James Webb Telescope

Ziggurat said:
Nonsense. They originally said the mission might only last for 5 years, and now they're saying it might last up to 20. That's a terribly inaccurate prediction, and proves that they're garbage at their jobs.
:duck:
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I know you’re joking, but how did this actually come to be? I assume the lifetime is mostly based on fuel available for station keeping? Was the initial 5-year lifetime based on worst-case (or even probable-case) scenarios and they’ve just over-performed every step of the way?
 
Senor_Pointy said:
I know you’re joking, but how did this actually come to be? I assume the lifetime is mostly based on fuel available for station keeping? Was the initial 5-year lifetime based on worst-case (or even probable-case) scenarios and they’ve just over-performed every step of the way?
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Pretty much. In cases like this I suspect everyone looks to under promise and over deliver.

Part of it is down to the incredible accuracy of the launch vehicle.

https://i.redd.it/9uynjtjms2881.jpg
 
Senor_Pointy said:
I know you’re joking, but how did this actually come to be? I assume the lifetime is mostly based on fuel available for station keeping? Was the initial 5-year lifetime based on worst-case (or even probable-case) scenarios and they’ve just over-performed every step of the way?
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3point14 said:
Pretty much. In cases like this I suspect everyone looks to under promise and over deliver.

Part of it is down to the incredible accuracy of the launch vehicle.

https://i.redd.it/9uynjtjms2881.jpg
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Both are correct. There is another, less considered reason.

Spacecraft are built to specifications. If the SC is specified to last for 20 years, it is almost impossible to prove you have met that requirement before delivering the SC. Five years is more reasonable. No one could afford a spacecraft that is actually specified to last 20 years.
 
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So, Dr. Becky mentions that there have actually been not just one but 5 micrometeor impacts so far. Basically one per month. Over time, the damage could add up.

And, not to derail, but I makes me think about the difficulty of even a mission to Mars, much less interstellar travel.

In science fiction, it's a problem that is just ignored for the most part. But these little dust or sand-sized particles could make travel between stars impossible from a practical standpoint. After all, if you want to get there in less than 10,000 years or so, you would need to travel at a significant fraction of the speed of light, but could any spaceship even survive that, or would it be ablated (eroded) away en route? Would it still be functional when it arrives? Or would it be shot through with tiny bullet holes? This could be the reason for the Fermi "paradox". That is, even highly advanced intelligent civilizations are incapable of traveling between stars, because it's impossible from a practical standpoint. Like trying to swim across an ocean that's 1000 times wider than the Pacific. Theoretically possible, but not practically possible.
 
Puppycow said:
So, Dr. Becky mentions that there have actually been not just one but 5 micrometeor impacts so far. Basically one per month. Over time, the damage could add up.

And, not to derail, but I makes me think about the difficulty of even a mission to Mars, much less interstellar travel.

In science fiction, it's a problem that is just ignored for the most part. But these little dust or sand-sized particles could make travel between stars impossible from a practical standpoint.

..snip...
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Historically that's not been the case, there was at one time a bit of a push back at all these spacecrafts that get a micro puncture or worse, even in trips to Mars like for example Clarke's "The Sands of Mars" published early in the 1950s.
 
Darat said:
Historically that's not been the case, there was at one time a bit of a push back at all these spacecrafts that get a micro puncture or worse, even in trips to Mars like for example Clarke's "The Sands of Mars" published early in the 1950s.
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OK, I guess I stand corrected, but I think the problem still remains a problem.
 
Puppycow said:
OK, I guess I stand corrected, but I think the problem still remains a problem.
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Oh it is a genuine problem and one that would have to be accounted for in any missions to Mars we plan.

Space experiments really do push our engineering skills to a maximum. It's part of why they cost so damn much and take so long to plan and then execute.
 
I never heard the hubble mirror being injured by these granules, yet it is a sure thing. What is the difference?
 
