Starfish and Apollo (1962)

9 July 1962: An artificial aurora lights the sky over the Pacific Ocean following the Starfish Prime space nuclear explosion. Image credit: U.S. Air Force.

Since I first posted a less detailed version of this post on my old Romance to Reality website (1996-2006), the Starfish Prime nuclear test has become a popular topic on the Internet. On 9 July 1962, the U.S. Air Force launched a 2200-pound W-49 nuclear warhead into space on a Thor rocket from Johnston Atoll in the Pacific Ocean. The warhead exploded with a yield of 1.44 megatons of TNT at an altitude of 248 miles above the Pacific.

The Starfish Prime nuclear blast produced a flash of light visible over much of the Pacific basin. For seven minutes after the explosion, an artificial red aurora danced in the skies over island groups as widely separated as Hawaii, Tonga, and Samoa. The blast's electromagnetic pulse damaged electrical systems on the Hawaiian island of Oahu, 800 miles away from the explosion.

Starfish Prime, a follow-on to U.S. high-altitude nuclear tests conducted in 1958, was publicized in advance. Many widely scattered aircraft and naval vessels, as well as sounding rockets, were used to observe its effects.

Though it sought answers to scientific questions, it was intended also to test whether nuclear explosions in low-Earth orbit (LEO) could augment and expand the Earth-girdling Van Allen radiation belts to create a barrier that would incapacitate Soviet intercontinental missiles launched against the United States. The test series of which it was part, Operation Dominic, was partly a response to the Soviet Union's August 1961 decision to end a three-year nuclear testing moratorium.

Schematic cross-section of the inner and outer Van Allen Belts based on James Van Allen's 1958 model. In February 2013, NASA announced that data from the two Van Allen Probes indicated that a third radiation belt can sometimes form beyond the outer belt. Image credit: Wikipedia.

High-energy particles Starfish Prime pumped into the belts probably contributed to the failure of Telstar 1 just four months after its 10 July 1962 launch. Telstar 1 was the first active communications satellite, meaning that it received and re-transmitted incoming radio signals. The satellite was reacquired in January 1963, but failed permanently on 21 February. Six other satellite failures have been traced to Starfish Prime.

No one knew how long the beefed-up radiation belts might persist. Some feared that the increased radiation might last until 1967-1968, when NASA hoped to carry out the first Apollo expedition to the Moon. The Apollo spacecraft, launched from Cape Canaveral on Florida's east coast, would have to traverse the augmented Van Allen Belts, and no one could say what effect their radiation would have on Apollo crews.

A Bell Labs technician puts the finishing touches on the experimental multi-national Telstar 1, the world's first privately sponsored satellite. A Thor-Delta rocket boosted the 170-pound satellite into a 592-by-3687-mile Earth orbit the day after the Starfish Prime nuclear explosion. Image credit: Bell Laboratories.

D. James and H. Schulte, researchers with NASA's newly created advance planning contractor, Bellcomm, analyzed the effects of Starfish Prime on NASA Moon plans in a memorandum they sent to NASA Headquarters on 5 October 1962. It was among the first of many memos and reports Bellcomm would supply to NASA over the decade that followed.

James and Schulte based their analysis of the LEO radiation environment during the first Apollo mission on a model of the post-Starfish Prime Van Allen belts developed by NASA Goddard Space Flight Center scientist Wilmot Hess. His model placed the lower limit of the expanded inner Van Allen belt at an altitude of about 600 miles.

Just two days after Starfish Prime, NASA announced that, after more than a year of sometimes heated discussion, it had selected the Lunar-Orbit Rendezvous (LOR) mission mode for accomplishing Apollo Moon landings. LOR would see lunar mission functions split between two manned spacecraft — a large command ship and a small Moon lander. The command ship would come no closer to the Moon than lunar orbit. The lander would operate independently only during descent to the Moon's surface, on the surface, and during ascent to lunar orbit.

LOR mission plan. Please click to enlarge. Step 10 shows the lunar lander separating from the command ship; 11 and 12 show the lander descending and on the surface; 13 and 14 show the lander ascent stage climbing to lunar orbit and docking with the command ship; and 15 shows the ascent stage being cast off and the command ship firing its engine to leave lunar orbit and fall back to Earth. Image credit: NASA.

LOR had won out over Earth-Orbit Rendezvous (EOR) because it promised to reduce the mass of the lunar spacecraft, enabling launch on a single Saturn C-5 rocket (as the Saturn V was known in 1962), and because it would make the moon lander small compared to the EOR lander and thus safer to land. EOR needed multiple Earth launches and landed the entire piloted lunar spacecraft on the Moon.

Despite NASA's decision, James and Schulte examined the radiation environment for both LOR and EOR Apollo missions. This reflected lingering anxiety both inside and outside NASA concerning LOR.

Many worried that the LOR mission mode's namesake maneuver, the post-lunar landing rendezvous and docking between the command ship and the Moon lander in lunar orbit, might prove too challenging. They worried in particular that, with Earth's ground-based tracking stations too far away to be of use, the spacecraft in lunar orbit would have difficulty finding each other. If, during Apollo development, this were found to be so, then an EOR backup plan would become necessary.

In James and Schulte's EOR scenario, NASA would launch a single large piloted lunar spacecraft with mostly empty propellant tanks into LEO. There it would rendezvous and dock with a separately launched automated tanker containing its LEO departure propellants.

James and Schulte assumed that, before an EOR Apollo spacecraft could set out for the Moon, it would need to orbit the Earth at least six times in a 252-mile-high parking orbit inclined 28.5° relative to Earth's equator (28.5° is the latitude of launch facilities on Cape Canaveral). During its first orbit after launch, controllers on the ground would track the piloted EOR Apollo to determine its precise path.

Rendezvous and docking with the tanker would need up to 2.5 orbits, then propellant transfer and final orbit determination/spacecraft checkout would require two more. After a final half-orbit, the EOR Apollo's orbital motion would have caused its orbital plane to become aligned for launch to near-equatorial landing sites on the Moon. It would then ignite its engines to depart LEO.

The Bellcomm planners determined that, based on the Hess model, the EOR Apollo astronauts would receive a radiation dose of four rad in LEO before setting out for the Moon. They would experience most of their LEO radiation exposure during orbits five and six, when they would begin to pass through a magnetic field anomaly that spans the Atlantic from Brazil to South Africa.

NASA Goddard Space Flight Center illustration of the South Atlantic Anomaly.

Within the South Atlantic Anomaly, as it is known today, the Van Allen belts dip to within 100 miles of Earth's surface. If the EOR Apollo astronauts could not depart LEO on schedule, then they would pass through the widest part of the South Atlantic Anomaly during orbits seven, eight, nine, and 10, and would receive up to six rads per orbit.

LOR Apollo would, by contrast, not linger in LEO. James and Schulte assumed that the LOR Apollo spacecraft/LEO-departure booster combination would circle Earth once in 252-mile-high LEO while controllers precisely tracked it to determine its orbit. It would then complete half an orbit more so that its orbital plane would align for departure to near-equatorial landing sites on the Moon.

The LOR Apollo crew would stay far from the South Atlantic Anomaly during their one and a half orbits of the Earth. Because of this, their radiation dose in LEO from the augmented Van Allen belts would amount to only 0.02 rad.

In both the LOR and EOR modes, the astronauts would receive a dose of 16 rad while crossing the Starfish Prime-augmented Van Allen belts en route to the Moon. Thus, the minimum dose the EOR astronauts would receive would be 20 rad, while LOR astronauts would receive 16.02 rad.

The Bellcomm planners noted that future nuclear explosions in LEO could dramatically boost the dose Moon-bound astronauts would receive during Van Allen belt passage. They added that a nuclear bomb packed with Uranium-238 could increase radiation in the belts "a hundredfold."

James and Schulte noted that the Van Allen belts are inclined relative to Earth's equator and do not cover its poles. If the belts became impassable, they wrote, NASA would have little choice but to launch Apollo astronauts through the Van Allen belt gaps over the poles.

Unfortunately, Cape Canaveral was poorly placed for polar launches because rockets launched due south or north would pass over populated areas. These included Cuba and Brazil to the south and the major cities of the U.S. eastern seaboard to the north.

James and Schulte wrote that a country with polar launch capability might explode nuclear weapons in space to bar a nation without such capability from launching men to the Moon. They did not mention the Soviet Union specifically, nor did they point out that the Soviet Union, with its extensive Arctic Ocean coastline, was well placed to carry out polar launches.

The Van Allen radiation belts returned to normal a few years after Starfish Prime. Nuclear explosions in space never menaced Apollo astronauts, in large part because on 5 August 1963, representatives of the U.S., Great Britain, and the Soviet Union met in Moscow to sign the Treaty Banning Nuclear Weapon Tests in the Atmosphere, Outer Space, and Under Water.

Conclusion of the treaty, which needed more than eight years to negotiate, very likely received some impetus from Starfish Prime. The treaty, which permitted only underground nuclear tests on Earth and sought to curtail spread of nuclear test fallout, entered into force on 10 October 1963, and has subsequently been signed by nearly all United Nations member countries.

Sources

Memorandum, D. James and H. Schulte, Bellcomm, to W. Lee, NASA Headquarters, "Radiation environment of EOR and LOR," Bellcomm, October 5, 1962.

