Rocksim Help

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

roytyson

Well-Known Member
Joined
Oct 31, 2017
Messages
429
Reaction score
294
Ok, starting to get nervous about my L1 flight next month.

So I'm trying to get everything loaded into Rocksim, but was having trouble making it all work out to the totals. I finally just done a mass override on the weight/cg without the motor, then added the motor.

I'm not sure how to change each part to get the mass correct any other way.

For what I have loaded, does there appear to be any concerns?

Thanks for any feedback you may have.

ROY

Rocksim-__Users_roytyson_Desktop_dx3_3_rkt___Activation__Validated___and_Motors.jpg
 
Looks about right. Overriding the overall mass and CG (no motor) is the best way to do it once your rocket is built.

Altitude, launch rod departure velocity, and optimal delay are the three most important things I look at in the simulation when it comes to choosing a motor.

I have the same cardboard DX3 (with dual deploy). Works just fine with H128 and H180 to moderate altitudes of 1700- 2200 ft. These may be better choices for cert, rather than I200 at 3000 ft.
 
A mass override with manual CG will get you there. Did you do a CG manually?

I usually do an individual CG and mass for each component while making design choices. However once the rocket is fully assembled I then do a mass and CG override.

Beyond that I am assuming you're going with motor eject? If so then make sure your delay matches the sim as close as you can get it. Rocksim does a good job in estimating this. Once you have run your sims, just double click each one to bring up the simulation results, then scroll down to "Time data", specifically "Optimal ejection delay" and round up if you can.

Once you have this number you can adjust the delay on the simulation, where you add the engine and set your events.

Good luck.
 
Oh, for sure. I plan on my cert with either H210 or H180. The I200 is my fun motor.
 
I agree with buckeye and mpitfield. You are good to go, good luck on your certification flight.


Composite Addict
 
I did both my L1 &L2 on a cardboard 4" DX3. The L1 flight was an Aerotech H123 to about 750ft. I used motor ejection to pop the near apogee and it made for a great cert flight.

As everyone else said, once the rocket is built, the weight of individual components no longer matter; you've added epoxy, hardware, paint, etc., which are (nearly) impossible to know in advance. Override the weight and CG and enjoy the flight.
 
I did both my L1 &L2 on a cardboard 4" DX3. The L1 flight was an Aerotech H123 to about 750ft. I used motor ejection to pop the near apogee and it made for a great cert flight.

As everyone else said, once the rocket is built, the weight of individual components no longer matter; you've added epoxy, hardware, paint, etc., which are (nearly) impossible to know in advance. Override the weight and CG and enjoy the flight.

Yes, and just fyi: I also did both my L1 and L2 on a 4" cardboard SuperDX3. It's a nice sturdy kit for a wide variety of H-I-J motors. For L1, I used AT I305 to 2206 feet, and then later for L2 used CTI J330 to 3724 feet. Worked great both times, although both of my peak altitudes were lower than sim by about 25%, probably due to my very poor paint job, not smooth at all. Anyway, rather than details about motor choice, I was more worried about avoiding CATO by drag separation or lack of separation on motor ejection -- i.e., trying to get the friction fit just right between booster and payload section. I asked the RSO to help me double-check it each time, held it for a shake test, added a bit of masking tape, then got perfect recovery both times (JLCR, not DD).

Best of luck.
 
My L1/L2 was also a 4" super dx3. lol. I way overbuilt mine. L1 was on a 54mm CTI I218 (barely scraped 1000ft and L2 was an aerotech DMS J250 (2500+ft).

I agree with the guys above. Don't go ham on a cert flight. There's more than enough time to push limits after you Cert. You don't get extra points for turning heads. It's pass or fail. Make sure you pass.
 
I agree with the guys above. Don't go ham on a cert flight. There's more than enough time to push limits after you Cert. You don't get extra points for turning heads. It's pass or fail. Make sure you pass.

The above is not my personal philosophy.

I push my certs flights because it is much more rewarding to take risks when I have something on the line. I have never subscribed to the "make sure you pass then take risks later" mantra. Failure is an option", you just dust yourself off, figure out where you failed and try again. Failure is often when the deepest knowledge is gained and a big part of the hobby is about learning through personal experiences for me.

Why if someone does more than a pop and drop does it automatically have to be about "turning heads", its not always about the destination, there is also a journey to enjoy. If it was all about ego I would be burning through my certs.
 
The above is not my personal philosophy.

I push my certs flights because it is much more rewarding to take risks when I have something on the line. I have never subscribed to the "make sure you pass then take risks later" mantra. Failure is an option", you just dust yourself off, figure out where you failed and try again. Failure is often when the deepest knowledge is gained and a big part of the hobby is about learning through personal experiences for me.

Why if someone does more than a pop and drop does it automatically have to be about "turning heads", its not always about the destination, there is also a journey to enjoy. If it was all about ego I would be burning through my certs.

It all depends on the primary reason for attempting a certification flight. If the primary reason is certification, show us what you know. That’s really all that the certification witnesses need to see.
If you want to push it, you raise the risk of failing that goal, but we leave it up to the flyer. There’s no place on the forms for style points. [emoji3]. Either way, we’re there to help.


Steve Shannon
 
It all depends on the primary reason for attempting a certification flight. If the primary reason is certification, show us what you know. That’s really all that the certification witnesses need to see.
If you want to push it, you raise the risk of failing that goal, but we leave it up to the flyer. There’s no place on the forms for style points. [emoji3]. Either way, we’re there to help.


Steve Shannon

No disrespect however "primary reason" and taking risks are not mutually exclusive. If the small percentage of humans that push our species forward didn't take risks then we would still be sitting in caves if at all.
 
No disrespect however "primary reason" and taking risks are not mutually exclusive. If the small percentage of humans that push our species forward didn't take risks then we would still be sitting in caves if at all.

No worries, I didn’t feel any disrespect from you. This is a philosophical difference, nothing more. I absolutely agree about pushing forward. Where we disagree is in when to take risk and it’s really a personal choice. A certification flight already entails risk: a person may fail. I wouldn’t see how fast I could accelerate during a driver’s license test either.
In my opinion only (absolutely no relationship to Tripoli policy), if you truly want to be able to be in a position to take greater risks to advance your knowledge, you focus on passing the test, then once you pass the test that allows you to progress to higher powered motors so you can fly to higher altitudes, launch larger payloads, learn about building larger motors, etc.
I wanted to add that this doesn’t mean you shouldn’t have fun with your cert flight, just make sure the main reason for the flight isn’t neglected.



Steve Shannon
 
Last edited:
I always make sure I am thinking about pushing the envelope and learning something from each flight. My certs were at higher impulse motors (I, K, N) than the requirement, but that was my personal choice.

Choose how you want to fly and keep within the rules :)
 
Back
Top