SPACE SOLAR POWER SATELLITES -------------------------- John Pazmino NYSkies Astronomy Inc www.nyskies.org email@example.com 2008 November 7 initial 2009 Septenber 6 currebt
Introduction ---------- One of the earlier potential applications of humankind's newfound ability to work in Earth orbit was the solar power satellite. In the mid 1960s, before the Apollo flights, a basic scenario was put out by several spacefaring agencies and advocates. There would be in geostationary orbit an immense field of solar panels to generate electric. The accompanying satellite wold convert the electric into a microwave beam to send to a receiving base on the ground. This receiving base would convert the microwaves back to electric and feed it to the local power network. Many studies were made over the years, thru the 20-thous, by NASA, US Dept of Energy (DOE), US Dept of Defense, universities, and aerospace companies. In October and November 2008 Paul Roseman, National Space Society, gave two talks on the solar power satellite, outlining today's prospects. The first was at the Sharp dance club in Chelsea on October 3rd. The next was on November 6th at the NYSkies-NSS Seminar. Altho Roseman presented the powersat, as it's sometimes called, as his own proposal, it has enough features shared by others that it is more of a general plan adaptable by almost any promotor of space- based power plants. My comments here summarize the situation, banking off of Roseman's talks. The ideas are not peculiar to him. Comments here are applicable to the project as a whole and not specificly the person offering it.
Motivation -------- Now, as in the 1970s, the motivation to exploit space-based solar power was the potential depletion of fossil fuels, ecological and environmental degradation from burning the fuels, erratic price and political manipulation of fossil fuel. Solar power is free fuel, infinite in supply, and proofed against overseas interference, perfectly clean with no effluent or emission. In the 1970s we had the interruption of oil supply by Iran, bitter winters that froze coal supply, new environmental regulation, steep (for the time) increases in crude oil price, manipulation of Caspian Sea oil by the Soviet Union. Today we have similar ills, with a new roster of players. On the other hand, the growth in electric demand is moderated since the 1970s due to sustainability, greener lifestyle, recycling, more efficient machines and devices, shift to electronic from mechanical products. So the rapid growth of the 1970s slowed substantially, reducing the need for more generating plants. New facilities are definitely needed and are being built, but by ordinary industrial procedures not obvious to the utility customer. There are no booklets in the bills proclaiming the next new power plant down the road. New projects tend to far smaller than formerly, a few hundred megawatts each, and placed on small lands of a few acres. This growth in supply seems to satisfy the future electric needs for the midterm future without having to appeal to space-based energy sources.
DOE-NASA study ------------ In the late 1970s I worked, thru my office, on one such study run by NASA and the newly formed DOE. The idea was to assess the feasibility of supplying a major portion of electric for a large market area in the US by a space solar power satellite. My work was mostly on the handling of the microwave beam when it reached Earth, but my office had to coordinate with other units in scoping out the entire power system from orbit to customer. The idea was to field a huge arena of photovoltaic cells in a geostationary orbit. The electric produced by the cells would be turned into a beam of microwaves. The microwave would be aimed at a station on Earth that turns it back to electric. Suitable equipment at this station fixes up the current to feed into the surrounding power network. While this sounds like a repeat of what I said in 'Introduction' the basic plan hasn't changed much at all in the intervening 40 years. Only some details advanced and, believe ir not, we may soon end up with a space capability that reverts BACK to the 1960s! My office assumed that some how the development and design and proving of the power station was carried by funding other than from the electric power industry. At that time the industry was occupied with a sharp growth in demand and massive expenditures for new traditional power plants. At that time these included large coal and nuclear stations. Thus, the industry would not be willing to try an experiment, which may or may not work, when it needed more power facilities within a couple years. An other situation then, and possibly to repeat now, was the severe tightness of funding. Interest rates for loans and bonds was in the tens of percent and the debt payments consumed a large portion of the industry's current revenue. There plain wasn't spare change around to allocate to a new form of electric in space.
Cell area ------- In the 1970s a solar cell of production and spaceworthy quality yielded about 100 watt/meter2, or about 8% efficacy. Incident solar power at Earth distance from the Sun is about 1,400 watt/meter2. This is the absolute maximum electric an ideal conversion process can yield. There just ain't no more sunlight to squeeze energy out of. To generate a given power in watts, the required area is the power divided by efficacy. For 100Kw, about the demand of ISS, from cells of 200w/m2 yield, you need (100,000w)/(200w/m2)=(500m2). This is about the area of a room 22-1/2 meter square. However, this power is that at the cell. There are losses, which in current space arts and skills are about 30% between the cell output terminals and the wall sockets. We need more like 650m2 of cell area to supply ISS. That's a floor about 25-1/2 meter square. This is, in fact, about the cell area of ISS. The panels are much larger due to structure and spacing between the cells. Power efficacy of solar cells is improving. So far and in the near future, there will likely be no space-worthy cells better than 300w/m2 yield. In lab experiments, yields of 400 to 500w/m2 are reported. These are in rigs totally unsuited for making real solar cells. Many space advocates insist that such large yields are for cells that are now at sale in the likes of Radio Shack. They can be affixed to panels and sent into space tomorrow.
Panels ---- Solar cells to generate a reliable supply of electric must be faced toward the Sun. ISS is bodily rotated to face its panels toward the Sun. This is why there's so wide a range of brilliance of ISS when it passes thru your sky. The panels if tilted edgeon to you make the station much dimmer than if they are faced toward you. What good are solar cells aiming down to the ground? ISS has cells on both sides of its panels to lessen the maneuvering it has to do. When one side faces you, the other is aiming up toward the Sun. Most of the mass and bulk of the ISS panels is in the framework, hardware, and wiring. For a power station with its immense panels, this mass would be fabulously large. The frame must be extra strong to withstand torque, inertial reaction, flexure and torsion, and momentum transfer, solar pressure, magnetic stress, even tidal gravity from the Moon. All in all, the area of the panel, with its cells and frames, is about twice that of the cells alone.
