It might seem that a manned flyby – spending a year in flight to and from Venus in exchange for only a day at the planet for experiments, and no chance to touch the surface – would have only a limited scientific payback, but this was not simply a grand stunt; there were a large number of valuable experiments that could have been performed on this mission. Key goals listed in the planning documentation include the following:
To obtain and analyze surface samples.
To make measurements of the environment of Venus.
Reconnaissance and mapping of Venus.
To conduct a range of astronomical observations.
To conduct solar observations.
To make measurements of the interplanetary space environment.
As planned, a small flotilla of probes would have been released from the flyby vehicle as it approached Venus, and these could have been monitored in almost real-time by the astronauts passing by, allowing a far greater degree of control and response to split-second situations than was - or is - possible for unmanned probes. Design studies exist for a wide range of such probes. (As for operating them from a flyby, the Soviet Union used this technique for many of its Venera landers with success.)
One mission that would actually fly in the 1980s – as a Soviet unmanned probe – was releasing a series of balloons into the atmosphere of Venus. The primary goal would be analysis of the atmosphere and the weather pattens of the planet, preferably at a variety of atmospheric levels. (When balloons were flown in the Vega series in 1985, they were released at what turned out to be the most turbulent level of the atmosphere.)
A Venus orbital probe would also have been likely; the projections at the time were for a photographic study of the planet, and that could well have proven somewhat disappointing, but by the time the mission would have flown, a radar mapper could have been substituted instead; such technologies were sufficiently far advanced. A secondary role for the probe could have been as a communications relay, allowing the remainder of the probe flotilla to communicate with the flyby vehicle, and potentially Earth, at much greater ranges.
The hardest part of the mission would have been a sample return. In 1967 no spacecraft had been successfully soft-landed on Venus, but by 1973 the Soviet Union had attained great success with its Venera probes. This took several attempts, and the disheartening reality exists that the lander carried in the manned flyby could well have been unsuccessful, but it can be assumed that a precursor probe would have been landed as a test-flight.
Ultimately, landing a probe on Venus was a solvable problem. Sample return techniques were never worked out in any detail for Venus, but there were several studies for a Mars sample return. A mission profile would have seen a probe land on Venus ahead of the flyby, then launch a sample of the Cytherean (Venusian) surface to rendezvous with the manned flyby. Obviously, this would be a very complicated mission, and the likelihood of success would be limited – but it would be far easier for samples to be returned to a craft at close range than to return them all the way to Earth. Any lander mission in that era would have provided a wide range of data whether the sample was successfully retained or not. (It should be noted that at one time, the Soviet Union planned a similar mission to the moon, with an unmanned lander launching lunar soil samples to be retrieved by a craft on a lunar flyby.)
An alternative could have been returning a sample of the Cytherean atmosphere, captured by a high-altitude probe conducting a flyby of its own after skimming the upper layers of the atmosphere; this could have provided a range of data on atmospheric content even if the rendezvous was not attained.
It seems likely that several variations of these probes would have been deployed on the encounter with Venus; the sample return mission may have been a one-off, but a series of balloon probes and landers could have been dispatched to obtain readings from several points on the surface of the planet, and maximise data return in the event of probe failure. (Though again, an element of manned operation could have been used to help improve the chances of success, either in terms of rapid response to system failures or even the adoption of manual override techniques. I rate it as likely that any probe would have been controlled by the astronauts inside, to limit the obvious danger of catastrophic collision – some manner of self-destruct system would have been a probability for the same reason.)
Other mission objectives would have been accomplished with a fitted telescope. Obviously this would have been utilised for close-range observations of Venus as the flyby vehicle approached the planet, but a variety of other targets would be suitable as well. (Including Mercury; a manned flyby would have passed closer to the planet than any space probe planned in 1967.) A study into the potential uses of such a telescope included the observation of distant galaxies, taking spectra of various faint sources, and the long-term measurement of variable stars – something not possible from the surface of the Earth. There would likely have been other targets of opportunity during the mission as well – newly-discovered comets, or possibly asteroids.
The telescope would also be used for solar observation, especially as the craft made its closest approaches to the sun, to observe coronal phenomena, solar flares, and sunspot activity – many of the experiments carried out by Skylab, though at vastly closer range. Another possibility would be the collection of solar wind particles from interplanetary space for later analysis back on Earth.
The Earth would also be an intriguing target, and likely a popular one for the astronauts; there were suggestions that images should be taken at various ranges, and a 'family portrait' of the Earth-Moon system could have had the same popular appeal as the famous 'Earthrise' photograph taken by Apollo 8 in 1968.
It should be remembered that this manned flyby vehicle would effectively be a space station, simply one with a destination. The medical experiments that were conducted in Skylab could have been conducted in the manned flyby, over a significantly longer-period; these experiments were mostly low-weight, and would have been valuable in assessing crew performance over the period.
