Project Elara Safety Review and Precautions

At Project Elara, we want to develop technologies that people can trust. This page covers a review of the safety of Project Elara’s technologies and discusses what precautions we must take to ensure that our technology is as safe as possible.

Preface

When new technologies are introduced, we have seen time and time again that the innovator(s) involved often pursue progress recklessly, at the expense of the safety of the general public. Our technology involves microwave beaming, a potential major safety hazard, as well as many other safety risks such as the possibility of substantial space debris, hazardous materials in rocket launch fuels, pollutants in the manufacturing of the system, etc.

It is important to not dismiss the risks entirely, since space-based solar power is a technology that carries inherent risks. When we think about safety, our first response should not be “the technology is perfectly safe”; rather, it should be “there are risks involved, but we have prepared a substantial set of safety measures to ensure that it is as safe as possible”.

A good example of this strategy in action is with airplanes. Large passenger aircraft pose substantial inherent risks over, say, a car; no matter what, you cannot dismiss the fact that aircraft today can fly close to the speed of sound, often weigh over 100 tons, and can carry over ten times the number of passengers in a typical SUV. These are all characteristics that make them inherently dangerous.

But in general, air travel is much, much safer than car travel. Why? Because aircraft are equipped with advanced safety measures dedicated to ensuring safety, including redundancy of all key aircraft systems, fail-safes, and extensive training for pilots. Remember, dangerous does not mean the same thing as unsafe. Dangers can be mitigated with safety measures and a strong safety-oriented culture, but something that is unsafe is unacceptable.

The safety risks of our technology cannot and must not be dismissed. We will take every effort to consider as many safety risks as possible and investigate each of them as thoroughly as possible. It is also essential that we do declare a conflict of interest in evaluating our own technology’s safety in our papers, and look into the literature carefully. Not all of these measures can immediately be implemented due to the small size of our team at present and our limited resources. However, they are principles we must keep in mind going forwards.

Possible dangers

Unlike electron beams, microwaves are not ionizing radiation, so they do not have the radiation hazard associated with ionizing light sources (like X-ray and UV lasers). The dangers posed by microwave beams can be divided into two main types:

• Thermal effects, which come from heating caused by microwaves, and are the predominant danger of microwave beams
• Non-thermal effects, which can be further divided between (a) electromagnetic interference with electronics and (b) biological effects of microwaves, both on humans and other organisms

High-energy microwave beams can lead to serious burns due to the dielectric heating they cause. This comes from the interaction of the rapidly-oscillating electric fields of these microwaves with polar molecules, causing the molecules to rapidly

• Microwave exposure
  • Dielectric heating of air
  • Dangerous power densities in beam, see https://www.laserax.com/blog/laser-safety-laser-classes-explained
• Electron gun dangers (need for vacuum pump, ionizing radiation from electron gun if not properly controlled, incredibly hot thermocathode that can cause a fire by heating up the surrounding air to hundreds of degrees up to the autoignition temperatures of materials in the laser/room)
• Undulator dangers (strong magnetic fields)
• Solar mirror dangers (highly-concentrated and possibly blinding sunlight)
• Possibly-toxic materials in spacecraft/launch vehicle

For modelling the atmospheric heating of the microwaves we start from the PDE first described in Thermocathode design for electron gun:

$${\nabla }^{2}T=-\frac{1}{k}\left[\sigma |\mathbf{E}{|}^2-\mu (T^4-v^4)\right]$$

We assume for now that we are analyzing a cubic volume of air with volume $V$ that is homogeneous. Numerically, we can solve for more complicated atmospheric conditions, but we will start with this to find an analytical baseline solution.

Safety mechanisms

Safety must come built-in with fail-safes especially essential.

Power beaming control

It is necessary to recognize that not all locations need to receive the same amount of power. Recall that the power density (intensity) is given by $I=P/A$, where $P$ is the power transmitted and $A$ is the cross-sectional area upon which the beam is incident. If we want to beam to smaller dishes, for the power density to still be safe, we will need to reduce the power. For this, we may simply dial down the power in the appropriate beams.

Note: we plan for several types of receiver designs:

• Massive circular receivers several kilometers in size, covered in rectennas:
  • Ocean-based receivers several kilometers in size, which are based off old oil rigs and can supply huge amounts of electricity that can power entire countries
  • Land-based receiver stations, which can be smaller (and as a result, only capture a part of the beam), but still be effective at distributing power to local communities
• Medium-sized receivers (around the order of a few dozen meters):
  • Shipborne receivers (both powered ships and unpowered barges) that can dock to quickly deploy energy to coastal cities
  • Ground-based receivers of similar scale, which can power e.g. an apartment block and can be placed at the top of the apartment
  • Converted telecommunications towers/radar towers that have their radio dishes modified to support power receiving
• Small, air-droppable & helicopter-towable receivers (a few meters to maybe 10 meters max)
  • Printed rectenna “sheets” that can be quickly deployed to disaster zones and rural sites
• Power transmitter towers (may not be necessary?) to be able to transmit power from the largest receivers to other regions that can’t host massive receivers
  • Skyscraper-sized power towers that have high-mounted receiver dishes which have secondary power beams (phased array or parabolic antennas) to beam power to areas further away (up to around 100km)
  • Mountain-based “beacons” that transmit power wirelessly from one mountain-top to another, crossing over high mountain ranges and reaching areas that would be otherwise inaccessible
  • Power beam “cables” that basically are microwave waveguides so that the power beam received from very large receiver stations (especially the ones at sea/on the coast) can be channeled to distant locations, where a secondary antenna converts the microwave beam to electricity

Fail-safes