{"id":15406,"date":"2016-06-29T21:03:03","date_gmt":"2016-06-29T13:03:03","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/junos-british-built-engine-readied-for-all-important-firing-at-jupiter\/"},"modified":"2016-06-29T21:03:03","modified_gmt":"2016-06-29T13:03:03","slug":"junos-british-built-engine-readied-for-all-important-firing-at-jupiter","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/junos-british-built-engine-readied-for-all-important-firing-at-jupiter\/","title":{"rendered":"Juno\u2019s British-built engine readied for all-important firing at Jupiter"},"content":{"rendered":"
\"Artist's
Artist\u2019s concept of the Juno spacecraft\u2019s Leros 1b main engine firing. Credit: NASA\/JPL-Caltech<\/figcaption><\/figure>\n

Ground controllers pressurized the Juno spacecraft\u2019s propulsion system Tuesday to prep for a July 4 rocket firing by the probe\u2019s UK-made rocket engine that will steer the spinning, solar-powered robot into orbit around Jupiter.<\/p>\n

Kicking off more than 20 months observing Jupiter\u2019s atmosphere and magnetic field, Juno is poised to become the second spacecraft to ever orbit the solar system\u2019s king planet, and the first since NASA\u2019s Galileo orbiter ended its mission in 2003.<\/p>\n

Juno\u2019s Leros 1b main engine, designed and built by Moog-ISP in Westcott, 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\u2019s success is expected around 11:53 p.m. EDT July 4 (0353 GMT July 5).<\/p>\n

Pointing roughly in Juno\u2019s direction of travel as the spacecraft spins up to 5 rpm, 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\u2019s computer commands propellant valves to open.<\/p>\n

The goal of the burn late Monday is to change Juno\u2019s speed by 1,212 mph (541.7 meters per second), the exact value required for Jupiter\u2019s immense gravity to tug the spacecraft into a looping, oval-shaped 53.5-day orbit.<\/p>\n

Juno will have one shot at the burn as it passes over Jupiter\u2019s north pole and within 2,900 miles (4,667 kilometers) of its swirling, banded cloud tops, nearly 10 times closer than any previous mission.<\/p>\n

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\u2019s project manager at NASA\u2019s Jet Propulsion Laboratory.<\/p>\n

The Leros 1b engine aboard Juno ignited twice in 2012 to adjust the spacecraft\u2019s course, aiming the probe for a flyby of Earth in October 2013, using the planet\u2019s gravity to slingshot toward Jupiter. The engine also briefly fired for a few seconds each year to flush contaminants out of the propulsion system.<\/p>\n

\u201cWe know how to set up the propulsion system,\u201d Nybakken said. \u201cWe know how the engine performs. The only thing new here is how the main engine performs, and the spacecraft performs, in Jupiter\u2019s intense radiation environment.\u201d<\/p>\n

Juno\u2019s 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\u2019s equator.<\/p>\n

The engine design also has a history in interplanetary spaceflight.<\/p>\n

Leros 1b engines successfully steered NASA\u2019s 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.<\/p>\n

\"A
A Leros engine. Credit: Moog-ISP<\/figcaption><\/figure>\n

Ground controllers opened a micrometeoroid shield covering the engine June 20, and engineers planned to warm up Juno\u2019s high-pressure helium tanks Monday before pressurizing the orbiter\u2019s propulsion system Tuesday. A member of Juno\u2019s team confirmed the events occurred as planned.<\/p>\n

Juno switched off its science instruments Wednesday as attention focuses on the July 4 orbit insertion maneuver.<\/p>\n

The spacecraft is scheduled to start its Jupiter arrival sequence Thursday and run on autopilot through next week\u2019s engine burn.<\/p>\n

\u201cIt will be completely hands-off from that point,\u201d said Jeff Lewis, Juno flight operations lead engineer at Lockheed Martin, which built the spacecraft and uplinks commands to the probe at an operations center near Denver.<\/p>\n

