Riccioli Outpost (1990)

The red oval at left marks Riccioli crater, Paul Lowman's candidate site for a lunar geology/astronomy outpost. The crater is approximately round, but appears foreshortened because it is near the lunar limb. Image credit: NASA
NASA held a workshop in August 1990 to examine candidate lunar base sites as part of the Space Exploration Initiative (SEI). U.S. President George H. W. Bush had announced SEI on 20 July 1989, the 20th anniversary of the Apollo 11 Moon landing. SEI aimed to return American astronauts to the Moon to stay and to carry out the first piloted Mars expedition. For most of its first year, SEI lacked a timetable, though in November 1989, The 90-Day Study, NASA's initial SEI blueprint, scheduled the return to the Moon for as early as 2001. On 11 May 1990, Bush called for American astronauts on Mars by 2019.

One candidate lunar base site was 156-kilometer-wide Riccioli crater. Riccioli is located southwest of Oceanus Procellarum, near the edge of the Moon's disk as viewed from Earth, just west of prominent dark-floored Grimaldi basin. Named by 17th-century astronomer-priest Giovanni Battista Riccioli for himself, the crater includes slumped crust blocks (graben) overlain with ejecta from the impact that blasted out the nearby multi-ringed Orientale basin, the youngest large basin on the Moon.

Heavily degraded Riccioli crater. The red oval marks a possible outpost site on the interior uplift. Light-colored ejecta from Mare Orientale (out of shot to the southwest) is discernible over much of the crater. Image credit: NASA
Riccioli's ancient, complex geology and its position near the Moon's equator and western limb had drawn the gaze of geologist Paul Lowman. At the August 1990 workshop, he advocated for the crater's irregular interior uplift as the site for a geoscience outpost and astronomical observatory. In places, the interior uplift stands more than 800 meters above the crater floor.

Paul Lowman. Image credit: NASA
NASA put Lowman on its payroll in 1959. By some accounts, he was the agency's first geologist. He worked at NASA Headquarters in Washington, DC, then moved to the newly built NASA Goddard Space Flight Center in Greenbelt, Maryland, a Washington suburb. He trained Mercury, Gemini, and Apollo astronauts to identify and photograph Earth's geologic features from Earth orbit and participated in the development of Apollo lunar geology experiments. He wrote about future lunar mining as a member of the interagency Working Group on Extraterrestrial Resources; he also took part in an internal NASA study of a temporary lunar outpost based on Lunar Module spacecraft and other Apollo technology.

After Apollo, Lowman participated in Skylab Earth observation experiments and the Landsat Program. The Earth-orbiting Landsat automated satellites sought resources and monitored the environment on Earth.

Lowman assumed that geologist-astronauts at Riccioli outpost would have at their disposal several rovers equipped as campers. He planned three traverses within Riccioli, each about 100 kilometers long with multiple stops. The traverses would each last several days.

Traverse 1 would begin with a sample stop just outside the outpost's front door. Lowman believed that the Riccioli interior uplift might include some of the oldest lunar crust. From there, the geologist-astronauts would drive across the dark mare to sample light plains material — probable ejecta from the Orientale basin — on Riccioli's northeast rim. The Orientale ejecta, he asserted, could contain pieces of mantle material from deep within the Moon.

Lowman's Traverse 2 would explore criss-cross grabens and rilles (canyons) in search of recent volcanism. Lowman hoped that the explorers might uncover water-rich minerals they could mine.

During Traverse 3, they would sample craters with dark haloes along the Riccioli southeast rim about 50 kilometers from the outpost. Lowman believed that the dark haloes could be signs of relatively recent volcanism; that the craters they surround could be volcanic vents and the haloes erupted volcanic material. Alternately, the impacts that blasted out the craters might have exposed ancient dark deposits buried beneath Orientale basin ejecta.

Lowman expected that geologist-astronauts would build on the exploration experience they gained in Riccioli crater to rove beyond its degraded walls. Riccioli is located in the Moon's "wild west," a region of complex geology that even today is in many ways mysterious. Lowman named as geologic exploration targets within a few hundred kilometers of Riccioli the ring mountains and small mare plains of Mare Orientale; the Reiner Gamma swirls, a prominent magnetic anomaly; the Marius Hills volcanic complex, an Apollo candidate landing site; and bright Aristarchus crater.

Astronomers based at near-equatorial Riccioli outpost could, Lowman added, observe nearly the entire celestial sphere every month. He suggested that the generally level Riccioli crater floor could provide a stable platform for groups of sensitive astronomical instruments that had to be kept carefully aligned to function properly. A cluster of carefully aligned small telescopes, for example, could act as a single large telescope.

