18 July 2016

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 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 is a train of linked propellant modules, each about 20 feet long. From a certain 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 moon 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 really high Isps, the heaviest gas-core 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 engine, uranium would take the form of an incandescent ball of plasma in which nuclear fission would take place. The uranium fuel element (the plasma ball) 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 it should be.

Ragsdale's group emphasized open-cycle gas-core propulsion over closed-cycle gas-core 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, an omission 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 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 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 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 propellant 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 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 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 cut in half the quantity of hydrogen propellant the gas-core Mars spacecraft would expend during its round-trip journey.

NASA LeRC researchers envisioned 80-day gas-core "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 concepts, NASA LeRC gas-core propulsion never got the conceptual artwork it deserved - until now. This illustration, kindly provided by artist William Black/http://william-black.deviantart.com/, 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 early in its Earth-departure burn. 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 the dragonfly 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/http://william-black.deviantart.com/. The large disc at left is a shadow shield for protecting the spacecraft crew from radiation from 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. In Black's interpretation, hydrogen gas from the turbopumps then vents aft into space through a pair of pipes. He also includes a gimbal system for pivoting the engine off its center line and an uncooled rocket nozzle extension (colored black).
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 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 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 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 uranium 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.

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)

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

18 comments:

  1. Fabulous! You've provided a great treatise on the nuclear engine. Looking forward to Part III!

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    1. I'm working on it now. It will be more similar to part one - that it, it will summarize the film and book 2001 where part one left off.

      No ETA yet, but no vacation planned, so should be a shorter gap between part one and part two.

      dsfp

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    2. I mean, there should be a shorter gap between part two and part three. Oops!

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  2. I think about during the same time period what was spent on munitions while these research budgets were being cut and shake my head. Amazing technology potential to be developed here. But ironic as the theme in much of science fiction is that our ability to invent technology outpaces our wisdom in how to constructively use it.

    Thank you David for your well detailed research and time to assemble this post. Very intriguing.

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    1. You're welcome. Exotic propulsion is not a strong area for me, so I've had to do a lot of research. I think this is because I've focused on technologies that have gotten further along before they got the ax - space stations, for example (in that case we actually built some, though none as functional as once proposed).

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  3. There is an error for the unit conversion from Kelvin to Celsius: 22,000 K is 21,700° C and not only 12,200° C. Kelvin and Celsius values are nearly at the same at that level. And further more that's four times of the solar surface, not just twice.

    Nevertheless a great article about studies I haven't heard about before. But that sounds to me more like Science Fiction. An Isp of 3000-5000 seconds is today more realistic by using a VASIMR thruster, but the source for the electric power would also require a nuclear power plant.

    So nuclear power is the only source for power we know today for deep space exploration. And Voyager, Cassini, New Horizons, and more would not have happened without RTGs.

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    1. You have to understand that while the VASIMR has an Isp of 3,000 to 30,000 sec (depending upon the setting) but with a pathetic thrust of 400 to 40 newtons. You can see this because its thrust power is only about 6 megawatts.

      The open-cycle gas core nuclear thermal rocket has an Isp of around 4,000 sec but with a thrust of about 5,000,000 newtons. This is because it is using a barely contained nuclear reaction with a thrust power of about 10,0000 megawatts. Yes, it is a bit over the top.
      http://www.projectrho.com/public_html/rocket/enginelist.php#id--Nuclear_Thermal--Gas_Core--Open_Cycle--Open_Cycle

      VASIMR's drawback is nuclear reactors have a lot of mass, which drops the spacecraft acceleration. If the thrust is lower than about 5 milligee it can take the spacecraft years just to change orbit.

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    2. sorry, replace 10,0000 megawatts with 100,000 megawatts. That is 100 gigawatts or 0.1 terawatts.

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  4. Thank you for catching those errors - I'll fix them immediately.

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  5. Fixed. VASIMR would require some really hefty nuclear reactors and cooling systems, so has its share of technical issues, just like any advanced propulsion system. A big problem is, how do you test it at full scale? In any case, this post is not intended to advocate gas-core nuclear propulsion. This is a history blog, and this particular post looks at a film in the context of NASA research conducted in the 1960s and early 1970s.

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  6. I would like to see you work with Stan Borowski to see what Discover would look like if it had used Nuclear Thermal engines. Not as good as gas core--I know--but we do have SLS.
    http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140009579.pdf

    The idea of an oxygen afterburner interests me.

    I'm thinking the number of SLS payload segments for Discovery using NTR will about match the blocky vertebrae. 7-11 or so.

    Expensive--but if we had a radio signal near Io--we'd spend the money.

