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Johnson, Les

Publications and source records attributed to Johnson, Les.

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2021

Design of Solar Sailing Trajectories Resilient to Safe Mode Events

Solar sails are an enabling technology for stand-alone small-satellite deep-space exploration. However, their always-on nature, combined with the time of flight required for deep-space missions, makes them particularly susceptible to safe mode events. Unlike missions using electric propulsion, exclusively solar sail- ing missions cannot carry extra propellant to make up for a safe mode event, and more powerful methods like expected availability cannot be directly applied. This work extends the expected availability and duty cycle approaches to solar sailing. Through an application to NASA’s Solar Cruiser mission, a 46 % increase in tra- jectory resilience is obtained at negligible change in the mission’s time of flight. Additionally, it is shown that when a safe mode event stops the spacecraft from reaching its target orbit, the developed methods reduce the expected final error by approximately an order of magnitude.

Johnson, Les↗
NASA NTRS2019

Setting Sail for the Sun: The NEA Scout & Solar Cruiser Missions

Join HAL5 as we welcome back Les Johnson, who will talk about his work on developing solar sails at Marshall Space Flight Center and its role in propulsion and exploration of the Sun. With the successful flights of NASA's NanoSail-D and the Planetary Society's LightSail, solar sails are making the transition from an interesting idea to be demonstrated to technology ready for use on space missions. Scientists and engineers here in Huntsville are doing just that with the development of the Near Earth Asteroid Scout's 925 square foot solar sail that will fly in 2020. And that's not all, in August, a team led by NASA MSFC was selected as a finalist to develop an 18,000 square foot solar sail for a project called, Solar Cruiser, that may fly as early as 2024. If you would like to learn the fundamentals of solar sailing and get the scoop on these two innovative and exciting missions, then hang on as we "Set Sail for the Sun!"

Heliophysics↗
NASA NTRS2019

Electrostatic Solar Sail: A Propellantless Propulsion Concept for an Interstellar Probe Mission

The propulsion of an electrostatic solar sail (E Sail) is obtained by extracting momentum from the solar wind through electrostatic repulsion of the positively charged solar wind ions (see Figure 1). The positively charged solar wind protons are deflected by the electric field created around the tethers.This electric field grows in diameter as the spacecraft moves away from the Sun, therefore the E Sail effective area grows. The growth of the E-Sail effective area allows the propulsive force to decrease as 1/r up to distances of 20 AU as it moves away from the Sun, unlike solar sail propulsion whose thrust decreases as 1/r 2 but only to distances of 5AU. This propulsive force is created without using propellant and, therefore, E-sail avoids both the mass and complexity of chemical rockets (that require large amounts of propellant, propellant storage tanks, plumbing, valves, and insulation).

DeStefano, Anthony M.↗
NASA NTRS2019

Near Earth Asteroid Scout: Exploring Asteroid 1991VG Using A Smallsat

After its deployment from NASA’s Space Launch System (SLS) in 2020, the Near Earth Asteroid (NEA) Scout mission will image an asteroid on a close flyby using an 86m2 solar sail as its primary propulsion. NEA Scout, with a 6U CubeSat form factor, is one of several secondary CubeSat payloads to be deployed from the SLS on its maiden flight. The NEA Scout will be ejected from the SLS on a trajectory toward the moon and will use its onboard cold gas propulsion system to attain an elliptical lunar orbit. Once the spacecraft is in orbit, the solar sail will deploy and spacecraft checkout will begin. The NEA Scout will remain in the lunar vicinity until the low-thrust trajectory to the destination asteroid, 1991VG, or another NEA of interest, can be attained. The spacecraft will then begin its 2.0 – 2.5 year journey to the asteroid. About one month before the asteroid flyby, NEA Scout will search for the target and start its Approach Phase, using a combination of radio tracking and optical navigation. The solar sail will provide continuous low thrust to enable a relatively slow flyby (10-20 m/s) of the target asteroid under lighting conditions favorable to geological imaging (<50 degree phase angle). Once the flyby is complete, and if the system is still fully functioning, an extended mission will be considered – the reconnaissance of another asteroid or a re-flyby of the first asteroid several months later are both options. NEA Scout is funded by the NASA Human Exploration and Operations Mission Directorate.

