China Proposes Magnetic Launch System for Sending Resources Back to Earth

Distance Between the Earth and Moon
The Earth rising over the Moon's surface, as seen by the Apollo 8 mission. Credit: NASA

In his famous novel The Moon is a Harsh Mistress, Robert A. Heinlein describes a future lunar settlement where future lunar residents (“Loonies”) send payloads of wheat and water ice to Earth using an electromagnetic catapult. In this story, a group of Loonies conspire to take control of this catapult and threaten to “throw rocks at Earth” unless they recognize Luna as an independent world. Interestingly enough, scientists have explored this concept for decades as a means of transferring lunar resources to Earth someday.

Given that space agencies are planning on sending missions to the Moon to create permanent infrastructure, there is renewed interest in this concept. In a recent paper, a team of scientists from China’s Shanghai Institute of Satellite Engineering (SAST) detailed how a magnetic launcher on the lunar surface could provide a cost-effective means of sending resources back to Earth. This proposal could become part of China’s long-term vision for a lunar settlement known as the International Lunar Research Station (ILRS) – a joint project they are pursuing with the Russian space agency (Roscosmos).

Continue reading “China Proposes Magnetic Launch System for Sending Resources Back to Earth”

Magnetic Levitation

[/caption]Overcoming the pull of gravity and fighting acceleration are major challenges for scientists looking to achieve flight and/or high-speed transportation. One way that they overcome this is the modern and growing technology known as Magnetic Levitation. Relying on rare earth magnets, superconductors, electromagnets and diamagnets, magnetic levitation is now used for maglev trains, magnetic bearings and for product display purposes. Today, maglev transportation is one of the fastest growing means of transportation in industrialized countries. This method has the potential to be faster, quieter and smoother than wheeled mass transit systems and the power needed for levitation is usually not a particularly large percentage of the overall consumption; most of it being used to overcome air drag. In William Gibson’s novel Spook Country, maglev technology was also featured in the form of a “maglev bed”, a bed which used magnets to stay suspended in midair.

Magnetic levitation (aka. maglev or magnetic suspension) is the method by which an object is suspended with no support other than magnetic fields. According to Earnshaw’s theorem (a theory which is usually referenced to magnetic fields), it is impossible to stably levitate against gravity relying solely on static ferromagnetism. However, maglev technology overcomes this through a number of means. These include, but are not limited to, mechanical constraint (or pseudo-levitation), diamagnetism levitation, superconductors, rotational stabilization, servomechanisms, induced currents and strong focusing.

Pseudo-levitation relies on two magnets that are mechanically arranged to repel each other strongly, or are attracted but constrained from touching by a tensile member, such as a string or cable. Another example is the Zippe-type centrifuge where a cylinder is suspended under an attractive magnet, and stabilized by a needle beading from below. Diamagnetic levitation occurs when diamagnetic material is placed in close proximity to material that produces a magnetic field, thus repelling the diamagnetic material. Superconductor-levitation is achieved much the same way, superconductors being a perfect diamagne. Due to the Meissner effect, superconductors also have the property of having completely expelled their magnetic fields, allowing for further stability.

The first commercial maglev people mover was simply called “MAGLEV” and officially opened in 1984 near Birmingham, England. It operated on an elevated 600-metre (2,000 ft) section of monorail track between Birmingham International Airport and Birmingham International railway station, running at speeds up to 42 km/h (26 mph). Perhaps the most well-known implementation of high-speed maglev technology currently in operation is the Shanghai Maglev Train, a working model of the German-built Transrapid train that transports people 30 km (19 mi) to the airport in just 7 minutes 20 seconds, achieving a top speed of 431 km/h and averaging 250 km/h.

We have written many articles about magnetic levitation for Universe Today. Here’s an article about the uses of electromagnets, and here’s an article about how magnets work.

If you’d like more info on the magnetic levitation, check out these articles from How Stuff Works and Hyperphysics.

We’ve also recorded an entire episode of Astronomy Cast all about Magnetism. Listen here, Episode 42: Magnetism Everywhere.

Sources:
http://en.wikipedia.org/wiki/Magnetic_levitation
http://hyperphysics.phy-astr.gsu.edu/hbase/solids/maglev.html
http://www.rare-earth-magnets.com/t-magnetic-levitation.aspx
http://en.wikipedia.org/wiki/Earnshaw%27s_theorem
http://en.wikipedia.org/wiki/Maglev_train
http://en.wikipedia.org/wiki/Meissner_effect