An "R"-powered rocket build

[Theory]

I am speaking to the inside, and using triangles to more closely match the nose cone shape

 

[Paulb06]

I agree with the glass....2 reasons...(1. glass is easier to layup inside a nose cone and depending on thickness can be tacked in using a few drops of ca....and wetted out inside the nosecone....much easier than trying to handle wet strips...(2. You can use the space inside the nosecone for trackers if its glass....the main case for glass is lighter weight for a given stiffness....you can build it as stiff using glass but it will be thicker and heavier

My bad ...I meant the " main case for CF "

 

[Rail Dawg]

Here's the current stack. Almost 9' of the 22' tall rocket sitting in the Vehicle Assembly Building after installing the bottom 3 coupler assemblies.

Went off without a hitch thank goodness. Had a small scare when the 3rd coupler assembly got a little stuck while inserting it into the top of the stack. But with just a little bit of finesse it behaved and slid like a champ into position.

Used US Composites epoxy for the mating and definitely was a good choice.

Chuck C.

 

[Ez2cDave]

Had a small scare when the 3rd coupler assembly got a little stuck while inserting it into the top of the stack. But with just a little bit of finesse it behaved and slid like a champ into position.

Chuck,

I'm glad you were able to rapidly solve the "Houston, we have a problem" moment with the Coupler Assembly and did not have to "Lock the doors" . . .

Everything looks like it's coming together, nicely . . . Nice shot of the "VAB", too !

Dave F.

 

[Nick@JET]

I spy some huge tubes in the back ground, what is the diameter of those!?

 

[Nytrunner]

I spy some huge tubes in the back ground, what is the diameter of those!?

I think those are from his double-barrel pickup earlier in the thread (when this was a 3' wide monstrosity

 

[3stoogesrocketry]

Chuck , the nose cone you have is for the 11.5 inch V2 . I have two of the same cones . The first one had 8 pounds of lead shot and epoxy in the tip. It fell over while in a 36 inch tube , on a concert floor. Granted it is a heck of a hit , but the cone shattered and the tip , top 6 inches , fractured all the way around the epoxy lead seam. I would wait to get a filament wound cone . Hopefully it will be longer then the 3.2 to 1 he has.

 

[Ez2cDave]

I spy some huge tubes in the back ground, what is the diameter of those!?

Those are the FIREWORKS for the celebration after the successful launch and recovery of the "ARR" . . . !

Dave F.

 

[Paulb06]

Chuck , the nose cone you have is for the 11.5 inch V2 . I have two of the same cones . The first one had 8 pounds of lead shot and epoxy in the tip. It fell over while in a 36 inch tube , on a concert floor. Granted it is a heck of a hit , but the cone shattered and the tip , top 6 inches , fractured all the way around the epoxy lead seam. I would wait to get a filament wound cone . Hopefully it will be longer then the 3.2 to 1 he has.

Ahhh... but would it have fractured with 8lbs of additional fiberglass reinforcement inside instead of lead?

 

[Ez2cDave]

I am speaking to the inside, and using triangles to more closely match the nose cone shape

Theory,

Thanks for confirming that information. I previously inferred that was the technique you were describing.

I agree that this process will solve the issues at hand and allow for successful reinforcement and modification of the Nose Cone.

Dave F.

 

[Ez2cDave]

Ahhh... but would it have fractured with 8lbs of additional fiberglass reinforcement inside instead of lead?

Paul,

We may never know the answer to that question . . .

What we do know is that, as currently manufactured, the Nose Cone will require significant structural reinforcement and modification.

The process of applying multiple layers of triangular "gores" of Carbon Fiber reinforcement to the interior surface, coupled with modifications to allow a machined metal tip to be secured attached ( specifications - TBD ), and filling the nose cone with two-part foam, should effectively overcome the inherent shortcomings of the existing piece of hardware ( Nose Cone ).

I'm sure that Chuck is currently assessing all suggestions and exploring his options.

My personal recommendation to Chuck would be to reinforce and modify the existing unit, rather than waiting for a "filament-wound" item from the same manufacturer that designed and constructed the current Nose Cone, with all its shortcomings.

