Could the Space Voyages in the Film and Novel "2001: A Space Odyssey" Really Happen? (Part 2)

The good ship Discovery from the classic 1968 motion picture 2001: A Space Odyssey. From right to left, we see the pressure sphere housing the crew, a train of six propellant modules, the communications complex, four more linked propellant modules, and the propulsion module. Image credit: Turner Entertainment/Metro Goldwyn Mayer.

When I set out back in June to write about a pair of plans for accomplishing the space voyages portrayed in the classic 1968 film and novel 2001: A Space Odyssey, I assumed that I could get the job done in a single post. I should have known better; not only are the plans complex, there is much to say about the film and book that inspired them. Now I plan a total of three posts, of which this is the second.

This post deviates from my original intent in another way; it does not describe a real spaceflight plan inspired by and meant explicitly to reproduce a capability portrayed in the movie or book 2001. Instead, it describes how the spaceship Discovery, the setting for much of the action in the second half of the film 2001, was intended to propel itself between planets. This will lay useful groundwork for the third and final post in this little series.

Along the way, by way of explaining the details of the cinematic Discovery's propulsion system, I will sum up the state of advanced nuclear propulsion research at NASA Lewis Research Center (LeRC) in the early 1970s. During the same period, President Richard Nixon, the Congress, and NASA itself brought down the ax on the joint NASA/Atomic Energy Commission (AEC) nuclear-thermal propulsion development program.

The novel 2001 (written by Arthur C. Clarke) and the film 2001 (based on a screenplay jointly written by director Stanley Kubrick and Clarke) differ as to how Discovery is portrayed. There are in fact two different Discovery spacecraft.

Discovery in the novel 2001: A Space Odyssey measures more than 300 feet long from its forward-mounted spherical pressure hull to its aft-pointing plasma jet propulsion units. Immediately behind the pressure hull is a cluster of four cylindrical hydrogen propellant tanks and, behind them, a complex system of cooling fins. The fins form a "V" with the broad top of the "V" facing forward and a shielded nuclear reactor at its point.

The nuclear reactor would generate electricity for "focusing electrodes" in Discovery's plasma jets. These would heat the hydrogen and expel it to generate thrust. Judging by Clarke's description, the Discovery plasma jet design was apparently based on the same principle as the jets that propelled the Aries-1B Moon shuttle I discussed in my last post.

The cooling fins, which Clarke described as "[v]eined with a delicate tracery of pipes for. . .cooling fluid," were meant to radiate excess heat from Discovery's nuclear reactor into space. They would, he wrote, "glow cherry red" when the ship's plasma jets operated at full thrust, but would become "dark and cool" after the jets were switched off.

Discovery of the film 2001 lacks any sign of cooling fins. Partly this is because Kubrick worried that his audiences would wonder why a spacecraft operating in the vacuum of space would need wings, but Kubrick's evolving aesthetic vision also played a part. Ultimately, he sought a frail-looking, skeletal Discovery.

The largest single component of the cinematic Discovery is the propulsion module at its aft end, with the roughly 40-foot-diameter pressure sphere at the spacecraft's forward end coming in a close second. In between these is a train of linked propellant modules, each about 20 feet long. From a distance, these resemble vertebrae. About halfway along Discovery's "spinal column" is a communications complex with three Earth-pointing dish antennas, one large and two small.

Sadly, we never see Discovery's engines in action in the film 2001. We might have witnessed the slender spacecraft slowly turn to point its engines forward as it approached Jupiter, then watched in wonder as they lit up to slow Discovery so that the giant world's gravity could capture it into orbit.

Discovery's engines, 700 feet behind the pressure sphere bearing the crew. Image credit: Turner Entertainment/Metro Goldwyn Mayer.

The timing for such a maneuver would, however, have been awkward from a story point of view; having just lobotomized the HAL 9000 computer, the "brain and central nervous system" of his ship, it seems doubtful that David Bowman, the sole surviving member of Discovery's five-person crew, could have had enough time to prepare for and carry out a successful deceleration maneuver. Kubrick opted instead to skip the Jupiter capture maneuver and proceed directly to his film's enigmatic, mind-bending climax.

Despite never seeing it operate, we have at our disposal information about how the cinematic Discovery's propulsion system was meant to work. The individual most responsible for this was Frederick Ordway.

Ordway was born in 1927. He graduated Harvard in 1949 with a Bachelor of Science degree, then earned certificates in physics and geosciences at the Sorbonne. In 1950, while studying in Paris, he attended the first International Astronautical Congress, where he met Clarke, whose six-decade writing career was just taking off.

In the 1950s, Ordway worked for New York-based aviation companies, generally in the area of rocketry. Toward the end of the decade, at the urging of Wernher von Braun, he relocated to Huntsville, Alabama, to work at the Army Ballistic Missile Agency (ABMA). Ordway became a NASA employee in July 1960, when ABMA became the nucleus around which NASA Marshall Space Flight Center crystallized.

In 1963, Ordway published the first of more than 20 books he would author in his lifetime. Titled Conquering the Sun's Empire, it was a popular-audience vision of humankind's future in the Solar System illustrated by his friend and collaborator, the artist Harry Lange.

In January 1965, Clarke introduced Ordway and Lange to Kubrick, who hired them both in mid-February to provide him with technical advice. The Discovery design in the novel 2001, known informally as the "dragonfly," was based on Lange pre-production illustrations developed during early discussions between Ordway, Lange, Clarke, and Kubrick.

A major part of Ordway's contribution to 2001: A Space Odyssey involved visiting aerospace companies and NASA centers, where he interviewed experts in spaceflight-related fields and collected advance-planning documents in an effort to ensure that Kubrick's film would present a believable vision of spaceflight at the turn of the millennium. He also became a spokesperson for the film, which had aroused intense interest in the aerospace community.

25 September 1965: Frederick Ordway (left, in white) joins a few notables for a tour of the British studio where 2001: A Space Odyssey was filmed. From left to right, they are: Donald "Deke" Slayton, NASA Director of Flight Crew Operations; Arthur C. Clarke; Stanley Kubrick; and George Mueller, NASA Associate Administrator for Manned Space Flight. Image credit: The Stanley Kubrick Archives.

Ordway's formal involvement with 2001 production ended after nearly two years, in December 1966, 15 months ahead of the film's world-wide release in April 1968. Ordway's time on Kubrick's payroll coincided with NASA's peak funding year.

In 1965-1966, it was still reasonable to assume that the U.S. space agency would in the 1970s, 1980s, and 1990s expand upon the achievements of the 1960s Apollo Program. Thirty-five years seemed to be plenty of time to build a giant artificial-gravity Earth-orbital space station, establish a lunar base, land humans on Mars, and launch humans and intelligent, talking computers into the outer Solar System.

According to Ordway, the cinematic Discovery was meant to have a "Cavradyne" gas-core nuclear-thermal propulsion system. He described it in a 1970 Spaceflight magazine article on the spacecraft of 2001. His description subsequently appeared as design notes in a set of Discovery blueprints drawn by graphic artist Shane Johnson. Ordway himself excerpted his 1970 description of Discovery's propulsion system in a 1982 paper. I will describe the fictional Cavradyne system shortly; before that, though, I will provide for it some "real world" context.

At the time Ordway published his 1970 article, NASA and the Atomic Energy Commission (AEC) had for more than a decade worked together to develop nuclear-thermal rockets. NASA and the AEC emphasized solid-core nuclear-thermal propulsion; gas-core nuclear engines of the type envisioned for Discovery of the film were widely seen as exotic and perhaps impossible.

Nuclear rocketry had ceased to be a national priority as early as 1963-1964, when Presidents John F. Kennedy and Lyndon Baines Johnson grounded the Reactor In-Flight Test (RIFT) project, which had optimistically aimed to launch a solid-core nuclear rocket engine into Earth orbit on a Saturn V rocket in 1967. Nevertheless, many within NASA remained hopeful in 1970 that solid-core nuclear rocket stages might navigate the Earth-Moon system in the mid-to-late 1970s, as described in NASA's 1969 Integrated Program Plan (IPP). I discuss the IPP elsewhere in this blog — please see the "More Information" links at the end of this post.

During the 1960s, low-level gas-core engine studies took place under the aegis of the Advanced Reactor Concepts Section at NASA Lewis Research Center (LeRC) in Cleveland, Ohio. Robert Ragsdale, chief of the Section, performed gas-core research and analysis with his LeRC colleagues and supervised small contractual studies at more than a dozen corporations and universities across the United States. It is possible that Ordway contacted Ragsdale or researchers his Section funded as he gathered information for Kubrick, though no record of such a meeting is known to exist.

A solid-core nuclear-thermal rocket, the most basic kind, can be seen as a nuclear reactor with an open-cycle cooling system. A reflector focuses neutrons radiated from solid uranium fuel elements back into the reactor core, causing nuclear fission to occur. The fuel elements grow hot. Left to themselves, they would melt catastrophically; however, a turbopump drives propellant (typically cryogenic liquid hydrogen) into the reactor. The propellant turns to hot plasma upon contact with the fuel elements and vents into space through a bell-shaped nozzle, generating thrust.