"The Artificial Radiation Belt Made on July 9, 1962," W. Hess, Journal of Geophysical Research, Volume 68, Number 3, 1 February 1963, pp. 667-683.

Wikipedia - "Starfish Prime" (https://en.wikipedia.org/wiki/Starfish_Prime - accessed 9 January 2016).

Wikipedia - "Telstar" (https://en.wikipedia.org/wiki/Telstar - accessed 12 January 2016).

U.S. Department of State - "Treaty Banning Nuclear Weapon Tests in the Atmosphere, Outer Space, and Under Water" (http://www.state.gov/t/isn/4797.htm - accessed 12 January 2016)

More Information

What If Apollo Astronauts Became Marooned in Lunar Orbit? (1968)

What If Apollo Astronauts Could Not Ride the Saturn V Rocket? (1965)

Space Race: The Notorious 1962 Plan to Launch an Astronaut on a One-Way Trip to the Moon

Solar Flares and Moondust: The 1962 Proposal for an Interdisciplinary Science Satellite at Earth-Moon L4

He Who Controls the Moon Controls the Earth (1958)

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

 24 July 1969: Richard Nixon and Thomas Paine (left), NASA's third Administrator, wait on board the aircraft carrier Hornet for splashdown of the Command Module Columbia at the end of the Apollo 11, the first mission to land men on the Moon. At the time, Paine was lobbying hard for Nixon's acceptance of the IPP. Image credit: NASA.

When one reads of NASA's 1969 Integrated Program Plan (IPP), it is often difficult to know whether to laugh or cry. The IPP, a product of George Mueller's NASA Headquarters Office of Manned Space Flight, began to evolve as early as 1965, but not until May 1969 did it take on the grandiose form NASA Administrator Thomas Paine stubbornly advocated to President Richard Nixon.

Paine, a Washington neophyte who had replaced the politically wily James Webb in late 1968, expected that the IPP would be NASA's reward for vanquishing the Soviet Union in the race to the Moon. He urged his Center directors across the country to "think big" in their plans for post-Apollo space projects.

Had NASA gained approval for its Integrated Program Plan in 1969, a vast network of space transportation systems, space stations, and surface bases might have been in place by 1984. Image credit: NASA.

In its various versions, the IPP included space stations in low-Earth orbit (LEO), geosynchronous orbit (GEO), and near-polar lunar orbit; Saturn V and Saturn V-derived rockets for launching them; a fully reusable Earth-to-LEO Space Shuttle for launching astronauts, cargo, and propellants; a reusable modular Space Tug that could operate with or without a crew and do double-duty as a Lunar Module-B (LM-B) Moon lander; a reusable Nuclear Shuttle for LEO-GEO and LEO-lunar orbit transportation; and lunar and Mars surface bases. All of this complex and expensive infrastructure was meant to become operational by the mid-1980s at the latest.

The IPP is sometimes wrongly attributed to Wernher von Braun, director of NASA's Marshall Space Flight Center (MSFC) in Huntsville, Alabama. Von Braun was in fact skeptical about the IPP. He did not expect an Apollo-level commitment to spaceflight following Apollo's culmination, let alone one several times larger. He had spent the 1960s seeking opportunities to expand U.S. piloted spaceflight using his Saturn rocket family. By the time Apollo 11 Commander Neil Armstrong set foot on the Moon (20 July 1969), however, it was abundantly clear to the pragmatic German-born rocketeer that this would not happen.

Nevertheless, with his position rapidly eroding in the new political climate, von Braun at Paine's request tasked MSFC's artists with pumping out IPP illustrations and its advance planners with grafting a piloted Mars mission onto the up-to-then cislunar IPP. He then touted the Mars plan to Nixon's high-level Space Task Group (STG) on 4 August 1969. Paine called von Braun NASA's "Big Gun" and expected the STG to be bowled over by anything he put before them. The first NASA piloted Mars mission could leave Earth as early as 1981, von Braun told the STG in a 30-minute presentation.

Nixon had appointed the STG in February 1969 to provide him with alternatives for NASA's future. Paine, a member of the STG, had won over Vice President Spiro Agnew, the STG's chairman, enabling him to put forward the IPP as the only choice for NASA's future. The STG's September 1969 report offered Nixon three schedules for accomplishing the IPP, but that was not the same as providing the three program alternatives Nixon had requested. Paine might have offered Nixon a choice between an LEO space station, a lunar base, or a man on Mars. Instead, he insisted on a package containing all three.

This was, of course, an ill-considered move. Nixon's Office of Management and Budget had made it clear that NASA should expect rapidly declining annual budgets, not rapidly increasing ones. Nixon interpreted Paine's stubborn advocacy of the ambitious IPP as a clumsy effort at bureaucratic empire-building, not as a sincere proposal for a bold ("swashbuckling" was a term Paine used) American space program.

Paine's inflexibility created a vacuum that the Nixon Administration filled. NASA had supplied a single plan for its future that was unacceptable, so the White House made its own plan that served the President's political ends.

First, before accepting the STG report in September 1969, the White House added a fourth IPP schedule with no fixed dates. Nixon then adopted the line that IPP development would proceed as funding became available with the goal of a man on Mars by the year 2000, a date so far in the future as to be meaningless.

Next, in July 1970, a year after Apollo 11, Nixon accepted Paine's resignation effective on the first anniversary of the STG report's public release (15 September 1970), and replaced him with the much more pliant James Fletcher. Finally, on 5 January 1972, Nixon made the Space Shuttle the sum total of NASA's post-Apollo piloted program. He touted the aerospace jobs it would create in California, a state vital to his 1972 reelection bid.

5 January 1972: President Richard Nixon and NASA's fourth Administrator, James Fletcher, in California with a model of the Space Shuttle. The Space Shuttle was the only element of the IPP to fly, and then only in a partially reusable form. It first reached orbit on 12 April 1981. Image credit: NASA.

Before that fateful announcement, however, NASA expended considerable effort on planning the IPP's execution. Paine's resignation did not stop the study efforts immediately. The LEO Station and Shuttle received more attention than the other elements because they were viewed together as the IPP's first step, but planners continued to look at all elements of the IPP well into 1971.

In June 1970, E. Grenning, an engineer with Bellcomm, NASA's Washington, DC-based advance planning contractor, developed a "traffic model" (basically, a flight schedule) based on a modified version of Paine's IPP Option I (the so-called "Maximum Program"). Grenning's model spanned the years 1970 through 1984.

Grenning explained that the IPP was based on two fundamental principles. These were "the systematic establishment of semi-permanent manned bases in various locations in cislunar space and eventually in interplanetary space" and the "parallel introduction of low cost transportation systems. . . for the purpose of economically moving cargo and personnel to and from the bases."

A major change from the IPP as submitted to Nixon was that the piloted Mars program, which would span seven years, was not tied to any specific dates. Grenning explained, however, that, when the decision was taken to proceed with the piloted Mars program, its seven-year schedule would need to be tied to existing Earth-Mars minimum-energy transfer opportunities, which occur every 26 months.

Another change was that Grenning listed proposed automated planetary exploration missions. This was a response to protests from scientists, who were understandably eager to explore the many types of worlds in the Solar System. The "Balanced Base" planetary program would include 21 missions, all of which would leave Earth between 1976 and 1984.

In addition, Grenning stretched the pre-Mars IPP over a slightly longer period, so that its elements would not all be in place until 1984. Combined with not providing a specific date for its man-on-Mars program, this made Grenning's traffic model for Option I somewhat more conservative than the one in the STG report. It was, however, more conservative only relative to the grandiose Option I Paine championed.

Until 1975, Grenning's model was based wholly on Apollo spacecraft and Saturn rockets, none of which were reusable. Because it used no reusable vehicles and established no permanent bases, it was simple in execution compared with the traffic model that began to take hold in 1975.

The year 1970 would see three Apollo Moon-landing missions, Grenning wrote, each with three astronauts, a Command and Service Module (CSM), and a Lunar Module (LM) launched on a three-stage Saturn V rocket. They would constitute the continuation of the Apollo lunar landing missions that had begun with Apollo 11. It is interesting to note here that Grenning's model, dated June 1970, seemed to exist in a parallel universe; after the Apollo 13 accident in April 1970, Apollo was grounded until January 1971.

The year 1971 would see the first two Extended Apollo missions. An uprated Saturn VB rocket would launch three astronauts, an Extended CSM (XCSM) capable of 16 days of flight, and an Extended LM (XLM) capable supporting two astronauts for three days. The XLM would have a landed payload capacity of 1000 pounds. NASA would fly two Extended Apollo missions per year from 1971 through 1974, plus one in 1975, for a total of nine missions and 54 man-days on the Moon.

Once again, Grenning's model did not match up with reality. In January 1970, Paine had announced that, far from being uprated, Saturn V production would go on standby. He had also cancelled Apollo 20, at the time the last planned Moon-landing mission.

The IPP would have seen two-stage Saturn V rockets (designated Int-21) launch many payloads. Int-21 would have remained operational as late as the mid-1980s. This image shows the only two-stage Saturn V; it launched the Skylab space station in May 1973. Image credit: NASA.

In Grenning's traffic model, 1972 would see the first two-stage Int-21 Saturn V derivative launch the first Apollo Applications Program (AAP) Orbital Workshop (OWS). The AAP OWS was a 22-foot-diameter Saturn V S-IVB third stage converted into a temporary space station. The Int-21, of which a whopping total of 41 were meant to fly between 1972 and 1984, would be capable of placing up to 250,000 pounds into LEO.

