OpenRocket Simulation Software

NARCON – Mar 13, 2010 Kerry Quinn NAR# 88941 FoxValleyRocketeers Woodstock, IL

OpenRocket

• • • • • • Why Run Simulations Anyway ?

What is OpenRocket How does it compare to… Interesting O.R. mini-studies Could I model a ______ with OpenRocket?

Live Demonstration

Why Run Rocket Simulations ?

• • • • • • • • Motor / Wind / Altitude Interactions Stability Questions Educational – Math/Physics When It’s too cold to fly real rockets It’s fun You will be smarter than the average bear Advanced Flights (dual deploy, air-start etc.) Contest Flying / Optimization Kit Mods / Scratch Building

Evolution of a Rocketeer…

Step 1: Excitement Step 2: Excitement, tempered by knowledge * Wylie: more of a build-it & fly it guy… Step 3: Understanding, punctuated by aspirin and less frequent flying Step 4: Mastery, with safer flights & shorter walks to recovery (lighter wallet) * Ref: Essence Model Rocketry Site (EMRR) www.rocketreviews.com

What is OpenRocket ?

OpenRocket 0.9.5 is a rocket design and 6 DOF flight simulator, very similar to Rocksim … • Written by Sampo Niskanen as part of his Master’s Dissertation in 2009 at the Helsinki University of Technology: “Development of an Open Source Model Rocket Simulation Software” • Includes detailed theory manual and sourcecode (java) • Website: http://openrocket.sourceforge.net/

Sampo

Sampo Niskanen

Sampo’s Brother Antti Hybrid Rocket Launch for a science program on the Finnish Broadcasting Company – February 2010

Price Compute CP & CG Compute Cd Predict Altitude Predict Descent speed & duration Effect of Wind Staging Clustering Effects of Surface finish Fin Cant Dual Deploy Print Templates Generic Fin Shape Viewing Angles Shaded Views Flight Animations Effect of Atmosphere Standard Part Names Dynamic Stability Tube Fins External Pods Non Axisym Thrust Export Data

So is it “like Rocksim” ???

VCP Free Yes Yes wRASP SpaceCAD Free Yes Yes Yes Yes Yes $ 55 Not auto limited Yes Yes Yes Yes Yes No No No Yes No Yes Yes No Yes ?

No No No No Yes Rocksim $ 120 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Any Yes Yes Yes Yes Yes Yes Yes ?

Yes OpenRocket Free Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Side, end No No Yes No Yes No Visual, no aero No Yes Kerry Conclusions: • Much more capable than VCP & wRASP • No capabilities exceeding Rocksim • Biggest short comings relative to Rocksim:  No standard part naming (doesn’t know “BT-50” for example)  No aerodynamic calcs for “exterior pods”  No tube fins  No Printing (see later in this talk)

wRASP – a tried and true friend….

wRASP: If you know: diameter Cd mass engine You can predict: altitude, accel & velocity at launch rod tip

When looking to something new, compare it to what you “know” already… wRASP: you ‘pick’ the Cd (combo of finish and “dragginess”) O.R.: you ‘pick’ the surface finish, O.R. calculates the geometry drag

Comparison: Rocksim & OpenRocket (& altimeter)

RockSim RockSim B4-4 C6-3 Actual OpenRocket RockSim

B4-4 engine

64.0 m 74.4 m +16% 79.1 m +24%

C6-3 engine

151.5 m 161.4 m +7% 180.1 m +19%

Finish

Regular Paint (60um) “matt finish” * Analyses based on measured mass and CG.

* Both simulations are similar, both over-predicted altitude

OpenRocket Main Screen

1. “DESIGN TREE”

• • • • Drag and drop operation Quick Sim and Params update on-the-fly Quick Sim is “rough estimate” of performance Only “side” and “back” model views available

4. “DESIGN PARAMS” 2. “MODEL VIEW” 3. “QUICK SIM”

1. Model, Quick Sim and Params update as you enter values or slide sliders 2. Large library of materials and Surface finishes built-in 3. Fins can be a “set” or treated Individually. Any shape possible.

Typical Simulation Results Weathercock & Drift Drag, Stability and Mass by component Dual Deploy Chute

OK… but what’s great about 6DOF simulation ?

You can predict trajectory as function of CG/CP and wind interactions….

Side view of launch Launch rod wind Orientation vs. Time Maybe they should have used OpenRocket…

Individual Fins

Spin Stabilization

Add Cant Azimuth Roll Rate (70 rpm) Fin canting generates spin and can be used to increase stability.

