Help Needed for RocketPy Solid Motor Configuration for AeroTech M2500T

[AtaKerem]

Hello everyone,
I'm trying to configure a RocketPy simulation and I need to configure the rocket motor. RocketPy needs the following parameters:
- dry_mass
- dry_inertia
- nozzle_radius
- grain_number
- grain_density
- grain_outer_radius
- grain_initial_inner_radius
- grain_initial_height
- grain_separation
- grains_center_of_mass_position
- center_of_dry_mass_position
- nozzle_position
- burn_time
- throat_radius
Explanation for the parameters are here: https://docs.rocketpy.org/en/latest.../SolidMotor.html#rocketpy.SolidMotor.__init__

I can get some of the parameters like the dry mass and the burn time from thrustcurve.org but I have no idea where I can find all the other parameters. Does anybody know where I can get these parameters for an AeroTech M2500T? Thanks!

 

[Antares JS]

A bunch of those can be had from the drawing.

https://d3l66gvjdr7rqw.cloudfront.n.../hp 98-10240 (m2500t-p) 'i'_1709829774090.pdf

 

[Handeman]

Wow! That RocketPy looks like a huge rabbit hole! Not one I want to dive into but you might love it. Good luck.

 

[Neutronium95]

Hello everyone,
I'm trying to configure a RocketPy simulation and I need to configure the rocket motor. RocketPy needs the following parameters:
- dry_mass
- dry_inertia
- nozzle_radius
- grain_number
- grain_density
- grain_outer_radius
- grain_initial_inner_radius
- grain_initial_height
- grain_separation
- grains_center_of_mass_position
- center_of_dry_mass_position
- nozzle_position
- burn_time
- throat_radius
Explanation for the parameters are here: https://docs.rocketpy.org/en/latest.../SolidMotor.html#rocketpy.SolidMotor.__init__

I can get some of the parameters like the dry mass and the burn time from thrustcurve.org but I have no idea where I can find all the other parameters. Does anybody know where I can get these parameters for an AeroTech M2500T? Thanks!

Do you actually need to use RocketPy? Adding in all pf those factors won't result in a simulation that's any more useful, in comparison to using ab existing .eng or .rse motor file. From what I've seen anf heard the software has some interesting capabilities, but the developers aren't too familiar with rocketry as a whole, and just seem to pile on detail far beyond what's necessary to make a useful simulation instead of making it more usable for regular hobbyists.

 

[Voyager1]

Wow! That RocketPy looks like a huge rabbit hole! Not one I want to dive into but you might love it. Good luck.

Do you actually need to use RocketPy? Adding in all pf those factors won't result in a simulation that's any more useful, in comparison to using ab existing .eng or .rse motor file. From what I've seen anf heard the software has some interesting capabilities, but the developers aren't too familiar with rocketry as a whole, and just seem to pile on detail far beyond what's necessary to make a useful simulation instead of making it more usable for regular hobbyists.

If you’re prepared to set it up, RocketPy is an impressive package. Yes, it’s fiddly to install and you do need to define your models and motors, but once you’ve got past all that it has some very impressive outputs, including splash patterns and 3D flight profiles to Google Earth.

 

[Art Upton]

If you’re prepared to set it up, RocketPy is an impressive package. Yes, it’s fiddly to install and you do need to define your models and motors, but once you’ve got past all that it has some very impressive outputs, including splash patterns and 3D flight profiles to Google Earth.

I am curious who has tested all those "outputs" of this Py compared to actual flying of rockets with the parameters?

When RockSim pro that did drift and splash zone patterns was in Alpha and Beta Testing, Tim had lots of rocketeers volunteer with GPS logging rockets do comparison and send the data back to him.

 

[manixFan]

RocketPY is designed for impact analysis for a ballistic flight. It is heavily used in Europe and has had its methodology validated in a technical journal. I can be used to satisfy the safety requirements for stakeholders who are trying to insure that rockets that have a ballistic flight pattern land in safe areas. It imports wind data and uses all the technical information about the rocket, motor, launch azimuth and angle to determine the amount of weather cocking and how it will affect the ballistic impact points.

The biggest benefit of it is you can set up a Monte-Carlo simulation and create dispersion patterns with varying levels of confidence intervals. It can be used to help set Go/NoGo conditions for a launch based on current wind conditions.

