Development and test of a measurement system for in-situ mesaurements of volcanic ashes and radioactivity for the continuing safety of civil aviation using a drone
With the project MEASURE, a joint venture with three partners from federation, applied research and industry is funded by the Federal Ministry for Economic Affairs and Climate Action (BMWK) in context of the national aviation research program Lufo VI-1. The aim of the project is the development of an in-situ measurement system in order to quickly obtain data in the event of contaminated airspace, e. g. by radioactivity or volcanic ash (see Figure 1), enabling targeted actions to maintain aviation safety. The three partners, German Weather Service (DWD), German Aerospace Center (DLR, Institute of Air Transport) and enviscope GmbH are adapting in-situ measurement technology to a Remotely Piloted Aircraft System (RPAS) and are developing a smart flight trajectory tool based on dispersion calculations for an efficient aerial survey of the operation area. On completion of the project, the capability of the system is proven as part of a demonstration campaign. In the long term, a warning system is to be set up for operational use throughout Germany.
Figure 1: Pollutant distributions for two exemplary disaster scenarios. The unmanned measurement system shall be developed to contribute to the prediction of such scenarios with valuable in-situ measurements. Left: Incident at the nuclear power plant in Fukushima (2011). Right: Fictious volcanic eruption of Grimsvoetn in Iceland.
The main task of enviscope within MEASURE is the development and adaptation of the measurement technology to a Do-DT 25 drone operated by the subcontractor Airbus Defense & Space (see Figure 2), which was selected as a suitable available carrier platform for the desired measurements in the upper troposphere due to its performance data.
The carrier platform offers installation compartments at the wingpods and in the nose compartment, which can be equipped with a total mass of approx. 30 kg. For these installation compartments, enviscope developed modules for the in-situ measurement of aerosol and radioactivity, the collection of meteorological and avionic data as well as infrastructure, data recording and transmission, which are briefly presented below. Furthermore, initial information is provided on the dropsondes for aerosol and radioactivity, which are still under development and will be used to additionally obtain vertical profiles of the pollutants.
Source: Airbus Target Drone Systems
Figure 2. In the MEASURE project, the Do-DT 25 serves as an airborne platform for the measurement modules determining the mass concentration of aerosol particles (volcanic eruption) or the local dose rate (radioactive incident), respectively.
Wingpods
In particular, the instrument carriers in the wingpods have been designed for high g-loads on the fast-flying drone, which are mainly caused by the catapult take-off and the impact on landing with the parachute (see Figure 3). In addition, the carriers, which are fitted with sensitive optical or electronic measurement components, are equipped with self-developed shock absorption systems to protect them against these adverse conditions.
Figure 3. Shock-absorbing instrument carrier developed by enviscope for mounting the gamma spectrometer and the optical particle counter. Above: Strength analysis at 20g load. Below: Photo of the volcanic ash carrier.
Wingpod 1 – Aerosol
The core measurement for scenario 1 (volcanic eruption) is the mass concentration of aerosol particles in the size range from 0.3 µm to 10 µm, which is used as a direct measure for limitations in civil aviation. Particles are detected with an optical particle counter integrated in a wingpod of the Do-DT 25 (see Figure 4) and supported by a visibility sensor (cloud detection) and a temperature/humidity sensor. The selected commercially available optical particle counter was adapted by enviscope for use on the drone. The visibility measurement paired with the measurement of relative humidity allows to differentiate between liquid (clouds) and solid particles (ash, soot, dust, etc.).
Figure 4. Illustration of the developed volcanic ash module for one of the wingpods of the Do-DT 25 carrier system.
To capture aerosol particles during flight, enviscope has developed a passively operated, two-staged inlet system, which is specifically designed to operate between altitudes of 4 – 10 km height. It works exclusively via the pressure distribution on the wingpod resulting from the air flow during flight (see Figure 5). To minimize particle losses, the flow path from the outside tip to the optical particle counter is kept as straight as possible. Isokinetic flow conditions have been achieved by designing the inlet tips based on flow simulations.
Figure 5. Left: Assembly of the passively operated, two-staged inlet system for use of the optical particle counter to determine the mass concentration of aerosol particles on the drone. Right: Flow simulations carried out to adjust isokinetics conditions at the inlet junctions.
Wingpod 2 – Radioactivity
The key parameter in the event of a radioactive incident is the local dose rate. It is measured with a gamma spectrometer on the drone. In addition, a filter collector for radioactive particles is planned to be able to carry out a laboratory analysis of the particles afterwards, whereby the nuclide vector is determined as an important additional information. The used gamma spectrometer is commercially available and has been adapted by enviscope for operations on the drone.
Nose Compartment
The entire infrastructure required for operation is housed in an equipment carrier in the nose compartment (see Figure 6). A GPS module is also installed here to determine the flight attitude and position. By combining the pollutant concentrations with these flight parameters, the spatial distribution of the pollutants along the selected flight route can be determined. The flight route is determined in advance based on the initial dispersion calculations by DWD and the performance limits of the Do-DT 25 carrier platform using AI-supported algorithms by the joint partner DLR.
Figure 6. Illustration of the equipment carrier integrated in the nose compartment of the Do-DT 25.
All the data collected, including the vertical profiles of the dropsondes, can be transmitted online to the DWD using specially developed data transmission technology to enable real-time validation and re-scaling of the available dispersion calculations.
Dropsondes
To determine vertical profiles of pollutant concentrations, enviscope is developing miniaturised dropsondes that are to be dropped from the drone using a launcher (see Figure 6). The form factor of the new dropsondes is based on commercially available dropsondes. They can, therefore, also be used on research aircraft in the future. The new dropsondes have a modular design to determine either the mass concentration of aerosol particles or the local dose rate, depending on the disaster scenario. The data collected is sent back to the drone. The communication modules required for this are based on LoRa technology and are developed by enviscope.
Figure 6. Designs of three different modules of the new miniaturized dropsonde. Left: The basic module including components for communication and basic meteorological sensing (temperature, relative humidity, pressure, wind velocity). Middle: Module to determine the local dose rate. Right: Module to determine mass concentration of aerosol particles.
