(Yet?) Another Soyuz Build

[5thDay]

As the title suggests, here is another build thread for my next R7 family build. Before anything else is typed, there are some really amazing threads on these forums for Soyuz building and reference. The gentleman who built the 1:50 and later 1:25 scale models (thread links to follow in later edits) did amazing work and other members have posted great detailed close up photos there which I reference often.

After a near scale test flight of a poster board built Soyuz I decided to spend my my time building the rocket I want to fly. That is a 1:15 scale (10ft) model. I landed at 10ft by considering where a "huge" rocket begins for me and I think the math would be very grounded for me.
Material density properties and a little thing called "The Safety Code" led me to back down to 8ft (7ft proper because who really counts the escape tower rocket height anyways?) in order to stay a comfortable distance from maximum weights.

More to come as I post additional replies and in complete honesty I don't want to list out a dozen features I hope to fly with only to pull them for one reason or another.

 

[5thDay]

Least favorite part complete!

Two of four crafted in order to see the total width and height of the first stages. I can pick up the fine tuned templates tomorrow and cut poster for the remaining two quickly. The upper half models much much easier so within the week I should have the skin finished so that I can tear into it and nail down some flight functionality.

 

[lakeroadster]

Man you're fast, that's a lot of work for 7 minutes! just kidding.

You state:

I can pick up the fine tuned templates tomorrow ....

Is somebody else cutting the templates?

Tell us more about the process.

What thickness materials are you using?​

What motor powers this bird?​

 

[5thDay]

Is somebody else cutting the templates?

Pattern would have been a better term. I am making all of this myself and wanted to imply that:
- I can pick this (back) up tomorrow when my son allows me build time and create two more boosters.
- Fine tuned relates to my current process and how when trying to get these transitions shaped there is a lot of fit check, trim & repeat going on.

This material loves to buckle and wave into creases when rolled into cylinders and even more so one transition rolls and tight rolls (below 90mm) so there is an art to that which I am still working out that involves damp rags and stretching.

In post#2 first photo there is the pattern for the booster nosecone on the carpet next to the round sections for the booster lowest sections.

This building phase uses Dollar Tree $0.50 per sheet poster board (0.36mm) that has a smooth slightly waxy side and a more porous side that feels like card stock. All skins are butt jointed single layer using rubber cement. I also use 5mm white foam board from Dollar Tree wherever I need to hold something round until the next section is added. Those can be seen in the first post photos but are removed now that the skin holds itself to shape. The smooth side takes and releases standard (cheap) masking tape easily without damage so you can see a lot of little pieces here and there holding things into position for me while cement sets.

Rubber cement so far is the best adhesive I have found for this construction but I am experimenting with other things to find something that won't wave the paper yet dries harder.

The end result is an entire rocket outer skin made with 0.36mm paper in a single layer with no couplers or overlaps inside or out. Weight was a big concern when deciding on this size build. I have a few reinforcement options in mind but top candidates at this time are:
-blow molding HDPE or PETE into the interior of the skin to an average thickness of 0.5mm.
-Casting large sections of the finished rocket into semi-rigid silicon half molds for future resin molding (including details created in paper on the exterior)
-wrapping the exterior with custom made "sheets" of melted and pressed 0.5mm HDPE. Each rectangular section would be attached to the others in a patchwork just as actual sheet metal would be applied to a Soyuz.

For flight, it is too soon for me to start picking motors but I have infinite options. If I use motor mounts equal to the bell nozzle scale diameter stage 1 and 2 take twenty 29mm fixed motors with twelve more 13mm steering motors and stage 3 takes four 38mm. Those counts do not include direct staging ideas for Block A.

Doing flight sims isn't really an option (though I made some elaborate attempts) so I plan to design a tethered method for doing first stage configuring testing. I want booster separation at a fairly low altitude because even though it is not realistic, I want to see the cross. Almost certainly, there will be mix-matching and hot staging going on to give me the flight I am looking for. Apogee Medalists look like a great option for center core stage 1 motors. Tim @ Apogee Components doesn't recommend them for heavy rockets. I would reach out to him with my ideas and photos when I get to that point.

