Editing SSPH Primus (section)

==Design==
{{More citations needed section|date=March 2024}}
[[Image:Primus 1.jpg|thumb|left|SSPH 1 on display at [[Marina South]] as part of Singapore's [[Singapore National Day Parade|National Day Parade]] celebrations in 2005]]
The chassis is based on the proven United States [[M109 Paladin|M109 155&nbsp;mm self-propelled howitzer]]. This has been upgraded in a number of key areas and has a new power pack similar to that fitted to ST Kinetics [[Bionix AFV|Bionix infantry fighting vehicle]] (IFV), which is already in SAF service. The use of common subsystems for the Primus and Bionix IFV offers several advantages, including easier training and reduced logistics.

The power pack of the Primus consists of a [[Detroit Diesel Corporation]] [[Series 92|6V 92TIA]] diesel engine developing 550 horsepower coupled to a [[General Dynamics]] Land Systems HMPT-500-3EC fully automatic transmission.<ref>{{Cite web|title=DSTA {{!}} Singapore Self-Propelled Howitzer 1 Primus|url=https://www.dsta.gov.sg/latest-news/in-the-news/dsta-in-the-news/singapore-self-propelled-howitzer-1-primus|access-date=7 December 2021|website=www.dsta.gov.sg}}</ref>

The maximum road speed of the Primus is {{Convert|50|km/h|mph}}, with an operating range of {{Convert|350|km|mi}}<nowiki>. Its combat weight of 28.3 tons allows it to use the SAF's military bridging systems. The relatively light combat weight also allowed the flexibility of being air-portable by an </nowiki>[[Airbus A400M]] Transport aircraft.<ref>{{Cite web |title=Primus 155mm 39 Calibre Self Propelled Howitzer - Army Technology |url=https://www.army-technology.com/projects/primus-155mm-39-calibre-self-propelled-howitzer/ |url-status=live |archive-url=https://web.archive.org/web/20231209055539/https://www.army-technology.com/projects/primus-155mm-39-calibre-self-propelled-howitzer/ |archive-date=9 December 2023 |access-date=7 December 2021 |website=Army Technology |language=en-GB}}</ref>

The turret is fitted with a locally developed 155&nbsp;mm 39-calibre barrel with a [[muzzle brake]] and fume extractor. This meets the NATO Joint Ballistics Memorandum of Understanding. The range of the Primus' gun depends on the type of projectile and charge combination used, and is about {{Convert|19|km|mi}} with the old [[M107 (projectile)|M107]] [[high explosive]] (HE) projectile and {{convert|30|km|mi|abbr=on}} with an extended range full bore base bleed projectile. In addition to smoke, HE and illumination projectiles, the locally developed 155&nbsp;mm cargo round can also be fired.

A semi-automatic loading system is provided to increase the rate of fire and reduce crew fatigue. The fused projectiles are loaded and rammed automatically; the modular charges are loaded manually. The Primus has a burst rate of fire of three rounds in 20 seconds and a maximum rate of fire of 6 rounds per min. The bustle mounted magazine holds up to 22 rounds of 155&nbsp;mm projectile.

The digital [[fire control system]] automates the complete projectile loading process and gun laying operation. An ammunition inventory management system keeps track of all onboard ammunition as well as ammunition expenditure during firing. The weapon is laid to the target using an automatic fire control system, which includes an onboard positioning and navigation system. This can receive target information from the battery or regimental command post. It takes less than 60 seconds to come into action and open fire and 40 seconds to be re-deployed.