Recently, I received a press release from the American Museum of Natural History on their excellent exhibit about the future of space exploration. I did a quick word search: "Mars" got 14 hits; "asteroid" 12; "moon/lunar" 11; "Europa" and "Jupiter" a total of four. A check of "Venus" came up empty. Considering that all the aforementioned worlds are fascinating and scientifically fecund, our closest planetary neighbor is notable by its absence. I've always had a nagging suspicion that when it came to choosing targets for planetary exploration, Venus has gotten the short shrift over the last two decades—especially from NASA.

So, why not make up for this exclusion by adding our closest planetary neighbor into NASA's destinations for astronauts to visit when their new booster and spacecraft technology comes on line in the coming decades?

You'd think that if planners pitched this preposterous proposition at a NASA mission planning meeting, they'd be ushered out of the room by security posthaste. After all, why would we want to go anywhere near the place? Although Venus is a beautiful orb at a distance, presiding over the horizon as the brilliant morning or evening star, up close and personal it is an environmentally malevolent world. "Hellish" is the word that is usually offered to describe its surface conditions, with pressure at 90 Earth atmospheres and temperatures around 500 degrees Celsius that would melt lead, making short work of even a hardened lander. And if robots fear it, astronauts wouldn't have a prayer. Compared with Venus, Mars looks like a tourist resort—even the harsh environment on the moon or asteroids seems balmy. And then there's that sulfuric acid–laced, CO2 atmosphere and runaway global warming that makes Venus truly a nightmare bizzaro Earth where everything seems upside down and inside out—the sun even rises in the west.

Yet, maybe I'm not so unhinged, or at least I'm in good company: It seems that in the 1960s, during the height of the space race, NASA engineers had made serious inquiries about what it would take to send astronauts to Venus—not to land, but to do a manned flyby.

History of missions, and those that never were

The last dedicated U.S. robotic mission to Venus, Magellan, which orbited from 1990 to 1994, radar-mapped 98 percent of the surface and returned reams of data. Since then there have been only flybys by other NASA probes, which used the Earth-size world for gravity assists and instrument calibration. That is not to say the second rock from the sun has been totally ignored. The European Space Agency currently has stationed Venus Express in orbit at the veiled globe. And from 1967 to 1983 the Soviet Union staged a most ambitious assault on Venus with an armada of orbiters, flybys and landers that sampled the atmosphere and soil and took eerie photos of the surface before meeting their demises from minutes to hours after touching down.

Maybe that's why Venus seems to have become a space exploration pariah, and why I was all the more intrigued when I came across a bland, 177-page typewritten 1967 proposal (pdf) by engineers at Bellcomm, Inc., a joint venture between NASA and AT&T that was dissolved in 1972. Written in dry engineerese, the document laid out the spacecraft specs and trajectories, along with thermal and radiation issues to surmount (such as solar flares, communications, etcetera) in adapting Saturn/Apollo moon hardware for a three-astronaut Venus flyby mission proposed for a launch window in 1973–74. What a boldly optimistic era, when this and even more ambitious proposals, such as a combo flyby of Venus and Mars, were being tossed out—objectives that ring unrealistic to the postmodern ear. But why? Have we become too pragmatic to dream—too abiding of our current technological, political and fiscal limitations?

Proposed steps in reconfiguring Saturn/Apollo lunar transportation system for a long-duration Venus flyby mission. From: Bellcomm, Inc., "Manned Venus Flyby," February 1, 1967; Document number TR-67-600-1-1

Casting aside practical constraints, as one should when ideating, I can't help but wonder if the current hiatus in U.S. manned space missions following the shuttle program renews the opportunity to challenge our limits. We are in a similar situation as that after the December 1972 splashdown of Apollo 17, the last moon mission. Although optimism was more abundant in the 1960s, and we had the hardware and expertise, unfortunately both popular enthusiasm, and with it funding, had already started to evaporate even before Neil Armstrong uttered his famous observation about human perambulation on the lunar surface in 1969, sealing to the public's and politicians' satisfaction our Cold War "victory" in the space race with the Soviet Union.

Today, the political and fiscal situations seem more disheartening. And now we don't even have a homegrown technological ability to get into, let alone beyond, low Earth orbit (LEO). But for better or worse, somehow the financially humbled U.S. has embarked on building a new space transportation system, with intermediate goals left up to NASA on where to go—at least so far. With the exception of a fuzzy, ever more distant future dream date with the Red Planet, closer destinations are still up for grabs. What will it be, then? A flirtation with an asteroid? A reconciliation with the lunar surface? Astronauts stalking the moon from a Lagrangian point beyond its far side?

