Engineering topics

Johnson, Charles

Publications and source records attributed to Johnson, Charles.

3 records

NASA NTRS2019

Advanced Diffractive MetaFilm Sailcraft

A fast-tracked multifaceted approach that integrated NASA, industry, and academia was successfully executed to advance the novel concept of radiation pressure by means of a thin diffractive film. This pioneering new approach to light sailing was found to offer advantages over reflective sails - especially for missions that include close orbits or a close fly-by of the sun.The research effort included experiments, numerical modeling, and an "incubator meeting" that brought together over 35 researchers and stakeholders to uncover some of the most feasible means of advancing both the TRL and mission capabilities of diffractive sailcraft. One of the outcomes of the incubator meeting was to focus this Phase I research on a solar polar orbiter mission for heliophysics experiments. NASA decadal surveys and other reports have repeatedly pointed out that scientists have only a paucity of information about the sun beyond the ecliptic plane. The TRL has been advanced from 1 to 3 during this Phase I research with the help of experiments that have verified the predicted force and mechanical control afforded by diffractive sails. Knowledge gained from the experiments and numerical models was not only disseminated in peer reviewed publications and conferences, but it also resulted in a patent disclosure.

Diffractive↗

NASA NTRS2013

Tethered Satellites as an Enabling Platform for Operational Space Weather Monitoring Systems

Tethered satellites offer the potential to be an important enabling technology to support operational space weather monitoring systems. Space weather "nowcasting" and forecasting models rely on assimilation of near-real-time (NRT) space environment data to provide warnings for storm events and deleterious effects on the global societal infrastructure. Typically, these models are initialized by a climatological model to provide "most probable distributions" of environmental parameters as a function of time and space. The process of NRT data assimilation gently pulls the climate model closer toward the observed state (e.g., via Kalman smoothing) for nowcasting, and forecasting is achieved through a set of iterative semi-empirical physics-based forward-prediction calculations. Many challenges are associated with the development of an operational system, from the top-level architecture (e.g., the required space weather observatories to meet the spatial and temporal requirements of these models) down to the individual instruments capable of making the NRT measurements. This study focuses on the latter challenge: we present some examples of how tethered satellites (from 100s of m to 20 km) are uniquely suited to address certain shortfalls in our ability to measure critical environmental parameters necessary to drive these space weather models. Examples include long baseline electric field measurements, magnetized ionospheric conductivity measurements, and the ability to separate temporal from spatial irregularities in environmental parameters. Tethered satellite functional requirements are presented for two examples of space environment observables.

Gilchrist, Brian E.↗

NASA NTRS2011

Electrodynamic Tethers for Novel LEO Missions

The exponential increase of launch system size - and cost - with deltaV makes missions requiring large total impulse cost prohibitive. Northrop Grumman and partners have matured a fundamentally different method for generating propulsion using electrodynamic tethers (EDTs) that escapes the limitations of the rocket equation. With essentially unlimited delta V, we can perform new classes of missions that are currently unaffordable or unfeasible.

Kantner, Michael↗