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USS Jupiter (AK-43) circa 1942-1943
Click on this photograph for links to larger images of this class.

Class:        MERCURY (AK-42)
Design:        MC C2 (Federal)
Displacement (tons):        5,994 light, 13,900 lim.
Dimensions (feet):        459.2' oa x 63.0' e x 25.8' lim.
Original Armament:        2-3"/50 4-20mm (1942: AK-42)
Later armaments:        1-4"/50 1-3"/50 0<8-20mm (1942-43: AK-43);
1-5"/51 1-3"/50 8-20mm (1942-43: AK-42);
1-5"/38 4-3"/50 8-20mm (1943-44: AK-43, and 1945: AK-42); 1-5"/38 4-3"/50 2-40mmT 8>4-20mmS (1945-47: both); 1-5"/38 4-3"/50 2-40mmT 4<8-20mmT (1947-51: both); 1-5"/38 4-3"/50 (1957: AVS-8);
4-3"/50 4-20mmT (1958-59: AKS-20);
2-3"/50 (1959-61: AVS-8)
Complement:        173 (1944)
Speed (kts.):        16.4
Propulsion (HP):        6,000
Machinery:        G.E. turbine, 1 screw

AK Name Acq. Builder Keel Launch Commiss.
42 MERCURY 26 Jun 41 Federal SB & DD, Kearny 3 Jan 39 15 Jul 39 1 Jul 42
43 JUPITER 25 Jun 41 Federal SB & DD, Kearny 16 Mar 39 30 Sep 39 22 Aug 42

AK Name Decomm. Strike Disposal Fate MA Sale
42 MERCURY 28 May 59 1 Aug 59 30 Jun 60 MA/R 5 Mar 75
43 JUPITER 1 Aug 65 1 Aug 65 1 Aug 65 MA/R 12 Mar 71

Class Notes:
FY 1942. Called C2-Cargo by the MC, probably similar to the builder's later C2-F. On 29 Apr 41 the CNO's War Plans Division listed 33 merchant ships that the Navy would need to carry out the initial movements for which commitments had been made and to give early support to U. S. forces beyond the continental limits. Most of these ships, including the 5 cargo ships on the list, were required before 1 Aug 41. On 10 May 41 the assistant CNO directed the Auxiliary Vessels Board to review and update this list and the Board's own earlier recommendations of 11 Feb 41. In its report of 14 May 41 the Board also came up with a total of 33 ships but increased the number of cargo ships to 10. These were to be fast (15 knots or better) ships such as the EXCHANGE or EXCELLER classes or regular C2 or C3 ships. On 26 May the President increased the number of cargo ships again (probably to provide hulls for two ADs requested by the Navy in January but not yet provided) when he directed the Maritime Commission to turn over to the Navy 19 ships including 12 cargo ships of 15 knot speed. Nine were to be turned over immediately and three by 30 June. The first group (all duly acquired between 29 May and 6 June) became AK 23-31and the last three, acquired a few weeks later, became AK 41-43.

The Navy was unable to find crews for all twelve of the new cargo ships, given the many other ships being taken into the Navy at the same time, and while it promptly took ownership title to AK 41-43 it then turned them over to private firms for operation by merchant crews. As Navy-owned but civilian-manned ships they were designated "U.S. Naval Cargo Ship" instead of "U.S.S." Initially the Matson Navigation Co. operated AK-41 and AK-43 in the Pacific and Agwilines, Inc., operated AK-42 in the Atlantic. In December 1941 the two ships in the Pacific were assigned armaments of one single-purpose 3", 4", or 5" gun while the ship in the Atlantic was to get 2-3"/50 double purpose guns, all three also getting eight anti-aircraft machine guns.

