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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: 4, Interesting) by TrumpetPower! on Monday October 17 2016, @07:23PM
It's taken as gospel amongst the geek crowd that a surefire way to get to the stars is to build a sleeper ship that'll coast between the stars for tens or hundreds of thousands of years before waking up the passengers at their distant destination.
Sure, the plot line generally includes stuff breaking down in interesting ways...but the reality is that we can't build stuff that can wake up reliably after a few mere decades...and, at the types of longer-than-civilization-has-existed sorts of timespans for interstellar travel, even your welded-shut steel gas canisters will have leaked all their contents, and all rubber and plastic will have long since decayed into dust. And the atoms in your electronic circuits will have entropically migrated throughout the chips, resulting not in neat city-like circuits but simple unstructured silicon crystals with metallic impurities. Not to mention, your radioisotopic energy sources have decayed to the point of not having any more usable energy (whilst having destroyed their containers from radiation), and your fusion-based sources have run out or leaked out of their containers.
I'll gladly bet a cup of coffee that the JPL crowd will figure out a way to get lots of great science out of Juno. They're a creative and dedicated lot and more than smart enough to build all sorts of flexibility into their plans.
But where's your JPL ten thousand years from now to save your sleeper ship, with a years-long round-trip communication lag? No human institution has survived anywhere near that long, and the closest analogues, extant ancient religions, are radically different from their ancestors.
Cheers,
b&
All but God can prove this sentence true.
(Score: 1) by khallow on Monday October 17 2016, @08:27PM
but the reality is that we can't build stuff that can wake up reliably after a few mere decades...
Yet.
even your welded-shut steel gas canisters will have leaked all their contents
Unless you made the walls of the canisters thicker.
and all rubber and plastic will have long since decayed into dust
Unless they aren't exposed to UV or a reducing atmosphere for all that time. And you can always manufacture more such when the old ones no longer are sound.
And the atoms in your electronic circuits will have entropically migrated throughout the chips
Unless, you've been replacing the circuits with newly manufactured circuits, every few centuries, whether they need it or not.
Not to mention, your radioisotopic energy sources have decayed to the point of not having any more usable energy (whilst having destroyed their containers from radiation), and your fusion-based sources have run out or leaked out of their containers.
Unless of course, the half life is on the order of the trip duration or you use regular style fission reactors (half life of U235 is 700 million years, for example).
But where's your JPL ten thousand years from now to save your sleeper ship, with a years-long round-trip communication lag? No human institution has survived anywhere near that long, and the closest analogues, extant ancient religions, are radically different from their ancestors.
Or humans could figure out how to live tens of thousands of years. That would work as well.
(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.
(Score: 2) by jimtheowl on Tuesday October 18 2016, @01:19AM
Marvin:
.. thanks to the silly little errands your organic life forms keep sending me through time.. (I am now) thirty-seven times older than the Universe itself..
Do you remember, the first time you ever met me? .. I mentioned to you that I had this terrible pain in all the diodes down my left side? That I had asked for them to be replaced but they never were?
See if you can guess which parts of me were never replaced?
Go on, see if you can guess...
- Douglas Adams - Hitchhiker's Guide to the Galaxy
(Score: 2) by takyon on Monday October 17 2016, @09:08PM
I was gonna poo in your general direction, but honestly, let's just wait until January 2017. Because by then, emdrive may be anointed or broken (a peer-reviewed paper will be published in December).
Then there's this:
http://www.zmescience.com/science/news-science/second-generation-em-drive-just-around-corner-patent-made-public-friday/ [zmescience.com]
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 1, Informative) by Anonymous Coward on Monday October 17 2016, @09:50PM
The EM Drive again, huh? That's always good for a laugh. Your link is actually related to your first sentence: version 2 is coming out because he's suckered as many as he can get with version 1.
The statements from your link are interesting:
Those are, charitably, misleading, or outright wrong. Churn a lot of thrust? There isn't enough to convince a reasonable person that they are over the noise limit. If real propulsion scientists and engineers can measure thrust, not the C-team at "Eagleworks", but the guys who do it for real, then we can start talking about this as something interesting. Right now it is cold fusion level of science., except that cold fusion at least has a physical basis for it.
(Score: 2) by takyon on Monday October 17 2016, @10:19PM
Just look at the paper when it comes out in December.
I think some of the findings of the December paper leaked out, but I will wait until its actual release to care. The paper could be revised by then.
The quoted portion is just bad reporting. The original source for the 2.0 article is IB Times UK [ibtimes.co.uk] (and the patent application). Unfortunately, we have to take Roger Shawyer's word for it that governments are actually (still) interested in emdrive. He appears to have "suckered" in a legit company at least:
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 1) by khallow on Tuesday October 18 2016, @03:05PM
(Score: 2) by jimtheowl on Tuesday October 18 2016, @02:00AM
(Score: 0) by Anonymous Coward on Tuesday October 18 2016, @04:40PM
"They laughed at Columbus, they laughed at Fulton, they laughed at the Wright brothers. But they also laughed at Bozo the Clown." -- Carl Sagan, Broca's Brain
(Score: 0) by Anonymous Coward on Tuesday October 18 2016, @04:35PM
Solution = maintenance. You have a crew, use them to fix and re-manufacture stuff. However, the ship will probably have to stop for supplies and fuel since maintenance requires more energy.