5 ms·

> Instead of building one huge short life-span spacecraft Short life-span? How long has the Hubble been up there?

by zabzonk 5y ago

minitoar 5y ago
It’s the telescope of Theseus, though.
- xref 5y ago
  Because some component bays designed to be swapped out were swapped out? Far as I know they haven’t replaced the 2.4m main mirror or the housing, you know, the “ship”
  - minitoar 5y ago
    Yes, that is the joke I was making. Thank you for explaining it.
    - vimacs2 5y ago
      I think their point was your joke doesn't make much sense when only a small subsection of the entire telescope was ever replaced.
      - minitoar 5y ago
        In my opinion that's part of what makes it funny, and is also a core issue in the Ship of Theseus problem -- who's to say how much it can be changed and is still "the same thing"? Maybe the thing that was replaced was very small but was very important to the identity.
        deleted 5y ago
        [deleted]
        xref 5y ago
        That’s not what the Ship of Theseus is. The thought experiment is: if you replace 100% of the original object then is it the same object. Not like, if you change the batteries in the remote is it the same remote.
- zabzonk 5y ago
  Sort of. The broken optics famously got fixed in the first HST shuttle mission, and there have been other replacements over time. A lot of it is the same, though. And of course, the HST is in LEO, which means it is reachable with current rocket tech, which the James Webb, being situated at L2 won't be. But that's not to say you could not have a large platform at L2 (or another Lagrange point) that could be serviced by robots, or even manned craft, if it was designed that way.
  - GekkePrutser 5y ago
    But Hubble wasn't a one-off design. It shared a lot of design elements with other space telescopes that are more earth-focused :) So it had a lot more benefits of scale than JWST.
  - minitoar 5y ago
    I guess my point was: without that servicing it would’ve been a pretty short life span (literally 0?). The swarm approach helps with this.
foolfoolz 5y ago
webb needs to use thrusters to stay in position. there’s 5 years worth of fuel onboard they did design the fuel in a way that potentially could be refilled… but the refilling craft doesn’t exist. and webb timescales make that sound impossible
- Taniwha 5y ago
  And it's at L2 so not that easy to get to
  - prox 5y ago
    I take Starship could, and should be operational in some form by then.
    - Cthulhu_ 5y ago
      Question is whether it'll be financially / commercially viable. I think that greatly depends on how much data the telescope gathers or whether it needs more time. Also keep in mind that the Hubble got multiple upgrades over its lifespan, which will be much more difficult with the Webb - is it feasible to do spacewalks that far out? Has any astronaut ever done a spacewalk outside of Earth orbit?
      - LargoLasskhyfv 5y ago
        Are you referring to the protection by Earths magnetic field? If so, would it matter much, given we (allegedly) shot humans in not more than slightly pressurized tin cans to the moon multiple times? And they survived.
      - prox 5y ago
        Yeah, if it has done it set out to do, then we don’t need to. Also depends how much of a moon presence we have in five years. Launching from the moon might make it feasible for sure, considering the billions the JWST has cost!
- arp242 5y ago

> Instead of building one huge short life-span spacecraft Short life-span? How long has the Hubble been up there?

minitoar 5y ago

It’s the telescope of Theseus, though.

xref 5y ago
Because some component bays designed to be swapped out were swapped out? Far as I know they haven’t replaced the 2.4m main mirror or the housing, you know, the “ship”
- minitoar 5y ago
  Yes, that is the joke I was making. Thank you for explaining it.
  - vimacs2 5y ago
    I think their point was your joke doesn't make much sense when only a small subsection of the entire telescope was ever replaced.
    - minitoar 5y ago
      In my opinion that's part of what makes it funny, and is also a core issue in the Ship of Theseus problem -- who's to say how much it can be changed and is still "the same thing"? Maybe the thing that was replaced was very small but was very important to the identity.
      - deleted 5y ago
        [deleted]
      - xref 5y ago
        That’s not what the Ship of Theseus is. The thought experiment is: if you replace 100% of the original object then is it the same object. Not like, if you change the batteries in the remote is it the same remote.
zabzonk 5y ago
Sort of. The broken optics famously got fixed in the first HST shuttle mission, and there have been other replacements over time. A lot of it is the same, though. And of course, the HST is in LEO, which means it is reachable with current rocket tech, which the James Webb, being situated at L2 won't be. But that's not to say you could not have a large platform at L2 (or another Lagrange point) that could be serviced by robots, or even manned craft, if it was designed that way.
- GekkePrutser 5y ago
  But Hubble wasn't a one-off design. It shared a lot of design elements with other space telescopes that are more earth-focused :) So it had a lot more benefits of scale than JWST.
- minitoar 5y ago
  I guess my point was: without that servicing it would’ve been a pretty short life span (literally 0?). The swarm approach helps with this.

foolfoolz 5y ago

webb needs to use thrusters to stay in position. there’s 5 years worth of fuel onboard they did design the fuel in a way that potentially could be refilled… but the refilling craft doesn’t exist. and webb timescales make that sound impossible

Taniwha 5y ago
And it's at L2 so not that easy to get to
- prox 5y ago
  I take Starship could, and should be operational in some form by then.
  - Cthulhu_ 5y ago
    Question is whether it'll be financially / commercially viable. I think that greatly depends on how much data the telescope gathers or whether it needs more time. Also keep in mind that the Hubble got multiple upgrades over its lifespan, which will be much more difficult with the Webb - is it feasible to do spacewalks that far out? Has any astronaut ever done a spacewalk outside of Earth orbit?
    - LargoLasskhyfv 5y ago
      Are you referring to the protection by Earths magnetic field? If so, would it matter much, given we (allegedly) shot humans in not more than slightly pressurized tin cans to the moon multiple times? And they survived.
    - prox 5y ago
      Yeah, if it has done it set out to do, then we don’t need to. Also depends how much of a moon presence we have in five years. Launching from the moon might make it feasible for sure, considering the billions the JWST has cost!
arp242 5y ago