My first supersonic rocket - STREGA

[verex]

Hi everyone, this is my first topic on this forum.
My name is Damian and I'm from Poland - middle country in central Europe. I'm 17 and I am building rockets for 3 years in Polish Rocket Society. Sorry for my broken english, but I don't use this language everyday .

I would descript my first supersonic project. STREGA is my first aluminium rocket and I designed it for supersonic flights on M-class sugar motor. The rocket has 80mm diameter and I designed two concepts:
1. Subsonic - small J-class motor for subsonic test flights. The fins are TIG welded to the motor case on nozzle part. Fins were cut from 3.0mm EN AW 5754 aluminium plate.
2. Supersonic - large M-class motor for flight to 6 kilometers (19.685 ft). The fins (from 4.0mm EN AW 5754 aluminium plate) will be welded on 84mm EW AN 6060 other tube outside the motor.

Nosecone (6:1) was making from glass fibre and epoxy.

On board are:
- Altimax G2 SD altimeter
- UWS5-51 (something like DentaMag) - 1st chute deploy system
- GPS/GSM tracker
- sound locator
- camera (I don't have onboard video - chinese cameras don't like freeze )

I flew subsonic in 19th January. The apogee from simulate was about 800 meters high. But the weather was very difficult. Wind was blowing 25 km/h. My rocket had 0,5 calibre of stability (in subsonic version) on the launchpad and 0,8 calibre on 140 meters (crash height).
My rocket was overturned, which resulted of 1st chute deployment. After few second Altimax deployed main chute. Probably rocket was unstable .

The rocket landed nearby, so I didn't need GPS

Fotos: https://picasaweb.google.com/102508991714628546910/STREGASupersonic
Videos from launch:
1. https://www.youtube.com/watch?v=yLlW7M_JZJo
2. https://www.youtube.com/watch?v=utIef_-a2tM

But the rocket is in one part, so after turning new tube I would launch again

I'm actually turning M-class KNO3/Sorbitol motor. It will have 5,1 kg propellant in 8 beats grains.
Data from SRM:
Max thrust: 2371 N
It 5896 Ns
t 2,65 s
Isp 118,1
Class M225

In attachement is a project of aluminium&graphite nozzle. I haven't seen on this forum this solution.
I will paint the rocket next mounth.

I hope my english is good enough to understand this post .

Greetings,
Damian

 

[CarVac]

It looks like you need more stability... you may have hit wind shear.

 

[verex]

Yeah, I think so. In next test flight I would add extra weight to nosecone (and choose better day to launch ).

 

[Aksrockets]

Did you simulate this rocket to make sure your stability was alright before flight?

Very nice work! I've considered TIG welding the fins directly to a casing, but was worried about the welds creating imperfections that could potentially weaken the case. Any bit of undercut and I'd consider a casing unusable.
Any close up pics of the fins?

Keep up the good work. I love seeing more youth work on high performance rockets.

Alex

 

[bobkrech]

Nice looking rocket.

You want a minimum of 1 caliber stability for your rocket. In a cross-wind you want more as the CP moves forward and reduces stability. You might find the following references useful.

https://www.apogeerockets.com/Wind_Caused_Instability

https://argoshpr.ch/joomla1/articles/pdf/sentinel39-galejs.pdf

If speed is your goal, I believe larger fins would be a better way to move the CP aft. Nose weight to move the CG forward makes the rocket heavier and will decrease Vmax.

Bob

 

[verex]

Yes, I'm projecting my all rockets in Open Rocket. In OR my rocket has 0,5 calibre of stability on the launchpad.

More photos you have in Picasa gallery: https://picasaweb.google.com/102508991714628546910/STREGASupersonic?noredirect=1 and I will take a new fins photos tommorow.

The fins are welded to part where is a graphite nozzle. This part of case don't work under pressure. The case after welding was a little bit deformed, but after turning is ok. And it works .

Bob, thanks for advice. So I will make a new case with bigger fins .

 

[Aksrockets]

Even though you might have .5 cals at mach .3 or whatever Openrocket simulates at, you don't necessarily have the same stability at higher velocities. CP shifts aft, then forward again as speed increases.

You can use Openrocket to simulate this.

Analyze > Component analysis.

Here's an example with an I motor altitude rocket I just designed.
It's stable at M .3


But unstable at M 2.2


You can use Openrocket to create a stability vs time graph of your rocket.