Powersat area ----------- Because of the fabulous expense and effort to place any large body in geostationary orbit, you want that powersat to produce a massive amount of energy to recover costs. You also want large output to displace Earth-based power plants that for one reason or other are not so desirable to operate. All plans for powersats propose huge outputs in the multigigawatt range. A typical scenario is a 10Gw satellite, but it is sometimes not clear if this is the collected power in orbit or that ultimately reaching the ground. In the DOE-NASA study my office allowed 10Gw reaching the ground, regardless of what is collected in orbit. There will be losses along the way from the electric in orbit and that on the ground, which my office took to be 50 percent. That was based on the ability then to convert to and from microwaves and absorption in the air. The powersat would have to produce 20Gw on orbit, which calls for a cell area of some 67,000,000m2, 67Km2! This is about about twice the area of Manhattan!! The optimistic 300w/m2 efficacy and 30% conversion in orbit is assumed. When the frame is factored in, we got a panel size, not just cells, of some 130Km2. If this sounds ridiculous, there are dreamy plans out there purposely showing such immense structures, all with teeny astronauts flitting around them. Some folk are walking around who don't blink at such figures.
Construction ---------- Roseman emphasized the construction methods, using low Earth orbit to assemble the powersat modules and boost them to geostationary orbit for final assembly. He made heavy use of reusable fuel tanks as fuselages of the fabrication base. Astronauts live and work in this base and the operations in the higher orbit are done by remote control or automatonicly. The idea is to keep the people within reach of Earth in case of trouble, like the concerns for the Shuttle flights. The powersat would be uncrewed. The modules would be such that they could be docked and attached without humans on the spot. Then, somehow, never explained by spacefarers, the powersat would be placed into commercial service. In the 1970s there was no spacecraft that could be a model for building the space solar power satellite. Skylab and Salyut were the only large craft in orbit and these were sent up in completed form. Only trivial unfurling, extending, aiming, and so on were needed to put the craft into operation. It is not at all clear from Roseman or others how large a workforce is needed to build the solar station. Assuming they stay in the low-orbit base, a ten-year program could mean 20 to 30 changes of crew, each having several dozen people. That's a lot of Shuttle or Soyuz or Orion flights.
Human crew -------- In the 1970s scenario we assumed a crewed powersat because there was no fully operational means of running the station entirely on its own. in any case we felt a crew had to be on hand to look after the machinery and catch trouble before it gets out of hand. For that study we had to estimate the cost of crewing the satellite. There was no comparable facility on Earth to judge the operating costs so we combined two extremely specialized facilities on Earth. We took the costs of crewing a nuclear power plant and a submarine for their complexity, confined quarters, isolation, stress, machinery to look after, training requirement. We assumed that specific space-related training,to be an astronaut, was covered by NASA and the electric industry covered the utility-related aspects of the crew.
Space operations -------------- The Shuttle was not yet in service for the NASA-DOE report, but still an unproven design. The only large rocket for lifting heavy payloads to low Earth orbit or moving them to geostationary orbit was the Saturn-V system. We configured the Saturn-V and Apollo capsules to ferry humans and materials to the fabrication base with dozens of flights. Roseman showed sealed pods at the ends of a rotating column to generate gravity by centrifugal force. He, like just about all other space fans, completely disregarded Coriolis force. The column and pods are made from spent fuel tanks of previous launches to the base. In the DOE-NASA study we put in a low-orbit station like that showed by Roseman. It was a dedicated structure, a rebuilt extra Saturn fuselage, like Skylab. It would be the upper stage that enters orbit and is occupied by the crew from a later flight. Transfer of humans from capsule to base was by spacewalk. Materials went over by hauling them to tiedowns outside the base. Spacewalks would bring the pieces together and couple them into the large modules for the move to high orbit. The base was merely the living quarters for the crew. All work was done outside where it was possible to configure pieces larger than the base itself and than fit them onto the upper Saturn stage for the trip upstairs. . Nothing would be manufactured or made from scratch in orbit. There was and still is now no means to do that. The fabrication base would assemble the small items into larger ones and fit them with means for hooking them up via remote control. We put humans on the power satellite for the sheer necessity of running the station and looking after it. There was no way we would allow such a huge project sit unattended. Far too many things can and will go wrong. Crews would be exchanged by upper stage Saturn and an Apollo capsule from time to time, but I can't recall the term of duty we proposed. Roseman has the power plant running automaticly with remote supervision. All humans stay at the lower base. His heavy lift vehicle is the Ares-Orion system. However, this system is not intended for any construction work. They are stricta mente for ferrying to and from terminals like ISS. It would be an immense project in itself to add extra function to the Ares-Orion to allow construction with them. This is in the face of recent NASA cutback in the Orion design. it may now carry only 4 crew, not 6. It may have far less propulsion so it has to wait at the Moon for a favorable gravity gradient to return to Earth, not come back on demand. It is noteworthy that neither then nor now is the Shuttle employed! The first study preceded the Shuttle, A future one comes after Shuttle flights terminate. It is also noteworthy that after the Shuttle is grounded, there is NO means of construction planned by ANY nation. The Orion-Ares system is only for carrying humans and supplies like a car. The lunar habitat will be buttoned up on Earth, sent to the Moon via Ares rocket, and landed there in one piece. Only trivial fitting is done on the Moon like running a waste hose out from the base or plugging extension cords to power instruments placed away from the base. Hence, any project calling for actual construction in space is doomed to die simply because there will be no construction services or facilities around in the midterm future.