    Also--I like the idea of empty tankage being used as PROFACs http://www.bisbos.com/space_n_profac.html

    I don't think Gas core will work for that.

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  7. I love the way you keep updating the article. You mentioned 2 Discoveries. We have a 3rd:

    In the Book 2010, Overvoltages induced my spaceweather caused emergency-shut-downs of the nuclear reactors after Doctor David Bowman left the Discovery. Discovery ran on batteries for months until they were depleted. Normally, either the HAL 9000 or the crew would reactivate the nuclear reactors, but the HAL 9000 operated in a much reduced state and no crew was above the Discovery.

    In 2010, the 3 Americans, who were not allowed to take help from the Soviets, had to resurrect the totally dead Spacecraft and its computer, which might have recorded data in its reduced state about the Monolith for years before the power failed years ago, but the ship was totally dead. This was a big point in the book.

    Sir Arthur Charles Clarke, CBE, FRAS had a problem:

    Without cooling, the H2 would boil-off. He had to rethink his propulsion-system. He decided to keep nuclear propulsion, but decided to change the propellant. It had to be hydrogen-rich with the nonhydrogen component light. This leaves 4 choices:

    * Methane
    * Ammonia
    * Water
    * Hydrogen Fluoride.

    We need not bother considering Hydrogen Fluoride. That leaves Methane, Ammonia, and Water. The more hydrogen, the better, which points to methane, but the methane would have boiled off without refrigeration. That leaves ammonia and water. Water does not have much hydrogen in it and would freeze. That left ammonia:

    The book explains the choice as of using ammonia because, under pressure, ammonia can remain liquid from Earth-Orbit to Jupiter-Orbit without heating or refrigeration. Sir Arthur Charles Clarke, CBE, FRAS explained the changes such as the book 2001 taking place at Saturn and 2010 taking place at Jupiter because the books took place in parallel universes, in the forwards of 2010, 2061, and 3001.

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    1. Forgot to mention - I often post and then tweak. This time around is kind of extreme - major changes in structure, new info, new pictures. . . But that's OK, I think, if it yields a better post.

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    2. My replies to your comment, Walabio, of which there are now three, are out of order. Sorry about that.

      Occurs to me that one could say there's yet another DISCOVERY - as I suspect you know, Kubrick for a while wanted a Project Orion-type "bang-bang" propulsion system. His model-building department rebelled and Clarke wasn't too enamored of the change, either. Yet the might-have-been design is well enough known, I think, to rate as a fourth DISCOVERY, if we're basing our count mainly on propulsion systems.

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    3. I forgot about the Orion-Drive from the Lost Worlds of 2001. Oh well, it never made it into the Canon of the Movies and Books. Much changed during development:

      The sentient robot Athena became the sapient supercomputer HAL 9000.

      In the late 1950s, and early 1960s, so many wanted the high impulse, high thrust of nuclear propulsion. We soon had too abandon the nuclear option for safety (we could use ORION_propulsion for crewed interstellar missions. Now, we use the low-thrust high-impulse of ion-drives:

      Some believe that we should use Xenon, but I believe that NaK with a little Cæsium for increasing the liquid-range is worth investigating as a propellant. Back in the early 1960s, they would laugh at ion-drives:

      > "¡Baa¡ ¡Humbug! If it does not generate over a meganewton of thrust, it is not worth considering!"

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  8. Oh, drat - I plan to discuss this in my third post, along with things like the "carousel" designs. My current plan is to report what happened to DISCOVERY after Bowman left her instead of reporting what happened to Bowman. Stargate technology is not something I feel equipped to tackle. :-) I contend that it's accurate to state that there are two DISCOVERYs in 2001 - 2010 is not 2001.

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  9. I'm dragging on comments way longer than I should, but if I had to contract building nuclear space cycler similar to Buzz Alrin's Mars cycler, what nuclear propulsion would be the most feasible and attainable (mass of liftoff, size to build, etc) for a deployment in 10 years?

    Would this not be the next step from the ISS - long term habitability beyond Earth orbit, targetable for trips to Mars, Venus, and other locations for human flyby? I think 4-8 astronauts, flying around the inner solar system, demonstrating propulsion and habitability (gravity centrifuge hopefully) technology.

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    1. I've suggested something along these lines in the past, though not as the next step after ISS. I like to imagine a variable-gravity station in Earth orbit for that. Then I'd take the variable-G station design and send it out of Earth orbit as a revolving cycler - a space station orbiting the Sun. I imagine using solar-electric propulsion during these space program phases. I do not claim that these are the "best" next steps, but I like them - they make sense to me.

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