A major advantage of a nuclear-thermal rocket engine over a chemical-propellant rocket engine (for example, the Space Shuttle Main Engine) is in the area of specific impulse, or the ratio of a unit of propellant expended to a unit of thrust generated. Specific impulse, abbreviated Isp, is expressed in seconds. The best Isp attainable using liquid hydrogen/liquid oxygen chemical propellants is in the neighborhood of 450 seconds, while the best solid-core nuclear Isp is in theory roughly twice that — on the order of 800 to 1000 seconds.

Nuclear-thermal Isp is dependent on the temperature of the fuel elements. Achieving an Isp much greater than about 1000 seconds using a solid-core nuclear-thermal engine rapidly becomes infeasible because the propellant can no longer cool the fuel elements enough to prevent them from melting. Supplemental cooling — for example, coolant flowing through plumbing within the engine to pick up its excess heat and then through large cooling fins to radiate that heat into space — becomes increasingly necessary, boosting spacecraft weight.

The NASA LeRC team found that, for high Isps as high as 1000 seconds, the heaviest element of a solid-core nuclear-thermal engine system would be its cooling system. Increased weight would mean more costly heavy-lift rockets to place the spacecraft's components into space for assembly as well as reduced engine performance.

Gas-core nuclear-thermal propulsion promised a way around the "temperature barrier." In a gas-core nuclear engine, uranium would take the form of an incandescent ball of plasma in which nuclear fission would take place. The uranium fuel element would operate at a temperature far above the point at which a solid-core uranium fuel element would vaporize — and that would be exactly as planned.

Ragsdale's group emphasized open-cycle gas-core nuclear propulsion over closed-cycle gas-core nuclear propulsion. The open-cycle plasma ball would "float" in a "stagnant region" that would fill about 40% of a spherical engine chamber about a dozen feet across. Hydrogen propellant would flow around the plasma ball, be heated until it also became a plasma, and then vent through a nozzle into space.

No physical wall would separate the uranium plasma from the hydrogen, a deletion meant to reduce engine mass and complexity. A thin uranium wire would feed slowly into the plasma ball to make up for the small amount of uranium plasma — about 0.25% of the propellant flow at any particular moment — that would escape the open-cycle gas-core nuclear-thermal engine with the hydrogen propellant. As the open-cycle engine was shut down, the entire uranium plasma ball, diluted by hydrogen, would gradually vent from the nozzle into space.

A closed-cycle gas-core nuclear-thermal system — sometimes called a "nuclear lightbulb" — would include a physical barrier between the uranium plasma ball and the hydrogen propellant. The barrier would add weight and complexity, and might create temperature limitations; it would, however, also prevent uranium plasma from escaping into space. Presumably the design would also make engine start-up — hydrogen flow initiation for cooling followed by creation of a stable uranium plasma ball in which fission would occur — a simpler task.

Using mathematical models, Ragsdale's group studied open-cycle gas-core nuclear-thermal engines with Isps of between 1500 and 3000 seconds. These could, they determined, operate without supplemental cooling.

To reach Isps beyond 3000 seconds, the plasma ball would need to become so hot that surrounding structure would melt and fail without supplemental cooling. Even with supplemental cooling, seemingly insurmountable temperature barriers would soon be reached. For an Isp of 5000 seconds, for example, the core temperature would run at about 22,000 K (about 39,000° F, or 21,700° C); that is, about four times the temperature of the Sun's surface and well above the melting point of all known materials.

Ragsdale's group found a surprisingly simple partial solution to the melting problem. The hydrogen propellant would enter the spherical chamber containing the uranium plasma ball through pores or slots. Seeding the hydrogen with tungsten particles, each roughly the size of those making up cigarette smoke, would help it to absorb heat, preventing all but about 0.5% of the plasma ball's thermal radiation from reaching the inner chamber wall. The resulting increased hydrogen temperature would also mean increased engine thrust.

About 7% of the uranium plasma ball's energy would, however, emerge as gamma and neutron radiation, pass unimpeded through the hydrogen/tungsten particle propellant mix, and heat the chamber wall and surrounding structures. Research had found that, because of this, some level of supplemental cooling would inevitably be required to prevent destruction of the gas-core engine.

Simplified cutaway of an open-cycle gas-core nuclear rocket engine. A pressure vessel provides structural strength and a beryllium oxide (BeO) moderator absorbs neutrons radiated from the uranium plasma, limiting pressure shell and adjacent spacecraft structure heating. Coolant moves through passages in the moderator to provide supplemental cooling. After passing through the moderator, the coolant flows through a space radiator then returns to the moderator to pick up more heat. A turbopump drives hydrogen propellant through the inner, "porous" wall. Uranium enters the plasma ball in the form of a "wire" roughly the diameter of a pencil lead to make up for the small amount carried off by the hydrogen plasma, which vents into space through the nozzle at right to generate thrust. Not shown is the system for introducing tungsten particles into the hydrogen. An engine of this basic design could in theory yield Isps of between 3000 and 5000 seconds. Image credit: NASA.

Citing more than a decade of research, Ragsdale predicted confidently that open-cycle gas-core nuclear-thermal propulsion would be confirmed to be feasible within just a few years. It is important to note, however, that the gas-core nuclear-thermal engine studies explored in this post were of necessity preliminary due to limited research funding. One consequence of this is that some study results are inconsistent and many are perhaps optimistic.

Ragsdale pointed to planned 56-day astronaut stays on board Skylab in Earth orbit when he proposed a 60-day round-trip piloted Mars mission with a spacecraft mass of 2250 tons in Earth orbit at mission start. Of this, the gas-core engine would account for from 50 to 250 tons and hydrogen propellant about 1500 tons. He noted that, if it were determined that astronauts could remain healthy for up to 80 days in space, then extending the Mars voyage duration accordingly would half the quantity of hydrogen propellant the gas-core nuclear-thermal Mars spacecraft would expend during its round-trip journey.

NASA LeRC researchers envisioned 80-day gas-core nuclear-thermal "courier" Mars missions. These would travel to Mars in 40 days and then return to Earth in 40 days. The spacecraft would linger near Mars only long enough to "jettison" a forward-mounted payload.

Like so many advanced spaceflight concepts, NASA LeRC gas-core propulsion never got the conceptual artwork it deserved — until now. This illustration, by artist William Black, is based on a crude line drawing that appears in early 1970s NASA LeRC gas-core propulsion reports. It shows the 80-day "courier" spacecraft. The NASA LeRC line drawing indicated a need for radiator fins, but did not show their shape or extent; Black has made them resemble the "V"-shaped radiator configuration of Discovery in the novel 2001. Doing so places them within the conical radiation shadow created by the shield at the front of the gas-core engine (see image below) so that they do not reflect radiation toward the crew. Please click on image to enlarge.

Closeup of an open-cycle gas-core nuclear-thermal rocket engine based on NASA LeRC design concepts as envisioned by artist William Black. The large disc at left is a shadow shield for protecting the spacecraft crew from radiation produced by the engine. The cage-like truss structure surrounds the uranium storage and feed system and tungsten particle feed, hydrogen feed, and coolant circulation lines. Liquid hydrogen cools the silver part of the engine bell, becoming a hot gas; it then drives turbopumps (colored gold) that pump hydrogen into the spherical gas-core engine chamber.

Ragsdale wrote that the Space Shuttle, with its planned ability to routinely and cheaply launch payloads to Earth orbit, would help to make possible piloted interplanetary spacecraft with gas-core nuclear-thermal engines. This observation is ironic because, in testimony before a February 1971 Congressional hearing on the future of U.S. nuclear rocketry, NASA Acting Administrator George Low had used the need to fund Shuttle development as an excuse for slashing nuclear propulsion funds in Fiscal Year 1972 to a level barely sufficient to close out the program.

In his January 1972 article, Ragsdale wrote that his group had big plans for gas-core engine development in the 1972-1975 period. As it turned out, however, the Nixon White House and NASA officials announced while his article was still current that they had slashed all funding for nuclear-thermal rocket research from the Fiscal Year 1973 NASA budget. NASA and the AEC backed out of the nuclear-thermal propulsion business by the end of 1973.

Now we return to the world of 2001: A Space Odyssey. Ordway's conjectural Cavradyne engine, a closed-cycle gas-core system, was a "cavity reactor only several feet across." A plasma ball with a temperature of about 11,400 K (about 20,000° F, or 11,100° C) would float at the center of a graphite inner container that would pass heat but not neutrons. Hydrogen would flow between the graphite container and the inner wall of the cavity reactor outer shell, then would vent as high-temperature plasma through a nozzle into space.

Nuclear-propulsion spacecraft designs are usually shaped at least in part by the need to keep astronauts well away from sources of radioactivity. The cinematic Discovery's length of 700 feet reflected the presence — judging from the external configuration of its propulsion units — of at least three and possibly six Cavradyne engines. One can speculate that each engine was meant to have a shield at its forward end, creating overlapping radiation shadows that would encompass the pressure sphere bearing the crew.

