 In the mid-1960s, NASA began planning what audacious goal it could take on after successfully landing on the Moon. One idea that gained a fair amount of traction was a manned mission to Venus, or a manned mission to Venus and Mars with a single launch, depending on the specific launch window. It sounds like science fiction, but studies showed it was perfectly viable as a next step for the space agency. Hello everyone, I'm Amy, this is The Vintage Space, my little corner of the internet where we talk about all things mid-century that frankly interest me. And space is one of those big topics that I love. Today we're revisiting a mission concept I've written about before, but have never done a proper video on, which seems nuts because it's one of my favorites, the manned Mars-Venus flyby missions NASA and contractor Belcom explored in the late 1960s. Before we get into the specifics of these mission proposals, we need to look at the post-Apollo era more broadly as it was shaping up in the mid-1960s with the Apollo Applications Program, or AAP. 1965 was an interesting time for NASA. The agency was just beginning the Gemini Program, which was testing some of the most vital technologies the agency would use on Apollo missions to the Moon, which were stated to start flying sometime in 1967. Everything looked great for the lunar landings completion by the end of the decade, but the agency was starting to lose support. Funding was waning, and NASA had no guarantees about its post-Apollo future. This uncertainty wasn't completely surprising. NASA was created in 1958 as a response to the Soviets launching Sputnik, and it was never guaranteed to last longer than the time it would take for America to launch a satellite or humans into orbit. But the Soviets' persistent lead in space compelled President Kennedy to challenge America to a manned lunar landing before the end of the 1960s. This goal gave NASA a raison d'etre. Apollo allowed NASA to grow. But with the finish line now in sight, what would happen next? The Apollo Applications Program and its planning office were thus created to help the agency figure out what to do with the Apollo hardware, infrastructure, and mission architecture. And it had spent so much time and money bringing to fruition. There were a few logical next steps for Apollo applications, namely two that had been favorites of spaceflight pioneers going back to the 1940s, an Earth-orbiting space station from which the agency could launch deep space missions and a human mission to one or both of our neighboring planets, Mars and Venus. Contrary to Apollo, which was an engineering challenge dictated by politics, I have a whole video about it right up here. The driving factor behind Apollo applications was science. Granted, the structure of NASA was such that nothing could be free from politics, but science would be at the center of future missions, whether it was understanding more about destinations in space, about human factors for long-duration missions, or larger questions like is their life on another planet. An abstract goal, however, wasn't enough. If NASA wanted to secure funding to continue building the Saturn V rockets and Apollo hardware, which it did, it would need a firm mission that could use that infrastructure. For some options on that mission plan, the agency turned to BELCOM, a division of AT&T established in 1962, to support the space agency by evaluating theoretical missions and running studies. BELCOM, in turn, focused on Venus and Mars. Though the missions got less media coverage than human flights, Mars and Venus were both big targets for the United States and the Soviet Union in the early space age. Up until 1965, the year NASA started defining its post-apollo goals, there had been more than a dozen planetary missions. Missions to Venus were, on the Soviet side, Sputnik 7, an attempted Venus impact, Venera 1, a flyby wherein contact was lost, Sputnik's 1920 and 21 all attempted flybys, Cosmos 21 thought to be a Venera test flight, Venera 1964A and B, which both failed, Venera 2 and Venera 3, a flyby and lander mission respectively, both of which lost contact with the Earth, and a final launch failure with Venera 1965A. The Americans had better luck. Mariner 1 failed at launch, but Mariner 2 launched successfully on August 27th and flew by Venus on December 14th, 1962, before settling into a heliocentric orbit. During its 45-minute-close flyby, wherein it passed within 21,000 miles of Venus' surface, it discovered the planet's slow retrograde rotation, hot surface temperatures, surface pressure, carbon dioxide-heavy atmosphere, cloud cover, and the lack of magnetic field. It was also the first mission to measure the solar wind. Mariner 2 also found that there was more to learn by probing into the planet's thick layer of clouds. Scientists even suspected that there could be a suitable surface for a manned landing under those clouds. Mars was slightly less of a mystery when