Oh! I see, sorry.
Well first off, while I like Earthforce as a campaign idea, placing the PCs into a command structure is usually difficult, PCs being what they are. However, if everyone goes in eyes open and there aren't many personality conflicts (or if everyone is ok with the command structure and taking orders sometimes) it should work out.
Had you planned on having a PC captain? Presumably not at first, but it's something to plan for, seems like a good chance for an act break or character development. Though I suspect it'd take a lot of work to make sure the right PC was in command.
1st level characters get turned loose on anything. Gotta start somewhere, after all. The trick is not their level, but the challenges you give them. For instance: my group was surveying a planet for IPX solo at second level. The challenge wasn't combat oriented, but diplomatic when they negotiated with the natives for rights to survey the ruins and exploit the mountains for the crystals. They had some planning to do to survive the trip up the mountains, and there were some complications later with the arrival of an alien resupply vessel, but none of this was focused on anything complicated or requiring high DC skill checks. So it comes down not to challenge ratings but more tailoring the exploration encounters to fit your PCs' skills and HP totals.
In addition, if you've got 1st level PCs in a military-based campaign, you can have the added reward of promotions to go along with leveling. Not one for one, but it's another carrot for the PCs, and you can never have enough carrots.
You can get the group together with the usual methods, just translated to space. Another example from my campaign, if you can stand it: they started on an economy flight from Proxima to Mars. Once they were safely in hyperspace and escape was impossible, someone got shot and the PCs stepped up to try and figure out who and why (mainly because they were mostly shady folks themselves and didn't want to be blamed). During the investigation, the IPX public relations rep on board noticed that they were a good group and offered them a job, and thus a career was born. (there were plenty of other job offers available, from a tech runner to a Markab True Seeker, but IPX paid the best up front.)
Traditionally, start them off with a bang, and make sure they have plenty of reason to work together long enough to forge some bonds. Once you take the pressure off, you don't want them going their separate ways. If it's a strictly Earthforce campaign, though, it's easy to get them together and keep them together. Captain says work together, they work together.
Hope that answers your question a little better!
(And if you are ever in the market for a B5 player, drop me a line. I enjoy pbp gaming and no one near me is running B5.)
was more to do with how have you gotten the characters together...
as it were.
