How to virtualise a SharePoint ASP application
Solution 1:
It sounds like you are referring to extending a web application which will have a similar effect to what you're describing. Here is a link on how to extend a web application. The content is shared but you can configure security & such differently on each extension. You can ignore the web extension default name (internet, extranet, etc.) because they are only convenience placeholders. All web applications extensions are created equal regardless of the name you select.