With a total of seven spacecraft currently operating in orbit and on the surface of Mars today, it seems hard to believe that just a half a century ago we had yet to even reach our much-studied neighbor. It was not for lack of trying, however. In the atmosphere of Cold War competition with the United States, the Soviet Union had attempted to send a pair of flyby probes to Mars in the fall of 1960 only to have them succumb to launch vehicle failures (see “The First Mars Mission Attempts“). Another flyby probe and the first ever Mars lander also fell prey to rocket issues during the next launch window in the fall of 1962. Only the Soviet Mars 1 survived launch to fail 142 days into a 230-day flight due to issues caused by an attitude control malfunction (see “You Can’t Fail Unless You Try: The Soviet Venus & Mars Missions of 1962“). But as the 1964 launch opportunity to Mars approached, the United States was finally ready to join the race to reach Mars.

The Mariner-Mars 1964 Project

The Mariner-Mars 1964 project was officially approved by NASA in early November 1962 – over a month before NASA’s first interplanetary spacecraft, Mariner 2, successfully encountered Venus on December 14 as part of the earlier Mariner-Venus 1962 project. While originally NASA wished to send advanced one-ton spacecraft to Mars using the Atlas-Centaur launch vehicle, the Centaur’s continuing development issues meant that it would not be available for the 1964 Mars launch window. Just as they did with the Mariner-Venus missions, NASA would instead be forced to rely on a much lighter weight spacecraft originally derived from the Ranger lunar spacecraft bus (see “The Prototype That Conquered the Solar System“). Like the Ranger and earlier Mariner-Venus spacecraft, the Mariner-Mars spacecraft would be the responsibility of Caltech’s Jet Propulsion Laboratory (JPL) in Pasadena, California.

For the Mariner-Mars 1964 project, NASA decided to launch a pair a spacecraft, designated Mariner C and D, to perform observations of Mars during a flyby including securing the first close up images of its surface. Launching a pair of spacecraft like they had done for the 1962 Venus opportunity provided some measure of insurance against launch vehicle or spacecraft failures to improve the chances that at least one Mariner spacecraft would survive to encounter Mars. Unfortunately, reaching Mars would be much more difficult than Venus. The flight to Mars would be over twice as long requiring much higher system reliability. The greater distance from the Earth and Sun at the time of the encounter meant that a more powerful communication system and larger solar panels would be required. In addition, the surface imaging experiment coupled with the longer distances traveled tightened the navigation accuracy requirements making it necessary that a more capable propulsion system be carried for up to two midcourse corrections.

Even with advancements in spacecraft systems design since the Mariner-Venus mission, these requirements pushed the mass of the Mariner-Mars spacecraft up to 261 kilograms. This exceeded the capability of the Atlas-Agena B rocket used to launch the 204-kilogram Mariner 2 by about 45 kilograms for the 1964 Mars launch window. In order to get the needed performance, the General Dynamics Atlas D would be mated with a modified version of the improved Agena D built by Lockheed Space and Missile Company (which, after decades of corporate mergers, is now part of the aerospace giant Lockheed Martin along with what was General Dynamics Space Systems Division). This would be the first time NASA would use the Atlas-Agena D for one of its missions. Responsibility for the launch vehicle was given to NASA’s Lewis Research Center (LeRC) located outside Cleveland, Ohio (now named the Glenn Research Center after Ohio-native, John Glenn).

Since the Ranger-style nose shroud used by Mariner 2 was too small to accommodate the Mariner C and D spacecraft with their larger solar panels and altered antenna configuration, a new and larger shroud was required. Even before the inception of the Mariner-Mars 1964 project, NASA was already studying a new unified shroud design for its Agena-based missions called UNIPAC. The lightweight fiberglass UNIPAC shroud concept was designed to encapsulate the payload in a contamination-free environment for prelaunch integration with its rocket and testing. Separation of the shroud during ascent would be accomplished by using pyrotechnic charges to split the shroud in half along its longitudinal axis with internal jets at the nose opening the severed halves. After extensive testing and study, Lockheed with the consent of LeRC decided in November 1963 to use a modified UNIPAC shroud design that employed an “over-the-nose” configuration instead of a simple clamshell. The shroud would now be a one-piece fiberglass-and-magnesium section connected to a beryllium nose dome with a spring cartridge system replacing the originally proposed pyrotechnic segmentation system for shroud ejection.

Launching Mariner 3

Because of the characteristics of the 1964 Mars opportunity, mission constraints and the limitations of even the more capable Atlas-Agena D, Mariner’s launch window to Mars lasted only about 27 days from November 4 to 30. This was much shorter than the 50-day launch window available to the Mariner-Venus 1962 mission which was able to use a single launch pad to send both Mariner 1 and 2 on their way. Given that it typically took about 21 days to refurbish an Atlas launch pad and erect a second rocket, two launch pads would have to be used to improve the chances of getting both Mars-bound spacecraft off the ground in the time available. Launch Complex 12 and 13 at Cape Kennedy were chosen to support the Mariner-Mars 1964 launches. LC-12 was a NASA launch pad but it needed to be modified to support the Atlas-Agena D then reconfigured after the Mariner launch to continue supporting the Agena B for missions such as the upcoming Ranger 8 lunar probe. LC-13 was a USAF facility that was already configured to support the Agena D but would require some modifications to support the Mariner payload just as LC-12 would.