Test flight of the smaller painted Soyuz seen in the first photos did just under 1,000ft. Similar yet heavier construction, that model weighs 504g dry and was launched on a single Flight Star F72-10T. With that thrust, the need for more weight was obvious and is why I started this larger build.

 

[5thDay]

Options.

With my custom flight controller I can add as many separate ignitions as I want but sketched them here with direct staging to save some additional channels.

As long as I have intial jump to get off the rail at a safe speed, the name of the game is to continue burning the core stage long enough to let the boosters separate.

 

[5thDay]

Had to reroll some tubes I wasn't happy with and decided I liked that material for transitions enough to redo all 4.

Sustainer progress is coming along and the body tube sections are shown in approximate position they will be at after I do those transitions tomorrow.

I am considering fiberglassing all of it instead of the HDPE options I was looking into. It would put me into HPR territory but that just means waiting for a club launch day.

 

[OverTheTop]

What about fiberglassing with "tissue", a very thin fiberglass layer over the top? Might get you strength without excessive mass.

 

[5thDay]

Thanks for the question and suggestion. I will need to do some forum searching for 'tissue' to see exactly what materials you might be referring to, what they weigh and where I can get them. In researching fiberglass coatings, I came across 1/2oz weave but the concensus seemed to be negative. I don't know if I specified well enough early on in this thread but I am not really constrained by anything on this bird and developing it as it comes together to meet my flight plans.

My first flying model as a kid was a P40 WarHawk. It had a Balsawood fuselage with rice paper skin. That has been the driver of this miniscule outer shell construction I am doing. A feature of HDPE I like is the bounce-back properties. 20oz Mountain Dew bottles are 0.36mm as an example.

 

[OverTheTop]

A couple of examples:
http://www.reginaglass.com.au/product-applications.htmlhttp://www.nivitex.com/fibreglass-tissue.html

 

[5thDay]

Starting to look more like a rocket.

Ended at this point for the night when I noticed a problem. For scale, my math told me the final height (minus engine nozzles) would be 1/2" below my ceiling from the carpet.
The upper stage is lower than it should be in this photo but in final position the escape tower is about 1/2" too tall to be placed. There is an error somewhere and I am not lucky enough for it to be in a tubular section...

I'll hunt it down tomorrow, get the tower added and post some weights.

 

[Cape Byron]

Kudos. Anyone scratching a Soyuz gets maximum cool points.

 

[5thDay]

I've decided to also scratch the launch support tower from Baikonur Cosmodrome as well. I will need a rail to launch this tall of a rocket and the way I would stand that up vertical made me think, "why not transport this rocket to the launch field on a dedicated trailer? Why not have the entire umbilical, launch clamp and service tower system modeled? "

It will be nice to model something that doesn't fly and where weight is not so critical.

Project totals to this point:
Rocket 603g
Cost $5.50

 

[5thDay]

I have been busy with other things and have had limited time to build.

Research continues on Gargarin's Start (pad 1/5). I have perhaps 50 close up detailed photos saved showing it from many different angles which is important when attempting to scale accurately using the FG pictured within.

220mm Linear Actuators acquired for the service tower and wired to verify placement idea.
Telescoping "hidden" launch rail idea showed promise on much smaller scale launches. I may start a stand alone thread on rod/rail options as 8020 is grossly out of the budget as I am considering 25-30' of guided lift off.

Fiberglass coating critical areas, finishing putty over ugly seams and the start of surface detailing has begun. I have even put a few coats of paint down to help keep myself excited and motivated.

 

[OverTheTop]

I have flagged this series of books in other threads and I'll add it here as well, in case any Soyuz aficionado's have missed my other links. I am not sure which volume has the majority of the information on the "Semyorka" R-7 that we know as Soyuz now. I guess you will just have to download all four parts to the Rockets and People book and find out .
https://www.nasa.gov/connect/ebooks/rockets_people_vol1_detail.htmlThis is a great series of books, well translated and a different perspective on their space program, written by somebody who got in at the ground level and eventually became the Chief Control Systems Engineer for the rocket program there, the revered Boris Chertok.

 

[wrad]

I need to get myself a proper wall poster printout of the Soyuz blueprint, Its such a great resource, but looks awesome as well!

600g at this scale! foam board rely is awesome stuff.

