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In full dis­clo­sure the author of this post is involved in mod­el, ama­teur and high pow­er rock­etry so for­give their over excitement! 

The Nation­al Asso­ci­a­tion of Rock­etry in the USA has run NARCON a rock­etry themed con­ven­tion for many years and recent­ly has moved to vNAR­CON mov­ing the major­i­ty of activ­i­ty online. After the event the videos are put online and it’s always chock full of use­ful infor­ma­tion and devel­op­men­tal knowl­edge for the glob­al rock­etry community. 

In recent years FreeCAD has increased in vis­i­bil­i­ty in rock­etry com­mu­ni­ties, thanks main­ly to the amaz­ing rock­etry work­bench built by fab­u­lous FreeCAD Con­trib­u­tor Dav­es­rock­et­shop. The Rock­et work­bench makes it real­ly sim­ple to cre­ate com­plete rock­et designs or rock­et com­po­nents from either open data­bas­es of known rock­etry com­po­nents or using your own para­me­ters. It’s an amaz­ing tool for cre­at­ing CAD com­po­nents for 3D print­ing, laser cut­ting and more. As part of design­ing rock­ets the design­er is con­cerned about sta­bil­i­ty as well as gen­er­al flight dynam­ics, how high can it fly is not only of inter­est in terms of the infor­ma­tion need­ed for a safe and suc­cess­ful flight. 

There are numer­ous tools that help peo­ple some­what analyse and sim­u­late their rock­et designs, Open­rock­et is an excel­lent and pop­u­lar open source tool which has some crossover fea­tures and approach­es with the FreeCAD Rock­etry Work­bench. There are also pro­pri­etary rock­et design tools, pri­mar­i­ly Rock­Sim and then there is a free to use closed source win­dows pack­age called RASAero II. It’s been not­ed that all of these tend to dif­fer slight­ly in their sta­bil­i­ty analy­sis in part due to them using slight­ly dif­fer­ent ana­lyt­i­cal tech­niques (Open­rock­et uses Bar­row­man meth­ods, Rock­sim uses a pro­pri­etary extend­ed Bar­row­man sys­tem and RASAero uses a Rogers Mod­i­fied Bar­row­man system). 

In the above video Ken steps through ele­gant­ly how he has used FreeCAD and the Cfd­OF Work­bench to analyse rock­et designs using Com­pu­ta­tion­al Flu­id Dynam­ics (CFD). This is incred­i­bly inter­est­ing for rock­etry peo­ple as it offers a com­plete­ly dif­fer­ent approach to sta­bil­i­ty and drag analy­sis and has shown some inter­est­ing results com­pared to oth­er meth­ods. Notably there has been a long stand­ing set of com­mu­ni­ty held beliefs around how much drag is cre­at­ed by the addi­tion of dif­fer­ent types of launch rail attach­ments (small lugs or tubes or con­for­mal parts added to the out­side of rock­ets to attach them to the launch rail). Some of these beliefs are based on tiny amounts of wind tun­nel data from the 1960’s and this data is still being used by some of the rock­et analy­sis tools men­tioned above. It’s fab­u­lous to see FreeCAD being used to devel­op deep­er under­stand­ing and prac­tice in the rock­etry com­mu­ni­ty. We wish every­one there blue skies and low winds for hap­py launching!