Saturn IB rockets would launch three CSMs, each bearing a three-man crew, to the first AAP OWS between mid-1972 and early 1973. NASA would launch a second AAP OWS at the beginning of 1974. A total of nine CSMs would deliver crews to the the second AAP OWS by early 1976.

Paine had cancelled Apollo 20 so that its Saturn V could be used to launch the first AAP OWS. In February 1970, NASA announced that the AAP OWS program would be called the Skylab Program, a name that Grenning did not use in his June 1970 traffic model document.

Reusable IPP spacecraft and semi-permanent bases would make their debut in 1975, overlapping with missions using Apollo-Saturn systems and helping to ensure that there would be no gap in U.S. piloted spaceflight. As already indicated, these would increase the complexity of NASA piloted space operations. Spacecraft and bases would need to be assembled, refueled, and resupplied using other spacecraft and bases that would themselves need to be assembled, refueled, and resupplied.

Cutaway of a Saturn Int-21-launched Space Station Module with docked and docking research modules and, at its far end, a transfer module for transporting Station crews and supplies from a Space Shuttle Orbiter payload bay to the Station. Image credit: NASA.

In 1975, NASA would launch on an Int-21 its first LEO Space Station Module (SSM), the prototype for all subsequent SSMs. Grenning wrote that the LEO SSM, which would orbit between 200 and 300 nautical miles above the Earth, would be used to conduct science, applications, and technology research. It would also serve as a depot for cargo bound for GEO and the Moon, a satellite repair base, and an assembly and launch control center for automated and piloted planetary missions.

Soon after the LEO SSM reached space, the fully reusable Space Shuttle would take wing for the first time. In the LEO SSM's first year, winged Shuttle Orbiters would visit it three times. The 12-man Shuttle Orbiter would lift off vertically on the back of a winged, piloted booster larger than a 707 airliner, then would separate and ignite its own cluster of engines to complete the climb to LEO. It would carry up to 50,000 pounds of payload in its 15-by-60-foot payload bay. A Shuttle Orbiter would be good for 100 flights before it would need to be replaced.

The cislunar portion of the IPP architecture. Space Station Modules, color-coded blue, appear in low-Earth orbit, in synchronous Earth orbit, in lunar orbit, and on the lunar surface. The Shuttle is depicted as the only Earth-to-orbit transportation system, though the Saturn V would have remained in service into the 1980s. Image credit: NASA.

In 1975, NASA would also conduct a test flight of the Saturn VC, a beefed-up three-stage Saturn V with a Space Tug/LM-B fourth stage. The Saturn VC, an "interim system" for bridging the gap between Apollo and more advanced IPP lunar systems, would be capable of placing 100,000 pounds into lunar orbit. The LM-B, a Space Tug with landing legs, could operate on the lunar surface for up to 14 days at a stretch.

Early in 1976, a Saturn VC would launch a 50,000-pound SSM and a fully fueled Space Tug/LM-B to near-polar lunar orbit. During 1976, 1977, and 1978, nine Saturn VCs would launch four Space Tug/LM-Bs and five four-man "QCSMs" to the lunar-orbit SSM, enabling a continuous lunar population of four astronauts. The QCSM, which Grenning did not describe, would be an interim system like the Saturn VC. Two-person crews would land on the Moon in Space Tug/LM-Bs four times in 1976, five times in 1977, and four times in 1978. Each trip to the lunar surface and back would expend 50,000 pounds of liquid hydrogen/liquid oxygen (LH2/LOX) propellants.

One design concept for the Space Tug/LM-B. Image credit: NASA.

A slightly different design concept for the Space Tug/LM-B. Both the Tug/LM-B in this illustration and the one shown above it would have had similar capabilities. Image credit: NASA.

The Space Tug would have an important "Space Shuttle Augmentation" function. Among augmentation missions considered was satellite servicing beyond Space Shuttle/Space Station operational altitude. Image credit: NASA.

The American Bicentennial year of 1976 would see an Int-21 boost a stack of five fully fueled Space Tug/LM-Bs into LEO. With a full load of LH2 fuel and LOX oxidizer, each Tug/LM-B would have a mass of about 50,000 pounds. Space Tug/LM-Bs would be designed for a one-year in-space lifetime. Beginning in 1976, one Space Tug/LM-B would be based at the LEO SSM at all times for use in satellite servicing, spacecraft assembly, Earth-orbital rescue, and other missions.

The lunar-orbit SSM would have on hand two fully fueled Space Tug/LM-Bs at all times. One would land on the Moon and the other would stand by to rescue the surface astronauts in the event that their Space Tug/LM-B malfunctioned. After a year of operations, Space Tug/LM-Bs based at the lunar-orbit SSM would be stripped down and turned into tankage for a propellant depot in lunar orbit.

Also in 1976, the Space Shuttle would fly eight times. Six Shuttle missions would deliver astronauts, supplies, and cargoes, including two automated planetary spacecraft, to the LEO SSM. The remaining two missions would see the Shuttle orbiter serve in a "tanker" role. Each Shuttle Orbiter would carry 50,000 pounds of LH2/LOX propellants, enough to refuel one Space Tug/LM-B.

The Space Shuttle Orbiter in one of its chief IPP roles: that of tanker supplying propellants to other IPP spacecraft. Image credit: NASA.

A piloted Space Tug removes a cargo module from the Shuttle payload bay using robot arms, stacks it on its top (center left), performs rendezvous with a waiting Moon-bound Nuclear Shuttle (upper right), and transfers the cargo module. Image credit: NASA.

The first two missions of the Balanced Base planetary program, the Venus Explorer Orbiter and the Comet d'Arrest flyby, would depart Earth in 1976. Automated planetary missions would each need two fully-fueled Space Tug/LM-Bs. When the planetary launch window opened, Space Tug/LM-B #1 would ignite its rocket engines to accelerate Space Tug/LM-B #2 and the planetary probe, then would shut down its engines, undock from Space Tug/LM-B #2, turn end for end, and fire its engines again to return to LEO for refueling and reuse.

Space Tug/LM-B #2 would fire its engines to further accelerate the planetary probe, then would shut down its engines and release the probe onto its interplanetary trajectory. Space Tug/LM-B #2 would then turn end for end and fire its engines to slow itself and return to LEO.

Grenning's IPP included many Space Tug-launched robotic probes. The probe above resembles the Voyager Mars/Venus orbiter/lander design cancelled in 1967. Image credit: NASA.

In 1977, the Space Shuttle would fly 10 times and the Int-21 would fly twice. The Space Tug/LM-B could not carry enough propellants to change from near-equatorial LEO SSM orbit to polar Earth orbit, so two Shuttle Orbiters would launch directly from Earth's surface into polar orbit to perform sortie (non-Space Station) missions. Polar sorties would occur at a rate of two per year through 1984.

Eight Shuttle missions would transport crews and cargoes bound for the LEO SSM. One of those would deliver to 50,000 pounds of LH2 propellant for the first NERVA nuclear-thermal rocket engine-equipped Nuclear Shuttle, and four would deliver 50,000 pounds of Space Tug/LM-B propellants each.

The Nuclear Shuttle would extend the IPP's reach to the Moon and Mars, enabling establishment of Moon and Mars bases. Note the crew cabin (upper right). Image credit: NASA.

One Int-21 would launch the first Nuclear Shuttle and another would launch five fully fueled Space Tug/LM-Bs (four for the robotic planetary program and one for the LEO SSM). The Int-21 would not have the lift capacity to launch the Nuclear Shuttle to LEO fully fueled, so it would reach space with room in its tank for an additional 50,000 pounds of LH2. Before a newly launched Nuclear Shuttle departed LEO for the first time, a Shuttle Orbiter tanker would rendezvous with it to top off its tank.

Nuclear Shuttles would each be good for 10 missions from LEO to GEO or lunar orbit and back, then would be launched into disposal orbit around the Sun. Some would carry a cargo of worn-out Space Tug/LM-Bs into solar orbit with them.

Each Nuclear Shuttle mission would expend 240,000 pounds of LH2. Six Space Shuttle tanker flights would be required to refuel the Nuclear Shuttle once. The Nuclear Shuttle would transport to the lunar-orbit SSM six astronauts and 90,000 pounds of cargo, or 100,000 pounds of cargo in automated mode. It could return 10,000 pounds of cargo and six astronauts from the Moon to the LEO SSM.

The Nuclear Shuttle could deliver 90,000 pounds of cargo and six astronauts to GEO and return six astronauts from GEO to the LEO SSM. After the GEO SSM was established in 1980, all Nuclear Shuttles would perform a shakedown cruise to GEO before traveling to lunar orbit for the first time. If it malfunctioned during its maiden flight to GEO, a Space Tug/LM-B could rendezvous with it to make repairs or return it to the LEO SSM.

The first Nuclear Shuttle would operate only in automated mode; its 10 missions would serve as an extended flight test. The first piloted Nuclear Shuttle, the second launched, would reach LEO on an Int-21 in early 1979. Four piloted and six automated Nuclear Shuttle flights would occur each year beginning in 1981, by which time one new Nuclear Shuttle would reach LEO and one old Nuclear Shuttle would be disposed of in solar orbit each year.

