Okay, I've had a thought:
While reading the Terms Of Service on user generated content
https://robertsspaceindustries.com/tos#rsi_content (terms you are already bound to) it struck me that if you can't get them to read or endorse your book, you can legit apporach them for permission to make a cover for your book using official RSI imagery. They still might not read it, but it may open the door to negotiation as to what they want from you in promoting it and what you may be able to get from them even if it's just a little shout-out on the twitter or something.
Whaddya think, a last roll of the dice? They potentially get their "Community Made" sticker on the corner of the cover and you get some actual dialogue going with them?