A new level of urgency for space-based solar power
by Nathan Kitzke
|One could imagine satellites powering forward operating bases (FOBs) or overseas bases for US joint military operations in both permissive and non-permissive environments.|
But do not let today’s low gas prices fool you. The US Energy Information Administration projects the global oil market to balance in 2017, as global demand for oil will continue to grow at an average rate of 1.7 million barrels per day. As the Earth’s growing population gains access to electricity and demand for energy increases, the appetite for fossil fuels will maintain its steady climb and cost will rise with limited availability. For example, the Middle East now uses nearly 33 percent of the oil that it produces, compared to just 20 percent in 2000.5 With the largest reserves in the world equaling 25 percent of the global total, the world still continues to rely on the Middle East to supply its petroleum demands in the foreseeable future. At the current rate of consumption, global supplies will only last another 36 years. 6
On his 2016 State of the Union address, President Obama called for increased investment into clean energy that would make American businesses a leader for selling the energy of the future. With growing global populations and a surging demand for energy, concerns regarding long-term accumulation of fossil fuel-derived greenhouse gases coupled with a decline in world fossil-fuel reserves over the next thirty-five years will dominate world interest.7 According to former NASA official John Mankins, the “green” technologies that President Obama speaks of like photovoltaic arrays, high energy and low mass fuel cells, and wind turbines have made substantial contributions to meeting long-term energy demands, but they are unlikely to provide the amounts of continuous base-load power that will be needed in the coming decades. Space-based solar power (SBSP) could provide virtually limitless energy from the sun in a safe and cost-effective manner. SBSP is the collection of energy from the Sun by space-based assets, and its wireless transmission from space to other space assets or to Earth.8 But as yet, the United States has no official SBSP program.
One could imagine satellites powering forward operating bases (FOBs) or overseas bases for US joint military operations in both permissive and non-permissive environments. One could also envision entire cities or regions completely fueled by limitless, affordable energy from space. Despite these possibilities, it is unlikely that Americans or others will notice the significant impact of this new technology over the next 10 years. The military, humanitarian, and infrastructure capabilities are beyond the imagination of most, but fortunately they are not beyond reality from a technical perspective.
The United States has demonstrated a history of innovation and leadership in aerospace development that began with the Wright Brothers and the establishment of the space program at NASA. As the world’s premier aerospace developer, the US is well positioned to lead the development of space-based solar power. Doing so could establish new industry for the US and decrease our military’s annual $20 billion energy bill.9
The urgency of this matter should drive Congress to require the Air Force Space Command to develop both laser and microwave wireless point transfer (WPT) SBSP. Laser SBSP should be considered because of the immediate impact that it can bring to space-based assets and potential for terrestrial military operations. By demonstrating laser SBSP capabilities, the US will ignite the appetite for microwave SBSP systems capable of significantly more power distribution tailored for permanent power grid infrastructure support. With current proposals provided by Lawrence Livermore National Laboratory (LLNL), laser SBSP could be implemented in five years. It is imperative that the US develop and collaborate new policies, both domestically and internationally, that support the demonstration of WPT SBSP not with the aim of weaponizing space, but to build a more prosperous world for future generations.
When developing a design for SBSP, four interrelated characteristics matter the most: the wavelength/frequency of the electromagnetic (EM) wave sued for transmission of the energy; the distance over which the energy is to be transmitted; the size of the transmitting aperture; and the size of the receiving aperture.10 The laser design uses a beam at visible or near-visible wavelengths, whereas the microwave design uses radio frequency (RF) energy transmitted at microwave wavelengths of about 2 to 20 centimeters.11 Each design has significant advantages and disadvantages.
|An initial laser-based system could be placed in low Earth orbit (LEO) with a single Falcon 9 launch, as compared to the multiple space launches and on-orbit robotics assembly required for a microwave-based system.|
As the wavelengths used in lasers are very small, on the order of hundreds of nanometers, you can achieve effective transmission of energy with small transmitting and receiving apertures. When it comes to lasers, distance is largely insignificant. At a geosynchronous orbit (GEO), a 3.65-meter-aperture laser is potentially capable of providing a spot on the Earth’s surface 36.5 feet across.12 That laser width, which impacts the size of the spot on Earth, can theoretically be adjusted by changing the size of the transmitting aperture. Lasers operate at frequencies multiple orders of magnitude higher than microwaves, and can result in the use of a smaller transmit aperture in space.
