Wireless Mesh for Earth to Space
First check out the Nova video on this solution. You can see the competition for building a space elevator prototype is getting narrow and competitor are being lead by a bunch of kids out of the University of Saskatchewan. The whole concept is a ribbon made out of carbon tubes are sent from a satellite orbiting, and a free electron laser is pointed at this solar collector that provides the power to run an electric motor up this ribbon of carbon tube toward the satellite, hence Arthur C. Scott’s vision of space elevator. The fun part is that the people that are competiting are gaining great knowledge in developing this technology and are becoming the experts. This is a great idea.
But what got me excited and thinking was the laser power, solar collectors system that they would use to propel the craft. It used a laser beam that focuses its energy onto the solar panels. The panels would convert the light to electricity and system would not need any batteries. If you have seen my solar panel experiments running a wireless mesh node you can see where I’m going with this. Well basically a wireless mesh node that is power by laser. But my thinking took me a step further the laser would also be used to provide communication. The laser would be equipped with Free Space Optics (FSO.) So it would not only provide the energy through a narrow beam of light it also would provide gigabits of bandwidth communication, such that point to point. It is similar to Ethernet over Power line, where Ethernet signal is used in conjunction with the power line to provide both power and communication but without any infrastructure between the two devices.
But we have seen with laser in the past that when they are used for communication such as Free Space Optics that they are susceptible due to weather conditions. For terrestrial applications, the principal limiting factors are:
- Beam dispersion
- Atmospheric absorption
- Fog (10..~100 dB/km attenuation)
- Background light
- Pointing stability in wind
- Pollution / smog
If the sun goes exactly behind the transmitter, it can swamp the signal.
These factors cause an attenuated receiver signal and lead to higher bit error ratio (BER). To overcome these issues, vendors found some solutions, like multi-beam or multi-path architectures, which use more than one sender and more than one receiver. Some state-of-the-art devices also have larger fade margin (extra power, reserved for rain, smog, fog). To keep an eye-safe environment, good FSO systems have a limited laser power density and support laser classes 1 or 1M. Atmospheric and fog attenuation, which are exponential in nature, limit practical range of FSO devices to several kilometres; but and this is a big but, the space elevator to get around this problem will utilize a free electron laser. Now doing some research on this the laser would be targeting a single object that is moving in a straight line. Tracking this objects and keeping the solar panel align with the beam has already been invented.
Wow you can theoretically use this laser through any of the terrestrial conditions fore mentioned. This has already been examined NASA-DOE reference design of the ‘70s Koomanoff and Bloomquist, 1998. I think it was referred to PV-driven cloud-penetrating microwave beamers. Now this is what I talking about, laser that can penetrate terrestrial conditions. FSO commercial applications are focused on providing the most inexpensive product that they can. They should have been focus on producing the best quality product and to me quality is PV-driven cloud-penetrating microwave beamers (CPMB.) Imagine using these technologies together call it Ethernet over Laser (EoL.)
We implement wireless mesh using 802.11b in the past it follows a typical wireless distribution; however, having the ability to interconnect nodes that are in range. The uplink nodes or nodes that connected to internet or internet backbone provide initial protocols so that mesh nodes can communicate with each other and thus providing framework to create a mesh cloud. Now substituting the uplink Ethernet with FSO utilizing CPMB may provide the infrastructure not only provides backbone but the energy to run the mesh node. It could also be the communication device that the space elevator may use. Or it can give the wireless mesh the ability to go to a low orbit satellite power by upward facing CPMB.
Distributing the CPMB to other nodes would be difficult because today’s solar panels are not that efficient. This would be similar to an electric car driving down the high way having an electric turbine generating its electricity. Eventually the car will stop. I’m thinking that each step of the CPMB would have a power loss say “efficiency of the initial solar panel – the power that it would run the mesh node – Transmitter laser going to the next node or back to the original node.” Yeah, a lot of loss but depending on the solar collectors it may have enough power to distribute to two other mesh nodes. If efficiency of the solar collectors can be increase and the redistribution of the excess laser beam can be tapped and redirected to other nodes. A viable solution can be made for communication.
If this solution can be made for communication it can be made for other solutions. The University of Michigan has broken a record with a 1.3-micron speck wide laser. Weighing in at a mere 20 billion trillion watts per square centimeter and containing a measly 300 terawatts of power, It’s about two orders of magnitude higher than any other laser in the world and can perform for 30 femtoseconds once every ten seconds— some of the researchers speculate it is the most powerful laser in the universe. Can you imagine if this thing could run continuously it would be able to power everything?
This technology could be that turn point that we have all been looking for a laser that could power your home, your transportation and provide you with communications. But lets take these baby steps first; the future is bright. I will be watching the space elevator competition. It has the components of changing the world. Who would of thought that space elevator competition could be the catalyst in identify new technology that could provide communication and power through a beam of light.