Riccioli crater's near-limb location meant that Earth would stand low in the eastern sky; low enough that at some locations the crater rim and central uplift could hide the home planet from view. Radio telescopes built out of sight of Earth could, he explained, operate without interference from terrestrial artificial and natural radio sources.

Lowman revealed a playful side when he proposed that Riccioli outpost include a bright strobe light. This could be activated when the Moon was at first-quarter phase, when it stands high and half-lit immediately after sunset for observers on Earth. The Sun would not yet have risen at Riccioli crater, so the blinking strobe would stand out against the dark part of the first-quarter lunar disk.

SEI excited scientists, engineers, and space enthusiasts, but it never gained much traction with Congress and the wider public. Because of this, it ended soon after President Bush left the Oval Office in January 1993. NASA, meanwhile, turned its efforts toward building the International Space Station in low-Earth orbit in cooperation with its long-time International Partners and Russia.

Lowman, for his part, never stopped advocating for a lunar outpost, and Riccioli crater remained his favorite candidate site. In 1996, taking into account new miniaturized space technology and capable robots, he proposed a mostly automated astronomy outpost in Riccioli crater built up using small, cheap automated landers. Lowman passed away a week after his 80th birthday on 29 September 2011.


A Site Selection Strategy for a Lunar Outpost — Science and Operational Parameters: Determining the Impact of Science and Operational Parameters for Six Sites on the Moon by Simulating the Selection Process, Conclusions of a Workshop, 13-14 August 1990, Solar System Exploration Division, NASA Johnson Space Center, Houston, Texas, pp. 31-36

"Remembering Paul Lowman," Landsat Science (Accessed 9 October 2019)

"Paul Lowman: NASA's 76-Year-Old Maverick," NASA Goddard Space Flight Center, 11 September 2007 (Accessed 9 October 2019)

More Information

As Gemini Was to an Apollo Lunar Landing by 1970, So Apollo Would be to a Lunar Base By 1980 (1968)

Harold Urey and the Moon (1961)

Mission to the Mantle: Michael Duke's Moonrise

Gemini on the Moon (1962)

Retrograde Module separation. Image credit: Jeff Bateman/David S. F. Portree
In June 1962, a little more than a year after President John F. Kennedy put the U.S. on course for the Moon, NASA's piloted spaceflight organizations agreed that Lunar Orbit Rendezvous (LOR) should be the Apollo lunar landing mission mode. LOR would employ two spacecraft: a Command and Service Module (CSM) for carrying three astronauts from Earth to lunar orbit and back again; and a Lunar Excursion Module (LEM) for landing two astronauts on the Moon and returning them to the CSM in lunar orbit. Both the CSM and the LEM would include two modules: the Command Module (CM) and Service Module (SM) in the case of the CSM, and the Descent Module and Ascent Module in the case of the LEM.

On 11 July 1962, NASA Administrator James Webb made public NASA's mode choice. He told a press conference that LOR Apollo would leave Earth on a Saturn C-5 (as the Saturn V rocket was known at the time) capable of launching 45 tons to the moon, and that the agency would also study a two-man Direct Ascent Apollo lunar landing mission launched on a Saturn C-5. In Direct Ascent, a single spacecraft would carry the astronauts from Earth to the lunar surface and back again.

NASA Administrator James Webb (left) explains NASA's decision to adopt LOR at a NASA Headquarters press conference on 11 July 1962. Seated beside Webb are (L to R) NASA human spaceflight officials Robert Seamans, Brainerd Holmes, and Joseph Shea. Image credit: NASA
Webb did not provide a justification for the two-man Direct Ascent study, though it soon became clear that it was a concession to Jerome Wiesner, chairman of the President's Science Advisory Council (PSAC). Wiesner, a Massachusetts Institute of Technology professor who had also served as PSAC chair for President Kennedy's predecessor, President Dwight Eisenhower, was not comfortable with LOR's complexity.

While NASA moved ahead with LOR, it also hired McDonnell Aircraft Company and TRW Space Technology Laboratories to study Wiesner's preferred mode. For McDonnell, manufacturer of the one-man Mercury and two-man Gemini spacecraft, the study had three aims.

