I received the TurboCAD stuff Friday (actually, I got it Saturday, but it was delivered Friday :)). So I installed a copy, and started trying it out. If you want a copy let me know, it is pretty good stuff.
Of course the best way to try out a CAD tool is to design something useful with it. The something useful I tried was an aerospike engine: http://lucifer.piratelabs.org/Rockets/spikelist.jpg http://lucifer.piratelabs.org/Rockets/spikelist.TCW http://lucifer.piratelabs.org/Rockets/spikelist.dxf I have run into a few difficulties and learned quite a bit: 1. The actual location and size of the throat is not obvious. Twice I dimensioned the spot where I thought the throat was to later find out that there was a smaller area downstream of it. (The first time was just a boneheaded DOH!, the second time was a subtle trick of conical geometry.) 2. The throat dimension is going to be real tough to get right on the scale we are working at. .020 inches is a ~400N thrust difference. 3. It looks like (from what little I have found) the "ramp" geometry is fairly important to getting good performance and the proper flow fields. The ramp on my drawing is pretty much wrong, I think. A NASA-AIAA paper that I found uses a flow 28-34 deg off the center axis at the throat and a cubic spline curve for the ramp. 4. WOW!!! something is wrong with my calcs. I get theoretical numbers from 3700N thrust and 132 Isp at 500m elavation (our test stand) up to vacuum 5000N and 180 ISP. Okay, so vacuum performance is unattainable even for an aerospike, but I am questioning my thermodynamic analysis - does this seem reasonable for theoretical numbers at 300psi chamber pressure and 85% HTP?? 5. I really need to do some CFD on this. Does anyone know of a good grid/mesh generation software package that is low-cost and easy to obtain? I have some CFD code that should do exactly what I need (AllSPD-3D from NASA Lewis) but generating a grid by hand is more tedium than I can bear. Dave _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