In 1977, four Tug/LM-B pairs would launch the Mars Explorer Orbiter, the Mars High Data Orbiter, and two Jupiter-Saturn-Pluto Mariner-class flyby spacecraft. The Tug/LM-Bs would burn the propellants with which they were launched to send the two Mars missions on their way, then would be refueled to launch the twin Jupiter-Saturn-Pluto missions. Grenning noted that dispatching automated spacecraft to destinations beyond the Main Asteroid Belt would need so much energy that the second Tug/LM-B could spare no propellants to return to LEO. It would, therefore, be expended.

The year 1978 would see a Mercury-Venus Mariner flyby, a Venus Mariner Orbiter, and a Solar-Electric Asteroid Belt Survey depart the LEO SSM. All Space Tug/LM-Bs used to launch these missions would be recovered. In 1979, NASA would launch the 6,000-pound Mars Soft Lander/Rover and two more Jupiter-Saturn-Pluto Mariner-class flybys, expending two Tug/LM-Bs.

In 1980, a second Venus Explorer Orbiter would leave Earth, as would two Jupiter Flyby/Atmosphere Probe spacecraft. The latter would expend two Tug/LM-Bs. The year 1981 would see a second Mars Explorer Orbiter, two Saturn Mariner-class Orbiter/Atmosphere Probes, and two more expended Tug/LM-Bs.

NASA would launch only one automated planetary mission, the 8,000-pound Mercury Solar Electric Orbiter, in 1982. Venus would get another Venus Explorer Orbiter and a Venus Mariner Orbiter/Rough Lander in 1983. NASA would also launch its second comet mission, a Mariner rendezvous with Comet Kopff. With a mass of 8500 pounds, it would be the heaviest of the 21 automated probes in the Balanced Base program. Mars would get a second High Data Orbiter and a second Soft Lander/Rover in 1984.

Back in NASA's piloted program, between 1979 and 1981 Int-21s would launch three more LEO SSMs. These would be combined with the first LEO SSM to form a "Space Base" with a permanent crew of from 50 to 100 astronauts. In 1980, an Int-21 would launch into LEO an SSM that would be mated to a Nuclear Shuttle and boosted to GEO. Early in 1979, Space Shuttle missions would begin to fly at a rate of 30 per year; by mid-1980, Grenning had the number of flights ramping up to 90 per year.

One proposed Space Base configuration. This three-armed design, which would have a permanent crew complement of 50 astronauts and scientists, would spin about its axis to produce acceleration in the habitat arm (left). The crew would feel the acceleration as gravity. The other two arms would each hold a nuclear reactor at a safe distance from the crew in the habitat module and core section. Also visible to the right of the Space Base is a small free-flying science module; these would dock with the non-spinning core section for servicing. Image credit: NASA.

As indicated earlier, Grenning tied piloted Mars missions to no particular year. Probably the piloted Mars program would not begin until NASA had ample experience with long-duration spaceflight, orbital assembly, and Nuclear Shuttle operations. The Bellcomm planner did, however, lay out a seven-year plan encompassing two complete piloted Mars missions and the first half of a third. The first and second missions and second and third missions would overlap.

All three would follow a conjunction-class mission profile; that is, they would reach Mars in about six months, remain there for about 18 months, and return to Earth in about six months. For safety, two identical six-person Mars spacecraft would travel as a convoy. At launch from the Space Base, each would comprise three Nuclear Shuttles, a mission module housing the crew, a payload module bearing unmanned probes and supplies, and a two-stage piloted Mars Excursion Module (MEM) lander. Both Mars spacecraft would be capable of supporting the entire 12-person mission complement in case one failed catastrophically.

Nuclear Shuttle IPP mission applications would culminate with Mars missions in the 1980s. Each Mars expedition would include two piloted Mars spacecraft and each piloted Mars spacecraft would include one Nuclear Shuttle with strap-on tanks (as shown here) or a cluster of three Nuclear Shuttles (as shown in the next image). Image credit: NASA.

The IPP Mars mission would have seen two Nuclear Shuttles used as interplanetary boosters. After they set a third Nuclear Shuttle, a Space Station Module-based crew module, and a piloted Mars Excursion Module lander on their way, each would have separated, turned end-for-end, and fired its NERVA engine to slow down and return to low-Earth orbit for reuse. Image credit: NASA.

A pair of IPP interplanetary spacecraft en route to Mars. The bulbous forward section (right) would have housed sample-returner probes and the Mars Excursion Module piloted Mars lander. Image credit: NASA.

Eighteen months before the first mission was set to depart the Space Base, NASA would launch four Nuclear Shuttles on Int-21 rockets and then launch four Space Shuttles to top off their tanks. The following year, the space agency would launch two more Nuclear Shuttles. These would each have a half-load of LH2 propellant because the Int-21s that launched them would also carry one MEM each. Topping off the Nuclear Shuttle tanks would need three Space Shuttle flights. Six Shuttle flights would fuel Space Tug/LM-Bs used for Mars spacecraft assembly. A final pair of Int-21s would launch the twin SSM-derived Mars spacecraft mission modules; a final Space Shuttle would launch the Mars spacecraft crews.

As the countdown clock reached zero, the NERVA engines in the two outboard Nuclear Shuttles on each spacecraft would fire to place the third Nuclear Shuttle, mission module, payload module, and MEM on course for Mars. They would then shut down, separate, turn end for end, and fire their engines again to slow themselves and return to LEO. The center Nuclear Shuttle on each spacecraft would perform course corrections and slow the spacecraft so that martian gravity could capture them into orbit.

The Apollo Command Module-shaped MEM was designed to descend through the thin martian atmosphere found by the 1960s flyby Mars Mariners. It would have comprised two main parts: the descent module with Mars surface living accommodations and an airlock/garage with Mars surface rover; and the cramped ascent module, where the crew would ride during descent, landing, and ascent after the surface mission was complete. Image credit: NASA.

MEM ascent stage liftoff. The ascent stage was a stage-and-a-half design with a cluster of approximately conical expendable propellant tanks and integral tanks in its cylindrical core feeding a single engine. Image credit: NASA.

After 18 months at Mars, during which at least one MEM would land on the planet for about a month (the second might be held in reserve in Mars orbit as a rescue vehicle), the twin center Nuclear Shuttles would fire again to put the mission modules on course for Earth. They would be used to perform course corrections; then, as the Mars spacecraft neared Earth, they would fire for the last time to slow the mission modules for capture into Earth orbit. Space Tug/LM-Bs would retrieve the Mars crews and the center Nuclear Shuttles.

The second and third Mars missions would be carried out in much the same way. The four outboard Nuclear Shuttles from the first mission would be reused for the second and third missions and the two center Nuclear Shuttles from the first mission would be reused for the third mission. The second mission would leave LEO before the first mission returned, so would need two new center Nuclear Shuttles. Grenning wrote that the third mission, preparations for which would begin in the fifth year of the seven-year program, might establish the first semi-permanent Mars surface base.

Grenning forecast that the seven-year piloted Mars program would need four Space Shuttle flights and four Int-21 flights in its first year to place Mars spacecraft components and (especially) propellants into LEO. Year 2, toward the end of which the first two piloted Mars spacecraft would depart from Earth orbit, would need four Int-21s and 13 Shuttles.

Year 3, during which preparation for the second Mars expedition would begin, would need just one Int-21 and 13 Shuttle flights. NASA would launch 20 Space Shuttle flights and three Int-21s in the Mars program's fourth year, 10 Shuttle flights and no Int-21s in its fifth, and 24 Shuttle flights and four Int-21s in its sixth. The final year of the program would see no Int-21s and 13 Shuttle flights.

Grenning also summed up the number of flights required to carry out the Maximum Rate cislunar program from 1975, when IPP stations and spacecraft began to replace Apollo-based stations and spacecraft, to 1984. The Space Shuttle fleet would accomplish 518 missions to LEO. The Saturn VC would fly 11 times between 1975 and 1979, when it would be phased out in favor of piloted lunar flights via the Space Shuttle, LEO SSM, Nuclear Shuttle, lunar-orbit SSM, and LM-B. The Int-21 would fly 25 times in the cislunar IPP, with a peak annual launch rate of five in 1981.

Was the Mueller/Paine IPP in any sense realistic? It depends on the judgement criteria one uses. Certainly, it was not a realistic option for 1970 America due to domestic political and economic considerations, the opposition of the Nixon White House and the Congress, and public disinterest.

In addition, one might take issue with its confident assertion that its network of reusable space systems and permanent and semi-permanent bases would save money. Complex reusable space systems require either costly development or costly maintenance and refurbishment. A single failure can take down an entire network of interdependent complex systems, and pioneering systems are more prone to failure than well-established ones. If, for example, a Space Shuttle had exploded, then crew and propellant transport would have ground to a halt throughout the IPP infrastructure for an indeterminate period of time.

One might, on the other hand, argue that the IPP's scale was not adequate for the challenges of piloted space exploration. Even the IPP would have permitted astronaut access only to cislunar space, the Moon, and Mars. Perhaps we find the IPP grandiose in part because we have been conditioned to "think small" about space exploration. If our plans took in our entire local neighborhood — the Solar System — and sought to be realistic, then they would of necessity demand a scale orders of magnitude beyond that of the IPP.

Sources

"Integrated Manned Space Flight Program Traffic Model Case 105-4," E. M. Grenning, Bellcomm, 4 June 1970.

