NASA’s Manned Mission to Venus

In the mid-1960s, NASA was already looking ahead to what it would do after the Apollo program. Where could the organization send astronauts after the moon that would make use of everything it had learned getting them to our satellite? What emerged was the Apollo Applications Program (AAP), a program designed to give the technologies generated from Apollo direction towards long term objectives in space. AAP goals were varied. They ranged from Earth orbital research, an extended and more permanent lunar exploration program, and manned planetary missions. Within this latter category, Mars was on the table but wasn’t the only target. In 1967, NASA looked at what it would take to send men to Venus (pictured).

Earth’s Twin

Historically, Venus has been an enigma in the sky. Nearly every culture has named it for its own goddess of love, but modern Earth-based observations revealed that our same-sized neighbour is a hot, carbon dioxide rich world. In 1962, NASA launched history’s first interplanetary mission, Mariner 2, to investigate our cosmic twin.

The small spacecraft gathered data about interplanetary space and solar activity on its way to Venus before taking direct measurements and observations of the planet during its 45-minute flyby. NASA lost contact with the spacecraft in 1963 after it swung into a wide heliocentric orbit. (Right, an artist’s concept of Mariner 2.)

The mission report on Mariner 2 was published in 1965. Among the preliminary results, NASA learned that Venus lacks a strong magnetic field, its extreme heat is generated in its lower atmosphere or surface, and the radiation levels between Earth and Venus are no more dangerous than the radiation anywhere else outside Earth’s protective magnetic field. NASA also learned that Venus had more secrets locked away under its thick clouds. It was worth going back.

The “Manned Venus Flyby” proposal was published on February 1, 1967. It was prepared for NASA by Bellcomm Inc., a division of AT&T established in 1963 to assist the nation’s space agency in its research, development, and overall documentation of systems integration within spacecraft.

When the report was published, NASA had just lost the Apollo 1 crew in a pre-launch fire, it had never flown any Apollo hardware with a crew, a crew had never flown outside Earth orbit, and the longest any astronaut had spent in microgravity environment was two weeks. So in determining the feasibility of a manned mission to Venus, Bellcomm was limited to preliminary reports about, and the expected performance levels of, Apollo hardware.

But flying to Venus was thought to be no harder than a mission to the moon, and NASA was theoretically able to do that. This would just be a longer mission and travel a little closer to the Sun. (Left, Venus as seen by Mariner 10 in 1973. The colours have been enhanced to simulate Venus’ natural colour as the human eye would see it.)

The Mission Profile

The crew would launch on a Saturn V during a month-long window beginning on October 31 and ending on November 30, 1973. This window offered the best geometry for a quick transit to Venus and the year was chosen because it was expected to be one with minimal solar activity — a good thing to take advantage of since the crew would be going towards the sun. At their closest, the crew would be only 0.7 AU from the Sun. (1 AU is the distance from the Earth to the Sun, about 93 million miles or 150 million kilometres. 0.7 AU is about 65.1 million miles or 105 million kilometres.)

After a brief stay in Earth orbit, the crew would fire their SIV-B stage (the upper stage of the Saturn V) and begin their transit to Venus. The outbound leg of the trip would last 123 days, making the crew’s arrival at Venus some time around March 3, 1974. Like Mariner 2, they would flyby rather than go into orbit, giving them only a brief time for up close observations and experiments. After their brief encounter with the planet, the spacecraft would sling around and begin its 273 day trip back to Earth. The crew would arrive and splash down, just like they would on Apollo, around December 1, 1974. Including the month-long launch window, the mission was planned for 400 days. (Right, the crescent moon and tiny crescent Venus.)

The first stages of the mission – from launch to the burn that would send the crew to Venus – the flight profile would be exactly the same as what NASA was planning to follow for Apollo. Likewise, when it returned to Earth, its reentry and splashdown would be the same as the methods in place for Apollo. Otherwise, the mission took on a very different shape.

The Spacecraft

The spacecraft was a tripartite design based on the Apollo hardware with additional components to support the longer mission. The Apollo Command and Service Module (CSM – a block II model) would be reused on this mission, an Environmental Support Unit (ESM) would replace the Lunar Module (LM), and a spent Saturn S-IVB (pronounced S four-B) stage would add a third section. (A schematic diagram showing the structure of the spacecraft from the outside. On the left is the Apollo configuration. Moving the the right are possible upgrades of the Venus configuration. From the Bellcomm report.)

The CSM would reprise its role as the main spacecraft. The crew would launch and splash down in the familiar gumdrop-shaped vehicle. The principle difference between the lunar and Venusian model was the addition of 430 pounds of ablative material in the heat shield for the latter. Coming in from interplanetary space, the astronauts would be traveling much faster and could expect a much more fiery reentry.