An initial laser-based system could be placed in low Earth orbit (LEO) with a single Falcon 9 launch, as compared to the multiple space launches and on-orbit robotics assembly required for a microwave-based system.13 After testing the system, a laser SBSP satellite would be deployable directly from Earth’s surface to GEO on just one Falcon Heavy rocket. In addition, the latest designs of laser SBSP have now made use of high efficiency components so that more of the Sun’s energy collected in space can be converted to energy transmitted to Earth. The extremely poor transfer efficiencies from solar energy to electric DC power have improved significantly in recent years to efficiencies greater than 50 percent.14
Lasers, though, produce a visible beam that cannot pass readily through haze or cloud cover, reducing its average efficiency of transmission and potentially necessitating the use of adaptive optics on the ground. Even with the improvement in efficiency, there will be a concern for heat buildup in the transfer of solar energy to laser energy because heat does not naturally dissipate in space. The satellite’s design must incorporate a cooling function utilizing radiation instead of conduction and convection,15 as heat buildup in a high power laser will be an issue and development of a good cooling system will be essential.
It will also be imperative no objects travel through the laser. With countless satellites between GEO and the Earth’s surface, a shutoff mechanism will be required to recognize beam interference from another space based system.16 User and pedestrian safety on the ground will be a significant concern. Laser transfer’s high visibility (you will easily able to see it, especially at night),will also be a potential concern if supporting covert military operations.
Microwave WPT SBSP, on the other hand, provides a steady, uninterrupted transmission of power through rain, clouds, and other atmospheric conditions, depending on the operational frequency chosen. It will safely transmit power through air at intensities no greater than the sun’s most intense rays. It will be capable of providing from one to tens of gigawatts of energy to terrestrial receivers, enough to power a large city.
|Laser SBSP could be deployed today to help build an energy infrastructure for increased space industrialization.|
The significant challenges of the microwave design stem from its relative size of a system compared to the laser SBSP design. This is primarily related to the fact that apertures for longer wavelengths are significantly larger than the equivalent apertures needed for operation at the wavelengths associated with lasers. The microwave design would therefore require multiple launches into space from earth. Further, due its size, it would require on orbit robotic assembly in GEO or assembly in LEO with a required space tug application to move it from LEO to GEO. Such a robotic on-orbit assembly capability will require significant technological development that may not be available yet. John Mankins estimates a six-year roadmap required to field and test his SPS-ALPHA design from an initial operating capability in LEO to a full operating capability in GEO.
LLNL has been developing a laser SBSP design since 2002 that today will only weigh roughly 10 metric tons, a fraction of the weight of the microwave design.17 Its researchers predict a cost of $500 million to create and deploy it into space with only one Falcon 9 rocket, which drastically reduces the cost and time of production. The laser beam would only be about two meters in diameter. The LLNL design utilizes microgravity to permit a low-mass, inflatable, non-rigid structure.18 This laser WPT design reduces the required size of the receiving aperture on Earth by more than a thousand times and relaxes the focusing requirements of the transmission system.
Diode-pumped, electrical lasers with efficiencies of more than 50 percent, with the ability to output many kilowatts of power, are commercially available now. Today, it would be quite possible to deploy the LLNL design on a Falcon Heavy and have a SBSP satellite ready for use. In order to justify its $500 million price tag, this essay will examine laser SBSP applications best suited for space-based and terrestrial military applications in future development. Successful demonstrations of the laser SBSP will help spark momentum for microwave designs, which have even bigger strategic impacts for future power application in a potentially resources constrained environment.
The latest designs of microwave SBSP feature more practical structures than in the past, which extended for kilometers and were estimated to cost somewhere between $1 and $3 trillion to create. John Mankins’ microwave design would use a terrestrial receiving aperture several kilometers in diameter, require fewer launches, and take advantage of today’s latest concepts in on-orbit servicing using robotics. Right now, he estimates a required cost for the project to be between $1 and $10 billion, a significant reduction in cost compared to past designs. The significant improvements in technology to field a SBSP system from the 1970s to right now demonstrate the potential for SBSP in the future.
From a more strategic outlook, the microwave design of SBSP provides tremendous potential for powering future societies on earth using a rectifying antenna referred to as a “rectenna.” The size of the rectenna would be equivalent to the size of a football field, receiving the SBSP microwave signal, and plugging into a power grid with appropriate DC-to-AC converters. With on-orbit construction requirements, microwave SBSP designs could utilize the energy provided from an already deployed laser SBSP satellite. Due to the lack of atmosphere and challenges seen with terrestrial type usages, the laser application of SBSP energy to space based operations promotes an environment of innovation and diffusion of perceived reality.
