The Seventies DOE/NASA Photo voltaic Energy Satellite tv for pc Research
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| Picture 1 (see callout in textual content). Picture credit score: NASA. |
Of all the various spaceflight ideas NASA has studied with any diploma of seriousness, most likely probably the most monumental was the Photo voltaic Energy Satellite tv for pc (SPS) fleet. Czech-born physicist/engineer Peter Glaser outlined the idea in a short article within the esteemed journal Science in November 1968, and was awarded a patent for his invention on Christmas Day 1973.
Glaser had seen {that a} satellite tv for pc in geosynchronous Earth orbit (GEO), 35,786 kilometers above the equator, would cross by way of Earth’s shadow for only some minutes every year. It was well-known {that a} satellite tv for pc in equatorial GEO strikes on the identical velocity the Earth rotates on the equator (1609 kilometers per hour). Because of this, for individuals on Earth’s floor, the satellite tv for pc seems to hold immobile over one spot on the equator. Glaser additionally understood that electrical energy didn’t should journey by way of wires; it might be beamed from a transmitter to a receiver.
Glaser combined these three elements and got here up with a satellite tv for pc in equatorial GEO that might use photo voltaic cells to transform daylight into electrical energy, convert the electrical energy into microwaves, and beam the microwaves at a receiving antenna (rectenna) on Earth. The rectenna would flip the microwaves again into electrical energy, then wires would carry it to the electrical utility grid.
The nice benefit an SPS loved over a photo voltaic array on Earth’s floor was, as talked about, that it could spend nearly no time in Earth’s shadow. Earth’s rotation meant that an Earth-surface photo voltaic array may make electrical energy at most about half the time. The remainder of the time it could sit dormant underneath the evening sky.
NASA and its contractors displayed low-level curiosity within the SPS idea as early as 1972. Early work befell on the Jet Propulsion Laboratory and NASA Lewis Analysis Heart (now NASA Glenn), in addition to at Arthur D. Little, a Cambridge, Massachusetts-based engineering agency of which Glaser was a Vice President. The extent of effort elevated in 1973, after the Group of Petroleum Exporting Nations imposed an oil embargo to punish the U.S. and different industrialized nations for his or her assist of Israel within the 1973 Yom Kippur Battle. By 1976, NASA Johnson Area Heart in Houston, Texas, and NASA Marshall Area Flight Heart in Huntsville, Alabama, led SPS research inside the area company.
In June 1975, NASA and the Power Analysis and Improvement Administration (ERDA) signed a Memorandum of Understanding calling for joint SPS analysis. ERDA started to plan an SPS examine with NASA firstly of Federal Fiscal Yr 1977 (October 1976), within the waning days of Gerald Ford’s caretaker Presidency. The three-phase examine started in July 1977. Whole value of the joint SPS research, which have been meant to final for 3 years, was $15.6 million, of which the DOE paid 60% of the whole.
Power shortages coupled with the Three-Mile Island nuclear accident (March 1979), made the mid-to-late Seventies a fertile setting for different vitality analysis. A month after the ERDA/NASA research started, President James Carter made ERDA part of the brand new Division of Power (DOE). Creation of the DOE was a part of a coverage bundle aimed toward U.S. vitality independence and “clear vitality.”
After Apollo, NASA had, regardless of its finest efforts, discovered itself and not using a clearly outlined mission for its piloted program aside from improvement of the Area Shuttle. SPS supporters within the aerospace neighborhood noticed within the idea an irresistible alternative for NASA to contribute to the answer of a urgent nationwide downside.
Improvement, deployment, and operation of SPSs would confront NASA with engineering issues far past any it had tackled earlier than. If an SPS was to contribute a significant quantity of electrical energy to the interlinked U.S. utility grids — and, by DOE’s reckoning, “significant” meant gigawatts — then it must be colossal by regular aerospace engineering requirements. The SPS silhouetted towards the Solar within the NASA paintings on the high of this put up (Picture 1) is typical: it could have measured 10.5 kilometers lengthy by 5.2 kilometers large and had a mass of fifty,000 tons.
Paired with a rectenna a few kilometers throughout, such an SPS would contribute 5 gigawatts to the U.S. electrical energy provide. DOE estimated that 60 such satellites with a complete producing capability of 300 gigawatts may contribute meaningfully to satisfying projected U.S. electrical energy demand within the 2000-2030 interval.
