Geosynchronous Drift: Krafft Ehricke's Destination Mankind Apollo Mission (1972)

Apollo 17 launch, 7 December 1972. Image credit: NASA.

In May 1972, Krafft Ehricke, Executive Advisor in the Space Division of North American Rockwell Corporation, proposed that the last piloted lunar landing mission, Apollo 17, scheduled for the end of 1972, be postponed until the U.S. Bicentennial in July 1976 and dispatched to a new destination: a geosynchronous orbit (GSO) 22,300 miles above the Earth. An object in a GSO requires one day to complete one revolution of the Earth. Since Earth revolves in one day, an object in equatorial GSO appears to hang over one spot on the equator.

"The mission into geosynchronous orbit," Ehricke declared, would provide "additional return on America's investment in Apollo" by dramatizing "the usefulness of manned orbital activities." He added that his proposal, which he dubbed Destination Mankind, "would inspire many, as did the lunar missions before it, but in a different, perhaps more direct manner, because of its greater relevance to some of the most pressing problems of our time."

Ehricke's emphasis on practical benefits over lunar exploration reflected a significant shift in the public perception of spaceflight — one which had gained momentum throughout the 1960s. President Richard Nixon had articulated this shift in his "Statement About the Future of the United States Space Program" on 7 March 1970. The 37th President stated that he believed that the U.S. space program should proceed at a measured pace (not on "a crash timetable") and should be devoted to scientific exploration (mainly using interplanetary robots, but with man on Mars as a "longer-range goal").

In addition, NASA should emphasize international cooperation, cost reduction, and, crucially, "practical application — turning the lessons we learned in space to the early benefit of life on Earth." Nixon declared that results of space research should be "used to the maximum advantage of the human community." He listed among the practical applications of spaceflight "surveying crops, locating mineral deposits, and measuring water resources."

Ehricke described a representative 12-day Destination Mankind mission. Reaching GSO would require about as much propulsive energy as reaching lunar orbit, he noted. The three-stage Destination Mankind Apollo Saturn V rocket would lift off from Launch Complex 39 at Kennedy Space Center, Florida, at about 8:30 p.m. local time. Following first and second stage operation, the S-IVB third stage would fire briefly to place itself, the Apollo Command and Service Module (CSM), and a Payload Module (PM) into 100-nautical-mile parking orbit. Ehricke did not describe the PM design.

One orbital revolution (about 90 minutes) later, the S-IVB would ignite again to perform Transynchronous Injection (TSI). After S-IVB shutdown, the astronauts would separate their CSM and turn it 180° to dock with the PM, which would be attached to the top of the S-IVB in place of the Apollo Lunar Module (LM). They would then extract the PM, maneuver away from the S-IVB, and settle in for the 5.2-hour coast to GSO.

Deep Space Climate Observatory (DSCOVR) image of Africa, the Middle East, India, Europe, and adjacent seas and oceans. Cairo, close to the northern limit of the Destination Mankind Afro-Eurasian Station, is located near the center of the image. DSCOVR images Earth every two hours from Sun-Earth L1, not from geosynchronous orbit. Image credit: NASA.

The Destination Mankind CSM would ignite its Service Propulsion System (SPS) main engine to enter a GSO at 31° east longitude. This would place it over the equatorial nation of Uganda — if the CSM entered an equatorial GSO. The mission's GSO would, however, be inclined 28.5° relative to Earth's equator, so the CSM would oscillate between 28.5° south latitude (over South Africa's east coast) and 28.5° north latitude (southwest of Cairo) and back every 24 hours. The CSM would reach its southern limit at 10 a.m. local time and its northern limit at 10 p.m. local time. This 57°-long stretch of the 31° east longitude line would, Ehricke explained, constitute Destination Mankind's "Afro-Eurasian Station."

Destination Mankind mission objectives would fall into three general areas: science, technology, and public relations. Science objectives would draw upon an Apollo Geosynchronous Scientific Experiment Package (AGSEP) carried in the PM. The crew might assess the astronomical value of a GSO observatory, perform high-energy particle experiments, and observe and image the Earth. At the Afro-Eurasian Station, the astronauts could view Africa, Europe, the Middle East, Central Asia, and India. Earth imaging and observation might be conducted in collaboration with observers at "ground truth" sites on land and on ships at sea.

Ehricke emphasized the technology objectives of his Destination Mankind mission. He was particularly enamored of a solar illumination experiment that would see a circular reflector assembled by spacewalking astronauts. The experiment would provide reference data for design and operation of future space-based reflectors, he explained. He calculated that a 100-meter reflector in GSO could light Earth's surface one-tenth as brightly as a full Moon in a selected area. This level of illumination, though "subvisual," would be useful for night meteorology and surveillance of border and coastal areas, Ehricke wrote.

The astronauts would also erect "Manstar," a 500-to-700-foot-diameter reflective balloon visible over a wide area of Earth's surface as a modestly bright star. Ehricke called Manstar "a visible manifestation for all mankind of the potential value of space."

Ehricke called public relations "Public Exposure." Destination Mankind astronauts would become television stars. They would describe their Earth observations — "especially aspects useful and of interest to regional populations" — via TV broadcasts from GSO. Their spacewalks would also make for good TV fare, Ehricke judged.

Apollo 17 Command Module Pilot Ronald Evans retrieves film and data cassettes from the Scientific Instrument Module Bay built into the side of the Apollo 17 CSM America. His 17 December 1972 spacewalk was the last performed beyond low-Earth orbit. Ehricke's Destination Mankind mission would have included several spacewalks in GSO, where none has yet occurred. Image credit: NASA.

DSCOVR image of North America, South America, and Central America with adjacent oceans and seas. New Orleans, near the northern limit of the Destination Mankind Panamerican-Pacific Station, is located near the center of the image. Image credit: NASA.

The Destination Mankind CSM and PM would remain at the Afro-Eurasian Station for an unspecified period (perhaps two days), then the astronauts would fire the CSM's SPS to climb to a slightly higher orbit and begin a two-day "drift" westward across the Atlantic to their Panamerican-Pacific Station. Upon reaching their new station, located at 90° west longitude, the crew would fire the SPS to lower their orbit and halt their drift.

The CSM and PM would oscillate between 28.5° south (over the Pacific off northern Chile) and 28.5° north (over the Gulf of Mexico south of New Orleans), again reaching the southern limit at 10 a.m. local time and the northern limit at 10 p.m. local time. Equatorial crossing would occur above the Galapagos Islands. The astronauts would spend their time much as they did at the Afro-Eurasian Station, then would fire the SPS again to drift westward across the Pacific.

DSCOVR image of Australia, east Asia, east Africa, the Middle East, India, and adjacent bodies of water. The Destination Mankind Australo-Asian Station's southern limit would occur over the Indian Ocean off the coast of Perth, Australia, in the lower half of the image, just right of center. Image credit: NASA.

The last stop on the Destination Mankind crew's world tour would be the 98° east longitude line, which Ehricke dubbed the Australo-Asian Station. They would reach the north point in their south-north oscillation over southern China and the south point over the east Indian Ocean west of Perth. Near the end of their stay at the Australo-Asian Station, they would discard the PM.

The Destination Mankind crew would return to Earth from the Australo-Asian Station. Using the SPS, they would perform a Trans-Earth Injection burn as their CSM crossed the equator near Sumatra moving north at 4 p.m. local time. Fall to Earth would last 5.2 hours, and splashdown would occur in the Pacific west of Hawaii at just after 6 a.m. local time.

Sources

"Destination Mankind: Proposal for a Saturn V - Apollo Mission into Geosynchronous Orbit," K. Ehricke, North American Rockwell, 10 May 1972.

The American Presidency Project, "Statement About the Future of the United States Space Program," Richard Nixon, 7 March 1970 (http://www.presidency.ucsb.edu/ws/index.php?pid=2903&st=Future+of+the+United+States+Space+Program&st1= — accessed 14 April 2017).

