[HECnet] Can we hook this up to a VAX or something?

Correct, an RX02 floppy with a formatted capacity of 512 kB IIRC. Absolutely, on the 11/03 CFE. And any of the UNIBUS VAXen (730, 750, 780, etc) would directly support an RX01/02 on an RX211 interface. Such combinations were not unusual and were supported by VMS. I've got a 11/730 with an RX02 drive in the garage. Likewise any of the BI bus VAXen with a UBA could at least in theory do the same, though by that time 8" floppies were uncommon. Bob