What stupid project do you have to do to research centrimetric radar?

[Gen.Lagus]

When trying to research 1940s tech, centrimetric radar, it just states that you have to research special project, but not what project in order to get access to research it in the normal research tree. So, what am I supposed to do?

[Nutarde45DE]

try to use the sp_instant or sp_breakthrough commands witch is "special projects" and for the centrimetric radar just look at the special project tab for air and when a special project is done just look at the tech tree then you can reseach it will look like blue for certain projects not all and maybe try reaseaching the normal radars first