Jeff Greason describes how to go from 2% of lightspeed using dynamic solar wind soaring and then using pellets propelled from the sun to go from 2-6% of lightspeed using existing near term technology. At 6% of lightspeed the particles in the interstellar medium interact with the spacecraft like beyond nuclear fusion level energy. The high intensity energy is taken and used to power propulsion to reach 25% of lightspeed. The plasma magnet used during the solar wind dynamic soaring phase is used to brake at the target star.
These are clever ways to take relatively near-term technologies to reach 25% of lightspeed with probes and possibly even manned spacecraft. The methods to get to 2% of lightspeed over 2 years are all that are needed for travel within the solar system and even out to the gravitational lens points starting about a dozen times further than Pluto. Going to the gravitational lens areas let a small telescope use the Sun as a lens to become 10 billions time more powerful. We can pre-explore all of the solar systems within 1000s of light years with millions of space telescopes. We then choose to send actual probes to the best solar systems which we will have already started exploring with observatories sent to viewing points 3 light days around the Sun.
Gaining the kinetic energy required for interstellar flight affordably is difficult and tapping existing natural sources of energy such as the solar wind is attractive for reducing costs. However, a gap exists in the published concepts, in that solar wind speeds are limited to ~700 km/s, while even with concepts such as the wind-powered reaction drive (‘q’-drive), speeds of ~5% of c must be reached before they can take over. A cost effective way to fill that gap has been lacking.
Aerographite puffballs can be released near the sun and they will accelerate to about 5% of light speed. Aerographite is ultra-thin foam and are 15,000 times lighter than aluminum.
Objective – Demonstrate a method by which inert pellets, accelerated by the solar wind, can be used to accelerate a spacecraft from solar wind speeds up to ~5% of c.
Methods: Classical physics computations to support the basic physics and feasibility of the approach.
Results: When two matter streams are in proximity but with different velocities, or when they move through the same space but with different velocities and distinguishable properties, the difference in velocities, or velocity shear, can be used to gain propulsive energy. A stream of pellets moving through the interstellar medium is an example of such a case. Propulsion by pellets is an idea explored in the prior art that requires high speed pellets; the extraction of useful work from the difference in speed between the pellets and the interstellar medium allows a ship running over the pellets and also drawing energy from the passage through the interstellar medium to gain propulsive energy even when faster than the pellets and even when the pellets are composed of inert reaction mass. The basic physics of this is discussed and the performance equations and discuss this in the context of using relatively slow pellets (accelerated by solar wind), to send a spacecraft to a substantial multiple over the solar wind velocity. Another case where small macroparticles and a plasma wind are at different speeds is the inner solar system in the plane of the ecliptic, where the solar wind and zodiacal dust have different velocity distributions; this may offer further applications of the same principle.
Arxiv – Low-cost precursor of an interstellar mission
The solar photon pressure provides a viable source of thrust for spacecraft in the solar system. Theoretically it could also enable interstellar missions, but an extremely small mass per cross section area is required to overcome the solar gravity. We identify aerographite, a synthetic carbon-based foam with a density of 0.18 kg m−3 (15,000 times more lightweight than aluminum) as a versatile material for highly efficient propulsion with sunlight. A hollow aerographite sphere with a shell thickness shl = 1 mm could go interstellar upon submission to solar radiation in interplanetary space. Upon launch at 1 AU from the Sun, an aerographite shell with shl = 0.5 mm arrives at the orbit of Mars in 60 d and at Pluto’s orbit in 4.3 yr. Release of an aerographite hollow sphere, whose shell is 1 µm thick, at 0.04 AU (the closest approach of the Parker Solar Probe) results in an escape speed of nearly 6900 km s−1 and 185 yr of travel to the distance of our nearest star, Proxima Centauri. The infrared signature of a meter-sized aerographite sail could be observed with JWST up to 2 AU from the Sun, beyond the orbit of Mars. An aerographite hollow sphere, whose shell is 100 µm thick, of 1 m (5 m) radius weighs 230 mg (5.7 g) and has a 2.2 g (55 g) mass margin to allow interstellar escape. The payload margin is ten times the mass of the spacecraft, whereas the payload on chemical interstellar rockets is typically a thousandth of the weight of the rocket. Using 1 g (10 g) of this margin (e.g., for miniature communication technology with Earth), it would reach the orbit of Pluto 4.7 yr (2.8 yr) after interplanetary launch at 1 AU. Simplistic communication would enable studies of the interplanetary medium and a search for the suspected Planet Nine, and would serve as a precursor mission to αCentauri. We estimate prototype developments costs of 1 million USD, a price of 1000 USD per sail, and a total of < 10 million USD including launch for a piggyback concept with an interplanetary mission.
A technology developed under NASA Institute for Advanced Concepts (NIAC) sponsorship, the Plasma Magnet, offers a path to high-acceleration maneuvers in the solar wind, including fast transits to outer planets and to the Solar Gravitational Lens.
The AIAA Nuclear and Future Flight Propulsion Technical Committee has sponsored a conceptual design study of a demonstrator mission, JOVE. If flown, JOVE would provide the critical flight demonstration of this technology. The solar-powered spacecraft would weigh approximately 25 kilograms and would get to Jupiter in three weeks reaching an astounding 300 kilometers per second. Mr. Greason went over the key design challenges uncovered during the conceptual design, reviewed the current state, and discussed possible next steps.
Jeff Greason is an entrepreneur and innovator with 25 years of experience in the commercial space industry. He is the Chief Technologist of Electric Sky, developing long-range wireless power for propulsion and other purposes; and Chairman of the Tau Zero Foundation, developing advanced propulsion technologies for solar system and interstellar missions. He has been active in the development of commercial space regulation and served on the Presidential Augustine Commission in 2009. Jeff was a co-founder of XCOR Aerospace and served as CEO from 1999 to early 2015. Previously, he was the rocket engine team lead at Rotary Rocket and an engineering manager in chip technology development at Intel. He holds 28 U.S. patents and has recently published papers on novel space propulsion concepts. He is also a Governor of the National Space Society.
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
Known for identifying cutting edge technologies, he is currently a Co-Founder of a startup and fundraiser for high potential early-stage companies. He is the Head of Research for Allocations for deep technology investments and an Angel Investor at Space Angels.
A frequent speaker at corporations, he has been a TEDx speaker, a Singularity University speaker and guest at numerous interviews for radio and podcasts. He is open to public speaking and advising engagements.