McDonnell would develop a conceptual Direct Ascent Moonship design incorporating a two-man CM similar to the three-man North American Aviation (NAA) Apollo CM. When NAA contracted with NASA to build the Apollo CSM in November 1961, it had assumed that Apollo would use either Direct Ascent or Earth-Orbit Rendezvous. In both of those mission modes, the CSM would have had the honor of landing on the Moon. NAA did not welcome NASA's choice of LOR.

McDonnell would also look at using Gemini for the Direct Ascent Moon landing mission. At the time it conducted its study, Gemini's maiden flight was scheduled for launch in 1964. Known initially as "Mercury Mark II," the spacecraft, which was meant to reach Earth orbit atop a Titan II rocket, was meant to provide NASA with experience with spacewalks and rendezvous and docking ahead of Apollo.

From aft to front, the Gemini spacecraft consisted of the Adapter Module, the Service Module, and the CM. The Gemini CM, which measured 8.7 feet across its heatshield and weighed 5775 pounds, had two hatches (one per astronaut) with one forward-facing window each. Gemini could carry enough life support consumables and fuel cell reactants for a 14-day Earth-orbital mission.

Cutaway of a Gemini spacecraft. Image credit: NASA
Finally, McDonnell would determine modifications the two-man Apollo and Lunar Gemini spacecraft would need to serve as unpiloted "rescue" vehicles. NASA expected that a rescue lander, if one flew, would be landed without a crew at the target landing site ahead of the Direct Ascent mission crew's arrival.

The company proposed four two-man Direct Ascent Command Module designs. The company's conical two-man Apollo would measure 8.8 feet tall and 10.4 feet across its heat shield. (For comparison, the three-man Apollo was 10.6 feet tall and 12.8 feet across.) Interior volume would total 185 cubic feet, of which 73 cubic feet would be available for the crew.

The astronauts would enter and leave the module through a hatch with two windows located above the pilot's couch. A blow-out hatch with one window located above the co-pilot's couch would provide emergency egress. During Earth launch and reentry, lunar liftoff, and while sleeping on the Moon, the astronauts would recline in their couches facing the nose and main control panel. This would place the windows above and behind their heads.

During lunar landing, they would sit upright on their couch backs facing landing controls and view the Moon's surface through the windows. Following Earth atmosphere reentry, the two-man Apollo CM would lower to a gentle land landing on three 71-foot-diameter parachutes.

Lunar Gemini I modifications would include a beefed-up heat shield so that it could withstand reentry at lunar-return speed, improved radio systems for communication between Moon and Earth, lunar landing controls, and life support consumables stocks sufficient to support an eight-day lunar mission. The spacecraft would also include two systems for viewing of the lunar surface during landing. The right-side astronaut would recline in his couch normally (back toward heat shield and lunar surface) and deploy an external mirror for an "over-the-shoulder" surface view. The left-side astronaut would roll over in his couch and view the lunar surface directly through a transparent "viewing dome" built into his hatch. The Lunar Gemini I Command Module would weigh 6802 pounds.

Except for its Earth-landing system, Lunar Gemini II would closely resemble Lunar Gemini I. Until June 1964, NASA planned a land landing for its Earth-orbital Gemini spacecraft. The Gemini CM would deploy an steerable delta-winged paraglider during descent to Earth and glide to a touchdown on skids or wheels. McDonnell retained this system in its Lunar Gemini I design, but decided to trim weight from Lunar Gemini II by substituting a single 84-foot-diameter parachute and splashdown at sea.

Land landing in the Lunar Gemini II capsule would be not survivable; if emergency land landing became necessary, the astronauts would eject from the falling capsule after reentry and descend on personal parachutes. The Lunar Gemini II Command Module would weigh 6376 pounds.

Lunar Gemini II spacecraft configurations. Clockwise from lower left: Lunar Gemini II Command Module; Lunar Gemini II Command Module with Service Module, Terminal Landing Module, and Retrograde Module; top view of Lunar Gemini II Command Module with Service and Terminal Landing Modules; Lunar Gemini II Command, Service, and Terminal Descent Modules; and Lunar Gemini II Command and Service Modules. Image credit: Jeff Bateman/David S. F. Portree
Earth-orbital Gemini astronauts would rely on ejection seats for escape if their Titan II booster rocket malfunctioned. Lunar Gemini I and II would retain this system.

For its Lunar Gemini III design, McDonnell opted for a launch-escape tower similar to the one used on the Mercury capsule. In the event of a Titan II malfunction, the tower's solid-rocket motor would blast the Lunar Gemini III CM to safety. Couches with shock absorbers would replace the ejection seats, and three 71-foot-diameter parachutes would provide a slower, gentler descent than Lunar Gemini II's single parachute. These modifications would restore the land landing capability lost in Lunar Gemini II. All three Lunar Gemini versions could return up to 85 pounds of scientific equipment and lunar samples to Earth.