the space age started, since lacking a thick cloud cover, astronomers and scientists had been observing it via telescopes for decades. And what astronomers could see, particularly surface features that looked like an active water system and possible vegetation, made it a very exciting potential place to visit. On the Soviet side, Mars Nix 1 and 2, also called Mars 1960a and Mars 1960b, failed at launch. Sputnik 22 attempted a flyby. Mars 1 lost contact on its flyby mission, as did Zont 2 and Zont 3. The Americans, again, saw more success. Mariner 3's attempted flyby failed, but Mariner 4 returned the first real look at the planet. The 5.2 million bits of data returned from the mission included images showing a moon-like crater terrain, which meant it could be landed on. The mission also found there was no magnetic field, that the surface atmosphere pressure was between 4.1 and 7.0 millibars, and that daytime temperatures were around minus 100 degrees centigrade. Scientists quickly hypothesized that the solar wind might have stripped away an ancient atmosphere. In both cases, data from the successful missions said the radiation levels in interplanetary space, even going towards the sun in Venus' case, were no worse than anywhere else outside the Earth's magnetic field. Since NASA was already dealing with the radiation issue for Apollo, it wasn't seen as a prohibitive limitation to stop studies into human missions. Mars and Venus were, in short, viable targets for reconnaissance missions, with Mars being of primary interest. Developing an interplanetary mission, even without a landing element, would not only teach NASA a lot about both planets, it would also show the agency was up for a demanding new challenge. Before we look at how humans could visit these planets, we need to step back for a quick look at how the Apollo missions worked, and specifically what technologies the Apollo applications program was looking to reuse. The Saturn Apollo stack wasn't exactly a multi-mission or multi-destination design. It was built specifically for Apollo, dictated primarily by the program's tight timeframe. The lunar mission was barely a glimmer in mission planner's eyes when, in May of 1961, and with one 15-minute suborbital mission in NASA's success log, President Kennedy challenged the country to a manned lunar landing by the end of the decade. I have a whole video right here about the lunar landing mission decision and how that timeframe was set. To fulfill the president's goal, engineers decided, in 1962, that instead of landing a large return vehicle on the surface, it would be simpler to land on the moon with a small dedicated lander. The heaviest part of the stack, the command service module with all the bulk of the mission's fuel and life support systems, would stay in lunar orbit. This lowered the mission's overall launch mass, making it feasible to mount a lunar landing flight on a single Saturn V rocket. So the hardware Apollo applications engineers had at their disposal was custom built for the lunar mission. The lunar module couldn't land anywhere else. It was designed to land without an appreciable atmosphere in one-sixth Earth's gravity. The command service module could be modified for other goals, too, but it was built to support a two-week mission since that's the average length to get to the moon and back. But if the mission didn't need the lunar module, taking that spacecraft away opened to the possibility for a new module that could support a longer flight, potentially a flight long enough to get to Mars or Venus. Between Mars and Venus as possible destinations, there was a stronger case for Mars. What little in-situ data NASA had said it was moon-like in terrain and far more manageable for potential landing. The challenge was getting there. The biggest stopping block for a Mars mission was the Mass for Initial Earth Orbit, or M-E-O, which is just the mass of the spacecraft and rocket that need to leave the Earth to start the mission. The exact mass varies depending on the relative positions of Earth and Mars when the mission starts, with the least mass of launch vehicle needed for a mission to Mars when that planet was at perihelion or its closest point to the Sun. But a mission would have an easier time getting to Mars if it actually went to Venus first. Flying to Venus to get to Mars sounds counter-intuitive since it's going in the opposite direction, but it makes a lot of sense. Think of our solar system as a gravity well, the Sun pulling everything towards it, but the planet's moving fast enough to be in a state of continual freefall. It's not quite the same, but you can think about it like water flowing around and towards a drain, the drain being the Sun. A spacecraft launching towards Mars needs a lot of delta-V or velocity to fight against that gravity well, and a lot less delta-V to go towards it. Going back to our imperfected drain analogy, going towards Venus, you're going with the