The Next Decade in Space: A Report of the Space Science and Technology Panel of the President's Science Advisory Committee, Executive Office of the President, Office of Science and Technology, March 1970.

"Statement About the Future of the United States Space Program," Richard M. Nixon, 7 March 1970.

"An Integrated Space Program for the Next Generation," George Mueller, Astronautics &  Aeronautics, January 1970, pp. 30-51.

"Integrated Space Program - 1970-1990," Internal Note-PD-SA-69-4, Terry Sharpe & Georg von Tiesenhausen, Advanced Systems Analysis Office, Program Development, NASA Marshall Space Flight Center, 10 December 1969.

America's Next Decades in Space: A Report for the Space Task Group, NASA, September 1969.

The Post-Apollo Space Program: Directions for the Future, Space Task Group Report to the President, September 1969.

"Manned Mars Landing Presentation to the Space Task Group," Wernher von Braun, 4 August 1969.

"Integrated Manned Space Flight Program: 1970-1980," NASA Office of Manned Space Flight, NASA Headquarters, 12 May 1969.

Astronautics and Aeronautics, 1970, NASA SP-4015, 1972, pp. 77-79, 82-84.

Astronautics and Aeronautics, 1969, NASA SP-4014, 1970, pp. 266-269, 304-305, 308.

After Apollo? Richard Nixon and the American Space Program, John M. Logsdon, Palgrave MacMillan, 2015.

More Information

Triple-Flyby: Venus-Mars-Venus Piloted Missions in the Late 1970s/Early 1980s (1967)

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

McDonnell-Douglas Phase B Space Station (1970)

Space Station Resupply: The 1963 Plan to Turn the Apollo Spacecraft Into a Space Freighter

Triple-Flyby: Venus-Mars-Venus Piloted Missions in the Late 1970s/Early 1980s (1967)

A NASA Manned Spacecraft Center-designed piloted flyby spacecraft departs Earth orbit. A series of three Saturn S-IVB stages would have ignited in turn to place the spacecraft on its interplanetary trajectory. The stylized image above shows two spent S-IVB stages, the third S-IVB with its single J-2 engine firing, and the piloted flyby spacecraft with portholes and a streamlined cover over its large telescope. In most piloted flyby plans, the Earth-departure burns together constituted the only significant propulsive velocity change of the mission. Image credit: NASA.

During its first decade (1958-1968), NASA devoted more advance planning study effort to piloted Mars and Venus flybys than it did to piloted Mars landings. Piloted flyby missions to the nearest planets were seen as the most ambitious voyages beyond the Moon potentially feasible in the 1970s. Such missions could, many believed, employ modified, upgraded Apollo spacecraft and Saturn rockets to serve as low-cost "bridge" missions linking planned temporary Earth-orbiting space stations of the early 1970s and piloted Mars landings and Venus orbiters of the early-to-mid 1980s. In this respect, they would be as Project Gemini was for Project Mercury and Project Apollo.

Despite the effort spent on them, NASA's 1960s piloted flyby plans are little remembered today. Proposals for piloted flybys in recent years almost never cite the mass of study documents NASA and its contractors generated half a century ago. Even careful historians confuse piloted flyby mission proposals and spacecraft designs with piloted landing proposals and spacecraft.

The NASA Headquarters-led Planetary Joint Action Group (JAG), which included representatives from Marshall Space Flight Center, Kennedy Space Center, and the Manned Spacecraft Center in Houston, proposed in a pivotal October 1966 internal report that the first piloted Mars flyby mission should depart Earth orbit in September 1975. The four-person Apollo-derived flyby spacecraft would swing past Mars in late January-early February 1976 and return to Earth in July 1977.

As it flew past Mars, its crew would release automated probes. At least one would soft-land, collect samples of Mars rocks, dirt, and air, and launch them to a hermetically sealed laboratory on board the piloted flyby spacecraft for initial study and transport to labs on Earth.

Except for modest course corrections, no propulsion would be needed after the piloted flyby spacecraft left Earth orbit. This was one of the mission's great attractions. As they neared Earth, the flyby astronauts would abandon the piloted flyby spacecraft and reenter the atmosphere in a beefed-up Apollo Command Module.

In its report, the Planetary JAG described several candidate follow-on piloted flyby missions for the remainder of the 1970s. Of great scientific interest was a "triple-flyby" mission, in which the piloted spacecraft would fly past Venus, then Mars, then Venus again, before returning to Earth. As with the simpler September 1975 Mars flyby mission, only minor course adjustments would be necessary after the triple-flyby spacecraft left Earth orbit.

Venus flyby: the piloted flyby spacecraft depicted in Earth-orbital launch configuration at the top of this post is shown here with its telescope, solar arrays, dish antennas, and Venus mapping radar antenna deployed. A robotic Venus atmosphere-entry probe — perhaps a lander — is shown departing the flyby spacecraft probe compartment. This NASA Manned Spacecraft Center concept, never described in a formal report, dates from near the end of the 1960s period of piloted flyby planning. Image credit: NASA.

Unfortunately, the only opportunity to begin a triple-flyby in the late 1970s known in 1966 was poorly timed. The spacecraft would need to depart Earth in February 1977, while the 1975 Mars flyby mission was still underway. This would create operational difficulties — NASA would need to operate two piloted planetary missions at once — and would deprive the space agency of the opportunity to apply lessons learned from the September 1975 flyby mission. No other opportunity to begin a triple-flyby mission was known before 1983. Planetary JAG planners assumed that by that date NASA would have moved on to piloted Mars landings and Venus orbiters.

In September 1967, J. Bankovskis and A. Vanderveen, advance planners with NASA contractor Bellcomm, identified a triple-flyby opportunity with an optimum Earth-departure date of 26 May 1981. A spacecraft launched from Earth orbit on that date would fly past Venus on 28 December 1981, past Mars on 5 October 1982, and past Venus again on 1 March 1983. It would return to Earth on 25 July 1983. Mission duration would total 790 days. Departures on other dates within a 30-day launch window would yield mission durations of from 720 days to 850 days.

Discovery of the 1981 triple-flyby opportunity led Vanderveen to look for other triple-planet flyby opportunities researchers had missed. In October 1967, a year after the Planetary JAG completed its report, he announced that he had determined that a previously known November 1978 "dual-planet" (Venus-Mars) flyby mission opportunity could be slightly modified to create a new triple-flyby opportunity.

Vanderveen wrote that, if one assumed a launch from Earth orbit on 28 November 1978, then the triple-flyby spacecraft would pass Venus on 11 May 1979, Mars on 25 November 1979, and Venus again on 29 January 1980. Return to Earth would take place on 31 January 1981. Mission duration would total 800 days. Earth departure on other dates within a 35-day launch window could reduce mission duration to 760 days.

Vanderveen explained that the two Venus flybys would have different qualities, so they would require different scientific programs. In both, the flyby spacecraft would pass about 1200 miles from Venus. On 11 May 1979, the triple-planet spacecraft would race past the center of the dayside hemisphere, its ground track nearly paralleling the Venusian equator. This, Vanderveen wrote hopefully, might permit visible-light mapping through breaks in the dense Venusian clouds.

The southern hemisphere of Venus as imaged by the European Space Agency's Venus Express orbiter. Image credit: ESA.

The 29 January 1980 Venus flyby, on the other hand, would see the spacecraft slowly approach the planet's dayside southern hemisphere. It would pass closest to Venus 30° south of the equator near the terminator (the line between day and night), then would recede from Venus's nightside hemisphere. Vanderveen recommended that the flyby crew turn infrared sensors and a mapping radar toward the night side as they flew away from Venus and began their year-long return to Earth.

Piloted flybys did not become part of NASA's 1970s program for several reasons. NASA split over the efficacy of the piloted flyby mission concept, with the Manned Spacecraft Center in particular favoring as bridge missions piloted Mars and Venus orbiters over piloted flybys.

More important was a toxic political climate, which was partly of NASA's making. Increasing U.S. military involvement in Indochina drove up the Federal budget deficit, leading to cuts in many programs, including the space program.

The Apollo 1 fire (27 January 1967) damaged the relationship between NASA and Congress at this critical time, increasing the space agency's vulnerability to funding cuts. The fire broke out during a pre-flight test inside the first Apollo Command and Service Module (CSM) spacecraft scheduled to fly with a crew on board. Astronauts Gus Grissom, Ed White, and Roger Chaffee perished. It emerged that CSM contractor North American had delivered to NASA CSM spacecraft containing many manufacturing flaws, yet NASA had not shared this fact with Congress.

Efforts by NASA Headquarters under Administrator James Webb and the Lyndon Baines Johnson White House to secure substantial funding for post-Apollo piloted spaceflight, including piloted flybys, had switched into overdrive just before the Apollo 1 fire, so became a lightning-rod for Congressional displeasure. In August-September 1967, Congress slashed the Apollo Applications Program (AAP) budget request for Fiscal Year 1968 and heaped scorn on piloted and robotic Mars plans.

AAP, a series of Earth-orbital temporary space station and advanced moon missions based on Apollo hardware, shrank rapidly during the following year. The only U.S. automated probe program planned for the 1970s, the Voyager Mars/Venus program, was cancelled outright in part because the Planetary JAG had relied heavily on Voyager heritage for its piloted flyby automated probe designs.

