Brazil – 1976
Tracked Self-Propelled Multiple Rocket Launcher – 1 prototype built
In 1973, Brazil began developing the X1 light tank, which was completed later that year. From there, the vehicle would spawn multiple variants, from bridge-laying vehicles to anti-aircraft vehicles. Another variant of the X1 combined the Brazilian research in rocket development, which had started in 1949, with the Brazilian advancements in the X1 project into a tracked self-propelled multiple rocket launcher vehicle, also known as the XLF-40. With this project, Avibras would gain a more prominent role within the defence industry and it would eventually lead to the renowned ASTROS 2 Artillery Saturation Rocket System.
Brazilian rocket development
In 1949, the Escola Técnica do Exército (ETE) (English: Army Technical School) initiated the Brazilian research of rockets, in line with developments from other major countries of the time. The first project was the 114 mm F-114-R/E rocket, which showed promising results. The F-108-R rocket system was then developed in 1956, which could fire multiple rockets and was mounted on a ¾ ton Willys Overland Jeep designated Fv-108-R.
In 1961, the company Avibras Aerospacial SA was founded in São José dos Campos (SP) by engineers of the Centro Técnico da Aeronáutica (CTA) (English: Aeronautical Technical Center). Avibras would develop Brazil’s first solid synthetic propellant, which would propel them into the rocket and missile industry.
The first major step for Avibras and the CTA was their participation in the Experimental Inter-American Meteorological Rocket Network project or EXAMETNET. This was a project led by the United States to acquire meteorological data for the entire American continent. The US started working together with countries like Argentina and Brazil by providing them with the Arcas rocket to carry out measurements at heights between 20 to 80 km. With Brazil’s participation in the project, the CTA acquired the technology and design of the Arcas rocket and went on to start developing the Sonda 1. The Sonda 1 was a two-stage rocket for which the general idea and technology were copied from the Arcas, but were redesigned for a larger rocket. Although the Sonda 1 itself would not be a success, its design proved fundamental.
In 1965, the CTA transferred the technology of the Sonda rocket to Avibras. With this transfer, Avibras effectively became the most important manufacturer of rockets and missiles in Brazil, as Avibras was responsible for the manufacture of the Sonda 1. After the Sonda 1 project, the CTA started developing the Sonda 2, which was again manufactured by Avibras in the late 1970s. From this point onward, Avibras would, together with the CTA, Instituto de Pesquisas e Desenvolvimento (IPD) (English: Research and Development Institute), and the new Instituto Militar de Engenharia (IME) (English: Military Institute of Engineering), renamed after a merger between the ETE and IMT in 1959, started developing ground-to-ground and air-to-ground rocket systems. One of these rockets was the X-40, which was developed in 1972.
The X-40 was a 300 mm rocket (rockets are unguided, missiles are guided) with a length of 4.45 meters (14.6 feet), weighing 550 kg (1,213 lb), of which a payload of 150 kg (331 lb), and a range of 65 km (40.4 miles). It used a solid propellant as fuel and was manufactured by Avibras. An interesting fact was that this was the first time the Brazilian engineers had used computers to make the calculations for rocket development.
With the development of the X1 family, the promising results of the X-40 rocket, and seeing this as a way to provide more firepower and mobility to the Brazilian artillery units, the IPD initiated the design of a tracked self-propelled multiple rocket launcher, which received the designation Carro de Combate Lançador de Foguetes X-40 (English: Combat Car X-40 Rocket Launcher).
The X1 project
The first X1 vehicle was developed and presented at the Brazilian Independence Day Parade on September 7th of 1971. The X1 was a modernization project of the M3 Stuart, carried out by the Parque Regional de Motomecanização da 2a Região Militar (PqRMM/2) (English: Regional Motomecanization Park of the 2nd Military Region), together with Bernardini and Biselli, two Brazilian private companies. The PqRMM/2 was responsible for the development of the wheeled vehicles, but also for the tracked vehicles of the Brazilian Army at the time, and was under the supervision of the Diretoria de Pesquisa e Ensino Técnico (DPET) (English: Army Research and Technical Educational Board), which coordinated the projects.