More Information

"A Continuing Aspect of Human Endeavor": Bellcomm's January 1968 Lunar Exploration Program

Apollo's End: NASA Cancels Apollo 15 & Apollo 19 to Save Station/Shuttle (1970)

A Bridge from Skylab to Station/Shuttle: Interim Space Station Program (1971)

Reviving & Reusing Skylab in the Shuttle Era: NASA Marshall's November 1977 Pitch to NASA Headquarters

From Monolithic to Modular: NASA Establishes a Baseline Configuration for a Shuttle-Launched Space Station (1970)

Modular Shuttle-launched Station in the 1980s. Image credit: NASA.

On 22 July 1969, two days after Apollo 11's triumphant landing on the Moon's Sea of Tranquillity, NASA issued a pair of Phase B Space Station study contracts. One, under the direction of NASA's Marshall Space Flight Center (MSFC) in Huntsville, Alabama, went to McDonnell Douglas Corporation (MDC), while the other, under the direction of the Manned Spacecraft Center (MSC) in Houston, Texas, went to North American Rockwell (NAR).

Both companies looked at 33-foot-diameter, barrel-shaped "monolithic" stations. These were designed to be launched in one piece into low-Earth orbit atop a two-stage Saturn V rocket. Both companies assumed that a logistics vehicle — commonly called a Space Shuttle — would resupply the Station, rotate its six-to-12-man crews, deliver experiment equipment and small experiment modules, and return experiment results and experiment modules to Earth.

Plan drawing of NAR's Phase B "monolithic" Space Station design. Image credit: NAR/NASA/DSFPortree.

Elsewhere in this blog (see "More Information" at the bottom of this post) I have described the monolithic Space Stations and efforts in the early 1970s to preserve a Space Station Program in the face of rapidly shrinking NASA budgets and rapidly changing national priorities. In this post, I will describe a little-known study performed in-house by NASA personnel at MSC for the NASA Headquarters Space Station Task Force. The study helped to pave the way for a sea-change in Station planning in late July 1970.

In January 1970, as negotiations toward the Fiscal Year (FY) 1971 NASA budget got under way between NASA, President Richard Nixon's White House, and the Congress, NASA Administrator Thomas Paine announced that, to accommodate proposed funding cuts, NASA's Saturn V rocket test and assembly facilities would be mothballed. He was not specific about when this would happen, stating only that it would occur after the last Saturn V ordered for the Apollo Moon program — the fifteenth — was completed and tested. That was expected to occur before the end of 1971.

The Mississippi Test Facility at Bay St. Louis, home of test stands for Saturn V engines and rocket stages, would be hardest hit; from about 2000 its staff would shrink to from 150 to 200 "caretaker" personnel. The industry publication Aviation Week & Space Technology explained in its 9 February 1970 issue that, if NASA proceeded with these Saturn V plans and then received funding for new Saturn Vs in its FY 1972 budget, it would need four years to restore its assembly and test capabilities. The first Saturn V after the last Apollo Saturn V — the sixteenth — would not launch before July 1975.

On 4 May 1970, the Space Station Task Force asked MSFC and MSC to direct MDC and NAR to devote some attention during their Phase B studies — which were set to conclude in two months — to assessing a new method of launching the Space Station: specifically, by boosting it into Earth orbit in pieces in the payload bays of Space Shuttle Orbiters. At about the same time, MSC began to organize its in-house Shuttle-launched modular Station study, which commenced officially on 1 June 1970.

One ground rule of the MSC study was that the modular Station should be able to accomplish the same research objectives as its monolithic counterpart. Another was that MSC should seek to "exploit the unique capabilities of multiple Shuttle launches."

By June 1970, NASA had, in exchange for U.S. Air Force political support, largely settled on a 15-foot-by-60-foot payload bay for its winged Shuttle Orbiter design. Engineers at its Houston center had, however, not fully reconciled themselves to these payload bay dimensions. Some sought a shorter — and sometimes wider — payload bay.

The habitat modules they considered for their Space Station during June 1970 reflected this. They looked at five modules; then, in a second round of analysis, they emphasized four. The initial five measured 12 feet in diameter by 39.5 feet long; 12 feet in diameter by 29 feet long; 14 feet in diameter by 29 feet long; 16 feet in diameter by 22.2 feet long; and 18 feet in diameter by 17.4 feet long. The four "second-pass" modules measured 12.5 feet in diameter by 30 or 40.5 feet long; 14.5 feet in diameter by 30 feet long; 16.5 feet in diameter by 23.2 feet long; and 18.5 feet in diameter by 18.4 feet long.

MSC's four "second-pass" circular floor plan Shuttle-launched Space Station Modules. Image credit: NASA with dancing stick figures by DSFPortree.

MSC's four "second-pass" horizontal floor plan Shuttle-launched Space Station Modules. In this image and the image above, the stick figures indicate the positions of the floors in the modules, not necessarily the presence of artificial gravity. Image credit: NASA/DSFPortree.

MSC looked at both "horizontal" and "circular" floor plans for the four second-pass habitat modules. The former yielded a rectangular floor and ceiling aligned with the long axis of the module. Space above the ceiling and below the floor could hold supplies, spare parts, and equipment. The latter, a stack of floors, each as wide as the module's maximum internal diameter, tended to have more floors and less equipment space.

Module design Concept Selection took place on 1 July. MSC chose a horizontal habitat module 14 feet in diameter by 29 feet long, which could launch in a 15-foot-diameter Shuttle Orbiter payload bay as short as 30 feet long. MSC assumed that the module — which it called a Basic Structural Element (BSE) — would weigh about 8000 pounds empty and about 20,000 pounds fully outfitted.

MSC then included the selected habitat module concept in six modular Space Station configurations (shown below). Five of the six would provide their crews with a weightless living and working environment. All six would feature one Solar Power Boom with a pair of two-part solar arrays, one or two Central Assembly Element (CAE) core modules with 10 docking ports each, eight BSE modules, and two Expendables Storage Element (ESE) logistics and crew carriers. MSC calculated that all six modular configurations would provide roughly the same workspace as the NAR monolithic Station design.

Illustrations of four configurations MSC considered and then put aside are labeled 1 through 4 below. X, Y, and Z axes and Station ground tracks are indicated. The designs are of two classes: the Configuration 1 and 2 BSE modules form arms and the Configuration 3 and 4 BSE modules form bundles. In Configurations 3 and 4, a single nadir-facing plus-Z BSE module is provided for Earth-observation experiments.

On 15 July 1970, MSC engineers briefed the Space Station Task Group on its progress at NASA Headquarters. They included in their presentation — which, being an interim product, contains its share of internal inconsistencies — the four designs they had put aside plus a preliminary revolving artificial-gravity baseline design with a specialized telescoping CAE (fifth image above). Most of their presentation was, however, devoted to a preliminary assembly sequence for their baseline Shuttle-launched Station configuration (bottom image above — click to enlarge).

The baseline configuration illustration includes no ESE, though the modular Station would always operate with at least one — and often two — attached to CAE Y-axis ports. Though its length was not given, the ESE was described as shorter than the CAE, BSE, and Solar Power Boom modules.

The ESE was intended as a temporary Station module — it would ride into space inside a Shuttle Orbiter payload bay, then would transfer to a Station Y-axis port under its own propulsion bearing supplies, equipment, spare parts, and astronauts. It would remain docked with the Station after the Orbiter departed. While attached to the Station, it would serve as a "pantry" or "warehouse." It would later move under its own propulsion to another Shuttle payload bay bearing experiment results and astronauts for return to Earth. The ESE was the only module designed to dock with the Station under its own power.

Shuttle Orbiters would dock the Solar Power Boom, BSE, and CAE modules with the Station. All three module types would include a docking port at either end. After reaching orbit, the Orbiter crew would pivot the module out of the payload bay and, using one of its end ports, attach it to a docking port atop the Orbiter cabin. They would then rendezvous with the Station and dock with it using the port at the module's other end. When time came to return to Earth, the Orbiter would undock from the module, leaving it attached to the Station.