The Lunar Gemini III couches could be configured so that the astronauts could sit upright (feet toward heat shield) relative to the Moon's surface during lunar landing. New hatch windows would provide direct views of the lunar surface for both astronauts. The Lunar Gemini III CM would weigh 6453 pounds minus its launch escape tower.

McDonnell proposed that both the two-man Apollo and the Lunar Gemini CMs reach the Moon atop a stack of three propulsion/service modules. The cylindrical, 21.6-foot-diameter, 16.4-foot-tall Retrograde Module would weigh 26.9 tons with a full load (23.8 tons) of liquid hydrogen/liquid oxygen propellants. It would rest atop the Saturn C-5 rocket and its top would attach to the bottom of the Terminal Landing Module. The Retrograde Module would perform course corrections during flight to the moon, lunar orbit insertion, de-orbit, and descent to 6000 feet above the Moon, then would detach from the Terminal Landing Module and tumble away to crash on the surface (image at top of post).

Lunar Gemini II on the Moon. Image credit: Jeff Bateman/David S. F. Portree 
The Terminal Landing Module, which would perform descent to the lunar surface following Retrograde Module separation, would weigh three tons with a full load (1.7 tons) of ignite-on-contact hydrazine/nitrogen tetroxide propellants. It would measure 21.6 feet across its base, which would attach to the top of the Retrograde Module, and 19.3 feet across its top, which would attach to the bottom of the Service Module. It would measure only 6.5 feet tall; this low profile would keep the Direct Ascent lander's center of gravity near the surface, helping to ensure that it would not tip during landing on its four spindly legs.

The legs would fold against the Retrograde Module's sides under ejectable streamlined fairings during ascent through Earth's atmosphere. A compartment in the module's underside would hold 165 pounds of scientific gear for exploring the lunar surface.

The top of the Service Module would measure 10.4 feet across if attached to a two-man Apollo CM and 8.7 feet across if joined to a Lunar Gemini CM. It would stand 8.5 feet tall and measure 19.3 feet across its base, where it would attach to the top of the Terminal Landing Module. The Service Module would perform lunar liftoff and course corrections during the flight home to Earth. It would weigh 11.7 tons with a full load (9.7 tons) of hydrazine/nitrogen tetroxide propellants.

In addition to propulsion systems, the Service Module would carry 1148 pounds of CM support equipment, including Gemini fuel cells to provide electricity and drinking water, a surface-mounted radiator for cooling, life-support oxygen tanks, and two boom-mounted radio dish antennas.

The Lunar Gemini II Service Module rocket motor ignites, boosting the Command Module off the Moon. Image credit: Jeff Bateman/David S. F. Portree
McDonnell found that both the two-man Apollo and the Lunar Gemini could serve a rescue function. The automated rescue spacecraft might home in on a radio beacon mounted on a pre-landed automated Surveyor lander. It could remain dormant on the lunar surface for up to 30 days awaiting arrival of the crew. If the piloted Direct Ascent spacecraft became damaged during landing or malfunctioned after touchdown, the astronauts would walk to the rescue spacecraft and use it to return to Earth.

Rescue modifications would include a guidance system similar to that under development for the automated Surveyor lunar soft-lander; additional liquid oxygen/liquid hydrogen fuel cell reactants (5.7 pounds per day) for powering electric heaters in the Command Module during the 14-day lunar night; additional water (6.5 pounds per day) for evaporative cooling during the 14-day lunar day; and a propellant-saving Surveyor-type "direct descent" landing profile with no stop in lunar orbit before descent to the lunar surface.

NASA/PSAC differences over the Apollo mode choice became public midway through the two-man Direct Ascent study, when Wiesner and Webb argued in front of President Kennedy and reporters during a presidential tour of NASA Marshall Space Flight Center (11 September 1962). Soon after McDonnell submitted its report, NASA reaffirmed its decision to go with LOR (24 October 1962).

Webb threatened to resign if NASA's choice were overruled, and Wiesner, sensing that Kennedy would back his NASA Administrator, acquiesced. On 7 November, the agency finalized its LOR decision by awarding the contract to build the LEM to Grumman Aircraft Engineering Corporation in Bethpage, Long Island.