MERCURY (AK-42) received an armament of 2-3"/50 (one forward and one aft) and 8 anti-aircraft machine guns at the Charleston, S.C., Navy Yard between 23 and 26 January 1942. In May 1942 MERCURY's travels took her to San Francisco, which was outside the operating area of Agwilines and where an inspection showed that her armament was in unsatisfactory condition. The Navy initially planned to find her another commercial operating agent for operations in the Pacific but ended up instead placing her in commission with a Navy crew after an overhaul during which her crew accommodations were expanded and her armament was upgraded to include a 5"/51 instead of the after 3"/50 and 8-20mm guns in place of her machine guns. For one of her cargo runs temporary deckhouses to accommodate passengers were added on either side of hatch no. 4 aft of the superstructure, and she retained these for the rest of the war. Operational control of AK-42 was passed to ComServPac in January 1944 for service with the 5th Amphibious Force and she subsequently supported several major amphibious assault operations by carrying both troops and their equipment to landing sites. In February 1945 she was reassigned to ComServRon Ten and was ordered to be fitted as a GSK (General Stores) issue ship with the capability to transfer the stores at sea. To accomplish this all obstructions on the tops of her cargo hatches and adjoining deck areas, including all but one of her LCM and LCVP landing craft, had to be removed to provide adequate working space for the transfer at sea crews. After these improvised modifications were carried out at Ulithi, AK-42 replenished fast task groups at sea between March and May 1945. The ship began a full conversion to an AKS (Stores Issue Ship) with underway replenishment capability at the Hurley Marine Works, Oakland, Calif., in June 1945 and was reclassified AKS-20 effective 30 Jul 45. During this conversion her armament was finally upgraded to the standard for naval auxiliaries, 1-5"/38 and 4-3"/50, two 40mm twin mounts may also have been fitted, and her 20mm guns were redistributed to help clear the main deck of obstructions. The conversion was completed in September 1945 and MERCURY then saw continuous active service in the Atlantic Fleet until being decommissioned in 1959.

JUPITER (AK-43) received her initial armament of 1-4" and 1-3" in the San Francisco area in April 1942. In July 1942 the Navy decided to commission the ship upon her return to San Francisco in August, although she was to receive only a minimal conversion and her armament was not to be changed until her services were not so urgently required. This conversion was carried out by the Mare Island Navy Yard. Mare Island probably upgraded her armament to a standard naval auxiliary outfit of 1-5"/38 and 4-3"/50 in September 1943. AK-43 was reassigned in April 1944 to the Pacific Fleet's 5th Amphibious Force and she subsequently supported several major amphibious assault operations by delivering cargo and troops to the landing sites. In June 1945 ComAirPac advised CinCPac that the aviation supply ships then assigned to AirPac were too slow to operate with logistic support groups and that these groups needed an AVS to support carriers on extended periods at sea without return to fleet anchorages. He recommended converting a fast AK to an AVS fitted out similar to GRUMIUM (AVS-3) but with an underway replenishment capability. On 5 Jul 45 CinCPac recommended that AK-43 be reassigned to ComAirPac and converted. CNO reassigned the ship on 11 Jul 45 and on the next day recommended her reclassification to AVS-8, to take effect 31 Jul 45. The conversion was carried out by Amship Corp., Alameda, Calif. between August and October 1945 and was completed by the Navy's yard at Hunter's Point between October 1945 and January 1946. During this conversion her crew accommodations were expanded, four transfer stations were installed for transferring at sea stores and large aviation items like spare aircraft engines and wing surfaces, her main deck was cleared of obstructions, her cargo spaces and hatches were modified, her 20mm mounts were relocated and two 40mm twin mounts may have been added to her armament. JUPITER was placed in reserve in 1947 but was recommissioned in 1950 and then served continuously in the Pacific until 1965 as the Navy's only aviation stores ship.

Ship Notes:
AK Name MC# Notes
42 MERCURY 16 Ex merc. MORMACTERN, ex LIGHTNING 1940 (ID-4997B, completed 29 Sep 39). To AKS-20 30 Jul 45. To NDRF 5 Apr 60. To buyer 7 Apr 75.
43 JUPITER 17 Ex merc. SANTA CATALINA, ex FLYING CLOUD 1940 (ID-4997C, completed 1 Nov 39). To AVS-8 31 Jul 45. In USN reserve 1947-50 (decomm. 23 May 47, recomm 10 Oct 50). To NDRF 25 Jun 64. To buyer 30 Mar 71.

Page Notes:
AK        1941
Compiled:        10 Jan 2010
© Stephen S. Roberts, 2002-2010