MSC estimated that 14 Shuttle flights would be needed to launch and assemble its baseline modular Station. The first flight would place into Earth orbit 20,412-pound CAE 1 (labeled 1 on the drawing). CAE 1 would have nothing yet with which to dock, so it would be released directly from the Orbiter payload bay without first linking to the docking port atop the Orbiter crew cabin. It would include electricity and propulsion systems that would keep it operational until Shuttle flight 2.

The second Shuttle flight would see a 19,351-pound ESE dock with one of the two plus-Y CAE 1 ports, giving the growing Station an "L" configuration. It would provide electricity and propulsion for the CAE 1-ESE combination, and would carry food sufficient for 12 men for 90 days. It would, however, carry no astronauts.

Shuttle flight 3 would see the 19,154-pound Solar Power Boom (3) join to the CAE 1 plus-X end port (the end port nearest the docked ESE). Its solar arrays (2) would unfurl after the Shuttle Orbiter that delivered it moved away, This would block the Boom's plus-X docking port (4) and double the Station's length.

Shuttle flight 4 would place into space the first BSE, a 17,209-pound module containing the Station's main control & science data processing facilities. It would be attached to the CAE 1 minus-Y port nearest the Solar Power Boom; that is, to the Y-axis port on the opposite side of CAE 1 from the ESE. It is not shown in the baseline configuration illustration above; an arrow, however, marks the port to which the first BSE would be docked. Except for the Solar Power Boom and the one or two CAEs, the Shuttle flight 4 BSE would be the only permanent module not docked to a CAE Z-axis port.

Shuttle flights 5 through 8 would also deliver BSE modules. Module placement would alternate between minus-Z and plus-Z CAE 1 ports. A pair of robot arms on CAE 1 would aid Shuttle astronauts in safely docking the closely spaced BSEs.

Shuttle flight 5 would place in orbit a 20,605-pound BSE containing mainly life support and personal hygiene equipment (5). This would bring total Station mass to 96,731 pounds.

Shuttle flight 6 would deliver a 20,302-pound BSE outfitted with crew staterooms and communications equipment (6). Shuttle flight 7, midway through the assembly sequence, would attach to the Station a lightweight (13,367-pound) BSE containing crew recreation and dining facilities and a galley (7).

The Shuttle flight 8 module, a BSE dedicated to crew health and biomedical studies (8), would also be a lightweight (13,324 pounds). Its arrival at the Station would signal completion of one of the modular Station's two redundant, independently pressurized volumes. MSC's modular Station would at that point be equivalent to two decks, an equipment bay, and the Solar Power Boom of the NAR monolithic Station. It would weigh 143,724 pounds.

Redundant, independent volumes reflected the Station's crew safety philosophy. If one volume became uninhabitable, the entire crew could retreat to the second volume to await an Orbiter that would provide repair assistance or rescue. The modular Station would not be permanently staffed until both volumes were completed.

Shuttle launches 9 through 14 would boost into space the Station's second redundant, independent volume. It would be equivalent to a monolithic Station equipment bay and two more decks.

Shuttle flight 9 would place into space the 18,645-pound second CAE (9), the plus-X end port of which would be attached to the CAE 1 minus-X port. This would enable attachment of four more Z-axis BSEs. The MSC team did not specify whether CAE 2 would include its own pair of robot arms or if it would use the pair launched on CAE 1. Shuttle flight 10's 16,395-pound BSE would include a maintenance shop and laboratory space (10), while Shuttle flight 11's 19,024-pound BSE would contain a general-purpose lab (11).

The Shuttle flight 12 BSE would provide backup Station control & data processing (12). Like its twin delivered during Shuttle flight 4, it would weigh 17,209 pounds. The payload for Shuttle flight 13 would be a 15,756-pound BSE containing crew quarters (13).

Shuttle flight 14 would complete MSC's baseline modular Station. An Orbiter would release from its payload bay a 20,551-pound ESE containing the Station's first six long-term resident astronauts and food for 12 men for 90 days. Like the first ESE, the second ESE is not shown in the drawing above; it would, however, be attached to the CAE 2 Y-axis port marked on the drawing by a star. With the addition of the 14th Shuttle payload, Station mass would total 251,304 pounds.

MSC Baseline Shuttle-Launched Station Assembly Sequence

1. Shuttle flight 1: CAE 1
2. Shuttle flight 2: ESE 1 (to CAE 1 +Y port)
3. Shuttle flight 3: Solar Power Boom (to CAE +X port)
4. Shuttle flight 4: BSE 1 (to CAE 1 -Y port)
5. Shuttle flight 5: BSE 2 (to CAE 1 -Z port)
6. Shuttle flight 6: BSE 3 (to CAE 1 +Z port)
7. Shuttle flight 7: BSE 4 (to CAE 1 -Z port)
8. Shuttle flight 8: BSE 5 (to CAE 1 +Z port)
9. Shuttle flight 9: CAE 2 (to CAE 1 -X port)
10. Shuttle flight 10: BSE 6 (to CAE 2 -Z port)
11. Shuttle flight 11: BSE 7 (to CAE 2 +Z port)
12. Shuttle flight 12: BSE 8 (to CAE 2 -Z port)
13. Shuttle flight 13: BSE 9 (to CAE 2 +Z port)
14. Shuttle flight 14: ESE 2 (to CAE 2 -Y port)

The image at the top of this post (click to enlarge) shows MSC's modular Station as it would appear by the mid-1980s. It would include at least five more BSEs than the baseline configuration. Four would link to the Z-axis ports of a third CAE attached to the CAE 2 minus-X port.

In the painting, an ESE makes an appearance: it includes a pair of robot arms. One of the four BSE modules attached to CAE 3 is a dedicated Earth-observation module (an open round end-hatch and extended instruments are visible below the ESE arms).

Two BSEs are shown attached to Y-axis CAE ports; one is the BSE delivered during Shuttle flight 4 (it is displayed here attached to the CAE 1 plus-Y port nearest the Solar Power Boom rather than the minus-Y port), while the other, attached to a CAE 2 minus-Y port, is probably a temporarily docked free-flyer with an independent propulsion system. This would detach from the Station periodically to provide a stable platform for materials science and astronomy experiments; such experiments could be adversely affected by vibration caused by crew movement within the Station.

The approaching Shuttle Orbiter is an MSC design with straight wings a little more than 90 feet across, internal liquid oxygen and liquid hydrogen tanks, twin main engines, and a payload bay shorter than 60 feet. It bears atop its crew compartment, attached to its docking port, a BSE module - probably another freeflyer, or perhaps a temporary attached lab - bound for a CAE Y-axis port.

After its 15 July presentation at NASA Headquarters, the MSC team apparently halted its activities. The artificial-gravity baseline design, for example, seems not to have been developed further. I have found no evidence that briefings scheduled for 1 August and 7 September at MSC and 15 September at NASA Headquarters actually took place.

NASA extended the NAR and MDC Space Station Phase B contracts by six months on 30 June 1970. On 29 July 1970, Charles Mathews, chair of the Space Station Task Force, requested that MSC and MSFC direct their respective Phase B contractors to expend more effort to study Shuttle-launched modular designs. This direction became formal on 1 February 1971, when NAR and MDC began Phase B Extension studies almost entirely focused on modular designs. When unveiled in late 1971, the NAR modular design resembled the baseline design from MSC's May-July 1970 in-house study.

Acronyms

BSE = Basic Structural Element
CAE = Central Assembly Element
ESE = Expendables Storage Element
MDC = McDonnell Douglas Corporation
MSC = Manned Spacecraft Center
MSFC = Marshall Space Flight Center
NAR = North American Rockwell

Sources

Shuttle-Launched Space Station Study Interim Review, NASA Manned Spacecraft Center presentation to NASA Headquarters, 15 July 1970.

"Curtailing Field Centers Limits Saturn 5 Options," Aviation Week & Space Technology, 9 February 1970, pp. 26-27.

"Space Station and Space Platform Concepts: A Historical Overview," J. Logsdon and G. Butler, History of Space Stations and Space Platforms - Concepts, Designs, Infrastructure, and Uses, I. Bekey and D. Herman, editors, Volume 99, Progress in Astronautics and Aeronautics, American Institute of Aeronautics and Astronautics, 1985, pp. 226-233.

