The Hefesto project began in 2022 with the idea of building a rocket without any 3D-printed parts or bolted joints, unlike what we used to do in the LEEMUR and FORTVNA projects. The goal was to make it as inexpensive as possible, with minimal electronics, and constructed entirely from fiberglass.
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During the launch on December 23, 2022, the Hefesto v1 was launched. It was a very small rocket that laid the groundwork for the later development of Hefesto v2. It was powered by a Julian motor, and due to a flaw in the stability design upon exiting the launch rail, the rocket became unstable and impacted the ground just a few meters from the rail. Nevertheless, the manufacturing of the motor mount using fiberglass and cork, as well as the construction of the fins and fin can with fiberglass, set the foundation for Hefesto v2.
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Hefesto v2 was launched on May 13, 2023. It was a rocket very similar to LEEMUR, but with significantly fewer 3D-printed parts, greatly reducing its weight, and with no bolted joints. The nose cone, along with a few other components, continued to be made from 3D-printed PLA, as no viable alternative could be found for producing them in fiberglass or other materials within the available time and resources. This launch was a resounding success: Hefesto v2, powered by a Julian motor, reached an altitude of 950 meters, marking our highest apogee to date. The rocket's separation and recovery were also flawless, representing one of the greatest successes in LEEM's recent history.
Inspired by the Roman mythology goddess Fortuna, the Fortvna rocket is a prototype of a CanSat Launcher that began development at LEEM in 2022, with Gabriel Arenas as the project leader. The design initially included space to launch 12 CanSats to an apogee of 1 km, although it was later updated to accommodate 9 CanSats. The rocket had a height of 202 cm in version 1, and 177 cm in version 2, both with a diameter of 181 mm, and it used an SRAD Conde Julian motor for propulsion.
The first launch of this rocket took place on December 23, 2022, resulting in a partial success, as the Conde Julian motor experienced some performance issues, preventing the rocket from achieving stable flight. The weights simulating the CanSats were successfully deployed, but the mechanical separation system did not operate optimally.
The second launch was carried out on May 13, 2023, resulting in an explosion on the launch rail due to an unexpected failure in the Conde Julian motor. This version of the Fortvna, named Fortvna 2.0, featured improvements to the separation system and aerodynamics to achieve better stability upon exiting the launch rail, although these improvements could not be tested.
The Fortvna project continued as a learning project for the new team members during the following academic year (2023–2024). Two teams, Frigg and Freya, were formed, each tasked with building their own rocket and competing to see which would achieve better results. Ultimately, these rockets were intended to be launched in a campaign that never took place, as the program was canceled before it could conclude. The program was canceled due to organizational issues, a lack of team resources, and the infeasibility of conducting a launch that year.
Nevertheless, despite its cancellation, the Frigg and Freya teams' program is considered a success, as it served as fundamental training for the new members of the association.
The URSA project is the rocket presented by LEEM for the EuRoC24 competition. It is the largest rocket ever built by the LEEM team and represents the greatest technological challenge the team has faced to date. With this rocket, the aim was to compete in the 3 km solid motor category, and in this case the motor was SRAD (Student Researched And Developed).
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SIZE
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URSA had dimensions of 3 m in height and 158 mm in diameter.
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MOTOR
The motor designed for this mission was the SM12, which uses Rocket Candy as propellant and is the most powerful solid SRAD motor in Spain to date.
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DEPLOY SYSTEM
The rocket carried two parachutes: a drogue chute and a main chute, along with a separation system based on the release of compressed air.
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PAYLOADS
The payloads carried by URSA were created by CREA, a robotics and electronics association at ETSIDI (UPM).
One of them was a microgravity fluid experiment, which could not be flown due to leakage issues, and the other was a real-time video transmission system.
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​After many reviews by EuRoC officials, URSA rocket was finally cleared for launch on the last day of the competition, October 14. The ignition of the SM12 motor was nominal, as was URSA’s initial ascent. However, after only a few seconds of flight, and at an unknown altitude (since no telemetry data was obtained), the rocket disintegrated in flight.
After analyzing the few remains of URSA that we were able to recover, it was determined that the issue was a premature activation of the COâ‚‚ separation system by the electronics. This system should have been triggered when the rocket was close to apogee, at which point its velocity would have been much lower and therefore the dynamic pressure acting on it much smaller. Since it was triggered prematurely, the external dynamic pressure prevented the separation system from working properly. As a result, the pressure generated inside by the activated COâ‚‚ cartridge had no way to escape, ultimately causing the rocket to explode.
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URSA is, so far, the largest mission ever carried out by LEEM in its history, and it has laid the groundwork for many future missions and subsequent participations in EuRoC and other competitions.
The LEEMUR rocket series began development in 2021, being the first rockets developed at LEEM during the team’s new stage, which started in 2020. The main goal of the LEEMUR rocket series is to serve as technology demonstrators, allowing the team to test manufacturing processes and new systems developed in the workshop. The person who led most of the design work for the entire LEEMUR series was the head of the design department, Víctor Santurino Salmerón.
