The museum does not require ID to enter, however as LaShandra mentioned you do need a pass to enter on weekends but do not require one during the week. They are going into their busy season so obtaining timed weekend passes online will become more difficult. If you're an early bird, the ticket office gives out timed entry passes if you arrive by 9am but the entry passes may not be until later in the day.
I am fairly certain that Vets/retirees can get in with guests without a ticket. I don't recall the total number of guests they can bring with them though.
The museum is free, however weekends requires a pass which is easy to obtain from the website. I was able to get one 2 hours before I went. The passes are for timed entry. You do not have to go at that exact time but you will not be able to get in before the time indicated in the pass. You may want to try to go during weekday and go early- there is a lot to see.
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