Space Shuttle: The History of the National Space Transportation System - The First 100 Flights, Third Edition, D. Jenkins, Specialty Press, 2008, pp. 101-108, 137.

More Information

A Bridge from Skylab to Station/Shuttle: Interim Space Station Program (1971)

An Alternate Station/Shuttle Evolution: The Spirit of '76 (1970)

Apollo's End: NASA Cancels Apollo 15 & Apollo 19 to Save Station/Shuttle (1970)

McDonnell Douglas Phase B Space Station (1970)

Think Big: A 1970 Flight Schedule for NASA's 1969 Integrated Program Plan

"A True Gateway": Robert Gilruth's June 1968 Space Station Presentation

Electricity from Space: The 1970s DOE/NASA Solar Power Satellite Studies

Image 1 (see callout in text). Image credit: NASA.

Of all the many spaceflight concepts NASA has studied with any degree of seriousness, probably the most enormous was the Solar Power Satellite (SPS) fleet. Czech-born physicist/engineer Peter Glaser outlined the concept in a brief article in the esteemed journal Science in November 1968, and was awarded a patent for his invention on Christmas Day 1973.

Glaser had noticed that a satellite in geosynchronous Earth orbit (GEO), 35,786 kilometers above the equator, would pass through Earth's shadow for only a few minutes each year. It was well known that a satellite in equatorial GEO moves at the same speed the Earth rotates at the equator (1609 kilometers per hour). This means that, for people on Earth's surface, the satellite appears to hang motionless over one spot on the equator. Glaser also understood that electricity did not have to travel through wires; it could be beamed from a transmitter to a receiver.

Glaser mixed these three ingredients and came up with a satellite in equatorial GEO that would use solar cells to convert sunlight into electricity, convert the electricity into microwaves, and beam the microwaves at a receiving antenna (rectenna) on Earth. The rectenna would turn the microwaves back into electricity, then wires would carry it to the electric utility grid.

The great advantage an SPS enjoyed over a solar array on Earth's surface was, as mentioned, that it would spend almost no time in Earth's shadow. Earth's rotation meant that an Earth-surface solar array could make electricity at most about half the time. The rest of the time it would sit dormant under the night sky.

NASA and its contractors displayed low-level interest in the SPS concept as early as 1972. Early work took place at the Jet Propulsion Laboratory and NASA Lewis Research Center (now NASA Glenn), as well as at Arthur D. Little, a Cambridge, Massachusetts-based engineering firm of which Glaser was a Vice President. The level of effort increased in 1973, after the Organization of Petroleum Exporting Countries imposed an oil embargo to punish the U.S. and other industrialized nations for their support of Israel in the 1973 Yom Kippur War. By 1976, NASA Johnson Space Center in Houston, Texas, and NASA Marshall Space Flight Center in Huntsville, Alabama, led SPS studies within the space agency.

In June 1975, NASA and the Energy Research and Development Administration (ERDA) signed a Memorandum of Understanding calling for joint SPS research. ERDA began to plan an SPS study with NASA at the beginning of Federal Fiscal Year 1977 (October 1976), in the waning days of Gerald Ford's caretaker Presidency. The three-phase study began in July 1977. Total cost of the joint SPS studies, which were meant to last for three years, was $15.6 million, of which the DOE paid 60% of the total.

Energy shortages coupled with the Three-Mile Island nuclear accident (March 1979), made the mid-to-late 1970s a fertile environment for alternative energy research. A month after the ERDA/NASA studies began, President James Carter made ERDA a part of the new Department of Energy (DOE). Creation of the DOE was part of a policy package aimed at U.S. energy independence and "clean energy."

After Apollo, NASA had, despite its best efforts, found itself without a clearly defined mission for its piloted program other than development of the Space Shuttle. SPS supporters in the aerospace community saw in the concept an irresistible opportunity for NASA to contribute to the solution of a pressing national problem.

Development, deployment, and operation of SPSs would confront NASA with engineering problems far beyond any it had tackled before. If an SPS was to contribute a meaningful amount of electricity to the interlinked U.S. utility grids — and, by DOE's reckoning, "meaningful" meant gigawatts — then it would have to be colossal by normal aerospace engineering standards. The SPS silhouetted against the Sun in the NASA artwork at the top of this post (Image 1) is typical: it would have measured 10.5 kilometers long by 5.2 kilometers wide and had a mass of 50,000 tons.

Paired with a rectenna a couple of kilometers across, such an SPS would contribute five gigawatts to the U.S. electricity supply. DOE estimated that 60 such satellites with a total generating capacity of 300 gigawatts could contribute meaningfully to satisfying projected U.S. electricity demand in the 2000-2030 period.

Image 2. Image credit: Boeing/NASA.

There was, of course, no way that NASA could launch such huge satellites intact, or even in a few modular parts. It would need to construct the SPS fleet in space, most likely in GEO, from many parts. This called for an armada of highly capable space transport vehicles and an army of astronauts and automated assembly machines.

The red, white, and blue "Space Freighter" pictured in the Boeing painting above (Image 2) was, as its name implies, meant to serve as the main cargo launcher for SPS construction. Fully reusable to cut costs, it would have comprised at launch an automated, delta-winged Booster with a piloted, delta-winged Orbiter on its nose. After separating from the Orbiter, the Booster would have either landed downrange (if it were launched from a site in California, Arizona, New Mexico, or western Texas) or would have deployed turbofan engines and flown back to its launch site.

Image 3. Image credit: NASA.

Had it been built, the Space Freighter would have utterly outclassed all other launchers. Its Orbiter would have delivered up to 420 metric tons of cargo to a staging base in low-Earth orbit (LEO). For comparison, the largest 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 May 1973.

Engineers speak of "gross liftoff weight" (GLOW) when they describe large launchers. The Space Shuttle had a GLOW of about 2040 metric tons and the three-stage Apollo Saturn V, about 3000 metric tons. Estimated GLOW for the Space Freighter was a whopping 11,000 metric tons.

Alert readers will notice discrepancies in the paintings that illustrate this post. These occur because the images are based on design concepts developed by different engineers in different phases of the multi-year SPS study. The delta-winged Boeing Space Freighter design, for example, is different from the NASA Space Freighter design depicted in the illustration above (Image 3).

The NASA Space Freighter has a Booster with some resemblance to a Saturn V S-IC stage; both the Booster and the Orbiter have skinny main wings and forward canard fins. The Orbiter payload bay is located near its front; not, as in the Boeing design, at mid-fuselage. Despite these differences, the NASA Space Freighter would have had the same capabilities as the Boeing Space Freighter.

Image 4. Image credit: NASA.

The NASA painting above (Image 4) depicts a hexagonal LEO staging base with a central "control tower." Access tubes link the control tower to docking modules at the hexagon's six vertices. Between the access tubes are color-coded triangular "marshaling yards" with socket-like bays for storing standardized NASA Space Freighter cargo containers.

The staging base control tower has mounted on its roof a "space crane" descended from the much smaller Space Shuttle Remote Manipulator System, which was under development at the time DOE and NASA conducted their joint SPS study. The control tower space crane is positioning a cargo container so that an automated chemical-propulsion Orbital Transfer Vehicle (OTV) can dock with it. After docking and space crane release, the OTV would automatically transport the container to a construction base in GEO.

Another, smaller space crane rides a track around the edge of the hexagon. It is shown unloading a cargo container from the newly docked Space Freighter Orbiter.

The painting includes many other details. It shows, for example, what appears to be a conventional Space Shuttle Orbiter approaching the staging base in the background. Rockwell, prime contractor for the Space Shuttle, proposed that second-generation Space Shuttle Orbiters serve as dedicated crew transports for the SPS program. The company envisioned that replacing the Orbiter payload bay with a pressurized crew module would enable it to transport up to 75 astronauts at a time.

Next 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 — identical to the automated OTV, except for the presence of a pressurized crew module — is shown docked with the LEO staging base at lower right.

Image 5. Image credit: NASA.

Image 6. Image credit: NASA.

