Phase II (Under construction)
A Stance-Driven 6DoF Board & Supercritical Nitrogen Propellant.
The Problem
There’s a massive gap between where we currently are with intra-vehicular mobility: free-floating and grabbing handrails- and where we want to get to: walking upright with Earth-analogue simulated gravity. We are quite a few decades and trillions of dollars away from defaulting to spinning stations for new builds. The free-floating works for very small spaces, but spaces will otherwise stay small if we don’t build out the infrastructure in the coming decades to bridge that gap to simulated gravity.
The SOLUTION
Building on the RSL/ MVS concepts, there’s an opportunity to create these large structures for several hundreds of people to live and work and move about freely, all without introducing artificial gravity. This project proposes a mobility platform that increases speed and shrinks distances in microgravity habitats just as personal mobility devices (bicycles, scooters, skateboards, etc.) do on Earth.
By decoupling translation (propulsion) from stabilization (attitude control) and mapping them to a split-deck sensorimotor interface, this system enables precise, hands-free 6-Degrees-of-Freedom (6DoF) flight. The architecture integrates a pressure-sensitive stand-on board, a wearable micro-thruster array, a sternum-mounted control moment gyroscope, and a logistics network for supercritical nitrogen propellant.
1. The Human Interface: Stance-Mapped Control Platform
Articulated Sensorimotor Flight Deck
The primary interface is not a vehicle, but a sensitive input device that translates human proprioception, specifically stance width, pressure differential, and foot articulation, into digital flight commands.
- Kinematic Architecture
- The deck consists of two symmetrical halves connected by a central pivot, allowing for torsion and independent pitch articulation. This enables Pressure-Differential Pitch Control, where vertical (ascend/descend) vectors are driven by the pressure delta between the left and right foot rather than whole-body center-of-mass shifts.
- Mechanical Indexing
- Dual Passive Sole-Lock (PSL) channels mechanically index with bars on the user’s boot, ensuring repeatable sensor alignment without requiring active latching power.
- Active Retention & Safety
- Embedded electromagnets provide vertical retention of the boot’s steel sole plate. A specific “Control Lock” gesture mechanically separates the board halves and interrupts the magnetic circuit, allowing for immediate manual egress.
- Three Stances Supported:
- Square Stance
- A specific heads-up mapping where alternating toe/heel pressure drives lateral translation (sidestepping) without yaw, enabling precise orthogonal positioning at workstations.
- Regular & Goofy
- Standard board-sport orientations allow for passage with greater perceived control and a slimmer profile in the longitudinal axis of travel.
- Square Stance
2. Actuation: Omni-Pulse Wearable Propulsion
Torso-Distributed Cold-Gas Thruster Array
Thrust is delivered via a wearable vest containing six distributed cold-gas micro-thruster nodes. This non-annular topology maximizes lever arms for high-authority torque control while keeping the center of mass predictable.
- Distributed Topology
- Nodes are located at the shoulders, flanks, and hips to generate forces and moments about all three axes.
- Sensor Fusion
- An onboard multi-IMU fuses data from the board and the vest to ascertain pose. When integrated with visual odometry, it executes automatic attitude & torque cancellation, acting as a “viscous ether” to prevent the slop of uncommanded spin.
- Infrastructure Coupling
- In corridor transit, the vest maintains a 2-3cm hover gap above the floor. This stabilizes the user for frictionless travel while keeping the board within the inductive capture range of environmental acceleration strips.
3. Stabilization: Indexed Control Moment Gyroscope (CMG)
Sternum-Mounted Attitude Control Unit
To conserve propellant during high-frequency orientation changes, a lightweight, single-gimbal CMG is integrated into the vest’s sternum plate, indexed to different axes..
- Propellant-Free Attitude
- The CMG establishes orientation (Yaw/Pitch/Roll) via angular momentum exchange, reserving gas thrusters strictly for translation. This can reduce propellant consumption by a significant amount.
- Pre-Indexing Logic
- The gimbal defaults to a Yaw-Ready orientation. For off-axis maneuvers, the system pre-indexes the gimbal (150-200ms latency masked by the scheduler) to deliver symmetric torque pulses without dumping momentum into a spin. User preset commands are capable of initiating and executing a 180° yaw in ~0.5 seconds.
