A critical moment in NASA'S Juno mission has been postponed while engineers at the Jet Propulsion Laboratory attempt to sort out a mysterious engine issue. If the problem is not resolved quickly, it could reduce the amount of high-quality data the Jupiter-orbiting probe is able to collect during its scientific mission.
On October 19th, at its point of closest approach to Jupiter (called periapsis), the Juno spacecraft was scheduled to perform its final main engine burn, a "period reduction maneuver" that would narrow its orbit from 53.4 days to 2 weeks. Once in its "science orbit," the spacecraft's main data collection phase will commence.
But on Friday, the space agency decided to delay the burn due to an unexpected issue with a pair of helium valves that are part of the engine's fuel pressurization system. As Juno project manager Rick Nybakken said in a news release, these valves "did not operate as expected during a command sequence that was initiated [Thursday]."
"The valves should have opened in a few seconds, but it took several minutes," Nybakken continued. "We need to better understand this issue before moving forward with a burn of the main engine."
http://gizmodo.com/something-went-wrong-with-the-juno-spacecrafts-engine-1787873807
[Source]: NASA
(Score: 3, Informative) by richtopia on Tuesday October 18 2016, @01:02AM
I forget why helium specifically, but pressure fed engines are almost universal for altitude control and orbital maneuvering.
https://en.wikipedia.org/wiki/Pressure-fed_engine [wikipedia.org]