LORENTZ PROPULSION MICROPROBES


A proposed design for the chip microprobes. Image copyright Popular Science.

Lorentz Propulsion Microprobes
Tech Level: 12
Interstellar Lorentz Microprobes
Tech Level: 14

In a number of articles these devices are more commonly referred to as space chips or chip probes.


LORENTZ PROPULSION MICROPROBES
Tech level: 12

To date, most deep-space exploration probes have been inordinately expensive things. The cheapest of them cost over a hundred million dollars, not even including launch costs.

However, a proposal by Mason Peck, an associate professor of mechanical and aerospace engineering at Cornell University in New York, postulates a way to make the probes dirt cheap and to send them swarming through the solar system and beyond thousands strong. The idea is to create microchip-sized probes and to use the Earth’s electromagnetic field to fling them to other planets.

These chip probes would be tiny enough that twenty five of them would be able to fit on a standard postage stamp. They would consist on one side of a shielded microprocessor, solar cells to keep the unit charged, very tiny thrusters, a small deployable boom antenna, and an anchored monofilament wire for use in Lorentz force propulsion. The other side would contain one of a potential variety of microsensors. One chip probe may have a sensor for water, another for ammonia, another for methane, yet others for temperature, amount of light, acidity and so on. At Tech Level 12, when these devices are expected to become practical enough to produce in quantity, a rudimentary video camera could even be etched on the chip in place of a sensor, though these may require slightly larger chips to handle the increased processing and transmission ability required.

The microprobes are intended to be deployed in groups of hundreds or thousands with a dozen or more types of sensors spread between them. Groups of only one type of sensor (like those looking for chemical signs of life) are possible as well. In any one swarm, a certain percentage loss of the probes, due to collision, systems failure, radiation damage, etc., is expected, but would usually not be enough to deter the mission.

Because of their limited transmission power and capabilities, the chips would send out a single bit stream with its ID (or just its type of sensor) and if it found anything (basically a ‘yes’ or ‘no’ response.) These could be picked up by receivers on Earth or in Earth orbit. If a larger satellite is in orbit around the target body, the signal positions can be triangulated to help give researchers a better visualization tool of possible conditions or compositions of different regions.

Peck also intends for his microchip probes to be launched to their destination using Lorentz force propulsion. The Lorentz force is the phenomenon of a charged particle or object moving at an angle perpendicular to the magnetic lines of force and the direction of current flow. It is one of the main physical phenomena that make technologies such as particle accelerators possible. The push from the Lorentz force is usually slight at any one moment relative to the total strength of the magnetic field, but can build up to quite a significant source of acceleration over time.

When these probes would be released into orbit from a conventional rocket, they would unspool a micro-thin filament that would carry an electrical charge. Depending on the exact design, this monofilament wire could be up to a kilometer long. The filament would play against Earth’s electromagnetic field, the Lorentz force very gradually accelerating the filament and attached chip probe. After about a year of continually being nudged, enough energy would have been imparted to the chip to fling it free from Earth’s gravity. If the original orbital insertion was calculated precisely, the chip would soon be coasting to its destination. Trip times could be several months o reach nearby asteroids, about two to four years to reach the Jupiter and its moons, and for a decade or more to reach more remote targets. The tiny thrusters the chips carry can perform some limited course corrections along thew way if needed.

Peck has been quoted as specifically mentioning Jupiter’s moon Europa as a specific target, and to use the microprobes to check worldlet for signs of native life. However, the chip probes can be used to investigate any body in the Solar System.

Once they arrive at a world, their small size would allow most to survive re-entry and impact with the surface of most bodies intact. Once actually on the ground, their chemical sensors could go to work.

Actual size of the proposed microprobes. It takes five
to equal the length of a standard US postage stamp.

INTERSTELLAR LORENTZ MICROPROBES
Tech Level: 14

While Earth’s magnetic field is sufficiently powerful for flinging chip probes throughout the solar system, sending them further—potentially even to other stars—would require much more powerful magnetic fields.

Jupiter’s rapidly spinning magnetic field could deliver 20,000 times the Lorentz force push that Earth’s field. Chip microprobes inserted into the field would be theoretically able to eventually accelerate to a few percentage points of light speed before leaving the gas giant’s field, perhaps even more if the chips get a gravity assists from Jupiter, its moons, or other planets on its flight trajectory.

At these speeds, the microprobes would still take well over a century to reach even the nearest stars. However, they would still be much cheaper than almost any alternative type of flyby probe, and would be able to target many more nearby stars than most other interstellar probe schemes for comparably the same price.

Because of the long flight times and much heavier exposure to radiation in space, the interstellar versions of the chip microprobes would be built a bit bigger and more robust to better withstand the harsh conditions of interstellar travel, say about a centimeter square. Also, because precision targeting of the destination may be much harder to accomplish, the microprobes may be sent out in swarms numbering hundreds of thousands or even millions to offset potential losses from malfunctions or chips thrown off course.


FURTHER INFORMATION

http://www.popsci.com/military-aviation-space/article/2007-08/mmmm-space-chips

http://www.airspacemag.com/space-exploration/FEATURE-Starchip.html

Lorentz Force

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfor.html

http://www.magnet.fsu.edu/education/tutorials/java/lorentzforce/index.html


Article added 11 December 2010

HOME DEEP SPACE PROPULSION HUB INTERSTELLAR FLIGHT HUB