NASA adapted to adversity, turning AAP into the Skylab Program (three three-man long-duration stays on board one Orbital Workshop space station) and the advanced Apollo J-class missions (Apollo 15, 16, and 17). The space agency also successfully negotiated with Congress for a new program of automated Mars spacecraft based on the low-cost Mariner design (Mariner 9 and Viking 1 and 2).

Piloted flybys would, however, never recover, in part because in early 1969, under the leadership of new NASA Administrator Thomas Paine, NASA advance planning became increasingly grandiose. Paine told NASA Center directors to "think big" in anticipation of riding the wave of spaceflight enthusiasm he expected would follow the first piloted Moon landing.

The result was an elaborate Integrated Program Plan (IPP) with a 12-man Space Station evolving into a 100-man Earth-orbital Space Base, reusable winged Space Shuttles, uprated Saturn V rockets, a lunar base, reusable Nuclear Shuttles for transport within cislunar space, and, by 1986 at the latest, a large piloted expedition to land on Mars. A forward step as small as an Apollo-derived piloted flyby mission had no place in the grand IPP.

The post-Apollo 11 wave was short-lived, however. Paine won over Vice-President Spiro Agnew to his plans for men on Mars, but it was a hollow victory, for Agnew had no power in the Administration of Richard Nixon. President Nixon, for his part, for a time considered ending piloted spaceflight.

Unlike the piloted flyby plans of NASA's first decade, the grand-scale plans of 1969-1970 would be long remembered. They would serve mainly to instill in the minds of many the expectation that initial piloted voyages to Mars must land and must be expensive.

Sources

"The Existence of a 1981 Triple-Planet Ballistic Flyby – Case 103-2," A. Bankovskis and A. Vanderveen, Bellcomm, 19 September 1967.

"Verification of the Existence of the 1978 Triple-Planet Flyby Opportunity – Case 720," A. Vanderveen, Bellcomm, 19 October 1967.

"White House Stand Blocks NASA Budget Restoration," Aviation Week & Space Technology, 28 August 1967, p. 32.

After Apollo? Richard Nixon and the American Space Program, John M. Logsdon, Palgrave MacMillan, 2015.

More Information

EMPIRE Building: Ford Aeronutronic's 1962 Plan for Piloted Mars/Venus Flybys

After EMPIRE: Using Apollo Technology to Explore Mars and Venus (1965)

"Assuming That Everything Goes Perfectly Well in the Apollo Program. . ." (1967)

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

The Russians are Roving! The Russians are Roving! A 1970 JPL Plan for a 1979 Mars Rover

1984: A Proton-K rocket very similar to those that launched Luna 17/Lunokhod 1 in 1970 and Luna 21/Lunokhod 2 in 1973 lifts off from Baikonur Cosmodrome bearing one of a pair of Vega probes destined for Venus and Halley's Comet. Image credit: Lavochkin Association/NASA.

As night fell at Baikonur Cosmodrome in Soviet Kazakhstan on 10 November 1970, a Proton rocket thundered to life and began its climb toward space. Six days later, the rocket's payload, the automated Luna 17 Moon lander, soft-landed on broad, flat Mare Imbrium. A team of six operators in the Soviet Crimea — five main operators plus a spare — remotely drove the Lunokhod 1 rover down ramps lowered from the lander onto the Moon's dusty surface.

The solar-powered (but nuclear-heated) 756-kilogram rover, measuring 1.35 meters tall and 2.15 meters across its tub-shaped equipment compartment, rolled on eight metal wheels with cleats at a top speed of 0.1 kilometers per hour. A hinged, bowl-shaped lid lined with electricity-generating solar cells opened to expose a thermal radiator atop the tub; as night approached, Lunokhod 1's operators commanded it to close the lid to hold in heat and protect its delicate electronics.

Lunokhod 1. Image credit: Lavochkin Association/NASA.

Lunokhod 1 originated in the abortive Soviet piloted Moon program, though this would not be revealed until the late 1980s. Its initial role was to have been to certify as safe the landing site selected for the piloted lunar landing.

The rover would then have stood by until a lander bearing a single cosmonaut arrived. If his lander became damaged during touch-down so that it could not return him to lunar orbit, the Lunokhod operator team on Earth would drive the rover to pick him up for transfer to a waiting, pre-landed backup lander. The United States had, incidentally, in the early 1960s considered launching site-survey rovers to Apollo landing sites, and had studied long-range automated rovers that visiting astronauts could board and drive.

Even before the successful Apollo 11 landing (20 July 1969), the Soviets claimed that they never intended to land cosmonauts on the Moon. This was, of course, untrue, but it found a receptive audience among those who opposed piloted lunar exploration on the basis of cost or who favored the Soviet Union in the Cold War.

Through their official media, the Soviets declared that they had opted instead for robot explorers that cost much less than Apollo and placed no human life at risk. This message was particularly potent in the months following the near-disaster of Apollo 13 (11-17 April 1970).  They told the world that Lunokhod 1 and its cousins, the Luna automated sample returners, presaged a new era of extensive and intensive robotic lunar and planetary exploration.

U.S. space planners took note. In a report called An Exploratory Investigation of a 1979 Mars Roving Vehicle Mission, completed a timely three weeks after Luna 17 landed on Mare Imbrium and Lunokhod 1 began its traverse, a 12-man design team at the Jet Propulsion Laboratory (JPL) in Pasadena, California, described a NASA Mars rover mission in 1979.

Billed as a "logical follow-on" to the Viking landings planned for mid-1976, JPL's 1127-pound rover would include six wire wheels akin to those on the Apollo Lunar Roving Vehicle, which at the time was scheduled to be driven by astronauts on the Moon for the first time in 1971. Mobility would enable "extended" Viking objectives: for example, while Viking would land on a safe, flat plain and seek living organisms only within reach of its three-meter-long robot arm, the 1979 rover could land in a flat area, then enter rugged terrain to seek out biologically promising sites.

Viking 1 launch on a Titan III-E rocket on 20 August 1975. Image: NASA.

The Mars rover would leave Earth between late October and mid-November 1979 on a Titan III-C rocket with a Centaur upper stage — the same rocket/upper stage combination that would launch the Vikings in 1975. It would lift off sealed within a Viking-type lander aeroshell and bioshield cap attached to a Viking-type orbiter. The orbiter's rocket motor would perform a course correction burn 10 days after launch.

Assuming a 3 November 1979 launch, Earth-Mars transfer would need 268 days. During the voyage, a door would open in the top of the aeroshell and the rover's cylindrical electricity-generating Radioisotope Thermal Generators (RTGs) would extend into space on a boom. The plutonium-powered RTGs would continually generate heat; if kept sealed within the aeroshell during the flight to Mars, heat build-up would damage the rover.

Mars arrival would occur in August 1980. The orbiter's rocket motor would slow the spacecraft so that the planet's gravity could capture it into orbit. Two days later, it would tweak its orbit so that it would pass over the rover's primary landing site. The JPL team estimated that its Mars rover could reach sites between 30° north and 30° south latitude.

Cutaway of JPL's proposed 1979 Mars rover packed into its Viking-type aeroshell. The arrow points to the rover's twin RTGs, which are extended beyond the aeroshell on a boom to prevent them from overheating the rover's electronic systems during the flight to Mars. Image credit: JPL/NASA.

Five days after Mars orbit arrival, the rover would cast off its bioshield cap to expose the aeroshell. Shortly before separation from the orbiter, the rover would retract its RTGs. The aeroshell would then separate and fire thrusters to slow down and fall toward Mars.

The JPL engineers described the rover landing sequence in considerable detail. Two hours after separation from the orbiter and 300 seconds before landing (that is, at L minus 300 seconds), the aeroshell would encounter the thin upper atmosphere of Mars. Entry deceleration would peak at about 12 times the force of Earth's gravity.

At L minus 80 seconds, moving at a speed of Mach 2.5, the aeroshell would deploy a compact ballute ("balloon-parachute") 21,000 feet above Mars. Three seconds later, at 19,000 feet and a speed of Mach 2.2, a single parachute would deploy and the ballute would separate.

At L minus 73 seconds, with the rover streaking through the martian sky at Mach 2, the parachute would fill with thin martian air. Six seconds later, the lower aeroshell would separate, exposing the rover's underside and twin landing radars.

JPL's 1979 Mars rover in its landed configuration. Arrows point to the three terminal descent rocket motors. Image credit: JPL/NASA.

Three terminal descent rocket motors on the rover would begin firing at L minus 33 seconds. Three seconds later, at an altitude of 4000 feet and a speed of 300 feet per second, the parachute and upper aeroshell would separate from the rover. The rover would then touch down gently on Mars directly on its wheels.

JPL's rover would comprise a train of three compartments, each with one wheel pair. Flexible connectors would link the compartments. The forward compartment (the "science bay") would include a Viking-type soil sampler arm with an attached soil magnetic properties experiment, a new-design "chisel and claw" arm, four biology experiment packages (the number NASA planned to launch on the Viking landers at the time JPL completed its rover report), a mass spectrometer, a weather station, and a seismometer. The forward compartment wheel hubs would carry one terminal descent rocket motor each, and the front wheel pair would be steerable.

The middle compartment (the "electronics bay") would house the 95-pound dual-purpose (science & rover control) computer.  A telescoping stalk would support a dish-shaped high-gain antenna, a low-gain antenna, a facsimile camera capable of generating a 360° panorama, and a vidicon camera with rangefinder.