In the SPS study, NASA sought to balance automation and astronauts. Automation was, its engineers noted, good for repetitive actions such as fabricating the tens of kilometers of trusses needed to support SPS solar cell blankets.

The basic "beambuilder" depicted in the upper image above (Image 5) would turn tight rolls of thin aluminum sheeting into sturdy single trusses. The more complex multiple beambuilder system in the lower image (Image 6) would combine and link together single trusses to make the major structural members of the satellite.

Astronauts would supervise and maintain the beambuilder robots and join together the trusses they fabricated. Automated OTVs would deliver thousands of aluminum rolls to the GEO work-site, which the astronauts would then load into the beambuilders.

DOE and NASA expected to added two SPSs to the "fleet" in GEO each year starting in 2000. Each SPS would need about 200 Space Freighter launches and hundreds of OTV transfers between the LEO staging base and GEO. Propellants for the OTVs, as well as 50 metric tons of orbit trim propellants for each SPS per year, would demand even more Space Freighter launches.

Image 7. Image credit: NASA.

Despite extensive reliance on automation, the 30-year SPS project would require the presence of nearly 1000 astronauts in space at all times. Most would be based in GEO (Image 7).

In addition to construction workers, personnel needed in space would include physicians, administrators, OTV pilots, life support engineers, general maintenance workers ("janitors"), cooks, space suit tailors, and computer technicians. Personnel needed on the ground — at the launch/landing site, at the rectennas, and at widely scattered factories for manufacturing SPS parts, OTVs, spares, foodstuffs, and propellants — would outnumber astronauts by at least 10 to 1, NASA and DOE estimated. Building and operating the SPSs could become a major new U.S. industry.

Image 8. Image credit: NASA.

As beambuilders and astronauts completed trusswork sections, automated OTVs would begin to deliver rolls of solar cell "blankets" to the SPS work-site. The NASA painting above (Image 8) shows in the background an automated OTV laden with bluish rolls of solar cell blankets (upper right).

Meanwhile, an automated system feeds blanket sections to a piloted "cherry picker" at the end of a small space crane. The cherry picker's "pilot" — who wears only shirt-sleeves in his pressurized cab — uses manipulator arms to link one end of a solar cell blanket to a truss.

More than 50 square kilometers of solar cell blankets would be spread over the trusswork of each SPS in this way. The end result of this intensive human and machine labor is depicted in idealized form immediately below (Image 9).

Image 9. Image credit: NASA.

Image 10. Image credit: NASA.

The lower painting above (Image 10) shows Glaser's invention at work. The intense sunlight of space strikes solar cells, which are hidden from view (the image does, however, provide a good look at the backside of a completed SPS). Millions of silicon or gallium arsenide cells efficiently convert the sunlight into electricity.

The kilometer-wide steerable microwave transmission antenna at the lower end of the SPS converts the electricity into microwaves and focuses the microwave beam on a rectenna on Earth, nearly 36,000 kilometers away. The beam appears in the illustration as a ghostly cone; in reality, the microwaves would be invisible.

DOE and NASA envisioned building the 60 rectennas (Image 11) required for the SPS system from coast to coast along the 35° latitude line. Cities on or near that line include Bakersfield, California; Flagstaff, Arizona; Albuquerque, New Mexico; Amarillo, Texas; Oklahoma City, Oklahoma; Little Rock, Arkansas; Memphis and Chattanooga, Tennessee; and Charlotte, North Carolina. If one flew between these cities, one would overfly rectennas on the ground in different settings — forest, farm fields, mountains, swamp, desert — every 50 kilometers or so.

The 1970s saw growing awareness of environmental problems and the dangers of terrorism. DOE and NASA took pains to seek public input so that they could attempt to calm public fears. Most people polled worried about the microwave beams linking the SPSs with their rectennas on Earth. Some expressed concern about the environmental impact of the beams, while others feared that terrorists might seize control of an SPS and turn its beam on a city.

Image 11. Image credit: NASA.

NASA pointed out that the beam would be de-focused to reduce risk to the Earth's upper atmosphere, aircraft, and people working at the rectennas. As depicted in the painting above, limited agriculture could take place under the rectennas, directly in the path of the microwave beams. In addition, the microwave transmitter on the SPS could be designed to shut off automatically if its beam drifted. DOE and NASA expected that each rectenna would have around it a "buffer" zone of uninhabited land so that if the beam drifted a small distance before it turned off automatically, only the ring-shaped buffer would be affected.

In this final image of this post (Image 12), we see the SPS fleet near the end of 2015; that is, halfway through the 30-year construction program, when 30 satellites would form a bright line across the southern night sky as viewed from the contiguous United States. A DOE document explained that each satellite would shine a little brighter than Venus. The satellites would appear about as far apart as the three stars making up Orion's belt. Widely available 7 x 50 binoculars would reveal each satellite's rectangular shape to Earth-bound observers.

Image 12. Image credit: NASA.

The string of satellites would remain still against a background of moving stars and planets. In reality, of course, the stars and planets would remain still relative to the rotating Earth and the SPSs would keep up with Earth's rotation.

Every six months, at the time of the spring and autumn equinoxes, each SPS would pass through Earth's shadow near midnight for several days in succession. During its brief shadow passage, a satellite would not produce electricity. One by one, starting with the eastern satellites, the SPSs would redden and grow dark. After about 10 minutes in eclipse, each would return to its full brightness.

The DOE/NASA SPS studies continued into the Administration of President Ronald Reagan, who took office in January 1981. In August 1981, the Congressional Office of Technology Assessment (OTA) published a review of SPS work performed since 1976. The OTA's assessment of the viability of the concept was generally favorable. The Reagan Administration was, however, not enthusiastic about electricity from space or, indeed, from any but conventional sources.

The DOE/NASA SPS studies constituted only a tiny, low-priority portion of the space agency's total activities. The first Space Shuttle test flight in April 1981, the first American piloted space mission since July 1975, was, of course, of far greater consequence.

With the first Shuttle flight under its belt, NASA redoubled its efforts to build support for a Shuttle-launched Earth-orbital space station. The agency sought to portray the Space Station as a space shipyard, a marshalling yard for space tugs and payloads, and a laboratory for exploitation of the unique qualities of space.

Ultimately, only the laboratory function would gain support, in large part because it would be less costly than the shipyard and marshalling functions. Even that support was grudging; though Reagan approved the Station in January 1984, it would undergo a series of redesigns and would not be completed for more than 20 years.

Sources

"Power from the Sun: Its Future," Peter Glaser, Science, Vol. 162, 22 November 1968.

Feasibility Study of a Satellite Solar Power Station, NASA Contractor Report 2357, P. Glaser, O. Maynard, J. Mackovciak, and E. Ralph, February 1974.

Memorandum of Understanding Between the Energy Research and Development Administration and the National Aeronautics and Space Administration, 23 June 1975.

The Solar Power Satellite Concept: The Past Decade and the Next Decade, JSC-14898, July 1979.

Some Questions and Answers About the Satellite Power System (SPS), DOE/ER-0049/1, U.S. Department of Energy, Office of Energy Research, Satellite Power System Project Office, January 1980.

Satellite Power System Concept Development and Evaluation Program, Volume I: Technical Assessment Summary Report, NASA Technical Memorandum 58232, NASA Lyndon B. Johnson Space Center, November 1980.

Solar Power Satellites, Office of Technology Assessment, U.S. Congress, August 1981.

More Information

Think Big: A 1970 Flight Schedule for NASA 1969 Integrated Program Plan

Evolution vs. Revolution: The 1970s Battle for NASA's Future

NASA Johnson's Plan to PEP up Shuttle/Spacelab (1981)

Rube Goldberg's Space Shuttle

By mid-1971, this was one of the two leading Space Shuttle design configurations. The first stage, bearing the letters "USA" and a single stabilizing oversized tail fin, might have been derived from the Saturn V S-IC first stage. Image credit: NASA.

For Americans above a certain age, the phrase "Rube Goldberg Machine" elicits a chuckle or perhaps a sneer, depending on the context of its use. Rube Goldberg (1883-1970) was an award-winning cartoonist. His most famous drawings were of whimsical machines that accomplished a simple task in the most complex way possible.

