arrow_back_ios

Main Menu

See All Software See All Instruments See All Transducers See All Vibration Testing Equipment See All Electroacoustics See All Acoustic End-of-Line Test Systems See All Academy See All Resource Center See All Applications See All Industries See All Services See All Support See All Our Business See All Our History See All Global Presence
arrow_back_ios

Main Menu

See All nCode - Durability and Fatigue Analysis See All ReliaSoft - Reliability Analysis and Management See All Test Data Management See All DAQ Software See All Drivers & API See All Utility See All Vibration Control See All High Precision and Calibration Systems See All DAQ Systems See All S&V Hand-held Devices See All Industrial Electronics See All Power Analyzer See All S&V Signal Conditioner See All Acoustic Transducers See All Current and Voltage Sensors See All Displacement Sensors See All Force sensors See All Load Cells See All Multi Component Sensors See All Pressure See All Strain Sensors See All Strain Gauges See All Temperature Sensors See All Tilt Sensors See All Torque Sensors See All Vibration See All Accessories for Vibration Testing Equipment See All Vibration Controllers See All Measurement Exciters See All Modal Exciters See All Power Amplifiers See All LDS Shaker Systems See All Test Solutions See All Actuators See All Combustion Engines See All Durability See All eDrive See All Production Testing Sensors See All Transmission & Gearboxes See All Turbo Charger See All Training Courses See All Acoustics See All Asset & Process Monitoring See All Custom Sensors See All Data Acquisition & Analysis See All Durability & Fatigue See All Electric Power Testing See All NVH See All Reliability See All Smart Sensors See All Vibration See All Weighing See All Automotive & Ground Transportation See All Calibration See All Installation, Maintenance & Repair See All Support Brüel & Kjær See All Release Notes See All Compliance See All BKSV Worldwide Contacts
arrow_back_ios

Main Menu

See All API See All Experimental Testing See All Piezoelectric Charge Accelerometers See All Piezoelectric CCLD (IEPE) accelerometers See All Electroacoustics See All Noise Source Identification See All Environmental Noise See All Sound Power and Sound Pressure See All Noise Certification See All Industrial Process Control See All Structural Health Monitoring See All Electrical Devices Testing See All Electrical Systems Testing See All Grid Testing See All High-Voltage Testing See All Vibration Testing with Electrodynamic Shakers See All Structural Dynamics See All Machine Analysis and Diagnostics See All Dynamic Weighing See All Vehicle Electrification See All Calibration Services for Transducers See All Calibration Services for Handheld Instruments See All Calibration Services for Instruments & DAQ See All On-Site Calibration See All Resources See All Software License Management

Experimental stress analysis: students conquer the outer limits of the troposphere with HBK

ARIS and ETH Zurich, Switzerland 

Introduction

Students from the Academic Space Initiative Switzerland (ARIS) at the Eidgenössische Technische Hochschule Zurich (ETH Zurich) public research university have been building research rockets since 2017. In 2020/21, a team of more than 50 motivated students, studying for Bachelor, Masters or PhD degrees, produced the 4th generation of research rockets as part of the PICCARD project, and entered the European Rocketry Challenge (EuRoC) in Portugal.

Their aim was to win the prize in the category, ‘a student researched and developed engine reaching an altitude of 30,000 feet’ with their PICCARD research rocket. For the first time, the research rocket had a hybrid-propellant engine, developed by the students. The functional capabilities of the system were demonstrated by a successful launch at the EuRoC in October 2021. This success was also achieved by virtue of a new monitoring system to measure the loads on the research rocket’s aerostructure. The HBK strain gauges used in this system delivered valuable information about bending moments and axial forces occurring during all phases of flight.

This then formed the basis for further optimizing the research rocket, and successful participation in the Spaceport America Cup 2022 in New Mexico. Here, as part of the HELVETIA follow-up mission, the team wants to successfully carry a four-kilogram payload to a height of 30,000 feet and bring all parts of the rocket safely back down to Earth.

chevron_left
chevron_right

ETH Zurich students reach for the stars

The non-profit association Academic Space Initiative Switzerland was founded at the ETH Zurich public research university in August 2017. Ever since, it has encouraged students to deploy their theoretical knowledge into practical projects. So, the ARIS teams develop rockets to enter competitions around the world for young academics and ambitious non-profit organizations.

2020 saw the launch of the 4th ARIS mission with the PICCARD project. The aim of this mission is to win the Spaceport America Cup 2022 in New Mexico. For this competition, the team want their rocket to transport a payload of four kilograms to a height of 30,000 feet and then return all components safely to Earth. To achieve this, 50 motivated students developed the completely new PICCARD rocket.

For the first time, unlike its predecessors with outsourced drive technology, the PICCARD has a student researched and developed hybrid-propellant engine. The new rocket achieved a successful first flight at the European Rocketry Challenge in Portugal, demonstrating that the system works.

As well as the new engine, a monitoring system integrated in the rocket and based on HBK strain gauges was used for the first time. With its help, the HELVETIA team were able to gather valuable data during the flight, enabling targeted optimization of the rocket for a successful launch in New Mexico.

