Proton-M experiment

[5thDay]

I have had to scale back my builds significantly for a few reasons and sadly that ment mothballing the "big" Soyuz project for a while. As a positive, having a 9ft rocket shell hanging from my ceiling is a piece of decorating I am really proud of.

This last week however when inventorying and cleaning out my tubes I had some ideas I wanted to send skyward. Below is a basic description, some features and a question of opinion regarding my "fin" idea for stage 2.

The Proton never really impressed or inspired me much until I considered it as a build project. The psuedo-booster look however is more interesting when considering NOT tracking 7+ objects descending and when the 6 engine cluster can easily be treated as a basic first stage of a simple 2 stage rocket. It also put to good use the variety of thick walled tubes I have of various sizes that telescope with other tubes I have accumulated.

Stage I core is made from 68mm 4mm wall tube with 6 "booster" tubes arranged around it. Stage 2 core leading all the way to the shroud is 59mm tube that is also 4mm wall. These sturdy tubes are nice to work with but don't make it into material selection often due to their excessive weight. Each stage joins the stage above it via a thrust ring or collar in a 'push up from underneath' concept that I think will help immensely with drag seperation and nosecone ejection. That will be looked at closely during first test flights with a dummy load in stage 2 and nylon screws holding the stages together.

My flight plan ultimately is launching with six E12-4, clustered and mounted into the external tubes via 29-24mm adapters and engine blocks. Utilizing an extremely simple 556 timer in monostable configuration, stage 2 hot stage starts a H180-10 just tenths of a second before the E cluster falters in accelerating. This checks a couple boxes for me in a progressively more challenging list of flight profiles to complete. BP to APCP staging, cluster as stage 1 and airstarting a HP motor.

As is often the case with scale or near scale models (this is not scale accurate or the same scale as my smaller Soyuz)... I had to consider stability of the entire rocket and of stage 2 alone. Gas Stabilization is something I want to attempt eventually but not at this impulse level and acrylic fins would be overkill for this sized rocket IMO. What I have come up with, I think is clever, and simulates well in OpenRocket.

As I try to demonstrate in the photos below, I want to attach the first stage nosecones to the second stage external 'thrust collar'.
After separating the nosecones would remain and function as fins for stage 2. Stage 1 would have 3 of 6 tubes loaded with small parachutes that will deploy on descent with their ejection charges. Having the first stage central tube open gives me more confidence in the airstart and I simply like the way multi-chute descents look.

Currently the nosecone/fins are simply HappyMeal material but will be fiberglass coated to hold their shape. I did consider leaving the nosecones attached to stage 1 tubes, but having them pass through rings attached to stage 2 which would function like short tube fins but, the leaning in geometry of these cones didnt work well with that idea and I have a suspicion that I will get more CP movement with cones. Who cares to offer predictions or thoughts on this design?

**My baby Soyuz came out of storage for repairs in order to fly the same day as the Proton. It was never finished as a staged or clustered rocket and only flew once on a single F72 as a stability test. I may add a single C motor to each booster just for effect but will likely keep everything connected as a single stage rocket. Photo for size and detail comparison of my Baikonur fleet added last.

 

[5thDay]

I build everything for my rockets. In fact whenever I encounter dimensions given in BT units I often have to look up the conversions. 24mm medium wall 'straight' tubes are the ones that come on rolls of masking film used in painting or Reynolds' Wrap 150ft rolls. One area that always gives me problems are centering rings!!

This is why I am so happy to share the 'cheat' I found today. There will be probably no other rockets this will work but... if anyone reading this is working on a Proton and dreading carving 12 centering rings, consider this.

The MMTs on a Proton stage 1 are not canted and are anterior to the rocket. A "centering ring" holds the MMT in the center of a larger tube and keeps it straight. On this rocket however I found:

The core tube is straight.
The six "booster" looking smaller body tubes are straight.
Gluing the MMT directly to that same alignment line secures it and positions it where it has to be.
My Centering Rings would actually be "Off-centering crescent moons"

Once the MMTs were glued and placed I put small pieces of pool noodle foam inside the booster tubes to hold them down (clamps basically). I then put closed cell foam disks into the MMT to act as plugs. With the bottom sanded flush I placed some tape over the bottom and then sat the assembly upright on a paper plate and poured resin into each booster to 1/4". Here I reached for my 2 part expanding foam and of course one part was rock hard

Not discouraged I cut several crescent moons out of foam and pushed them into position with skewers. After all were in position I added foam glue and let that set. Finally I added another 1/8" of pourable resin on top to cap it and give me a more typical 2 disc MMT arrangement.

Missing quite a few steps worth of photos but when I had to change plans due to exposed/bad expanding foam I de-prioritized documentation. Photo 3 is after a light sanding of the bleed through I had at the tape lines.

 

[bjphoenix]

Very interesting. I need to build some of those offset cones for side pods on my current build.