Costs --- Construction of the pwwersat would be enormously expensive, no matter what spacefarers say. ISS cost some $100 billion dollars -- as at November 2008 -- and took some ten years to complete. It involved about 20 Shuttle flights, many crew changes, and scores of supply Progress flights. ISS has a crew of three, maybe six when completed, and no real function other than keeping the crew alive. The space solar power station, orders larger and higher and massive, would cost correspondingly more than ISS. Realistic estimates, suing reasonably expected space skills and methods, are in the trillions of dollars. Unless some utterly unexpected new and cheap means of lifting from Earth, traveling and working in space, supporting humans in space comes along, there is no hope or dream of lowering this incredible cost. Roseman and others theorize, with no backing, that launch costs will magicly decline to a myriad of dollars per kilogram. This could apply to a satellite tossed into low Earth orbit. It can not apply to human occupants who have to return to the ground alive and well. There's a lot more than launch costs, which are often the lesser part of a mission's total price. Design, testing, proving, building components costs plenty. Training crews for the fabrication base costs plenty. Inventing the robots to assemble the power station in high orbit costs plenty. Many systems proposed for the power satellite don't exist now, not even in smaller form. They have to be invented, a very iffy occurrence to predict. If any one critical portion fails to mature in time to send up to the powersat, it doesn't go up. This is, in fact, the fate of many spaceprobes. The Mars Science Lab may be the next example. Many of whose parts aren't yet worked out. The bottom line is that there just is no fiscal sense to move to a space-based electric generating facility. Only if we get really near the end of coal and petroleum supply will we consider a space based system. But even then, why must it be in orbit? Can't it be on the Moon? It will rise and set daily with the Moon, but is that so terrible? We can collect the power during the visible hours and let other longitude belts take power when the Moon passes over them. In fact, this feature could attract international cooperation being that the Moon is visible from every country as she orbits the Earth.
Fuel tanks? --------- I discuss here just one design feature illustrated by Roseman. His plan employs spent fuel tanks as fuselages for the low-orbit station. These would come from the rockets bringing parts for the station into low-Earth orbit. The tanks would be assembled into a column and pods to make a rotating construct for artificial gravity. The column is only to transfer between pods and maybe store of materials and supplies. The pods would be sealed, like the original tanks, with crew inside a closef environment. Roseman showed nothing of how this crew receives pieces for the power station and how they get the finished modules to their booster rockets. The pods in his pictures indeed looked, well, sealed. Why the closed environment? Is it necessary, convenient, desirable for building a solar satellite? No one who advocates this scheme offers competent answers. The best is that such a habitat is typical of a futurist society in space. Is it? Perhaps for a interplanetary flight, where there is no routine need to go outside, a closed capsule is the sensible method. But what about a craft meant to interact with materials coming up from Earth, worked on in orbit, then delivered to high orbit? Isn't it just cheaper and easier to build the fabrication plant in sections on Earth, ferry them into low orbit, couple them up like a new ISS? Crew would freely enter and leave the plant as they need to to work on the power satellite's components. The plant reasonably must have handholds, tiedowns, hatches, vents, antennae, grippers, electric cables, navigation devices, alarm sensors, and lots more over its outer surface. These have to operated from both inside and outside the craft. A plant built into an empty fuel tank would have a smooth solid exterior of no use for doing construction work. If you postulate that while in space, holes and fittings and attachments will be made to the tank, you lose all hope of savings in keeping the tank. You might as well build the hull on Earth with all the proper penetrations. An other question is that can the tank be built to accommodate its future use as a hull? It could be fitted with lugs, seats, brackets, rails, sockets, and the like, into which the guts of the fabrication plant will attach. This is a needless complication that could compromise the tank's primary function of handling fuel. Interior panels to mate with a section of habitat later could induce turbulence and cavitation during fuel flow. Is the fuel tank really empty? Hardly. Residual fuel, film or pockets of vapor, have to the purged. This is a dangerous chore on Earth, like cleaning abandoned gasoline tanks. Fuel can be highly poisonous and corrosive. Ordinary spacesuits can not survive the fumes or spills during an in-orbit cleanup. You must invent a new protective suit, with special tools and life support, just to clean out the tank. If safe and clean methods can be figured out, they will surely be extremely hazardous, complex, slow, and costly. For what? Avoid the destructive reentry of a fuel tank? It seems that trying to make a space hardware do two utterly anatagonist functions will be far more costly and risky than to just have one function for each of two separate pieces. A final issue. Roseman notes that recoverable fuel tanks will be a standard feature of future rockets, specificly to turn into habitats in orbit. What rocket? Neither Area, nor Arianne, nor any other rocket on the drawing boards features salvageable tanks for use in orbit.
Orbital stability --------------- A geostationary orbit is claimed by many space advocates as a stable fixed spot in space. A satellite placed there is like in a peghole to stand still over the equator at a given longitude. This is an outdated notion from the 1950s when we did not yet chart out the gravity field around Earth. The satellite will drift away from its home location from various tugs of gravity from Sun and Moon. It may suffer push from solar pressure and magnetic fields. That's why geostationary satellites have onboard jets to keep nudging it back to home. They are decommissioned not so much from breakdown but from running out of propellent to maintain their orbital state. An other newer concern is the disposal of retired or dead geostationary objects. The general practice is to boost them to a much higher orbit where in time they will be pulled out of the Earth's domain to become solar moons. This is the graveyard belt about 60,000 kilometers from Earth. Just how a retired powersat will be disposed of is quite unknown. It may have to be deliberately boosted into solar orbit so it spirals to death into the Sun. The reason to move them at all is to vacant the longitude seats for new satellites. The geostationary belt, 42,000 kilometers from Earth, has crowded zones over longitudes requiring dense telcomms service, while over other longitudes there are few satellites. The linear spacing in orbit per degree of longitude is about 730 kilometers. If we allow a safety zone of 50 kilometers on each side of a satellite, each degree of longitude could contain up to 7 satellites. The buffer helps avoid interference of signals between adjacent satellites and possible collision as the satellites wander from home. Because the powersat would be so immense and so crucial for human life, the exclusion zone may be 200 kilometers on each side. So in its longitude slot only 3 other small satellites could fit.