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| Picture 2. Picture credit score: Boeing/NASA. |
There was, in fact, no manner that NASA may launch such enormous satellites intact, and even in just a few modular components. It will must assemble the SPS fleet in area, almost certainly in GEO, from many components. This known as for an armada of extremely succesful area transport autos and a military of astronauts and automatic meeting machines.
The purple, white, and blue “Area Freighter” pictured within the Boeing portray above (Picture 2) was, as its identify implies, meant to function the primary cargo launcher for SPS building. Absolutely reusable to chop prices, it could have comprised at launch an automatic, delta-winged Booster with a piloted, delta-winged Orbiter on its nostril. After separating from the Orbiter, the Booster would have both landed downrange (if it have been launched from a web site in California, Arizona, New Mexico, or western Texas) or would have deployed turbofan engines and flown again to its launch web site.
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| Picture 3. Picture credit score: NASA. |
Had it been constructed, the Area Freighter would have completely outclassed all different launchers. Its Orbiter would have delivered as much as 420 metric tons of cargo to a staging base in low-Earth orbit (LEO). For comparability, the biggest single-launch U.S. Earth-orbital payload, the Skylab Orbital Workshop, weighed 77 metric tons. Skylab was launched on a two-stage Saturn V rocket on 14 Could 1973.
Engineers converse of “gross liftoff weight” (GLOW) once they describe giant launchers. The Area Shuttle had a GLOW of about 2040 metric tons and the three-stage Apollo Saturn V, about 3000 metric tons. Estimated GLOW for the Area Freighter was a whopping 11,000 metric tons.
Alert readers will discover discrepancies within the work that illustrate this put up. These happen as a result of the photographs are based mostly on design ideas developed by totally different engineers in several phases of the multi-year SPS examine. The delta-winged Boeing Area Freighter design, for instance, is totally different from the NASA Area Freighter design depicted within the illustration above (Picture 3).
The NASA Area Freighter has a Booster with some resemblance to a Saturn V S-IC stage; each the Booster and the Orbiter have skinny major wings and ahead canard fins. The Orbiter payload bay is positioned close to its entrance; not, as within the Boeing design, at mid-fuselage. Regardless of these variations, the NASA Area Freighter would have had the identical capabilities because the Boeing Area Freighter.
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| Picture 4. Picture credit score: NASA. |
The NASA portray above (Picture 4) depicts a hexagonal LEO staging base with a central “management tower.” Entry tubes hyperlink the management tower to docking modules on the hexagon’s six vertices. Between the entry tubes are color-coded triangular “marshaling yards” with socket-like bays for storing standardized NASA Area Freighter cargo containers.
The staging base management tower has mounted on its roof a “area crane” descended from the a lot smaller Area Shuttle Distant Manipulator System, which was underneath improvement on the time DOE and NASA performed their joint SPS examine. The management tower area crane is positioning a cargo container in order that an automatic chemical-propulsion Orbital Switch Automobile (OTV) can dock with it. After docking and area crane launch, the OTV would routinely transport the container to a building base in GEO.
One other, smaller area crane rides a monitor across the fringe of the hexagon. It’s proven unloading a cargo container from the newly docked Area Freighter Orbiter.
The portray consists of many different particulars. It exhibits, for instance, what seems to be a standard Area Shuttle Orbiter approaching the staging base within the background. Rockwell, prime contractor for the Area Shuttle, proposed that second-generation Area Shuttle Orbiters function devoted crew transports for the SPS program. The corporate envisioned that changing the Orbiter payload bay with a pressurized crew module would allow it to move as much as 75 astronauts at a time.
Subsequent to the crew transport is a cluster of cylindrical modules for housing the staging base crew and astronauts in transit between Earth and GEO. A piloted OTV for transporting astronauts to and from the GEO SPS work-site — similar to the automated OTV, aside from the presence of a pressurized crew module — is proven docked with the LEO staging base at decrease proper.
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| Picture 5. Picture credit score: NASA. |
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| Picture 6. Picture credit score: NASA. |
Within the SPS examine, NASA sought to stability automation and astronauts. Automation was, its engineers famous, good for repetitive actions reminiscent of fabricating the tens of kilometers of trusses wanted to assist SPS photo voltaic cell blankets.
