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Vostok re-entry sphere


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Hi Folks,

It has been some time that I have been either at the work bench or on the forum but am now geting back in harness and can start joining in again.

Some three weeks ago we went to visit the Cosmonaut Exhibition at the Science Museum in London...quite superb. It includes the flown Tereshcova craft Vostok 6, Vostok 1 and Soyuz TM14. Marvellous to see them ‘in the flesh’ so to speak. There are many other items also never before seen outside Russia including a real lunar lander ! What an extraordinary machine....so pleased I have Fantastic Plastic’s resin kit of it. A number of the objects had been over to the UK before in the mid ‘sixties. I shot an 8mm film of that exhibition at the time which I still have somewhere..

The upshot of all this is, that on returning home, I pulled out my Vostok file and the Nu-Bee (Revell) 1/25 kit (Do have a look at Vincent’s and Stevenichols superb re- workings of what is essentailly a very simple kit) and found myself considering giving the LM yet another hiatus and commencing on a 3/8” (1/32) engineering model of a post re-entry sphere.

The main problem of course is the paucity of real engineering info’. Still don’t know what the spere was actually made of ! Presumably duralimin, but was it spun, cast, pressed, sectioned, bolted, welded ?? Hopefuly will find out. I do have a couple of basic engineering drawings in Russian but to my great annoyance have lost the origiinal reference, but at least it gives me a start. If any of you Guys can suggest any links, publications etc. which you think may be of help it would be greatly appreciated.

Was going to begin with a mould and vacuum form but then decided to go straight to Milliput which provides the oportunity to represent the variable thickness of the sphere’s walls which was essential for orientation in re-entry. Thereafter the work will be in styrene in the usual way.

The polystyrene sphere was 60mm diam and have included a comparative scale pic by tacking together part of the Nu-Bee kit. Helps orientation as well.

Cheers

JohnB

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Hi Folks,

It has been some time that I have been either at the work bench or on the forum but am now geting back in harness and can start joining in again.

It certainly has been quite some time since you last posted ... and it's good to see you back here, John!

You've made a good start on this, but clarify something for me. Did you Milliput the exterior of the polystyrene sphere. If so, the surface looks perfect!

Keep us posted.

Thanx

Pete

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John, don't you go away, again, heheh. Excellent stuff -- we'd like to see more build shots. I wouldn't dare use Milliput unless you want to see a lumpy mess -- but, of course, the master is at work here -- you control Milliput like Poseidon controls the waves.

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Thanks Guys...really appreciated...it feels good to get back at the bench again.... Am also gradually catching up on all the wonderful work that is going on on the Forum.

Yep Pete, just Millipted the exterior of poly' sphere and then it was largely experimentation. Hopefully will be able to obtain the effect I want

At the hatch levels the ablative shield is only about 1 1/2" inches thick ( see pic ) so the Milliput needed thinning right down. With care I am surprised how thin it is possible to get it just by allowing it to cure long enough and then scraping and wet & dry paper. So thin in fact I thought it best to re- in-force it using lavatory tissue soaked in PVA and this seems to work, rather like papier- mache, serendipity it is will be also possible to model a representation of the variable wall thichness even better than just Milliput alone....more control !! Also adds a little more texture as a bonus....

For finishes am using the same technique on the surfaces of the Columbiad (sci-fi forum) ie metal powders then carbon powders ( artist's charcoal crushed up and mixed with rotten stone perhaps in PVA on a ground of raw umber oil paint. On the Columbiad this allowed a great deal of flexibility for adjustment of the finish. Needs patience though as each application needs at least overnight to dry out. So modest progression thus far and no disasters.....yet.

Thanks again chaps.

Cheers

johnB

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Still a long way to go but a great deal of fun

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Edited by johnbuck
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John,

Great job on the sphere -- I don't how you can do that with Milliput and still have a sphere when you are done!

Question: In photos of some of the post re-entry Vostoks/Voskhods I have observed The 'latitudinal' lines at the base of the sphere that you have depicted. It appears in some photos that these 'rings' are actually "stepped" rather than a smooth continuous sphere. What is the purpose of these on the real spacecraft? Is this the actual heat shield material, with a much thinner coating on the upper half of the sphere?

Thanks for any info!

Tom

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Hi Tom,

Thanks for the compliment ...... much appreciated.

Re the latitudinal lines on the heat shield : in the pics are of Vostok 6 I took and you can see that they run around the lower third of the craft being variable between 5 and 7 inches wide it looks like. They appear to be like a 'bandage soaked in a resin ? ' substance in many layers (by the burnt holes) not dissimilar to the mercury/Gemini shields in the Smithsonian. In the second pic' you can see a join in the band at the bottom set at an angle of about 30degrees which suggest to me at least that the material may have been laid on in these bands by hand. Each band has one of these joints.....interesting stuff.

