I've started a campaign with Rogue Trader as Gamemaster, but now, after few months of playing, I've some problem:

1) The Rogue Trader player don't let the other player to do almost anything without his permission. He's arguing that he's responsible of the entire ship. How can I make him understand that a Rogue Trader trust his camrades (the other players)?

2) In ship combat, a PG could fire with a total BS of 70+ (with many bonus from RT, augury and so on), much more than NPC vessel. How I can make the ship combat more challenging?

3) In the last session I let the PGs to buy at black market some archeotech, but it was a fake. When they discover that it was a fake, they go to kill the vendor. I've decided that now the vendors crime organization (he's not the leader, but still a member) would set a bounty on the PGs. Is that to much?

4) A player know too much of the WH40K universe, and, with his comment, break up some interesting subplot like one of the voidsmen being taken by a strange lady who follow some strange rites (she was close to Slaanesh Cult). How can I block this sort of spoiler?

Thanks! And sorry for the bad writings, I'm Italian!

1) The Rogue Trader is first among equals. The other player characters are there because their skills supplement his own. If he wants to play that sort of game, let him. Then let the Arch-Militant tell his security forces to stand down. Permit the Explorator to let the engines cease their toil. The Astropath should refuse to transmit any message. The Navigator can seal himself in the Nest and refuse to guide the ship. The Voidmaster can remove his hands from the rudder and let the captain pilot himself. Ascension has several pages dedicated to making sure everyone understands this, and how to avoid the pitfall of making one player think they have the right to boss the others around. Quick snippet repost of the most cogent part:

Group Direction
Does the fact that, in the game, the Inquisitor is in charge mean that the player that is playing the Inquisitor is also in charge? This is an important question for you to consider before running ascended games of Dark Heresy. It is a question of who sets the direction of the Cadre within the game. The fact is that the character of the Inquisitor is undoubtedly in charge, in the game world. It is also a fact, however, that unless you are running a very unusual group, the person playing the Inquisitor is not, in reality, a highly experienced investigator, leader, master of politics and warrior all rolled into one. They are also, in the real world,
one of a group of players who they are quite definitely not in charge of. In other words, the in-game and out-of-game situations are poles apart, but the impact of decisions made by the Inquisitor’s player are not just restricted to the world of the game.

While the most intuitive answer is to say that the person who is playing the Inquisitor is in charge, there are other ways of setting up the power structure within the group. The ones that are touched on here include: making use of out of character decisions by the group, and the Game Master giving the Inquisitor player open advice on what is possible and expected within the game. Ultimately the answer to the original question is up to you, but it is vital that you consider
not only the needs of the Dark Heresy setting, but the needs of you and your players for an arrangement that is enjoyable and comfortable for all.
Making Decisions
How important decisions are made is the central issue of how playing an Inquisitorial Cadre either succeeds or fails. Decisions in this context are not those made about whether the Death Cultist should take her matched power blades or power sabre, but are those concerning what the Cadre is going to do. For example a Cadre may have information that the servants of a renegade Inquisitor have infiltrated the Arbites on Landunder with the aim of freeing a heretic held in the Arbitrator oubliette on that world. Is the Cadre going to charge in and conduct an aggressive purge of the Arbites, or are they going to infiltrate the Arbites and see if they can learn more of the renegade’s intentions? This is a decision that effects the direction of the game. It must be clear for everyone who has the final call on this type of decision. In the game world, of course, the Inquisitor would make such a decision or deliberately delegate it to a servant because of their expertise. In the real would of the gaming group, however, simply defaulting to having the Inquisitor player make this decision has risks. First it takes away the involvement of the other players in the direction of the game they are playing in. Secondly it places a lot of pressure on the Inquisitor player to
make a good decision.

Using Out of Character Consensus
A very satisfying alternative to having decisions rest with the Inquisitor’s player is to have all players discuss decisions that affect the direction of the game, then make a collective decision on what course of action the Cadre should take. If there are several differing views amongst the players, get them to take a vote, with the Inquisitor’s player having the tie-breaking vote in the case of a deadlock. This discussion, and decision, should be made out of character with the players discussing the situation as players rather than as characters. Once the decision has been made out of character, the group consensus then becomes the in game decision of the Inquisitor. The only potential downside of this method is that it removes some of the Inquisitor’s decisions from his player’s control.

The tl;dr version of this is that you should first of all discuss this with the person playing the Rogue Trader. Explain that while he might be roleplaying how his character would react, it negatively affects everyone else's fun, and ask him to dial it down a bit. While he is the Lord-Captain, the other PCs are important too.

2) Your first option is to increase NPC skills. I tend to give +20 to one skill and +10 to another, ie Tech-Use and Ballistics Skill. I've been doing this and it's worked out quite well so far. However your major problem is that damage scales far more for the PCs than it does for NPCs. There's a simple solution for this too: reduce ship armour by 12, but have that armour apply to every hit . Lances ignore armour as per normal and broadsides get the Storm quality. Evens things out quite nicely.

3) Not at all, that's an appropriate step to take. It's something I've done myself once or twice. Most black-market types will not escalate to a full-scale war if it came to that, however. They'd more likely just send assassins to do away with the RT or someone he cares about.

