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from the debugging-from-960-million-kilometers-away dept.
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: 2) by TrumpetPower! on Monday October 17 2016, @09:09PM
Now you're significantly eating into your delta-vee budget.
It doesn't matter the environment; the volatile compounds (the vulcanizers in the rubber, for example) will all...well..volatilize.
Manufacture...from what raw materials? And with what energy? Materials manufacture currently takes our entire planetary industrial infrastructure. Were you planning on hauling the whole Earth with you, or maybe some significant fraction thereof?
And, if you're going to have a constant industrial manufacturing enterprise going just to keep the ship from falling apart...well, there goes any energy savings you might have had in mind. A slow trickle over the course of dozens of millennia adds up to as much energy as a furious expenditure over the course of decades.
If you could keep your fission reactor functioning the whole time, it'd provide enough energy to get there fast. But, to get there fast, you need about as much energy as our entire civilization currently uses just for a schoolbus-sized ship...and you're back to a delta-vee problem if you're going to use uranium.
Interstellar travel makes for great space opera, but you really do need unobtanium...and the stuff is called that for a reason.
Cheers,
b&
All but God can prove this sentence true.
(Score: 1) by khallow on Monday October 17 2016, @09:30PM
Now you're significantly eating into your delta-vee budget.
At tens of thousands of years travel time, you have a very small delta-v budget. It's not a significant cost of the trip. In fact, you might be able to get most of your delta-v for the outgoing leg with gravity assists from Jupiter and the other gas giants.
It doesn't matter the environment; the volatile compounds (the vulcanizers in the rubber, for example) will all...well..volatilize.
Assuming the materials have volatile compounds and that you aren't willing to replace the materials somewhat more often as a result. There's a variety of silicone rubbers which wouldn't have that trouble, for example.
And, if you're going to have a constant industrial manufacturing enterprise going just to keep the ship from falling apart...well, there goes any energy savings you might have had in mind. A slow trickle over the course of dozens of millennia adds up to as much energy as a furious expenditure over the course of decades.
You've already mentioned a lot of available power as being a requirement. And once the trip takes longer than a certain amount of time, you are forced to have the ability to replace the components of the ship. Plus, such capabilities would be useful at any destination.
If you could keep your fission reactor functioning the whole time, it'd provide enough energy to get there fast. But, to get there fast, you need about as much energy as our entire civilization currently uses just for a schoolbus-sized ship...and you're back to a delta-vee problem if you're going to use uranium.
A slow trickle over the course of dozens of millennia adds up to as much energy in a furious expenditure over the course of decades.
Interstellar travel makes for great space opera, but you really do need unobtanium...and the stuff is called that for a reason.
It's been about 10,000 years since agriculture started. In that time, the Solar System has traveled a little under 8 light years around the Milky Way which is enough to get to the four closest star systems [wikipedia.org] and almost close enough to get to the fifth closest star system (which would be about 0.1 lightyears further). We are already doing interstellar travel.