It is not too unkind, given that most of the factors that led to its complexity were outside of NASA's control, to place the Space Shuttle in the category of a Rube Goldberg Machine. It began as a simple idea — economically deliver crews, supplies, and equipment to an Earth-orbiting Space Station — and, through conflicting, expanding demands placed on it, unwise cuts in funding for its development, and deferral of the Space Station it was meant to serve, grew into something large, complex, and costly.

Throughout the Space Shuttle design process, NASA fought a rearguard action to preserve reusability. In 1969, the U.S. civilian space agency sought a fully reusable Shuttle design with a piloted Booster and a piloted Orbiter, each carrying liquid propellants for placing the Orbiter into Earth orbit. Inadequate funding support from the Nixon White House and Congress coupled with a U.S. Air Force requirement that the Orbiter include a payload bay at least 60 feet long and 15 feet wide soon made that design untenable, however.

NASA and its contractor teams took a rapid series of cost-cutting steps during 1970-1972. The design process became messy and almost untrackable, with concepts proposed, abandoned, and proposed again in rapid succession or even simultaneously by different contractor and NASA teams.

The piloted Booster shrank after engineers tacked a pair of reusable solid-propellant rocket motors onto its tail. Then it ceased to be piloted, becoming part of what amounted to a three-stage rocket. Riding bolted to the top or side of the Booster's expendable second stage, the piloted Orbiter became in effect a reusable third stage that would complete its climb to Earth orbit by burning liquid hydrogen (LH2) fuel and liquid oxygen (LOX) oxidizer carried in tanks inside its streamlined fuselage.

In part to prevent the Orbiter from growing out of all proportion as its payload bay grew, NASA moved low-density LH2 out of the Orbiter fuselage into cheap expendable drop tanks. The move also ended worries about safe containment within the Orbiter of volatile LH2, which is prone to slow seepage even through solid metal.

The Orbiter carried LOX for its ascent to orbit inside its fuselage for a little while longer. By August 1971, however, the delta-winged Orbiter contained only enough propellants to maneuver in orbit and to slow itself so that it could deorbit and reenter Earth's atmosphere. At first, its orbital maneuvering engines were expected to burn LH2/LOX, but then NASA substituted hypergolic (ignite-on-contact) propellants.

During the same period, the preferred Shuttle stack design flip-flopped between two candidates. One (image at top of post) had two LH2/LOX stages stacked one atop the other. The first-stage engines were mounted directly beneath their stage, as on a conventional rocket. The engines for the second stage were built into the tail of the Orbiter mounted on its side. They would ignite at altitude after the first stage separated and, owing to their position on the side of the second stage, would thrust off center.

The first stage would be reusable; after depleting its propellants and separating from the second stage, it would deploy parachutes and lower to a gentle landing at sea, where it would bob with its engines pointed at the sky. A specially designed ship would then recover it and tow it to port for refurbishment. The second stage would reach orbit attached to the Orbiter, then would separate, reenter, and break up over the ocean.

The other candidate design (image below) featured a reusable Orbiter and a pair of reusable LH2/LOX boosters mounted on the sides of a single large expendable External Tank (ET). The lightweight ET's interior would be split between a small tank for LOX and a large one for LH2. Both the twin boosters and the tail-mounted Orbiter engines would ignite on the launch pad. The side-mounted boosters would expend their propellants and fall away about two minutes after liftoff. They would each deploy parachutes and descend to a gentle ocean landing to await recovery. Pipes leading from the ET tanks would feed propellants to the Orbiter's engine cluster throughout ascent to orbit.

That looks familiar: the other Space Shuttle stack design leading the pack by mid-1971. Note off-center thrust plumes from the delta-winged Orbiter's tail-mounted engines (lower left). Image credit: NASA.

In a final cost-cutting move, NASA replaced the reusable liquid-propellant boosters with reusable solid-propellant boosters. The liquid-propellant boosters could be turned off in the event of a major malfunction; the solid-propellant boosters could not.

Mounting engines on the reusable Orbiter meant that they would be returned to Earth for refurbishment and reuse. The resulting off-center thrust troubled many engineers, however, because it meant that thrust forces would be transmitted through the Orbiter to the second stage (in the case of the first Shuttle design alternative) or the ET (in the case of the second). This would place added stress on the Orbiter, its links to the second stage or ET, and the second stage or ET. Links between the second stage/ET and the Orbiter would include propellant pipe connections, which engineers expected would be prone to leaks even without the added stress of off-center thrust.

Off-center thrust also meant that the short LOX tank, when full the heaviest part of the second stage or ET, had to be situated atop the long LH2 tank, the lightest part of the second stage or ET. Putting the dense LOX on top helped the Shuttle stack to remain stable in flight as the Orbiter's engines rapidly emptied the second stage or ET and the stack's center of gravity shifted, but it also placed added stress on the second stage or ET structure. Because the LOX at the top of the second stage/ET needed a long pipe to reach the engines on the Orbiter's tail, the arrangement also increased the risk of propellant pipe rupture.

During the 1970-1972 Shuttle design evolution, several engineers proposed and re-proposed a novel alternative to off-center thrust: a cluster of reusable engines that would operate attached to the bottom of the expendable second stage or ET. After the Orbiter reached Earth orbit and its main engines shut down, the engine cluster would be detached from the second stage or ET and, using an armature system of booms or struts, be swung into a storage compartment inside the aft end of the Orbiter fuselage.

The second stage or ET would then be cast off. In the case of the ET, vented residual propellants would cause it to tumble, rapidly reenter the atmosphere, and break up. When the astronauts on board the Orbiter completed their mission in Earth orbit, the engine cluster would return to Earth with them, where it would be removed from the compartment, refurbished, and mounted on a new second stage or ET.

The NASA Manned Spacecraft Center — renamed the Lyndon B. Johnson Space Center (JSC) in February 1973 — managed Space Shuttle development. Shuttle engineers were quick to reject the swing-engine design. They did this mainly because its armature system seemed overly complex and thus prone to malfunctions.

The Rube Goldbergian swing-engine concept would not die, however. In March 1974, in fact, JSC chief of engineering Maxime Faget (co-designer of the Mercury capsule and a 1969 all-reusable Shuttle) and JSC engineers William Petynia and Willard Taub filed an application to patent the swing-engine design. By then, the decision to settle on the second stack configuration described above was two years old (NASA Administrator James Fletcher announced the choice on 16 March 1972).

The JSC engineers proposed three swing-engine design approaches. The U.S. Patent Office granted their patent on 30 December 1975.

All of their design approaches would, they argued, eliminate stress on the Shuttle stack caused by off-center thrust, enable transposition of the ET LOX and LH2 tanks, and improve stack flight characteristics during ascent through Earth's atmosphere. The results would, they explained, include a lighter Orbiter and ET, more payload, and greater safety.

As a bonus, the swing-engine system would enable the Orbiter to adjust its center of gravity after it released or took on an orbital payload, thus improving its reentry and atmospheric gliding flight characteristics. It would do this by shifting the engine cluster forward toward the back of the Orbiter payload bay using the same mechanical armature system that would swing the engines away from the bottom of the ET. The armature system would also serve to gimbal (swivel) the engines to steer the Orbiter/ET stack during ascent to orbit.

Other benefits would spring from the swing-engine design. The ET and engine cluster could be tested together without an Orbiter attached. All piping linking the Orbiter and the ET would be eliminated. Separable links between the ET and the engine cluster would be required, of course. The engine cluster would, however, be quite small and light compared to the Orbiter; this meant that it could be easily mounted on the ET, tested for leaks, and (if necessary) removed and repaired before flight.

First method for transferring engine cluster from aft end of the ET to storage in the Orbiter aft fuselage. 1 = ET; 2A = mounting ring for four engines (in thrust position on ET); 2B = mounting ring for four engines (in stored position in Orbiter aft fuselage); 3 = joint linking lower armature to engine ring (1 of 2); 4 = lower armature strut (1 of 2); 5 = upper armature strut (1 of 2); 6 = joint linking upper armature to Orbiter aft fuselage (1 of 2); 7 = trailing edge of wing (1 of 2); 8 = opening in aft fuselage for engine cluster storage; 9 = solid-propellant ascent abort rocket (1 of 2); 10 = vertical stabilizer. Image credit: NASA/U.S. Patent Office.