Neither Ordway nor Clarke provided detailed performance data for their Discovery spacecraft. The voyage durations they mention do, however, imply high-performance propulsion.

In a late 1965/early 1966 draft of the 2001 screenplay, for example, Discovery's trip time to Saturn with a gravity-assist at Jupiter is given as 257 days. In Clarke's novel, Discovery reaches Jupiter in about six months and then proceeds onward to Saturn. In a draft of the novel which has Jupiter as Discovery's goal, excerpted in Clarke's 1972 book The Lost Worlds of 2001, the one-way trip-time is given as 219 days. These trip times are consistent with the Earth-Mars trip times in NASA LeRC conference papers and reports on gas-core nuclear-thermal engines.

The last and next-to-last images in this post are Copyright © William Black (http://william-black.deviantart.com/) and are used by kind permission of the artist.

Sources

2001: A Space Odyssey, draft screenplay by Stanley Kubrick and Arthur C. Clarke, p. c15d, 11/1965.

Kubrick, Stanley, and Arthur C. Clarke, 2001: A Space Odyssey, directed by Stanley Kubrick, Metro Goldwyn Mayer, April 1968.

The Lost Worlds of 2001: The Ultimate Log of the Ultimate Trip, Arthur C. Clarke, New York: Signet, January 1972, pp. 130-132.

"Part B: 2001: A Space Odyssey in Retrospect," Frederick I. Ordway, III; Science Fiction and Space Futures, Eugene E. Emme, editor, AAS History Series, Volume 5, San Diego: Univelt, 1982, pp. 47-105.

2001: A Space Odyssey, Arthur C. Clarke, New York: New American Library, October 1999, pp. 98-99, 105, 190-191.

The 2001 File: Harry Lange and the Design of the Landmark Science Fiction Film, Christopher Frayling, London: Rare Art Press, 2015, pp. 210-211, 217, 226, 228-231.

U.S.S. Discovery: Manned Nuclear Exploration Vessel (Registry XD-1) Spacecraft Interior Blueprints and Exterior Plans, Shane Johnson, no date (c. 1985), Sheets 1, 3, and 5.

"Crew Radiation Dose from a Gas-Core Nuclear Rocket Plume," NASA TM X-52832, C. Masser, NASA Lewis Research Center; paper presented at the Sixteenth Annual Meeting of the American Nuclear Society in Los Angeles, California, 28 June-2 July 1970.

"Gas-Core Rocket Reactors - a New Look," NASA TM X-67823, R. Ragsdale and E. Willis, NASA Lewis Research Center; paper presented at the Seventh AIAA Joint Specialist Conference in Salt Lake City, Utah, 14-18 June, 1971.

"To Mars in 30 Days by Gas-Core Nuclear Rocket," R. Ragsdale, Astronautics & Aeronautics, January 1972, pp. 65-71.

"Reactor Moderator, Pressure Vessel, and Heat Rejection System of an Open-Cycle Gas-Core Nuclear Rocket Concept," NASA TM X-2772, M. Taylor, C. Whitmarsh, P. Sirocky, and L. Iwanczyk, NASA Lewis Research Center, July 1973.

Humans to Mars: Fifty Years of Mission Planning, 1950-2000, NASA SP-2001-4521, Monographs in Aerospace History #21, David S. F. Portree, Washington: NASA, February 2001, pp. 33-52.

More Information

Could the Space Voyages in the Film and Novel 2001: A Space Odyssey Really Happen? (Part 1)

Could the Space Voyages in the Film and Novel 2001: A Space Odyssey Really Happen? (Part 3)

The Last Days of the Nuclear Shuttle (1971)

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

On the Moons of Mighty Jupiter (1970)

Touring Titan by Blimp & Buoy (1983)

The Challenge of the Planets, Part Three: Gravity

Could the Space Voyages in the Film and Novel "2001: A Space Odyssey" Really Happen? (Part 1)

An advanced LANTR Moon shuttle departs low-Earth orbit. Image credit: Pat Rawlings/NASA.

The film and novel 2001: A Space Odyssey changed my life. I know, that sounds overwrought, but it's true. I was six years old in April 1968, when the classic collaboration between science fiction author Arthur C. Clarke and film director Stanley Kubrick hit movie screens around the world. By that point in my young life, I had been reading for three years. I knew that I liked science — especially geology — so a "science fiction" film sounded intriguing.

By the time the movie drew to a close, I had become a spaceflight fan and a science fiction buff. I remain so afflicted today. (I expect that the existence of this blog makes the "spaceflight fan" part kind of obvious.)

The film 2001 is enigmatic, with mostly banal dialog and an ending that left many who saw it in its first run feeling confused and even cheated. Clarke's novel fills in gaps, but its narrative differs from the cinematic narrative. For example, in the movie 2001, Jupiter is the spaceship Discovery's destination; in the book 2001, the natural wonders of the Saturn system as understood in 1968 are used to good effect. None of this ambiguity troubled me; in fact, the mysteries stoked my young imagination.

Arthur C. Clarke (left) and Stanley Kubrick on the Aries-1B Moon shuttle passenger cabin set. Image credit: The Stanley Kubrick Archives.

This background explains why a pair of technical papers caught my attention as the year 2001 approached and passed. Nuclear propulsion engineers at NASA's Lewis Research Center (now Glenn Research Center) in Cleveland, Ohio, authored both papers. They described ways that the piloted spaceflight capabilities portrayed in the film and book 2001 might be made reality using technology and techniques that are either already in existence or are plausibly foreseeable.

In the first paper, first published in 1997 and subsequently lightly revised, Stanley Borowski and Leonard Dudzinski looked at how a 24-hour voyage to a lunar surface base might be accomplished using Nuclear Thermal Rocket (NTR) propulsion and liquid oxygen (LOX) mined from the Moon. For comparison, Apollo spacecraft needed more than three days to travel from Cape Kennedy to lunar orbit.

The second paper is much more ambitious, but also more speculative. It offers a design and operational scenario for a nuclear-fusion-propulsion spacecraft named Discovery II which could reach Jupiter orbit in just four months and Saturn orbit in seven. I will discuss it in my next two posts.

The film and book 2001 both begin with a band of man-apes who are having a tough time of it. They grub in the dust for bits of vegetation beside competing quadruped herbivores and huddle together at night listening to screeching big cats, for whom they make easy prey.

The book focuses on a hominid named Moonwatcher. Some time after an intellect-boosting encounter with an alien black monolith, he grasps the related concepts of tool-use and hunting. Soon his entire band wields bone clubs. They hunt the unsuspecting herbivores, drive off the big cats, and make war on a technologically backward rival band.

After murdering the rival band's leader, Moonwatcher of the film 2001 hurls his club triumphantly at the sky, where it becomes an Earth-orbiting satellite bearing nuclear warheads. In a heartbeat we leap over three million years of human evolution and technology advancement.

A more hopeful sign of advanced technology appears — a gleaming white space plane in Pan American Airlines livery. On board is Dr. Heywood Floyd, a high-level bureaucrat on a mission for the United States Astronautics Agency (USAA). National security, the novel 2001 explains, requires that he fly with only a pilot, co-pilot, and stewardess for company.

USAA is evidently a NASA successor organization. One can speculate that, in the 2001 timeline, a well-funded NASA worked with large commercial entities and handed off certain of its roles as, with NASA aid, those commercial entities succeeded in proving themselves capable of providing necessary spaceflight services. Along the way, NASA handed off aeronautical research (the first "A" in the acronym NASA) and became largely focused on advanced spaceflight development and scientific exploration. This prompted a name change.

The Pan Am space plane deposits Floyd at a wheel-shaped artificial-gravity international space station. It is the fifth in a series, so is called Space Station V. There Floyd confronts members of a rival band — a group of Soviet scientists on their way home from the Moon — and transfers to a near-spherical Aries-1B Moon shuttle to begin his journey to the U.S. base in 150-mile-wide Clavius crater.

Aries-1B Moon shuttle. Image credit: Turner Entertainment/Metro Goldwyn Mayer.

In the book 2001, the 30-passenger Moon shuttle's "low-thrust plasma jet" propulsion system operates for "more than 15 minutes" to begin the 25-hour voyage to the Moon. Floyd, alone on board with a pilot, co-pilot, steward, stewardess, and two engineers, hears the "whistling" of the "electrified" plasma jets. He feels the acceleration they impart to the Moon shuttle as a "mild" pressure pushing him down into his seat.

In their 1997 paper, Borowski and Dudzinski dubbed their Moon shuttle propulsion system LANTR, which stands for "LOX-Augmented Nuclear Thermal Rocket." They envisioned that LANTR propulsion would form a critical component of a cislunar transportation infrastructure that ultimately would include multiple interdependent vehicles and a Lunar Oxygen (LUNOX) mining and refining base near the Apollo 17 landing site at Taurus-Littrow on the southeast edge of Mare Serenitatis.