It's far from a trivial application and I don't believe it is intended for individual hobbyists to use. It's main audience are the folks that run large launches and want to make sure rockets don't end up where they are not wanted.


Tony

 

[mikec]

I'm still not sure what RocketPy is doing that it can't just figure out from the thrust curve like any other sim.

 

[manixFan]

I'm still not sure what RocketPy is doing that it can't just figure out from the thrust curve like any other sim.

What other sim do you use that can run a Monte Carlo simulation of 250 launches of the same vehicle with the wind coming from a heading of 0º at 10 mph. And then repeat that in 45º increments around the compass. And plot the 3 sigma impact circle on a Google Earth image for each heading run. Then do the same thing again with the wind set at 20 mph. Or use real-time weather data downloaded from public datasets via the internet to model a launch held that day.

I think there is a fundamental misunderstanding of what RocketPy is and isn't. As I mentioned above, it is not designed to be used by hobbyists to predict altitude or wind drift. If you need to make very well informed estimates of where a rocket that takes a ballistic trajectory will impact, using a wide variety of factors of the actual physical characteristics of the model, then RocketPy is for you. It is very similar to the kinds of simulations used by commercial and governmental agencies.

As a quick example of what it is doing, based on all the physical data provided to the program, (look back at some of the information required by the simulation as mentioned in post #1) it calculates the center of gravity throughout the entire burn as the fuel is consumed, as well as center of pressure. It does that so it can model the effect of wind on the path of the ballistic trajectory. You can't model that from a simple thrust curve.


Tony

 

[mikec]

If you say so, but it only does BATES grain geometry and the CG evolution of such motors is easy to determine from the information in a RASP file, to a fair degree of accuracy.

I'm sure it's a great program and very capable.

 

[Art Upton]

#1) it calculates the center of gravity throughout the entire burn as the fuel is consumed, as well as center of pressure. It does that so it can model the effect of wind on the path of the ballistic trajectory. You can't model that from a simple thrust curve.


Tony

Hi Tony, you mention Ballistic trajectory a few times and how government fly say sounding rockets. Just curious does this also help predict flights that go straight up and then pop a parachute for recovery in a safe zone?

 

[drewnickel]

Hi Tony, you mention Ballistic trajectory a few times and how government fly say sounding rockets. Just curious does this also help predict flights that go straight up and then pop a parachute for recovery in a safe zone?

It does indeed work with parachutes as well. I guess the bigger benefit to RocketPy is it gives you literally all the control you could ever want or need in simulating a launch. High fidelity models like that are going to take work to set up.

 

[Reinhard]

Hi Tony, you mention Ballistic trajectory a few times and how government fly say sounding rockets. Just curious does this also help predict flights that go straight up and then pop a parachute for recovery in a safe zone?

At EuRoC (European equivalent to SAC), RocketPy is the official simulator. Teams need to submit their RocketPy simulation, but RocketPy team members are on location to run the simulations with the current data. For example, before a launch window opens, a Google Earth Map is generated with the estimated landing points for nominal flights as well as for the main at apogee and ballistic impact scenarios. That's mostly for deciding whether to proceed with the launch at the current conditions, but it can also help with narrowing the search area in case of a tracking failure.

Reinhard

 

[Reinhard]

Hello everyone,
I'm trying to configure a RocketPy simulation and I need to configure the rocket motor. RocketPy needs the following parameters:
- dry_mass
- dry_inertia
- nozzle_radius
- grain_number
- grain_density
- grain_outer_radius
- grain_initial_inner_radius
- grain_initial_height
- grain_separation
- grains_center_of_mass_position
- center_of_dry_mass_position
- nozzle_position
- burn_time
- throat_radius
Explanation for the parameters are here: https://docs.rocketpy.org/en/latest.../SolidMotor.html#rocketpy.SolidMotor.__init__

I can get some of the parameters like the dry mass and the burn time from thrustcurve.org but I have no idea where I can find all the other parameters. Does anybody know where I can get these parameters for an AeroTech M2500T? Thanks!

For all the information that can not be found from thrustcurve.org, a reasonable approximation based on the drawing above is all that you need. For example, the rocket's inertia will not be significantly affected, if the length of the propellant grains is off by 20%, but it will be affected if you enter ridiculous numbers like 1km long grains.

Reinhard