Like on Apollo, the CSM’s computer would be the primary supplier of guidance information as well as navigation and reaction control through the mission. It was, for the engineers, a simple matter of changing to programming for a Venus flyby trajectory. The on board computer would remain the same. The CSM would also provide the primary communications link between each module of the spacecraft as well as between the crew and mission control for the duration of the mission. From Earth, NASA would track the spacecraft with by ground based radio signal tracking system. This was what NASA had used for the Mercury and Gemini missions, and it was the most reliable method available. (As seen from the LM, Dave Scott stand in the Command Module on Apollo 9. This is the spacecraft the astronauts would take to Venus.)

Most importantly, the CSM would be a ready lifeboat for the crew should anything happen – one incredibly important redundancy measure that was introduced into the mission. The CSM was powered entirely from batteries. During a nominal mission, the batteries would provide power to the spacecraft during reentry. They were also large enough to support the crew in the event of an emergency abort. If anything happened and the crew had to abort once they were en route to Venus, the CSM could bring them home. With the batteries full, the crew would live off the emergency rations on board for the 60 day abort trajectory that would bring them back to Earth. In addition to emergency rations, and also like NASA was planning on for Apollo, the CSM was stocked with survival rations for three men for a week. There was always a chance they would miss their splashdown point and land in a jungle.

The Environmental Support Module (ESM) was a larger module designed to dock with the CSM where it would dock with the LM on Apollo missions. Once in orbit, the crew would turn the CSM around, capture the ESM and pull it from its launch casing. The ESM was designed to supply long-duration life support and environmental control throughout the mission. It was also the main experimental bay.

With the CSM and ESM docked, the S-IVB stage would propel the crew towards Venus. Empty, the crew would keep the spent rocket stage attached and repurpose it into the third portion of the spacecraft – everything they would need to turn the SIV-B into a livable space stored in the ESM. The newly habitable module would become their primary living and recreational space. Outside this largest module would be an array of solar cells that would power the bulk of the mission and keep the CSM’s batteries charged. (A schematic of the repurposed and habitable SIV-B stage. From the Bellcomm report.)

Each piece of the spacecraft was reinforced to protect the crew from micrometeoroids or larger meteoroids. But neither were considered a likely hazard to the mission. Instead, possible solar flares were a main concern. To protect the crew, the ESM was reinforced with a radiation shield. This piece of the spacecraft would provide the astronauts with a shelter during a solar storm.

The Science

A manned mission to Venus couldn’t just be about NASA proving it was technically feasible. There had to be some scientific component to make it worthwhile. As such, much of the mission would be dedicated to running and monitoring experiments. High on the list was gathering data on Venus’ surface properties, the chemical composition of the lower levels of the atmosphere, its gravitational field, and the properties of its various layers of clouds. Experiments designed to reveal aspects of our solar system were also on the agenda. (This radar image fro the Magellan spacecraft shows the surface of Venus. 1994.)

The primary instrument on board the Venus mission would be a telescope. Mounted in the ESM, it could gather UV, X-ray, and infrared measurements. This would be used to measure Venus, as well as other objects in our solar system and beyond. Detailed measurements of Venus’s atmosphere and clouds, nearly impenetrable by telescope, would be done by robotic probes. The crew would release probes as they neared the planet and gather real-time measurements as they fell through the atmosphere. At least in this early planning stage, no probes were designed to land on Venus’ surface. (A Venusian landing couldn’t be achieved until the Soviet Union sent Venera 9to the planet in 1975.)

The surface of Venus as captured by the Venera 9 lander. 1975.

Because the CSM could only hold so much material coming back to Earth, communications from the spacecraft were designed to facilitate data transfers as well.  All the data the astronauts gathered would be sent to mission control as experiments were completed. This would limit the crew’s returned payload to film and cameras, and also give scientists a chance to be involved in the mission’s science as it happened. They could direct different observations and measurements based on what the astronauts had already found.

Living in Space for 400 Days

The 400-day mission would push the crew and the spacecraft to its limits. Onboard recycling systems would help the crew and mission planners make the most of what they had at their disposal and decrease launch weight. An onboard filtration system woudl provide the crew with clean water.  The mission would launch with 500 pounds of water. 100 pounds would be stored in the ESM and recycled throughout the mission while the other 400 pounds would be stored in the CSM to be used only in an emergency.

The environment, too, would be maintained by recycling the air. Lithium hydroxide canisters were set to be use on Apollo to remove carbon dioxide fro the air, but these filters saturate quickly and can’t be reused. They are a heavy and bulky choice. They would be retained as an emergency measure, but the duration of the mission would use a molecular sieve. It would absorb and filter the exhaled air and return breathable oxygen into the cabin. (Edward Gibson stands at an Apollo Telescope Mount on Skylab 4, 1974. Astronauts en route to Venus might have had a similar arrangement.)

