6
Six Degrees of Freedom -- movement along and rotation around all three spatial axes (X, Y, Z). In underwater vehicles this means surge, sway, heave (translational) plus roll, pitch, yaw (rotational). ASPEN simulates full 6-DOF dynamics for every vehicle.
B
The measurement and mapping of underwater depth and seafloor terrain. Bathymetric data defines the 3D shape of the ocean floor in ASPEN simulations, determining where vehicles can navigate and how acoustic signals reflect.
An acoustic ray-tracing propagation model that calculates how sound travels through water. Bellhop traces individual ray paths through the ocean accounting for refraction, reflection, and absorption. ASPEN uses Bellhop for realistic underwater acoustic simulation.
An open-source 8-thruster remotely operated vehicle made by Blue Robotics. It is widely used in research and education due to its modular design and accessible price point. ASPEN includes a detailed BlueROV2 digital twin with accurate thruster configuration and hydrodynamics.
I
Inertial Navigation System -- a sensor package that tracks position through dead reckoning using accelerometers and gyroscopes. INS is the primary navigation method for underwater vehicles that cannot receive GPS signals. ASPEN models INS drift and error accumulation.
NVIDIA's robotics simulation platform built on the Omniverse framework. Isaac Sim provides the core simulation engine that ASPEN extends with underwater-specific physics, ocean environments, and marine vehicle models.
M
Material Definition Language -- NVIDIA's shader and material format used in Omniverse. MDL defines how surfaces look and interact with light. ASPEN uses MDL materials for realistic underwater rendering including water caustics and seafloor textures.
A statistical technique that runs many randomized simulations to estimate probability distributions and assess risk. In ASPEN, Monte Carlo methods enable analysis of mission success rates across varying ocean conditions, sensor noise, and vehicle failures.
N
A compact, read-only GPU-optimized version of the OpenVDB sparse volumetric data structure. NanoVDB files (.nvdb) are ASPEN's runtime format for ocean data -- voxelized temperature, salinity, and current fields loaded directly onto the GPU for fast lookup.
Navy Coastal Ocean Model -- a U.S. Navy regional ocean forecast model providing higher resolution than global models like HYCOM. NCOM is used for coastal operations where finer-scale ocean dynamics matter for accurate vehicle simulation.
North-East-Down -- a coordinate convention commonly used in marine and aerospace applications where X points North, Y points East, and Z points Down. NED is the alternative to ENU and is standard in many navigation systems.
Network Common Data Form -- a standard self-describing scientific data format widely used in oceanography and atmospheric science. NetCDF is the primary input format for bathymetry and ocean model data in the ASPEN pipeline.
O
NVIDIA's visual programming and compute graph system within Omniverse. OmniGraph connects nodes to define simulation behavior, sensor processing, and action logic. ASPEN uses OmniGraph nodes for vehicle control, data flow, and environment updates.
NVIDIA's platform for building 3D simulation workflows and digital twins. Omniverse provides the rendering engine, physics runtime, and collaboration tools that form the foundation of ASPEN's simulation environment.
P
NVIDIA's GPU-accelerated physics engine for real-time rigid body simulation, collision detection, and articulated body dynamics. PhysX handles vehicle-environment interactions in ASPEN including buoyancy forces and contact physics.
Proportional-Integral-Derivative controller -- a feedback control algorithm that continuously adjusts outputs to minimize error. PID controllers are the standard low-level control method for underwater vehicle depth, heading, and speed regulation in ASPEN.
R
Remote Environmental Monitoring UnitS -- a family of AUVs developed for the U.S. Navy, widely deployed for mine countermeasures, hydrographic survey, and environmental monitoring. ASPEN can model REMUS-class vehicles for Navy-relevant mission scenarios.
Reinforcement Learning -- an AI training paradigm where an agent learns optimal behavior through trial-and-error interaction with an environment, receiving reward or penalty signals. ASPEN supports RL training for autonomous underwater vehicle navigation and decision-making.
Regional Ocean Modeling System -- a free-surface, terrain-following ocean model using curvilinear grids for high-resolution regional simulations. ASPEN's OceanModel class includes explicit ROMS support via a dedicated flag for handling its unique grid structure.
Robot Operating System 2 -- the industry-standard open-source robotics middleware providing publish/subscribe messaging, hardware abstraction, and package management. ASPEN bridges to ROS 2 for integration with real vehicle software stacks and control algorithms.
Remotely Operated Vehicle -- a tethered underwater vehicle controlled in real-time by a human operator on the surface. ROVs are connected by an umbilical cable that provides power and communications. The BlueROV2 is the primary ROV modeled in ASPEN.
NVIDIA's ray tracing GPU architecture that enables real-time ray-traced rendering. RTX GPUs are required for ASPEN to run Omniverse with hardware-accelerated rendering and GPU-based physics simulation.
S
An acoustic imaging sensor that creates detailed pictures of the seafloor by emitting fan-shaped sonar pulses to each side of the vehicle. Side-scan sonar is used for mine detection, habitat mapping, and search operations. ASPEN can simulate side-scan imagery.
Sound Velocity Profile -- a measurement of how the speed of sound in water changes with depth, influenced by temperature, salinity, and pressure. SVPs are critical for accurate acoustic modeling because they determine how sound bends and propagates underwater.
U
Universal Scene Description -- an open-source 3D scene format originally developed by Pixar. USD is the native scene format for Omniverse and ASPEN. USDA is the human-readable text variant. All simulation scenes, vehicle models, and environments are stored as USD.
Unmanned Underwater Vehicle -- the general term encompassing both AUVs (autonomous) and ROVs (remotely operated). UUV is the broadest category for any underwater vehicle that operates without an onboard human crew.