Directory of U.S. Military Rockets and Missiles
Appendix 4: Undesignated Vehicles
Copyright © 2006 Andreas Parsch

5-Inch Bombardment Rockets (HVSR / BOMROC)

In May 1943, the Naval Bureau of Ordnance proposed the development of a new ship-to-shore rocket with a range of up to 9100 m (10000 yds). To be tactically useful, that rocket had to have a much lower dispersion than the short-ranged 4.5-Inch Beach Barrage Rocket. To fulfill such a requirement, the NDRC (National Defense Research Committee) recommended the development of a spin-stabilized instead of a fin-stabilized rocket. Other than air-launched rockets, which have significant forward velocity from the first moment of flight, surface-launched rockets start with zero airspeed, where fin-stabilization is ineffective. Furthermore, spin-stabilized rockets can be shorter and need no fins, making launchers with rapid automatic reloading capability much easier to design.

Development of spinner rockets began in mid-1943 at CalTech (California Institute of Technology). The first rocket was the 3.5-Inch GPSR (General Purpose Spinner Rocket), which was developed for the U.S. Marine Corps to replace the 75 mm pack howitzer. However the rocket's dispersion was too large, and it was therefore not adopted for service use.

Together with the 3.5-Inch GPSR, CalTech also developed a family of 5-inch spinner rockets, generally known as 5-Inch HVSR (High Velocity Spinner Rocket). Initially, three versions of the HVSR with ranges of 1140 m (1250 yds), 2290 m (2500 yds) and 4570 m (5000 yds) were planned, but in the end only the 5000 yd version, and a still longer ranged (10000 yds) variant, were put in service. A variety of different warheads was developed for the 5-Inch HVSR, leading to the following rocket types:

Sea trials of the HVSR eventually began in August 1944, and the first PT boats began to operate the rockets in spring 1945. In October 1944, the Navy had ordered the conversion of medium landing ships to rocket support ships (type LSMR) for the operations in the Pacific. Because the 5-Inch HVSR was not yet ready at the end of 1944, the first ships were equipped with launchers for fin-stabilized 5-Inch FFARs (Forward-Firing Aircraft Rockets).

Photo: via Ordway/Wakeford
5-Inch FFAR
(used as surface-to-surface rocket)

Later LSMRs were equipped with the spinner rockets. Because of the more compact size, significantly more launchers could be carried which could also be reloaded much faster. Of the various HVSR variants, the most numerous, and the first one to see service, was the HCSR version. The rocket was extensively used during the landing operations at Iwo Jima and Okinawa, and was eventually also employed by LCI- and LCT-type landing craft. Development of launchers for the 5-inch spinner rocket eventually culminated in the MK 102, a two-barrel launcher which could be continuously loaded from below deck, and trained and operated by remote control.

Photo: via ORDATA Website
5-Inch GPSR

CalTech and the Naval Ordnance Test Station (NOTS) unsuccessfully tried to develop air-launched derivatives of the 5-inch spinner rockets, known as CASR (Common Air-Fired Spinner Rocket), GASR (General-Purpose Air-Fired Spinner Rocket) and PASR (Pyrotechnic Air-Fired Spinner Rocket). In the first tests in late 1944, the rockets were completely unstable, and although the worst problems could be solved, the air-launched spinners were not better than the existing fin-stabilized aircraft rockets. Furthermore, the spinner rockets' bulky tube launchers were heavier and induced more drag than the simple posts which launched the finned rockets.

The 5-inch HVSR bombardment rockets were employed by the Navy through the 1950s and 1960s for landing operations and general coastal fire support. Later versions used improved rocket motors (MK 50 or MK 61), and were generally referred to as BOMROC. A typical BOMROC with a MK 50 motor and a MK 10 warhead was 74.9 cm (29.5 in) long and weighed 23.8 kg (52.5 lb). However, only a single new shore-bombardment ship was built after the war, the USS Carronade (IFS-1) in the early 1950s. It was a much larger ship than the original LSMRs, and its rockets were fired by MK 105 launchers, improved derivatives of the MK 102. In 1969, IFS-1 and the few remaining LSMRs were all redesignated in the new LFR (Amphibious Fire-Support, Rocket) category. Development of new rockets and launchers was discussed in the early 1970s, but eventually the LFRs, and with them the MK 102/105 launchers and BOMROC rockets, were phased out without a replacement. At that time, naval guns were regarded as adequate for ship-to-shore fire support.

Photo: via ORDATA Website
BOMROC 5-Inch Rocket


Note: Data given by several sources show slight variations. Figures given below may therefore be inaccurate!

Data for 5-Inch HCSR, 5-Inch GPSR, 5-Inch CnSR, BOMROC MK 50:

Length81.8 cm (32.2 in)80.2 cm (31.6 in)73.7 cm (29 in)74.9 cm (29.5 in)
Diameter12.7 cm (5 in)
Weight22.7 kg (50 lb)22.6 kg (49.8 lb)23.4 kg (51.6 lb)23.8 kg (52.5 lb)
Speed1600 km/h (1000 mph)?
Range4570 m (5000 yds)9140 m (10000 yds)?
PropulsionMK 4 5" solid-fueled rocketMK 3 5" solid-fueled rocketMK 50 solid-fueled rocket
WarheadMK 10 High explosiveMK 7 High explosiveMK 8 High explosiveMK 10 high-explosive

Main Sources

[1] Norman Friedman: "US Naval Weapons", Conway Maritime Press, 1983
[2] Norman J. Bowman: "The Handbook of Rockets and Guided Missiles", Perastadion Press, 1963
[3] Frederick I. Ordway III, Ronald C. Wakeford: "International Missile and Spacecraft Guide", McGraw-Hill, 1960
[4] J.D. Gerrard-Gough, Albert B. Christman: "The Grand Experiment at Inyokern", Naval History Division, 1978
[5] ORDATA Online Website

Back to Directory of U.S. Military Rockets and Missiles, Appendix 4

Last Updated: 5 February 2006