Missions that Weren’t: NASA’s Manned Mission to Venus

Article written: 19 Dec , 2011
Updated: 24 Dec , 2015


In the mid-1960s, before any Apollo hardware had flown with a crew, NASA was looking ahead and planning its next major programs. It was a bit of a challenge. After all, how do you top landing a man on the Moon? Not wanting to start from scratch, NASA focused on possible missions that would use the hardware and software developed for the Apollo program. One mission that fit within these parameters was a manned flyby of our cosmic twin, Venus. 

As one of our neighbouring planets, a mission to Venus made sense; along with Mars, it’s the easiest planet to reach. Venus was also a mystery at the time. In 1962, the Mariner 2 spacecraft became the first interplanetary probe. It flew by Venus, gathered data on its temperature and atmospheric composition before flying off into a large heliocentric orbit. But there was more to learn, making it a destination worth visiting.

A scale comparison of terrestrial planets Mercury, Venus, Earth, and Mars. That Earth and Venus are of a similar size led many to draw comparisons between the planets before better scientific experiments revealed Venus is closer to the Earth inside out. Image Credit: NASA/courtesy of nasaimages.org

But beyond being relatively practical with great potential for scientific return, a manned mission to Venus would prove that NASA’s spacecraft and astronauts were up for the challenges of long-duration interplanetary flight. In short, it would give NASA something exciting to do.

The mission proposal was published early in 1967. It enhanced the Apollo spacecraft with additional modules, then took the basic outline of an Apollo mission and aimed it towards Venus instead of the Moon.

The crew would launch on a Saturn V rocket in November of 1973, a year of minimal solar activity. They would reach orbit in the same Command and Service Modules (CSM) that took Apollo to the Moon. Like on Apollo, the CSM would provide the main navigation and control for the mission.

Going to the Moon, Apollo missions had the crew turn around in the CSM to pull the LM out of its launch casing. On the mission to Venus, the crew would do the same, only instead of an LM they would dock and extract the Environmental Service Module (ESM). This larger module would supply long-duration life support and environmental control and serve as the main experiment bay.

An artist's impression of the Mariner 2 probe. Image Credit: NASA/courtesy of nasaimages.org

With these two pieces mated, the upper S-IVB stage of Saturn V would propel the spacecraft towards Venus. Once its fuel store was spent, the crew would repurpose the S-IVB into an additional habitable module. Using supplies stored in the ESM, they would turn the rocket stage into their primary living and recreational space. On its outside, an array of solar panels would power each piece of the spacecraft throughout the mission.

The crew would spend 123 days traveling to Venus. Ten hours of each day would be dedicated to science, mainly observations of the solar system and beyond with a telescope mounted in the ESM. UV, X-ray, and infrared measurements could create a more complete picture of our corner of the universe. The rest of each day would be spent sleeping, eating, exercising, and relaxing — a full two hours of every day would be dedicated to unstructured leisure, a first for astronauts.

Like Mariner 2 before them, the crew would flyby Venus rather than go into orbit. They would only have 45 minutes to do close optical observations and deploy probes that would send back data on the Venusian atmosphere in realtime.

After the flyby, the spacecraft would swing around Venus and start its 273 day trip back to Earth. Like on an Apollo lunar mission, the crew would transfer back into the Command Module before reentry taking anything that had to return to Earth with them. They would jettison the S-IVB, the ESM, and the Service Module, switch the CM to battery power, and plunge through the atmosphere. Around December 1, 1974, they would splashdown somewhere in the Pacific Ocean.

Though worked out in great detail, the proposal was a thought experiment rather than something NASA was seriously considering. Nevertheless, Apollo-era technology would have managed the mission.

Source: NASA Manned Venus Flyby Study

The surface of Venus as captured by Soviet Venera 13 lander in March of 1982. NASA/courtesy of nasaimages.org

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32 Responses

  1. Anonymous says

    This kind of makes you wonder why we do not have a “curiosity” type mission going to venus.

