Paper models, photos and musings of a Paper Kosmonaut

08 August 2018

ANS - the first Dutch adventure in space [2]

Tonight it rained for the first time in weeks. While it was too hot to glue, I was working on the filmed interviews I did with the engineers that built the ANS. It was very interesting and also gave me more insights on how the satellite worked and how special this thing actually was in 1973. 
Now it has cooled down a little but still it is warm outside. But in the meantime, I did manage to do some micro-sessions to get a little further with the build of ANS, the little satellite that could. As we go further into the build, I will try to keep telling you some more details on this little nearly forgotten marvel from the dawn of the nineteen-seventies. The photo below shows where I am now, the rest of the story follows below.

The receptor of the Soft X-ray Telescope has been installed, the backside of the solar panels have been detailed. (Note: the solar panels will be reversed when finished, this side facing the other way.)
First I did some more detailing on the top and bottom plate. The edges got an aluminium coloured strip (in the real thing it is an aluminium U-beam profile.) I also added a little hole (and a piece of LEE filter!) for the coarse solar sensor on the top.

This is the bottom plate after its first round of detailing.
In the centre of the picture, in gold, the solar sensor at the top plate.
The underside of the solar sensor, showing the tiny filter I added.
Building this model gives me that kind of satisfaction you get when you constantly discover things. How things work, how they interact and how they actually were designed. For instance, take the soft X-ray telescope made by the university of Utrecht. In most of the technical drawings I have of ANS, I just saw the cone-shaped mirror of the telescope. Now I kind of knew how it worked, but I couldn’t figure out where the X-rays would go after they went through the mirrored cone. Where was the receiving end of the telescope?

The cone of the soft X-Ray experiment. It just is a cone. Inside, the wall of the real thing was vapour-coated with a mirrored surface. This was done by Philips, at their experimental NatLab (Natuurkundig Laboratorium - Science Laboratory) in Geldrop. This place was a kind of engineer's sandbox where the weirdest concepts and contraptions were invented and made. Typical of the seventies, here the young generation of engineers were stimulated to push their inventivity to the limits and beyond.
The inside of the cone was made with shiny silver coloured card.
When the satellite is aimed at a suspected X-ray source, the rays fall into the mirror cone. Because of the super short wavelength, it isn’t collected like regular light rays, it has to be collected by the sides of the telescope wall. It shallowly bounces off and falls into the receiving part. A circular shield inside the mirror cone prevents other sources from interfering.

This was made by putting a small mirrored disk in the cone, supported by five small pieces of sewing pins that pushed themselves into the walls. Luckily, it stuck at a 90º angle and at a good height.

After that, I secured the cone in place with a few drops of glue. I cut strips off a doubled piece of aluminium coloured paper to make the ribs running over the outside of the cone.

Now, after some more looking at the drawings I have of ANS, I found out, the receiving sensors were placed separately, a few inches below the cone, leaving an open space between them. In front of that open space, the fine solar sensors were placed. Behind it, through a hole in the satellite’s structure, the caught X-rays would fall on a diaphragm disc, that would bundle the rays. And below that, a sensor would measure and calibrate the rays and from there the electronic components would analyse and store the data until it would be sending it all down to earth.  Now it soon will be time to build the  main experiment of ANS, the UV-telescope provided by the university of Groningen.

At SRON, the Dutch space research facility here in Groningen, the back-up UV-cassegrain telescope of ANS is displayed in a cabinet. I am going back there one of these days to take some more detailed photos. I want to be able to take the telescope out of the satellite’s frame to show it. Oh, the luck to have this space research laboratory just around the proverbial corner and that it actually has the back-up version of the telescope of the model you are making. I’ll try and take my measuring tape along to get the dimensions right.

In the meantime, I started with the bottom part, which has a large ring. It contained the yo-yo which was used to stop the satellite spinning after its release in orbit. Very often, a satellite is spun up by the last stage of the rocket before being released to ensure its stability afterwards. After its release, the satellite needs to slow down again. Some modern ones use gas thrusters to do so, but not ANS. Mainly because of the weight it would add, thrusters were not an option. The Dutch engineers used a very simple physics principle to stop ANS in its rotation. Spinning about 180 rpm, two small weights on a long cable were released by small explosives and swung outward, thereby more or less purging the satellite of its spinning motion. The last slow rotation was corrected by three reaction wheels on board. (this was another weight-saving solution. Just three reaction wheels were spinning in an X, Y and Z- axis. There were no backups. ANS had a lot of single point failures. Meaning, if such a device would fail, the mission was screwed. The engineers knew, but rhere was no place for back-ups in ANS. it just was too snall and coud not weigh more than 130 kilograms. So all they could do was hoping for the best...

This is the inner collar at the bottom plate. It was partially black because of the satellite's orientation to the sun. This being gold card, I tore off half and painted it matt black.
This is how it is placed insie the structure. The bottom plate is not correct, however, it consisted of two loose plates of a kind of honeycomb material. Heat shield? I don't know. It was placed a little raised inside the collar, though.
The outer ring. Without the proper instructions it was a little harder to figure out how the straight parts had to be formed but in the end it explained itself anyway. Here too, part of the outside was blacked because of the sun.
Here you see one of the yo-yo weights. The other one is on the opposite side of the ring. The band around the collar are the  wires that are attached to the weights. I have some nice 8mm footage of the tests they did with the yo-yo system. They used just the collar, spinning on a table inside an outdoor masonry structure at the NLR (Dutch Aerospace Laboratories), previously used to test a tiny ramjet-driven helicopter called Kolibri. 
But that's another story.
Centre piece removed. The ring was put into place. The other side of the part was coverd with a black piece of paper.
The shield cut loose. I accentuated the riveted parts with a needle.
Bam! I skipped a few steps, I'm afraid. The center part is an odd shape, being rounded at the outermost part and square (albeit rounded) at the innermost part. I smuggled and used a cut-out circle to get it nice and round. The other side was not any problem. The 'shield' was placed on a couple of small cardboard cuttings to lift it up from the floor. For the gold coloured center of the 4th stage connector, I used chocolate wrapper.
Then I added some flat cable wiring, running from the collar through a hole in the bottom plate into the satellite's frame. I Used pieces of dental floss for this.
Then it was time for the solar panels (or PVA - Photovoltaic arrays, as the pros like to call them). The printed versions have small dark lines over the backsides, representing the flat electrical wires running over the panels. The real thing has silvery lines, so I decided to use aluminiu tape to make it resemble the real stuff a little more. It was sealed with a layer of clear coat acrylic paint.

And that is where I am now. Hopefully the next entry won't be delayed by heatwaves. Thanks for taking a look and until next time.

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