Travis Brashears | University of California, Berkeley (original) (raw)

Papers by Travis Brashears

Recently, there has been a dramatic change in the way space missions are viewed. Large spacecraft... more Recently, there has been a dramatic change in the way space missions are viewed. Large spacecraft with massive propellant-filled launch stages have dominated the space industry since the 1960’s, but low-mass CubeSats and low-cost rockets have enabled a new approach to space exploration. In recent work, we have built upon the idea of extremely low mass (sub 1 kg), propellant-less spacecraft that are accelerated by photon propulsion from dedicated directed-energy facilities. Advanced photonics on a chip with hybridized electronics can be used to implement a laser-based communication system on board a sub 1U spacecraft that we call a WaferSat. WaferSat spacecraft are equipped with reflective sails suitable for propulsion by directed-energy beams. This low-mass spacecraft design does not require onboard propellant, creating significant new opportunities for deep space exploration at a very low cost. In this paper, we describe the design of a prototype WaferSat spacecraft, constructed on...

In the nearly 60 years of spaceflight we have accomplished wonderful feats of exploration and sho... more In the nearly 60 years of spaceflight we have accomplished wonderful feats of exploration and shown the incredible spirit of the human drive to explore and understand our universe. Yet in those 60 years we have barely left our solar system with the Voyager 1 spacecraft launched in 1977 finally leaving the solar system after 37 years of flight at a speed of 17 km/s or less than 0.006% the speed of light. As remarkable as this is, we will never reach even the nearest stars with our current propulsion technology in even 10 millennium. We have to radically rethink our strategy or give up our dreams of reaching the stars, or wait for technology that does not exist. While we all dream of human spaceflight to the stars in a way romanticized in books and movies, it is not within our power to do so, nor it is clear that this is the path we should choose. We posit a technological path forward, that while not simple; it is within our technological reach. We propose a roadmap to a program that will lead to sending relativistic probes to the nearest stars and will open up a vast array of possibilities of flight both within our solar system and far beyond. Spacecraft from gram level complete spacecraft on a wafer (" wafer sats ") that reach more than ¼ c and reach the nearest star in 15 years to spacecraft with masses more than 10 5 kg (100 tons) that can reach speeds of near 1000 km/s such systems can be propelled to speeds currently unimaginable with our existing propulsion technologies. To do so requires a fundamental change in our thinking of both propulsion and in many cases what a spacecraft is. In addition to larger spacecraft, some capable of transporting humans, we consider functional spacecraft on a wafer, including integrated optical communications, optical systems and sensors combined with directed energy propulsion. Since " at home " the costs can be amortized over a very large number of missions. The human factor of exploring the nearest stars and exo-planets would be a profound voyage for humanity, one whose non-scientific implications would be enormous. It is time to begin this inevitable journey beyond our home. Introduction We propose a system that will allow us to take the step to interstellar exploration using directed energy propulsion combined with miniature probes including some where we would put an entire spacecraft on a wafer to achieve relativistic flight and allow us to reach nearby stars in a human lifetime. With recent work on wafer scale photonics and directed energy, we can now envision combining these technologies to allow for a realistic approach of sending probes far outside our solar system and to nearby stars. By leaving the main propulsion system back in Earth orbit (or nearby) and propelling wafer scale highly integrated spacecraft that include cameras, bi-directional optical communications, power and other sensors we can achieve gram scale systems coupled with small laser driven sails to

We report on laboratory studies of the effectiveness of directed energy planetary defense as a pa... more We report on laboratory studies of the effectiveness of directed energy planetary defense as a part of the DE-STAR (Directed Energy System for Targeting of Asteroids and exploRation) program. DE-STAR [1][5][6] and DE-STARLITE [2][5][6] are directed energy "stand-off" and "stand-on" programs, respectively. These systems consist of a modular array of kilowatt-class lasers powered by photovoltaics, and are capable of heating a spot on the surface of an asteroid to the point of vaporization. Mass ejection, as a plume of evaporated material, creates a reactionary thrust capable of diverting the asteroid’s orbit. In a series of papers, we have developed a theoretical basis and described numerical simulations for determining the thrust produced by material evaporating from the surface of an asteroid [1][2][3][4][5][6]. In the DE-STAR concept, the asteroid itself is used as the deflection "propellant". This study presents results of experiments designed to measure the thrust created by evaporation from a laser directed energy spot. We constructed a vacuum chamber to simulate space conditions, and installed a torsion balance that holds an "asteroid" sample. The sample is illuminated with a fiber array laser with flux levels up to 60 MW/m2 which allows us to simulate a mission level flux but on a small scale. We use a separate laser as well as a position sensitive centroid detector to readout the angular motion of the torsion balance and can thus determine the thrust. We compare the measured thrust to the models. Our theoretical models indicate a coupling coefficient well in excess of 100 µN/Woptical, though we assume a more conservative value of 80 µN/Woptical and then degrade this with an optical "encircled energy" efficiency of 0.75 to 60 µN/Woptical in our deflection modeling. Our measurements discussed here yield about 45 µN/Wabsorbed as a reasonable lower limit to the thrust per optical watt absorbed.

