#3: K’Tesh! A Chat with Jim Parsons, OpenRocket Wizard

The Omega booster and Cineroc, simulated in OpenRocket by our guest, Jim Parsons

In this episode, we talk with Jim Parsons, who was once described as “the Chuck Norris of OpenRocket.”

OpenRocket is free model rocket design and simulation software which runs on Java. You can download it here, and play around with it if you’ve never tried it before.

OpenRocket is a great tool – and it’s free. But it does have its limitations.

If you make a sim of a kit, you might notice that it doesn’t look exactly like the kit you’re building. One big difference you’ll notice is the nose cone. All nose cones in OpenRocket (except for the elliptical ones) come to a sharp point, which isn’t the case in most model rockets. Usually nose cones are spherically blunted.

Jim Parsons’ OpenRocket version of the Estes Der Red Max, with an accurately-shaped nose cone

Now, for a flight simulation, this may not matter much. To find the center of pressure, model rocket simulators use what’s known as Barrowman equations, a system of mathematically locating the CP on a model rocket. These were derived from the math used in sounding rockets, and were published as an R&D report at Naram X in 196X by James Barrowman. (Click here to see the N00b’s interview with James Barrowman at NARCON 2017).

One of the simplifying principles of Barrowman equations are the assumption that all nose cones come to a sharp point.

But what if you want a simulation that looks like the actual kit? What if you’re trying to clone a historic, out of production model? Or you want a good reference for decal placement?

Jim has figured out how to trick OpenRocket to simulate accurate looking kits of all kinds. Some are quite challenging, because of features on the model that OR isn’t built to re-create. Check out this masterful sim of the Estes QCC Explorer.

The intakes on this model were challenging. Read about it here.

While most of K’Tesh’s sims can be used for flight simulations, due to the limitations of OR, there is the occasional model sim which is mostly just for show. The A.C.M.E. Spitfire, by FlisKits, is one such example.

This version of the A.C.M.E. Spitfire is about as close as OR can get.

The N00b has used some of Jim’s files and images to figure out the decal placement and paint scheme measurements on a number of builds, like his recently-completed Semroc Bandit and Semroc Cherokee D.

The N00b’s Cherokee D, a Retro-Repro by Semroc

Jim joins us from China, where he lives and works. He and the N00b discuss OpenRocket, chat a little about model rocket history, and the challenges of pursuing the hobby while living in China.

Check out K’Tesh’s master list of sims on The Rocketry Forum by clicking here :

https://www.rocketryforum.com/threads/kteshs-openrocket-files-index.148212/