For the first attempt, Mariner C, Atlas 289D and Agena 6931 would launch spacecraft serial number MC-2. Of the two designated pads, LC-13 was available first after the multi-satellite launch of the second pair of Vela satellites and the last TRS Mk. II nanosatellite on July 17, 1964 (see “Vintage Micro: The Original Picosatellite”). Erection of the rocket at LC-13 and other launch preparations began on August 17 after the required pad modifications had been made and tested. The launch of Mariner D would use Atlas 288D and Agena 6932 to send spacecraft MC-3 to Mars from LC-12. The last missions from this pad included the successful Ranger 7 launched on July 28 (see “The Mission of Ranger 7”) and the Orbiting Geophysical Observatory launched on September 4. Installation of Mariner D’s launch vehicle and other launch preparations started on September 28 after two months of pad modifications and testing.

After a successful simulated launch on November 2 and passing on the first day of the launch window to attend to some last minute hardware tests on the Agena D, Mariner C lifted off from LC-13 on November 5, 1964 at 19:22:05 GMT. Mariner 3, as it was now designated, was targeted to follow a Type II trajectory that would reach Mars on July 17, 1965 after a flight of 254 days – the longest interplanetary mission ever attempted up until that time. Even though it would be launched at least eight days later, the plan was that Mariner D would follow a faster Type I trajectory that would be targeted to reach the Red Planet two days earlier on July 15 regardless of its launch date – a choice made to simplify mission planning and the antenna configuration of the Mariner-Mars 1964 spacecraft that had a minimal impact on launch energy requirements for the 1964 Mars window (see “What if Mariner 3 Reached Mars?“).

While the first tracking pass of Mariner 3 an hour after launch indicated that its science instruments were turned on, there were no indications of power coming from the solar panels. In order to buy as much time as possible to attempt corrective action, a command was sent to the spacecraft to turn off the gyros to conserve battery power. Afterwards, telemetry hinted that either the shroud or the Agena D stage had failed to separate from the spacecraft. But after initial tracking revealed that Mariner 3 was traveling 255 meters per second slower than required to reach Mars, it seemed certain that the new shroud had failed to properly jettison and was preventing Mariner 3 from deploying its solar panels.

While the spacecraft had exceeded escape velocity, the velocity shortfall exceeded Mariner’s course correction capability by a significant margin meaning that Mariner 3 would miss Mars by several tens of millions of kilometers. Commands were belatedly sent to the receding spacecraft to jettison the shroud but to no avail. Briefly firing Mariner’s side-mounted course correction engine was also considered to blow off the shroud. Unfortunately, the batteries on Mariner 3 were finally exhausted 8 hours 43 minutes after launch before further action could be taken. The mission was a total loss.

Recovering from Failure

The day after the launch of Mariner 3, JPL engineers suggested that the problem with the new shroud was possibly caused when its skin separated from the honeycomb fiberglass core due to the pressure differential between the unvented core and the exterior. This structural failure would have fouled the separation mechanism preventing the shroud from being jettisoned. As a task team of engineers from JPL, LeRC and Lockheed started their investigation of the shroud failure, an around the clock crash program was immediately started to build and certify an all-metal replacement shroud for Mariner D. Simultaneously, efforts were made to offset the additional weight and drag of the replacement shroud as well as extend the launch window by as much as possible by modifying the Atlas-Agena D launch vehicle. If the required work could not be completed before the quickly approaching end of the 1964 launch window, NASA would be forced to wait over 25 months for the start of the next favorable launch opportunity to Mars at the end of 1966.

On November 8, the engineering task team had verified the failure mode of the fiberglass shroud so that there was now little doubt that this was the cause of the Mariner 3 failure. After an around the clock effort, Lockheed delivered the flight model of the new all-metal shroud to Cape Kennedy on November 22 – just 17 days after the Mariner 3 launch failure. The Mariner D spacecraft with its new shroud was mated to the Atlas-Agena D on November 24 with final tests of the new shroud design satisfactorily completed two days later. Despite the slight decrease in performance as a result of the new shroud, modifications to the launch vehicle had the net effect of increasing the payload capacity of the Atlas 288D/Agena 6932 by 18 kilograms adding about four extra days to the launch window in the process.

Thanks to the efforts of all those involved at NASA, its field centers and contractors, Mariner 4 successfully lifted off from LC-12 on November 28, 1964 at 19:22:01 GMT. The new shroud worked as intended and Mariner 4 was on its way to Mars. Two days later, the Soviet Union launched Zond 2 towards Mars with objectives that have only been fully revealed recently (see “Zond 2: Old Mysteries Solved & New Questions Raised”). While the voyages of Mariner 3 and ultimately Zond 2 ended in failure, Mariner 4 successfully reached Mars on July 15, 1965 returning 21 images of the Martian surface in the days following the encounter (see “Mariner 4 to Mars“). With this success, the exploration of the Red Planet by spacecraft had finally started.

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Related Reading

“Mariner 4 to Mars”, Drew Ex Machina, July 14, 2015 [Post]

“What if Mariner 3 Reached Mars?”, Drew Ex Machina, July 17, 2015 [Post]

“The Prototype That Conquered the Solar System”, Drew Ex Machina, September 15, 2015 [Post]

“Zond 2: Old Mysteries Solved & New Questions Raised”, Drew Ex Machina, July 17, 2014 [Post]

General References

Paolo Ulivi with David M. Harland, Robotic Exploration of the Solar System Part 1: The Golden Age 1957 – 1982, Springer-Praxis, 2007

Mariner-Mars 1964 Scheduled Launch, NASA Press Release, October 29, 1964

Mariner Mars 1964 Project Report: Mission and Spacecraft Development Volume I. From Project Inception Through Midcourse Maneuver, JPL Technical Report No. 32-740, NASA, March 1, 1965

Mariner-Mars 1964 Final Project Report, SP-139, NASA, 1967