Nanophotonics and Macrophotonics for Space Environments IX, 2015

Nanophotonics and Macrophotonics for Space Environments VIII, 2014

Nanophotonics and Macrophotonics for Space Environments IX, 2015

Nanophotonics and Macrophotonics for Space Environments IX, 2015

Nanophotonics and Macrophotonics for Space Environments VIII, 2014

Nanophotonics and Macrophotonics for Space Environments VIII, 2014

Recently, there has been a dramatic change in the way space missions are viewed. Large spacecraft... more Recently, there has been a dramatic change in the way space missions are viewed. Large spacecraft with massive propellant-filled launch stages have dominated the space industry since the 1960’s, but low-mass CubeSats and low-cost rockets have enabled a new approach to space exploration. In recent work, we have built upon the idea of extremely low mass (sub 1 kg), propellant-less spacecraft that are accelerated by photon propulsion from dedicated directed-energy facilities. Advanced photonics on a chip with hybridized electronics can be used to implement a laser-based communication system on board a sub 1U spacecraft that we call a WaferSat. WaferSat spacecraft are equipped with reflective sails suitable for propulsion by directed-energy beams. This low-mass spacecraft design does not require onboard propellant, creating significant new opportunities for deep space exploration at a very low cost. In this paper, we describe the design of a prototype WaferSat spacecraft, constructed on...

In the nearly 60 years of spaceflight we have accomplished wonderful feats of exploration and sho... more In the nearly 60 years of spaceflight we have accomplished wonderful feats of exploration and shown the incredible spirit of the human drive to explore and understand our universe. Yet in those 60 years we have barely left our solar system with the Voyager 1 spacecraft launched in 1977 finally leaving the solar system after 37 years of flight at a speed of 17 km/s or less than 0.006% the speed of light. As remarkable as this is, we will never reach even the nearest stars with our current propulsion technology in even 10 millennium. We have to radically rethink our strategy or give up our dreams of reaching the stars, or wait for technology that does not exist. While we all dream of human spaceflight to the stars in a way romanticized in books and movies, it is not within our power to do so, nor it is clear that this is the path we should choose. We posit a technological path forward, that while not simple; it is within our technological reach. We propose a roadmap to a program that will lead to sending relativistic probes to the nearest stars and will open up a vast array of possibilities of flight both within our solar system and far beyond. Spacecraft from gram level complete spacecraft on a wafer (" wafer sats ") that reach more than ¼ c and reach the nearest star in 15 years to spacecraft with masses more than 10 5 kg (100 tons) that can reach speeds of near 1000 km/s such systems can be propelled to speeds currently unimaginable with our existing propulsion technologies. To do so requires a fundamental change in our thinking of both propulsion and in many cases what a spacecraft is. In addition to larger spacecraft, some capable of transporting humans, we consider functional spacecraft on a wafer, including integrated optical communications, optical systems and sensors combined with directed energy propulsion. Since " at home " the costs can be amortized over a very large number of missions. The human factor of exploring the nearest stars and exo-planets would be a profound voyage for humanity, one whose non-scientific implications would be enormous. It is time to begin this inevitable journey beyond our home. Introduction We propose a system that will allow us to take the step to interstellar exploration using directed energy propulsion combined with miniature probes including some where we would put an entire spacecraft on a wafer to achieve relativistic flight and allow us to reach nearby stars in a human lifetime. With recent work on wafer scale photonics and directed energy, we can now envision combining these technologies to allow for a realistic approach of sending probes far outside our solar system and to nearby stars. By leaving the main propulsion system back in Earth orbit (or nearby) and propelling wafer scale highly integrated spacecraft that include cameras, bi-directional optical communications, power and other sensors we can achieve gram scale systems coupled with small laser driven sails to

We report on laboratory studies of the effectiveness of directed energy planetary defense as a pa... more We report on laboratory studies of the effectiveness of directed energy planetary defense as a part of the DE-STAR (Directed Energy System for Targeting of Asteroids and exploRation) program. DE-STAR [1][5][6] and DE-STARLITE [2][5][6] are directed energy "stand-off" and "stand-on" programs, respectively. These systems consist of a modular array of kilowatt-class lasers powered by photovoltaics, and are capable of heating a spot on the surface of an asteroid to the point of vaporization. Mass ejection, as a plume of evaporated material, creates a reactionary thrust capable of diverting the asteroid’s orbit. In a series of papers, we have developed a theoretical basis and described numerical simulations for determining the thrust produced by material evaporating from the surface of an asteroid [1][2][3][4][5][6]. In the DE-STAR concept, the asteroid itself is used as the deflection "propellant". This study presents results of experiments designed to measure the thrust created by evaporation from a laser directed energy spot. We constructed a vacuum chamber to simulate space conditions, and installed a torsion balance that holds an "asteroid" sample. The sample is illuminated with a fiber array laser with flux levels up to 60 MW/m2 which allows us to simulate a mission level flux but on a small scale. We use a separate laser as well as a position sensitive centroid detector to readout the angular motion of the torsion balance and can thus determine the thrust. We compare the measured thrust to the models. Our theoretical models indicate a coupling coefficient well in excess of 100 µN/Woptical, though we assume a more conservative value of 80 µN/Woptical and then degrade this with an optical "encircled energy" efficiency of 0.75 to 60 µN/Woptical in our deflection modeling. Our measurements discussed here yield about 45 µN/Wabsorbed as a reasonable lower limit to the thrust per optical watt absorbed.

Nanophotonics and Macrophotonics for Space Environments IX, 2015

Nanophotonics and Macrophotonics for Space Environments VIII, 2014

Nanophotonics and Macrophotonics for Space Environments IX, 2015

Nanophotonics and Macrophotonics for Space Environments IX, 2015

Nanophotonics and Macrophotonics for Space Environments VIII, 2014

Nanophotonics and Macrophotonics for Space Environments VIII, 2014