CREATE TABLE table_15944_5 (effective_exhaust_velocity__m_s_ VARCHAR, scenario VARCHAR)

What is the effective exhaust velocity in a Space Shuttle Vacuum?
SELECT COUNT(effective_exhaust_velocity__m_s_) FROM table_15944_5 WHERE scenario = "Space shuttle vacuum"
SELECT COUNT("effective_exhaust_velocity__m_s_") FROM "table_15944_5" WHERE "Space shuttle vacuum" = "scenario"