SSPH-1 Primus

The Singapore Self-Propelled Howitzer 1 (SSPH 1) Primus is a tracked 155 mm self-propelled howitzer developed jointly by the Singapore Armed Forces (SAF), the Defence Science and Technology Agency (DSTA) and Singapore Technologies Kinetics (ST Kinetics). Its name derives from the Singapore Artillery motto In Oriente Primus ("First in the East").

The requirement emerged in the early 1990s from the need to provide fire support able to keep pace with the armour brigades of the Combined Arms Divisions. A market survey conducted in 1995 and 1996 examined the American M109 Paladin, the British AS90 Braveheart, the Japanese Type 75 and the Russian 2S3M1, and concluded that all were either too heavy or too wide for Singaporean terrain. Drawing on its experience with the FH-88 and FH-2000 towed guns, ST Kinetics began development with DSTA in 1996. The first working prototype was rolled out in April 2000, built on a chassis adapted from the United Defense Universal Combat Vehicle Platform (UCVP), which incorporates components from the M109, the M2 Bradley and the M8 Armored Gun System. Two years of trials followed. The Primus was certified as meeting SAF requirements in September 2002 and was formally inducted into the Singapore Artillery in 2004.

The chassis derives from that of the M109 and was reworked around a power pack common with the ST Kinetics Bionix infantry fighting vehicle, comprising a Detroit Diesel 6V 92TIA engine and a General Dynamics Land Systems HMPT-500-3EC automatic transmission. The commonality with the Bionix simplifies crew training and logistics. Combat weight permits the use of SAF military bridging and allows air transport by the Airbus A400M.

The turret mounts a locally developed 155 mm 39-calibre barrel with muzzle brake and fume extractor, conforming to the NATO Joint Ballistics Memorandum of Understanding. Range varies with projectile and charge, from about 19 km with the standard high-explosive shell to 30 km with an extended-range full-bore base-bleed projectile. Smoke, illumination and a locally developed 155 mm cargo round can also be fired. A semi-automatic loading system loads and rams fused projectiles, while modular charges are loaded by hand; the bustle magazine holds 22 projectiles. Burst rate of fire is three rounds in 20 seconds, with a sustained maximum of six rounds per minute. A digital fire control system automates loading and gun laying, incorporates an onboard positioning and navigation system, and receives target data from battery or regimental command posts. An ammunition inventory management system tracks onboard stocks and expenditure. The gun can come into action in under 60 seconds and displace in 40 seconds.

The Primus equips the 21st Battalion, Singapore Artillery. Because land in Singapore is limited, live firing is conducted abroad: initial trials took place at Waiouru Army Camp in New Zealand during Exercise Thunder Warrior in February 2004, and the guns have also deployed to the Shoalwater Bay Training Area in Queensland for Exercise Wallaby. On 19 January 2019 a national serviceman was killed when crushed by the gun barrel of a Primus during maintenance work at a training exercise in New Zealand.