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​The design of the LEEMUR series evolved with the development of the different rockets that composed it, but most LEEMUR rockets shared the following characteristics:
Apogee
LEEMUR series rockets have a theoretical apogee of 1000 m
Payload
Able to carry 1kg of payload allowing it to be perfect for testing subsystems
Deploy system
This rocket has a mechanical separation system that allows it to be reusable
Propulsion
LEEMUR rockets are powered by LEEM-Made JULIAN motor
Size
Height: 1.6 m, Diameter: 7.5 cm
Other Characteristics
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LEEM-Made parachute
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LEEM-Made electronics LIAS I or LIAS II
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Phenolic cardboard fuselage in the first versions, later fiberglass. The progress in fiberglass fuselage manufacturing was largely thanks to the work of design department members Juan Martínez Vázquez and Rafael Gamero Redondo.
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Motor mount, electronics bay, nose cone, and other structural parts manufactured with 3D-printed PLA​
These features made the LEEMUR an extremely versatile rocket for testing a wide variety of subsystems, as well as an extremely cheap and quick one to manufacture. 3D printing played an important role throughout the entire development of the LEEMUR series, and the low cost of Julian motors allowed for many launches of these rockets: 12 launches in total, with 11 rockets built, since 2 of them were relaunched, although one was never launched (LEEMUR 3).
The first launch of a LEEMUR rocket took place on February 18, 2022. LEEMUR 1 was different from the rockets that followed: it had a phenolic cardboard fuselage, electronics without telemetry that stored data on an SD card, and was powered by a commercial category I motor. The separation system worked with the pyrotechnic charge installed in the commercial motor. The ascent of the flight was nominal; however, the separation did not occur, so the rocket crashed, although the data from the SD card was recovered from the wreckage. This flight was very important for the development of the association, as it allowed us to obtain data and move forward with new manufacturing methods and the implementation of new systems.
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Video of the LEEMUR 1 launch: https://www.youtube.com/watch?v=7dlZnL3O6ME&pp=0gcJCYQJAYcqIYzv
On July 19, 2022, six rockets from the LEEMUR series were brought to launch. These rockets were LEEMUR 2, 3, 4, 5, 6, and 7. Some of these rockets were powered by commercial motors, and others by Julian motors. LEEMUR 3 was ultimately not launched that day, leaving the following launch outcomes:
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LEEMUR 2: Partial success. Instabilities during guide rail exit due to ignition issues caused the trajectory to deviate significantly.
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LEEMUR 4: Failure. The rocket became highly unstable due to propulsion problems and ascended only a few meters before flipping over and crashing into the ground.
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LEEMUR 5: Success. Nominal trajectory and recovery.
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LEEMUR 6: Success. Nominal trajectory and recovery.
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LEEMUR 7: Success. Nominal trajectory and recovery. Successfully tested telemetry electronics developed by Carlos Serradilla Gil. An attempt was made to relaunch it given its good condition, but the attempt was eventually aborted.
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​For more information about the launches that day, watch the recap video of the live stream: https://www.youtube.com/watch?v=CmGN73k-r3A&t=1347s
The next launch took place on December 23, 2022. Four LEEMUR rockets were taken to the launch: LEEMUR 1.1E TF, LEEMUR 1.2ESA TF, LEEMUR 1.3AS TF, and LEEMUR 1.4S TF. Due to the unstable performance of the Julian motors that day, caused by last-minute modifications, only the first launch, that of LEEMUR 1.1E TF, was successful. The remaining rockets experienced unstable trajectories that caused the missions to fail.
Launch video 23/12/2022: https://www.youtube.com/watch?v=38NiaMIX_D0&t=1760s
The last LEEMUR rocket launch to date took place on May 13, 2023. Two LEEMUR rockets were brought to the launch, named simply LEEMUR “Telemetry” (its purpose being to test the LIAS II telemetry board) and LEEMUR “Drogue-Chute” (its purpose being to test a drogue parachute deployment system). These rockets were refurbished after being recovered from the previous launch. Both rockets achieved partial success: in the case of LEEMUR “Telemetry” due to a non-nominal trajectory despite good results with the electronics, and in the case of LEEMUR “Drogue-Chute” due to a non-nominal trajectory and the simultaneous deployment of both parachutes.
Launch video 13/05/2023: https://www.youtube.com/watch?v=pftNdJBzKy0&t=596s
The major advantages of the LEEMUR series (low cost, easy manufacturing, modularity, and high reliability) made it possible to test countless subsystems, ensuring that all technologies developed at LEEM were flight-tested. These rockets, together with the LEEM-Made philosophy, would define the identity of the team in this new stage of its history.
The SM12 “Aethon” is the largest student-developed solid rocket motor in Spain. Its design was led by Álvaro Albaladejo, former Propulsion Team Leader. It features four 1 kg grains of Rocket Candy propellant. The motor has a diameter of 104 mm, a length of 853 mm, and is made entirely of steel. The SM12 motor was designed specifically to power a rocket of URSA’s size and weight to 3 km altitude, in accordance with the requirements of the EuRoC competition.
