Imaginary Rockets – Modeling, Mocking and Planning (2)

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Most people who know me probably wouldn’t be surprised if I skipped the planning phase and just started building a rocket, blindly trusting it would work. Kerbal inspired me, though, and modeling and testing virtual prototypes had its own appeal. I downloaded OpenRocket, and found that on this modeling software, much like in KSP, I could build outrageous designs and test them for feasibility without ever having to worry about the dangers of live testing.

Before I even got started building I figured it would be important to set a few goals of what I would like to accomplish through iterative testing and development:

  • Stable Aerodynamic Flight
  • 1km Apogee
  • 360º Video
  • Aerodynamic control (articulated control surfaces? thrust vectoring?)
  • Remote Telemetry
  • Powered Descent/Landing
  • Maintain Medium Powered Rocket Classification

I’ll go into more detail about each of these objectives in their own posts, but to summarize, I wanted to build a rocket under 1kg that could take a 360º camera up to 1km altitude. Meanwhile, I thought it would be fun if that rocket constantly sent telemetry data back to a computer, and was able to perform some tricks.

At first I thought it might be necessary to build a massive body rocket that can carry larger camera systems, since most 360º cameras are fairly wide, but with some searching I was able to find the Kandao Qoocam 4K – a 360º camera in a stick configuration, which will help greatly reduce the diameter of the rocket, and therefore improve A LOT of the aerodynamics, but I’ll discuss this more in my “Optics” post.

Kandao Qoocam 4K 360º Camera on Amazon.com

A 1km rocket isn’t easy, especially when one key limitation is that I’m not certified to fly anything over a G class motor. We can get further into motor classes and model rocketry certification levels, but suffice to say I was not going to just be able to strap more motors on it like you would in KSP. This time I needed to be a lot more strategic about my design choices.

I spent some time looking around for a suitable rocket modeling program, and settled on OpenRocket because it was straightforward, free, and cross-platform (which meant it would work on my Mac). There are a lot of great modeling programs out there. They range from simplistic, like OpenRocket, to complex all-purpose 3d modeling suites. Choose one based on your level of comfort or ambition, and employ google search liberally.

In OpenRocket you can change each of the design parameters of your craft, including weight, roughness, shape, placement, motors and timing. One major setback is there seems to be a bug when running on OSX that causes it to crash when switching back to “Side View” from other view modes.

Another big setback of OpenRocket, but also almost all model rocketry software I encountered, was that it isn’t built for modeling electronically influenced flight plans, such as off-engine recovery methods, chute delays, dynamic flight control or electronically timed staging. It’s not the end of the world, and I’m probably one of very few people who have this complaint.

The first versions of the MarkDart were very bulky. Before I found the Qoocam, large cameras led to large bodies, lots of engines, and ultimately nowhere near Medium Power classification.

OpenRocket rendering of an early, unfeasible version of the MarkDart

As you can see from the image above, it would have been a BEAST of a rocket, both in size and trajectory. While I would have loved to violate FAA airspace regulations, I’m not entirely confident I’m ready to be able to light 3 motors simultaneously, and the risk of rapid unscheduled disassembly would have been altogether way too high.

Another early/scrapped MarkDart design

Moving to the Qoocam allowed me to be a lot more realistic about the design, ultimately settling for a one-engine vehicle with a 41.6mm diameter body. The rocket would have a clear payload tube for the optics payload (that’s aeronautical engineering lingo for the camera), and a fiberglass engine/parachute compartment.

The final MarkDart1 design before ordering parts

In my next post, I will discuss building a system to understand what the rocket is doing at any given point in time, also known as telemetry.