4. Logistics: Supercritical Nitrogen Ecosystem
Bufferless Supercritical Cartridge & Automated Vending
To streamline operations, the system uses a Supercritical Nitrogen architecture (~375K, 180 bar).
- Bufferless Direct Feed
- The cartridge acts as a “fluid” source that expands rapidly upon valve actuation. By maintaining the propellant in a supercritical state, the system eliminates the need for heavy onboard vaporization buffers or heater stack (as in liquid nitrogen). But it’s still much denser than a ‘safe’ level of compressed nitrogen, without the catastrophic failure risk of rupture.
- The cartridges can therefore be reliably handled by inexperienced or young populations.
- The cartridge acts as a “fluid” source that expands rapidly upon valve actuation. By maintaining the propellant in a supercritical state, the system eliminates the need for heavy onboard vaporization buffers or heater stack (as in liquid nitrogen). But it’s still much denser than a ‘safe’ level of compressed nitrogen, without the catastrophic failure risk of rupture.
- Automated Vending Logic:
- A station-wide nitrogen utility infrastructure feeds wall-mounted nodes along transit corridors. These dispense pre-warmed cartridges and manage lifecycle via returns and inspection.
- Purge & Verify
- Inbound cartridges undergo a pressure-decay leak check and residual gas purge.
- Recapture
- Residual nitrogen is captured into the station’s utility lines rather than vented.
- Reject Stream (alternate path)
- Failed units are mechanically diverted to a sealed reject bin.
- Purge & Verify
5. Environmental Integration: Active Surface Coupling
Electromagnetic Velocity Control
The wearable system operates together with the facility’s programmable floor tiles (compatible with magnetic valley shaping standards for cargo transport). In the middle of long corridors, or at the entry/exit to doorways, or the end of a queue are special floor tile segments
- Velocity Control Strips
- Boost Strips: Active electromagnetic zones that impart linear acceleration to the board’s steel baseplate, effectively “towing” the user to cruise velocity.
- Decel Strips: Passive or semi-active zones that bleed momentum for safe arrival speeds.
- Handoff Logic
- The user enters a strip, the floor coils energize. At the same time, the vest downrates any translational thrust to an idle, conserving propellant so the infrastructure can provide the kinetic energy.
Open Research Questions
The transition from architectural definition to flight-readiness requires addressing specific challenges in biomechatronics and control theory. These questions define the bulk of the required research.
In addition, each question yet to be answered for RSL/MVS remains an open blocker in enabling Phase II.
- Sensory Conflict & Biomechanics:
- Without gravity, the vestibular system lacks the “down” cue typically associated with leaning.
- Research Question
- How can we map foot-pressure differentials to pitch/roll without inducing sensory conflict?
- Control Loop Latency:
- The controller is on the feet, but the thrusters are on the torso. This creates a non-rigid control body introduced by hip and knee flexion.
- Research Question
- How can we model and compensate for the biomechanical lag in this chain to prevent a Pilot-Induced Oscillation (PIO)-likened scenario during aggressive maneuvers?
- Human-Infrastructure Handoffs:
- Transferring a floating human from a fluid-dynamic drive (thrusters) to a magnetic drive (floor strips) creates a potential jerk impulse.
- Research Question
- How can we create “soft-catch” control laws that ramp electromagnetic current based on the approach velocity and mass of the rider to ensure smooth coupling?
- Fluid Dynamics at Micro-Scales:
- Bufferless supercritical nitrogen experiences rapid pressure drop during expansion.
- Research Question
- How can we develop micro-valve pulse width modulation (PWM) strategies that prevent Joule-Thomson effect from freezing the nozzle or degrading impulse precision?
- Materials Science:
- Building containers that can handle high heat, high pressure, and non-cylindrical geometry introduces meaningful trade-offs.
- Research Question
- How can we develop cartridges to maximize supercritical nitrogen mass while maintaining safe, ergonomic, efficient form factors?
Next Steps
Build the floor.