CREATE TABLE table_name_30 (not_usable INTEGER, block VARCHAR(255), launch_failures VARCHAR(255), retired VARCHAR(255))
What is the highest number of not usable satellites when there are more than 0 launch failures, less than 30 retired, and the block is I?
    
SQL: SELECT MAX(not_usable) FROM table_name_30 WHERE launch_failures > 0 AND retired < 30 AND block = "block i"