LUNOX, the NASA Lewis nuclear propulsion engineers explained, was likely to become the first large-scale space commodity. The "orange soil" Apollo 17 explorer Harrison Schmitt kicked up on the flank of Shorty Crater — which, it turns out, occurs at many places on the Moon — would, they estimated, make a rich feedstock for LUNOX refining, with every 25 tons of the volcanic glass-rich dirt collected and processed yielding a ton of LUNOX. For comparison, about 327 tons of more typical lunar surface material would need to be mined and refined to produce a ton of LUNOX.

The LANTR architecture, based on a NASA Lewis Nuclear Thermal Rocket (NTR) architecture developed for the abortive Space Exploration Initiative (1989-1993) of President George H. W. Bush, would evolve over time. It would not at first use LUNOX, reach the Moon in a day, or include reusable vehicles.

Borowski and Dudzinski sought to reduce the cost of their Earth-to-low-Earth-orbit (LEO) launches by exploiting then-existing Space Shuttle hardware and facilities. A pair of Shuttle-Derived Launch Vehicles (for example, Shuttle-C), each capable of placing a 66-ton payload into 407-kilometer-high LEO, would suffice to launch an expendable "two-tank" NTR stage, expendable piloted lunar spacecraft, and cargo.

Shuttle-C in its most basic form: an expendable cargo canister with a two-engine Shuttle boat-tail replaces the Space Shuttle Orbiter. Image credit: NASA.

The first Shuttle-C payload, the 24-meter-long "core stage," would comprise a pair of NTR engines, attitude control and docking systems, and a 7.6-meter-diameter, 17.5-meter-long insulated, meteoroid-shielded tank with 49.3 tons of cryogenic liquid hydrogen (LH2) inside. The engines would serve as both electricity generators and rocket motors. Because they would have two roles, or "modes," Borowski and Dudzinski dubbed them Bimodal Nuclear Thermal Rocket (BNTR) engines.

The BNTR engine's basic design would resemble that of NTR engines going back to the 1950s. LH2 would serve double duty as nuclear-fission reactor coolant and rocket propellant. After passing through and cooling the reactor, the hydrogen, now hot and gaseous, would vent into space through a bell-shaped nozzle to produce thrust.

The second Shuttle-C payload would comprise a 4.6-meter-diameter, nine-meter-long tank with nine tons of LH2, an adapter for linking with the core stage, and a conical crew capsule with four astronauts on board. It would also include a second spacecraft: a 44-ton LH2/LOX chemical-propulsion Lunar Landing Vehicle (LLV) with a five-ton crew cabin and nine tons of cargo bound for the lunar surface.

The two Shuttle-C payloads would dock in LEO, forming what Borowski and Dudzinski called a Lunar Transfer Vehicle (LTV). With the LLV attached, it would measure 46 meters in length. Its twin BNTR engines would heat and expel LH2 for 47.5 minutes to place the LTV/LLV combination on course for an Earth-moon voyage lasting 84 hours.

At the end of this cislunar journey, the BNTR engines would fire a second time so that the Moon's gravity could capture the LTV/LLV combination into 300-kilometer-high orbit. The crew would board the LLV and descend to the lunar surface with their nine tons of cargo, which would include equipment for mining, refining, and storing LUNOX, as well as scientific gear and lunar base components.

The crew would spend 45 days on the Moon living out of the LLV. They would then pilot the LLV back to lunar orbit, transfer to the LTV capsule, cast off the spent LLV, and fire the BNTR engine pair to depart lunar orbit for an 84-hour journey to Earth.

Near Earth, the crew capsule would detach from the LTV and reenter the atmosphere directly. The rest of the LTV would swing by Earth and fire its BNTR engines briefly to boost itself into a Sun-centered disposal orbit. In total, the LTV BNTR engines would operate for 61.4 minutes during a 54-day round-trip lunar mission.

Borowski and Dudzinski also described one-way cargo missions derived from their piloted architecture. Twenty-five tons of additional cargo would replace the crew cabin and propellants for boosting the LLV back to lunar orbit, bringing total cargo delivered to the Moon's surface to 34 tons.

LUNOX production would ramp up with each successive expendable LTV/LLV lunar mission. In lockstep with the increasing supply of LUNOX, NASA would upgrade the cislunar transportation system so that, after an unspecified number of flights, it would evolve into Borowski and Dudzinski's reusable LANTR architecture. The LANTR architecture would, they explained, support routine weekly 24-hour Earth-Moon "commuter" flights.

By then, LUNOX production would amount to 10,878 tons per year. Of this, reusable Earth-bound LANTR LTVs would use 4888 tons, while reusable LLVs for transporting LUNOX, crews, and cargoes between the LUNOX surface base and a lunar orbit propellant depot would expend 5990 tons.

The NASA Lewis engineers assumed that 11 solar-powered, teleoperated LUNOX plants operating 35% of the time (this is, for 70% of each two-week lunar daylight period) could each strip-mine and refine 25,000 tons of orange soil to produce about 1000 tons of LUNOX per year. They estimated that the orange soil area near the Apollo 17 landing site might yield up to 700 million tons of LUNOX; that is, enough to support weekly 24-hour commuter flights for the next 60,000 years.

LANTR would see the basic all-LH2 BNTR engine augmented with a system for introducing LOX into the supersonic hot hydrogen exhaust flow "downstream" of the reactor. The LOX would enable the hydrogen to burn much as it does in a conventional LOX/LH2 chemical rocket engine, dramatically increasing LANTR thrust. This, Borowski and Dudzinski wrote, would offer "big engine" performance from "smaller, more affordable, easier to test NTR engines."

To trim development cost, the LANTR LTV would structurally closely resemble the all-LH2 LTV already described. At 7.5 meters long, the LANTR LTV's forward section would measure 1.5 meters shorter than its all-LH2 counterpart. The aft section, the core stage, would be outwardly identical to its all-LH2 predecessor. As with the all-LH2 LTV, a pair of Shuttle-Cs would launch the fore and aft sections of the LANTR LTV, which would then rendezvous and dock automatically in LEO.

The LANTR LTV would then dock automatically with a propellant depot in LEO. There it would fill its large tank with 45.5 tons of LH2 and its small tank with 112.3 tons of LOX, which is much denser than LH2. The propellant depot's LOX and LH2 would all be produced on Earth and boosted into LEO on Shuttle-derived launch vehicles.

Meanwhile, a Space Shuttle or a next-generation reusable piloted spacecraft would deliver to the International Space Station (ISS) 20 passengers bound for the LUNOX production base on the Moon. Accommodations on board the ISS are, of course, not spacious, so the new arrivals would immediately move into a 15-ton, 4.6-meter-diameter, eight-meter-long cylindrical Passenger Transport Module (PTM) docked with the station. Even in its most advanced form, Borowski and Dudzinski wrote, their Earth-Moon transportation system would be "spartan" compared with Heywood Floyd's Moon shuttle; it would, for example, not employ stewards.

The 20 Moon voyagers would remain inside the PTM throughout their 24-hour Earth-Moon journey, so would see little change in their immediate surroundings from the time they boarded it until they entered the lunar surface base. The PTM would, however, interface with three vehicles besides the ISS during each lunar flight.

As the time for LEO departure approached, the PTM would undock from the ISS and move away using its own chemical-propellant attitude-control thrusters. It would rendezvous with a LANTR LTV standing by near the LEO propellant depot at a "safe distance" from the ISS: that is, far enough away that radiation from its BNTR engines could neither harm the ISS crew nor reflect off ISS structure and harm the astronauts in the PTM. The PTM would approach and dock tail-first with the LANTR LTV, forming a 195.6-ton LANTR "commuter shuttle."

The commuter shuttle would climb away from LEO quickly (image at top of post). Acceleration to 24-hour Earth-Moon transfer velocity would need only 21.2 minutes, or less than half the duration of the all-LH2 LTV burn required to achieve an 84-hour Earth-Moon transfer. During the climb away from LEO, the 20 passengers would, much like Dr. Floyd in the book 2001, feel only a "mild" pressure — to be precise, just 0.23 Earth gravities of acceleration at BNTR start-up, when the commuter shuttle was fully loaded with propellants, and 0.46 gravities just before BNTR engine shutdown, when about half its propellants were expended.

Twenty-four hours after LEO departure, the BNTR engines would fire again to slow the commuter shuttle so that the Moon's gravity could capture it into lunar orbit. It would rendezvous with a lunar-orbit propellant depot containing LH2 brought from Earth and LUNOX.

The PTM would undock from the commuter shuttle and link up with a waiting lunar surface-based reusable LLV, the second vehicle with which it would interface during its trip to the Moon. The skeletal four-engine LLV would weigh 10.9 tons without propellants or cargo and 59.5 tons loaded with 33.6 tons of propellants and the 15-ton PTM.

In lunar orbital night: at the end of a 24-hour Earth-Moon crossing, the PTM (lower left) has separated from the LANTR LTV (lower right) near the Moon-orbiting propellant depot (barely visible above the LANTR LTV). A reusable LLV now moves into position to grapple the PTM and begin descent to the LUNOX production base on the Moon's surface. Image credit: Pat Rawlings/NASA.

