Nothing is impossible, but L2 is much further away than humans have ever been. AFAIK, we do not have any human rated spacecraft even remotely capable of going that far (and, hopefully, coming back).

Current plans are for it not to be serviced. Considering that it’s sitting way beyond the moon at L2, it’d have been out of each even for the shuttles when they were still in service.

However, hopefully it’s not out of reach of the hardware we’ll have in 20 years. Even though right now our capability is actually less than 20 years ago…

JWST will be so far away from earth that is unlikely any human will ever get near him. Also, Hubble was designed to be serviceable during its lifetime. This isn't the case for JWST.

Maybe technology will develop enough to allow us to send drones to work on JWST, but today this is still just a dream.

PS: I'm just a random code monkey on the internet, so take these comments with a grain of salt.

20 years is a long time, and space is moving fast these days. I wouldn't bet on it not being serviced (although I do agree that we'll have something better by then).

If I were to bet on something it would be a simpler but bigger design that takes advantage of Starship’s much wider fairing.

Let’s say we wanted a constellation of telescopes to do full sky surveys of small objects in our system for asteroid detection. Do those need to be kept at near absolute zero to be effective at that task?

Webb has a specific mission of imaging deeply redshifted space. I would hope in 20 years we’ll be able to launch bigger, simpler, and cheaper designs for more “pedestrian” missions.

The JWST was not designed to be serviceable. It's not impossible, but it's not in the plans right now.

It's unlikely anything at L2 could be serviced until we have significant infrastructure in space (like something for refuelling). Hubble orbits about 400 miles up, JWST is about 1 million miles away.

JWST was designed for future refueling capabilities (there is a docking target and an externally accessible port for access to propellant storage), and this mission is well within existing launch vehicle capabilities (if a robotic refueler is lifted as payload). At launch, JWST was fueled with ~301 kg of propellant, so subtract that from launch vehicle payload to get an idea how heavy your refueling vehicle can be (assuming roughly 4k-5k kg depending on launch vehicle), and some margin for the refueler to separate and propel itself over the gravity edge JWST balances itself on from L2 into deep space post refueling.

https://space.stackexchange.com/a/38415

https://time.com/6127003/webb-space-telescope-discoveries/

> Webb faces other operational challenges, however. Hubble has been kept alive in part through maintenance and servicing runs done by astronauts. Webb’s great distance from Earth makes that kind of house call impossible. What’s more, in order to remain stable at its gravity-balanced Lagrange point, Webb needs a thruster system, and a thruster system requires fuel. The telescope will launch with a full tank, but that will be only enough to keep it operating for a minimum of five years and a maximum of 10. In theory, a refill ought to be possible, and the telescope is actually equipped with a docking target to accommodate an incoming spacecraft that could conduct a refueling and extend the JWST’s life. It’s an appealing idea, especially considering the telescope’s dizzying price tag. That spacecraft, however, does not yet exist, though it could within the next decade.

To be honest, sounds like a cool project to start working on, with the idea that it becomes an off the shelf capability for future space observatories. SpaceX's Dragon can carry a 6000 kg payload, and already supports autonomous docking with the ISS, for example.

By "servicing" I actually meant more "repair". The initial burns left enough fuel that JWST is likely to wear out before it runs out of fuel. The refuelling I meant was for craft to get people there and back, because repair is significantly more difficult than refuelling.

https://blogs.nasa.gov/webb/2021/12/29/nasa-says-webbs-exces...

My mistake. In that case, it'd likely be more reasonable to get a vehicle to the observatory, boost it back to Earth orbit, and then attempt to return it to L2 after on orbit servicing. I don't know what that Delta-v budget looks like, although I'm happy to throw coffee money someone's way if they want to do the math in this thread.

its L2 point takes about a month to reach, much different orbit than Hubble which is why the flawless launch is so important and the unpacking.