In Rails project we are using sunspot gem for Solr full text search engine. Sunspot is built on top of the RSolr library, which provides a low-level interface for Solr interaction.
Is there any possibility to set that RSolr requests to SOLR server is HTTPS not HTTP
This is already supported by RSolr. Just set your url with the https protocol and the port to 443.
You can see how it works here: