Software for Model Rocketry

I’m a geek and my day job involves writing a lot of computer software so of course I’m drawn to the use of software to improve my rockets.  As a fan of open source software (i.e., free) I was naturally drawn to OpenRocket.  This allows me to use (most) simulation files developed using the commercial software, RockSim by Apogee Components, which I’ll probably break down and buy soon because it’s got really cool features, like printing nose cones and other parts if you’ve got access to a 3D printer (our library has a 3D printer so I may see what I can do with a trial version Rocksim).  For my current needs, OpenRocket allows me to simulate launching my rockets on different sized engines with different delays before parachute deployment.  In the past, I would have to guess whether to use a certain engine and, occasionally, would lose a rocket or have the parachute shred upon opening.

RocketReviews is a great web site where other hobbyists describe modifications or issues building their rockets and often share their RockSim calculations.  A good place to start is their RockSim Library which can be searched or filtered by manufacturer to find a specific kit.  For example, a RockSim file is available for my Executioner.  OpenRocket lets me open these files and see how different engines will perform.  Add a couple of engines on the Motors tab then click on the Run Simulations tab, select one or both entries and click the Run Simulations button.



I can also plot the projected flight to see where the parachute ejection occurs with respect to apogee (below) and check the speed at deployment ("Velocity at depl" in the above simulations).


I’ve used these guides to help decide which delay to use (i.e., D12-3 instead of D12-5 means a 3 second delay instead of 5 second) to prevent the parachute from shredding or getting tangled when opening at high speed.  I weighed my painted rocket to compare it to the empty weight used in the RockSim file and it matched within a few tenths of an ounce.  OpenRocket also allows me to help preview what the rocket will look like with my chosen paint scheme, and can can add a separate image to overlay decals. 



I also really like seeing other people’s rocket launch videos so decided to try to capture my own.  Being too cheap to buy a dedicated video camera, I brought my MacBook Air to the launch, started QuickTime recording before launching the rocket and captured a nice stable video (without the jerkiness of hand held iPhone videos).  After playing around I was able to edit the video using iMovie, cropping it, slowing down the replay and adding a title.  Check out the slow motion liftoff on my October 15th posting.  In the future I’ll play with combining my hand held and computer videos.

Finally, I will post launch videos from the rocket's perspective when I get my Astrocam to record.  Estes just started selling a kit to strap the video camera onto any rocket, so I will try to record from my Executioner in a future launch.  11/20 update: Estes has added the kit but I've read they're not going to sell the holder without the camera.  Plan B is to build one using 3D printing (some plans are available for download).

UPDATE: https://github.com/dbcook/openrocket-database has information about how to update your local copy of the OpenRocket database with current parts.  Some geek skills are required to get it working, especially on Windows.  I'm using a Mac and am comfortable using the terminal to issue commands and found their directions worked on the first try for me.  This adds "From database" to the menu, as shown below for locating the exact dimensions and weight of an Estes transition to a RockSim mockup of an Estes Gemini Titan II because I'm thinking about building this from plans:


Again, this worked on my Mac.  Your mileage may vary...

Feb 28, 2022 UPDATE-The developers behind OpenRocket just announced their first new release since 2015 of version 22.02 Beta of OpenRocket.  It now supports adding "pods", updated engine and accessory databases and lots of other cool features that I have yet to explore.  Check out https://wiki.openrocket.info/Downloading_%26_Installing or their main site at https://openrocket.info to download this new release.

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