JWST

[Screwdriver]

This 9 hour print did not want to stay stuck down last night...

The raft was still very firmly attached but wow that odd shape generated a fair bit of warp power.

 

[selectedgrub]

What is this?

 

[Maker]

The James Webb Space Telescope, like Hubble but bigger and better.

 

[Screwdriver]

What is this?

That's the base, edited since the first model. The two brackets attach the forward and aft sunshield pallets.

The most difficult part of this build is not the modelling but changing the design 1. to allow it to print at all and 2. to allow modifications/revisions for the attached pieces.

So I have built in some adaptability to some of the major parts (those which need 6 hour plus print times) so that if I need to change anything, I don't need to reprint an entire assembly.

For the base, I need to fit some extending telescopic boom arms and they will break! Eventually. Plus I need one version that telescopes and one that doesn't for the full five shield version which will not fold. There is no product I can scale down 40:1 that is thinner than the 0.025mm Kapton tape on the real thing!

So for exampe, tried to use some gold leaf to gild some of the mirrors and that stuff is about 0.5 microns. Smoke particles average about 2.5 microns so that just goes to show why gold leaf is 1. so damned delicate and 2. so cheap because a tiny amount goes a long way.

If I scale the 25 micron JWST sun shield material (down to 0.6 micron), it needs to be about the same thickness as a gold leaf. Forget about how that compares to a "human hair", that's thinner than smoke!!

 

[ukracer]

That's the base, edited since the first model. The two brackets attach the forward and aft sunshield pallets.

The most difficult part of this build is not the modelling but changing the design 1. to allow it to print at all and 2. to allow modifications/revisions for the attached pieces.

So I have built in some adaptability to some of the major parts (those which need 6 hour plus print times) so that if I need to change anything, I don't need to reprint an entire assembly.

For the base, I need to fit some extending telescopic boom arms and they will break! Eventually. Plus I need one version that telescopes and one that doesn't for the full five shield version which will not fold. There is no product I can scale down 40:1 that is thinner than the 0.025mm Kapton tape on the real thing!

So for exampe, tried to use some gold leaf to gild some of the mirrors and that stuff is about 0.5 microns. Smoke particles average about 2.5 microns so that just goes to show why gold leaf is 1. so damned delicate and 2. so cheap because a tiny amount goes a long way.

If I scale the 25 micron JWST sun shield material (down to 0.6 micron), it needs to be about the same thickness as a gold leaf. Forget about how that compares to a "human hair", that's thinner than smoke!!

How about printing in pieces with pegs?

 

[Screwdriver]

How about printing in pieces with pegs?

That is what I am doing.

 

[ukracer]

That is what I am doing.

Smaller pieces then lol

 

[Screwdriver]

Smaller pieces then lol

Well I could conceivably end up with something that looks a lot like an airfix kit. Before then though I need to get the engineering challenges out of the way and the gross dimensions to my satisfaction. After that I can nip and tuck each part until I'm perfectly happy.

Got plenty of time, JWST has so much fuel on board after a textbook launch, looks like it's gone from a 5-8 year mission to a 20+

 

[Screwdriver]

More bits and bobs.

None of the gold work is to my satisfaction but I have a solution that will work so all that stuff gets peeled off and done right.

Plus I need to work on my photography and find a dark/grey backdrop.

 

[Parm]

More bits and bobs.

None of the gold work is to my satisfaction but I have a solution that will work so all that stuff gets peeled off and done right.

Plus I need to work on my photography and find a dark/grey backdrop.

Set up a mini infinity wall so you don’t get that line between the table and wall. White backdrop is the norm but experiment with colours to find one you like.

Your project is looking good

 

[slim_boy_fat]

@Screwdriver How much machine printing time do you reckon the project's taken to date?

 

[Screwdriver]

I will take better pictures of the completed model but in the meantime, this prototype looks worse the better the picture is!

FWD sunshield pallet is done and you can see why the entire upper half of the JWST has to lift out of the way.

So I will remodel the deployable tower assembly so that it too can be deployed. It needs to lower by 1200mm (30mm on the model) so that the fwd_ss_pallet can fold up without clouting the top of the mirror. Tricky because there can be no slop and it has to remain aligned and cannot be allowed to rotate.

I have bigger fish to fry. When I first decided to make a model, I looked at the largest single part and scaled it to fit the Ender3. It came out at "about" 40:1 which seemed a good idea at the time. Problem is, the AFT sunshield pallet is the same size as the print bed! Doh!

It just about fits.

This is what that looks like.

I forgot some time ago I hacked a bit of code which allows me to print right up to the edge. I should have remembered because every once in a while I clout the bed clips, the whole thing shakes and it prints over the metal clip. On this occasion, it clipped the edge and dragged the bed 5mm out of whack.

Perhaps inadvisedly I let it run and just tacked it down with one of those freehand printing pens.

That is just the print raft and the model sits just inside it, 10-15mm from each edge. I will be on tenterhooks for the next 11 hours (!) babysitting the print. Seems to have worked out. It's now printing on the raft. Most of this part it raft and support with it being both large and an odd shape.

So I'll let it run and find out what happens by midnight...

 

[Screwdriver]

@Screwdriver How much machine printing time do you reckon the project's taken to date?

Oh, I dunno, five major parts are 8-12 hours each. The smaller bits are between 1-2 hours. I mostly let it run overnight and like this morning, find a little present.