The variable wall thickness in the drawings appears to be principally due to the variable thickness of this heatshield, with so much more ablative material at the 'bottom' ending at about 1 1/2" at the hatch level and above. At launch this would have given the sphere a slightly ovaloid appearance I guess.

Am devising a way to represent this on the model at the moment and will post some pics later. Looks like linen is going to work....

Am coming to the conclusion that the heat shield 'wraps up' a sectioned aluminium sphere built in pressed sections welded/bolted together......wish there was more engineering info' out there.

That is my only crit' of the otherwise superb exhibition in London, a lack of any technical info, and this goes for all the exhibits.....and the book shop attached.....pity.

Cheers

johnB

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Edited by johnbuck
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  • 2 weeks later...

Hi Folks,

am making progress on the sphere. This is proving most interesting using Milliput in this way and appears to working out OK.

Using a 2:1 mix of PVA have 'lined' the external with iron powder and the internal with aluminium powder 3 coats of each finally. Plus a little ali' foil to start the patching.

Oil paint as a 'filler' of the metal powder surface provides control for the rough and smooth area of the outside to imitate the ablation of the heat shield.

Wanted to try and give the 'resin soaked bandage' impression to the heat shield so after a little experimentation I settled on the linen idea soaked in 6:1 PVA which allowed simple cutting. Had to attach the linen to the cutting mat with spray mount to keep everything straight.

Threee layers of linen went on each impregnated with oil paint ( raw umber mixed with a tiny amount of ultra marine. This mix dries overnight and gives a good deep grey black ).

Had to have a think about the base for the hatch rings to keep everything flat so left the centres in for removal later.

Routered the Milliput to fit

Cheers

johnB

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Edited by johnbuck
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Thanks Bill for your kind comments,

that is really encouraging. Am certainly enjoying all the problems this build seems to be throwing up continuously.

Just received this from KSC this morning.....

https://www.kennedyspacecenter.com/nasa-news-and-history/nasa-news/boeing-starliner-on-display.aspx?utm_source=DecemberOverview&utm_medium=email&utm_campaign=Fall2015&spMailingID=24049165&spUserID=MTE1Njg5MDkzMjA0S0&spJobID=682041217&spReportId=NjgyMDQxMjE3S0

A scratch build for the future perhaps..... weldless ? What does this mean : pressed sheets and rivets ? If only we lived closer......

Cheers

johnB

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I would guess either machined or (less likely) printed and machined. I can ask my brother if he has any more on it's construction. Would be an interesting subject for sure. I got to see the training sister of the cupola for the ISS and it;s main body is a single machined piece. Very impressive machine work.

Bill

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Really ! That is most interesting Bill....and a well connected bro'. If you could find out....

I had no idea the cupola was a single piece of machining...extraordinary. I envy you your viewing.

Thanks for the info'

The hatch base rings are now in. Now for the difficult bit : a very shallow conical ring with with 30 holes in it X3

Cheers

johnB

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Edited by johnbuck
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Hi Guys,

A little more work on the sphere, this time the hatches. All Milliput again.

Made a negative mold from the sphere to get the correct curvature. Did try heating some 20thou styrene and pressing it in but could not get it to work so back to old faithful.

Things get somewhat dusty but think this is probably the better way to go as again it gives a lot of control and consistency. Fit of the hatches are just below the surface of the sphere to allow for the metal powder finishes inside and out.

When these are finished I can the jig up for all the holes in the hatch rims and build the styrene inserts afterwards rather than before as I originally intended. Think there may well be problems that will need solving when it comes to these as there are three surfaces to deal with. You can see from the Vostok pics ( sorry : somewhat dark as flash was not allowed. Brightening the screen helps considerably ) that the hatch surfaces have the holes counter-bored to take the the attachment bolt covers....interesting....

Cheers

johnB

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Edited by johnbuck
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Hi dekon70,

Thanks for your kind comment. Its much appreciated.

Working with Milliput in this way is certainly interesting.

I have the essentials of the structure of the sphere finished now and it always comes back to the correct position when rocked so it was worth paying attention to the variable wall thickness.

Now a question of the hatch rings.

Just for interest have popped it alongside the Crows Nest 1/32 Mercury. ( parts just blue tacked together I hasten to add ).

We all know how much bigger it was and why the Americans were somewhat dismayed by the apparent lifting power of the R7 ( was the height of the cold war of course ) but when you place one beside the other and get an idea of their respective volumes......... one can really see why.......

Thanks again,

johnB

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