The JSC engineers' first swing-engine design, illustrated above, assumed a quartet of Shuttle engines, a single vertical stabilizer, and an aft-pointing fuselage opening. The armature system would swing the engines into the fuselage so that their engine bells pointed aft.

The second design, illustrated below, assumed three Space Shuttle engines in a vertical row and an Orbiter with twin out-splayed vertical stabilizer fins. The armature system would swing the engines up and over the aft end of the Orbiter fuselage and lower them into a rectangular slot between the fins. After a horizontal landing on Earth, their engine bells would point skyward.

Second method for transferring the Space Shuttle engine cluster from the aft end of the ET to the storage space in the Orbiter aft fuselage. 1 = Orbiter payload bay; 2 = LOX tank in aft end of ET; 3 = ET; 4 = vertical stabilizer (1 of 2); 5A = engine cluster in thrust position on aft end of External Tank; 5B = engine cluster in stowed position in Orbiter aft fuselage; 6A = centerline of engine cluster in thrust position; 6B = centerline of engine cluster in stowed position; 7A = armature strut for transferring engine cluster (thrust position) (1 of 2); 7B = armature strut for transferring engine cluster (stowed position) (1 of 2); 8 = center armature joint (1 of 2); 9 = path of center armature joint (8) during engine cluster transfer to stowed position. Image credit: NASA/U.S. Patent Office.

The JSC engineers' third swing-engine design also assumed three engines arranged in a vertical row, but could be used with either single or double vertical stabilizer Orbiter configurations. The armature system would tilt the engine cluster 45° and slide it on rails into a rear-facing opening in the aft fuselage. As with their second design, the engine bells would point upward after the Orbiter glided to a landing.

Orbital Flight Test-1 (OFT-1), also known as Space Transportation System-1 (STS-1), the first flight of the Space Shuttle. Columbia lifted off from Launch Complex 39A at Kennedy Space Center, Florida, on 12 April 1981, and landed at Edwards Air Force Base, California, two days later. Veteran astronaut John Young was Commander and rookie Robert Crippen was Pilot. Image credit: NASA.

The swing-engine concept had, of course, become a mere curiosity well before the U.S. Patent Office granted Faget, Petynia, and Taub their December 1975 patent. Following the March 1972 selection of the Shuttle stack configuration, NASA awarded Rockwell International the contract to build Space Shuttle Orbiters on 26 July 1972. The company built a total of five space-worthy Orbiters, each with three Space Shuttle Main Engines mounted in a triangle on their aft fuselages, over a span of more than 20 years.

The Orbiters functioned admirably, though they needed far more costly refurbishment and maintenance than NASA envisioned when it proposed its all-reusable Space Shuttle design in 1968-1969. Booster system malfunctions claimed two Orbiters and their seven-person crews, however. Challenger was destroyed on 28 January 1986 when a solid-propellant booster field joint burned through, leading to ET structural failure and Orbiter break-up 73 seconds after launch. Columbia, the first Orbiter to orbit Earth (12-14 April 1981), was lost after foam insulation on the ET it rode broke loose during ascent and struck and damaged its wing leading edge. This led to wing structural failure and Orbiter breakup during reentry on 1 February 2003, at the end of a 16-day mission.

Sources

Patent No. 3,929,306. Space Vehicle System, Maxime A. Faget, William W. Petynia, and Willard M. Taub, NASA Johnson Space Center, 5 March 1974 (filed), 30 December 1975 (granted).

Space Shuttle: The History of the National Space Transportation System, the First 100 Missions, Dennis R. Jenkins, 3rd Edition, 2008.

Wikipedia: Rube Goldberg Machine (https://en.wikipedia.org/wiki/Rube_Goldberg_machine — accessed 28 November 2016)

More Information

George Landwehr von Pragenau's Quest for a Stronger, Safer, Better Space Shuttle

Series Development: A 1969 Plan to Merge Saturn V and Shuttle to Spread Out Space Program Cost

One Space Shuttle, Two Cargo Volumes: Martin Marietta's Aft Cargo Carrier (1982)

George Landwehr von Pragenau's Quest for a Stronger, Safer Space Shuttle

The Space Shuttle Challenger and its booster system moments before they were destroyed. The plume of flame emerging from the side of its malfunctioning SRB is clearly visible. Image credit: NASA.

The Space Shuttle Orbiter Challenger was minding its own business on 28 January 1986, working hard to get its seven-member crew and its large satellite payload to low-Earth orbit, when its booster stack betrayed it and everything began to go badly wrong. First, hot gas within its right Solid Rocket Booster (SRB) began to burn through a seal meant to contain it. Soon, a fiery plume gushed from the side of the SRB, robbing it of thrust, and reached out menacingly toward the side of the brown External Tank (ET) and the strut linking the lower end of the SRB to the ET (image at top of post). The plume broke though the ET's foam insulation and aluminum skin, then the strut pulled free of the weakened ET.

Challenger fought back as the ET began to leak liquid hydrogen fuel. It swiveled (the aerospace term is "gimballed") the three Space Shuttle Main Engines (SSMEs) in its tail as it struggled to stay on course. The plume from the SRB, meanwhile, glowed brighter as it began to burn hydrogen leaking from the ET. At the same time, the SRB began to rotate around the single strut left holding it to the ET. That strut was located not far from the Orbiter's gray nose, near the conical top of the errant SRB.

Throughout these events, Challenger's last crew remained oblivious to the technological drama taking place around them. This was just as well, since they had no way to escape what was about to happen to them.

When Challenger at last lost its struggle against its own booster stack, significant events were separated by tenths or hundredths of seconds. Immediately after the right SRB's lower strut came free, the entire Shuttle stack lurched right. Mike Smith, in Challenger's pilot seat, had time for a startled "Uh-oh" less than a second after the lurch. The ET's dome-shaped bottom then fell away, freeing all the hydrogen fuel it contained. The right SRB's pointed nose slammed into and crushed the top of the ET, freeing liquid oxygen oxidizer. The escaped hydrogen blossomed into a fireball that encompassed Orbiter, rapidly disintegrating ET, and SRBs.

Yet the Orbiter Challenger did not explode. Instead, it broke free of what was left of the ET and began a tumble. The aerodynamic pressures the Orbiter experienced as its nose pointed away from its direction of flight were more than sufficient to snap it into several large pieces: the crew cabin, the satellite payload, the wings, and the SSME cluster emerged from the fireball more or less intact. The SRBs, still firing, flew out of the fireball, tracing random trails across the blue Florida sky until a range safety officer commanded them to self-destruct. The Orbiter's wreckage, meanwhile, plummeted into the Atlantic within sight of the Florida coast.

NASA recovered the bodies of the crew and portions of the wreckage, including the section of the right SRB that had leaked hot gas. The wreckage was turned over to accident investigators.

This 1975 NASA illustration depicts the basic components of the Space Shuttle system. The Orbiter includes three Space Shuttle Main Engines (left). Two Solid Rocket Boosters, one of which is mostly hidden behind the External Tank, provide thrust during liftoff and the early part of ascent. The tank includes (from right to left) a small tank for dense liquid oxygen, a drum-shaped structural support ring/tank separator below the Orbiter's nose, and a large tank for low-density liquid hydrogen.

During a Shuttle launch, the three SSMEs ignited first. This caused the twin SRBs, the bases of which were mounted to the launch pad by explosive bolts, to flex along their entire length away from the SSMEs, then straighten out again just as they ignited. O-ring seals between the cylindrical segments making up the SRBs often became unseated during flexure, then had to reseat to contain hot gases after SRB ignition. Accident investigators concluded that failure of one of those seals doomed Challenger. Even more damning, they found that partial seal failures followed by hot exhaust leaks had occurred on pre-Challenger flights — and had been disregarded by NASA managers.

