To answer your questions:
1. How is combat/ damage decided: As Cam stated, the GM generally lets the player calculate the damage done to that player’s force and decide how it affects each of the players ships. We do have guidelines though for how much damage should be done and the GM will review the players post, if the player is underreporting his damage the GM may send a private message to the player and discuss the matter with him, or the GM has the option of adding additional damage to the player’s fleet.
The GM will also calculate the damage to the kilrathi forces using these guidelines and post that damage in the Kilrathi forces response. Sometimes the GMs miss things or forget about player actions. If this happens the player can message the GM and let the GM know, the GM will then correct his post.
We also have guidelines for how long it takes to repair damaged ship and ship components.
2. Length of turn: As a forums based game we do not have a set length of turn. Players may respond to the kilrathi forces post within 24 hours or a week. We do try to keep things moving though, and if a player has not posted in awhile, usually over a week, we will send them a private message just to check on them. That way the GMs can adjust the direction of the plot and kilrathi actions based on the number of players who are active.
In combined fleet actions, those involving more than one player, the GMs will allow another player to temporarily make decisions for a player who is absent for an extended period of time in order to prevent the other active players from getting “stuck” having nothing to do while they wait for the other player to post. We will try to ask for permission from the inactive player before we do this though.
3. Do you have to be online?: No you don’t have to be online IM ing when you post. You can log in, make the necessary posts to the forums and then log out. But you don’t have to be online or make your posts at a set time.
4. Is there a position for novices?: We have been starting new players off in the Gemini Sector fleet where they can learn the game and gain experience before being transferred to one of the other sector fleets. The GMs are also more forgiving on a new player in their first battle and generally have the battle favor the confederation player rather than the kilrathi.
When players are ready to move out of the Gemini Sector fleet, or at any time after that, they also have the option of requesting transfer to the Open Exploration Campaign. This is where they are free to move to between sectors and work with forces in any of the front line sectors. They can even try to slip behind the lines and raid kilrathi convoys or bases.
5. The rules thread, which is posted in our orientation forum, may help in answering more of your questions. It can be found here:
http://wcaao.rpwsg.com/board/viewtopic.php?t=488
We also have a thread in the same forum outlining the steps to get started.