 

[5thDay]

bjphoenix, if your side pods are permanently attached to the core body tube like the Proton's are I would make this change to my step process. If not, there is probably no reason these offset motor tubes wouldn't work fine and this change wouldn't apply.

I needed to use extra large fillets to get the 'booster' pods to feel firm. If I was to build this again (likely upscaling) I would glue the MMT to the core first.

--------‐----------------------------------------

When attaching non-concentric tubes together like this, there is not much surface area for glue to bite into. Use the following steps to correct if using a pourable resin style rings.

1. Using basic fin placement methods for marking lines evenly around the tube, extend those lines with a straight edge for the length of tubes being applied.
2. Using a small piece of angle, mark the inside of the MMT at top and bottom.
3. Mark a straight line down each pod's tube on the outside.
4. Use scissors or a sharp hobby knife to slit the pod tubes along the lines drawn in step 3.
5. Test align the MMT using the mark on their ID to the lines of the core tube OD. Apply glue slightly wider than the contact area.
6. Allow the MMT glue to bite and then quickly stretch the slit pod tubes slightly as you put them into position from either the top or bottom.
7. Align and bring the slit walls of the pod tube into the setting glue fillet. If you come in at the perfect angle you will split the fillet putting glue on four surfaces with a single fillet.

--------------------- mmt
+++++++++++++++++++++ glue
--------------+++++++--------------- slit pod
+++++++++++++++++++++
------------------------------------------- core tube

 

[5thDay]

24mm Retainer (Nozzles)

Sharing a pretty cool and easy rocket nozzle idea I first implemented on my BIG Soyuz rocket. On that model they were to scale (1:17) so will be large on models much smaller but if accuracy < looking cool sometimes, you may want to check this out.

Before going further I want to state these nozzles are not intended to be functional and during flight end up ablating away to roughly half of their height with BP motors. There are many posts here discussing any potential improvement to BP motors of adding a more elaborate nozzle and the consensus seems to be no.

-----

I experimented with various brand 16.9oz., 20oz and 2 liter bottles. Each brand has a slightly different shape and expansion rate of the neck so find one you like first. Coke 16.9oz bottles worked for my BIG Soyuz so that is what I ended up with a lot of and are pictured below.

I have experimented with using these on 18mm motors as well. That size slips through the ID of the throat and allows for not cutting the threads off but instead gluing the cap to the rocket and epoxying the threads and nozzle to the side of the paper tube motors. You need to cut a hole in the cap obviously so the motor can recess into the airframe.

For 29mm motors I found that 1gal milk jugs are the perfect size to do the same however the material is very soft and pliable. None of these were ever flown.

 

[5thDay]

Only a few items remaining before a test flight.

Paint black bands on stage I fuel tanks.
Tap thread holes for retainer plate screws.
Attach launch lugs.
Make and attach sustainer recovery chute & cord.
Complete 556 timer circuit for airstarting the sustainer & producing the locator beep.

Everything else is almost ready. Three 8" chutes are already packed into stage 1 fuel pods 1, 3 and 5. I made a clip whip specifically for this model so that avoiding shorts when attaching ignitors inside the nozzles. Ignition will be a touch unorthodox as the battery power is fully onboard for stage 1 and stage 2. The launch controller just sends the start command which I am doing to have a ON -> delayed ON monostable configuration of the timer circuit. The other option would be a relay with the sustainer ignitor on NC contacts which is open by the coil being powered until it isn't. I avoided that route for pad safety and for shock concerns about using mechanical switches.

Six E12-4 handle the first stage for 2 seconds before the DIY H motor in the sustainer fires. Really putting some trust into those nosecones working as fins. Large launch area and safety distances given stability concerns as well as potential for my motor casing to burst.

 

[5thDay]

Experiment results are (mostly) in. Flight was not successful, and I can not check off all of the goals I wanted to accomplish. It was a fun launch where all safety devices worked and the six E12s made for an exciting takeoff.

Second stage did not light. I installed a rip cord shunt where the rocket at 100' would have a slip of paper pulled out of a set of clips. The rip cord (braided line soaked for 3 hours) burned through on takeoff. Shunt remained in and prevented firing.

The Proton-M, as I modeled it is not stable and without canting of the six BP motors I had thrust instability towards the end of their burns. I was somewhat surprised by this as the Soyuz-FG I found to be stable as-is when modeled at a similar scale. Perhaps with canted MMTs the uneven thrust problem would have been lessened. This somewhat surprised me as I believed Estes motors to be fairly consistent. Perhaps that consistency is limited to E9 and does not extend to E12.

My soda bottle nozzles were a win and ablated as hoped. Cool looking at take-off but no effect during flight except perhaps a had more grey to the smoke trail.

Not enough curiosity in the stage 1 nosecone as stage 2 fins idea to repair the rocket for flight. I plan to do only enough repairs to reattach the pieces which separated on landing and proudly display this with other learning experience rockets.