Good idea to only weld over the nozzle area. I had not considered that. Warping is always a problem with aluminum.

Alex

 

[verex]

Alex, I took some photos of the fins. Thanks for your screens. I didn't know about this option in Open Rocket.

Inside the tube, where wall is dirtier, is a nozzle part. This part had to be turned, because it was deform after welding.



In Friday I would have first parts for the large M-class motor so I will share more photos soon.

Damian

 

[Issus]

From most of my experiments with supersonic, you need at least 1.7 stability in OpenRocket for anything over mach 1.5 or so. Try to maintain at least 0.5cal when the rocket is going it's fastest.

 

[TopRamen]

That's pretty cool. I'm envious of the way you folks from other Countries build your Rockets out of "Real" Materials like Metal and make your own Motors.

 

[verex]

That's pretty cool. I'm envious of the way you folks from other Countries build your Rockets out of "Real" Materials like Metal and make your own Motors.

In Poland we don't have Tripoli and other systems, so we must build our own motors. Also we don't have rocketry shops with materials, so we are using anything what we may buy in shop and Internet. A few people from our rocket society preparing hybrid motors, because it's 100% legal. Solid motors aren't covered by the law.
Actually I am also working on my first hybrid. I think the motor will be useable in July.

Thanks for compliments, but I think you have better situation. In USA and other Tripoli countries solid motors are legal and there are in the shop. We don't have opportunity to flight over 15 km (~49 200 ft), because our military training grounds are too small. We are trying to get a permission to flying from the Baltic see or from coastal areas, but it isn't easy.

 

[verex]

So let's start!

Actually I have the nozzle, bulkehads and the fins-tube. Fins and the motor case are in progress . I must drill the holes for screws in the nozzle, bulkheads and in the motor casing.
I have two bulkheads - one will flight and there is a longer than second bulkhead, because that have a coulper with other parts of rocket. The second bulkhead are smaller, because there will use to ground tests and other HP models

Some photos:

2017 Aluminium nozzle with graphite throat:


Exhaust part of the nozzle:


Fins 84mm tube:


All finished parts:


And view of STREGA from Open Rocket. That's cool!


Other parts will be finished tommorow.

 

[verex]

Mass of one fin: 73,7 g
Mass of flat bulkhead: 371 g
Mass of fins-tube: 195,6 g
Mass of the nozzle: 651,3 g
Mass of the bulkhead with coulper: 549 g
All fins weight: 221,3 g

Fins are very sharp. Like a shaver

Ok, some better photos:

Fins

Bulkhead with coulper

Flat bulkhead

Nozzle:

So I must weld the fins and make a motor case. I must buy new, longer aluminium tube, because this one is too short.... However I have bought 120 cm tube, but they send me 106 cm :/ .

P.S. Only I don't see attached photos in previous posts?

 

[Andre]

Looks awesome Damian. I'm allready looking forward to see this bad boy fly at FM 2014.

Andrej

 

[Issus]

It looks good, however it also looks really heavy. Have you considered making it from lighter components, or less bulky? You'd be able to fly a much lighter rocket which would make it go higher/faster

 

[rocketjet787]

Yeah, I think so. In next test flight I would add extra weight to nosecone (and choose better day to launch ).

Yes knowing when to launch is just as important as knowing how to launch.

 

[verex]

@rocketjet787 Yes, weather is one of the most important things.

From 27-29 March I was in Pomeranian Scientific-Technological Park in Gdynia on International Competiton of Young Scientists E(x)plory. Many copanies and institutes are interested in rockets, whose can explore our atmosphere. I'm very glad that they help young people (like me ) developing our projects.

It was my rocketry stand on this competition:


I also have an opportunity to visit and develop my project in association with Space Research Center Polish Academy of Sciences.

Actually I'm turning tube to M motor and other parts this rocket. I think in next month I will test this motor on a new test stand.

P.S. What are you thinking about soldering fins to the tube? In Poland I have "AlumWeld" set and it's very cheap. The binder resitant 370 Celsius degrees. More info about it here: https://www.alumweld.pl/index.php/kategoria/lutowanie-palnikiem
Does soldering is better than TIG-welding? TIG-welding probably deform my tube, but it is more resistant for high temperatures. Soldering don't deform tube, but it melted in 370*C.