Instead of a pure oxygen environment as NASA had used on Mercury, Gemini, and was planning to use on Apollo, the Venus mission would give the crew a two-gas environment 70 percent oxygen and 30 percent nitrogen. At this point, no one was completely sure how men would react physiologically to 400 days in a pure oxygen environment. This safety measure came at a cost. It was a less reliable system than a pure oxygen environment with a single filtration system, but the benefit to the astronauts outweighed the possibility of complications.

Nothing would be dumped overboard on this mission – everything would be stored. The ESM would proved the crew with over 300 pounds of fecal containment bags and germicides. They would neutralize and store all waste as well as any excess food. The ESM was also stocked with over 30 pounds of medical supplies. The crew would have to be prepared to treat minor cuts and bruises or perform surgery if the need arose.

On a daily basis, the astronauts would have a healthy balance of work and play. Only 10 hours each day would be dedicated mission goals – experiments and observations, systems managements and monitoring, general maintenance, and transmission of biomedical data to mission control. The rest of the time would be a mix of relaxation (two hours a day – the launch weight included an allowance for books, movies, and games), eating, personal hygiene, and sleeping. Each astronaut would also have a forced two hour workout scheduled into each day on an exercise cycle. This, NASA hoped, would keep them from succumbing to muscular atrophy. (Left, Pete Conrad works out on an exercise bike during Skylab 2. 1973.)

So What Happened?

Unfortunately for historians – though perhaps fortunate for a possible crew – the manned Venus flyby was a thought mission. It was never something NASA seriously intended to fly. As the report from Bellcomm clearly states, “it is clearly not the intent of this study to recommend that NASA undertake a Venus flyby mission in 1973 or at any time.” Rather, the report was designed to demonstrate the mission’s feasibility within the confines of the Apollo Applications Program and could be used by NASA as a reference when developing long term missions. The whole mission profile could easily be applied to Mars, or any other interesting nearby object in space.

I suppose there’s always a slim chance NASA will revisit the idea in some attempt to find a use for Orion. It may not be as sexy as a mission to Mars, but a manned Venus flyby would be fascinating.

Suggested Reading/Source

M. S. Feldman et al. “Manned Venus Flyby” published February 1, 1967. Bellcomm.


  • Stu Young says:

    Amy, thanks for posting this mission profile on your blog. You covered some details of which I wasn’t previously aware, such as the deployment of solar panels from the ESM, the use of the ESM as a radiation shelter, the use of batteries alone in the CSM, the storage of waste, etc. (I’m assuming waste dumps were not planned because doing so may have subtly nudged the spacecraft off course, as feared during the Earth-return trajectory of Apollo 13.).

    One thing that I think I remember from other descriptions of this mission: I think that aborts could only be done within the battery capacity of the CSM, which, as you pointed out, was 60 days. That meant that there was a limited interval after Trans-Venus Injection, maybe only a few weeks, during which the crew could abort if something went wrong. After that window passed, there wasn’t enough delta-vee in the CSM to adjust the orbit into a hyperbolic trajectory which would return the crew to Earth within the 60 day time period.

    I also remember that the exercise bike was planned to be mounted on an axis parallel to the centerline of the SIV-B. The astronauts, as they pedaled, would circulate around inside the diameter of the SIV-B, and would experience centrifugal force which would press them down into their seat, varying according to their speed of rotation. It would in effect be a human-powered centrifuge; a low-tech version of the centrifuge on-board the USS Discovery in the movie “2001.” It’s a pity that a similar arrangement wasn’t installed on Skylab; my intuition is that such a contraption would be much more effective than the exercise equipment on board the ISS, perhaps completely negating the deleterious effects of zero-G on humans.

    I wonder, though: would the oscillations of the centrifugal bike cause the Venus flyby spacecraft to possibly go off course?

    -Stu Young

    • David VomLehn says:

      Simply reply–no, the centrifugal bike would not cause Venus to go off course. It could, and probably would, change the direction in which the spacecraft was pointing, but so long as the engines were not producing thrust at the time, it would make no difference. Specifically, there is only vacuum, no air to push against.