In-Space Propulsion↗
NASA NTRS2019

The Kon-Tiki Mission – Demonstrating Large Solar Sails for Deep Space Missions

Two key NASA strategic documents, Our Dynamic Space Environment: Heliophysics Science and Technology Roadmap for 2014-2033 and 2013 Solar and Space Physics: Science for a Technological Society, contain over a dozen references describing the value of solar sails to enable revolutionary new observational capabilities. Based on these needs, the NASA Marshall Space Flight Center (MSFC) developed the Kon-Tiki mission concept to mature solar sail technology for use in future Heliophysics missions, as well as missions of interest across a broad user community (e.g., space weather and Earth polar observatories). Kon-Tiki would serve as a pathfinder for missions that observe the solar environment from unique vantage points such as the Solar Polar Imager (SPI), opening a fundamentally new range of observational capabilities for the Heliophysics Program and for space weather monitoring. Observations away from the Sun-Earth line (SEL) present unique opportunities for answering the outstanding science questions of Heliophysics, for improving space-weather monitoring and prediction, and for revealing new discoveries about our Sun and solar system. High solar inclinations are particularly compelling. Investment in, and demonstration of, the technology needed to enable polar missions is essential to making this unique vantage point a reality in the next decade. Propellantless solar sails can be used to create artificial equilibria and indefinite station-keeping at locations sunward of L1 along the SEL, or at any desired offset from the SEL leading or trailing the Earth in its orbit. They can change the heliocentric inclination of a spacecraft from the ecliptic to as high as solar polar, stopping and remaining at any intermediate inclination orbit in between. Sails can be used to hover over the Earth’s poles, using solar photon pressure to offset the Earth’s gravitational attraction, creating functional equivalents of geostationary earth orbits. The Kon-Tiki mission would fly a small spacecraft with a large (>1200 square meter) solar sail containing embedded reflectivity control devices (RCDs) and photovoltaic cells. The mission concept includes successful deployment of the solar sail, validation of all sail subsystems, controlled station-keeping inside of the Sun-Earth L1 point, attitude control of the sail with the RCDs (including spinning and despinning), demonstration of pointing performance for science imaging, and finally an increase in heliocentric inclination (out of the ecliptic).

Johnson, Les↗
NASA NTRS2019

Electric Sail Propulsion for Deep Space Missions

Electrostatic Sail (E-sail) propulsion extracts momentum from the solar wind, which has minimal speeds of 400 km/sec, through electrostatic repulsion of the positively charged solar wind ions. This momentum exchange is accomplished by an array of multi-kilometer-length charged tethers biased to a high positive voltage, producing an electric field around the tethers that deflect the positively charged solar wind particles. This electric field grows in diameter as the spacecraft moves away from the sun, increasing the E-sail effective area. The growth of the E-sail effective area allows the created propulsive force to decrease at a rate closer to 1/r out to distances from the sun of up to 20 Astronomical Units (AU). This is unlike solar sail propulsion, where the thrust decreases at a rate of 1/r2 and is only effective out to distances of ~5 AU. The propulsive force is applied without expending any propellant. Although the thrust generated by an E-Sail is low, it can be applied continuously over a period of years (depending on the mission type), and can push a 500 kg spacecraft to tremendous velocities—as high as 12 AU per year—making the voyage to 600 AU in as few as 50 years after launch. The NASA Marshall Space Flight Center recently completed a NASA Innovative Advanced Concept (NIAC) study in which all of the major system- and subsystem-level aspects of an E-Sail-propelled vehicle were assessed and a maturation plan developed. If implemented, E-Sail propulsion could be realized and deployed as a viable option for space missions within a decade.

Interstellar Probe↗
NASA NTRS2019

New Moon Explorer Mission Concept

New Moon Explorer (NME) is a smallsat reconnaissance mission concept to explore Earth’s ‘New Moon’, the recently discovered Earth orbital companion asteroid 469219 Kamoʻoalewa (formerly 2016HO3), using solar sail propulsion. NME would determine Kamoʻoalewa’s spin rate, pole position, shape, structure, mass, density, chemical composition, temperature, thermal inertia, regolith characteristics, and spectral type using onboard instrumentation. If flown, NME would demonstrate multiple enabling technologies, including solar sail propulsion, large-area thin film power generation, and small spacecraft technology tailored for interplanetary space missions. Leveraging the solar sail technology and mission expertise developed by NASA for the Near Earth Asteroid (NEA) Scout mission, affordably learning more about our newest near neighbor is now a possibility. The mission is not yet planned for flight.

Johnson, Les↗
NASA NTRS2018

New Moon Explorer Robotic Precursor Mission Concept

A low-cost reconnaissance mission concept has been devised of Earth’s ‘New Moon’, the recently discovered Earth orbital companion asteroid 2016HO3. 2016HO3 provides a compelling destination to address science, economic, and asteroid protection objectives and could serve to influence the future direction of human exploration in cis-lunar space by offering an additional destination for human exploration and utilization. Key enabling technologies, solar sail propulsion, thin film power generation and telecommunications capabilities, and small spacecraft technology have reached a development milestone enabling an affordable reconnaissance mission. Leveraging the solar sail technology and mission expertise resident at the National Aeronautics and Space Administration’s (NASA) Marshall Space Flight Center (MSFC) resulting from the Human Exploration and Operations Mission Directorate (HEOMD) funded Near Earth Asteroid (NEA) Scout mission, and combining this with the science and instrument expertise at the Goddard Space Flight Center (GSFC), a 12U scale small spacecraft mission can characterize 2016HO3. Spin rate, pole position, shape, structure, mass, density, chemical composition, temperature, thermal inertia, regolith characteristics, and spectral type can be determined using a small, CubeSat form factor within a three year time of flight. This paper outlines the outcome of a concept study for the New Moon Explorer (NME), a solar sail propelled reconnaissance mission of 2016HO3.

Dervan, Jared A.↗