Laser SBSP could be deployed today to help build an energy infrastructure for increased space industrialization. The advantages of using the laser design would be tremendous for space assets. It would enable spacecraft using electric propulsion to carry out a mission with relatively little propellant.19 Royce Jones, CEO of Solar Maximum LLC, a company specializing in Concentrated Photovoltaic and Thermal (CPV-T) combined systems, proposes a hybrid space tug design that use both a 0.5-megawatt laser rectenna and a 0.25-megawatt on-board direct drive solar cell. He states that vehicles powered by lasers from SBSP systems would enable vehicles to reduce mass by a factor of twenty to thirty times than solar, chemical, or nuclear powered vehicles. The ability to beam energy to the space tug decreases mass because the energy production system would not be located in its design. This development could enable a low cost cislunar transportation system. Jones believes his hybrid space tug design could be used for a wide range of space mission types, including retiring communication satellites in GEO, moving cargo and people to space stations, cleaning up space debris, and conducting on-orbit assembly, something that could assist John Mankins’ SPS-ALPHA design in GEO.
Laser SBSP could support both missions that we are currently thinking of today and ones we are not.20 From an innovative perspective, a multi-megawatt or even gigawatt laser-powered space tug could one day outperform even chemical rockets in thrust.21 Developing a laser SBSP capability to test space tug operations could open the doors to further capabilities long desired by space advocates. Laser SBSP could be a game changer for building a transportation network and logistics infrastructure in space and potentially be that missing link that propels the human race into becoming a spacefaring society. A beamed energy in-space transportation system could be considered a precursor or even a technology demonstrator for SBSP terrestrial military functions.
Out of the $20 billion a year that the Defense Department spends on energy, roughly 35 percent of delivered fuel goes toward powering forward operating bases.2223 For the FOB, a SBSP satellite that produces one megawatt of power would support a maximum power output of 500 kilowatts assuming a wireless transfer efficiency of 50 percent.24 With the average person requiring 1.5 to 2 kilowatts of power, the maximum capacity utilizing the LLNL design would be around 250 service members. In this scenario, the laser rectenna receiving aperture would be situated a distance away from the tent site and operations area of the FOB.25 This is similar to today’s operations, which are conducted with portable ground generators rated at 40 to 60 kilowatts and use the same concept for both thermal and noise abatement issues.
|If the LLNL design is implemented, it could produce a laser SBSP satellite and deploy it on a Falcon Heavy to GEO for $135 million.|
Support would only include the necessary security perimeter and space-based asset de-confliction. A laser SBSP satellite could play a significant role in supporting such an operation in a combat environment with its inherent flexibility. Further, a laser SBSP satellite could power multiple FOBs, giving a backup power source when logistical lines run thin or there is a sudden increased demand for power.
When 100 airmen of Air Mobility Command’s Contingency Response Group (CRG) deploy to establish airfields in other parts of the world, they take four generators to power each location, three to power seven tents and one to power their operations structure. On a 45-day deployment, they will consume 250 liters of fuel and 30 liters of oil every eight hours for just these four generators. After 45 days, the organization will have consumed a total of 34,000 liters of fuel and about 4,000 liters of oil.26 Their initial capacity for deployment only allows them to carry about 3,800 liters of fuel. Depending on the mission, these warfighters could operate in permissive, semi-permissive, or even combat environments and experience situations where replenishables must be re-supplied, putting those that provide those supplies in in harm’s way.
According to Martin LaMonica of IEEE Spectrum, fuel can cost $2.64 to $3.96 per liter by the time fuel is delivered to outposts.27 After the initial five days and 3,800 liters of gasoline, the price to run the generators will jump from $36 an hour to $285 an hour just for diesel. At these prices, CRG operations for the next 40 days of deployment would cost $273,000 in just fuel costs alone. If the LLNL design is implemented, it could produce a laser SBSP satellite and deploy it on a Falcon Heavy to GEO for $135 million. It would take 12.5 generators to conservatively create the output of 500 kilowatts of energy. At a comparison cost of $4 a liter for fuel alone, it would take only 17 years of continuous 500 kilowatts of energy production to recoup the $135 million launch cost.
Fuel delivery convoys to deployed forces add cost to logistical chains and create targets for improvised explosive devices (IEDs). The flexibility provided by SBSP will reduce the frequency of logistical resupply for our joint warfighters and will lower Defense Department energy costs to sustain its expeditionary footprint over the long run. The ability to keep our soldiers, sailors, marines, and airmen out of harm’s way carries a lot of weight in supporting the idea of SBSP. Once the case for SBSP gains traction within the Defense Department, the significant gains of this new energy resource will be harnessed by powering joint military installations that exist in areas where energy is high cost.
