A few things

I'm not a movie critic or a genius, the stuff below is my opinion/take on the matter (having recently viewed it) it is certainly not etched in stone, take it for what it's worth.

1. As far as I can tell, the shuttle is _the_ link to the rest of the solar system, humanity, etc. So on board would be new workers coming to start their year, or visitors, technicians, whomever. As well as supplies.

2. The deal with the drug is -mostly- a question of economics. I interpretted it to be - you get a year of work there, you earn based on your productivity, perhaps with bonuses for jobs done ahead of time, or a certain quota, since they make the 'company' (or companies) more money. Those bonuses extend to the management, not just the grunts, so it's in _everybodies_ interest to make it work.

The drugs (ostensibly) cost less money (at the very least at the start) than the extra productivity they enable, so for at least some of the workers, perhaps most, the choice is simple. It's perhaps a little like smoking (if you will go along with this example purely for the sake of explaining the plot, I don't wish to engage anyone in a pro or anti tobacco argument, it's none of my business) - the first cigarette, the first hundred, the first year won't have any significant health impact, which is _why_ no teenager is going to give a damn about such risks, it's years later when the side effects start to show that they find that they've smoked so long they are addicted and have real trouble quitting, if they do at all.

Well it's similar for this fictional drug. They all think 'it's only a year' and with that money they're set for life or can use it to buy into a business, or whatever and live comfortably. Once under the influence of the drug, especially longer term, they'll start to think they are invincible, and those 'few' that went nuts on the drug were just weak minded, but 'they' will be able to handle it.

I recall seeing a tv cop drama - where one sub plot was based on real life police experiences. A new 'deadly' batch of heroin had hit the streets. Too strong, too pure. With junkies dying left and right, one would think they'd all shy away from whomever was selling that particular batch or type or whatever (forgive me I don't know the right vocab). In actual fact the exact opposite happened. All the hardcore long time junkies atually went _looking_ for that bad batch, because they felt that they had a tolerance for it, and could handle it and _for them_ it would be the ultimate ride and they'd survive just fine. Of course the reality was different.

Perhaps the important thing to note is that nobody 'chooses' to be a junkie, they might 'choose' to have one hit, and like it, perhaps smoking or snorting it. then they have it again at a party, and like it, and have it at the next party, then they can't go to a party without it. then there's that one time they can't get it together to go to work on a monday, so they have a little bit, then the same the week after, then a little on tuesday as they still aren't tip top. Then snorting it isn't giving them enough of a hit to get them through, and it's getting expensive, so they start injecting, as they get more mileage from each hit. and so it goes on. Now ABSOLUTELY, they are making the choice each and every time, but it's not some _instant_ choice of 'hey I'll be a total write off' it's small steps.

No doubt it's the same sort of thing being played out in outland, with the exception (compared to my example, though I do note that similar stuff does go on in some countries where they use stimulants to work longer shifts, or do work they otherwise couldn't do - for example prostitution - some can do it, others can't do it 'sober') that it's initially done for work/economic reasons, not just a sort of euphoric party drug.

One thing that is similar, the dealers further up the chain (obviously some lower level ones would be dealing to support their own addiction) know only too well the social impact, and happily trade in death or at the very least misery, for the dollars. When you add up (in the real world) the cost to the community - a $1000 tv or stereo stolen for a $50-100 quantity of drugs, assaults, muggings, the burden on health care institutions - the dealers know all that, and happily facilitate all that damage - they probably lead to a few hundred dollars of impact for every dollar of drug they move. And considering they move hundreds of thousands, if not millions of dollars worth of the stuff....

So it is much the same thing displayed, albeit it slightly restructured into a good vs evil western style genre - good sherrif in a crooked town - in outland.

As for how many were 'in on it' - probably many - since it's a big money - there's not a lot of money in being honest (in this context). Presumably the higher ups, shift managers, formen, would know more, as would those near the end of their time on Io - those more likely to actually have used it to some extent. No doubt there'd be those who didn't touch the stuff, but they'd be earning less, and in such an enviroment, esp with a few lawmen on the take, they'd have to just knuckle down and not cause too much of a stir about it.

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After the ending, I'm guessing Sheppard would _have_ to be made a scapegoat. They company would know and (tacitly) allow the drugs to go on, or would have under his watch, because it made them more income. But now that it's blown up big time, they'd have to make an example out of him. I would speculate they'd even promise him or family/friends some sort of under the table payment to keep his mouth shut, or take the weight of the blame. An Oliver North or soemthing (though he likely did what he allegedly did because he was a patriot and had courage - not that I necessarily agree or disagree with that whole scenario. Maybe he'd even play both sides, and take that hush money, but also threaten exposing those further up the chain that did know about it, and end up with the best legal representation, or a sentence that actually meant the possibility of parole before he died or was too old to enjoy it.