can kind of see why Estes originally called the A10-3T an A10 rather than an A2-3T. The low-thrust tail on the burn might as well be no thrust and therefore instead be considered part of the delay, which on its own is typically shorter than a full 3 s anyway. So it really does act like an A10-3. That rubric gets screwed up when it comes to the A10-0T. Going by that rubric, one could think of it as an A10-1 booster motor. Meanwhile, funny enough, an Estes-designated A3 motor has pretty much the same average thrust as an Estes-designated A10.)
 
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