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The link you sent is very good. An interesting mixture of engineering and pragmatical reasons why it won't work. To them I add the problem of transition - assuming that London could be served by two circular runways instead of five "normal" airports, how would it manage while (for example) Heathrow was razed and rebuilt as a circular runway?
Of course, if they razed Luton...
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.
Nah! Saw the joke but, I have had the effort of explaining why things like circular airports are not good. Too long spent, I found the Mentor Pilot thing too late last time, so I was all primed for someone to come up with Circular Runways again. Luton, mmmm, not too bad an idea...
You can get DraftSight download for free. It appears they are now trying to upsell you, but when I used it, it was a pretty straight-forward copy of the old AutoCad 2d program. They will require an email address, and will send you 'offers', but for free, it was good for basic use.
You can also use SketchUp. It was a full 3-d package. I believe there is a personal edition for free, that doesn't have the professional features. I never got very used to the way it worked, after having used SolidWorks, but I remember finally figuring out that it could do what I wanted.
Hope these help. There are also probably a ton more freebies out there, but others would have to chime in for reviews on them.