Trials of the HERCCULES stratospheric experiment begin

Trials of the HERCCULES stratospheric experiment begin

2023-05-22 10:15:39

HERCCULES, intended to study convective heat transfer in the stratosphere, will be launched by stratospheric balloon in September.

The HERCCULES (Heat-transfer and Environment Radiative and Convective Characterization in a University Laboratory for Experimentation in the Stratosphere) experiment was conceived and developed by a multidisciplinary team of students from the Polytechnic University of Madrid (UPM) in Spain. At the end of 2021, he was selected by the European Space Agency (ESA) to participate in its BEXUS program.

The REXUS/BEXUS programmes, under a bilateral agreement between the German Aerospace Center (DLR) and the Swedish National Space Agency (SNSA) and through a collaboration with ESA, allow students from universities and colleges across Europe to carry out scientific and technological experiments following all phases of development of a space project: design, construction, tests and flight.

HERCCULES studies convective heat transfer in the stratosphere, with the aim of improving the thermal modeling phase of this type of experiment to reduce the uncertainty associated with heat transfer and the thermal environment and at the same time optimize current designs.

It consists of four main elements: the Heat Transfer Lab, an experiment to assess convective heat transfer in the stratosphere; the Environmental Lab, which will characterize the thermal environment during the flight; the Attitude Lab, which consists of a series of sensors to measure the orientation of the nacelle, and an experimental nadir sensor for stratospheric balloons.

Part of the hardware used in HERCCULES. (Photo: UPM)

Ready for launch

HERCCULES, which has already been integrated, is currently immersed in the testing phase. The purpose of this phase is to analyze and verify the behavior of the different systems in conditions very similar to those that the experiment will face during the flight.

On the one hand, it is necessary to check the compatibility between the ground station and the on-board software, studying the telemetry, as well as verifying that the telecommands sent allow for proper control of the experiment.

On the other hand, “due to the loads that can appear during the launch and landing of the nacelle, it is necessary to verify that the structure that protrudes from it and that supports the radiation sensors will resist the loads during the flight,” explains Blanca. Boado, PhD student in charge of structural design. This will be corroborated by a vibration test at the facilities of the Ignacio Da Riva Microgravity University Institute on the Montegancedo campus.

Finally, the experiment has to be tested under the thermal conditions that will occur during the flight. These are mainly characterized by a pressure drop during the ascent up to 600 Pa, which changes the way in which heat is transmitted and temperatures of up to 50 degrees Celsius below zero at the tropopause. Once the cruising altitude is reached (about 35 kilometres), the low air density means that heat dissipation to the environment occurs mainly by radiation. However, in internal areas, convection can still have a significant weight (this is precisely what the Heat Transfer Lab intends to measure). For this, the experiment will be analyzed inside a thermal vacuum chamber, in the Thermodynamics laboratory of the Higher Technical School of Aeronautical and Space Engineering (ETSIAE).

The data acquired during the tests will be used later to correct the numerical thermal models developed by computer. Carlos Arroyo, student of the Master’s Degree in Space Systems (MUSE) is in charge of carrying out these essays as part of his master’s final project.

HERCCULES has to be completely ready by June 30, the day that the person in charge of the integration of the BEXUS32 flight will go to the ETSIAE of the UPM for the final review.

Multidisciplinary by necessity

This experiment manages to unite several of the disciplines involved in the development of space systems. Behind HERCCULES there is a multidisciplinary team of students from various UPM centers, led by David González Bárcena, assistant professor in the Fluid Mechanics and Aerospace Propulsion Department of the Higher Technical School of Aeronautical and Space Engineering (ETSIAE) who, when The project started when I was a doctoral student at this same School.

Juan Manuel Redondo and Pedro Barba, guided by the professor of the Higher Technical School of Engineering and Telecommunications Systems (ETSIST) Javier Malo, have been in charge of the complete design of the electronics. From the same School, Álvaro Morán and Javier Garrido have developed the ground station from which data will be received and sent during the flight.

The design of the on-board software has been developed by Ángel Pérez, currently a doctoral student at the Higher Technical School of Computer Engineering (ETSIINF) and member of the STRAST research group of the UPM, under the direction of Professor Juan Zamorano.

The rest of the necessary subsystems, as well as the integration of the experiment, have been developed by ETSIAE students, mostly MUSE students or alumni. Ángel Porras, Juan Bermejo, José Miguel Álvarez, Daniel Corcuera and Sergio Marín participate as doctoral students. Marina Merchán, Siro Muela, Noelia Martínez, Adrián Peña, Alba Benito, Carlos Gómez and Pablo Dorado have also contributed to the project within their respective MUSE and GIA academic programs.

“The HERCCULES project, which started as a small sketch on a blank sheet of paper, is now close to becoming a reality. It is now when we value what it means to us and without a doubt it is a unique experience for all the students involved. Our team is the only one from a Spanish university that was selected in the call and it is the first time that the Polytechnic University of Madrid participates in this program”, explains David González.

The project has also had the technical and financial support of the “Ignacio Da Riva” University Research Institute (IDR/UPM). “In the IDR team we are very satisfied with the work of this group of students, which demonstrates the quality of the technical and human training provided by the public university, and their motivation. One of the tasks of the IDR is precisely to support this type of initiative, which represents an opportunity for students to deploy their abilities and develop their interests, aligned with the research tasks of the Institute. In this case, it has been framed within the OAPES synergistic project of the Community of Madrid” according to the words of the director of the IDR, Ángel Sanz.


If the test campaign is satisfactory, and in any case, after the pertinent corrections or improvements derived from the tests carried out, HERCCULES will be ready to be launched into the stratosphere in September from the Esrange space base, in Kiruna. (Sweden). The experiment will be sent to this region of Lapland at the end of July. Several of the team members will attend the launch campaign from September 15 to 25, to integrate it into the gondola along with 3 other experiments from other European universities. HERCCULES will ascend in a helium balloon up to 35 kilometers for approximately 90 minutes. The total duration of the flight will be about 7 hours, enough time to take data from the thermal environment and from the sensors on board.

The launch and flight of this experiment, financed by the BEXUS program, was scheduled for September 2022, however, the war in Ukraine caused it to be postponed until 2023. (Source: UPM)

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