The essential “beambuilder” depicted within the higher picture above (Picture 5) would flip tight rolls of skinny aluminum sheeting into sturdy single trusses. The extra advanced a number of beambuilder system within the decrease picture (Picture 6) would mix and hyperlink collectively single trusses to make the foremost structural members of the satellite tv for pc.
Astronauts would supervise and keep the beambuilder robots and be a part of collectively the trusses they fabricated. Automated OTVs would ship 1000’s of aluminum rolls to the GEO work-site, which the astronauts would then load into the beambuilders.
DOE and NASA anticipated to added two SPSs to the “fleet” in GEO every year beginning in 2000. Every SPS would want about 200 Area Freighter launches and a whole lot of OTV transfers between the LEO staging base and GEO. Propellants for the OTVs, in addition to 50 metric tons of orbit trim propellants for every SPS per yr, would demand much more Area Freighter launches.
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| Picture 7. Picture credit score: NASA. |
Regardless of in depth reliance on automation, the 30-year SPS challenge would require the presence of almost 1000 astronauts in area always. Most can be based mostly in GEO (Picture 7).
Along with building staff, personnel wanted in area would come with physicians, directors, OTV pilots, life assist engineers, common upkeep staff (“janitors”), cooks, area go well with tailors, and pc technicians. Personnel wanted on the bottom — on the launch/touchdown web site, on the rectennas, and at broadly scattered factories for manufacturing SPS components, OTVs, spares, foodstuffs, and propellants — would outnumber astronauts by at the least 10 to 1, NASA and DOE estimated. Constructing and working the SPSs may turn into a significant new U.S. business.
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| Picture 8. Picture credit score: NASA. |
As beambuilders and astronauts accomplished trusswork sections, automated OTVs would start to ship rolls of photo voltaic cell “blankets” to the SPS work-site. The NASA portray above (Picture 8) exhibits within the background an automatic OTV laden with bluish rolls of photo voltaic cell blankets (higher proper).
In the meantime, an automatic system feeds blanket sections to a piloted “cherry picker” on the finish of a small area crane. The cherry picker’s “pilot” — who wears solely shirt-sleeves in his pressurized cab — makes use of manipulator arms to hyperlink one finish of a photo voltaic cell blanket to a truss.
Greater than 50 sq. kilometers of photo voltaic cell blankets can be unfold over the trusswork of every SPS on this manner. The tip results of this intensive human and machine labor is depicted in idealized kind instantly beneath (Picture 9).
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| Picture 9. Picture credit score: NASA. |
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| Picture 10. Picture credit score: NASA. |
The decrease portray above (Picture 10) exhibits Glaser’s invention at work. The extraordinary daylight of area strikes photo voltaic cells, that are hidden from view (the picture does, nevertheless, present an excellent have a look at the bottom of a accomplished SPS). Tens of millions of silicon or gallium arsenide cells effectively convert the daylight into electrical energy.
The kilometer-wide steerable microwave transmission antenna on the decrease finish of the SPS converts the electrical energy into microwaves and focuses the microwave beam on a rectenna on Earth, almost 36,000 kilometers away. The beam seems within the illustration as a ghostly cone; in actuality, the microwaves can be invisible.
DOE and NASA envisioned constructing the 60 rectennas (Picture 11) required for the SPS system from coast to coast alongside the 35° latitude line. Cities on or close to that line embody Bakersfield, California; Flagstaff, Arizona; Albuquerque, New Mexico; Amarillo, Texas; Oklahoma Metropolis, Oklahoma; Little Rock, Arkansas; Memphis and Chattanooga, Tennessee; and Charlotte, North Carolina. If one flew between these cities, one would overfly rectennas on the bottom in several settings — forest, farm fields, mountains, swamp, desert — each 50 kilometers or so.
The Seventies noticed rising consciousness of environmental issues and the risks of terrorism. DOE and NASA took pains to hunt public enter in order that they may try and calm public fears. Most individuals polled fearful concerning the microwave beams linking the SPSs with their rectennas on Earth. Some expressed concern concerning the environmental influence of the beams, whereas others feared that terrorists may seize management of an SPS and switch its beam on a metropolis.
