Projector, Rocket 3-inch, No. 8, Mk. I

Projector, Rocket 3-inch, No. 8 Mk. I
Production Information
Type	Rocket Launcher
Technical Information
Total length	1.77 m
Weight	1,120 kg
Caliber	3" Rockets (76.2 mm)
Magazine capacity	16 or 30 rockets
Muzzle velocity	353.5 m/s
Crew	3
Usage
Year introduced	1944
Used by	Great Britain Canada
[Source]

The Projector, Rocket 3-inch, No. 8 Mk. I "Land Mattress" was a rocket launching system used by Great Britain during World War II.

Description

The Land Mattress' name came from its naval counterpart, the Sea Mattress, a similar system used for bombarding beaches prior to landing. Notably, the Land Mattress design used components from various sources. For example, the rocket motor from the RP-3 Aircraft Rocket, the 3 kilogram warhead from the naval Sea Mattress, and discarded fuses deemed unsafe by the British Royal Army. By using the RP-3's aircraft rocket motor and rifling the rocket tubes, the Land Mattress' rockets were given a degree of spin, thus increasing accuracy and maximum range. The muzzle velocity of these rockets was about 353.5 meters per second, with the system taking about seven seconds to completely empty its racks of rockets.

The Land Mattress weighed about 1,120 kilograms with a total length of 1.77 m. It featured either 16 or 30 rocket tubes, with each rocket taking an estimated 10 minutes to reload and rewire to the built-in electrical ignition system. Perhaps the most restricting feature of the system was its elevation which was restricted from +23˚ to +45˚, giving the piece a good maximum range of 7,225 meters, but also a minimum range of 6,125 meters. To correct for the minimum range, rotary spoilers were added to the exhausts of the rockets so as restrict the flow of exhaust by varying amounts, giving the Land Mattress an absolute minimum range of 3,565 meters, something that was far more practical.

History

Development

One of the twelve prototype Land Mattresses being reloaded after supporting the 1st Polish Armored Division near Breda. It is possible to tell it is a prototype because of its 4 x 8 organization of rocket tubes instead of the standard 5 x 6.

The Land Mattress was designed and prototyped in 1944 by Canadian artillery officer Lieutenant Colonel Eric Harris working with Lieutenant Colonel Michael Wardell. Their combined development of the Land Mattress followed requirements set forth by the First Canadian Army. Even with the support for development, many components and assets of the Land Mattress project had to be scavenged wherever available, including taking existing anti-aircraft crew and retraining them to use the Land Mattress and prepare its rockets. The first ten prototypes were completed at the Meyer-Dunford Bottling plant and arrived in France for testing on September 30, 1944. These prototypes each had 32 rocket tubes instead of the eventual 30. Testing was completed in December of 1944 with the original ten plus two new prototypes being assigned to the 1st Rocket Battery.

Combat Service

The first combat trial involving the Land Mattress occurred on October 31, 1944 with good success. Again in the Netherlands, the second trial took place in November, in which the Canadian rocket battery supported the 1st Polish Armored Divisions attack against German positions in Breda. With both trials declared successful, the Land Mattress was shifted to fully operational status and entered full production, with two further rocket batteries ordered. Land Mattresses proceeded to aid Allied troops in such battles as during the crossing of the river Scheldt in which 1,146 rockets were fired in only six hours. In all, some 400 Land Mattresses were produced during World War II.