water, and going to Mars, you're fighting against it. So if your spacecraft weighs X, let's just pretend X is a solid number right now. You would need a bigger, more powerful rocket to launch it to Mars than to Venus. In the case of AAP, if the updated Apollo stack weighs X, and you're limited by the power of the Saturn V, it makes sense to take advantage of the gravity well moving towards the Sun, and let Venus help you get to Mars. Planetary flybys are extremely useful for changing a spacecraft's trajectory. A planet's gravity is obviously far stronger than a spacecraft's. When a spacecraft passes by a planet, that planet pulls the spacecraft towards it, but with the right management of delta-V, if it's going fast enough, it can avoid being pulled into orbit and instead dip into the planet's own gravity well before being punted out. That punt comes with a transfer of energy. The planet transfers a little of its own momentum to the spacecraft. The effect on the planet is minuscule, but the effect on the spacecraft is significant. It will not only gain a lot of delta-V that dip into the planet's gravity well, will bend the spacecraft's trajectory. A perfectly timed Venus flyby can not only give the spacecraft the delta-V it needs to fight the gravity well and move outwards towards Mars, it can put it on the right course, too, all with the smaller launch vehicle that can't manage the direct Mars launch. This is obviously a different trajectory than a Hohmann transfer, a launch profile that sees a spacecraft travel half a solar orbit on its way to a destination. If we're talking about Mars, it would leave Earth when the planet is at its perihelion or closest point to the Sun and arrive at Mars at that planet's aphelion or furthest point from the Sun. The trajectory uses the Earth's orbit energy in conjunction with the rocket at launch to imbue the spacecraft with the delta-V it needs to fight the gravity well to go outwards to Mars. There's another reason to use Venus as a helper planet on the way to Mars. The ideal alignment for a direct Mars mission happens once every 18 months, but an ideal window for a mission to Venus happens every 12 months. You have more opportunities for the outer planet missions if you take advantage of the frequent Venus alignment. In studying possible trajectories, BELCOM acknowledged that propulsion developments like nuclear rockets safe for human missions could change things. But given the state of the art in the mid-1960s, the Venus swing by architecture was the best for a Mars mission. In a 1966 report, the BELCOM team identified five oppositions between 1978 and 1987 that could support this flight. And the timing was fortuitous. The late 1970s through 1980s was expected to be a time frame at wherein the Mars mission would take center stage for NASA and the country. BELCOM went beyond just identifying possible dates and outlined a full mission with hardware and everything. A 1967 BELCOM report went into detail on a three-man Venus flyby launched in November of 1973. The whole month was the launch window for this study. This study aimed to show early capability for manned interplanetary flight and the ability to obtain scientific data beyond the moon. Similar to Apollo, the mission was broken into phases. Launch, Earth parking orbit, Venus injection, outbound leg, Venus encounter, inbound leg, and Earth return. So let's take a look at that mission by breaking down the spacecraft stack as envisioned by BELCOM. The mission hardware used a command and service module similar to what was used on Apollo, a new environmental support module in place of the Lunar module and a spent S4B stage to serve as an additional habitable module. The CSM would reprise its central role from the Apollo flights only instead of the lunar capable block two version, the Venus mission would use an upgraded block four model. It would be the main part of the spacecraft responsible for guidance, communications, reaction controls, Earth landing with the crew at the end of the mission, and electrical power for the launch and landing phases. It would also have power and provisions to support a post-Venus injection abort. This spacecraft would also be the main propulsion center for the flight. It would power the Venus injection burn that would send the whole spacecraft to Venus as well as transposition and docking, recovering the spacecraft elements from their stored launch configuration. Attitude control during course correction burns and the abort burn should one be needed. Keeping all of the main propulsion to this spacecraft was a way to minimize the stack's overall cost. The mission only needed one big propulsion source and the associated fuel stores. But in place of the single service propulsion system engine that would power Apollo missions, the Venus iteration would use two Lunar module descent engines. Their total mass was about the same as the SPS engine, but having two brought a measure of redundancy