    • Bertie Seyffert says

      I think it’s a simple matter of us not being able to build anything (much less a rover) that can survive longer than a couple of hours/days under those extreme conditions. Afaik the Vega 1/2 aero-probes hold the record at 46 hours, but they did so hanging at an altitude of ~50km where conditions are more earth-like. Basically Mars missions offer much more science for the same cost. IMO Venus Express was the best compromise…

      But yeah, a rover on the surface of the most volcanic planet in the solar system would be friggin awesome 😀

      • M Selman says

        Here’s a nice animation showing a Venus Rover.

        Friggin awesome in:Deed

      • Anonymous says

        Your link to the “NASA promotional video showing a concept of how they could explore Venus with a group of robots” was very interesting. As one reader, Thanks for the link.

        It would be a feat to steer and level a solar-powered flier at an altitude (if one exists), were it would not be torn apart by ferocious winds at one level, or begin a death spiral from acid cloud mists(?) eating through its outer hull, and eating away its cells and electronics, on another. (Acid proof exterior, I guess.)

        The little metallic explorers (of heat-reflective design for maneuvering around the floor of a furnace) remind me of a Namibian(?) beetle which raises itself up-high, to stand on stilt-like legs, and so keep its (heat-resistent?) body from slowly roasting as it moves along the burning sand-dunes of the hot desert.

        That vintage concept of a journey to Earth’s terrible twin was an eye-opener. As others commented, it does sadly highlight a loss of bold vision, and its daring imagination: of concepts and plans to reach foreword, and outwards into the unknown, rather than shrinking back from the challenging frontiers of pioneering discovery and courageous exploration.

    • Anonymous says

      The problem is the surface of Venus is 600C, which is not very friendly to electronics, motors and so forth. At temperatures between that of an autoclave and a blast furnace it is very tough to keep this heat from turning any system into junk. The Russian Venera probes only lasted an hour or so before the heat and pressure destroyed it. Any rover would require some incredible heat pump, probably powered by a nuclear reactor, to keep the interior and critical systems at a temperature several hundred degrees C below the outside. Then consider the cost this would entail!


      • Anonymous says

        Even reactors have waste heat dissipation issues of their own…

      • Member
        IVAN3MAN_AT_LARGE says

        Yo LC, New Scientist had an article about such a rover using a Stirling engine cooler: Antique fridge could keep Venus rover cool.

      • Torbjörn Larsson says

        … aaand I nailed it! The Stirling cooler is capable to get down to 200 degC, so they propose 300 degC SOI circuitry.

        Which is fairly standard by now. In fact I would be surprised if not modern processors use SOI CMOS to get away with generating more heat than the surface of the Sun (!) per surface area, while also enable shrinking dimensions. SOI makes less parasitics and makes away with those runaway junctions.

        So maybe you could just throw a laptop circuit board into that cooled compartment. =D

      • Torbjörn Larsson says

        Well, now.

        First, the average surface temperature on Venus is ~ 460 degC.

        Second, while silicon bipolar transistors labor under the pernicious effect of a positive thermal coefficient so they enter thermal runaway somewhere beyond ~ 125 degC, there are plenty of extreme temperature technologies:

        “2) What are the temperature limits of electronics?

        At the low end, operation of semiconductor-based devices and circuits has often been reported down to temperatures as low as a few degrees above absolute zero, in other words as low as about ?270°C. This includes devices based on Si, Ge, GaAs and other semiconductor materials. Moreover, there is no reason to believe that operation should not extend all the way down to absolute zero.

        On the high end, “laboratory” operation of discrete semiconductor devices has been reported at temperatures as high as about +700°C (for a diamond Schottky diode) and 650°C (for a SiC MOSFET). Integrated circuits based on Si and GaAs have operated to +400?500°C. Si ICs have been reported to operate at +300°C for 1000 hours or longer.