The non-profit association Academic Space Initiative Switzerland was founded at the ETH Zurich public research university in August 2017. Ever since, it has encouraged students to deploy their theoretical knowledge into practical projects. So, the ARIS teams develop rockets to enter competitions around the world for young academics and ambitious non-profit organizations.

2020 saw the launch of the 4th ARIS mission with the PICCARD project. The aim of this mission is to win the Spaceport America Cup 2022 in New Mexico. For this competition, the team want their rocket to transport a payload of four kilograms to a height of 30,000 feet and then return all components safely to Earth. To achieve this, 50 motivated students developed the completely new PICCARD rocket.

For the first time, unlike its predecessors with outsourced drive technology, the PICCARD has a student researched and developed hybrid-propellant engine. The new rocket achieved a successful first flight at the European Rocketry Challenge in Portugal, demonstrating that the system works.

As well as the new engine, a monitoring system integrated in the rocket and based on HBK strain gauges was used for the first time. With its help, the PICCARD team were able to gather valuable data during the flight, enabling targeted optimization of the rocket for a successful launch in New Mexico.

The steep road to an optimum aerostructure

A sufficiently rugged aerostructure is essential for ensuring that the PICCARD rocket can successfully achieve its flight and return to Earth. It has to cope with all the forces occurring at all phases of the flight while being as lightweight as possible. That is the only way it and its payload can be self-propelled to the desired height. Therefore, the team needs precise knowledge of all possible loads acting on the structure during flight, so that the rocket can be endowed with maximum strength and minimal weight.

During the development of the PICCARD, the students used simulation to determine the most important fundamental parameters for designing the rocket’s aerostructure. However, models only give an approximate idea of external influences that are difficult to predict, such as wind. By contrast, in-flight measurements deliver precise data on actually occurring forces, which in turn enables optimum design of the aerostructure.

Successful launch of mission monitoring system

In a separate sub-project, the students developed a lightweight, easy-to-implement and yet precise monitoring system for the PICCARD mission. The finished system was installed above the tank of the rocket, allowing the bending moments and axial forces occurring during the rocket’s flight to be recorded. This data now forms the basis for further optimization of the design of the rocket’s structural parts, in the hope of taking first place in the 2022 Spaceport America Cup.

A total of three Wheatstone bridges, two for moments in the x and y directions and one for axial forces in the z direction, each with two HBK strain gauges, were installed in the monitoring system for measuring loads. The strain gauges were attached to the inside of the rocket’s carbon-fiber shell. 350Ω strain gauges were used and supplied with a high-precision voltage of 3.3 V. All signal cables were shielded to ensure optimum signal quality and grounded on the circuit board. Previous tests showed that the module generated very little noise. The sensors were calibrated by means of a 3-point bending test. To demonstrate bending load, loads up to three quarters of the maximum were introduced.

The strain gauge setup for the bending moments enabled the deformations to be compensated by axial forces and temperatures. On the other hand, the setup for axial forces measured force components caused by bending and normal forces, and only compensated for temperature-induced deformations. To gain direct information on axial forces, further processing of this measured data is required.

Precise data enables optimized structural parts

The new monitoring system demonstrated its capabilities during its first use in Portugal. It reliably measured loads during the flight and delivered most of the hoped-for data. The axial forces and bending moments in the x and y directions could be precisely determined from the rocket’s launch to the apogee (highest point) of its flight.

Unfortunately, it was not possible to collect meaningful data during the return to Earth: the parachutes did not deploy as planned at the apogee due to a technical fault in the parachute system. They opened only during the descent, when the rocket was falling at a speed of 240 m/s. The shock forces this caused were so great that the rocket broke apart.

Despite the lack of measured values for the descent, the data still enables a better understanding of the system. This way, the aerostructure of the PICCARD rocket can be further optimized, raising the possibility of victory at the 2022 Spaceport America Cup.

HBK delivering the best results

When choosing the measurement technology to be employed in the newly developed monitoring system, strain gauges from HBK were the obvious choice. The decision was based on positive experiences in the past, coupled with the company’s international reputation as a supplier of measurement technology that delivers precise results even under the most demanding environmental conditions. Another advantage was the ease with which the strain gauges could be integrated, living up to HBK’s promise of ‘plug and measure’. In addition, the HBK team were dedicated to supporting the PICCARD project with help and advice. This, plus HBK’s identification with the mission’s goals, are convincing arguments in favour of future collaboration and further successful projects.

About ARIS and ETH Zurich

At the Academic Space Initiative Switzerland, motivated students at the ETH Zurich public research university have been working intensively on building rockets since 2017. Their goal is to apply and deepen their theoretical knowledge to successfully take part in various aerospace competitions. ETH Zurich is a university specializing in technology and the natural sciences. It was established in 1855 and is today one of the world’s best-known universities. Around 23,000 undergraduates and postgraduates are enrolled in 16 departments.

Technology used