and therefore reliability. One of the CSM's most vital jobs was communications, maintaining a strong and constant link with Earth. Though there would be space for the crew to return as much as 100 pounds of data in the form of tapes, exposed films or other physical means, there's expected to be so much more gathered on the flight. The CM would constantly transmit data back to Earth via the same unified S-band communications Apollo would use going to the moon, supported by the World Wide Tracking Network to ensure there was never a break in contact. The radio signal was expected to be strong enough to support TV broadcasts from interplanetary space, too. The command module's other big job of guidance and navigation was again functionally similar to Apollo. I have a video on how Apollo's navigation works right up here, but in short, the mission was planned such that the computer could check the spacecraft's position against known stars and other targets periodically, backed up with an astronaut sighting with a sextant. The same would be done to Venus with the software program updated to reflect the different destination. Control, which includes attitude stabilization in flight, was a little harder since spinning the whole spacecraft might interrupt communications or sighting during experiments. BELCOM thus recommended a momentum exchange system like Reaction Wheels or gyros for control. Though it played a key role throughout the flight, the command module wouldn't be the crew's main living or working space. Here is where the new modules come into play. The environmental support module launched in place of the lunar module and provided the crew with long-direction life support, served as the main environmental control system in flight, and housed the bulk of the onboard experiments. It could do so much because it was large. About 660 cubic feet compared to less than 300 for the Apollo command module. Though important, the ESM would be fairly spartan in terms of crew comforts since it was about experiments and resource management. There would be plenty of room for one of the astronauts to monitor all systems from a central chair. One of the astronauts could sit at the experiment bay. The third man could either be sleeping, preparing food, or engaging in personal hygiene. The ESM was also crucial in emergency situations. The bed in this module could double as a medical cot where a sick man could be under constant observation. It was also the module that would serve as a radiation shelter in the event of a solar flare. More on that in just a couple minutes. The final module was a disused S4B. This would be turned into a larger living space from which the crew could also monitor experiments and gain electrical power from externally mounted solar panels that would supplement the fuel cells and a possible nuclear power source. When it came time for Earth Reentry, the command module would be the only part of the spacecraft to return safely, bringing the crew with it. The reentry would be fast, about 45,000 feet per second. For reference, Apollo missions were expected to reenter at around 36,000 feet per second. But all studies said the spacecraft was capable of protecting the crew with this higher speed. All it needed was an additional 430 pounds of a blade of material on the heat shield. Included within these three modules was everything the crew would need to live. There would be sleeping accommodations, enough dry and reconstitutable food for all three men, clothing, tools, and equipment for maintenance and repairs, and personal hygiene equipment. It would also have all the wellness supplies they might need, including exercise equipment, medical equipment, and books, movies, music, and games for mental health. But the most important thing on the human side was maintaining the environment for 400 days. The actual mission could be shorter, but this was a good number for figuring out needs. One of those needs was water, identified as the heaviest element of the entire mission. Anticipated to weigh 10,300 pounds, water was needed for drinking and food preparation, as well as hygiene. Gas was another vital element. The onboard environment would be mixed 70% oxygen and 30% nitrogen at five pounds per square inch for the duration of the flight. There was, at the time, no research done on a crew's long-term exposure to pure oxygen, which was the gas of choice for Apollo. So this more complicated but safer setup was chosen for this flight. Managing waste was a separate issue since there would be a lot of it in many forms. Washwater exhaled carbon dioxide, urine, and fecal matter. There could be upwards of a pound and a half of waste generated from the crew every day. Washwater reclamation through filtration and germ-style treatment was the easiest way to manage waste. Capturing exhalation and perspiration could also be recovered through condensation. Carbon dioxide would be controlled by a molecular sieve with