It needs a major redesign to make the central tower extend and retract, else no point having a folding pallet. I also need to move the side boom arms in a bit more (15mm) so I may need four telescope sections which at this scale, is pushing the poor little Ender. If I can make all this work, I will make a little carry case for it, the same size and shape as the Ariane capsule. It is pretty amazing that this model itself has such a smal footprint. Here's a scale version of the inside of the Ariane payload bay.

I could hardly believe it when I placed the circle on the model, based off the info on the NASA website. Looks impossibly small...

Especially when the sunshield is deployed.

 

[Screwdriver]

Well, that's the easy part done. Now for the reckoning.

It does fold up but as I mention earlier, without an extending tower, the whole deployable tower unit is 30mm too high.

The fwd pallet clouts the top of the mirror and the pallet also hits the front of the light collector. There's a sort of folded recess in the middle of the fwd sunshield pallet which should allow the light collector to tuck in. It will be close! Same goes for the central hinge in the primary mirror boom. It should also tuck into that same crease on the aft sunshield pallet but because the whole tower is too high, the knuckle of that joint stops the aft pallet from tucking in.

Finally, the mid boom arms are 15mm too proud, they also need to telescope further into the body. There's only 35mm of body per side for the arms to slide into and a good chunk of that is taken up by the tower boom. They both need to extend a whopping 185mm ! I have a cunning plan for the last 15mm of that but I need to get the tower sorted next.

Kind of fascinating to see how much effort NASA put into the design of this amazing device. I can see why it needed to unfold in a very strict order!

 

[Dr.Al]

Looks like someone else has been at it too: https://www.prusaprinters.org/prints/109816

 

[Screwdriver]

Yes I have seen that. There are plenty out there but what I am after is a functioning model which looks more like the real thing. There are a couple of engineering modles out there which look like they were made by engineers (1/20 scale and a whopping 1/6 scale). They look like sh*t.

In reality, I am avoiding having to come up with a scale version of this:

Which is going to be horribly difficult to pull off.

I went a bit nuts a couple fo days ago and remade the entire instrument section, the big box behind the main mirror. I did an overnight session (non stop 24 hours etc.). I pored over all the millions of images out there to make an accurate frame including each spar and convert it into a model which can be printed without overhangs and odd angles sticking up etc.

I'm struggling to resist modelling the individual instrument packages to fit inside it because at this scale, detail is quite important. I might just as well do it I suppose. Gonna have to remake the big curved mirror sections anyway.

I am paying for that today but I do have a much more realistic version which should actually print more easily.

 

[Screwdriver]

I am a lot happier with this version. Rather than a crude sketch on a blank box, I have modelled the framework of the DST to be as accurate as I can get away with at this scale.

Where that tinfoil is is where I am going to stick the instrument section (the ISIM). There are only two or three big boxes in there (and they are VERY pretty!) but it also fits inside it's own frame, similar to the general construction of the entire framework. It was doing my head in trying to figure out which bit I was looking at, what orientation the picture is in and how it fits on the telescope.

Here's the ISIM with a pretty box being stuck in it.

Here's a very rare picture of the actual flight ISIM fully decorated:

On the plus side, having a relatively faithful copy of the framework means that adding the required detail, ISIM, hinges, antennae, panels etc, is much easier since thy will (of course!) fall onto a mounting point in the model. Downside is:
1. I have to remake the primary mirror section so that I can have three, more authentic, hinges (should just be doable at this scale) and
2. Having recently resigned myself to detailing the framework of the DTA, I really HAVE to do the same with the "backbone" of the primary mirror assembly.

You know. This:

 

[Seadog]

Meanwhile

 

[Screwdriver]

Version, err, four? Main structure (deployable tower assembly) is pretty much done.

I have also made the raising and lowering of the tower by installing a coarse screw inside the base (spaceship bus) and to operate, just screw or unscrew the round part of the base. Works a bit like a regular vice screw box.

I really wanted the flight instruments to be visible since I was showing off the structure anyway. The Integrated Science Instrument Module contains "only" four actual instruments: they're all there. The ISIM is a separate framework which is installed into the main frame of the DTA which also carries the mirrors

That was tricky. Lots of guesswork on sizes and trying to get the right shape from the images out there. They fit and are representative of the individual items if not quite the "look" I was hoping for. Even at 40:1 the scale does not allow me to get much closer to the "real" scale sizes or I'd be printing matchsticks.

Can't really see the instrument modules when they're installed but I know they're there.

Though they do stand out better in real life than in the photos.

I'm happy with the mirrors having made countless attempts to cut "perfect" hexagons from home made gold foil. Still need to polish the rough plastic finish before sticking them on, but there's the last test piece.

I made a sort of triangular jig for holding razor blades which rotates 60º to cut the hex.

Yeah, I know. I must be nuts but I've started so I'll finish....

 

[Screwdriver]

So close....

LOL. The cascading dimensions of a six part telescopic feature are doing my head in. Not only that, I have to calculate clearances for concentric circles vs. hexagons

It works but is not really strong enough (yet). To make the final section a respectable size, the tubes have to be virtually a single line of print (actually two overlapping). either that or the fist sections look wrong at scale. But after several weeks, I'm getting there.

Incredibly, it HAS to collapse this far to be worth doing at all. The folded model MUST fit into the target Ariane5 payload bay.

Swapped out for the smallest nozzle size possible and I'm really hoping this version will be a success. It's printing now but at a tasty 2.5 hours per batch, each iteration of design takes days to finess.

<edit> NB, those last two photos are of that actual arm sliding down to just fit into the required dimension. The issue I had with that version was the amount of hand tweaking and one or two weak areas. Plus I redesigned the mounting for the part that fits on the end to tension the sunscreen.