lifespan ------ Space proponents count on a power station lasting indefinitely or for ever. They claim the space hardware is durable as they point to examples like Voyager, Mars rovers, SOHO. This is nonsense. Saellites can and do fail. When a spaceprobe does fail, there is usually no way to repair it. The singular exception is Hubble Space Telescope, which went thru several visits via Shuttle to replace broken instruments or install upgraded ones. Even ISS is essentially a frozen craft in orbit. Small items are brought up by Shuttle or Progress, but nothing in the order of replacing a structural section can be done to it. Like any other spaceprobe, the space solar power satellite is subject to the unforgiving space climate. Metals weaken, plastics get brittle, glass crazes. Mechanical damage comes from meteors and (since October 2008) asteroids. Sputtering and spalling will destroy the solar cells. Motors burn out, switches stick, wires snap, springs loosen, transformers split, electronics overheat, sensors and trackers go astray, chips get zapped, and more. With no means in geostationary orbit to send a repair visit, the powersat has to be curtailed in operations. Certain solar panels are shut off, for example. In time the power sent to Earth declines in sudden steps until there is too little to earn the keep of the powersat. At the same time, the lost space-based power has to be made up with conventional sources on Earth. More nuclear plants may be called for. Eventually, the cost and effort to run the powersat's ground station is on longer acceptable and it, too, must be retired. To close out the powersat, it must be deliberately shut down, then moved to the graveyard orbit or spiked into the Sun. Then the ground station is demolished and its land freed for other development. How long will this be after commissioning the satellite? The design lifespan has to be several decades, like most other large ground power plants. That's for the initial equipage, without continual replacement over its lifespan. A ground power station undergoes continual maintenance and repair over its many-decade life. By the time it is retired, sometimes because there are newer alternative sources of electric rather than actual disfunction, there may be few of its original components in it. There is no prospect of repairs or replacement in a powersat in geostationary orbit. Its lifespan is a minimum one, that of the first major system to break down.
Miccrowaves --------- Electromagnetic radiation conveys energy from its transmitter to its receiver. That's how a radio or remote control works, a feature first exploited by Tesla in the 1890s. The choice of the microwave band is dictated by the properties of the Earth's atmosphere. From radio astronomy and planetary radar, this band penetrates the air better than many others. It is more tolerant of cloud, humidity, dust to reach the ground with enough energy density to yield useful amounts of electric. The specific frequency, from a centimeter to submillimeter, is dictated also by the assignment of wavebands by the US FCC to other functions. If the beam lands near a radio astronomy center, there could be intense interference with observations, a form of radio graffiti. The only other significant alternative waveband proposed was the optical band. Here the energy would be carried by laser beams. The advantage is that the orders shorter wavelength allows for a tighter focus on the ground, requiring a smaller area for the receiver. This is no longer seriously considered for the gross hazard from a wayward beam. 10Gw poured over a single square kilometer outside the receiver campus is not a good thing. That's 10Kw/m2, an incinerator ray. Political and social reaction against a laser-based power system would be vitriolicly negative. Check out the warnings on DVD players and lecture pointers, and ask supermarket workers about the laser in the paypoint scanners. A one kilowatt laser is under test as a shoulder-mount gun to knock down planes and cruise missiles. Now here comes a laser beam fully ten million times stronger to a cornfield near you. Microwaves are not without their own hazards. Microwave ovens have metallized windows to shield the operator from leaks. Cell phones and other wireless devices have warnings about long close position of the device near the brain. Microwave guns are under design for cooking the brains of enemy soldiers. Casualties will be cleaner and neater. Enemy structures and facilities will be safer to capture and occupy. The column of dense radiation must have a no-fly zone around it. Planes would be excluded from it and surrounds, much as they are steered away from so many other no-fly sectors around the country. Apart from the nuisance of adding yet an other such sector, I see no special obstacle to air traffic.
Reception at Earth ---------------- My office allowed that somehow the power from the power satellite is placed onto a microwave beam and now I had to deal with it when it gets to the ground. The initial problem was that 10Gw then, and now, is a monster amount of power to put into the utility grid at one spot, like 10 typical nuclear plants on one campus. There just weren't any such concentration of generation in the US except for possibly the Hoover or Bonneville projects out west. In the east, the largest in the 1970s were 2 to 3Gw projects, like Niagara Falls and Ravenswood. Both require massive collateral works to get the power from them to the electric grid. Niagara Falls does this by many 345Kv transmission lines in both US and Canada (it's a joint operation) that was built as an integral part of the project. Ravenswood has a similar set of 345Kv lines, all underground, threading thruout Manhattan. The cost of these works must be part of the overall project cost. In fact, for hydroelectric projects, my office requires that such power lines be incorporated in the project licence. However, space advocates blithely ignore this part of the powersat proposal, thinking that the electric can be dumped into the existing network with no extra facilities to capture it. It can not.
