Reusable stages weigh more than equivalent expendable stages. Ariane is a series of a European civilian expendable launch vehicles for space launch use. A number of alternatives to expendable rockets have been proposed. The payload capability was to be in an expendable configuration or in a reusable configuration. However, the expense of operating an expendable system was not satisfactory. The Unha is a North Korean family of expendable carrier rockets. The ramjet was strictly expendable and easily replaced. Drop tanks are generally expendable and often jettisonable. SpaceX is also certified for US military launches of Evolved Expendable Launch Vehicle-class (EELV) payloads. Eventually the military resumed the use of expendable launch vehicles instead. Among their crews, CVE was sarcastically said to stand for "Combustible, Vulnerable, and Expendable". Less-senior officials were more expendable. TDRSS is also used to provide launch data relay for expendable boosters. It is normally used when there is a recurring need for expendable goods. The second stage is intended to be expendable.