OpenRocket Simulation Software

NARCON – Mar 13, 2010

Kerry QuinnNAR# 88941

FoxValleyRocketeersWoodstock, 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

• Motor / Wind / Altitude Interactions• Stability Questions• Educational – Math/Physics• When It’s too cold to fly real rockets • It’s fun

• Advanced Flights (dual deploy, air-start etc.)• Contest Flying / Optimization• Kit Mods / Scratch Building

Why Run Rocket Simulations ?

You will be smarter than

the average bear

All

Roc

kete

ers

Som

e R

ocke

teer

s

Evolution of a Rocketeer…

* Ref: Essence Model Rocketry Site (EMRR) www.rocketreviews.com

*

Wylie: more of a build-it &

fly-it guy…

Step 1: Excitement Step 2: Excitement, tempered by knowledge

Step 3: Understanding, punctuated by aspirin and less frequent flying

Step 4: Mastery, with safer flights & shorter walks to recovery (lighter wallet)

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 Niskanen

SampoSampo’s Brother Antti

Hybrid Rocket Launch for a science program on the Finnish Broadcasting Company – February 2010

So is it “like Rocksim” ???VCP wRASP SpaceCAD Rocksim OpenRocket

Price Free Free $ 55 $ 120 Free

Compute CP & CG Yes Not auto Yes Yes

Compute Cd limited Yes Yes

Predict Altitude Yes Yes Yes Yes

Predict Descent speed & duration

Yes Yes Yes

Effect of Wind Yes Yes Yes

Staging Yes Yes Yes Yes

Clustering Yes Yes Yes Yes

Effects of Surface finish No Yes Yes

Fin Cant No Yes Yes

Dual Deploy No Yes Yes

Print Templates Yes Yes Yes No

Generic Fin Shape No Yes Yes

Viewing Angles Yes Any Side, end

Shaded Views Yes Yes No

Flight Animations No Yes No

Effect of Atmosphere Yes Yes Yes Yes

Standard Part Names ? Yes No

Dynamic Stability No Yes Yes

Tube Fins No Yes No

External Pods No Yes Visual, no aero

Non Axisym Thrust No ? No

Export Data Yes Yes Yes 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)

B4-4 engine C6-3 engine Finish

Actual 64.0 m 151.5 m

OpenRocket 74.4 m +16% 161.4 m +7% Regular Paint (60um)

RockSim 79.1 m +24% 180.1 m +19% “matt finish”

* Analyses based on measured mass and CG.* Both simulations are similar, both over-predicted altitude

OpenRocketActual

RockSim

OpenRocketActual

RockSim

B4-4 C6-3

OpenRocket Main Screen1. “DESIGN TREE”

4. “DESIGN PARAMS”

3. “QUICK SIM”

2. “MODEL VIEW”

• 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

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 treatedIndividually. Any shape possible.

Typical Simulation Results

Dual Deploy Chute

Weathercock & Drift

Drag, Stability and Mass by component

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

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

Launch rod

Orientation vs. Time

Side view of launch

Maybe they should have used OpenRocket…

wind

Spin Stabilization

Individual Fins

Add Cant

Roll Rate (70 rpm)

Azimuth

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 …

Barrowman eqns require minimum 3, equal spaced fins…. But no such restriction in OpenRocket…

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

A couple of “mini-studies” with OpenRocket …..

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…

For a shorter walk, lower altitude: aim into the wind …

wind

Note: a 1 DOF simulator, like wRASP, won’t tell you ANY of this….

Launch Rod Angle

“Two Fins and Nose Cone” ? (!)Some things are best left to VIRTUAL reality

windw

ind

wind

wind

2 FNC . . .don’t try this at home…wind

win

d

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.

If there is no restoring force, the rocket cartwheels ….

+90 zenith = towards sky

-90 zenith = towards ground

What’s so great about 6 DOF ?

Unstable Flights 2Unstable Flight 1

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?

Quest

“Totally Tubular”

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

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. Create Model in OR

2.Run the OR model file thru ORutil

3. View/print resulting *.htm file using Internet Explorer

1”x1” square

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)