The LLV would descend to the LUNOX base on four plumes of burning Earth hydrogen and LUNOX. After touchdown, a wheeled flatbed — the third vehicle with which the passenger module would interface — would move into position beneath the PTM and detach it from the overhead LLV framework. The PTM/flatbed combination would then roll over the lunar surface from the landing field to an airlock leading into a surface habitat. After linkup with the habitat, the 20 passengers would exit the PTM to begin their duties on the Moon.

In addition to moving passengers and cargo between Earth and Moon and back again, the LANTR architecture would, as already indicated, move LUNOX and Earth-produced LH2. Four times per week a reusable tanker module with an empty weight of five tons loaded with 25 tons of LUNOX would ride a flatbed to a waiting automated LLV and then ascend to the Moon-orbiting propellant depot. After pumping its LUNOX cargo into the propellant depot's tanks, it would return to the LUNOX base.

Welcome to the Moon: in the lower right corner, a PTM rides a six-wheeled flatbed to an airlock leading into a large inflatable lunar surface habitat. Meanwhile, at upper center-right, a tanker LLV lifts off on a mission to transport LUNOX to the lunar-orbital propellant depot. Image credit: Pat Rawlings/NASA. 

Borowski and Dudzinski assumed a fleet of four LANTR LTVs. Each would carry out 13 Earth-Moon round-trips per year, for a total of 52 commuter flights (that is, one per week). Each LANTR LTV would in its BNTR engines hold enough fissile material to permit 44 Earth-Moon round-trips, giving it an operational lifetime of 3.3 years.

A LANTR LTV near end-of-life would perform a one-way all-cargo mission before disposal into a Sun-centered orbit. One-way cargo would include Earth-produced LH2 for the propellant depot in lunar orbit. With about 23 tons of surplus LH2 in its "core stage" tank, a one-way LOX load of only 66 tons, and a potential cargo weight of about 80 tons, the LANTR LTV might deliver more than 100 tons of LH2 to lunar orbit during its final mission.

When Borowski and Dudzinski wrote their paper in 1997, existence of lunar polar ice in permanently shadowed craters, first predicted in 1961, remained uncertain. Data from a 1994 joint experiment using the Clementine lunar orbiter and NASA's Deep Space Network antennas had hinted strongly at the existence of hydrogen at the poles, but alternate explanations for the hydrogen signal existed, and an experiment employing the giant Arecibo radio telescope in Puerto Rico could find no trace of lunar hydrogen.

Robotic spacecraft in lunar polar orbit have since confirmed that a large quantity of water ice exists at the Moon's poles — in the billions of tons. Provided that mining equipment can be designed to operate in the very cold, very dark environment of the permanently shadowed craters, the existence of water ice means that both oxygen and hydrogen await us on the Moon in potentially easily processed form.

In theory, water ice-rich feedstock need only be heated to separate out the water, which would then be split into hydrogen and oxygen using electrolysis. Though this would seem to render Borowski and Dudzinski's LUNOX mining scenario irrelevant, their LANTR-based transportation system might burn LOX and LH2 derived from lunar polar ice as easily as it could Earth LH2 and LUNOX.

Early drafts of the 2001: A Space Odyssey screenplay — there were many — are replete with informative dialog. Though actors spoke some of the dialog during filming, most was replaced with classical music and sound effects in the final film.

In a late 1965/early 1966 draft of the script, the Aries-1B moon shuttle pilot and co-pilot speculate about the purpose of Heywood Floyd's unprecedented single-passenger lunar flight. The pilot remarks that the Moon shuttle will return to Earth orbit without passengers because Clavius Base is under quarantine. Only Floyd would be permitted to leave the Moon shuttle and no one at the base  would be permitted to board it.

The co-pilot points out that Moon shuttle tickets cost $10,000 one-way, so Floyd's mission will cost USAA and U.S. taxpayers about $600,000 — that is, the same as a round-trip flight with 30 passengers on board going each way. Alas, Borowski and Dudzinski provided no estimate of the cost of reaching the Moon using their proposed infrastructure.

In the book 2001, Floyd disembarks from the Aries-1B and stops for a glass of lunar sherry — made from Moon-grown algae — in the Clavius Base Administrator's office. He then attends a briefing in which he hears the latest news about the find that motivated his secretive single-passenger Moon flight. A black monolith found beneath the floor of Tycho crater has, he learns, nothing to do with the Chinese expedition of 1998. It was, geologists from Clavius Base have determined, deliberately buried three million years ago. It is the first evidence of intelligent life off the Earth.

After a moonbus ride across the rugged southern Lunar Highlands to Tycho, Floyd witnesses the beginning of a slow lunar dawn. He dons an advanced space suit — doing so takes only a few minutes, and it barely restricts his movements — then descends into the pit excavated around the monolith. Meanwhile, the Sun rises slowly over the lip of the excavation, shining its light on the monolith for the first time in three million years.

In the film 2001, Floyd joins other bureaucrats for a group photo in front of the monolith. Set against the brooding monolith, which seems to soak up all light, this very human ritual is so mundane as to be comical. As the photographer gestures repeatedly for them to move closer together — a critical part of the group-photo ritual — the monolith interrupts by emitting a powerful electronic scream.

Floyd and the others stumble around in pain and confusion as their suit radios receive the signal and blast it into their helmets. Only later do they realize that, by exposing the monolith to the Sun, they have tripped an ancient alarm.

Sources

"2001: A Space Odyssey" Revisited — The Feasibility of 24 Hour Commuter Flights to the Moon Using NTR Propulsion with LUNOX Afterburners," AIAA-97-2956, Stanley Borowski and Leonard Dudzinski; paper presented at the 33rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit in Seattle, Washington, 6-9 July 1997.

"2001: A Space Odyssey" Revisited — The Feasibility of 24 Hour Commuter Flights to the Moon Using NTR Propulsion with LUNOX Afterburners, NASA/TM-1998-208830/REV2, Stanley Borowski and Leonard Dudzinski, NASA Glenn Research Center, June 2003.

Kubrick, Stanley, and Arthur C. Clarke, 2001: A Space Odyssey, directed by Stanley Kubrick, Metro Goldwyn Mayer, April 1968.

2001: A Space Odyssey, Screenplay by Stanley Kubrick and Arthur C. Clarke, pp. b35-b36a, 12/1965.

2001: A Space Odyssey, Arthur C. Clarke, New York: New American Library, October 1999.

The Making of Stanley Kubrick's 2001: A Space Odyssey, Piers Bizony, Taschen, 2014, p. 58-59.

2001Italia.it: A Blog Devoted to 2001: A Space Odyssey (http://www.2001italia.it/ — accessed 12 June 2016).

More Information

Could the Space Voyages in the Film and Novel "2001: A Space Odyssey" Really Happen? (Part 2)

Could the Space Voyages in the Film and Novel "2001: A Space Odyssey" Really Happen? (Part 3)

The Last Days of the Nuclear Shuttle (1971)

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

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

Artist concept of Gilruth's 1968 "million-pound" artificial-gravity space station. Visible in this image are the habitat module (left), the hub with space-facing instruments on top and the hangar below, and, in the distance on the right, the S-II stage counterweight linked to the hub by a truss structure. Also visible are a small module maneuvering toward the hangar opening, a small piloted servicing vehicle approaching a free-flying 120-inch telescope, and a docked Gemini-derived crew rotation/logistics resupply vehicle. Image kindly provided by Carmine Rossi. Image credit: NASA.

Engineers often make the mistake of assuming that the course of spaceflight should be logical. Perhaps this is a quirk of the engineer personality (if such a thing exists). In any case, it is an unrealistic expectation. Human enterprise does not follow a logical path. History is about expediency and contingency, rarely do engineers see eye to eye, and, in any case, engineers do not comprise the majority of players in spaceflight decision-making.

In reading various proposals for NASA's post-Apollo future, one often has the sense that engineers wanted earnestly to take back the planning process and put the space agency on a logical track. They understood as well as most people the international and domestic political drivers behind Apollo, but viewed the Moon program as a step out of turn. They were proud of their Apollo accomplishments; as the lunar program's culmination approached, however, many seemed eager for the opportunity to leave the Moon alone in favor of a logical build-up of experience and capabilities back in low-Earth orbit.

At the cutting edge: Robert Gilruth in 1958. Image credit: NASA.

In few places is this as apparent as in Robert Gilruth's 25 June 1968 presentation to the Fourth International Symposium on Bioastronautics and the Exploration of Space. The Symposium took place in San Antonio, Texas, just a few hours' drive from the Houston-based NASA Manned Spacecraft Center (MSC), where Gilruth was director. Gilruth titled his presentation "Manned Space Stations: Gateway to Our Future in Space."

A native of Minnesota, Gilruth had gone to work at the Langley Memorial Aeronautical Laboratory in Hampton, Virginia, in 1937, directly out of graduate school. The National Advisory Committee for Aeronautics (NACA) had established Langley, its first research lab, in 1917, in part to ensure that the United States would not be left behind as the First World War drove aviation advancement in Europe.

