Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_61530 ( "Bow number" text, "Ship name" text, "Launched" text, "Commissioned" text, "Service" text )

### Question ###
When did the ship that was commissioned July 1948 with a bow number of ps-31 launch?

### Accurate SQL ###

SELECT "Launched" FROM table_61530 WHERE "Commissioned" = 'july 1948' AND "Bow number" = 'ps-31'