It takes 48 minutes for a radio signal to travel one way between Earth and Jupiter, so real-time commanding is impossible.<\/p>\n

\u201cThe spacecraft has to be pretty smart and pretty autonomous,\u201d Lewis said. \u201cThere\u2019s a lot of on-board fault detection, so it can detect faults and take care of itself.\u201d<\/p>\n

Without a successful insertion burn, there is no mission, so software engineers programmed Juno to do away with much of its conservative safety logic just for the July 4 arrival. If something fails or radiation zaps an electronic component, Juno will attempt to reboot and immediately resume the engine firing instead of going into safe mode and radioing Earth for help.<\/p>\n

The so-called \u201cauto restart\u201d feature is a safeguard against the potential of a relatively minor fault ruining the mission, Nybakken said.<\/p>\n

\u201cFor instance, if the radiation causes the computer to reset and the engine stops, it\u2019s not designed to just protect the spacecraft,\u201d Nybakken said. \u201cIt\u2019s designed, for this one portion of the mission, to restart the burn.\u201d<\/p>\n

Juno\u2019s on-board navigation is also smart enough to tweak the duration of the burn as it happens, incorporating data on the engine\u2019s mixture ratio and performance, Lewis said.<\/p>\n

Even if the navigation system runs into trouble, he said, Juno\u2019s computer has a timer to turn off the engine at a prescribed time to ensure the burn does not run long.<\/p>\n

But Juno is going into an unexplored realm, with its entire $1.1 billion mission riding on the outcome of Monday\u2019s maneuver.<\/p>\n

Juno will brush by Jupiter\u2019s dangerous radiation belts on the way in Monday, with its most sensitive electronics wrapped inside a titanium vault designed to repel most impacts by high-energy particles that could damage the orbiter\u2019s computers.<\/p>\n

\u201cWe go in sort of like a dive bomber,\u201d said Scott Bolton, an astrophysicist at the Southwest Research Institute who leads Juno\u2019s science team. \u201cWe go in really fast and get out fast. That speed itself is really hazardous, and we\u2019re also spinning. We\u2019re this giant solar array spacecraft cartwheeling through this incredible magnetic field and radiation belt, so it\u2019s a little bit scary.\u201d<\/p>\n

Juno will repeat its close-up encounters with Jupiter, called \u201cperijoves\u201d by orbital dynamicists, 36 more times before it plunges into the planet\u2019s atmosphere for a destructive finale in February 2018. On each flyby, Juno will collect data on Jupiter\u2019s magnetic and gravity fields, investigate the planet\u2019s enigmatic interior, and take pictures, all while subjecting itself to the solar system\u2019s most dangerous environment outside the sun.<\/p>\n

But the July 4 arrival carries even more risk with the whole mission at stake.<\/p>\n

\u201cI think the Jupiter Orbit Insertion is the second highest risk (of the mission, after launch),\u201d Bolton said. \u201cEverything is riding on it. This spacecraft is very complex. This was a great challenge. We are going literally where no one has gone before.\u201d<\/p>\n

Email the author.<\/i><\/b><\/p>\n

Follow Stephen Clark on Twitter: @StephenClark1.<\/strong><\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

Artist\u2019s concept of the Juno spacecraft\u2019s Leros 1b main engine firing. Credit: NASA\/JPL-Caltech Ground controllers pressurized the Juno spacecraft\u2019s propulsion system Tuesday to prep for a July 4 rocket firing by the probe\u2019s UK-made rocket engine that will steer the spinning, solar-powered robot into orbit around Jupiter. Kicking off more than 20 months observing Jupiter\u2019s […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[1183,1929,1606,472,2907,1561,2612,1620],"class_list":["post-15406","post","type-post","status-publish","format-standard","hentry","category-news","tag-jet-propulsion-laboratory","tag-juno","tag-jupiter","tag-lockheed-martin","tag-moog","tag-planetary-science","tag-swri","tag-united-kingdom"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/15406"}],"collection":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/comments?post=15406"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/15406\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=15406"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=15406"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=15406"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}