It is affected by a number of successful trades, so if you make 100 trades and species are hostile and only half of the trades are successful, then the game will run 10% chance to get blueprint only for 50 trades. So, anything that increases success rate will help, other than that, there seems to be no modifiers.
Thank you, registration did appear, but when I tried to create an account there was an error stating that email configuration is invalid. On the second attempt there is an error stating that the account already exists. On login there is an error stating that I need to verify my account, but there is no message in my email (gmail) inbox. I suspect that the initial error was caused by a failure to send confirmation email and related to outgoing email configuration rather than my email address.
Understood, thanks for the reply.