Gilruth was no raging conservative when it came to technology. In the 1940s and 1950s he had worked at the cutting edge of high-speed aviation, where conventional aeronautics shaded into the arcane world of rockets and vehicles shaped to endure the pressures and temperatures of hypersonic speeds. He was instrumental in the creation of the rocketry range at Wallops Island, located across Chesapeake Bay from Langley near the tip of the Delmarva Peninsula. His talents were noticed early on; in 1952, before he turned 40, he became Langley's assistant director.

Gilruth's work took on new significance when the Soviet Union launched the first Sputnik satellite into Earth orbit on 4 October 1957. Though President Dwight Eisenhower downplayed the significance of the Sputniks, political pressure orchestrated in large part by Senate Majority Leader and Presidential aspirant Lyndon Baines Johnson forced his hand.

Within a year of Sputnik's launch, NACA became a part of the newly established NASA, Langley was renamed the NASA Langley Research Center (LaRC), and Gilruth became director of the Space Task Group (STG), an ad hoc organization within LaRC dedicated to human spaceflight. He remained director as the STG was elevated in 1962 to the status of a new NASA center, renamed the Manned Spacecraft Center, and transplanted to Vice President Johnson's home state of Texas.

The Symposium held six years later in San Antonio was a high-profile venue for putting across Gilruth's vision of the logical course of post-Apollo spaceflight. Arthur C. Clarke, screenwriter with Stanley Kubrick of the landmark film 2001: A Space Odyssey, was on hand to talk about exotic biology in the clouds of Jupiter. 2001 was released just three months before the Symposium. National Aeronautics and Space Council Executive Secretary Edward Welsh delivered the keynote address. In it, he called upon Congress to cease slashing NASA funding aimed at giving the agency a post-Apollo future.

Planning and building an Earth-orbiting space station would be challenging, Gilruth told his audience, in part because engineers had proposed so many different designs and justifications for space stations. In his presentation, he emphasized designs from MSC in-house and contractor studies. In fact, to prepare for his talk, Gilruth in April 1968 had tasked his engineers with designing a "million-pound station" based on 1966 MSC designs.

A 1966 NASA Manned Spacecraft Center station design with the same general layout as the 1968 "million-pound" design at the top of this post. At upper right is the habitat module. Telescoping arms link it to the zero-gravity hub, to which an Apollo Command and Service Module piloted spacecraft is docked. A spent Saturn V S-II second stage (left) serves as an artificial-gravity counterweight for the habitat. The solar-powered station would permanently point its solar arrays at the Sun as it orbited the Earth so that the spin axis would pass through the center of the cylindrical hub and through the long axis of the docked Apollo. Image credit: NASA.

Gilruth's 1968 station would need three Saturn V rocket launches to get started and two more to reach its full potential as a "location in space. . .developed to support men and equipment on a permanent basis. . .to take advantage of the economies of size, centralization, and permanency." He likened the space station to a base in Antarctica.

He declared that "development of the Saturn V. . .had provided one of the major building blocks for space station design." Gilruth then discussed how the Apollo Applications Program (AAP), NASA's only approved successor to Apollo, would compliment his station program. As its name implied, AAP would apply hardware developed for the Apollo Moon program, including the Saturn V rocket, to new missions on the Moon and in Earth orbit.

In early 1966, as AAP's NASA Headquarters office drew up a roster of more than 30 AAP Earth-orbital and lunar flights after minimal consultation with MSC and the other NASA centers, Gilruth had frank discussions with George Mueller, NASA Associate Administrator for Manned Space Flight, via letter, telephone, and telex. He argued that finding new uses for Apollo spacecraft and rockets was no basis for a post-Apollo space program. This ignored the fact that President Johnson had in 1965 called for a low-cost post-Apollo program based on Apollo technology.

NASA's piloted spaceflight organizations, Gilruth wrote, should aim instead for a "next big program" after Apollo. He mentioned the possibility of casting AAP as a precursor to a piloted Mars/Venus flyby, a class of piloted Apollo-derived mission under active investigation in 1964-1967. While engaged in discussions with Mueller, however, Gilruth initiated the 1966 in-house MSC station studies, thus revealing the form he believed the next big program should take.

In his San Antonio talk, Gilruth explained that AAP would explore the advantages of Earth-orbiting space stations "in a modest way." In particular, the AAP "wet launched" workshop, a modified Saturn IB S-IVB second stage, would enable NASA to study station habitability, biomedical effects of long spaceflights, and, through the addition of a separately launched solar observation module, the ability of humans to perform "a really complex scientific experiment" in Earth orbit.

Cutaway of the AAP Wet Workshop showing the Apollo Lunar Module-derived solar observatory (center left) attached to the docking adapter. The solar observatory would reach Earth orbit atop a Saturn IB rocket, the Saturn V's smaller cousin, which was intended as AAP's workhorse launcher. Image credit: NASA.

The AAP workshop would play the role for which it was intended — that of rocket stage — until it reached orbit. During ascent to orbit, a streamlined launch shroud on top of the stage would separate, revealing a docking module mounted atop the S-IVB stage liquid hydrogen fuel tank.

Ground controllers would command the orbiting stage to open vents in its liquid hydrogen and liquid oxygen tanks to enable residual propellants to escape. They would then close the vents and fill the hydrogen tank with a breathable air mixture from tanks in the docking module. Meanwhile, twin solar arrays would unfold from the workshop's sides. These would generate a total of about six kilowatts of electricity.

A three-man crew would then arrive in a Saturn IB-launched Apollo Command and Service Module (CSM) spacecraft. They would dock at the front of the docking adapter, enter it, and move furnishings stowed inside through a "manhole" hatch into the hydrogen tank. They would, for example, install a grid-work floor, fabric walls, and a galley module. After completing their orbital program, which might last weeks or months, the astronauts would return to Earth in the CSM. Subsequent crews would live on board the AAP workshop for successively longer periods.

Gilruth concluded his discussion of the AAP workshop by noting that it would "neglect what may be one of the major requirements for successful operation of a space station" — namely, artificial gravity. He believed that a practical space station would need to provide its inhabitants with "a high level of artificial gravity."

Artificial gravity would, he explained, enable comfortable movement, easy handling of fluids, and Earth-like "general man/machine interfaces." Because they could move more or less as they did on Earth, with their hands free to hold objects and to work, station crew members would need little special training to move about. Fluids would move as they did on Earth, which would make familiar the basics of personal hygiene, station cleaning, and food preparation. Equipment on the station could be identical to equipment on Earth, improving efficiency.

Artificial gravity would allow many types of researchers to live and work on the station, Gilruth told his San Antonio audience; basically, any who were eager to explore and exploit the economic and scientific benefits the space station would offer. "I, personally, look forward to the day when our space station crews will contain representatives from all the nations of the world," he added.

Gilruth described briefly an intermediate step between the zero-gravity AAP workshop and his large artificial-gravity station. He envisioned that a Saturn IB might launch an Apollo CSM. A drum-shaped multipurpose experiment module Boeing had designed on contract to MSC would ride in the streamlined adapter between the CSM engine bell and the top of the Saturn IB second stage.

Upon reaching orbit, the CSM would detach from the adapter, the four petal-like segments of which would fold back to expose the experiment module. The CSM crew would turn their spacecraft end for end and dock with the top of the experiment module, then would open latches linking the module to the rocket stage. Using the CSM's attitude-control thrusters, they would then pull the experiment module away from the stage.

Artificial-gravity experiment: the counterweight (upper right) is the S-IVB second stage of the Saturn IB rocket that boosted the CSM and experiment module into Earth orbit. Image credit: NASA

The module would, however, remain attached to the spent stage by an "extension mechanism," which might be as simple as a reel and cable. As the CSM/experiment module combination backed away from the stage, the crew would carefully fire the CSM's attitude-control thrusters, causing the CSM/experiment module/cable/stage assemblage to slowly spin end over end. The cable would draw taut and the crew would feel artificial gravity pressing them down into their couches. Separating from the module would end the experiment.

The 1966 MSC station study had looked at three classes of artificial-gravity space station, designated "Y," "O," and "I." The "Y" station would be approximately Y-shaped, with at least three arms. (The Project Olympus station — see the 1963 "Space Station Resupply. . ." link under "More Information" at the end of this post — is a good example of this station type.) The "O" station would take the form of a rotating wheel. The "I" station, which Gilruth favored and described in his San Antonio talk, would be a long cylindrical assemblage. He likened it to a "baton."

Assembling Gilruth's spinning baton (left to right): Saturn V launch 1 boosts the habitat module with its twin telescoping arms into Earth orbit. Saturn V launch 2 places the hub into orbit; the hub then docks with the habitat module. Saturn V launch 3 launches a deployable truss which turns the Saturn V S-II second stage into a counterweight. The station crew then fires rocket motors to spin the station end over end 3.5 times per minute to produce about one Earth gravity in the section of the habitat module farthest from the center of rotation. Image credit: NASA.