4) Two things. Red herrings and Lore tests. The player might know the symbol of Slaanesh when he sees it, but unless his character succeeds at a Forbidden Lore (Warp) test he can't do anything about it. Red herrings shouldn't be used too often, but just because they saw someone performing a particular set of actions doesn't mean that she's Slaaneshi. Maybe it's just a custom where she's from. Hell, maybe it is a Slaaneshi rite but she's just slumming it, getting off on how wicked and decadent she's being by using the 40k equivalent of an ouija board. Unfortunately for the players, they find out she's the planetary governor's daughter shortly after one of them pulls their power-sword out from her chest...

1) I second Errant's point on this issue. I'll also say that rather than explaining this to the Rogue Trader player, explain this to all the other players. Let them know how much power they have, and make it clear that the Rogue Trader's operations cannot continue for more than a fleeting moment without the participation of any of the other Explorers.

2) Unless the Explorers are going out of their way to seek out easy prey, make the NPC ships at least a well armed, well crewed, and well lead as the Explorer's own. Likewise, learn how players fight space battles and remember that a successful strategy doesn't stay secret for long. If the players come up with good tactics that swings the odds in their favor, have the NPC ships start using that tactic. When your players become over reliant on a specific tactic, have the NPC ships anticipate that tactic and counter it. In my own campaign the Explorers became over reliant on running up on ships from behind and unleashing nothing but Hit-And-Run attacks. Their enemies wised up and starting dropping mines and trailing fighter craft behind them. Also, remember that as long as a ship's Warp Engines and Gellar Field function, it can always flee into the Warp to fight another day.

3) I don't consider that too much. It sounds appropriate. If the Explorers make powerful enemies they have to expect those enemies to strike against them, even if it means keeping their hands clean by using a bounty to entice others to do the striking. It's happened in my own campaign a few times as well.

4) This can be solved by making up some of your own lore for your campaign, or by using a little bait and switch. In the example you sighted, all signs point to a Cultist of Slaanesh. But the attractive woman who practices strange rites doesn't have to be a cultist of Slaanesh. Chaos takes many forms and is inherently deceptive. An attractive sorceress can just as easily be a cultist of Nurgle, a pretty package meant to deliver the worst social diseases. Also, don't be afraid to make the players questions what they really know. The Expanse is just one small corner of the galaxy, and the beings your Explorers encounter can always be the acceptation to the lore.

Thanks for the reply! This week I will talk to the player.

Let us know how it goes.

I had the same problem, the one with the RT being an ASS... so I took a bad turn and killed of his char and got an NPC captain for them, but then they got to dependant on the NPC's orders, after that I made an other player into the RT, but he turned out to have to loooong plans, so the other players couldnt do anything, as the ship didnt move and there where interesting stuffs where they where, and even if I said something interesting the RT didnt want to go there untill he finished what he started... so I needed a hard reset on the cars, and they all made new chars and got on a new ship, where again an NPC is captain, because nobody wants to be RT because the power goes into there minds... but again, if a social or trade situation comes up, they say: let the captain handle it... so thats one of the reasons I send them to a Feudal world, you can read about it in my other topic... but I want to have a leader char, but dont know how I could give them a ship, and a minimal PF without killing of my NPC... maybe giving them a warrant for reward and a small raider from the RT as a present? and have the RT as callable ally?

ohh and a bit off topic question, in "into the storm" there are ranks like captain, weapon master, and so on, that give bonuses, the captaion gives an a bonus as the RT class gets, is it stackable with the RT speciality? and can any player class be a captain, I dont need to change the class of the char, just give him a warrant?

That sort of situation, where the Rogue Trader wants to babysit every little plan he has in a location, is best handled by Background Endeavours. It allows him to plan everything out in detail (outside the session if need be), make his Command roll and then let it go so that he can go handle other things that the rest of the group finds interesting.

The Lord-Captain Ship Role confers a bonus to Hold Fast! and allows you to give the Exceptional Leader bonus to anyone aboard the vessel, it is NOT an extra bonus of the ability, nor does it allow you to use it twice. It also doesn't require a warrant.

Errant said:

Well... true, it could have been a background stuff, but the RT insisted on staying, even if skipping that part, but the other players didnt want there chars to stay idle and do nothing...

btw, if you skip some time, lets say 3 months on smaller trade runs close to the imperium, or some healing of one of the party members, then what could the other chars do in that time, I mean they can upgrade items and craft and so own, but how can I fix them better on some parts of the ships jobs? because my players mostly try to get away from there jobs, and if I tell the pilot that he should pilot the ship, then he just says that he has better thing to do and there are other pilotes too... he only wants to fly the ship when there is action, and when an NPC srews up he is totaly mad, that they cant even do a little piloting in bad situations, because the NPC's have kinda low stats compared to the PC's and for the NPC's I roll and usually its kinda bad rolls XD

how could I improve his behaivor?

Don't give him an option; "Okay, you want to organise this, this and this. Your current resources will make that a Command test at +30, if you're able to make an Acquisition to get some more specialists. You'll be informed of the results of the operation when it's done. Now, Player 2 wants to pursue the assassins that made an attempt on his life..."

Hmm. Depends on the player and the character, I guess. The first thought that comes to mind is organising a test of skill amongst the pilots on the ship. Have the player run drills on the crew to come up with an alternate for when he has other things to do. I'd run it as a Skill Challenge, combining Command, Pilot, Scrutiny, maybe some other skills. Depending on how that goes, bump up the Pilot skill level of the ship by a few points or grant a few rerolls for Pilot tests to reflect that. Unfortunately, a situation like that tends to result in poop roleplay (One player in a group of rollplayers describes going off into the bushes to handle the call of nature, GM awards a few experience points. Next thing you know the entire party's voiding their bowels all over the place. Fun times.)