The rear compartment (the "power bay") would include the twin externally-mounted RTGs, landing radars on its wheel hubs, and a rear-mounted terminal descent rocket motor. The rear wheel pair would, like the front pair, be steerable.

From some time before Earth launch until its second day on Mars, the three compartments would be squeezed together tightly with their wheels touching. This would enable the rover to fit within the confines of its Viking-type aeroshell.

Controllers on Earth would check out the rover during its first day after touchdown on Mars. On Day 2, they would spread out its compartments, deploy its appendages, and discard the terminal descent motors and landing radars. The JPL design team looked briefly at retaining the terminal descent rockets to enable the rover to "hop" over obstacles, but rejected this capability as being too fraught with risk.

Science operations would commence on Day 3. Mars surface operations would span one Earth year, from August 1980 to August 1981.

Controllers on Earth would guide the rover through its daily program. Operations would occur only during the martian daylight hours, when line-of-sight radio contact with Earth was possible.

Time available for operations during each 24-hour, 39-minute martian day would vary over the rover's one-Earth-year mission, as would radio-signal travel time. On 9 August 1980, for example, a rover at a site on the martian equator would remain in contact with Earth for 10.93 hours, while radio signals would need about 21 minutes to cross the gulf between the planets. In May 1981, Earth and Mars would be far apart — on opposite sides of the Sun — and radio-signal travel time would reach its maximum value of 41 minutes.

Typically, the rover would move from 50 to 100 meters at a time, then halt, image its surroundings, perform one of its science experiments, transmit its data to Earth, and then await new commands. JPL assumed that high-interest science sites would occur on average about 14 kilometers apart along its traverse route, and estimated that early in its mission the rover would travel about 300 meters per day, enabling it to traverse the distance between two science sites in 47 days. Distance traversed would, JPL optimistically assumed, rapidly increase as controllers gained confidence in their remote driving ability: the team estimated that in one Earth year its rover might traverse up to 500 kilometers.

Inspired, perhaps, by Lunokhod 1, the JPL team concluded its study by looking briefly at a lunar variant of its Mars rover design. The team found that the basic design of both rovers could be much the same, though the lunar rover launch vehicle would not need to be as large and powerful (a Titan III/Centaur without strap-on solid-propellant boosters would suffice) and a solid-propellant braking rocket would need to replace the Mars rover's aeroshell, ballute, and parachute because the moon has no atmosphere. In addition, the lunar version could tote an additional 150 pounds of science payload.

As the team's study circulated to a limited JPL audience, Lunokhod 1 continued its slow traverse over dusty Mare Imbrium. The Soviet rover was designed to function for three months, but did not officially cease operations until the 14th anniversary of the launch of Sputnik 1 on 4 October 1971, some 10 months after JPL completed its report (radio contact with Lunokhod 1 was, however, lost on 14 September 1971). During its 10.54-kilometer traverse, it beamed to Earth more than 20,000 images of its surroundings and analyzed lunar surface composition at 25 locations.

Lunokhod 2 included new cameras and instruments and was designed to travel over the lunar surface more quickly than had Lunokhod 1. In this image, the dual-purpose dish-shaped solar array/thermal cover is shown folded open, as it would have been during lunar daytime. Image credit: Lavochkin Association/NASA.

The Soviets followed up Lunokhod 1's success a few weeks after Apollo 17 (7-19 December 1972), the final piloted lunar mission. On 17 January 1973, Luna 21 landed inside rugged Le Monnier Crater bearing the Lunokhod 2 rover. The new rover was, the Soviets stated, superior to its predecessor. It would, for example, scuttle across the lunar surface much more rapidly than could Lunokhod 1.

On 9 May 1973, after traversing some 37.5 kilometers in less than three months, Lunokhod 2 rolled accidentally into a dark-floored crater. Its open bowl-shaped solar array/thermal cover apparently brushed against the crater wall, becoming partly filled with lunar dirt.

When, shortly thereafter, controllers in the Crimea commanded the array/thermal cover to shut at lunar sunset, the dirt fell on Lunokhod 2's thermal radiator. Two weeks later, as the Sun rose again at Le Monnier, controllers commanded the array/thermal cover to hinge open in preparation for a new day of lunar driving.

The dirt-covered radiator could no longer reject heat adequately, so Lunokhod 2 rapidly overheated in the harsh lunar sunlight. The Soviets declared its mission ended on 3 June 1973. Lunokhod 2 was the last rover to operate on another world until Mars Pathfinder's Sojourner mini-rover in 1997.

In March 2010, NASA released high-resolution Lunar Reconnaissance Orbiter (LRO) images of the Moon's surface showing the Lunokhod 1 and Lunokhod 2 rovers and the Luna 17 and Luna 21 landers. In the intervening years, LRO has orbited lower over the Lunokhod landing sites, enabling higher-resolution imaging. LRO images clearly show the extended Luna 17 and Luna 21 ramps and the tracks Lunokhod 1 and Lunokhod 2 left on the lunar surface.

The last journey of Lunokhod 2: the black arrow points to the crater where the rover accidentally collected a load of lunar dirt. Soon afterwards, the rover parked for the lunar night. The white arrows running up the center of the image highlight tracks Lunokhod 2 left as the Sun rose and the dirt on its radiator caused it to overheat. The white arrow near the top of the image points to Lunokhod 2 in its final resting place. This image shows an area of Le Monnier crater roughly 400 meters square. Image credit: NASA.

Proposals for a Viking follow-on robot rover mission would be put forward throughout the 1970s and 1980s, but none would move beyond the stage of proposals and studies. In part, this was because the Soviet Union failed to follow through on its promise (or threat) to launch robot sample returners and rovers to the planets.

Competition with the Soviet Union was rarely mentioned as a motive for robotic exploration after the early 1970s. When it was, it lacked its old punch: for example, it utterly failed to move lawmakers when comet scientists sought to use it as a justification for funding a U.S. mission to Comet Halley during its 1985/1986 apparition.

JPL's proposed 1979 rover bears a passing resemblance to the Mars Science Laboratory (MSL) rover Curiosity launched on 26 November 2011, almost exactly 41 years after Lunokhod 1. Both the JPL 1979 rover design and Curiosity have six wheels, rear-mounted nuclear power sources, stalk-mounted cameras, and front-mounted arms.

The nuclear-powered Mars Science Laboratory Curiosity captured a selfie on 3 February 2013. Image credit: NASA.

Curiosity, however, has a single body, solid wheels, and a more elaborate suspension system. Curiosity is also larger and heavier (about 2000 pounds) and depended on a more complex (and, to many observers, more worrisome) landing system known as the Sky Crane. The new system functioned as advertised, however, gently lowering Curiosity onto its wheels in equatorial Gale crater late in the evening U.S. Pacific Time on 5 August 2012.

Perhaps the most profound difference between the 1979 and 2011 rovers has to do with expectations. JPL engineers in 1970 assumed that their rover might cover half a thousand kilometers in a single Earth year. Curiosity, by contrast, cautiously traversed about 7.9 kilometers during its first 687-day martian year, which ended on 24 June 2014.

Although it has suffered wheel damage, Curiosity continues to climb the foothills of Aeolus Mons, an immense geologic layer-cake that fills much of Gale crater. Curiosity is expected to continue exploring until it suffers a catastrophic failure or until its electricity-generating nuclear source runs down, whichever comes first.

Sources

An Exploratory Investigation of a 1979 Mars Roving Vehicle Mission, JPL Report 760-58, J. Moore, Study Leader, Jet Propulsion Laboratory, 1 December 1970.

Challenge to Apollo: The Soviet Union and the Space Race, 1945-1974, NASA-SP-2000-4408, Asif Siddiqi, NASA, 2000, pp. 532-533, 740-743.

Press Kit, Mars Science Laboratory Landing, NASA, July 2012.

More Information

Centaurs, Soviets, and Seltzer Seas: Mariner 2's Venusian Adventure (1962)

A 1974 Plan for a Slow Flyby of Comet Encke

Making Propellants from Martian Air (1978)

Harold Urey and the Moon (1961)

Nobel Laureate and Moon fan Harold Urey. Image credit: NASA.

Harold Clayton Urey as born in the small town of Walkerton, Indiana, on 29 April 1893. He taught school in Indiana and Montana, then earned Bachelor's degrees in biology and chemistry from the University of Montana. After a stint at a chemical plant in Philadelphia, he earned a PhD in chemistry at the University of California at Berkeley in 1923.

Following a fellowship in theoretical physics at the Bohr Institute in Copenhagen, he joined the Chemistry faculty at Johns Hopkins University in Baltimore, then moved to Columbia University in New York. On Thanksgiving Day in 1931, Urey discovered the hydrogen isotope deuterium, a feat that earned him the Nobel Prize in Chemistry in 1934.

By most accounts, Urey was a generous and humble man. For example, he shared credit for his deuterium discovery with the scientist who manufactured the five liters of liquid hydrogen he used for his research.

Urey left Columbia for the University of Chicago in 1945. While in Chicago, he read Ralph Baldwin's 1949 book The Face of the Moon, which made the case for the impact hypothesis; that is, that the Moon's many craters are not volcanic calderas, as was widely believed, but are instead scars left by asteroid impacts. Baldwin's book changed Urey's professional life.