lithium hydroxide canisters as those used on Apollo retained as a backup method, but extracting oxygen from the exhaled gas was too complicated and heavy at the time. There was no provision for growing food on board, so no way to use feces as fertilizer. It would be germicidally processed, dried, and stored. The resulting gases vented out into space. There would be no artificial gravity on the mission. Research at the time said the crew would be fine without spinning the spacecraft to create a gravity environment so long as they exercised regularly. There were similarly no plans for EVAs except for emergency repairs to the spacecraft. On this point, the proposal did address known hazards, namely radiation and meteorites. Radiation was, at a time before humans had spent more than two weeks in Earth orbit, not thought to be an issue. The consensus was that the basic spacecraft offered enough radiation shielding, especially if a mission launched at a period of minimal solar activity. The problem arose during a solar flare, something that would threaten the crew with a burst of radiation. To guard against this, the crew would use an onboard warning system of nuclear portable detectors and dosimeters, the same ones that were planned for use on Apollo. In the event of a flare, they could shelter in the ESM for a few days while the radiation dissipated. Debris and rocks posed a separate hazard, both erosion from small particles or punctures from larger ones. To keep mass low, but the spacecraft protected, only the most critical systems would be heavily shielded with added aluminum shielding. The probability of collision with a large asteroid was thought to be so vanishingly small that there were no precautions taken against it. For all the specifics this report explored, there remained limitations. Building a 400 day mission based on hardware design for a two week flight meant a good amount of guesswork was involved. More broadly speaking, spaceflight on the whole was still in the state of learning. Additional longer missions would change the understanding of deep space missions with a crew. And if NASA did pursue a Venus swing by to get to Mars, this version of the spacecraft could only serve as a jumping off point for real planning. Further work from Belcom elaborated on the proposed Venus flyby, taking this basic idea and turning it into a multi-flyby mission to both Venus and Mars. These additional studies highlighted other launch windows in both 1977 and 1978 for multi-planet flybys. NASA even explored its own concept for a Venus mission in 1967. Looking at launch dates between 1975 and 1986, NASA also determined the flight was doable with Apollo Air Propulsion, meaning the same mission hardware could support these flights. Though advanced chemical or even nuclear propulsion could make strides in weight reduction. Again, it found the Venus mission easier from a mass perspective than the direct Mars flight. Missions within the window NASA identified range from 360 to 660 days, the longer missions having stays at Venus as long as 100 days and high eccentric orbit. Shorter missions as quick as 400 days with a 20-day stay also were possible within this timeframe. The Belcom studies were intended to show that such a mission was feasible. But as we know, no human missions were sent to other planets in the 1970s. But the idea of turning the S-4B into a living space did fly. There was discussion of refitting the rocket stage into a laboratory either after launch as a wet lab concept or pre-launch as a dry lab setup. This goal was realized as Skylab, an unflown S-4B was turned into a laboratory and launched on May 14th, 1973. It housed three crews, the last of which departed on February 8th, 1974. The station de-orbited and re-entered the atmosphere over Australia on July 11th, 1979. I hope you guys enjoyed that jaunt into missions that weren't. If there are other concepts you've heard about and you're interested to know more, let me know in the comments and I'll see what I can't think up. I've got a couple more in the pipeline before we dive into our mini-series on Explains. Until then, I want to remind you guys that my new book, Fighting for Space, is available however you like to consume books and also now available lightly updated in paperback, which is very exciting. My first book, Breaking the Tains of Gravity is also still widely available. I have links for both of those in the description below. A very special shout out to all of my Patreon supporters and YouTube members. You guys truly make these videos possible, so thank you so much for your ongoing support. I honestly could not do this without each and every one of you. If you would like to help keep the vintage space up and running, I've got the links you need in the description and of course all the links to connect across social media. Thank you guys so much for spending some of your day with me today. I do appreciate it and I hope to see you next time.