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Juno’s British-built engine readied for all-important firing at Jupiter

Artist's concept of the Juno spacecraft's Leros 1b main engine firing. Credit: NASA/JPL-Caltech
Artist’s concept of the Juno spacecraft’s Leros 1b main engine firing. Credit: NASA/JPL-Caltech

Ground controllers pressurized the Juno spacecraft’s propulsion system Tuesday to prep for a July 4 rocket firing by the probe’s UK-made rocket engine that will steer the spinning, solar-powered robot into orbit around Jupiter.

Kicking off more than 20 months observing Jupiter’s atmosphere and magnetic field, Juno is poised to become the second spacecraft to ever orbit the solar system’s king planet, and the first since NASA’s Galileo orbiter ended its mission in 2003.

Juno’s Leros 1b main engine, designed and built by Moog UK Westcott Ltd. in Buckinghamshire, is gearing up for a make-or-break 35-minute firing to steer the spacecraft into a wide multi-million mile ellipse around Jupiter. Confirmation of the burn’s success is expected around 11:53 p.m. EDT Monday (0353 GMT Tuesday).

Pointing roughly in Juno’s direction of travel, the engine will produce 145 pounds of thrust and consume a mix of hydrazine and nitrogen tetroxide. The toxic chemicals spontaneously combust when contacting each other, permitting the engine to generate thrust when Juno’s computer commands propellant valves to open.

The goal of the burn late Monday is to change Juno’s speed by 1,212 mph (541.7 meters per second), the exact value required for Jupiter’s immense gravity to tug the spacecraft into a looping, oval-shaped 53.5-day orbit.

Juno will have one shot at the burn.

Engineers calculated the engine must fire at least 20 minutes or so for Juno to be captured into any orbit around Jupiter, and 35 minutes to reach the targeted trajectory, according to Rick Nybakken, the mission’s project manager at NASA’s Jet Propulsion Laboratory.

The Leros 1b engine aboard Juno ignited twice in 2012 to adjust the spacecraft’s trajectory, aiming the probe for a flyby of Earth in October 2013, using the planet’s gravity to slingshot toward Jupiter. The engine also briefly fired for a few seconds each year to flush contaminants out of the propulsion system.

“We know how to set up the propulsion system,” Nybakken said. “We know how the engine performs. The only thing new here is how the main engine performs, and the spacecraft performs, in Jupiter’s intense radiation environment.”

Juno’s single main engine is similar to liquid-fueled orbit-raising thrusters flown on many communications satellites. More than 70 Leros engines have flown in space, and most of them boosted telecom platforms from elliptical post-launch drop-off orbits to their final operating stations in geostationary orbit more than 22,000 miles (about 35,786 kilometers) above Earth’s equator.

The engine design also has a past in interplanetary spaceflight.

Leros 1b engines successfully steered NASA’s Messenger mission into orbit around Mercury in 2011, helped get the Mars Global Surveyor and Mars Odyssey orbiters to the red planet, and flew on the NEAR Shoemaker spacecraft that became the first probe to orbit and land on an asteroid.

Ground controllers opened a micrometeoroid shield covering the engine June 20, and engineers planned to warm up Juno’s high-pressure helium tanks Monday before pressurizing the orbiter’s propulsion system Tuesday. A member of Juno’s team confirmed the events occurred as planned.

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Follow Stephen Clark on Twitter: @StephenClark1.

Source: You’ll find lots of information about the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Also we have facts about the space station, ISS, SpaceX launch, space program, and outerspace. Space Flight

Juno’s British-built engine readied for all-important firing at Jupiter

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