Normally, I don't comment about stuff like the Mayhem-DoY thing. But I'm getting caught up on several months of posts and just came from the thread mentioned. My input is for the more senior CFC posters to take it easy on newbies (Mayhem has about 50 posts). He's probably learning "the ropes", judging from what I've read. Positive encouragement is better. In that vein (to Mayhem), it is uncool to tell someone not to post in a public forum. Let the axe be buried... it was a misunderstanding, and don't hold on to a dim view of Duke o' York, who in fact is a good dude. Likewise, vet (long-time) CFC-ers (all of us with hundreds of posts) should simply encourage Mayhem by refraining from sharpness in our comments, and give him a chance. It does not seem that he's looking to cause trouble, and he is likely learning the eitquette.
Oh one more thing, the PM (Private Message) system can be used to communicate feedback in Private. It would be a good thing for M & DoY to PM each other, since is in fact much ado about nothing!
BTW, Welcome to CFC Mayhem

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Now on topic: The Duke o' York is right, except for the correction pointed out by Smash. If you want to protect your SS after launch, then just keep more than one city and more then 1000 gold in the bank. A good tactic might be to deliberately move your palace to an out of the way location if faced with overrun. Simply rush buy a new palace... it's comparitively cheap (no more than 398 gold if you have at least one shield in the box to begin with).
A note about losing your capital: Your empire might be split, but I don't have any game experience with how that might affect your SS. A "normal" split results in a stronger faction (yours) and a slightly weaker faction (a newly created enemy which takes a little less than half your cities and some gold). I assume, but have not tested, you get to keep your SS if you lose your capital in a Split. Bottom line, don't lose your capital

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To expand upon Smash's early comments about success, the SS will always arrive once launched (assuming your capital survives somewhere).
Example: If you have a 78% "Probablity of Success" and you have 4 Modules, then you will get (upon SS arrival):
78% * (4 * 100) = 312 bonus points
These points will be added to your score.
So the "Probability of Success" really means "Bonus Points Percentage Multiplier" of your base cargo (the number of Modules times 100). Of course you can have 1, 2, 3, or 4 Modules, and so have 100, 200, 300, or 400 base boints.