Rod Pyle's Secrets of Apollo: the missions that might have been

The lunar missions of Apollo are well chronicled, but there were extensive plans made for follow-on missions, of which only 1973 ‘s Skylab and 1975’s Apollo-Soyuz survived.

Starting in the mid-1960s, the Apollo Applications Program, which was overseen by Apollo 12 and Skylab astronaut Alan Bean for a time, dreamed up various ways to continue using Apollo hardware after the lunar landing program.

These included Apollo-derived space stations, lunar outposts, Lunar Module-based 'moon trucks' and even a possible Mars flyby.

But of these mission plans, perhaps the most inspired—or outlandish, depending on your point of view—was one that outlined a crewed flyby of the planet Venus.

NASA had flirted with the notion of sending a spacecraft on a free-return trajectory to Mars, Venus, or possibly both for a number of years.

A number of studies were contracted out and while complex and expensive, there were no technical hurdles that could not have been overcome with enough engineering and money.

The Saturn V had the power to launch the spacecraft toward Venus, the Apollo capsule would soon be battle-tested via the lunar flights, and the upper stage of the Saturn rocket- the S IV-B stage - could have been converted into a habitat for the Venus-bound explorers.

Protecting them from the ghastly amounts of solar and cosmic radiation was another matter, and a major solar event such as a coronal mass ejection, could have done serious harm to the astronauts, even with extra shielding installed in the Apollo capsule.

Nonetheless, the plan was seriously considered for a time.

The round trip to Venus and back would have taken just over a year, with the crew living in quarters about the size of a small apartment.

While their loop past Venus would only last a few hours, they would drop various probes into the planet’s atmosphere and conduct astronomy en route from a large telescope mounted on the S IV-B stage.

In the end, the Apollo Applications Program’s budget was cut along with the rest of the post-Apollo 17 lunar flights, dooming the more exotic mission plans.

But had it been attempted, Apollo’s journey to Venus would have been an amazing - if dangerous - journey.

This article originally appeared in the August 2019 issue of BBC Sky at Night Magazine.

Rod Pyle is the author of 15 space books and Editor-in-Chief of Ad Astramagazine for the National Space Society.