Altitude record attempt using the O3400 in minimum diameter style.

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You know I was thinking. You know how for the auto industry they chrome plate auto parts like bumpers and such. I dont know anything about chromeing things. My thought was could you actually chrome a composite fin can just like plastic parts are chromed? My thought behind that is the chrome plating can act as a barrier from the heat so consequently protect the composite underneath. IDK What do you think or is it just pie in the sky??
 
You know I was thinking. You know how for the auto industry they chrome plate auto parts like bumpers and such. I dont know anything about chromeing things. My thought was could you actually chrome a composite fin can just like plastic parts are chromed? My thought behind that is the chrome plating can act as a barrier from the heat so consequently protect the composite underneath. IDK What do you think or is it just pie in the sky??
You can vapor deposit chrome to anything, or you can probably use an electrodeless nickel chrome plating process, but it will not do what you want it to.

There are no thin metal plating processes that will protect a composite from heat. If the resin in a composite will flow with heat, the chrome plating will float over it. If the composite resin pyrolizes with heat, the trapped gas pressure will explosively remove the chrome plating. The same applies for chrome plating over plastics, and for high temperature barbeque or header paint over composites or plastics.

These coating are used to protect and prevent underlying metals from oxidizing and burning. High temperature composites with phenolic resin binders pyrolize and the generated gases carry away heat to minimize the heat penetration into the bulk. Often silica microballoons are incorporated into the resin to reduce density and thermal conductivity and when melted protect the surface from oxidation which reduces non-pyrolysis mass loss.

Bob
 
the chrome will transfer heat. your best bet for insulation would be a ceramic paint. I have never built or flown a rocket at this performance level but these have been proven to reduce heat transfer on and in high performance engines. there are some that do not require high temperature curing which would work on fins and the nose. I have applied them to a turbo header with great results, next time the engine is apart is is going on the piston tops and in the combustion chambers.
 
You know I was thinking. You know how for the auto industry they chrome plate auto parts like bumpers and such. I dont know anything about chromeing things. My thought was could you actually chrome a composite fin can just like plastic parts are chromed? My thought behind that is the chrome plating can act as a barrier from the heat so consequently protect the composite underneath. IDK What do you think or is it just pie in the sky??

You should really be focusing on a coating with a low thermal conductivity, not service temperature alone.

Look into this, I'll be using it on an upcoming project.
https://www.apogeerockets.com/education/downloads/Newsletter365.pdf

I actually doubt you'll need much protection. I don't think you'll break 3.

Alex
 
Chrome plating is a multi-step process.
They start with an acid bath... followed by dipping the item in: Copper then, Nickel, finally Chrome.


Has anyone attempted powder coating a rocket?

JD
 
Yea I am thinking mach 2.5
At Mach 2.5 the maximum stagnation gas temperature is ~350 C (660F) @ ~ 1 mile AGL under standard conditions (seal level @ 15 C (59 F). The surface temperature will be less. You can simulate the effect with a 1000 F heat gun for ~ 10 s -20 s.

You do not need to do any extraordinary surface treatments for this Mach level of transient heating. The most I would do is to cover the NC with a single layer of phenolic laminating epoxy.

Bob
 
Well the guy seems worried about composite material unable to stand up to heat when the rocket goes past mach 2, so I thought aluminum would be more heat resistant.
 
Aluminum is dead soft by 300 C. Not a good choice for sustained Mach 2+ flights. That's why Mach 3 aircraft use either stainless steel (MIG-25) or Titanium (SR-71) skins, however CF composites with phenolic resin is fine for rockets at Mach 2.5.

Bob
 
Stainless steel sounds heavy. Maybe a really thin wall nosecone (since that's the only part that's going to get heat) could work? Titanium sounds too exotic right now.
 
Stainless steel sounds heavy. Maybe a really thin wall nosecone (since that's the only part that's going to get heat) could work? Titanium sounds too exotic right now.

Sounding rockets regularly fly fiberglass nosecones past mach 4 if you put some ablatives on the cone.

Thin walls for compressive strength is a bad combination. That is one of the reasons why aluminum is used so much is because you can get much thicker walls for the same amount of weight, which is better for compressive loading.
If it were me I'd just use fiberglass or carbon, then have a steel or titanium nosecone tip to take the brunt of the heating. Then I would use ablatives if I was expecting much over mach 3. The phenolic epoxy suggested by bob sounds like a pretty solid idea if you are really worried about heating at these speeds.

I've flown my standard fiberglass with aluminum tip wildman nosecone to mach 1.5. I'd be comfortable flying it to mach 2.5 if I replaced the nose tip with one that seats better into the nosecone. The existing nose tip will slide out of alignment if it is loaded too much or loose at all. I wouldn't really be worried about the heating.
 
