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Why it's not made serviceable? Or at least able to be serviced, with non-herculean efforts? Manned missions to L2 would both maintain the truly unique device an

by avmich 5y ago

Why it's not made serviceable? Or at least able to be serviced, with non-herculean efforts? Manned missions to L2 would both maintain the truly unique device and move forward the manned space capabilities and experience. It's just - what? - four time farther than the Moon?

sp332 5y ago
It was hard enough to make it small and lightweight enough to get out there, with epoxy instead of bolts for example.
Nekhrimah 5y ago
At the time the design was locked in, there was nothing even planned that would be capable of supporting a crewed servicing mission. They have however included a grapple bar so that there is something to connect to should there be something in the future. SpaceX's Starship is the most likely vehicle at this stage, but that is still substantial development away from being capable of a James Webb servicing mission.
knappe 5y ago
How would we get there? There is no current vehicle that could be used to service anything at L2.
- avmich 5y ago
  Orion ( https://en.wikipedia.org/wiki/Orion_(spacecraft) https://en.wikipedia.org/wiki/Orion_(spacecraft) ) - "Capable of supporting a crew of six beyond low Earth orbit, Orion can last up to 21 days undocked". Can be used, especially with booster which can be launched by e.g. Falcon-9 Heavy, or if more mass required, by SLS (!) or Big Falcon Rocket.
  - knappe 5y ago
    Orion is not viable. They haven't even launched Artemis 1, let alone Artemis 2 (which is scheduled for 2023!) which would be the _first_ crewed launch. I'm not sure why we would plan to service JWT when we have nothing to service it with.
sparker72678 5y ago
One reason (of many) is that when the telescope was designed there was no way to know if we'd have capability to send anyone (or anything) to service it. Even today we don't have a proven platform that could pull off a manned mission to L2, let alone a mission that would then fix an insanely complex telescope in-situ. (There are a few that could try, but no one's done it.)
cycomanic 5y ago
Sending a manned mission to L2 for repair just doesn't make sense. You might as well just build a new telescope and send it out again, that probably would be cheaper. Just look at the massive effort that it took to go to the moon. Sure we are now more advanced, but if it was easy to go there now Elon would've already flown. As you said L2 is 4 times further, and you need to stop and restart at each point.
- pklausler 5y ago
  Re: stopping and restarting: there's a trade-off to be made here between flight time and necessary delta-V for arriving at a Lagrange point (and an independent one for departing). If you're willing to take the time (and consumables), you could use a slow trajectory that arrives with negligible relative velocity. And you can go there fast, arrive nearly dry, and still get back by "falling out of the sky". It's an interesting optimization problem.
  - ericbarrett 5y ago
    Note that if you send a human crew you don’t really want to go slow because of cosmic rays (not to mention being locked in a can). Autonomous robotics have come a long way but I don’t think they’re ready for state of the art telescope repair.
    - avmich 5y ago
      Soviet spaceship TKS ( https://en.wikipedia.org/wiki/TKS_spacecraft https://en.wikipedia.org/wiki/TKS_spacecraft ) was a whole orbital station module together with return capsule, developed up to mid-1980-s. It was supposed to be launched manned, and crew members - up to 3 - would have a lot of space available to them right after getting to orbit. So it could be considered as a long-range mission spacecraft; it would need to have a booster module, but that's solvable (i.e. Agena for Gemini-10 flight https://en.wikipedia.org/wiki/Agena_target_vehicle https://en.wikipedia.org/wiki/Agena_target_vehicle ).
      - 5y ago
Rebelgecko 5y ago
There actually is a docking adapter, but its utility is limited for a few reasons * If you're futzing with hydrazone, you want to avoid sending humans to mess with it * Any mission to repair it risks damaging the sensors just from the reaction mass that it takes to rendezvous * There is currently no path forward to actually doing this servicing mission, in terms of equipment and vehicles. The technology will almost definitely exist in the future, but by the time it does why not just send a new mission? * Designing the spacecraft to make it serviceable imposes new limitations on it
shirro 5y ago
Inspiration 4, the private mission scheduled to launch next week, will be the furthest a manned mission has gone from earth since the last space shuttle Hubble servicing mission over a decade ago. Hubble is only about 100km higher than ISS. To visit L2 you basically need a a vehicle and rocket capable of performing a moon mission which hasn't been available since 1972.
- avmich 5y ago
  > To visit L2 you basically need a a vehicle and rocket capable of performing a moon mission which hasn't been available since 1972. You don't need to land on anything - and that's a quite large delta-V saving, about 5 km/s for Apollo-style missions. So you save on mass, and you can spend savings elsewhere.
  - shirro 5y ago
    NASA keep calling SLS block 1 a moon rocket and it can't land anything on the moon either. All it can do is transfer crew to a halo orbit and back. And Orion clearly isn't a very capable vehicle for satellite refurbishing. Without an airlock EVAs would require depressurising the whole vehicle and it can't carry any big payloads or a robotic arm. My guess is after mass is added for all the capabilities shuttle had for spacecraft servicing you probably do need a real moon rocket.
- interestica 5y ago
  > which hasn't been available since 1972. I mean, technically they were available after '72. There were a couple Saturn V's and Command/Service Modules (and at least one Lunar Module) left over (and mostly repurposed). It would be interesting to know when the last time the hardware existed in working order that would have allowed a lunar mission. https://en.wikipedia.org/wiki/Canceled_Apollo_missions#Cancellations https://en.wikipedia.org/wiki/Canceled_Apollo_missions#Cance...
justin66 5y ago
> It's just - what? - four time farther than the Moon? Oh, is that all?
- avmich 5y ago
  Well, the Moon is some 1+ light second from Earth, with average orbital radius of 384,400 km. L2 in Sun-Earth system is roughly 1.5 millions kilometers. That roughly makes four times difference.

by avmich 5y ago

sp332 5y ago

It was hard enough to make it small and lightweight enough to get out there, with epoxy instead of bolts for example.