But how much to use? One fin? All fins? What will it do to altitude? Etc… Simulation lets you quickly test options

Looking beyond 3FNC designs …

Within 0.6 seconds in 10mph wind, rocket goes from 90 degrees “up” to horizontal... and beyond (!) 200 feet up and down in 2.03 seconds !!!* * This flight profile is NOT recommended Barrowman eqns require minimum 3, equal spaced fins…. But no such restriction in OpenRocket…

250 200 150 100 50 0 0 A couple of “mini-studies” with OpenRocket …..

Starhawk w/ tailweight A8-3 0.54 caliber stability

250 10

Wind (mph)

20 200 150 100 50 30 0 altitude no cant altitude 2deg cant pitch rate - no cant pitch rate - 2 deg cant

Effect of Non-uniform Fin Spacing

800 700 600 500 400 300 200 100 0 0 1 2 3

Fin #3 Mis-Position (degrees)

4 Thinking about launching a low-stability rocket on a windy day … ?

• rocket cartwheels above 12 mph wind • a little fin-cant increases stability up to 17 mph What if you build make 4FNC rocket but don’t get all fins exactly 90 degrees apart ?

• • at 90/90/90/90 you get 755 ft altitude at 90/90/92/88 you get only 631 ft Maybe that Rose Finjig is worth it after all ?

Does surface finish really matter?

Age old questions… Can I skip some of these steps ?

• Painting at all • “Polishing” • Airfoiling fins

Here is where to spend your effort…

Paint your rocket & Airfoil the fins for best altitude

Rockets, blowin’ in the wind…

Launch Rod Angle wind For a shorter walk, lower altitude: aim into the wind … Note: a 1 DOF simulator, like wRASP, won’t tell you ANY of this….

“Two Fins and Nose Cone” ? (!)

Some things are best left to VIRTUAL reality

2 FNC . . .don’t try this at home…

+90 zenith = towards sky -90 zenith = towards ground If there is no restoring force, the rocket cartwheels ….

wind wind … If I am uncertain about the safety or stability of an untested rocket, I will check the stability before flight and will fly it only after warning spectators and clearing them away to a safe distance.

What’s so great about 6 DOF ?

Unstable Flight 1 Unstable Flights 2

What can I build in OpenRocket?

Leading Edge Rocketry “Phantom”

What can I build in OpenRocket?

Semroc Hydra 7

One more reason for simulation… to predict where it will land…

The author, launching his Hydra VII Mark Bundick, retrieving the Hydra from the Woodstock swamp… (thanks again Mark)

What can I build in OpenRocket?

Fliskit Decaffinator O.R. warning about “stepped geometry”, predicted an altitude of 296 ft on D12-7

What can I build in OpenRocket?

O.R. doesn’t recognize tube fins – so CP and stability are incorrect “fly it” in – you can “build it”, but NOT OpenRocket!

Quest “Totally Tubular”

What can I build in OpenRocket?

T-65 X-wing fighter

What can I build in OpenRocket?

Planned Enhancements for OpenRocket… • • • • • • • • • • • • Aerodynamic computation using CFD Better support for supersonic simulation 3D view of the rocket design Saving figures and exporting simulation data Importing and plotting actual flight data from altimeters Importing new motor thrust curves Support for ready-made component databases Customized support for hybrid rocket motors and water rockets Rocket flight animation A "wizard" for creating new rocket designs Automatic “Engine Picker / Comparison tool” Listener plug-in apps (see below) The project is OpenSource with around 200 downloads so far. Author is soliciting help via the GNU system. Another grad student is developing a “listener” drop in code segment for his thesis, the listener gets data from and feeds changes back to the analysis as it progresses – his project is for an active guidance control system.

I can’t print from OpenRocket? (!)

• There is not yet a built-in feature in OR for printing (as of ver 0.9.5) • Kerry has developed a stand-alone print utility called “Orutil.exe”* - fin templates (trapezoidal, elliptical and free-form) - transition templates “estes-style” wrap-around fin/lug alignment guide • Written in ‘python’ sourcecode and Windows 32bit compiled versions available: www.foxvalleyrocketeers.org/myframes/reports.htm

* Special thanks to Dean Thorne for help in testing and in suggesting features.

ORutil Printing Process

1”x1” square 1. Create Model in OR 2.Run the OR model file thru ORutil 3. View/print resulting *.htm file using Internet Explorer

Summary

• OpenRocket has much of the Rocksim feature set… for FREE (6 DOF simulation is now available to everyone) • OpenRocket is easy to use • 6 DOF simulation provides much more insight than 1 DOF: stability, roll, wind, AoA etc… (and it is fun to try)