Potential servicing missions for the Webb

[Lee Jay]

With NASA saying there are up to 20 years of fuel onboard web, I think that also obviates the need for a servicing mission.

If everything works and stays working.

[deltaV]

With NASA saying there are up to 20 years of fuel onboard web, I think that also obviates the need for a servicing mission.

NASA's previous 11-digit-dollar space telescope (Hubble) has lasted for 31+ years. So a servicing mission in ~2040 to refill JWST's propellant tanks seems plausible.

[Jim]

With NASA saying there are up to 20 years of fuel onboard web, I think that also obviates the need for a servicing mission.

NASA's previous 11-digit-dollar space telescope (Hubble) has lasted for 31+ years. So a servicing mission in ~2040 to refill JWST's propellant tanks seems plausible.

Bad logic.  HST lasted because it was serviced.

[deltaV]

The Chandra X-ray Observatory has been active for 22 years without any servicing (https://en.wikipedia.org/wiki/Chandra_X-ray_Observatory). I'm not saying that a refueling mission is probable, just that it's plausible.

[deadman1204]

With NASA saying there are up to 20 years of fuel onboard web, I think that also obviates the need for a servicing mission.

NASA's previous 11-digit-dollar space telescope (Hubble) has lasted for 31+ years. So a servicing mission in ~2040 to refill JWST's propellant tanks seems plausible.

One of these was designed for servicing - to have instruments changed and other stuff. The other simply wasn't....

[maxtout]

Astroscale, who had their own demonstrator for servicing OOS satellites in LEO, bought IP and assets for a previous venture called Space Drone. This was being developed in a joint partnership between a UK and an Israeli company, the former being around since 2013 and the deal signed 2018.
The sale of Space Drone was in 2020.

The reason this is interesting is because the main idea behind Space Drone is to use its manipulators to grapple payload rings (spacecraft separation rings) for docking.

This allows you to grapple OOS spacecraft who do not have a rocket nozzle available in that position that MEV and many others require.
With multiple arms instead of just one, which most solutions feature (DARPA's Orbital Express / RSGS), this makes it a much more stable solution.

JWST falls into that position of not having a centralized rocket motor nozzle to launch a stinger down it, and also does not feature a prominent marman ring which is often used as a grapple. 
Bur it does have a payload ring, bolted on to the bus cone as part of the structure.
The inner ring, aside from having the two small thruster nozzles to one side, also features absorption and reflective tile covered radiators and the ring is similarly tile covered itself.

From concept work it seems that Space Drone grappled on the outer rim edge of the spacecraft separation ring and a variation of this would be most useful. Anything beyond that of course is another matter.

Although i know of the position of the fill/drain valves it is very hard to see them in most photographs of the bus.
A robotic system at the current level would similarly find it difficult I suspect, although they have been experimenting on this for many years. .

[Jim]

The payload ring is a Marman ring.

[tibber]

The payload ring is a Marman ring.

Thanks.

Is it held away from the rest of the bus by standoffs or something that would give enough clearance for an arm to grab the ring?
I guess I should also ask if the ring is strong enough for such a grab?

Cheers,
Tom

[Jim]

The payload ring is a Marman ring.

Thanks.

Is it held away from the rest of the bus by standoffs or something that would give enough clearance for an arm to grab the ring?
I guess I should also ask if the ring is strong enough for such a grab?

Cheers,
Tom

it connected the spacecraft to the launch vehicle

[maxtout]

I see marman ring, spacecraft separation ring and payload adapter used interchangeably for the same collection of hardware.
Same goes for the clamp.

In this context, most material stated payload ring and adapter and clamp for JWST.
The guideline for the Marman Ring standard was substantially different in profile when compared to JWST so in most cases I leave it at payload ring.

Is it held away from the rest of the bus by standoffs or something that would give enough clearance for an arm to grab the ring?

https://svs.gsfc.nasa.gov/14052
Shows that it is not proud, and doesn't have to be for its job.
JWST's complication is that there are boxes covered in OSR (as is the ring itself) arrayed around the inside of the ring, so if you 'just' grabbed it, you would damage those parts.

For the way Space Drone seemed to indicate (more delicate than most current grabbers that also grip both sides of the ring profile), yes it is, which is why I mentioned it.
As it is, other existing grabbers have been designed for more prominent ring profiles.

I guess I should also ask if the ring is strong enough for such a grab?

forged rolled aluminium, yes it is strong enough, it has to be when mounted on the launcher, supporting the payload and its connection.

[tibber]

The payload ring is a Marman ring.

Thanks.

Is it held away from the rest of the bus by standoffs or something that would give enough clearance for an arm to grab the ring?
I guess I should also ask if the ring is strong enough for such a grab?

Cheers,
Tom

it connected the spacecraft to the launch vehicle

Well, yeah.  That was assumed as part of the definition.

What I'm asking is the ring so closely attached to the space craft that a drone would be unlikely to have room to grab onto?
The second question related to the strength of the ring for the drone to grab and then connect the two together? In the launching position the whole ring would share in the load, which I presume is mostly pushing toward the spacecraft, whereas a grab would be one or two attachments subject to (I presume) vastly different force vectors.

Of course, I also expect any grab action would be programmed to be a gentle as possible so Webb isn't pushed significantly.

Cheers,
Tom

[maxtout]

The telescope backbone is connected to the core inside of the bus.

The bus is visibly square, but inside it is actually a cone. So it is very strong for the role it serves.

A  graphite-epoxy composite cone that the payload ring is bolted on to.

[tibber]

...

https://svs.gsfc.nasa.gov/14052
Shows that it is not proud, and doesn't have to be for its job.
JWST's complication is that there are boxes covered in OSR (as is the ring itself) arrayed around the inside of the ring, so if you 'just' grabbed it, you would damage those parts.

...

Thanks for the link to the videos! Very helpful.

And for your explanations.

Cheers,
Tom

[LouScheffer]

Although i know of the position of the fill/drain valves it is very hard to see them in most photographs of the bus.
A robotic system at the current level would similarly find it difficult I suspect, although they have been experimenting on this for many years.

According to this diagram, the drain and fill valves project out of the spacecraft bus, supposedly to make any hypothetical refueling easier.  So they should not be hard to spot.

[Jim]

They are covered in MLI

[maxtout]

They are covered in MLI

Precisely. Anyone have a good photo of it?

[JulesVerneATV]

robotic support repair, maintenance and rescue of older spacecraft

NASA 'Swift' but with the private sector getting involved maybe relevant for Hubble and future Webb

Private mission to save NASA space telescope will launch in 2026 on a rocket dropped from a plane
https://www.space.com/space-exploration/missions/katalyst-space-technologies-swift-observatory-rescue-mission-pegasus-rocket


Spacecraft to Boost NASA Telescope's Orbit for the First Time
https://www.extremetech.com/aerospace/private-spacecraft-to-boost-nasa-telescopes-orbit-for-the-first-time
It's another example of NASA relying more on private enterprise for its orbital infrastructure and maintenance.