        Covering both extremes, there are reports of the same transistor working from about ?270°C to about +350 to +400°C, an operating temperature span of over +600°C!

        3) Are these temperature limits attainable for practical applications?

        At the low-temperature end, practical operation of devices and circuits is reasonably achievable to as low a temperature as desired, bearing in mind that materials and designs appropriate to the temperature must be used. The various characteristics of a device may improve or degrade. In particular, below about 40 K (about ?230°C) Si devices often exhibit significant changes in characteristics.

        The high-temperature end presents more difficulty. The practical upper temperature limit is determined by many factors and for semiconductor devices often does not reflect the inherent temperature limit of the semiconductor material. The limit is frequently determined by the interconnections and packaging, both for active devices and passive components. As an indication of the practical upper limit, circuits have been offered commercially for operation up to +300°C [for example see http://www.ssec.honeywell.com/hightemp/%5D.

        Parts availability is a major obstacle to practical ETE; there are few components specified for either low- or high-temperature use. Persons needing to construct ETE hardware often have to select and adapt from the available “traditional” temperature range component base. Those with greater resources and time have sometimes followed the path of custom fabrication.”

        [Source: Extreme-Temperature Electronics Newsletter Issue #1 (26 April 2001).]

        While there are still no SiC ICs fit to run at ~ 500 degC what I know of (it is a dated source), if a Stirling cooler can get the temperature below 200 degC there is plenty of leeway for system construction. Even 300 degC could suffice.

      • Anonymous says

        Sure enough you can do this, but I suspect it will not come cheap. A Venusian rover would probably cost several times what a Martian rover would cost. The question is how space science dollars are going to be spent. If the choice is between $10B on systems such as space telescopes, gamma ray detecting spacecraft, space based gravity wave imagining and so forth or with putting a rover-probe on the surface of Venus I have to vote for what I see as more fundamental research.

        I did the temperature conversion in my head converting from 900F to Celsius, but I used the .6 conversion for km to miles for some reason


      • Member
        IVAN3MAN_AT_LARGE says

        I did the temperature conversion in my head converting from 900F to Celsius, but I used the .6 conversion for km to miles for some reason.

        Did you ever work for NASA, Mr Crowell? 😉

      • Anonymous says

        No, Lockheed Martin 😀

      • Member
        IVAN3MAN_AT_LARGE says

        The Lockheed Martin engineering team had used Imperial measurements (typical of American-based companies!), but it was the boys at NASA who had failed to notice and make the required conversion to metric measurements. 🙂

      • Anonymous says

        I stand corrected 🙂

      • Anonymous says

        Actually contact was often terminated when the relay moved out of range:

        “Venera-11 landed at 14° S 299° E. Conditions there were 92.6 atmospheres of pressure and a temperature of 452° C (846° F). It remained in radio contact for 95 minutes, until the bus vehicle moved out of range.”

        Also talk about machinery tolerating the temperatures isn’t hypothetical:
        “By the time of Venera-13 and 14, a surprising amount of complex equipment was simply installed outside the pressure hull, exposed to the intensely hostile surface conditions. By this time, Soviet engineers had developed new heat-resistant materials and electronics that were comfortable in this working environment.”

        See the wonderful http://www.mentallandscape.com/V_Venus.htm for more.

      • Anonymous says

        The article in:


        talks mostly about these probes “surviving until being crushed.”


  2. Anonymous says

    Not sure if we have anything that could survive the crushing atmospheric pressure. A high altitude areal craft might work. Solar powered, lighter than air, drifting along with the winds, and observing weather patterns.

    • M Selman says

      Pressure is no big problem. Remotely operated vehicles and manned submarines operate under similar extremes. Russia’s landers fared well; their titanium pressure vessels are probably still intact today. It’s the heat that burned and melted their electronics. High temperature components and better insulation may be employed in the future to enable several hour, or even month long missions. There are concepts for advanced weather balloons, but the lack of cameras in their design are deplorable. What public engagement can you get with wind speeds and spectrum graphs?

