J2

J2, J.II or J-2 may refer to:

Codes and classifications

, the Earth's second dynamic form factor in the Nodal precession

People and organizations

Rocketdyne J-2

The J-2 was a liquid-fuel cryogenic rocket engine used on NASA's Saturn IB and Saturn V launch vehicles. Built in the U.S. by Rocketdyne, the J-2 burned cryogenic liquid hydrogen (LH2) and liquid oxygen (LOX) propellants, with each engine producing 1,033.1 kN (232,250 lb_f) of thrust in vacuum. The engine's preliminary design dates back to recommendations of the 1959 Silverstein Committee. Rocketdyne won approval to develop the J-2 in June 1960 and the first flight, AS-201, occurred on 26 February 1966. The J-2 underwent several minor upgrades over its operational history to improve the engine's performance, with two major upgrade programs, the de Laval nozzle-type J-2S and aerospike-type J-2T, which were cancelled after the conclusion of the Apollo program.

The engine produced a specific impulse (I_sp) of 421 seconds (4.13 km/s) in a vacuum (or 200 seconds (2.0 km/s) at sea level) and had a mass of approximately 1,788 kilograms (3,942 lb). Five J-2 engines were used on the Saturn V's S-II second stage, and one J-2 was used on the S-IVB upper stage used on both the Saturn IB and Saturn V. Proposals also existed to use various numbers of J-2 engines in the upper stages of an even larger rocket, the planned Nova. The J-2 was America's largest production LH2-fuelled rocket engine before the RS-25 Space Shuttle Main Engine. A modernized version of the engine, the J-2X, is intended for use on the Earth Departure Stage of NASA's Space Shuttle replacement, the Space Launch System.

J-2 visa

A J-2 visa is a non-immigrant visa issued by the United States for spouses and dependents of J-1 exchange visitors.

Employment Authorization

J-2 visitors may request work authorization from United States Citizenship and Immigration Services (USCIS) by submitting form I-765. Adjudication typically takes between 3 and 5 months.

If approved, an Employment Authorization Document (EAD) will be issued, authorizing the J-2 visitor for employment for a period of up to one year. Applications for additional employment authorization may be submitted annually until the end of the J-2's status. However, some J-2 visa holders reported receiving EAD cards valid until the end of their J-2 visa.

Academic Enrollment

J-2 visitors may enroll in academic programs as recreational or degree-seeking students. There are no enrollment requirements associated with J-2 status; students may enroll full- or part-time and discontinue their program at any time. J-2 visitors who have not completed their academic program by the time the principal J-1's status ends may petition for a change to F-1 student status, provided they are not subject to the Two-Year Home Residency Requirement. Not mentioned about the duration of this visa