1978: A Space Odyssey

In 1972, the last Apollo lunar mission left the moon (that would be Apollo 17 if you believe Tom Hanks or Apollo 18 if you prefer alien attacks to facts). Since then, we've put a couple space stations in orbit, launched 135 space shuttle missions, and now humans even have a pet robot the size of a pickup truck living on Mars!

President Obama on the phone to JPL, discussing America's pet robot.
Source: JPL.

Which is all really awesome- and I am so excited to follow Curiosity's progress as it explores! But... don't you wish it was actual people who landed on Mars last weekend? How great would that have been?

Curiosity- our very own UFO over Mars!
Source: NASA.

It turns out, we came pretty close to launching a manned mission to Mars and Venus soon after the Apollo lunar program ended- back in the late 1970s!

Illustration of a test of Apollo hardware, for a manned Venus mission.
Source: Wikipedia.

There were a few different proposals for how the mission could have proceeded. The easiest, simplest idea was a manned flyby of Venus, spending four months to travel there, zipping by the planet less than 2,000 miles above its surface, and then spending four months travelling back to Earth. 

The most ambitious idea was for a triple-planet flyby: 

- Leave Earth orbit on November 28, 1978.

- Fly by equatorial Venus, on the "day" side of the planet, on May 11, 1979.

- Fly by Mars on November 25, 1979.

- Fly by southern Venus, passing from "day" into "night" on January 29, 1980.

- Land on Earth on January 31, 1981.

The four astronauts in the crew would observe Mars and Venus as they passed by, releasing weather balloons to travel into Venus's atmosphere, and launching a swarm of probes to land on Mars.The entire mission would last 800 days. For comparison, there's one human, Cosmonaut Sergei Krikalev, who has spent over 800 days in space. But it wasn't all at the same time- he flew six different missions. The record for the single longest duration spaceflight is held by Cosmonaut Valeri Polyakov, who lived on the Mir Space Station for over 437 days.

But, using existing 1970s (or for that matter, 2012) propulsion technology, an 800 day trip would be necessary.

The mission profile for a triple-planet flyby, launching in 1978.
Source: Wired Science.

During a November 1978 launch window the three planets would have been aligned for relatively quick and low-energy flybys. So when the manned triple-planet flyby was cancelled, NASA took advantage of this fortuitous alignment of the planets to launch Pioneer Venus 1 and Pioneer Venus 2 instead. NASA also launched a manned space station, Skylab, using much of the Apollo technology and drawing on ideas that would have been applied to the manned triple-planet flyby.

Skylab, as viewed by a Skylab Command and Service Module.
Source: Wikipedia.

The triple-planet flyby spacecraft would have relied on Apollo technology as much as possible, along with new technology being developed for the space shuttle. One plan envisioned a Saturn V rocket (scaled up slightly) being used to launch modules into orbit 25,000 miles above Earth, to be assembled into the triple-planet flyby spacecraft. The spacecraft's operations would be powered mainly by solar panels, like Skylab was; or radioisotopes, depending on the mission duration. The spacecraft itself would be propelled towards Venus using a rocket design based on a Saturn V. Then, a rocket like that found on the Apollo command module would be used for course corrections. Once the spacecraft left Earth orbit, that command module engine would be the only propellant needed: Sir Isaac Newton takes care of the rest, slingshoting the craft from planet to planet.

Here's a mock-up of the spacecraft.

The manned triple-flyby spacecraft.
Source: Wired Science.

(A) are the "radioisotope power supply systems," which deploy outside the body of the craft after the craft arrives in Earth orbit. 

(B) is the vehicle used to re-enter Earth's atmosphere at the end of the mission (the cone on top is similar to the Apollo Command Module; attached to that is a craft similar to the Apollo service module). 

(C) is an access tunnel between the living quarters of the space ship and the re-entry vehicle and the pressurized space around it. 

(D) is the main crew quarters (located as far away as possible from the radioisotope power supply).

(E) is an emergency shelter, with radiation shielding, in the crew compartment. It would be used to protect astronauts during solar flares. The walls of the emergency shelter would consist of the crew's water supply. 

(F) is a two-man centrifuge. Engineers considered equipping the entire craft with artificial gravity (by rotating all or part of the craft) but instead, to save weight, there's just the small centrifuge.

A manned probe above Mars: what could have been and could still be!
Source: Wired Science.

The spacecraft and potential mission plans were pretty well planned out. If you'd like to read more about them, David Portree's Wired Science article After EMPIRE: Using Apollo Hardware to Explore Venus and Mars is a fascinating source. He also wrote an interesting article on NASA plans to use space shuttle hardware for a 1990s Mars mission.

Why didn't the plans for a manned Mars and Venus flyby become reality? A few different factors, including the tragic Apollo 1 fire, slowed the Apollo program down to the point where funding for such a large-scale project became unlikely. The energy spent planning the manned flyby was probably also in large part a response to fears that the USSR might try to make a manned Venus or Mars flight before the U.S. could. This of course did not come to pass. Too bad, right?

Oh well. At least there's this guy:

Curiosity, hanging out all by himself on Mars.
Source: Universe Today.

Eventually, he'll have some more friends on Mars!

Sources: Wired Science; more Wired Science; even more Wired Science; Wikipedia; JPL; Vintage Space.