Direct Flight Apollo Study, Volume I: Two-Man Apollo Spacecraft and Volume II: Gemini Spacecraft Applications, McDonnell Aircraft Corporation, 31 October 1962

More Information

Plush Bug, Economy Bug, Shoestring Bug (1961)

Space Station Gemini (1962)

Chronology: Venus 1.0

Digital elevation model of one hemisphere of Venus based on Magellan radar mapper data. Blue and purple signify low elevations, shades of green signify intermediate elevations, and red, pink, and tan signify high elevations. The tallest mountain on Venus, Skadi Mons, is part of Maxwell Montes, the light colored "tadpole" feature near the top of the image. Image credit: NASA  
Chronology is the exoskeleton of history; without its supporting structure, events collapse in an unrecognizable heap. Because this blog presents historical spaceflight plans and their context in random order, without the benefit of an overarching chronology, I periodically write a post which places in chronological order posts in this blog that cover a specific subject area.

This time around, the subject area is Venus. Until the early 1960s, many scientists held out hope that Venus might support life. Even before Mariner II flew past it (14 December 1962), however, scientists had begun to suspect that close examination would undermine their visions of a clement Venus. The cloudy planet soon became an object lesson in the importance of greenhouse gases in planetary atmospheres.

Among the planets, no world has received more visitors than Venus. From the 1960s until the 1980s, Venus was the main planetary exploration target of the Soviet Union; no country placed more spacecraft on the Venusian surface.

Mariner 10 was the first spacecraft to fly by Venus and use it as a gravity-assist way station (5 February 1974); that is, it used the planet's gravity and orbital momentum to change its course and speed, enabling it to conduct three Mercury flybys in 1974-1975. The twin Soviet Vega spacecraft each used a Venus gravity-assist in 1985 to gain enough energy to reach Comet Halley in 1986; during their Venus flybys, they released combination lander/balloon payloads.

Venus helped to rescue the NASA robotic exploration program in the late 1980s. The U.S. space agency had intended to launch the Galileo Jupiter orbiter and probe into low-Earth orbit in May 1986 attached to a powerful Centaur G-prime upper stage in the payload pay of a Space Shuttle Orbiter. Astronauts would have released the stage and spacecraft, then the former would have ignited to boost the latter directly to Jupiter, with arrival in December 1988.

After the Challenger Space Shuttle failure (28 January 1986), however, Centaur G-prime, which burned liquid hydrogen fuel with liquid oxygen oxidizer, was judged to be too volatile to carry on board a piloted spacecraft. In its place, NASA opted for a solid-propellant upper stage and a complex Venus-Earth-Earth Gravity Assist (VEEGA) trajectory. Following launch on board the Shuttle Orbiter Atlantis (18 October 1989), a Venus flyby (10 February 1990) put Galileo on course for Earth gravity-assist flybys in December 1990 and December 1992 with arrival at Jupiter in December 1995.

Galileo had been expected to be the first U.S. planetary spacecraft launched since Pioneer Venus Multiprobe (PVM) left Earth in August 1978; its new reliance on the VEEGA trajectory meant, however, that NASA had to shuffle its planetary mission schedule. Because Galileo needed to use the October 1989 launch window for a direct flight to Venus, the Magellan Venus radar mapper lifted off on board Atlantis (4 May 1989), orbited the Sun one-and-a-half times, and entered Venus polar orbit (10 August 1990). Missions to Venus thus bracketed a nearly 11-year drought in U.S. planetary mission launches.

In recent years, we have seen proposals for piloted Venus orbiter and atmosphere missions. These mark a renewal of interest that began in the 1950s and continued through the 1960s. Had those early plans gone ahead, NASA might have launched astronauts on Venus flyby and orbiter missions in the 1970s and early 1980s. Recent proposals and 1960s proposals have in common reliance on robots to explore the harsh Venusian surface; no humans would land there.

Venus is mentioned with (perhaps surprising) frequency throughout this blog. What follows is a chronological list of links to posts with a significant Venus exploration component.

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

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

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

Venus as Proving Ground: A 1967 Proposal for a Piloted Venus Orbiter

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

Apollo Ends at Venus: A 1967 Proposal for Single-Launch Piloted Venus Flybys in 1972, 1973, and 1975

Floaters, Armored Landers, Radar Orbiters, and Drop Sondes: Automated Probes for Piloted Venus Flybys (1967-1968)

Things to Do During a Venus-Mars-Venus Piloted Flyby Mission (1968)

Two for the Price of One: 1980s Piloted Missions with Stopovers at Mars and Venus (1969)

After Venus: Pioneer Mars Orbiter with Penetrators (1974)