Its development involved tackling new challenges, such as cooking and molding much larger propellant grains, which made demolding and subsequent assembly into the motor significantly more difficult. Thermal protections also had to be added to certain parts of the motor, since the burn time was much longer than in previous motors. These thermal protections included cork ablatives manufactured by the propulsion team, as well as the use of RTV silicones, fiberglass inhibitors, and spacers.
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A total of two full static tests of the motor were carried out, and it was used once in flight, powering the URSA rocket at the EuRoC24 competition on October 14, 2024. The tests of this motor were conducted while monitoring as many variables as possible: thrust was measured with a load cell, chamber pressure with our in-house chamber pressure measurement system, and temperatures at various points of the motor with thermocouples continuously throughout the test.
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Thanks to all this collected data, the SM12 Aethon has become the most reliable motor developed by LEEM, and it now serves as the foundation for future Rocket Candy-based motors, improving and optimizing several aspects of this design.
Static test video of the SM12 Aethon motor: https://www.youtube.com/watch?v=iQndP1tIEH8
The Julian motor series was the first series of solid motors developed by LEEM, with development beginning in 2021. The design was led by Nicolás de Jong and Germán Pérez, and the manufacturing of the propellant and nozzles was carried out entirely by members of the propulsion department.
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The Julian motor is capable of reaching 600 Ns of total impulse, measuring 373 mm in length and 38 mm in diameter, with a maximum nominal chamber pressure of 40 bar. The motor incorporated four grains of solid Rocket Candy propellant. Its casing was made of aluminum and its nozzle of stainless steel, not the optimal materials for this type of rocket motor, but the best in terms of material cost and ease of manufacturing.
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It is the most frequently ignited motor by the association to date, with over 20 ignitions between tests and launches. The Julian motor was responsible for powering the vast majority of the LEEMUR series, as well as the Hefesto v1 and Hefesto v2 rockets.
After many tests, firings, and design iterations, the latest versions of the Julian motor became one of the cheapest and most reliable motors that can be used to propel a sounding rocket to altitudes below 1000 meters.
The Conde Julian motor is the evolution of the Julian motor. It is larger, wider, and uses five grains of Rocket Candy instead of four, with each grain being bigger than in the previous version. The design of this motor was led by Nicolás de Jong, Germán Pérez, and Sara Santos, and, as with its predecessor, almost all of its parts were manufactured by members of the propulsion department.
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Due to its configuration, the motor reached chamber pressures of over 100 bar, which added an additional structural challenge not present in the Julian motor. This configuration was necessary given the manufacturing limitations of the tools available at the time. For example, the stainless-steel nozzle had to be manufactured on a manual lathe in the team’s workshop, which, due to its small size, limited the maximum diameter that could be produced. This resulted in a motor with dimensions of 60 mm in diameter and 589 mm in length.
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The Conde Julian motor was responsible for powering the Fortvna rockets, the “CanSat Launcher” project that began development at LEEM in 2022. In both launches, the motor behaved in undesired ways, despite having achieved successful static tests beforehand. In the first Fortvna launch, the motor failed to achieve nominal ignition, which meant it did not provide the necessary thrust for the rocket to reach stability upon exiting the launch rail. In the second Fortvna launch, the motor exploded after ignition, even though it had successfully passed a static test earlier that same day.
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The challenges arising from the development of this motor brought the project to a critical point. Additional tests were carried out later with a new test stand and a chamber pressure measurement system, which provided information showing that the motor sometimes failed to withstand pressures above 90 bar with the structural configuration used at the time. Fernando Silva Cuenca, a member of the propulsion department, developed a new structural design for the Conde Julian motor, greatly increasing its reliability. Despite these improvements, the Conde Julian suffered another failed test due to irregular combustion that caused overpressure.
Because of all the ignition irregularities presented by this motor, and since the Fortvna project was indefinitely frozen, the development of the Conde Julian motor was also halted, as resources were redirected to the development of the new motor that would power our EuRoC24 rocket: the SM12 – “Aethon.”
In this project, we aim to develop the association’s first liquid rocket engine, a pioneering milestone that, if successfully completed, would also become the first student-built liquid engine in Spain.
The chosen design is a pressure-fed system using nitrous oxide as the oxidizer and ethanol as the fuel, operating at a chamber pressure of approximately 30 bar.
The ultimate goal is to integrate this engine into a rocket and carry out a launch. To achieve this, the project will follow a progressive approach: first, a scaled-down demonstrator will be developed, serving both as a technological testbed and as a learning platform for liquid propulsion design, integration, and testing. This initial version will be used for static fire tests on a bench, while the final version will undergo testing and will ultimately fly on board an experimental rocket.
Through this project, the association not only seeks a significant technical breakthrough but also aims to lay the foundation for future developments in experimental rocketry. Achieving this goal would mark a historic milestone: the very first student liquid rocket engine ever developed in Spain.