Automotive brake caliper paint can handle close to 2,000 degrees, but you need to find primer just as effective. Color choice is limited (Red, gray, and black), but you can buy ratllecans of this at your nearest auto parts store.
 
Points taken, however the caliper paint has to stand up to the presence of brake lining dust, which is metalic and highly abrasive. Kind of like being constantly exposed to steel wool. As far as getting the paint to stick, part of that is dependent upon the painter. It is better than most of the other retail store alternatives.
 
Mach heating is the product of a Mach Heating Constant which is then modified by a Mach Heating Correction Factor, MHCF = M^3, and the Altitude Density Correction Factor, ADCF = e(-0.138 x km), which accounts for the 12.9% density reduction in the atmosphere per kilometer of altitude above sea level.

The Mach Heating Constant is ~4.49 Watts/cm^2 at M=1 and sea level. The rocket under discussion in this thread is expected to reach a V, max of M = 2.5. With an O3400 max V would occur at ~1.8 km. The MHCF = 2.5^3 = 15.625 and the ADC = e(-0.138 x 1.8) = 0.78 so the peak heating rate is 4.549 x 15.625 x 0.78 = 55.4 watts/cm^2. The numerical integration of the product of the product of the MHCF x ADC is proportional to the total stagnation heat flux into the nose tip. The heating falls off rapidly away from the tip. A 0.25" thick NC would have a surface area density of 1 gm/cm3. It would have a specific heat of about 1 J/g/C. A heating rate of 55 Watts/cm^2 would raise the bulk temperature at a 55 C per second rate. It would take ~4 seconds at the max heating rate to raise the bulk temperature to 200 C which is the maximum service temperature of a phenolic resin composite, however the heat can also be transferred away from the tip, or the tip can be made more massive from aluminum to hold the heat, or from phenolic which can ablate if it gets too hot. The heat input falls off rapidly to the edge of the NC where the heating rate and heat fluence is about 10% of the stagnation values so it is only the tip that experiences somewhat high heat. In-flight a rocket is rapidly decelerating after V max and the density is dropping rapidly as the altitude increases so the heating rate rapidly decreases with time. Cooling is also not considered and the airflow will carry some heat away as will radiation. The flight profile should will not threaten the structural integrity of a well built FG or CF composite NC provided it is laminated with a 200 C rated resin.

Bob
 
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This is a plot of the Instantaneous Aeroheating of the Nose Tip of a Similar Flight to 61 KFT. Peak heating is ~54 W/cm2 @ M =2.6 and 7700' ASL.

4inchaeroheatingO3400.png

The Integrated Heat Flux is ~340 Joules/cm2. That's not going to do anything significant to a well designed CF or FG nosecone with a thick tip made with a properly heat treated phenolic epoxy. Since the aero heating falls off rapidly from the stagnation point, an aluminum, graphite or phenolic nose tip can be used if a thicker nosecone tip is not desired.

Bob
 
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Its time to resurrect this build thread. After putting this rocket on the back burner I have decided to put it out of mothballs and try to finish it.
 
Its time to resurrect this build thread. After putting this rocket on the back burner I have decided to put it out of mothballs and try to finish it.

Hey Andrew , I just looked over this thread again . As far as heat protection / ablatives go , just do like the big boys do . They take high temp red rtv , thinned down with acetone. Paint it on , let cure and fly .
Eric
 
Hey Andrew , I just looked over this thread again . As far as heat protection / ablatives go , just do like the big boys do . They take high temp red rtv , thinned down with acetone. Paint it on , let cure and fly .
Eric

Could you elaborate on this technique?
 
It is as simple as it sounds . You thin the RTV down just enough to apply with a HVLP sprayer. The idea is that the RTV WILL burn off and carry the heat with it during the critical time the rocket is accelerating thru M3+ at lower altitudes . The solution to the higher CD rate of the rocket while the rtv was burning off was solved by using more thrust.

Eric
 
It is as simple as it sounds . You thin the RTV down just enough to apply with a HVLP sprayer. The idea is that the RTV WILL burn off and carry the heat with it during the critical time the rocket is accelerating thru M3+ at lower altitudes . The solution to the higher CD rate of the rocket while the rtv was burning off was solved by using more thrust.

Eric

Curious, what are the characteristics when it ablates? Does is melt? Strip/erode off? Other?
 
What do u guys think will be better. A filament wound ogive cone from rocketry warehouse or a new fiberglass poly infused pheonlic tip cone from Wildman?
 
I agree with you on that part. But would I gain a better advantage on going with that cone from Wildman over a filament wound from rocketry warehouse?

First, I agree with Justin about going with the manufacturer of your tubing.

That said, considering this rocket is going to be hauling arse I would go for a cone with a large l/d. 5:1 or more. VK or conical
 
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