It's possible to simply store the luks password in a file.
I use this on my home computer; The root file system lives on a regular luks volume which I unlock with my passphrase at boot. An additional drive contains a luks volume with a generated password.
This additional volume is unlocked by a password file which lives on the encrypted root file system. It is automatically unlocked during boot if the root file system is unlocked.
/etc/crypttab looks like this:
crypt-root UUID=c5a2cf25-0aae-457e-874f-fca7ea3d5742 none luks
crypt-data UUID=96d79323-246d-49e0-9149-ec3a4cfc1c1e /etc/crypt-data.key luks
The third field is the keyfile,
none for the root filesystem, but
/etc/crypt-data.key for the data filesystem.
/etc/crypt-data.key contains the luks password:
Note, a newline or any other white space will be taken as part of the password! Take care to generate this file without trailing newline. Also, ensure it has strict permissions:
-rw------- 1 root root 59 Sep 14 23:57 /etc/crypt-data.key
You should be able to duplicate this approach for multiple volumes (either with distinct passwords or one shared password, your choice).