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The Mariner program had a number of successes for the U.S. space program, including the first Venus flyby (1962), the first flyby of Mars (1965), the first American Mars orbiter (1971) and for the final mission, Mariner 10 was the first spacecraft to visit Mercury (1974).

While Mariner 10 is still in orbit around the sun, this is an extra build of the propulsion system used for midcourse trajectory correction to make possible the first visit to two planets by a single spacecraft. For Mariner 10 to direct a course to Mercury, after sling-shotting by Venus, its trajectory could deviate no more than 200km (120 mi) from a critical point near Venus. To ensure that the necessary course corrections could be made, mission planners tripled the amount of hydrazine fuel Mariner 10 would carry as compared to the previous Mariner missions. The hydrazine fuel bladder went from a doorknob shape to a sphere (see diagram below).

The Mariner propulsion system for midcourse trajectory correction employed a rocket engine that provided 50 pounds of thrust. The system was suspended within the central portion of the basic hexagonal structure of the spacecraft.

This retro-rocket engine used a type of liquid propellant known as anhydrous hydrazine and it was so delicately controlled that it could burn for as little as ²/₁₀ of a second and increase the velocity of the spacecraft from as little as ⁷/₁₀ of a foot per second to as much as 200 feet per second.

Part of the FV Space Collection.

2 responses to “Mariner 10 Spacecraft Engine”

  1. jurvetson Avatar
    jurvetson

    I finally found a diagram, from Mariner 2, with a smaller fuel bladder. The four side-facing jet vanes set trajectory as the central engine burns: report: "The hydrazine fuel was stored in a rubber bladder inside a doorknob-shaped container. At the ignition command, nitrogen gas under 3,000-pound-per-square-inch pressure was forced into the propellant tank through explosively activated valves. The nitrogen then squeezed the rubber bladder, forcing the hydrazine into the combustion chamber.
    Hydrazine, a monopropellant, requires a starting ignition for proper combustion. In the Mariner system, nitrogen tetroxide starting or “kindling” fluid was injected into the propellant tank by a pressurized cartridge. Aluminum oxide pellets in the tank acted as catalysts to control the speed of combustion of the hydrazine. The burning of the hydrazine was stopped when the flow of nitrogen gas was halted, also by explosively activated valves."

    Mariner 10 composite photo of Mercury (with missing strip blurred out)l from APODFully deployed spacecraftand diagramed, propulsion sphere on center axis, right side and memorialized at JPL, as I noticed on our last visitJPL Flight Projects Center

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  2. jurvetson Avatar
    jurvetson

    as for the photos of Mars, here is a time series:
    * Mariner 4 (1965) first image of Mars (total of 22 images gathered on the first flyby of another planet, but a fleeting glimpse): • Mariner 6&7 (1969). Also a flyby, but twice as close to Mars as Mariner 4:• Mariner 9 (1971) carried the same instrument payload as 6/7 but entered Mars orbit for the first time and gathered 7,329 images from its 11-month orbit:

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