The future was then

The 1967 report on a Venus flyby and other proposals for manned interplanetary missions came out among a flurry of studies, such as those initiated in the early '60s by NASA's Planetary Joint Action Group (JAG) that prescribed piloted planetary exploration—manned planetary flyby missions that would drop off robotic probes—as the best and most economical way to test spacecraft technology while accomplishing planetary science. JAG blue-skied piloted missions to fly in the 1970s and '80s that envisioned using nuclear-thermal rockets for tandem Mars–Venus flybys, culminating in a Mars landing. The Marshall Space Flight Center's Future Projects Office, and its Apollo Applications program (AAP) also were part of this push. The latter was started in 1965, and is well chronicled in Humans to Mars, written by space historian David Portree (pdf) for NASA's History Office. The AAP was generated by a task force formed by legendary NASA Administrator James Webb in response to a Johnson administration directive to look at ways to reconfigure existing moon hardware for future missions. The assumption was that we would continue building Saturn rockets and Apollo spacecraft to acquire technological and operational experience for long-duration journeys. AAP was eventually subjected to death by a thousand budget cuts by the Johnson and Nixon administrations, and finally whittled down into the Skylab program—America's first space station.

So by 1970 Venus—or anywhere outside of LEO—was out of the question, even in those supposedly heady, well-funded days of space exploration. In actuality those times were also plagued by growing budget deficits, tunnel-visioned bureaucrats, provincially minded politicians and a populace rightfully concerned with joblessness and inflation, social upheaval and ongoing hot and cold wars. All that relegated 1970s America to diminished expectations as it slouched into low orbit on the hefty shoulders of the space shuttle. No doubt, the ideal was still intact: All roads for space exploration eventually led to the hardest place, a landing on Mars—albeit in the safely distant future. And here we are more than 40 years later, in roughly the same situation.

But among all the gloomy prospects, the current situation may offer an opportunity. After the Obama administration scrapped the preceding administration's Constellation program and the next-generation rockets that were to power it, NASA was ordered by Congress, for good or for bad, and mostly for local contracts and jobs (not necessarily all bad in a recession), to fast-track the development of the Space Launch System (SLS), which ordains a heavy-lift rocket reminiscent of the Saturn 5 and salvages technology from Constellation and the shuttle. So again, like the 1960s, it is technology, exploration and science following politics, but this time without a specific goal and deadline set by the president—a mandate that fostered a more logical approach implementing major next-generational designs developed for specific requirements. With SLS, as bizarre as it is to legally ordain such specs rather than let them evolve, the U.S. will get heavy-lift capability: Early SLS boosters will lob 70 to 100 tons into orbit, and later versions will carry around 130 tons—around the same tonnage as the now legendary Saturn 5.

So, if the U.S. is "stuck" with the SLS, along with a six-person Orion crew capsule that itself recapitulates Apollo, but in venti size, maybe we should start thinking like it's 1967 and ponder all the places we could send its payloads. Judging from the AAP studies, which adapted Apollo/Saturn components to Venus and Mars missions, couldn't NASA engineers also rig this neo–Apollo era technology for similar ends?

The AAP proposals, some of which are documented in Portree's very thorough blog Beyond Apollo, ranged from a "simple" Venus flyby mission lasting 359 days to a much more ambitious Mars–Venus flyby, which would have the Red Planet as its goal and use a Venus's gravity to speed the mission there or back. Various configurations were considered. The Bellcomm plan, which has been roughly animated as a YouTube facsimile employed the Saturn 5 third stage both as an Apollo capsule booster and as a habitation module, which would replace the lunar lander. The ingenious part was that after the third stage had expended its fuel, its tanks would become a space station–type module to support the three-astronaut crew. Using a spent stage in this manner was the basis for Skylab, but with the difference that the fuel tank was outfitted on the ground and launched as a payload, not as an active booster. In the Venus scheme, the astronauts would have to leach the remaining fuel from the tanks after being boosted toward Venus, and set up housekeeping en route during the outbound trip. And if such a crew-sustaining system worked, it might be adaptable for a Mars orbital or landing mission.

Life expectancy grim?

Of course, life is the holy grail of solar system exploration—and the general rule is: follow the water and, hopefully, that is where critters or their fossils will turn up. And the odds are that dry Venus is a dead—and deadly—world. But then, so are the moon and asteroids. Of course, the surfaces of the latter two can be visited; not so easy for Venus. But even from above, it is a far more dynamic place—the closest place to Earth with a significant atmosphere and geology that challenges our perceptions about how volcanism, plate tectonics, climate and weather work on our home world. Those factors are not insignificant, given Venus's evolution from what is thought to have been a more Earth-like world into an atmospheric hothouse, which may as well serve as a cautionary vision of our own planet's potential climatic destiny—albeit far more extreme, as is everything on our tempestuous sister world.

