IntroductionThe rapid growth of CubeSat deployments in Low Earth Orbit (LEO) has intensified the need for reliable end-of-life disposal strategies to mitigate the accumulation of space debris. This present study proposes an Earth-rotation-aware burn longitude methodology for targeted atmospheric re-entry of CubeSat using a single finite-duration retrograde de-orbit manoeuvre. Accurate longitude-targeted atmospheric entry of CubeSat requires accounting for Earth’s rotation during the coast phase between burn execution and atmospheric interface.MethodsThis study presents an analytical Earth-rotation-aware burn-longitude guidance model that incorporates J2 perturbation and atmospheric drag effects. The proposed guidance framework is integrated with a GPS-based navigation system and an Extended Kalman Filter (EKF)-assisted Attitude Determination and Control System (ADCS) for autonomous burn execution. Numerical simulations are performed for a 5.33 kg (dry mass) 4U CubeSat in circular low Earth orbits at 500 km, 600 km, and 700 km initial altitudes. Forward–only GMAT simulations independently assess the resulting re-entry trajectory without imposing a re-entry-longitude constraint, while Monte Carlo simulations evaluate the variation in the predicted re-entry longitude.ResultsThe required burn longitudes are determined as 91.36°W, 91.47°W and 91.58°W, corresponding to Earth-rotation longitude of 11.37°, 11.50° and 11.63°, respectively, enabling accurate re-entry longitude targeting. The corresponding atmospheric-entry interface is characterized by the predicted re-entry longitude and latitude. Orbit-transfer analysis indicates that retrograde velocity increments of 108.9–162.1 m/s are sufficient to lower the perigee to the 120 km atmospheric-entry interface using less than 0.5 kg of hydrazine monopropellant. The analytical model predicts transfer times to the 120 km atmospheric entry interface ranging from 45.38 min at an initial altitude of 500 km to 46.41 min at 700 km.DiscussionThe proposed method provides a computationally efficient and practically implementable approach for controlled CubeSat disposal and re-entry planning in LEO.
Introduction Deep-space missions will progressively limit real-time ground support, rapid evacuation and resupply, creating a need for medical capabilities that can operate with graded autonomy. Artificial intelligence (AI) may support this transition, but terrestrial performance cannot be equated with spaceflight readiness. Methods We conducted a narrative, hypothesis-generating review of literature relevant to AI-enabled space healthcare. Sources were selected iteratively for their contribution to health monitoring, biofluid analysis, medical imaging, clinical decision support or radiation assessment. The review did not use a systematic screening protocol or formal meta-analytic quality assessment; therefore, findings are synthesised qualitatively and claims are calibrated to evidence maturity. Results Evidence was grouped as spaceflight operational use, space-relevant prototype or analogue demonstration, terrestrial clinical validation, terrestrial experimental demonstration, or conceptual transfer. AI may support personalised monitoring, biofluid interpretation, ultrasound acquisition and analysis, radiation forecasting and clinical decision support. However, most cited applications remain terrestrial demonstrations. Key barriers include limited astronaut data, shifted physiological baselines, restricted computation and power, sensor and storage constraints, model drift, explainability, uncertainty management and failure handling. Conclusion AI is most plausibly deployed as one component of an integrated autonomous medical system that combines wearables and biosensors, onboard records, imaging, radiation monitoring, clinical decision support, crew oversight and delayed telemedical consultation. Near-term priorities are prospective validation in mission-relevant analogues, personalised baselines, resource-aware edge deployment, explicit uncertainty thresholds, human override and pre-defined safe fallback procedures. AI should augment rather than replace telemedicine and professional judgement.
Drosophila melanogaster has flown on rockets and spacecraft since 1947 and is one of the most widely used animals in gravitational biology, owing to its short life cycle, genetic tractability, modest hardware requirements and ability to develop and reproduce in orbit. Several recent reviews have catalogued its responses to spaceflight and altered gravity. This Mini Review addresses two questions. First, does sensitivity to altered gravity differ across developmental stages once differences in study design are taken into account? Second, how confidently can responses observed on ground-based platforms be attributed to altered gravity rather than to platform-specific physical or environmental factors? The available evidence identifies oogenesis, embryogenesis and metamorphosis as candidate gravity-sensitive windows, but studies of different stages have used different strains, hardware, exposure durations, gravity levels, controls and endpoints, so the data do not yet support a ranking of stages by sensitivity. Adult responses in immunity, cardiac function, the nervous system and behavior are documented in spaceflight, and in-flight 1 g centrifuge controls show that only part of them can be attributed to reduced gravity. Each ground-based platform introduces characteristic confounders, including fluid motion and limited gas exchange on rotating devices, strong magnetic fields in diamagnetic levitation and Coriolis forces in centrifuges. We summarize, for each platform, the applicable sample scale, main confounders and required controls. Finally, we discuss acoustic levitation, a contact-free technique that does not reproduce free fall and propose the validation steps it would require before use as an altered-gravity platform.
We propose a theoretical propulsion architecture in which the Casimir effect drives a mechanical see-saw oscillator that repeatedly impacts piezoelectric crystals, converting the resulting mechanical energy into electrical current. This harvested current is stored and used to power a magnetoplasmadynamic (MPD) thruster for interstellar space propulsion. The see-saw mechanism addresses a fundamental challenge of Casimir-piezoelectric harvesting: the piezoelectric effect requires changing mechanical strain, not static force, to produce continuous current. By alternating the Casimir-driven collapse of opposing plates onto piezoelectric elements, the architecture produces a repeatable cycle of charge generation. Onboard waste heat from the spacecraft’s radioisotope thermoelectric generator (RTG) provides the external energy input via thermal expansion of the see-saw beam, resetting the Casimir gaps after each impact; the Casimir force serves as the closing mechanism rather than the energy source. Temperature additionally serves a regulatory role via thermal corrections to optimize oscillation characteristics. Scaled across a large array of nanoscale Casimir gaps at the aft of the spacecraft, this framework is proposed as a candidate supplementary high-specific-impulse electric propulsion concept for interstellar missions. We outline the theoretical chain, present order-of-magnitude scaling analysis, identify key open questions and scaling constraints, and propose directions for future work. Experimental work has validated that piezoelectric elements can detect and respond to Casimir-scale forces, supporting the physical basis of this architecture. The architecture provides continuous supplementary MPD thrust for the operational lifetime of the onboard reactor without drawing from the primary power budget, limited only by propellant supply.
