5 ms·

> These motors, actuators, assemblies, etc need to be incredibly precise and reliable Is it impossible to build to a lower level of reliability then have human

by ars 4y ago

> These motors, actuators, assemblies, etc need to be incredibly precise and reliable Is it impossible to build to a lower level of reliability then have humans available to fix/adjust things in orbit? Then once it's fully assembled in place, move it to its final location?

WalterBright 4y ago
Don't we also have 60 years of experience with motors, actuators, and assemblies in space?
HideousKojima 4y ago
Some of the parts are so sensitive them weren't deployed until the telescope got into its final position at the moon's L2 Lagrange point. If you had humans assemble it in orbit it would still have to undergo the stresses of acceleration to get to the L2 Lagrange point.
UmYeahNo 4y ago
I don't think that's possible because, if I understand correctly, many of the parts need to be adjusted periodically to maintain accuracy. It's not a set-once-and-forget type situation. Those parts need to be able to make extraordinarily precise adjustments repeatedly for the life of the mission. "Aligning the primary mirror segments as though they are a single large mirror means each mirror is aligned to 1/10,000th the thickness of a human hair. This alignment has to be done at 50 degrees above absolute zero! [0] [0]https://www.nasa.gov/topics/technology/features/webb-actuator.html https://www.nasa.gov/topics/technology/features/webb-actuato...
jmyeet 4y ago
Yes and no. It raises a bunch of questions/problems, wuch as: 1. Where doe the telescope deploy? Ideally in LEO so you have a chance fo fix things but then that complicated the launch. You have to park in orbit and restart th eengine at a later point. AFAIK JWST didn't enter a parking orbit so would've required additional fuel. That might not have been possible; 2. What if the launcher itself fails? Do you want to have the capacity to launch another rocket, have it rock with JWST and then go on? If so, that's a whole new level of complexity and a set of problesm you have to solve as well as things that can go wrong; 3. If you look at the flight plan there are a bunch of turns. How would the G-forces affect, say, the deployed heat shield? 4. JWST actually had to rotate during launch to point the instruments away from the Sun so as not to destroy them. This already added complexity. Doing this with the deployed spacecraft would probably only further complicate this.
unyttigfjelltol 4y ago
The Webb is orbiting the Earth/Sun system at a Lagrange point. It's not in a normal Earth orbit. Astronauts have not gone that far from Earth

by ars 4y ago

WalterBright 4y ago

Don't we also have 60 years of experience with motors, actuators, and assemblies in space?

HideousKojima 4y ago

Some of the parts are so sensitive them weren't deployed until the telescope got into its final position at the moon's L2 Lagrange point. If you had humans assemble it in orbit it would still have to undergo the stresses of acceleration to get to the L2 Lagrange point.

UmYeahNo 4y ago

I don't think that's possible because, if I understand correctly, many of the parts need to be adjusted periodically to maintain accuracy. It's not a set-once-and-forget type situation. Those parts need to be able to make extraordinarily precise adjustments repeatedly for the life of the mission. "Aligning the primary mirror segments as though they are a single large mirror means each mirror is aligned to 1/10,000th the thickness of a human hair. This alignment has to be done at 50 degrees above absolute zero! [0] [0]https://www.nasa.gov/topics/technology/features/webb-actuator.html https://www.nasa.gov/topics/technology/features/webb-actuato...

jmyeet 4y ago

Yes and no. It raises a bunch of questions/problems, wuch as: 1. Where doe the telescope deploy? Ideally in LEO so you have a chance fo fix things but then that complicated the launch. You have to park in orbit and restart th eengine at a later point. AFAIK JWST didn't enter a parking orbit so would've required additional fuel. That might not have been possible; 2. What if the launcher itself fails? Do you want to have the capacity to launch another rocket, have it rock with JWST and then go on? If so, that's a whole new level of complexity and a set of problesm you have to solve as well as things that can go wrong; 3. If you look at the flight plan there are a bunch of turns. How would the G-forces affect, say, the deployed heat shield? 4. JWST actually had to rotate during launch to point the instruments away from the Sun so as not to destroy them. This already added complexity. Doing this with the deployed spacecraft would probably only further complicate this.

unyttigfjelltol 4y ago

The Webb is orbiting the Earth/Sun system at a Lagrange point. It's not in a normal Earth orbit. Astronauts have not gone that far from Earth