Some were in civilian clothing. One wore a uniform complete with a rank pip (the black or "hollow" one also found on Chief O'Brien's neck).
FWIW, it seems that out of all the personnel aboard the NX-01, the security goons with the plasma and later plasma/phase rifles were the most competent and successful. Phlox didn't appear to have staff; there were no scientists aboard worth mentioning; Trip's little people mainly fell off catwalks; but the security guys and gals hit their targets, didn't get knocked out in fisticuffs or surprised from behind, and generally achieved all that was achievable in a combat situation, neck to neck with Reed the hero character.
I guess that when Archer left Earth in a hurry in "Broken Bow", Security was the one department that both he and Starfleet insisted be fully represented and equipped; the rest could be picked up when Archer returned. Alas, it took two years for that to happen.
Timo Saloniemi
FWIW, it seems that out of all the personnel aboard the NX-01, the security goons with the plasma and later plasma/phase rifles were the most competent and successful. Phlox didn't appear to have staff; there were no scientists aboard worth mentioning; Trip's little people mainly fell off catwalks; but the security guys and gals hit their targets, didn't get knocked out in fisticuffs or surprised from behind, and generally achieved all that was achievable in a combat situation, neck to neck with Reed the hero character.
I guess that when Archer left Earth in a hurry in "Broken Bow", Security was the one department that both he and Starfleet insisted be fully represented and equipped; the rest could be picked up when Archer returned. Alas, it took two years for that to happen.
Timo Saloniemi