Receiver ------ Once the power leaves the powersat, spacefarers let it alone. Their illustrations show a pencil beam touching Earth at a point, which magicly becomes the electric to run your television, air condition, computer. Air condition in homes and offices were rapidly becoming popular in the 1970s. So great was the increase in air condition that it shifted some utility peak load from winter to summer. Both NYS and PJM turned into summer peaking regions in the 1970s. NYS is the New York State power region inclusing Con Edison. PJM is the Pennsylvania-Jersey-Maryland power region. Each operates as a unified electric system and coordinates electric flow between them and with other power regions. That beam, filled with 10 gigawatts of power, has to land at some particular location. For my market of NYS-PJM, the likely location of the receiving station would be central within that region. Now here's a fact no spacefarer likes to talk about. How big is this thing? It turns out to be humongous! For starts, the beam does feather out and wander as it comes down from the powersat, The antenna area must be large enough to capture all of it, else somw of the incoming power is spilled and lost. For safety and health reasons the beam has to be diffuse, of the order of incoming sunlight, or about 1Kw/m2. For the 10Gw in this model, that is an area of 10Km2 or about 3-1/2Km diameter. This is all of Lower Manhattan below Canal Street. Allowing a 500-m buffer for wander and to minimize accidental trespass by people or animal, the campus for the receiving station would be about 16Km2 area. That's Manhattan south of Houston Street It wasn't then and still is not today easy to find such a large available land for a single large-scale project. If anything, it's a lot harder today with the enhanced public participation in siting procedures and evolution of environmental awareness. Ideally the receiver should be located away from significant population and anticipated new development. The experience in hand from airports and industrial works is worth reviewing. Once in remote places, many of these facilities are now hemmed in by population growth and are now often regarded as nuisances and hazards.
Locating the receiver ------------------- For the NYS-PJM market we found a potential place to site the receiver. There was and still is a thinly populated region along the NY-PA border with little industry or commerce. It is remote from jobs and towns and has poor farming or mining potential. It was, on the other hand, close to backbone transmission lines and there was room to add more lines. So we placed, for study purposes, the receiver on the Pennsylvania side of the state border and added several output substations and a lots of 345Kv and 500Kv lines to reach to major nodes in the power network. New York had long ago settled on 345Kv for its backbone voltage while PJM chose 500Kv. Connection between the two then and now is via massive transformers and phase shifters. As fate had it, many decades later this area would become the Cherry Springs State Forest, site of the Cherry Springs and Black Forest starparties! There NEVER was a serious plan to build this powerat ground station there, being that there NEVER was an actual project for the powersat. It was all a conceptual study on paper. The peripheral works would in themselfs substantial, several large switchyards, many transformer banks, forests of power lines. We had to choose the connection points within the grid to avoid overload and keep a balanced loading. We did flow simulations to see how the new power flux, in a north-south orientation, would disturb the normal east-west flow thru the NYS-PJM region. It wasn't easy, but we did manage to get 10Hw into the grid for most of the time. In the peak hours and specially during seasonal diversity periods, we would have to spill space power because there ws no capacity in the grid to take it all. Note well that scoping out a power system is a hell of a lot more than adding up the capacity of power plants. You have to examine the power flow over the grid. There are times when the flow on a given transmission line must be limited to prevent overheating or instability or reserve problems. A line working the satellite ground station is no different.
Transmission ---------- In the 1970s almost all electric transmission was via alternating current. Direct current power lines were uncommon with few under proposal for the future. It was simply cheaper and easier to move electric in AC form, particularly thru transformers. On the other hand, AC was more sensitive to geophysical disruptions, had was already documented in the late 1960s in my office. the reason was vaguely appreciated because space-based monitoring of the Sun was still underdeveloped. The output of the powersat is direct current, being a photovoltaic process. The beam of microwave would also be direct current, by the nature of the power conversion from the solar cells. Hence, the power at the ground is a stream of direct current, which off hand would have to be changed back to AC. We had then little experience with DC/AC conversion on a large scale. The alternators available were for modest power levels, like in industrial or traction operations. Unless we installed massive numbers of alternators, it may be best to leave the power output in AC and do the conversion at the far receiving points thruout the NYS-PJM area. For recognition sake, we postulated 800KV DC lines (+/-400KV) to several farther connection points, more to show that we were aware of the potential for DC transmission in the east, like that running on the west coast. Since the 1970s, several high voltage DC lines were built connecting Quebec with New England and New York State, all working quite well with no serious problems. They proved to withstand geophysical attacks better than similar voltage of AC lines and avoid any troubles from alternating currents in air or structures.
Utility role ---------- We postulated that the consortium of electric companies in the NYS and PJM areas would pool resources to pay for the construction and operation of the power satellite. There was in the 1970s an established practice of sharing costs of building and running ground power plants like Homer City, Seneca, Roseton, Keystone. So the legal and financial mechanisms would be in place. The development costs to perfect the space-related phases of the project were picked up by NASA. It would also take care of the space- related training and qualification of crew and the transport to and from the station. Utilities would pay for the work done by the crew on orbit and during the stay on the station. Modern proposals assume a government ownership and operation, like a TVA or COE project, perhaps from realization that the costs are so immense that no aggregate of private companies can finance it. One curious aspect of a modern plan is the presumption that utilities are chopping at the bit to get space-based electric. This is not at all the case. For starts, some advocates still refer to their legacy power company when suggesting partners in the project In bygone years, a typical utility ran power planets and sold the electric to its customers. Con Edison in New York did that. It had plants all over the City and shares of plants elsewhere. It carried the output thruout the City on its power lines to the customers. Since about 10 years ago, utilities are now devested. Each now either generates the electric or sells it to customers. It can no longer do both. Con Edison, for example, kept its customers and got rid of its generating stations. Some were retired for being too old. Others were sold to other utilities or to allnew power producers. Your electric bill from Con Edison has two parts. One, the larger, is the cost of the electric bought from energy producers; the other, Con Edison's cost of shipping the energy to you. Only the latter portion is still under state regulation! The energy purchases are under free market costs. This situation has curious anomalies. Florida Power & Light, in Florida, went to generating, having sold off its customers. It then bought up other generating plants around the country! My office now deals with Florida P&L for plants it runs in the state of Maine! What happened is that there is no 'electric utility industry' in the traditional sense to take on a solar power satellite project, however much it may like to get its energy. There is, from the fragmentation of the generation part of the industry, no single company large enough to tackle such a project. A consortium is still needed but now it must be made from fiercely competing firms.