As for the craft itself, it would have greatly resembled Skylab in appearance; the Apollo CSM would have been used for mid-course manoeuvring, and the crew would have lived and worked in the S-IVB. Other studies suggest the design of an 'Environmental Support Module', which would have been placed in between the CSM and the S-IVB, which would have focused on life support systems and some experiments; in this configuration the S-IVB is simply used as living space.
As for recreational equipment, in a vehicle that was to weigh tens of thousands of pounds, thirty-three pounds were allotted for the following:
Exercise Device: 3 pounds
Recorded Music: 3 pounds
Movies: 5 pounds
Reading Materials: 20 pounds
Games: 2 pounds
One can only imagine that by the end of the mission, these movies and music tapes would have been worn out from overuse.
Assuming this mission had been approved, the next question is how it would have fitted into NASA's program in the 1970s. 1973 was an unrealistic target, and the next window was on June 4th, 1975; let us assume that this was the target date for the launch of the Venus flyby.
It is hard to see that Apollo would not have been affected by the adoption of this mission in 1967. The lunar landing would have continued as planned, up to Apollo 11, but with a refocus on extended operations away from lunar work, there is a good chance the the 'J' class missions would not have happened, the program limited to Apollo 11 and the following 'H' class missions. The development funding that went to upgrading the LM would have instead been spent on a CSM upgrade, the Block III proposed by North American in this period.
Apollo would have flown five landing missions; the program concludes with Apollo 15. (In our history, this was flown by Dave Scott, Al Worden, and James Irwin – given that the same scientific imperatives would have existed, the author speculates that Irwin would have been bumped fro
m his landing slot in favour of his backup, geologist Harrison Schmitt.) By 1971, the program would have started to refocus towards the new Venus objective. This would have had the additional benefit of freeing Saturn V boosters for Venus, as well as several Apollo CSM.
The planning document for a 'Manned Venus Flyby' outlines a realistic development schedule, with two test missions preceding the Venus launch. The first of these missions was to test the suitability of the spent S-IVB stage for long-duration spaceflight, and would have seen a launch of the complex into Earth orbit, with a duration of up to 28 days. The focus of this mission would have been as an engineering test flight, and would have used the standard Block II CSM.
The second flight would have been more ambitious, and would have tested the same systems in Earth orbit for a duration of a year – the length of the planned flight to Venus. Much equipment specific to the flyby would have been excluded, effectively making it a space station analogous to Skylab, with the first use of the Block III CSM, intended for use over an extended period. This would have focused on both engineering and medical testing, and the opportunity would no doubt have been taken for Earth Observation experiments. (For additional economy, it was suggested that this could use two Saturn IB launches, instead of a single Saturn V.)
Assuming these missions had been successful – and 1972 and 1973-74 suggest themselves as suitable timeframes – then the Venus flyby could launch in 1975. There would be windows of opportunity for additional Apollo missions in this period, in the context of test flights; a test of the Block III CSM could have been used to accomplish a 28-day Lunar Orbital mission, to conduct a complete orbital survey of the moon; this could also have been used to test equipment for the probe flotilla. Another flight under suggestion as part of Apollo Applications was to one of the Earth-Moon Lagrange points, to sample any material trapped at these points and determine its nature; this would have been of similar duration to a standard Apollo flight.
There would certainly have been a series of probes launched to precede man to Venus. An element considered essential was the launch of a Pegasus micrometeorite detector, to evaluate the potential risk of a meteor impact in interplanetary space. A Venus orbital probe would also have been likely, again to determine the nature of Cytherean space in context of protecting a crew. The 'Viking' soft-landers on Mars would be another likely casualty, replaced with similar landings on Venus.
As for the flight itself, the craft would have left Earth on June 4th, 1975, as indicated. 115 days would elapse before it made its approach to Venus; during this time a focus on astronomic surveys would have been taken, with the launch of the probe flotilla at pre-designated times. (One possibility would be the launch of some additional probes direct from Earth, still to be monitored from the flyby craft.)
During Venus approach, the craft would have been a hive of activity; the complete focus of the crew would have been on the planet, both on making their own observations with the on-board instruments, and monitoring the results of the probes coming in. Shortly after leaving the planet, rendezvous with any sample return craft would have been accomplished, and then the long flight back to Earth would have begun – 252 days before the crew would load themselves and their samples into the Block III CSM, separate from the craft that had been their home for a year, and return to Earth on June 5th, 1976.
The crew of the craft is a matter of conjecture, but it would likely have not been anyone who had flown on the two previous missions. There would have been any number of volunteers for such a flight, which would have carried the standard Apollo crew of three. The commander of the flight would have been an experienced astronauts, possibly one of the CMP from a lunar mission; someone like Dick Gordon, Ken Mattingly, Jack Swigert, or Gene Cernan might have been considered – or even a moonwalker – Pete Conrad might have been a possibility, Al Bean, Fred Haise, or even Dave Scott. The second and third seats would have gone to rookie astronauts – one of them an unflown Group V astronaut such as Jerry Carr or Jack Lousma, the third to one of the scientist-astronauts, though which would have been a matter of conjecture.