Nekhrimah 5y ago

At the time the design was locked in, there was nothing even planned that would be capable of supporting a crewed servicing mission. They have however included a grapple bar so that there is something to connect to should there be something in the future. SpaceX's Starship is the most likely vehicle at this stage, but that is still substantial development away from being capable of a James Webb servicing mission.

knappe 5y ago

How would we get there? There is no current vehicle that could be used to service anything at L2.

avmich 5y ago
Orion ( https://en.wikipedia.org/wiki/Orion_(spacecraft) https://en.wikipedia.org/wiki/Orion_(spacecraft) ) - "Capable of supporting a crew of six beyond low Earth orbit, Orion can last up to 21 days undocked". Can be used, especially with booster which can be launched by e.g. Falcon-9 Heavy, or if more mass required, by SLS (!) or Big Falcon Rocket.
- knappe 5y ago
  Orion is not viable. They haven't even launched Artemis 1, let alone Artemis 2 (which is scheduled for 2023!) which would be the _first_ crewed launch. I'm not sure why we would plan to service JWT when we have nothing to service it with.

sparker72678 5y ago

One reason (of many) is that when the telescope was designed there was no way to know if we'd have capability to send anyone (or anything) to service it. Even today we don't have a proven platform that could pull off a manned mission to L2, let alone a mission that would then fix an insanely complex telescope in-situ. (There are a few that could try, but no one's done it.)

cycomanic 5y ago

Sending a manned mission to L2 for repair just doesn't make sense. You might as well just build a new telescope and send it out again, that probably would be cheaper. Just look at the massive effort that it took to go to the moon. Sure we are now more advanced, but if it was easy to go there now Elon would've already flown. As you said L2 is 4 times further, and you need to stop and restart at each point.

pklausler 5y ago
Re: stopping and restarting: there's a trade-off to be made here between flight time and necessary delta-V for arriving at a Lagrange point (and an independent one for departing). If you're willing to take the time (and consumables), you could use a slow trajectory that arrives with negligible relative velocity. And you can go there fast, arrive nearly dry, and still get back by "falling out of the sky". It's an interesting optimization problem.
- ericbarrett 5y ago
  Note that if you send a human crew you don’t really want to go slow because of cosmic rays (not to mention being locked in a can). Autonomous robotics have come a long way but I don’t think they’re ready for state of the art telescope repair.
  - avmich 5y ago
    Soviet spaceship TKS ( https://en.wikipedia.org/wiki/TKS_spacecraft https://en.wikipedia.org/wiki/TKS_spacecraft ) was a whole orbital station module together with return capsule, developed up to mid-1980-s. It was supposed to be launched manned, and crew members - up to 3 - would have a lot of space available to them right after getting to orbit. So it could be considered as a long-range mission spacecraft; it would need to have a booster module, but that's solvable (i.e. Agena for Gemini-10 flight https://en.wikipedia.org/wiki/Agena_target_vehicle https://en.wikipedia.org/wiki/Agena_target_vehicle ).
    - 5y ago

Rebelgecko 5y ago

There actually is a docking adapter, but its utility is limited for a few reasons * If you're futzing with hydrazone, you want to avoid sending humans to mess with it * Any mission to repair it risks damaging the sensors just from the reaction mass that it takes to rendezvous * There is currently no path forward to actually doing this servicing mission, in terms of equipment and vehicles. The technology will almost definitely exist in the future, but by the time it does why not just send a new mission? * Designing the spacecraft to make it serviceable imposes new limitations on it

shirro 5y ago

Inspiration 4, the private mission scheduled to launch next week, will be the furthest a manned mission has gone from earth since the last space shuttle Hubble servicing mission over a decade ago. Hubble is only about 100km higher than ISS. To visit L2 you basically need a a vehicle and rocket capable of performing a moon mission which hasn't been available since 1972.

avmich 5y ago
> To visit L2 you basically need a a vehicle and rocket capable of performing a moon mission which hasn't been available since 1972. You don't need to land on anything - and that's a quite large delta-V saving, about 5 km/s for Apollo-style missions. So you save on mass, and you can spend savings elsewhere.
- shirro 5y ago
  NASA keep calling SLS block 1 a moon rocket and it can't land anything on the moon either. All it can do is transfer crew to a halo orbit and back. And Orion clearly isn't a very capable vehicle for satellite refurbishing. Without an airlock EVAs would require depressurising the whole vehicle and it can't carry any big payloads or a robotic arm. My guess is after mass is added for all the capabilities shuttle had for spacecraft servicing you probably do need a real moon rocket.
interestica 5y ago
> which hasn't been available since 1972. I mean, technically they were available after '72. There were a couple Saturn V's and Command/Service Modules (and at least one Lunar Module) left over (and mostly repurposed). It would be interesting to know when the last time the hardware existed in working order that would have allowed a lunar mission. https://en.wikipedia.org/wiki/Canceled_Apollo_missions#Cancellations https://en.wikipedia.org/wiki/Canceled_Apollo_missions#Cance...

justin66 5y ago

> It's just - what? - four time farther than the Moon? Oh, is that all?

avmich 5y ago
Well, the Moon is some 1+ light second from Earth, with average orbital radius of 384,400 km. L2 in Sun-Earth system is roughly 1.5 millions kilometers. That roughly makes four times difference.