After Challenger, NASA and its contractors redesigned the SRB joints and seals, added crew pressure suits and a limited crew escape capability, and banned potentially unsafe practices and payloads from Shuttle missions. Yet the U.S. civilian space agency might have gone much farther when it sought to enhance Space Shuttle safety after Challenger.

Even before the accident, NASA had at its disposal redesign proposals that could have made the Shuttle stack stronger and safer. In 1982, for example, George Landwehr von Pragenau, a veteran engineer at NASA's Marshall Space Flight Center, filed a patent application — granted in 1984 — for a Shuttle stack design that would have made the Challenger accident impossible.

Born and educated in Austria, von Pragenau joined the von Braun rocket team in Huntsville, Alabama, in 1957. He became a U.S. citizen in 1963. He specialized in rocket stability and flight effects on rocket behavior. He had, for example, been part of the team that found the cause of the "pogo" oscillations that crippled Apollo 6, the second unmanned Saturn V-launched Apollo test mission (4 April 1968).

In the conventional Shuttle stack, von Pragenau explained, SRB thrust was transmitted through the forward SRB attachment points to a reinforced intertank ring between the ET's top-mounted liquid oxygen tank and its liquid hydrogen tank.  He considered this "indirect routing" of thrust loads to be perilously complex. SSME thrust loads, for their part, passed through the Orbiter to its twin aft ET attachment points on the large, fragile liquid hydrogen tank.

By the time he filed his 1982 patent application, von Pragenau had spent almost a decade thinking about how the Shuttle stack might be rearranged to reduce weight and aerodynamic drag, increase stability, simplify thrust paths, and provide greater structural strength. His 1984 patent was, in fact, not his first aimed at Shuttle improvement.

Von Pragenau's 1974 alternative Shuttle stack. Image credit: U.S. Patent Office.

In 1974, von Pragenau had filed a patent — granted the following year — in which he proposed a more slender, more vertically oriented Shuttle stack; that is, one that would mimic conventional rocket designs in which stages are stacked one atop the other. He linked the twin SRBs side by side. Moving the tank for dense liquid oxygen from the ET's nose to its tail placed its concentrated mass nearer the base of the stack, improving in-flight stability. He then mounted the SRBs to the Orbiter's belly and perched the ET atop the SRB/Orbiter combination. SRB and SSME thrust loads were conveyed through struts to meet at the ET's flat, reinforced base.

Von Pragenau's 1982 Shuttle stack design was in some ways a less radical departure from the existing Shuttle design than was his 1974 design. He left the SRBs, ET, and Orbiter in their normal positions relative to each other, but made other significant changes. As in his 1975 patent, he moved the liquid oxygen tank from the ET's nose to its tail and brought the SRBs closer together to improve stability. The liquid oxygen tank became skinny, cylindrical, and almost as long as the Orbiter and SRBs attached to it. The liquid hydrogen tank, fat with low-density fuel, von Pragenau mounted atop the oxygen tank, partially overhanging the Orbiter and SRBs.

Von Pragenau's 1982 Shuttle stack redesign. The numeral "15" points to the rigid thrust structure framework. "34," "35," "36" are Solid Rocket Booster attachment fixtures. These would link to slide rails ("31" and "32") that would run the length of the liquid oxygen tank ("20"). "19" is the liquid hydrogen tank. Image credit: U.S. Patent Office. 

Von Pragenau could not tolerate flexing SRBs. He proposed to mount a slide rail on either side of the liquid oxygen tank. Three attachment fixtures on each SRB would link to the slide rails, helping to ensure rigidity. When the SRBs depleted their propellant, pyrotechnic bolts would fire, freeing them to slide backwards down the rails and fall neatly away from the Orbiter/ET stack.

The most important feature of von Pragenau's redesign was a rigid framework – a thrust structure – that would link the bottom of the SRBs just above their rocket nozzles. In addition to holding the SRBs rigidly in place, the thrust structure would transmit SRB thrust loads to the bottom of the ET oxygen tank, which would rest atop the center of the thrust structure. When the spent SRBs slid away from the Orbiter/ET stack, they would take the thrust structure with them.

Side view of Von Pragenau's 1982 Shuttle stack concept. Image credit: U.S. Patent Office.

Von Pragenau's concepts apparently exerted little influence on NASA's post-Challenger recovery effort. A likely explanation is that neither of his proposals — if they were known to decision-makers at all — was deemed affordable. In addition to extensive changes in manufacturing tooling, both proposals would have required modifications to the Vehicle Assembly Building, the twin Complex 39 Shuttle pads at Kennedy Space Center (KSC), and even the barge that delivers ETs to KSC. Instead of beefing up the existing Shuttle, NASA studied designs for new shuttles which, for lack of funding, remained firmly in the low-cost realm of CAD drawings, conference papers, and conceptual artwork.

On 1 February 2003, the Space Shuttle claimed another crew. The oldest Orbiter, Columbia, was heavier than her sisters Atlantis, Discovery, and Endeavour, which limited the amount of cargo she could deliver to the International Space Station (ISS). For this reason, NASA largely relegated to Columbia the few remaining non-ISS missions — for example, Hubble Space Telescope servicing.

As they began Earth-atmosphere reentry at 8:44 a.m. Eastern Standard Time after a nearly 16-day life sciences mission, the seven STS-107 astronauts on board Columbia were unaware that, during ascent, a piece of ice-impregnated insulating foam nearly a meter wide had broken free from the ET and impacted their spacecraft's left wing. Ice and foam had broken free from ETs before, but the damage they caused was, after cursory examination, deemed acceptable by Shuttle Program managers. This time, however, the impact opened a hole up to 10 inches wide in the Orbiter's left wing leading edge.

Hot plasma generated during reentry entered the hole and began to destroy Columbia's left wing from the inside out. Observers along the Orbiter's flight path, which cut across the southern tier of U.S. states, reported unusual flashes. Meanwhile, members of the STS-107 crew on Columbia's Flight Deck observed and recorded on video flashes visible outside their windows. In the recovered video, the astronauts appear to realize that the flashes were unusual but show no signs of panic.

Much as Challenger had before it, Columbia fought bravely against the forces destroying it. Onboard computers took account of increased drag on the left side of the Orbiter and sought to compensate to keep it on the flight path. At 8:59 a.m. Eastern Standard Time, however, Columbia tumbled and disintegrated over northeast Texas.

Both of von Pragenau's design concepts placed all or part of the ET above the Orbiter, so one might argue that they would not have prevented a failure resembling that which killed the STS-107 crew. On the other hand, one can be forgiven for speculating that a U.S. civilian space agency provided with the means after Challenger to rebuild the Shuttle system to make it safer might also have evolved an organizational culture more prone to investigating and less prone to tolerating recurring flight anomalies.

Von Pragenau retired from NASA in 1991 after more than 30 years of service. He remained involved in engineering efforts at NASA Marshall Space Flight Center during his retirement. He died two years after the Space Shuttle's final flight (STS-135, 8-24 July 2011), on 11 July 2013, at the age of 86.

Sources

Patent No. 4,452,412, Space Shuttle with Rail System and Aft Thrust Structure Securing Solid Rocket Boosters to External Tank, George L. von Pragenau, NASA Marshall Space Flight Center, 15 September 1982 (filed), 5 June 1984 (granted).

Patent No. 3,866,863, Space Vehicle, George L. von Pragenau, NASA Marshall Space Flight Center, 21 March 1974 (filed), 18 February 1975 (granted).

Hampton Cove Funeral Home Obituaries: George Landwehr von Pragenau (http://www.hamptoncovefuneralhome.com/fh/obituaries/obituary.cfm?o_id=2150841&fh_id=13813 — accessed 27 October 2016).

NASA History: Columbia Accident Investigation Board (http://history.nasa.gov/columbia/CAIB.html — accessed 29 October 2016).

NASA History: Challenger STS 51-L Accident (https://www.hq.nasa.gov/office/pao/History/sts51l.html — accessed 29 October 2016).

More Information

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What if a Space Shuttle Orbiter Had to Ditch? (1975)

What If Galileo Had Fallen to Earth? (1988)