 

[Issus]

I know of others (Mike Passaretti) who have brazed fins on, it handled a minimum diameter N5800 - the first to ever survive. Is this the same as you have? https://www.durafix.com/

See here: https://www.ausrocketry.com/forum/viewtopic.php?f=10&t=3593

 

[verex]

I know of others (Mike Passaretti) who have brazed fins on, it handled a minimum diameter N5800 - the first to ever survive. Is this the same as you have? https://www.durafix.com/

See here: https://www.ausrocketry.com/forum/viewtopic.php?f=10&t=3593

Yes, that's something similar. But... "the first to ever survive"... Are you trying to tell me that other brazing fins didn't survive supersonic flights?

 

[CarVac]

Yes, that's something similar. But... "the first to ever survive"... Are you trying to tell me that other brazing fins didn't survive supersonic flights?

That was the first-ever minimum-diameter rocket to survive the N5800.

Not the first brazed-fin rocket to survive (though I haven't heard of the technique being used before in hobby circles).

 

[verex]

Oh, thank you!

So I think that I bought this brazing set and I will try this solution in my rocket. But I want to test how much kilograms brazing fin can stand, before I using it.

 

[mikemech]

I don't remember the exact temperatures, but brazing rod melts at a much higher temperature than solder.

 

[Issus]

Oh, thank you!

So I think that I bought this brazing set and I will try this solution in my rocket. But I want to test how much kilograms brazing fin can stand, before I using it.

https://mikepassaretti.com/ddt/Taming_the_N5800_vFINAL.pdf

Mike detailed his testing of the fin using a sample piece and weights in here. You might want to try similar to ensure your braze/solder is going to be up to it - i'm sure it will, but its always good to be sure when sticking a M motor in something

 

[verex]

I have already my M-class motor done!
The lenght of the rocket in supersonic version is 2433 mm.
I will go to Warsaw tommorow on 50th anniversary of European Space Agency with my rockets, so I will share more photos tommorow.

We have local rocketry club meeting last saturday and we launched 12 of our rockets (low, middle and high power).
Video made by local TV:
[video=youtube;sB63Xd00zkE]https://www.youtube.com/watch?v=sB63Xd00zkE[/video]
On the video I was saying about scientific purposes of amateur rocketry in Poland and little bit about rocket launches this day.

More photos tommorow .

OH, I forgot share a photo!

 

[scsager]

Damian - Mój polski nie jest tak dobry - tak, to jest to, co mam do powiedzenia - :grin: :clap: :headbang: :wave:

 

[verex]

I was in Warsaw yesterday. Some photos here: https://picasaweb.google.com/102508991714628546910/50lecieESACNKWarszawa11042014?noredirect=1

More info coming soon.

@scsager Polski jest dość trudnym językiem dla uczących się go obcokrajowców .

 

[verex]

I have a question.
I bought an epoxy glue VersaChem Steel Weld Epoxy to make a fillets, but I'm not sure because I've never used this glue. Is it ok to make a fillets? Is anyone used this epoxy glue in supersonic rockets?

On the reverse is an instruction and there is a note: "Not recommended for use above 250 Celsius degrees (121 Celsius degrees)." - So... What temperature is not recommended? I don't know what temperature will have the fin-can and I would test it through the test of the motor.

Is anyone who know this glue and will recommend to use it to supersonic rocket?

P.S. The fins will be brazed to the tube (or fin-can or whatever it call in english ) and the fillets are only make for a smooth surface between fin and the fin-can.

 

[Issus]

Pretty much any epoxy will work for fillets, I'm guessing that epoxyweld you have is very similar to JBWeld fillers wise, the colours at least look very similar.

As far as temperature goes, the 121c is likely it's glass transition temp, or heat deflection temperature (basically the same thing). Basically this is the point it starts to get soft, that being said it will still work as a fillet at that temperature but not as well. Can you braze enough material around the base of the fin smoothly enough to make a structural fillet without stress raisers? If so, then the fillet is likely to be purely cosmetic/aerodynamic and its max temp really doesnt matter.

I'd be inclined to recommend you get a high temperature laminating epoxy and add your own fillers to it to increase it's strength and temperature (milled glass, carbon or kevlar - strands of fibers 2-5mm long).

 

[verex]

[video=youtube;r2laTeyC08c]https://www.youtube.com/watch?v=r2laTeyC08c[/video]

 

[Cory]

Great flight!