In 1952, Urey published The Planets, which launched the science of geochemistry as applied to extraterrestrial bodies. He christened this new discipline "cosmochemistry." In his book, Urey espoused the "cold Moon" theory; that is, that the Moon never became hot enough internally for its rocks to melt. The cold Moon hypothesis and the impact hypothesis went hand in hand; Urey expected that a cold, quiescent moon would be necessary to preserve ancient impact craters.

Earth's natural satellite was, he argued, little changed from the time it had formed. If humans one day could collect a piece of the Moon, it followed, then they would have in hand a "Rosetta Stone" for deciphering the Solar System's early history.

What turned out to be the first steps toward lunar sample return occurred shortly after Urey's book saw print. In late July 1955, the United States announced that it would launch a civilian scientific Earth satellite during the International Geophysical Year (IGY), an 18-month worldwide science campaign that would begin on 1 July 1957. A little more than a month later, in early September 1955, the Soviet Union announced that it, too, would launch a satellite into Earth orbit during the IGY.

President Dwight Eisenhower had little enthusiasm for rockets and satellites except insofar as they had defense applications. The U.S. IGY satellite, though civilian in nature, received his support because it had a hidden military agenda. It was intended to assert the international legal principle of the "Freedom of Space," which was meant to be analogous to the long-established principle of the Freedom of the Seas. The new principle would, Eisenhower hoped, quell Soviet protests when the United States began to launch surveillance satellites into orbits that carried them over Soviet territory.

The Eisenhower Administration believed that the Soviet Union did the United States a "good turn" by launching Sputnik 1, the first Earth satellite, on 4 October 1957. The Soviet satellite, which passed over U.S. territory several times each day, made unnecessary American assertion of the Freedom of Space principle.

Sputnik 1 soon turned into a liability for the Eisenhower Administration, however. The old General tried to downplay its significance, but neither an American public fearful of apparent Soviet technological superiority nor Democratic Senate Majority Leader (and Presidential hopeful) Lyndon B. Johnson would stand for it.

One result of Sputnik 1 was the creation of the civilian National Aeronautics and Space Administration (NASA), which opened its doors on 1 October 1958. By then, both U.S. and Soviet rocketeers had begun to launch small probes toward the Moon.

During 1958, Urey retired from the University of Chicago and went to work at the University of California, San Diego. On 29 October 1958, at the Lunar and Planetary Exploration Colloquium held at the Jet Propulsion Laboratory in Pasadena, California, he famously predicted that new lunar discoveries would give him a "very red face" in only a few years; that is, that spacecraft would soon collect data that would disprove many of his favorite lunar theories. "Nature can always be more complicated than we imagine," he added.

In November 1958, Urey met newly hired NASA scientist Robert Jastrow, whom he quickly converted to the cause of lunar exploration. The following month, Urey and Jastrow met with NASA Deputy Director for Space Flight Programs Homer Newell at NASA Headquarters in Washington, DC.

At the time, scientists interested in space physics — the study of particles and fields in space — dominated NASA space science. Urey and Jastrow sought to convince Newell that NASA should apply some of its scientific energies (and funds) to the exploration of the Moon's geology.

On 5 February 1959, the NASA Working Group on Lunar Exploration, chaired by Jastrow, met for the first time. Urey was an enthusiastic member. He also became a founding member of the influential National Academy of Sciences Space Science Board, which displayed its backing for lunar exploration by forming a "Lunar Committee." The group strongly supported President John F. Kennedy's 25 May 1961 call for a man on the Moon by 1970.

Three weeks after Kennedy's "Moon Speech," Urey responded to an informal request from Newell that he recommend landing sites on the Moon. In a 19 June 1961 letter, the polymath Nobel Laureate told Newell that "we should attempt to. . . get as great a variety of objectives as possible in as few landings as possible." In acknowledging that the Apollo landings might be few in number he was ahead of many of his colleagues. Urey then listed six classes of sites he felt should be explored.

The numbers in the image above are explained in the post text. Image credit: NASA/David S. F. Portree.

The first class took in sites at high latitudes (that is, close to the lunar poles) (1 on the image above). Urey explained that Harrison Brown, a fellow member of the Working Group on Lunar Exploration, had "presented evidence that water may exist close to the surface in certain high latitude areas." This was, of course, in keeping with Urey's "cold Moon" hypothesis.

Urey then called for landings on two of the lunar maria ("seas"), the smooth, relatively dark-hued plains that mottle the Moon's Earth-facing Nearside hemisphere. One of these, he explained, should be "of the deep type" — that is, it should be an obvious giant impact basin such as "the great collision area just before Sinus Iridium in Mare Imbrium" (2 on the image) or Mare Serenitatis (3). Seismic instruments emplaced on a deep mare would, Urey believed, enable determination of the depth to which the giant impactors that formed them had penetrated the Moon's crust.

The other mare landing should occur on a "shallow" mare, Urey wrote. In the shallow category he listed Oceanus Procellarum (4) and Mare Tranquillitatis (5), neither of which displays the distinctive round outline of Mare Imbrium and Mare Serenitatis. Urey told Newell that NASA would probably want to land first on Oceanus Procellarum in any case because it was a wide plain with few mountains or other obstructions to imperil descending spacecraft.

Next on Urey's wishlist was the interior of a large impact crater. He suggested Alphonsus (6), an old crater partly filled with "gray material." Soviet scientist Nikolai Kozyrev claimed to have observed there in 1958 a short-lived white cloud. Urey noted also that geologist Eugene Shoemaker, founder and first chief of the U.S. Geological Survey's Branch of Astrogeology in Menlo Park, California, was hard at work studying the young crater Copernicus (7) in "very great detail," and that his work might pave the way for a landing there.

Fourth on Urey's list was one of the "great wrinkles in the maria." He told Newell that the wrinkle ridges, as they are known, might be places where water had escaped from the Moon's icy cold interior. He added that Gerard Kuiper, founder of the Lunar and Planetary Laboratory in Tucson, Arizona, had observed deposits of white material atop the ridges. Urey interpreted these as salts left behind as water boiled away in the lunar vacuum.

A Moon lander dispatched to Mare Imbrium near Sinus Iridium could, Urey added, explore both a deep mare and prominent wrinkle ridges (8). Similarly, a landing near Copernicus could explore both the great crater and nearby "little volcano-like things" (9) that Urey believed were related in some way to the wrinkle ridges.

Number five on Urey's list was a mountainous area. His chief candidate was the Haemus Mountains on the south edge of Mare Serenitatis (10), which he believed constituted a mass of material blasted out during the formation of Mare Imbrium.

Finally, Urey listed features that were of interest to him personally. These included an unusual dark gray line in Mare Serenitatis, which he had theorized in the early 1950s was a streak of carbon-rich material similar to that found in primitive carbonaceous chondrite meteorites (11). He also suggested the Aristarchus-Herodotus region (12), which Kozyrev had found to be "luminous," and Lacus Mortis (13), which Urey believed was a graben; that is, a sunken block of lunar crust.

Urey ended his letter by asking Newell to share with him any landing site suggestions he received from other scientists. He argued that site selection was an important matter that "should be considered by many of us."

In his reply of 29 June 1961, Newell told Urey that he had forwarded his suggestions to NASA's Office of Lunar and Planetary Programs and to "the special study groups who have been working out plans for the manned lunar landing." Newell also urged Urey to share with him "any ideas that the Lunar Committee of the Academy's Space Science Board might have."

Urey remained active in lunar exploration throughout the 1960s. In early 1962, he joined the 12-member ad hoc working group NASA's Office of Space Science created to outline the Apollo science program. He participated in the Ranger (1961-1965) and Surveyor (1966-1968) automated missions, as well as the piloted Apollo 11 (July 1969) and Apollo 12 (November 1969) missions, which sampled Mare Tranquillitatis and Oceanus Procellarum, respectively. As he predicted, he had occasion to become red in the face: the Moon, the Apollo samples and surface experiments showed, was molten throughout its first 1.5 billion years of existence, probably experienced surface volcanism as recently as a billion years ago, and today has a molten inner mantle and outer core.

Urey continued his lunar studies until he was well into his 80s. Among his last scientific papers was one on lunar iron chemistry published in 1977. He died in La Jolla, California, on 5 January 1981.

Sources

Letter, Harold C. Urey to Dr. Homer E. Newell, Deputy Director, Space Flight Programs, NASA Headquarters, 19 June 1961.

Letter, Homer E. Newell to Dr. Harold C. Urey, School of Science and Engineering, University of California-San Diego, 29 June 1961.

"The Chemistry of the Moon," Harold C. Urey, Proceedings of the Lunar and Planetary Exploration Colloquium, 29 October 1958, Publication 513W3, Vol. 1, No. 3, Missile Division, North American Aviation, 1958.

"Harold Urey and the Moon," Homer E. Newell, The Moon, Volume 7, pp. 1-5, 1973.

NASA's Origins and the Dawn of the Space Age, Monographs in Aerospace History #10, David S. F. Portree, NASA History Division, September 1998.

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He Who Controls the Moon Controls the Earth (1958)

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Solar Flares and Moondust: The 1962 Proposal for an Interdisciplinary Science Satellite at Earth-Moon L4

Centaurs, Soviets, and Seltzer Seas: Mariner 2's Venusian Adventure (1962)