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_15944_5 (specific_impulse__s_ INTEGER, effective_exhaust_velocity__m_s_ VARCHAR)

### Question ###
What is the maximum specific impulse with a 4423 m/s effective exhaust velocity?

### Accurate SQL ###

SELECT MAX(specific_impulse__s_) FROM table_15944_5 WHERE effective_exhaust_velocity__m_s_ = 4423