Can one archive directly to tape?

Yes, set log_archive_dest = /dev/rmt0:100M in your INIT.ORA file and recycle the database.

You can also use ARCHMON (when available) which communicates with the ARCH background process. When the end of tape is reached, ARCH stops and signals
ARCHMON to prompt the user for a new tape. When ARCHMON detects the new tape,
it tells the ARCH process to resume the archiving operation. ARCMON requires regular operator monitoring and intervention.

$ archmon @P:TEST