My DH does a different job, but it's one where he is away more than he's home. He went back to it when DS was 4 weeks, and I was really dreading it. (DS is now 16 months) He's usually only away a week at a time, but then often is only back for a day before going away again, and has just done a 11 week stretch where he was only home for 12 days in those 11 weeks. So I know what it's like. I also don't have any family around, they all live several hours away.
I found that once I got over the initial few days, we actually settled into an ok routine, which worked. It changed when DH was home, but it made it manageable, and was less horrific than I thought it would be!
I tried to make sure I saw someone everyday, meeting antenatal group friends, or even going an meeting old work colleagues for lunch. Anything to make sure I saw and talked to another adult sometime in the day!
Being organised too. The first night I got to 4am and I hadn't eaten tea, still had makeup on and was in that days clothes... So I learnt I needed to make sure I had enough meals in the freezer for when he went away, making sure we cooked extra portions when he was home. Bought loads of microwave rice packets, and lived on stuff I could heat up in a few mins when DS fell asleep. I also made sure I was in pjs and makeup off etc late afternoon / early eve so I could just climb into bed whenever I got the opportunity.
If you can afford it, get a cleaner! Or just accept that you can only have two of the following three: sanity / happy child / clean house!!!!
And having a couple of mates that you can call on who can come and just hold DS whilst you eat or whatever if you are having a really really crap day.
I found it hard not to be resentful of friends who had DP who came home every evening. They always would say they didn't know how I coped, and I'd be all "oh it's fine".... And often it was... It really hasn't been as bad as I thought it might be. And it does get easier when they are a bit older and can play a bit on their own.