One million pounds, the mass Gilruth gave for his station, is equal to 500 tons. Probably this underestimates the likely mass of the station, which he hoped would house 50 people and 100,000 pounds (50 tons) of experiment equipment after its first three assembly launches.

The station would measure 240 feet from the center of rotation at its hub to the farthest part of the multi-deck, 50,000-cubic-foot habitat module and 375 feet from the center of rotation to the engine bells of the spent Saturn V S-II second stage that would serve as an artificial-gravity counterweight for the habitat. Total station length thus would come to about 615 feet.

These dimensions would enable the station to spin at 3.5 rotations per minute (rpm) without any ill effects for the crew, Gilruth explained. Spinning the station at 3.5 rpm would produce artificial gravity in the habitat module about equal to Earth's gravity. He noted that small-radius, fast-spinning systems could, based on Earth-surface studies of rotating rooms, cause crews to become ill and disoriented and produce other undesirable effects: water pouring from a faucet would, for example, curve. Setting his 500-ton baton twirling would require a one-time expenditure of 7000 pounds of propellants, Gilruth added.

The 45,000-cubic-foot drum-shaped hub would include electric motors that would cause it to rotate "backwards," canceling out the station's spin so that it would appear motionless. This would preserve zero-gravity conditions there. Gilruth envisioned that the hub would serve as a laboratory for exploring potential applications of zero gravity and as a hangar.

The hub hangar would receive self-propelled co-orbiting automated modules. Astronauts would service the modules in the hangar; they might collect and replace film, change out experiment equipment, and transfer propellants before releasing them to resume their zero-gravity work near the spinning station. Larger automated modules that could not fit within the hub hangar — for example, a 120-inch telescope — might be visited by astronauts, not returned to the station.

The station would operate in an orbit inclined 50° relative to the equator, enabling its Earth-pointing instruments, mounted on the lower sides of the hub, to survey a large fraction of Earth's lands and seas. Gilruth, an avid sailor, gave special attention to oceanographic observations in his San Antonio presentation. 

Space-pointing instruments would ride on top of the hub. Gilruth explained that many types of astronomical instruments would benefit from a position high above "Earth's dirty and shimmering atmosphere." 

Gilruth was not specific about the station's means of generating electricity, though he expected that it would need "20 or 50 or even 100 kilowatts" if it was to accomplish a wide range of experiments. The station's large size would permit mounting of proportionately large solar arrays; equally, it could enable use of "large nuclear systems" with extensive heat radiator panels, a large separation distance between the crew and the power source, and ample radiation shielding. 

Gilruth envisioned that, some time after the initial 50-person station was complete in Earth orbit, two more Saturn V launches would add another habitat module and a second S-II stage counterweight, bumping the station population up to at least 100. The large number of people would do away with the need for extensive cross-training in multiple skills and would enable specialization impossible in small crews. It would also reduce the amount of time any one station resident would spend performing maintenance and housekeeping chores, thus increasing time available for productive work.

Interestingly, Gilruth barely mentioned the need for a vehicle for transporting supplies and crews to and from his station, let alone any specific vehicle design. He mentioned "flexible crew rotation patterns," but did not explain how they would be accomplished. He did, however, note that the station could serve as a "logistic center" — a kind of warehouse — which would enable "efficient launch schedules for operational and experiment support supplies." He argued that the station's permanency would enable reuse and modification of equipment, reducing the quantity that would need to be shipped up from Earth.

The illustration of Gilruth's million-pound station at the top of this post — sent my way by reader Carmine Rossi — helps to clear up some of the mystery. Visible on either side of the hub are twin "Big Gemini" crew/cargo vehicles. These would have "backed up" to dock with ports on the sides of the non-spinning hub.

Proposed by contractor McDonnell Douglas in 1967, Big Gemini represented a continuation of Gemini contractor McDonnell's efforts to sell NASA and the U.S. Air Force Gemini-derived spacecraft and modular space stations. McDonnell had begun to pitch a broad range of Gemini variants as early as 1962, the year Gemini became the "bridge" program linking Mercury and Apollo.

Each Big Gemini might have launched nine astronauts (12 in its advanced version) and several tons of supplies. The design would have been familiar to many in his audience, so perhaps Gilruth felt no need to call it out specifically in his presentation.

Even in its advanced form, however, Big Gemini was a small crew/cargo spacecraft for a big space station. The concept, spelled out in a detailed eight-volume report submitted to MSC in August 1969, fueled awareness that large stations such as MSC's 1968 design would need sophisticated crew/cargo vehicles. This bolstered plans for reusable winged "Space Shuttle" vehicles.

Gilruth ended his presentation by declaring that a large space station would provide "tens of thousands of hours of operational experience. . .in the space environment." This would, he said, make it "a true gateway into the exciting space programs of the more distant future."

Sources

Letter, Robert Gilruth to George Mueller, 25 March 1966.

Letter, Robert Gilruth to George Mueller, 15 April 1966.

Preliminary Technical Data for Earth Orbiting Space Station, Volume 1, Summary Report, MSC-EA-R-66-1, NASA MSC, 7 November 1966.

Status Report: Earth Orbiting Space Station Artificial Gravity Experiment, MSC Internal Note 68-ET-1, NASA MSC, January 1968.

Manned Space Stations: Gateway to Our Future in Space, Robert Gilruth; presentation to the Fourth International Symposium on Bioastronautics and the Exploration of Space in San Antonio, Texas, 25 June 1968.

Astronautics and Aeronautics, 1968: Chronology on Science, Technology, and Policy, NASA, 1969, pp. 141-142.

A Summary of NASA Manned Spacecraft Center Advanced Earth Orbital Missions Space Station Activity from 1962 to 1969, Maxime Faget and Edward Olling, NASA MSC, February 1969, pp. 17-18, 27-28.

Skylab: A Chronology, NASA SP-4011, R. Newkirk, I. Ertel, and C. Brooks, NASA, 1977, pp. 172-174.

NASA Press Release, "Dr. Robert Gilruth, An Architect of Manned Space Flight, Dies," Bob Jacobs, NASA Headquarters, 17 August 2000.

More Information

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

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

McDonnell Douglas Phase B Space Station (1970)

A Forgotten Rocket - The Saturn IB

Chronology: Apollo-Shuttle Transition 1.0

Image credit: NASA.

Blogging history can be awkward — at least the way I do it. I tend to blog about whatever catches my interest as I sift through my files or locate new documents. The result is nothing like chronological, and chronology — the order in which things happened — is obviously essential for understanding history.

Because of this, I've decided to occasionally compile posts on a theme — posts that tell parts of one story — as a "chronological presentation." The posts listed below all can stand alone, but when placed together in chronological order they tell a more comprehensive story. As future posts fill in more gaps, the story will become more complete. Eventually, I'll post a 2.0 version of the link list below (and perhaps a 3.0 version after that).

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

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

McDonnell Douglas Phase B Space Station (June 1970)

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

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

The Last Days of the Nuclear Shuttle (February 1971)

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

Where to Launch and Land the Space Shuttle? (April 1972)

The Last Days of the Nuclear Shuttle (1971)

Image credit: NASA.

In July 1969, as the Apollo 11 moon landing brought the Apollo Program to its culmination, Lockheed Missiles and Space Company (LMSC), McDonnell Douglas Astronautics Company (MDAC), and North American Rockwell (NAR) began the Nuclear Flight Systems Definition (NFSD) study on contract to NASA’s Marshall Space Flight Center (MSFC) in Huntsville, Alabama. The NFSD study occurred against a backdrop of great change in the U.S. civilian space program, and its evolution through three phases reflected this.

Cutaway of a typical NERVA nuclear-thermal rocket engine. The explanation of its operation that follows is simplified. Turbopumps push liquid hydrogen propellant from a large insulated propellant tank (not shown) through the reactor core. A reflector focuses neutrons radiated from uranium fuel rods back into the core, causing nuclear fission to occur. Liquid hydrogen picks up heat generated by the fission reaction in the core, helping to prevent the fuel rods from melting. The hot hydrogen then expands outward from the nozzle skirt extension, producing thrust. Liquid hydrogen also cools the nozzle. During engine shutdown, a control drum blocks the reflector, damping nuclear fission in the core. Propellant flow is maintained for a "cool-down" period after fission is halted to prevent fuel rods melting. Note the external and internal radiation shields which reduce crew radiation exposure. Image credit: NASA.

In Phase I of the NFSD study, MSFC charged LMSC, MDAC, and NAR with producing a "detailed analysis [and] conceptual design" of an expendable nuclear-thermal rocket stage equipped with a 200,000-pound-thrust NERVA II engine. The NERVA II was expected to be flight-ready in late 1977. The contractors were directed to study "development requirements of a nuclear propulsion system, including its evolution from a flight test stage to an operational. . .stage."

The Phase I nuclear stage was envisioned as a NERVA II with a single 33-foot-diameter propellant tank sized for launch from Earth atop a two-stage, 33-foot-diameter Saturn V rocket. Its main purpose would be to push piloted spacecraft out of low-Earth orbit (LEO) toward Mars.

