A lot of Mods like this will cause windows defender to think there is a trojan, because the program alters or creates .dll files. If you got it from a link here then you can safely ignore that, I have used mechjeb for years and never had any virus or malware. Most antivirus will flag anything that tries to mess with .dll files.
Great mod, it not only taught me how to do things manually, but once I learnt from it, it also saves me the tedium of doing a lot of things manually.
Cool to see you pushing the limits of what it can achieve. I'll have a look myself too. but TBH spaceplanes hurt my brain. I normally only use them to lift to high atmosphere and then jettison them and I only do that to give myself new goals. Haven't made a space-plane that can do anything use-full yet. But testing and pushing the limits is kinda what Kerbal does best.