    • Stu, on the centrifuge question – the exercise bike would cause the spacecraft to spin on an axis, not change its direction. In Space Lab the astronauts ran around the running track for exercise, so that’s like your idea though not nearly as much g, it wasn’t the idea to give them gravity but they would have experienced some. I make it about 1/3 g, based on radius about 3 meters, and running at about 10 rpm, though they just did it for a short time. It’s interesting to speculate, would they have been able to counteract some of the effects of zero g by running like that, say, for an hour a day? (That’s assuming humans can withstand a spin rate of 10 rpm for an hour at a time running around a jogging track – if not – it would also give information about what humans can withstand). But nobody thought to do that experiment at the time, to measure physiological effect of running around the track for an hour a day.

      So anyway the ISS has momentum exchange gyroscopes – big heavy spinning weights to help keep it stable orientation in space. So you could use those, but also a simpler way – just have a weight in another counter rotating track – either have two astronauts cycling in opposite directions – or a weight that moves around in the other direction when you have no buddy to do it with you – or just a weight in an enclosed circular tube, that’s geared up so it moves in the opposite direction to your cycling at just the right speed to counteract the effects. It wouldn’t be too hard to arrange something or other.

      Here is my article about it.

      I’m interested to know more about this exercise bike for artificial gravity on the Apollo Venus mission. Do you know if anyone has written it up, are there any materials I can read about it – and add to the article?


  • Luke Togni says:

    A mission to Venus? I had no idea about this. Thanks for posting this.

  • […] hardware developed for the lunar program was ideal, so NASA commissioned a study on possible application of Apollo hardware to a manned mission to Venus. (Left, Venus traces an S as seen in the Earth’s […]

  • Amy:

    A bit of info for your readers, if you don’t mind –

    If you liked this, you should read my blog, Beyond Apollo:

    I describe hundreds of missions that were studied but not flown, and I provide a great deal of historical context, too. Most missions I describe date from the 1960s and 1970s, but I have some as recent as the past decade.

    The most important NASA study on piloted Mars/Venus flybys was this one:

    Piloted flybys were a big deal in the 1960s, though they are almost forgotten today. I also delve into this “lost” mission class in a history I wrote for NASA:

    There was also a proposal to put humans into Venus orbit:

    I like to call these proposals rather than plans because almost none of them got as far as the planning stage. The other thing I like to note about them is that they thought of just about everything in the 1960s, and planners today who are unaware of 1960s plans often start out by developing a plan that’s a bit broken and about half the time refine it so that it closely resembles the 1960s version. Then they present their results, unaware that they spent a lot of time developing something they could have read about in their friendly local tech library. That doesn’t mean that they are dumb, just that a lot of people tend to ignore history.

    David Portree

  • Strategos' Risk says:

    I have to wonder if a manned mission to Venus is all that implausible, even a landing mission. Given enough shielding, couldn’t astronauts explore the surface in armored vehicles?

  • Stu Young says:

    Possibly…The ships/rovers would have to be built like submarines; I think the pressure at the surface is something like 100 atm. The temperature is about 800 degrees F. The atmosphere is full of sulphuric acid as well.
    A manned landing on Venus was portrayed in the BBC docudrama “Voyage to the Planets and Beyond” (named “Space Odyssey” in the U.K.). A short visit of an hour was planned. They almost didn’t make it back to the mother ship, what with cameras melting, malfunctions of the primary ignition sequence, and all.
    As crazy about manned space exploration as I am, I think the Venusian surface is one destination I would turn down, if I was offered a flight there. There’d have to be some pretty valuable resources down there to make a manned landing worthwhile, IMO

  • David VL says:

    I’d sure want some uncrewed missions to test out prototypes of the equipment being used but, ultimately, what’s the use of having a space program if people aren’t experiencing and reporting as much as possible in person? It’s a crazy dangerous mission, but beats living your life in a Barcalounger!

  • […] Amy Shira Teitel gives us a historical account of what plans NASA had for Apollo-era hadware once the Moon program had completed. One mission idea was a manned mission to Venus. read more about this mission at: […]

  • Bruce Costello says:

    Amy – I much enjoyed your article. I would suggest that you consider writing a book on ‘lost mission’s’ such as this. I for one would be happy to buy a copy!

  • publius says:

    This is NASA CR-114025 and/or TR-67-600-1-1, accessible via the NASA Tech Reports Server at the following URL :

    (I find the publication number & NTRS reference to be highly valuable in cases such as this.)

  • epicjorik 1 says:

    this is not fascinating big lies

  • Limited Offer Apollo 12 The Nasa Mission Report

    […] it was the most reliable method available. (As seen from the LM, Dave Scott sta […]

  • […] other missions. And while there were studies that explored the possibility of sending a mission to Venus or Mars with Apollo hardware, the rationale to go was never there; these proposals were never more […]

  • Amy, I enjoyed your article, and wonder if you know about the Russian idea to build floating cloud colonies in the Venus atmosphere? Around the same time I think, well not much later, illustration from 1971

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