Phase II commenced in October 1969, immediately after President Richard Nixon's Space Task Group (STG) endorsed (with reservations) NASA's aggressive Integrated Program Plan (IPP) for future U.S. spaceflight. The IPP was the brainchild of George Mueller's NASA Headquarters Office of Manned Space Flight, which supervised NASA's manned spaceflight centers, including MSFC.

In NFSD Phase II, MSFC directed its contractors to design a reusable nuclear rocket stage equipped with a 75,000-pound-thrust NERVA I engine. The stage, dubbed the Reusable Nuclear Shuttle (RNS), was intended mainly for roundtrip crew and cargo flights between space stations in LEO and lunar orbit. In January 1970, MSFC presented the contractors with an ambitious RNS traffic model calling for 157 Earth-moon flights between 1980 and 1990 by a fleet of 15 RNS vehicles, each toting 50 tons of cargo. Piloted Mars missions, though still considered a part of the IPP, were in NFSD Phase II relegated to secondary importance.

Image credit: NASA.

As in Phase I, the Phase II nuclear stage would reach Earth orbit on top of a Saturn V rocket. Its liquid hydrogen propellant would, on the other hand, climb into orbit in the payload bay of the proposed reusable winged Earth-to-Orbit Shuttle (EOS). NASA envisioned that more than 40% of EOS flights would be devoted to delivery of propellants. The EOS would pump liquid hydrogen/liquid oxygen propellants it carried directly into the tanks of chemical-propulsion Space Tugs. Most propellant carried in the EOS would, however, be liquid hydrogen meant for RNS propulsion. MSFC engineers envisioned that the EOS would cache RNS liquid hydrogen in LEO at an Orbital Propulsion Depot.

Electricity from twin nuclear reactors arranged in a "Y" configuration (right) powers refrigeration systems that keep liquid hydrogen stored in the Orbital Propellant Depot from turning to gas and escaping. Image credit: NASA.

A Reusable Nuclear Shuttle tanks up at the Orbital Propellant Depot using a soft-docking Refueling Adapter. Image credit: NASA.

That same month, NASA Administrator Thomas Paine permanently terminated Saturn V production and canceled Apollo 20 so that its Saturn V could launch the Apollo Applications Program (AAP) Dry Workshop (DWS). In February 1970, NASA gave the AAP DWS the new name Skylab and redesignated AAP as the Skylab Program.

Soon after, MSFC directed LMSC to examine launching the RNS inside the Space Shuttle payload bay, which was expected to measure 15 feet wide by 60 feet long. LMSC's Shuttle-launched "modular" RNS would comprise a NERVA I engine and multiple hydrogen tanks launched separately into LEO and joined together through a labyrinth of pipes. NAR continued work on a single-tank RNS sized for launch on a future heavy-lift rocket, while MDAC divided its study efforts between the two launch options.

Phase II segued into Phase III in May 1970, when MSFC directed the NFSD contractors to assume a 1978 or 1979 NERVA I flight readiness date. The postponement reflected an anticipated Fiscal Year 1971 NERVA funding cut. MSFC also directed the contractors to limit to 150 tons the amount of liquid hydrogen propellant each RNS would carry.

In February 1971, with the NFSD study set to conclude in less than two months, D. J. Osias, an analyst with NASA Headquarters planning contractor Bellcomm, summarized and critiqued reports prepared by the three contractors. He began by examining the ways that the contractors had approached the problem of radiation shielding. "Nuclear propulsion," he wrote, "complicates in-space operations by introducing a radioactive environment."

All the RNS designs included a 3000-pound radiation shield on top of the NERVA I to create a conical radiation "shadow" for crew protection, but also relied on the vehicle's propellants and structure for supplemental shielding. Osias asserted that "in regard to radiation shielding. . .the most optimistic results are being accepted and attention to the problem is diminishing."

He also noted that, as liquid hydrogen was expended as propellant, it would cease to be available to serve as radiation shielding. As the RNS tank or tanks emptied, crew radiation dose would thus steadily increase. To solve this problem, NAR had developed a "stand-pipe" single-tank RNS concept, in which a cylindrical "central column" running the length of the main tank stood between the crew and the NERVA I engine. The central column would remain filled with hydrogen until the surrounding main tank was emptied. MDAC, for its part, had developed a "hybrid" RNS shielding design that included a small hydrogen tank between the bottom of the main tank and the top of the NERVA I engine.

 Image credit: NASA.

The proper way to load cargo onto a Nuclear Shuttle: I = Use Space Tug robot arms to remove cargo module from Space Shuttle payload bay; II = stack cargo module on Space Tug; III = ignite Space Tug chemical rocket motors to rendezvous with Nuclear Shuttle, taking care to approach within the conical shadow created by the NERVA engine's radiation shields; IV = transfer cargo to Nuclear Shuttle. Image credit: NASA.

Crew transfer from the Earth-to-Orbit Shuttle to the Nuclear Shuttle might take place at the Orbital Propellant Depot. In this image, the crew of the Earth-to-Orbit Shuttle takes care to remain within the shadow of the NERVA engine's radiation shields. Image credit: NASA.

Osias postulated a maximum allowable radiation dose for an astronaut from sources other than cosmic rays of between 10 and 25 Roentgen Equivalent Man (REM) per year. Astronauts riding an RNS would, however, receive 10 REM each time its NERVA I engine operated. An astronaut 10 miles behind or to the side of an RNS operating at full power would receive a radiation dose of between 25 and 30 REM per hour. Osias noted that the NFSD contractors had recommended that no piloted spacecraft approach to within 100 miles of an operating NERVA I engine.

Radiation would create other operational problems, Osias wrote. Spacecraft could dock with an RNS by approaching through the cone-shaped radiation shadow that protected its crew. Docking an RNS to a large vehicle that protruded beyond the shadow — for example, a space station or a liquid hydrogen propellant depot — would, however, generate obvious problems. The large vehicle's crew might be exposed to radiation from the NERVA I; more insidious, the large vehicle's structure would reflect radiation back at the RNS, endangering its crew.

The NERVA I engine would emit radiation not only while it was in operation; it would also generate spent nuclear fuel that would emit harmful levels of radiation for decades or centuries. Osias noted that NAR had "repeatedly emphasized [that] maintainability is essential to economic operation of the RNS." A spacewalking repairman who approached to within 400 feet of the side of an RNS 10 days after its tenth (and, going by MSFC's traffic model, final) Earth-moon round-trip would, however, receive one REM per hour from the spent fuel it contained. Maintenance robots might replace the servicing capabilities of astronauts, Osias noted, but such systems would need costly development before they could become available.

Osias also reported that the "NFSD contractors. . .devoted little effort to [studying] emergency operations and malfunctions," adding that "[n]uclear systems, more than chemical propulsion vehicles, have the ability to involve the general population of the [E]arth in a space accident." A NERVA I explosion in LEO, for example, could lead to "random reentry of large pieces of radioactive material" that would probably survive reentry heating and strike Earth's surface. He urged that prevention of "return of the NERVA engine to the [E]arth's surface. . .be a basic rule of nuclear propulsion planning."

In NFSD study Phase II, LMSC estimated that, after just one Earth-moon round-trip, enough spent fuel would have accumulated within a NERVA I engine that it would need to remain in a safe high-altitude disposal orbit for 135 years. By the end of its operational life — after ten Earth-Moon flights — the "most desirable method of disposing of an engine" would, Osias wrote, be to "send the RNS on an unmanned, one-way mission to deep space."

The same month Osias completed his critique of the PFSD contractor studies, veteran New Mexico Senator Clinton Anderson, a close friend of former President Lyndon B. Johnson and a long-time nuclear rocket supporter, called a hearing to highlight the Nixon Administration's plan to slash NERVA funding from $110 million in Fiscal Year 1972 to only $30 million. At the hearing, Acting NASA Administrator Robert Seamans, an STG member, explained that Space Shuttle development had priority over NERVA development because the Space Shuttle was the essential transportation element that would launch into space all other IPP elements, including the RNS. He told Anderson that "NERVA needs the Shuttle, but the Shuttle does not need NERVA."

Six months after the NFSD contractors completed their reports, the Nixon White House unveiled its Fiscal Year 1973 budget request. As many had feared, it contained no funding for continued NERVA development. Anderson was ill and no longer able to adequately defend NERVA. A group of more than 30 pro-NERVA congressmen sought to sway the Nixon Administration, but to no effect. The final NERVA ground tests occurred in June and July 1972, after which the program was terminated, ending nearly 20 years of U.S. nuclear propulsion development.

Sources

"Status of Nuclear Flight System Definition Studies — Case 237," B71 02018 (NASA Contractor Report 116601), D. J. Osias, Bellcomm, Inc., 9 February 1971.

Humans to Mars: Fifty Years of Mission Planning, 1950-2000, Monographs in Aerospace History #21, NASA SP-2001-4521, David S. F. Portree, NASA, February 2001.

More Information

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

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

Apollo's End: NASA Cancels Apollo 15 & Apollo 19 to Save Station/Shuttle (1969)

Humans on Mars in 1995! (1980-1981)