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| Picture 11. Picture credit score: NASA. |
NASA identified that the beam can be de-focused to cut back threat to the Earth’s higher environment, plane, and other people working on the rectennas. As depicted within the portray above, restricted agriculture may happen underneath the rectennas, instantly within the path of the microwave beams. As well as, the microwave transmitter on the SPS might be designed to close off routinely if its beam drifted. DOE and NASA anticipated that every rectenna would have round it a “buffer” zone of uninhabited land in order that if the beam drifted a small distance earlier than it turned off routinely, solely the ring-shaped buffer can be affected.
On this remaining picture of this put up (Picture 12), we see the SPS fleet close to the top of 2015; that’s, midway by way of the 30-year building program, when 30 satellites would kind a vibrant line throughout the southern evening sky as considered from the contiguous United States. A DOE doc defined that every satellite tv for pc would shine just a little brighter than Venus. The satellites would seem about as far aside because the three stars making up Orion’s belt. Broadly accessible 7 x 50 binoculars would reveal every satellite tv for pc’s rectangular form to Earth-bound observers.
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| Picture 12. Picture credit score: NASA. |
The string of satellites would stay nonetheless towards a background of transferring stars and planets. In actuality, in fact, the celebrities and planets would stay nonetheless relative to the rotating Earth and the SPSs would sustain with Earth’s rotation.
Each six months, on the time of the spring and autumn equinoxes, every SPS would cross by way of Earth’s shadow close to midnight for a number of days in succession. Throughout its transient shadow passage, a satellite tv for pc wouldn’t produce electrical energy. One after the other, beginning with the jap satellites, the SPSs would redden and develop darkish. After about 10 minutes in eclipse, every would return to its full brightness.
The DOE/NASA SPS research continued into the Administration of President Ronald Reagan, who took workplace in January 1981. In August 1981, the Congressional Workplace of Expertise Evaluation (OTA) printed a evaluate of SPS work carried out since 1976. The OTA’s evaluation of the viability of the idea was typically favorable. The Reagan Administration was, nevertheless, not passionate about electrical energy from area or, certainly, from any however typical sources.
The DOE/NASA SPS research constituted solely a tiny, low-priority portion of the area company’s whole actions. The primary Area Shuttle take a look at flight in April 1981, the primary American piloted area mission since July 1975, was, in fact, of far larger consequence.
With the primary Shuttle flight underneath its belt, NASA redoubled its efforts to construct assist for a Shuttle-launched Earth-orbital area station. The company sought to painting the Area Station as an area shipyard, a marshalling yard for area tugs and payloads, and a laboratory for exploitation of the distinctive qualities of area.
Finally, solely the laboratory perform would acquire assist, largely as a result of it could be less expensive than the shipyard and marshalling capabilities. Even that assist was grudging; although Reagan permitted the Station in January 1984, it could endure a collection of redesigns and wouldn’t be accomplished for greater than 20 years.
Sources
“Energy from the Solar: Its Future,” Peter Glaser, Science, Vol. 162, 22 November 1968.
Feasibility Examine of a Satellite tv for pc Photo voltaic Energy Station, NASA Contractor Report 2357, P. Glaser, O. Maynard, J. Mackovciak, and E. Ralph, February 1974.
Memorandum of Understanding Between the Power Analysis and Improvement Administration and the Nationwide Aeronautics and Area Administration, 23 June 1975.
The Photo voltaic Energy Satellite tv for pc Idea: The Previous Decade and the Subsequent Decade, JSC-14898, July 1979.
Some Questions and Solutions In regards to the Satellite tv for pc Energy System (SPS), DOE/ER-0049/1, U.S. Division of Power, Workplace of Power Analysis, Satellite tv for pc Energy System Mission Workplace, January 1980.
Satellite tv for pc Energy System Idea Improvement and Analysis Program, Quantity I: Technical Evaluation Abstract Report, NASA Technical Memorandum 58232, NASA Lyndon B. Johnson Area Heart, November 1980.
Photo voltaic Energy Satellites, Workplace of Expertise Evaluation, U.S. Congress, August 1981.
Extra Data
Think Big: A 1970 Flight Schedule for NASA 1969 Integrated Program Plan
Evolution vs. Revolution: The 1970s Battle for NASA’s Future