The tracked vehicles were researched and developed by a team of engineers within the Army and PqRMM/2, which were part of the Centro de Pesquisa e Desenvolvimento de Blindados (CPDB) (English: Centre for the Research and Development of Tanks). The CPDB was a study group of Army engineers which analyzed the possibilities of producing tanks domestically. The first goal was to develop a new family of light tanks using the M3 Stuart as its basis. One of the vehicles which would form part of what we now know as the X1 family, was the XLF-40.
With the success of the X1 project and the completion of the X-40 rocket, the Brazilian Army decided to initiate the development of a rocket system for the X1. The IPD made the first sketches of the Carro de Combate Lançador de Foguetes X-40 (English: Combat Car X-40 Rocket Launcher), which were presented on July 20th, 1976. Further design and construction were immediately initiated in an attempt to build the new vehicle before September 7th of the same year, so it could make an appearance on the yearly Independence Day parade, together with the X1A1 and the XLP-10.
The XLF-40 would receive three different designations during its development, with its proposal calling it Carro de Combate Lançador de Foguetes X-40, which would be simplified to Carro Lançador Múltiplo de Foguetes (Multiple Rocket Launcher Vehicle). Finally, it received the designation XLF-40. The X referred to it being a prototype, the L to Lançador (English: Launcher), the F to Foguetes (English: Rockets), and the 40 to the X-40 rockets used. Eventually, the full name would be Viatura Blindada Especial, Lancador de Foguetes, XLF-40 (VBE LF XLF-40) (English: Special Armored Vehicle, Rocket Launcher, XLF-40).
The development of the XLF-40 would be carried out by multiple companies, of which Avibras, Bernardini, and Biselli were the most important. Bernardini and Biselli were responsible for the conversion of the hull and installation of the suspension, while Avibras manufactured the rockets.
One of the requirements was that all the systems were completely operable from within the vehicle. The aiming and the launching of the rockets were controlled through radio systems. The rockets could be fired independently or in a volley. To provide a better surface to fire from, the XLF-40 had four outriggers, two on each side, which were operated by hydraulic pistons on each leveling system. These outriggers made the XLF-40 a more stable platform to fire from, increasing its accuracy. Another interesting development was the installation of the TRANSIT global positioning system to better locate the vehicle. This GPS system would help the crews to better estimate the firing arcs of their rockets and be more accurate. An M3A1 Stuart hull was selected to be converted to the XLF-40.
The XLF-40 would only be armed with its rockets and personal weapons for the crew, as the machine gun for the co-driver from the M3 Stuart was removed to provide the same dual hatch as for the driver. This meant that the co-driver had a larger space to enter or exit the vehicle. This style of hatches was first used on the X1 prototype vehicle, but would only be carried out on the XLF-40 and the XLP-10 vehicles. The construction of the XLF-40 prototype was completed in less than 2 months and was able to be presented during the September 7th, 1976 Independence Day Parade.
XLF-40 hull origin theory
In the X1 article, the writer proposed a theory to what may have happened with the X1 prototype after it was completed. This theory suggests that the hull might have been repurposed. Besides the X1, a bridge-laying vehicle designated XLP-10 and a rocket launching vehicle designated XLF-40 were built. Both these variants would use the two hatch opening for the co-driver instead of a hull machine gun. What is interesting is that the XLP-10’s and all production X1’s used a single front side plate and the XLP-10’s missed a characteristic hook on these plates. The XLF-40, though, used the exact same double front side plates design as the X1 prototype and also offered the hook. Additionally, both the X1 prototype and the XLF-40 were converted from an M3A1 Stuart, identifiable from the rear. Considering the X1 prototype was trialled in 1974 and the XLF-40 was built in 1976, it is very likely that the Brazilians removed the turret at some point to subsequently repurpose the X1 prototype hull for the XLF-40 prototype. This makes perfect sense to not waste an otherwise perfectly fine hull, and to reduce the costs of making a prototype.
With these arguments, the writer hopes to have sufficiently proved his theory that the X1 prototype hull was repurposed for the XLF-40, but would like to reiterate that this is just a theory and only indirect evidence and photographs point towards this possibility. No direct evidence has been found to verify this theory.
XLF-40 in Detail
The XLF-40 weighed 16.6 tonnes combat-loaded (18.3 US tons) and 15 tonnes (16.5 US tons) without rockets. It was 5.98 meters (19.6 feet) long, 2.74 meters (9 feet) wide, and 2.54 meters (8.3 feet) tall. It had a crew of three, with the driver located on the front left of the hull, the co-driver on the front right of the hull, and the commander probably positioned somewhere under where the turret originally was positioned, although there is no confirmation of this.