Reliability --------- Roseman and others emphasize that the powersat is on duty at all hours, save for a brief period when its orbit passes thru the Earth's shadow twice a year. These periods are known in advance so other supply into the market can be arranged. Fortunately these blackout periods are near the equinoxes, when power load is at moderate, neither at the summer or winter peak levels. Thus, we could postulate that the powersat was then taken off line for maintenance. Weather was a problem. Thick clouds, frequent over the market, would weaken the beam. The power output from the receiver would drop as much as several gigawatts. Because weather is unpredictable in any dependible manner, the power output would be a random fluctuation that resembled that of a fickle river for a hydroelectric plant. In sunny days the output was stable and ample. The geostationary orbit allowed generation to continue at local night, with the powersat hovering in the high south sky as an amazingly brilliant star. Rain or heavy humidity would soak up the beam, diverting energy from the receiver. The absorbed energy was feared to cause local disruptions in weather, which at the time could not be proved. it still can't, even with a far greater ability to model weather on supercomputers. Today this is no laughing issue. Public concern over carbon dioxide emissions, radon sippage, nuclear waste disposal, asbestos and lead airborne particles, and more would force a detailed analysis of the effects of microwave heaming down on a ground base. For starts, it is plausible that the artificially warmed air above the station would form a permanent low-pressure core. Snow, common in the market, was an issue. It soaked up energy to melt before reaching the ground. It was a real possibility that the lack of snow would louse up local water cycles. There was the prospect that a solar power satellite could lessen the power generation by nearby hydroelectric projects. So, for the most part we could count at some good piece of generation for most of the time, much like that of a huge hydro station on an erratic river. We were wary about employing it for system or contract power
Market for powersat ----------------- 10Gw is a big chunk of electric, far more than can be used by one town or one state. In the 1970s New York City needed about 9GW to meet its peak summer demand for electric. At other times the load was much less, down to about 4Gw. If the satellite power was dedicated to the City, most of it would be spilled. Some could be offered as dump power to other utilities. This is not the way to utilize the output from a massively complex and expensive satellite. An other issue was that it is insane from a reliability and integrity consideration to count on so large a portion of electric requirement on one source. Space solar power has to be supplemented by other, ground-based, sources in case of downtime or outage. A supplemental amount of capacity would be needed in several smaller plants to fill in for the satellite. I had to widen the market area for the space power to all of New York State and all of the PJM system. When planning a power system, the ideal scheme is to work the most efficient and largest plants continuously as much as practical. The older, smaller, less efficient plants are turned on and off to follow the rise and fall of electric demand. The most wasteful, most expensive plants are put on line for the peak demand periods, of a couple hours at most. Un the NYS-PJM area, the stacking of generation was in the 1970s first the large hydro works at Niagara Falls, Massena, and Susquehanna River. Then the nuclear stations at, as examples, Peach Bottom and Salem, Then come the large coal plants like Conemaugh, Keystone, and Homer City. The load-following projects were the smaller coal and other fossil fuel units. To carry the highest demands, jet turbines and small hydro plants were added. Besides just the age, size, and economy of power plants, the sequence of adding them to the supply depends on their operating mode. A jet turbine can be started and put on line within a few minutes, but they are limited by their allowable running hours per week. They are built around ordinary airplane jet engines. The dispatching of these plants thruout the region was coordinated by operating centers near Philadelphia PA for PJM and Albany NY for HYS. These centers also manage the purchase and sale of electric with other regions. It could for a given hour be cheaper or more effective to buy power than to turn on an other power plant. They must arrange for substitute supply when one of their own plants is off duty. It was into this matrix the the 1970s study placed the power satellite. It would displace some, but hardly all, of the fossil-fuel power plants to cover the base load requirements. It could for the NYS-PJM region supply pumping for the storage plants like Muddy Run, Yards Creek, and Blenheim-Gilboa. The situation today is similar, with a gradual increase in electric demand. The load on the grid is of a similar profile, with a rise and fall during the day and season. The important point to understand is that a 10Gw source, from any where, has to be placed in a very large market and not just for a town or small state. That requires major cooperation among the utilities in that region to build the ground facilities to allocate the power among them.
Environment --------- In spite of the promised purity of solar power, there are many environmental and ecological concerns, many unresolved as at now. There is little worry about the actual production of energy from the Sun, once the project is in service. The problems come from the construction, which has all the burdens on the environment that a massive rocket activity offers. Hundreds of rocket flights are needed to build the base station and several per year there after to service it. Rocket exhaust can be toxic and is concentrated in around the launch base. For the US this is Cape Kennedy, the other bases being too small for Ares rockets, or Saturn in the older work. Noise, water vapor, waste gases, partially-combusted fuel, jettisoned debris, shockwaves, and the potential for ground damage by falling pieces accompany each rocket launch. Leakage and spills of fuel and chemicals into local waters can upset ecology and degrade aesthetics. Nighttime launches insult the sky with massive prolonged luminous graffiti for hundreds of kilometers around the launch pad. This is hardly mentioned by spacefarers or astronomers on the premise that it is predictable. Wait until the launch is over to resume stargazing. These folk know nothing about the scratchy schedule of rocket launches. Hazards come from the Earth-based industry to make the station parts and equipment and supplies. These are of the usual kind, of waste discharges, smoke and soot, spoiled land, noise, fumes, luminous graffiti, attraction to crime and nuisance, traffic congestion, political influence, social abuses. Hence, a single space solar power satellite can insult humankind with the effect of the activity of a whole state or region of the country compressed n a ten-year span. The costs of remediation of these effects must be rolled into the price of the electric produced by the power station, For ground-based power plaets, such costs are a significant part of your electric bill.. Will this all-in price compromise the validity of the project? No ne can tell. And no one is going to give the trillions of dollars to find out the hard way.