And according to planetary scientist David Grinspoon in his book Venus Revealed, we should not be so quick to dismiss the Second Planet as a candidate for extraterrestrial life, even if it doesn't fit the somewhat limited current definition of life as carbon- and water-based. Although Venus is dry, with its active geology and atmosphere as well as signatures of chemical activity, it dares one to ask: Is it possible that some type of alien organic chemistry is part of the mix, affecting it as carbon-based life alters Earth's atmospheric systems? Pitted against Mars, and the even more distant Europa or Titan—the latter two also with extreme environments challenging to robotic spacecraft—nearby Venus is just as enigmatic. Although it may look like a long-shot for organics and life, there is much planetary science to offer, and no doubt plenty of surprises that will challenge our preconceptions—and it's all up for grabs in our inner planetary neighborhood.

But if we can't land there, why go at all?

NASA is now set to reestablish its deep-space capability in concert with 11 other national space agencies. There are nonbinding plans that lay out goals projected in the Global Exploration Roadmap. The document, published in September 2011, depicts a long-range framework to coordinate the space agencies' development of technology based on two scenarios that prioritize goals, both culminating in human bootprints on Martian soil: Asteroid Next and Moon Next. Each also adds a spacehab at the gravitationally stable Lagrange points 1 or 2 (L1 or L2), either between Earth and the moon, or beyond the moon looking down on its far side, where astronauts could learn about functioning in a deep-space environment without being too far from home.

But as the SLS/Orion hardware comes online, why limit ourselves as we take on this stepwise assault on the solar system? Why not, if we are on the cusp of taking another leap out of LEO, use this second opportunity to expand our set of objectives and consider all the destinations in our neighborhood by adding Venus into the mix as a candidate for a flyby or even an orbital manned mission?

This would be a logical next step after an asteroid mission. A "quick" trip to a near-Earth asteroid (NEA) could take no more than 90 days and keep astronauts a few lunar distances from Earth. Another possibility in 2020 is a roundtrip to a NEA lasting around 170 days. The Venus flyby would be at least twice as long, but still shorter than NASA's shortest-duration scenario for a round-trip to the Red Planet lasting 545 days, with only a short stay on the surface. Also, asteroids are elusive targets. Should we miss a launch window to a particular asteroid, the next may not arise for years. Venus, with its very circular orbit, keeps a regular schedule—we always know where it will be.

Within this time frame, after trips either to the moon, an asteroid or L2, or any combination thereof, to develop the transportation, habitation and landing systems, the next step would be Mars. But to go there, it will still be a giant leap—and landing on Mars is completely different from landing on the moon—or any other intermediate destination. As this landing technology is developed, a step could be inserted to test the transportation and habitation systems on a long journey à la Apollo 8—the first manned mission to orbit the moon and a major test for the Apollo spacecraft and crew before the lunar lander was ready.

A circumnavigation of Venus would test our ability to function in deep space, to enter a planet's gravitational influence, to create robust shielding for the higher radiation at Venus's relatively close proximity to the sun, to devise zero-g strategies for long-duration flights—all of which would bolster us for an even longer journey to Mars. Besides, for a long-duration mission, we might not want to commit our astronauts to landing on Mars only to find out that they could not walk, their musculature had so degenerated upon arrival. In contrast, the crew of a long Venus round-trip would land not on a faraway planet but back on Earth, where medical attention is readily available if needed. A flyby or orbital mission to Venus could also carry scientific instrumentation, much the way the orbiting Apollo spacecraft did during later flights to the moon

Such a flight could take advantage of the 130-ton payload iteration of the SLS to boost a crew module into orbit, complete with radiation shielding and supplies, along with an Orion spacecraft. Or it could adapt the 1967 plan—using the Saturn third stage as a habitation module—to the new SLS upper stage. There are many variables, but some round-trip flybys using so-called Hohmann transfer orbits could take as little as six months if enough propulsive energy is available. Here, I turn over the orbital mechanics to the engineers (pdf); the 1967 plan put the mission at 359 days. (Counterintuitively, due to the vagaries of orbital mechanics some trips to closer bodies take longer than those to farther ones. This is especially true of asteroids with their irregular orbits.)

One touch of Venus

Although a fleeting visit at Venus would not give astronauts enough observational time to reap a scientific bonanza, they could deploy robotic landers and orbiters as they swung around. The real bonus, however, would be experiential—both as a technological test-bed and by pushing the boundaries of human exploration in a systematic advance into the inner solar system. By employing a more flexible, incremental path for NASA's exploration plans, and adding this intermediate step that culminates in an eventual touchdown on Mars, we would not only gain valuable experience and technical know-how that will apply to a Martian visit but also open the way for further human exploration of the inner solar system. This could include orbital missions and, further in the future, flights that use the second planet for gravity-assisted missions to Mars, the asteroids and possibly even farther destinations. Finally, such an adventure could ignite the public's imagination, increase confidence in our spacefaring ability, and further solar system science, simultaneously serving as a dry run for our ultimate adventure—a mission to the Red Planet.

So if neither then nor now turns out to be a good time to get going on serious deep-space manned exploration that comprehensively covers all the places to go in the inner solar system, when will be a good time? Any great civilization is one that can multitask both crisis and progress. So it's on to the moon, asteroids and Mars—but why not Venus, too?