Hull and Armor
The hull of the XLF-40 was a slightly lengthened and modified M3A1 Stuart hull. As such, the overall protection for the XLF-40 hull remained the same as that of the M3. The thickness of the plates which were used to lengthen the hull is unknown. The upper front plate of the XLF-40 had an armor thickness of 38 mm (1.5 inch) at 17 degrees vertical, a middle front plate of 16 mm (0.6 inch) at 69 degrees, and a lower front plate of 44 mm (1.7 inch) at 23 degrees. Its sides were most likely about 25 mm (1 inch) thick. The rear armor and the lengthened parts of the side are unknown. Considering the original Stuart had 25 mm (1 inch) thickness on the sides and rear, it would not be unreasonable to assume that the lengthened structure was about 25 mm (1 inch) thick as well. The top plate would have been 13 mm (0.5 inch) thick and the floor plate would have gradually decreased in thickness from 13 mm at the front to 10 mm (0.5 to 0.4 inch) in the rear (although the thickness for the lengthened structure is unknown).
The rest of the XLF-40 had a very similar layout as the Stuart. It had two headlights, one on each side of the front mudguards, two towing hooks on the front hull, two driver style double hatches and, as a result, no hull machine gun.
The XLF-40 had two hydraulic pistons on the front hull, one on each side. These pistons were fixed on a pivot, which allowed them to turn facing the ground when the pistons were utilized. The feet on which the XLF-40 was stabilized had a rotating bar attached to them and to the hull, which caused the pistons to face the ground as the rod of the piston made a complete stroke.
The rear curved plate was altered to make room for the rear hydraulic cylinders. The hydraulic cylinder was mounted to the rear by cutting a hole in the curved M3A1 rear plate and sticking the cylinder through it. All the hydraulics of the XLF-40 were powered by the original M3A1 Stuart hydraulic system.
The XLF-40 was powered by a Scania-Vabis DS-11 A05 CC1 6-cylinder in-line diesel engine. This engine produced 256 hp at 2,200 rpm, giving the vehicle a horsepower per tonne ratio of 15.4. It used the same, but revised and locally produced, 5 forward and 1 reverse gearbox, transmission, and differential as the original Stuarts. The XLF-40 would have a top speed of about 55 km/h (34 mph) on roads, but would most likely be much lower when it was armed with the X-40 rockets. The vehicle had an operational range of 520 kilometers (323 miles).
The XLF-40 used a copied and slightly altered VVS suspension system from the 18-ton M4 artillery tractor. It had 4 road wheels divided over two bogies, with 2 bogies per track, two return rollers on each side, a drive sprocket in the front, and an idler wheel on the rear. The 18-ton M4 suspension gave the vehicle a ground pressure of around 0.59 kg/cm2 (8.4 psi). It had an on-ground track length of about 3.22 meters (10.6 feet) and could cross a trench of 1.2 meters (3.9 feet).
Turret and Armament
The turret was replaced by a single plate on which the rocket frame and the needed hydraulics were mounted. This single round plate used the same 1.6 meters (5.25 feet) turret ring diameter as the rest of the X1 family. On the rear of the plate were two hatches for the crew, located in between the rocket rails.
A frame was built on top of the plate, on which the hydraulic cylinders were located. The rods of these cylinders were fixed to the launching platform so that the rockets could be fired at the needed angle. The launching platform would rest on the frame during travel. Over the years, there seems to have been some development regarding the location of the hydraulic cylinders for the launching platform. The cylinders seem to have been placed much more forward from the launching platform in the early development stages. In later stages, the cylinders seem to have been placed much closer to the hinge point of the launching platform, potentially enabling the rockets to be fired from much steeper angles.
Resting on top of the frame was the launching platform, from which the rockets would be aimed and fired. The frame seems to have been constructed from heavily perforated steel profiles. The holes in the frame were probably meant to save weight, so that smaller hydraulics could be used. The launching platform was 5.5 meters (18 feet) long and between 1.8 to 2.4 meters (5.9 to 7.9 feet) wide. It had three rails from which a rocket could be fired. Each rail had two clamps attached to them in order to clamp the rocket to the rails during travel.