Samson said:
I never heard the hubble mirror being injured by these granules, yet it is a sure thing. What is the difference?
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1. Hubble is in Low Earth Orbit (LEO).
2. Hubble has a flap over the entrance to the mirror that can be closed.
3. That tube makes it less likely a micrometeoroid will enter the tube and hit the mirror. Hubble would have to be pointed directly at it.

That said, we know the solar arrays have been bombarded with hundreds/thousands of micrometeoroids. Hubble also has to worry about more space debris than Webb.
 
Puppycow said:
So, Dr. Becky mentions that there have actually been not just one but 5 micrometeor impacts so far. Basically one per month. Over time, the damage could add up.

And, not to derail, but I makes me think about the difficulty of even a mission to Mars, much less interstellar travel.

In science fiction, it's a problem that is just ignored for the most part. But these little dust or sand-sized particles could make travel between stars impossible from a practical standpoint. After all, if you want to get there in less than 10,000 years or so, you would need to travel at a significant fraction of the speed of light, but could any spaceship even survive that, or would it be ablated (eroded) away en route? Would it still be functional when it arrives? Or would it be shot through with tiny bullet holes? This could be the reason for the Fermi "paradox". That is, even highly advanced intelligent civilizations are incapable of traveling between stars, because it's impossible from a practical standpoint. Like trying to swim across an ocean that's 1000 times wider than the Pacific. Theoretically possible, but not practically possible.
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Shields up Mr Chekov!! :D
 
I wondered whether some kind of shields are possible, but I don’t know if they are. At least those like you see in Star Trek. Physical shields would add a lot of weight but maybe they are the only realistic idea. And would even those be eroded away during the journey.
 
Puppycow said:
So, Dr. Becky mentions that there have actually been not just one but 5 micrometeor impacts so far. Basically one per month. Over time, the damage could add up.

And, not to derail, but I makes me think about the difficulty of even a mission to Mars, much less interstellar travel.

In science fiction, it's a problem that is just ignored for the most part. But these little dust or sand-sized particles could make travel between stars impossible from a practical standpoint. After all, if you want to get there in less than 10,000 years or so, you would need to travel at a significant fraction of the speed of light, but could any spaceship even survive that, or would it be ablated (eroded) away en route? Would it still be functional when it arrives? Or would it be shot through with tiny bullet holes? This could be the reason for the Fermi "paradox". That is, even highly advanced intelligent civilizations are incapable of traveling between stars, because it's impossible from a practical standpoint. Like trying to swim across an ocean that's 1000 times wider than the Pacific. Theoretically possible, but not practically possible.
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One solution proposed in SF (notably by Arthur C. Clarke and Alastair Reynolds, is a water ice nose cone that ablates over the course of the trip. In Clarke's novel, Songs of Distant Earth, the inciting incident is a latter-day colony ship stopping over at an earlier-established colony to harvest some water from that planet's ocean to replenish their shield before the next leg of their journey.
 
slyjoe said:
1. Hubble is in Low Earth Orbit (LEO).
2. Hubble has a flap over the entrance to the mirror that can be closed.
3. That tube makes it less likely a micrometeoroid will enter the tube and hit the mirror. Hubble would have to be pointed directly at it.

That said, we know the solar arrays have been bombarded with hundreds/thousands of micrometeoroids. Hubble also has to worry about more space debris than Webb.
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You forgot 4: Hubble's mirror is a single piece. Damage can't move a segment, but likewise the mirror doesn't need to be adjusted to compensate.
 
theprestige said:
One solution proposed in SF (notably by Arthur C. Clarke and Alastair Reynolds, is a water ice nose cone that ablates over the course of the trip. In Clarke's novel, Songs of Distant Earth, the inciting incident is a latter-day colony ship stopping over at an earlier-established colony to harvest some water from that planet's ocean to replenish their shield before the next leg of their journey.
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One of my favourite Clarke novels. It's what I thought of immediately.
 
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