    • Anonymous says

      I should mention that even though the duration was limited, high altitude aerial craft *have* worked on Venus:
      “The aerostats were deployed at the anti-solar point of Venus, above the continent of Aphrodite Terra. During 46 hours of operation, they traveled about 1/3 of the way around the planet in the 240 km/hour zonal winds.”
      “Signals stopped when batteries were exhausted, and it is not known how much longer the balloons survived.”

      See http://www.mentallandscape.com/V_Vega.htm for more.

    • Anonymous says

      I should mention that even though the duration was limited, high altitude aerial craft *have* worked on Venus:
      “The aerostats were deployed at the anti-solar point of Venus, above the continent of Aphrodite Terra. During 46 hours of operation, they traveled about 1/3 of the way around the planet in the 240 km/hour zonal winds.”
      “Signals stopped when batteries were exhausted, and it is not known how much longer the balloons survived.”

      See http://www.mentallandscape.com/V_Vega.htm for more.

  3. Member

    The crew would spend 123 days traveling to Venus. […] After the flyby, the spacecraft would swing around Venus and start its 273 day trip back to Earth. […] Though worked out in great detail, the proposal was a thought experiment rather than something NASA was seriously considering.

    My first thought was: what about the problem of the need to go to the john?

  4. Anonymous says

    Great article!

    A bit sad that it shows a time when NASA dreamed and was much more ambitious.

  5. William Sparrow says

    Oh, do I dream of the days when NASA engaged in bold projects and the advancement of planetary science…..Damn the US Congress!

    • William, while I understand your comment, as a 37-year NASA employee I’ve gotta tell you are biggest problems are all internal. We could easily take a 10% budget cut – or more – and get more done for science, exploration, and for creating sustainable space industries, if we just changed what we did, and how we did it.

      Our biggest problem inside my agency, NASA, is NOT money; it’s attitude.

      • William Sparrow says

        Dave, Thank you for your response. Certainly NASA’s beaurocracy is responsible to some degree, the fact remains that Congress increasingly devalues scientific research in general and space sciences in particular with its move toward a more conservative, theocratic mindset. With NASA’s budget at less than 1% of the Federal budget, the future certainly looks bleak.

  6. Todd says

    Excellent post. Apollo Applications was where Al Bean was assigned until Pete Conrad tapped him on the shoulder for his Apollo 12 crew.

    Unless one of the planned lunar missions (Apollo 18, 19, 20) were cancelled, there wasn’t a spare Saturn V to do the heavy lifting for a Venus flyby.

    Another note about a mission that might-have-been: if they had kept Apollo 18 to send to the Marius Hills. Imagine that crew discovering the skylight over the lava tubes there. That would have been pretty darned exciting.

  7. M Selman says

    This would have been awesome. Humanity’s first interplanetary voyage.

    But it never was.

    I remember reading an olde mission PDF describing how the aluminum tanks would provide decent radiation protection. Then I watched a documentary telling how aluminum is unfavorable, because of cosmic rays striking the hull, producing a shower of secondary particles.

    • Torbjörn Larsson says

      The newly constructed ESM would be the radiation shelter accoring to Teitel’s reference.

      That said they did a primary radiation estimate as you surmised. And optimistically a linear r^-1 extrapolation to Venus orbit instead of a proper r^-2 estimate.

      So maybe we are lucky they didn’t try to pull that one off. (O.o)

  8. squidgeny says

    Nice article. I hope this is part 1 in a series of “missions that weren’t” posts 🙂

  9. Edward Morbius says

    This is actually a dumb idea. What is the point of sending humans on a mission where their presence adds no additional knowledge to the mission. You have to provide life support for the humans which ends up taking up space that should be used to carry scientific equipment. By the time this mission was planned they knew that Venus was inhospitable and it would have been impossible to land humans on Venus. On the other hand, if they had planned a similar mission to Mars that would be fine because there is the possibility of landing humans on mars.

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