Luminous graffiti --------------- If the panels were as reflective as those on ISS, the powersat at times could appear as a, gulp!, -16 magnitude star, about 10 times brighter than the full Moon! The 1970s were the nascent years of the ecological movement, so there was not yet a significant concern for 'light pollution' or loss of night darkness. Today there would be a mass agitation against putting something in the sky that stayed in one place and shined so brightly onto the ground. Arguments that it would aid in navigation at night (it's always fixed in the sky) just didn't fly. Nor did those that the illumination would facilitate farming and other chores normally closed at night. Perhaps it could eliminate the need for much ground-level lighting on streets or fields? No go. As a target to inspect during stargazing, the powersat would be a sizable angular spot. At about 5Km diameter and 38,000Km slant range from the US northeast, the satellite would appear about 27 arcseconds across. That's about the size of a 50Km crater on the Moon. Curiously, no astronomy interest, home or campus, and birtually no darksky advocate!, agitates against the solar power projecton for its luminous graffiti. I believe that's because there is no credible chance of it ever being built.
Public safety ----------- As part of our concern we had to consider the effects of the ground station on public safety. Already concern was rising among the public for safety in nuclear and hydroelectric plants. Longterm hazards were recognized from air pollution from coal and other fossil fuel-burning plants, plus disposal of the ash and slug from them. What were the potential hazards from the intense microwave beam coming down from the sky? As long as people and animals were kept away, by a buffer region patrolled and fenced, there would be none. Workers at the station could be offsite beyond the buffer. There was a problem with 'shutting down' the station for repair or maintenance. Like a nuclear plant, we can not turn off the prime power, the disintegration of atoms or the power beam from space. In such cases, we had to devise suits and vehicles that shielded workers against the beam when they had to enter the project campus. This is quite different from a coal plant where it can physicly stop burning the fuel, cool off, and let workers enter its guts. They can ear ordinary industrial safety gear. While the public can be excluded from the receiver campus, it may object vigorously to the sequester of a large piece of land from their use and enjoyment. They can not farm or graze on it, likely can not picnic, hike, do park recreation there. Roads would be relocated away from the campus, upsetting traffic circulation. Emotional effects could reduce property values, community attraction, industry/commerce development.
Security ------ In the 1970s there were small, but harmful, attacks on utilities from environmental groups or individuals. They bombed power lines and substations thruout the country. My office cooperated with the FBI in dealing with these incidents. It would be a stretch to total the receiver base, it being far too large and spread out for a single knock out blow. However, a switchyard or transformer could be taken out by a nogoodnik. This damage would weaken the service from the station, require rerouting of power, and call for costly tedious repair. It was also feasible to cut a transmission line far from the station by strapping a plastic bomb to one of the towers. The station would sense loss of one of its outlets and adjust its operations accordingly. One way would be to turn off certain receiver antannae to reduce the load on the remaining lines. Energy from space would then be spilled. Of vastly greater concern, for which there was and still is no solution, it that the powersat in orbit is a sitting duck for any one who has it in for the United States. The 1970s was in the middle of the Cold War with the Soviet Union. In the years before the Star Wars program of the 1980s, space attacks were deceptively crude. Just ramming a satellite would demolish it. Spraying paint on its solar panels would cripple it. Breaking pieces off with grippers and claws would maim a satellite. Lasers shot into its sensors or cameras would blind it. All these methods were actively tried, by actual experiment or simulation, by both US and USSR. There was at the time utterly no way to ward off an attack upon the powersat, classed as a critical energy infrasturcture. There was no way to intercept the attack and probably no way to know of its approach. Suddenly there is no more power beam coming down to the ground and all comms with the satellite is lost. At night you see a flashing blinking star, the tumbling remains of the powersat. There was no way in hell the US would expose a crucial energy facility to such an obvious security risk. A single small enemy rocket, costing a few million rubles, could in an instant throw the entire NYS-PJM region into a irrecoverable power blackout. Today, the 20-thous, there still is no feasible way to protect a powersat. The threat now comes from several countries, not just the old USSR (Russia is going thru a nationalist fit). Think of Venezuela, Red China, North Korea, Iran, Pakistan, Libya, to name only a few of the larger ones. Lots of countries have or soon will have space access and military capability there: the Ukraine, Belarus, India, Japan, North Korea, Iran, Taiwan, South Africa, Nigeria, Israel, Germany, France, again naming a few. If any of them gets, or feels, crossed by the US, a powersat could be a tempting target to get even on. If this assessment sounds like nonsense, as many spacefarers insist, you have only to look at Ground Zero. There, in the middle of the planetary capital, the World Trade Center was wasted with a thoroly low-tech weapon passing thru an indefendible airspace.
Military involvement ------------------ The space solar power satellite in all its forms is passionately presented as a pura mente civilian project to benefit humankind. It is proclaimed as a mission for civilian space agencies and industry. Neither Roseman nor other proponents realize that just about any space project now and in the future has a heavy thumbprint of military potential in it. The utter disregard for this basic fact of life seems shocking, given the many current examples of space programs of civilian benefit that are in whole or part a military operation. To give three simple, yet major, examples the Space Shuttle, Clementine, and GPS enjoyed massive support from military interests. All are touted as principal examples of civilian benefit from space projects. The powersat can hardly be any different. Besides its incredible cost and dangers, which only a military establishment would think to absorb, there is the utility of a geostationary base overlooking Earth. It is reasonable to suppose that the powersat will carry spy devices and command & control services for military use. If this sounds unlikely or undesirable, note well that right now the USAF is negotiating with commercial telcomms companies to put military functions in future satellites. It would pay for the extra soalr panel and chassis room to support spy equipment while the satellite carries out its civilian telcomms operations. In Europe the Galileo project is seeking a military partnership altho it started as an all-civilian works.
