A Pressure-Supported Pneumatic Architecture for Robust Deep Drilling on Mars: Performance Modeling, Sizing, and Mission Integration.

Accessing the martian deep subsurface is a long-standing scientific priority for astrobiology, climate reconstruction, and planetary evolution, yet robotic drilling missions have historically been limited by wellbore instability, loss of working-fluid circulation, and the risk of irrecoverable tool entrapment. This work presents and evaluates a wireline, downhole-actuated pneumatic drilling architecture designed to directly mitigate these mission-ending risks through active wellbore pressure support and continuous cuttings removal within a single, sealed CO₂ circulation system. The proposed system combines a rotary-percussive bottomhole assembly with a deployable sealing membrane and a closed CO₂ pneumatic circuit that provides both mechanical support to the borehole wall and transport of generated cuttings to the surface. Reduced-order flow physics models are developed to capture compressible gas transport, particle entrainment, porous leak-off, junction losses, incompressible liquid tether flow, and phase-change thermodynamics. These models are assembled into section-wise drilling and cleanout cycles and integrated into a mission-level simulator that enforces realistic sol-level constraints on time, energy, battery usage, and working-fluid mass. Mission simulations demonstrate that cleanout operations dominate both energy and CO₂ mass budgets, establishing wellbore pressure support as a first-order design variable rather than a secondary constraint. Modest relaxation of the maintained back-pressure from an overburden-matched level to a derated fraction substantially reduces cleanout energy demand and idle leak-off penalties while preserving effective particle transport. Under an InSight/Mars Life Explorer-class mission envelope, the architecture exceeds a 30 m baseline depth target well within the nominal operational window, with favorable scaling toward ∼100 m depths through increased mission duration and resource allocation. By explicitly coupling drilling, cuttings removal, and wellbore stability within a single operational framework, this architecture targets the primary failure modes identified in deep martian subsurface access. The results indicate, at the concept and reduced-order sizing level, that pressure-supported pneumatic drilling may provide a scalable pathway for deep drilling on Mars and other low-pressure planetary bodies, while identifying the subsystem validation needed before flight-system viability can be assessed.