Open Access

There is significant interest in sampling subglacial environments for geochemical and microbiological studies, yet those environments are typically difficult to access. Existing ice-drilling technologies make it cumbersome to maintain microbiologically clean access for sample acquisition and environmental stewardship of potentially fragile subglacial aquatic ecosystems. With the "IceMole", a minimally invasive, maneuverable subsurface ice probe, we have developed a clean glacial exploration technology for in-situ analysis and sampling of glacial ice and sub- and englacial materials. Its design is based on combining melting and mechanical stabilization, using an ice screw at the tip of the melting head to maintain firm contact between the melting head and the ice. The IceMole can change its melting direction by differential heating of the melting head and optional side wall heaters. Downward, horizontal and upward melting, as well as curve driving and penetration of particulate-ladden layers has already been demonstrated in several field tests. This maneuverability of the IceMole also necessitates a sophisticated on-board navigation system, capable of autonomous operations. Therefore, between 2012 and 2014, a more advanced probe was developed as part of the "Enceladus Explorer" (EnEx) project. The EnEx-IceMole offers systems for accurate positioning, based on in-ice attitude determination, acoustic positioning, ultrasonic obstacle and target detection, which is all integrated through a high-level sensor fusion algorithm. In December 2014, the EnEx-IceMole was used for clean access into a unique subglacial aquatic environment at Blood Falls, Antarctica, where an englacial brine sample was successfully obtained after about 17 meters of oblique melting. Particular attention was paid to clean protocols for sampling for geochemical and microbiological analysis. In this contribution, we will describe the general technological approach of the IceMole and report on the results of its deployment at Blood Falls. In contrast to conventional melting-probe applications, which can only melt vertically, the IceMole realized an oblique melting path to penetrate the englacial conduit. Experimental and numerical results on melting at oblique angles are rare. Besides reporting on the IceMole technology and the field deployment itself, we will compare and discuss the observed melting behavior with re-analysis results in the context of a recently developed numerical model. Finally, we will present our first steps in utilizing the model to infer on the ambient cryo-environment.

Lifting propellers operate at oblique inflow and thus encounter severe dynamic loads during forward flight, impacting structural integrity, fatigue, and vibration. Numerical optimisation approaches consider aerodynamic, structural mechanical, and aeroacoustic aspects within preliminary design. To also account for dynamic loads during forward flight, a novel procedure allows their rapid estimation. Based on steady-state simulations combining strip theory and beam finite elements, aerodynamic excitation, damping, and stiffness are defined in the frequency domain. Loads are derived through a linear inflow model and quasi-steady aerodynamics. Damping and stiffness loads are linearised and transferred into matrix form to calculate the frequency response. The computationally expensive need for simulations in the time domain is thus avoided. Applicability extends to both fixed and variable pitch lifting propellers utilised in large multicopters for cargo or passenger transportation. Comparisons to time-marching simulations show good agreement with deviations of approximately 10%. The analytical derivation yields physical insights to understand and reduce dynamic loads and their magnification due to resonance.

Kawasaki (KHI) has made various improvements and commercialized hydrogen gas turbines for existing diffusion combustors (0–100 vol.% H2, wet combustion) and lean pre-mixed DLE combustors (0–30 vol.% H2). However, it is challenging for conventional combustion technology to achieve dry low NOx emissions for 100 vol.% hydrogen. Kawasaki’s unique approach is the development of a new dry combustion technology for high hydrogen content fuel: the micromix (MMX) combustion. Kawasaki established this combustion technology to achieve low NOx for 100 vol.% hydrogen combustion. Micromix is based on a large number of miniaturized non-premixed-type flames, making this concept inherently safe toward flashback. Recently, Kawasaki has commercialized a gas turbine with a micromix combustor as the world’s first dry gas turbine capable for 100 vol.% hydrogen. This paper shows the latest improvements of the micromix combustor before the commercialization with focus on NOx reduction achieved by decreasing the fuel injection hole diameter, and the extension of the operational flexibility by applying a supplemental burner system. During demonstration tests with a 1.8 MWel gas turbine, it could be proven that this novel combustion concept meets Japan’s fundamental NOx regulations (84 ppm referred to 15 vol.% residual O2) for pure hydrogen and furthermore can be operated with natural gas/hydrogen blends in the range up to 50 vol.% H2 over the entire load range.

This paper presents initial findings from aeroelastic studies conducted on a wing-propeller model, aimed at evaluating the impact of aerodynamic interactions on wing flutter mechanisms and overall aeroelastic performance. The flutter onset is assessed using a frequency-domain method. Mid-fidelity tools based on the time-domain approach are then exploited to account for the complex aerodynamic interaction between the propeller and the wing. Specifically, the open-source software DUST and MBDyn are leveraged for this purpose. The investigation covers both windmilling and thrusting conditions. During the trim process, adjustments to the collective pitch of the blades are made to ensure consistency across operational points. Time histories are then analyzed to pinpoint flutter onset, and corresponding frequencies and damping ratios are identified. The results reveal a marginal destabilizing effect of aerodynamic interaction on flutter speed, approximately 5%. Notably, the thrusting condition demonstrates a greater destabilizing influence compared to the windmilling case. These comprehensive findings enhance the understanding of the aerodynamic behavior of such systems and offer valuable insights for early design predictions and the development of streamlined models for future endeavors.

Subglacial environments on Earth offer important analogs to Ocean World targets in our solar system. These unique microbial ecosystems remain understudied due to the challenges of access through thick glacial ice (tens to hundreds of meters). Additionally, sub-ice collections must be conducted in a clean manner to ensure sample integrity for downstream microbiological and geochemical analyses. We describe the field-based cleaning of a melt probe that was used to collect brine samples from within a glacier conduit at Blood Falls, Antarctica, for geomicrobiological studies. We used a thermoelectric melting probe called the IceMole that was designed to be minimally invasive in that the logistical requirements in support of drilling operations were small and the probe could be cleaned, even in a remote field setting, so as to minimize potential contamination. In our study, the exterior bioburden on the IceMole was reduced to levels measured in most clean rooms, and below that of the ice surrounding our sampling target. Potential microbial contaminants were identified during the cleaning process; however, very few were detected in the final englacial sample collected with the IceMole and were present in extremely low abundances (∼0.063% of 16S rRNA gene amplicon sequences). This cleaning protocol can help minimize contamination when working in remote field locations, support microbiological sampling of terrestrial subglacial environments using melting probes, and help inform planetary protection challenges for Ocean World analog mission concepts.