There were two choices. Those scientist-astronauts specialising in materials and engineering would have been ideal for the earlier test flights, but for the Venus mission, it would either have been a medical scientist, such as Joe Kerwin or F. Story Musgrove, or an astronomer, such as Curt Michel. While there would have been a bias towards the first scientist-astronaut selection, the final decision would depend on the astronauts flown on previous missions. A repeat mission is regrettably far less likely. It is unclear what would have been accomplished by flying the mission for a second time, and there would have been requirements for increased radiation shielding for a flight in, say, 1977.
One potential follow-up mission could have been to a near-Earth asteroid; as early as 1966, there were some proposals to send an Apollo-derived complex to intercept the asteroid Eros on a 527-day flight, with a flight complex not dissimilar to that projected for the Manned Venus mission; solar radiation would have been a concern, but as the flight would have been out towards the orbit of Mars, less of a concern than for a repeat of the Venus flight. A Mars flyby might also have been a possibility, but would have required improvements to the Saturn V if it was to be a one-launch mission.
But would this mission have ever actually been flown? More to the point, could it have been flown? In terms of booster technology, then certainly. The Saturn V could have thrown the flyby complex into the required trajectory without any modifications – the velocity required for a flight to Venus is no greater than that required to reach the moon, it just takes somewhat longer to get there! The Apollo CSM could have been modified to suit the requirements for re-entry at interplanetary speeds, there were numerous studies demonstrating this potential.
The problematic point would have been maintaining the life-support environment for an entire year, but this is not quite so far-fetched as it sounds. Skylab maintained a crew for periods of 28, 56 and 84 days, with the option for an additional 20 days – 188 days in total, half-way there. Given that there would have been a pair of test-flights from which much could be learned in the fields of atmospheric and water recycling and limiting atmospheric leakage, constructing a flyby module with the capability of sustaining a crew for 367 days was probably a realistic goal for 1975.
The biggest question mark would have been the health of the crew, and it would have been here that the second test-flight would have been absolutely essential. Until the Skylab program, the longest duration of an American space flight was recorded by Gemini 6, fourteen days. There were many unknowns in the period over the effects of prolonged spaceflight on an astronaut. Based on thirty years of data, we know now that given the proper exercise regime, it is possible for a man to survive for this period – there are several cosmonauts who have lived in space for longer than the duration of the Venus flyby mission. The question was – even if the test had been successful, would NASA have taken the risk?
The mission was probably flyable, albeit with a considerably higher risk factor than the Apollo lunar landings. It could have been accomplished, in the 1975 window, had the project begun in 1967 ( gutting the Apollo program in the process, most likely!) The scientific return would have been another question.
Undoubtedly a great deal of medical and astronomical data would have been returned from the Venus mission – but the returned data would have been little different from that returned from a year-long space station flight. As for the primary object of the mission, the Venus flyby – again, it is certain that a good deal of data would have been gathered from the flight, but the bulk of it would have been gathered from the unmanned probes being operated from the flyer. The same effect could have been gathered by unmanned probes over an extended period, as indeed was the case with the Soviet Venera and Vega probes. The difference would have been that the data would have been gathered in one grand, glorious moment, rather than spread out over twenty or thir
ty years.
The greatest effect would have undoubtedly been on the shape of the space programs of the USA and USSR over the next thirty years. If the USA had flown to Venus, then there would have been far greater motivation for the USSR to attempt a Mars flyby at some point in the 1980s. The pressure on NASA for more planetary missions would have been stronger, and the government might have been more favourably inclined towards future flights.
And yet...we haven't gone back to the moon. Would we have gone back to Venus, or on to Mars? I would like to think so...but I fear not.
As for the present day? Well, plans for planetary flybys fell into abeyance for many years, but lo and behold – as NASA evolved its Constellation plan for a return to the moon, and a potential progression to longer-ranged missions, manned flybys returned to the schedule, at point scheduled for the 2020s, shortly after a planned return to the moon. Now, however, Constellation is dead and buried, and once again, the manned flyby is off the books. Something about this mission seems to draw people...and one day, this mission profile just might be flown.
Bibliography
A Venus lander probe for Manned Flyby Missions, P. L. Chandeysson, Bellcomm, Inc., 1968
Alternate Apollo Missions: Liberation Points, John T. Wheeler, NASA, 1968
Drop Sonde and Photo Sinker probes for a Manned Venus Flyby Mission, R. N. Kostoff, Bellcomm, Inc., 1968
Experiment Payloads for Manned Encounter Missions to Mars and Venus, W. B. Thompson and others, Bellcomm Inc., 1968
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