 

[5thDay]

The one on my wall is a actually 49 sheets of 8.5×11 copy paper. I used GIMP to expand the original image to the size I was building for a 1:1 scale printout. When printing a .pdf as a poster in Windows there is an option for cut marks which gives you small lines at the margins to align cuts. Even with that to aid, getting a flat poster is a preview of how challenging working with paper accurately can be.

A quick note on scale:
I mentioned something was wrong or off when I stacked the stages and ended up with more rocket than I should have had. This came from 2 errors. The physical error was that I intentionally left the last piece (heightwise) of Block A long. This is the area before the latticework that I thought I might leave solid and cut the lattice from it later. I forgot I did myself that favor and when moving up to stage 3 I put another gap in.
The other contribution was the fault of my elementary school not owning a meter stick. I am a metric system convert and am comfortable at shorter distances comfortable with working in mm and cm but i can't visualize m. To this day, I remember my teachers describing a meter as "about the same as a yard." When i hear something is 50m my brain tells me (meter --> yard*3 = ft) roughly. Because I was aiming for a finished height using a bad conversion but an accurate scaling method; measure wall print and multiply by 1.933, I got a completely accurate scale rocket in an oddball 1:17 scale.

The 600g was admittedly overly ambitious. As a mold or a blank only the shape maters but midway through building when I decided to fly what I was building the single layer construction has caused me a lot of problems, time and weight. Much of the skin has had to be reinforced or rebuilt and something as simple as primer has buckled large areas to the point of needing more paper layers added. If I didn't have skeletal structure plans already I would start over with 2 layers everywhere and 3 layers on stage 3 and up targeting 1,200-1,500g.

 

[5thDay]

Other than the giant 45 degree mistake that I noticed first when taking these photos, I am pretty happy with my plans and progress.

The idea with the motor mount configuration is to have a plate riding the outside of the MMTs between the forward centering ring and the mid centering ring. Connected to that plate will be the booster attachment hooks. At ejection charge the bottom of the boosters are released while 2 longer burn motors continue firing and later eject normally into Block A as a backup to drogue if my apogee detection fails.

My mistake with the rotation of the center 4 motors is annoying because I decided to make the aft centering that shape for aesthetic reasons only. At least I caught it with foam and not plywood later.

 

[5thDay]

Booster ejection method.

The middle-forward centering ring (piston) functions like a piston and is held down close to the middle-aft centering ring by very light springs around the longer MMTs.
The ejection charge of the shorter MMT presses the piston up as shown in the second photo.
Attached to the piston disc are the 4 hooks that hold the bottom of the 4 boosters. The geometry of their linkage first releases the catch and with continued motion pushes the boosters laterally away from the center core while the motors in the longer MMTs continue thrusting.
My demonstration photo used E12-4 and E12-6 to communicate my intended event timing but I obviously understand that burn duration + delay time in total time is what my idea is based on. Something like two D12-3 and two E9-# is what will likely be loaded for my first flight.

Questions:
What direction should I vent the chamber? Sideways or downward.

Sizing of those vents starting ideas? Too large of vents and i will either slam the piston too hard or have it come back down too fast before the boosters "flip" backwards away from the core. Vent holes too small and ... best case scenario is the motor rear ejects on me and worst case involves lots of rocket anatomy debris.

Double question:
What is the name of the effect created by having a very long nozzle? I made the longer MMTs capable of holding two E length motors. If the upper of the two is retained and the lower is rear ejected, what thrust changes can I expect.

Scarier alternative, if both direct staged motors are retained and the MMT is made adequately strong; can the upper motor's nozzle exhaust be forced down into the spent motor casing and out of that nozzle again?
Something about that configuration screams safety concern but I don't have a name to call that configuration in order to search for it.

 

[wrad]

Its still mighty light for its size regardless!.

I like the idea for the staging, will be great to see how it works.

The name of the effect is the Krushnic effect. I believe it comes into play when the motor is recessed into the body tube by at least the same distance as the tube diameter. you can stop / reduce it however by adding venting holes into the body tube at approximately the same height as the upper motor nozzle, so that air can get into the tube and equalise the pressure.