Initially, the mounting point of the hydraulic cylinder was located in the middle of the launching rails but later seems to have been repositioned towards the rear of the platform due to the relocation of the hydraulic cylinder. The hydraulic cylinders enabled the launching platform to be angled and give the rockets the trajectory to hit their target. The rockets were fired perpendicular from the hull. This was done to provide the launching platform with the needed space to angle the rockets, which is seen to be done at a near 90-degree angle with the rockets aiming almost straight up the sky.
The XLF-40 was armed with 3 X-40 rockets. These rockets had a range of 65 km and used solid propellant as their fuel. The rockets were about 4.45 meters (14.6 feet) long and had a diameter of 300 mm. The rockets weighed 550 kg (1213 lb) each with a 150 kg (331 lb) payload. The rockets could be fired both simultaneously and independently from each other. The XLF-40 had no further armament.
After the XLF-40 was presented in the Independence Day Parade in 1976, Brazilians would continue testing and improving the vehicle until the early 1980s. It would be tested at the Marambaia Proving Ground in Rio de Janeiro, where it would fire its rockets towards the sea.
The XLF-40 would mostly end up as a testbed more than anything else. It would have a few issues, some of them with the launching platform, but these were said to never have been fully resolved. These issues were part of the reason why the project would not be progressed upon further. In 1981, with the knowledge acquired from the XLF-40 project, Avibras developed the ASTROS 1 rocket system for Iraq, which would eventually lead to the successful ASTROS 2 rocket system that is operated by the Brazilian Army, among others. The development of the ASTROS rocket systems probably contributed to the eventual cancellation of the XLF-40 as well.
With the cancellation, the XLF-40 was added to the Conde Linhares Military Museum collection in Rio de Janeiro at an unknown date.
In the end, the XLF-40 can be described as a testbed for rocket systems for which potential military service would have been a bonus. It incorporated some relatively advanced technologies, such as the TRANSIT GPS, which would go on to enable Avibras to develop a much more advanced rocket system. The Brazilian Army did not seem initially convinced by the potential of rocket systems after the XLF-40. It would take Brazil until the 1990s to buy the ASTROS system, 10 years after its first conception. This might also have been because the need and money were not there for the expensive system.
The XLF-40 was fundamental for Avibras as a company, and paved the way for the successful ASTROS rocket systems, which were sold by Avibras to countries such as Saudi Arabia, Iraq, Brazil and Indonesia, among others. The ASTROS would become one of Brazil’s most successful and lucrative weapon systems, still being ordered to this day.
|Dimensions (L-W-H)||5.98 (19.68 feet) x 2.74 (9 feet) x 2.54 meters (8.33 feet)|
|Total weight||16.65 tonnes (18.35 US tons)|
|Crew||3 (Driver, Co-driver, Commander)|
|Propulsion||Scania-Vabis DS-11 A05 CC1 6-cylinder in-line 256 hp diesel engine|
|Speed (road)||55 kph (34 mph)|
|Operational range||520 km (323 miles)|
|Armament||3 X-40 Rockets|
Front (Upper Glacis) 38 mm (1.5 inch) at 17 degrees
25 mm (1 inch) allround
Special thanks to Expedito Carlos Stephani Bastos, the leading expert of Brazilian armored vehicles https://ecsbdefesa.com.br/, Jose Antonio Valls, an Ex-Engesa employee and expert in Engesa vehicles, Paulo Bastos, another leading expert of Brazilian Armored vehicles and the author of the book on Brazilian Stuarts, and Guilherme Travassus Silva, a Brazilian with whom I was able to endlessly discuss Brazilian Vehicles and who was always willing to listen to my near-endless ability to talk about them.
Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives – Hélio Higuchi, Paulo Roberto Bastos Jr., Reginaldo Bacchi
Blindados no Brasil – Expedito Carlos Stephani Bastos
Lançador de Foguetes XLF-40 – A Artilharia Sobre Lagartas – Expedito Carlos Stephani Bastos
Uma realidade brasileira: Foguetes e mísseis no Exército Brasileiro 1949-2012 – Expedito Carlos Stephani Bastos
Personal correspondence with Expedito Carlos Stephani Bastos
Personal correspondence with Paulo Roberto Bastos Jr.
TM 9-785 18-Ton High Speed Tractors M4, M4A1, M4C, and M4A1C – US Army April 1952.
Stuart: A history of the American Light Tank, Volume 1 – R.P. Hunnicutt