International power ----------------- Because the electric from the satellite has to be sent to a one particular place, within one country, there could be little chance to attract overseas cooperation in building or running the satellite. In fact, for the US, there are only a few places with international operation. The major overseas partners for such joint electric operations are Canada and Quebec on account of the long shared border between them and the US. There are as yet only minor joint facilities with Mexico. The Niagara Falls and Massena projects straddle the US-Canada or US-Quebec border, so the works are jointly run by each pair of country. An other inducement for cooperation is that these plants are in the Great Lakes basin, controlled by the three countries thru the International Joint Commission on Great Lakes Regulation. The ability to transfer bulk electric across oceans is today nonexistent. For distances of a hundred or so kilometers, it is ridiculously expensive. There is no significant work to develop overseas electric transmission at this time and none is planned for the near future. Hence, A solar power ground base on Malta to send its output to Italy, Libya, Egypt, Greece is just not possible. Roseman offers that the low-orbit station could be platforms for training travelers for Moon and Mars flights by its artificial gravity. It just is easier and cheaper to build a specific satellite for this purpose that to tack it onto an industrial facility. There is the security issue again. Consider the heightened worry about Russia's role in ISS since summer of 2008. Given what it did in Georgia and wants to do in Poland, the Baltics, and Caspian Sea, it is not out of order to think Russia will bar US astronauts from its Soyuz lifeboat on ISS or refuse shipping US supplies to there by its Progress ships. Imagine the sword over the US if an overseas partner in the solar power station feels dissed? It could, litterally, throw a wrench into the gears and that's the end of electric service in the US east coast.
What century? ----------- The first idea for a space electric plant arose in the 1960s, when oldstyle weights and measures were prevalent in the US. Starting in the late 1970s there's been a steady migration toward metrics. All the space agencies and companies went metric by the late 1980s. It is a bit much to suppose that within a decade oldstyle will fade away. The reasonable accommodation is that Americans are bimodal, comfortable with both systems of units. Yet Roseman, and far too many other space fans, cling to oldstyle. They exert too little effort to move into the future, along with their agenda. This is among the queerest features of space advocacy I see. Astronomy went metric decades ago, with American home astronomers conversing fluently in either system. Home astronomers deal only in metrics with overseas associates, Yet even in reputable spacefaring litterature there is a predominance of oldstyle, even for material aimed at global readers. The result is a ball & chain on the American spacefarer for global support, recognition, credibility. It also induces a giggle factor with dealing with governments who may want to take up one of their ideas. For sure, Roseman's illustrations were adapted from other sources flecked with oldstyle measures. He could almost at sight alter the dimensions to metric before making the handouts, White out the old numbers and pen in the new. He didn't, thereby missing out an awfully basic step in building confidence in his audience. Yes, in the early days of the US space program, the engineers and scientists worked mostly in oldstyle. I have a copy of the operating manual and script for the Apollo-11 flight with detailed instructions for the ride to and from the Moon and activity on the lunar ground. Everything is in oldstyle! That's how it was back then. We be in the new millennium. If we be future-facing folk, we have no qualms about moving to metrics as quickly as practical. That does call for deliberate work. It's like being fluent in two languages, as in Belgium. For my own space advocacy, and that for astronomy, I employ metrics exclusively. It's been litterally 25 years -- back in the days of Halley's comet! -- since anyone raised a serious substantial objection to metrics. Yes, some audience do ask how much so-many kilograms is. I give a physical example, it's about the mass of a certain object. I never give the oldstyle equivalent. This does two things. First, it reminds that metrics are the essential ingredient of life in this century. Second, I subliminally give a lesson in visualizing a given metric quantity.
Conclusion -------- Since its conception in the 1960s, thru many studies since then, the allure of a solar power station in high orbit still attracts attention. The outcome so far is the same: It's not worth it. Unless and until a genuine breakthru in several of spacefaring skills and arts come along, there will never be a single kilowatt produced in space to light you lamps at home. Some space project promotors plead that there will be a way to get into space for ten dollars per kilogram or get 800 watts per square meter of solar cell. So they go and urge that the power station can and should be built now. They also commonly dismiss all thought of contingency. Everything will work correctly and perfectly. Every launch will succede by plan. Every part will fit exactly by plan. The electric will flow for decades without serious interruption. People on Earth will have such abundant cheap power the utility can pull out its meters and let you take all the electric you want for a flat rate per month. Need less to say, this plain will not happen. Just in New York, besides the World Trade Center, we had in the last ten years a major steam pipe eruption that eviscerated a midtown street, a GPS navigator that sent a car into Metro North tracks to be totaled by trains TWICE, a sinkhole near Union Square that swallowed several cars, helicopter crashes, ferry boat collision that killed a dozen people, airliner lose its tail on takeoff to crash in the Rockaways, airliner blow up off Long Island from a fuel leak, train wreck in New Jersey due to a color blind driver, a construction elevator rip away from a skyscraper in Times Square, and lots more. If you're looking for calamities in space, consider just one week in November 2008. Globalstar telcomms company warned that 42 of its 50 satellites are deteriorating so they will lose function in early 2009, crippling the firm's voice services. Orbcomm reported that 6 new satellites launched in June 2008 had defective attitude control systems, their reaction wheels not working properly. In addition to actual catastrophes we got plenty of examples of things that didn't work at all. The robotrain on the BMT Canarsie line never worked after years of tinkering, GPS-powered bus displays gave wrong times and locations of buses, atomic power plant inside Morningside Park that never fired up, Second Avenue subway keeps getting dumbed down but never built. All of these were part of machines and systems of long maturity and experience. Yet stuff happens.