The USAF has based outside the continental US, especially in the Pacific Command region, that present phenomenal cases for a microwave SBSP market, not just to provide electricity to the military but also for supporting the entire community. Kadena Air Force Base in Okinawa, Japan, has one of the most expensive power bills in the Defense Department. In 2013, the Government of Japan and the DoD together spent $65.21 million on the electric bill supporting Kadena AFB, with $30 million of it going toward base housing.28 A tremendous portion of the money budgeted for defense goes toward keeping the lights on in our buildings, infrastructure, and housing for our families. In 2015, Kadena AFB spent $50 million for 318 million kilowatt-hours at roughly $0.16 per kilowatt-hour—compared to the average price of $0.10 per kilowatt-hour in the US—after further improving initiatives to save energy on base and a favorable currency exchange rate.29
Over the past 15 years, US Pacific Command leaders have emphasized a growing concern for increasing energy costs within the AOR and a strategic vision of improved, affordable green energy development. With John Mankins’ SPS-ALPHA satellite design, the Air Force could provide energy not just to Kadena AFB but the entire island of Okinawa. According to the Okinawa Electric Power Company, the estimated population growth for the island in 2023 will increase energy demands to 8.156 billion kilowatt-hours per year.30 If the Air Force were to charge its airmen and the citizens of Okinawa just $0.10 a kilowatt-hour, decreasing the average Okinawan’s monthly electricity bills by 57 percent, it would generate $815 million in revenue and would pay off its $10 billion investment in less than 12 years.31
Instead of focusing on “power naps” every year in hopes of slightly lowering the Defense Department’s energy costs, the Air Force would further solidify its influence within the Pacific Command region. If the US government proves this concept in Okinawa, it could lead to further commercial developments in SBSP within the region. It may even improve American influence in the Pacific by starting a technology that provides clean, affordable energy for numerous US allies in the region. Kadena AFB could provide the benchmark for other bases in the Pacific to follow suit, like Joint Base Pearl Harbor-Hickam and Camp Smith in Hawaii.
At $0.32 per kilowatt-hour, Hawaii ranks number one in highest average energy costs in the United States.32 With the Defense Department responsible for 15 percent of the state’s energy consumption, the US Pacific Command commander directed an energy security strategy for the command’s entire region, focusing on improved energy security across the Pacific with the intent to free up resources for mission requirements.33 Its strategic goal was to match or exceed the state’s goals for harnessing clean, efficient, secure, and renewable energy. The strategy aimed to emphasize stability by designing new buildings with 30 percent less energy and decrease fossil fuel-generated energy consumption 65 percent by 2015 and 90 percent by 2025.
|By supplying SBSP in high-demand, high-energy-cost environments, the Defense Deparment can fulfill its growing energy requirement, better solidify a strategic expeditionary foothold in its overseas bases, and ignite a new energy resource to help bolster the US economy.|
In 2009, Pacific Command had a total of $1.42 billion in unfunded energy projects, including photovoltaic roofs, hangars, and carports; wave energy “powerbuoys”; range control wind/solar systems; smart metering; and biofuel electrical power plants. Per capita, Hawaii residents consume 57,740 kilowatt-hours per year.34 If a microwave SBSP satellite supplied every island with power at $0.10 per kilowatt-hour, it would generate $8.2 billion in revenue a year. Whether the Air Force developed a SBSP satellite to supply energy to Defense Department assets and the civilian state infrastructure in Hawaii, or a US company took out a $10 billion loan to launch a SPS-ALPHA, Hawaii exemplifies another tremendous market for microwave SBSP. Pacific Command should look to SBSP to meet its future energy goals.
Whether it’s powering small teams on remote operations or simply finding new power systems for in-garrison everyday infrastructure, SBSP represents a strategic move toward fulfilling a sustainable force. For the Defense Department, military infrastructure can become extremely costly at bases located in high-energy markets. By supplying SBSP in high-demand, high-energy-cost environments, the Defense Deparment can fulfill its growing energy requirement, better solidify a strategic expeditionary foothold in its overseas bases, and ignite a new energy resource to help bolster the US economy. The US should formulate a strategic vision that gives the Air Force the responsibility to develop laser SBSP as soon as possible and microwave SBSP on the six-year timeline presented by John Mankins.
SBSP is really just the first step in a transitional framework that will mark the progression of the human race to one that views space as truly the next, realistic frontier. SBSP has tremendous utility in supporting joint military operations both in forward operating bases and in overseas expeditionary basing. If developed, the potential to support military operations and commercial industrialization of space provide significant incentive for the US to develop this capability first and lead the rest of the world in tapping into this unlimited, clean supply of energy. When America leads all others in the race to provide solar power from space to planet Earth, it will strengthen its stance as a world leader.
This transition starts with a comprehensive policy that supports the establishment of laser and microwave SBSP. It will address the future budgetary and energy concerns of the Defense Department. It will revolutionize military operations, geopolitics, global warming, and competition for resources. It will prevent the depletion of natural resources on Earth and will enable the human race to continue to grow and prosper. Planning and executing a national US energy policy that undertakes the development of SBSP must become a priority for the executive and legislative branches of the US Government. SBSP will provide a lot of answers to the growing cost of energy in a resources scarce environment and will jumpstart America on the path to acquiring the mastery of the industrial space operations required to become a true spacefaring nation.