 

[5thDay]

What motor powers this bird?​

I redesigned (again) to gain more options for motors. Block A now has four 29mm mounts. Now decision yet on what stage 3 will use but by the time the bottom half of the stack finishes I should have plenty of altitude and wouldn't likely be able to see much more.
Flight total: 24 motors
Launch: 20 motors (2 composite)

Core: two Apogee Medallists F10-8, two Estes D12-3
Boosters Total: twelve Estes E12-4, four Estes E9-6
Boosters Each: three E12, one E9

Stage 3: four Quest C6-0, four Aerotech G80-10 or perhaps my F101-15... (I would add a safety check in my airstart electronics of course if I go that route!)

Stage 1 boosters and core, stage 2 is the core continuing on using the F10s after booster separation. Boosters will come down on streamers for help recovering. Stage 3 air starts around 6.5 seconds after launch. Stage 3 motors will either be very long delay or vented so that my electronics can fire the drogue and release the space craft at apogee.

Timing wise everything looks good and stages well with just motor burns and ejection charges handling the timing which saves code on my electronics. One problem remains with this configuration:

The F10s I have are 8 second delay and I don't get any coast time by hot staging Stage 3 and may have to work out a way to deploy a chute sooner on the falling core. Any helpful ideas?

 

[5thDay]

Completed the design change and upgrade to 4x 29mm motors for the core stage. 2x Apogee Medallist F10 and 2x Aerotech F20s. The boosters are all still 24mm with MMT long enough to stack 4x direct staged D boosters under 4x E9/12s. Little chance I will actually need that much thrust and once my final weighs are firm I imagine building sixteen 24:18 adapters to fly good smokey Quest B/C motors that only need to provide enough thrust to neutralize their own mass and drag.

It took longer than I thought it would to get the piston sliding perfectly and to recess motor retention internally. The nozzles will ablate but their base will remain to work as a retainer.

During the time I had not yet made up my mind about inner mechanical function, I worked on cosmetic item fabrication. I went with neodymium magnets mounted in the piston to handle booster separation instead of levers or hooks. In tests it works very elegant and the transition from attractive to repulsive forces acting on all 4 boosters is uniform, smooth and quite powerful.

Work on the pad has finally gotten underway but I believe I will keep those photos under wraps until launch. That way the Soyuz itself remains the topic for your comments or critiques which I am grateful for.

 

[5thDay]

Secondhand aluminum Golf Bag Cart purchased @ a swap meet for $2! Neighbors are getting excited for a launch!

Couple more assembly photos showing the 29mm core and 24mm booster MMTs. I will need to lighten these quite a bit so will be swiss cheesing their tubes after putting a wrap of fiberglass on them: add weight in order to remove more than that... Total mass is still of little concern but CG is and is why the top half of the rocket is coated more heavily in glass.

Yup, I waste time and materials during builds with things like painting the final color scheme over and over despite needing to add more details later. It helps to keep me excited.

 

[5thDay]

Stage ejection demo

Pardon the tape and paper but outside of clear tubes there wasn't am easy way to mount the magnets as they would be mounted inside the boosters.

The slide (painted red) has 4 magnets mounted to it, one for each booster. The boosters have two magnets each. One attractive and one repulsive. Not shown here is a pair of springs that hold the slide in the downward position.
At ejection charge of the two shorter MMTs, the red piston is forced upwards so that the magnets now repulse the magnets in the boosters and push them away.

The drag on the boosters and this firm nudge which happens to all 4 at once should give me a good chance at a cross.

 

[5thDay]

If you noticed the O-Ring on the piston that is plan B. Should I need it, the air compressed on the forward side of the piston can be vented to give each booster another nudge while the magnets detach.

 

[aerostadt]

As I recall F10's are end-burners (there is a small slot in the end of the grain) and hard to ignite.

 

[5thDay]

As I recall F10's are end-burners (there is a small slot in the end of the grain) and hard to ignite.

I have 24v available at the pad which is needed to move the linear actuators that connect to the service tower. The 2 composite lighting will release the launch clamps and ignite the 18 BP motors.
The F10s lighting the BP will either be via flash pan or by electronics that detect they have lit.

 

[5thDay]

Everything but mothballs...

Most recent photo of the 1:17 scale Soyuz build. The line holding this up is lightweight fishing line. This I believe was just under 2lbs the last time I weighed all pieces and added it up.