By Matthew Kresal
A Saturn V rocket sits on Launch Pad 39A at the Kennedy Space Center in Florida. On top of it, three astronauts await lift-off. The journey they will soon be embarking upon will take them even farther out into space than their comrades on the Apollo moon landings. They will spend thirteen months away from Earth, arriving back home in time for Christmas 1974. Their destination is not the Red Planet, for that goal is still some years off. Instead, they will be venturing forth to is another of Earth's celestial neighbors among the inner planets: the elusive, clouded world of Venus.
This mission, known as the Manned Venus Flyby, was among the ambitious projects proposed by NASA in the 1960s as it neared President Kennedy's goal of putting a man on the Moon by the end of the decade. With success seeming more likely than not by 1966, those at the NASA headquarters began turning their sights towards the agency's future. With contractors and hardwire in place from Apollo, the resulting effort came to be known as the Apollo Applications Program (AAP).
AAP presented an ambitious vision of NASA's future, built around the hardware and expertise necessary to make Apollo a reality. As envisaged across 1966-67, it was one that would take in a lunar base and a space station, known as a "wet workshop," using the S-IVB stage from the Saturn family of rockets. All of which would extend a human in presence in space while building-up experience for long-duration spaceflight. What AAP lacked was a finale, or perhaps even an overall goal.
In February 1967, engineers from Bellcom, Inc. thought they found one. Based near NASA's headquarters in Washington DC, Bellcom was an off-shoot of Bell Labs created in 1962 to provide advice directly related to Apollo. As David S. F. Portree noted in a 2012 Wired piece on their proposed lunar exploration program, the "organization rapidly expanded its bailiwick to support nearly all NASA Office of Manned Space Flight advance planning." It was perhaps no surprise then that Bellcomm would throw an ultimate objective for the AAP into the mix.
Their proposal, published in February 1967, was entitled Manned Venus Flyby. After studying the mechanics of such a journey and the state of the expected Apollo hardware, the engineers laid out a three-phase plan. The first two phases, A and B, would be developmental missions testing the concepts and hardware used in the flyby itself, designated Phase C.
Phase A would be to test the feasibility of the proposed "wet workshop" that would be the crew's home on such a voyage. The "wet workshop" would be an S-IVB stage launched that, upon arrival in orbit, would be drained of any remaining fuel, and the now-empty interior would be a living space for the crew who would dock with it via an Apollo Command Module. This Phase A spaceflight would last for a few weeks and resembles the Skylab missions eventually flown in the early 1970s (albeit it with a "dry workshop" instead of a "wet" one).
If Phase A proved the "wet workshop" concept, Phase B would be a check-out mission. Phase B would see a Saturn V used to launch a modified Command Module and S-IVB into a high orbit for a year. Doing so would test the deep space worthiness of the flight hardware, especially the proposed Environmental Support Module inside the Spacecraft-LM Adapter (SLA) that once held the Apollo Lunar Module on lunar missions. The mission would be just far enough away from Earth's radiation belts to simulate deep space while also being close enough that a crew could use a Command Module to return to Earth within hours in the event of an emergency.
If both A and B worked as planned, then Phase C, the flyby of Venus itself, would launch at the end of October 1973. A modified Command and Service Module would carry the crew into orbit atop a Saturn V, with the Service Propulsion System (SPS) engine replaced by two used on the descent stage of the Lunar Module. Offering redundancy in place of the single SPS potentially failing, the crew would use these to dock with the S-IVB before leaving Earth orbit, performing a systems check in a parking orbit as the astronauts would have to use those engines in the event of a burn failure by the S-IVB.
If the S-IVB burn went successfully, the crew would be on their way to Venus. The larger fuel tank inside the stage would serve as living quarters, while a smaller one tank housed waste for the duration of the voyage. The crew would spend approximately four months in transit before an encounter on the third of March 1974, performing various astronomical experiments, including radio and x-ray astronomy, during the voyage out.
The encounter itself would last only a few hours and be at a distance of some 3000 miles from the planet itself. It would be a busy few hours for the crew, who would have a series of experiments to perform. Among those suggested included a side-scan radar, used to penetrate the clouds to map the surface of the side facing the spacecraft as they passed by. The crew would also launch a series of atmospheric probes to enter the Venusian atmosphere, ranging from meteorological balloons to landers. These landers would both be "hard," to crash into the surface, and "soft," taking photographs and examining the Venusian soil.
Following the Venus flyby, the crew would begin an almost nine-month journey home. One that would see the highlight of a long-distance encounter with Mercury a fortnight into their transit, passing within 0.3 Astronomical Units (27.9 million miles) of this innermost planet of the solar system. The three astronauts would also continue their astronomical experiments, including learning more about particulate radiation, magnetic fields, and meteoroids in the space between Venus and Earth. The crew would also have an amount of inflight entertainment, as Paul Drye noted in a 2012 piece at False Steps. These would have included “viscous damper exercycle/g-conditioner,” plus "1.5 kilograms of recorded music, 1 kilogram of games, and 9 kilograms of reading material." Finally, the thirteen-month mission would culminate in a splashdown in the South Atlantic on the first of December 1974.
The Manned Venus Flyby was an ambitious goal, fitting in with NASA's image of itself in the post-Moon landing era. That vision was to prove out of step with the prevailing mood of the country and, in particular, Congress. Eighteen months after the proposal's publication, the House of Representatives voted to cut funding for the AAP as part of a wider NASA budget cut in August 1968. The decision was to have a knock-on effect on virtually all of the AAP proposals, culminating in the 1973 launch of the Skylab space station, visited by three crews between May 1973 and February 1974. Venus was to remain visited only by robotic probes, including Soviet Venera probes in the 1970s and 1980s, as well as the US Magellan probe in the 1990s and the European Space Agency probe Venus Express in the early 2000s.
The cancelation of the mission might have been to the benefit of the future of human space flight. As Paul Drye noted in 2012, July 5 and 6, 1974 saw a sizable coronal mass ejection (CME), a storm of electrons and protons thrown off of the Sun, hit the Earth. While those of us on the ground were unaffected by the CME, a crew returning from Venus might not have been so fortunate. Just another of the what-ifs that surround this voyage that never was.
(Interested readers may be interested in checking out this YouTube video, made by Rseferino Orbiter Filmmaker, of the proposed mission based on the plan made using the Orbiter 2010 spaceflight simulator.)