The reasoning behind that is that filament-winding would be a "totally new" process to Curtis ( manufacturer ) and that, while he is on the "learning curve", quality and structural integrity might be suspect, until he has mastered the process for LARGE Nose Cones.

Dave F.

 

[Theory]

correct Dave, and 'gores' is no doubt the correct term for what I was referring too. also, I am thinking that this is a case where the stiffness of Chuck's carbon will be a benefit as it will be easier to cut, wet out, and lay.

two layers with alternating seams along with a solid metal tip and foam should survive the limited time a Mach 2+

 

[Rail Dawg]

All good advice you guys.

Am currently evaluating the options. Would like a longer nosecone and preferably one good to go out of the box. Working on the current one isn't a problem but it may not be the best choice.

I do appreciate the inputs.

Chuck C.

 

[Rail Dawg]

OK I ran this nosecone past my parts-manufacturing guy. He's able to make a metal tip for this nosecone.

Give some input on how long the metal tip should be. Also the best way to attach it to the nosecone. I'm thinking either the tip is threaded or has all-thread extending from it?

I can layer in a bunch of fiberglass. Foam the void that's left. There will be a Big Red Bee GPS transmitter in the nosecone so glass will be best.

Thanks.

Chuck C.

 

[Theory]

Chuck,

given the scope of this project, I am not sure you will find a nose cone that is 100% ready to go out of the box.

so long as you are comfortable laying the carbon (sounds like you are) and have access to a lathe (or person who can work one) the nose cone modifications are no where near the most complex part of this build

 

[Paulb06]

I

All good advice you guys.

Am currently evaluating the options. Would like a longer nosecone and preferably one good to go out of the box. Working on the current one isn't a problem but it may not be the best choice.

I do appreciate the inputs.

Chuck C.

I Would call Curtis and find out how many plys and what weight cloth were used to tape the 2 halves of your nosecone together...you can look up the cloth an determine the finished layup thickness and it will tell you how strong the cone is.......if the thickness of the seam is equal to the rest of the cone, it's as strong as a one piece cone....I've seen FW turned into a pile of small pieces and whether its stronger depends on how the fibers are oriented

 

[Theory]

yes, for RF, glass will be needed over carbon.

the length should be determined by the contour of the structure. I would start it a few inches (4-5) below the "step" shown in the picture you sent. I would drill and tap the metal slug and then insert a piece of all-thread secured with some JB. That could then be anchored into a fabricated frame within the nose cone itself.

 

[Steve Shannon]

OK I ran this nosecone past my parts-manufacturing guy. He's able to make a metal tip for this nosecone.

Give some input on how long the metal tip should be. Also the best way to attach it to the nosecone. I'm thinking either the tip is threaded or has all-thread extending from it?

I can layer in a bunch of fiberglass. Foam the void that's left. There will be a Big Red Bee GPS transmitter in the nosecone so glass will be best.

Thanks.

Chuck C.

You mentioned stainless steel earlier. Before going down that road I would suggest getting approval from the launch director wherever you plan to fly it. Steel is not necessary. Phenolic or aluminum would be acceptable. A radiused tip rather than a sharp tip would lessen heat concentration.

 

[Ez2cDave]

OK I ran this nosecone past my parts-manufacturing guy. He's able to make a metal tip for this nosecone.

Give some input on how long the metal tip should be. Also the best way to attach it to the nosecone. I'm thinking either the tip is threaded or has all-thread extending from it?

I can layer in a bunch of fiberglass. Foam the void that's left. There will be a Big Red Bee GPS transmitter in the nosecone so glass will be best.

Thanks.

Chuck C.

Chuck,

If Andrew ASC can run the supersonic aerodynamic sims, get the Nose Cone dimensions over to him, ASAP.

By seeing the thermal data, he should be able to give you an accurate "number" for the required length of the metal tip.

TIP MOUNTING : I recommend a "solid block" inside the Nose Cone ( possibly JB Weld, with a "cast in place" All-Thread rod that the Nose Cone Tip will thread onto - must be "DEAD-CENTER", in all respects ).

YES . . . If the GPS is mounted in the Nose Cone, Fiberglass is mandatory over Carbon Fiber, due to RF shielding properties of CF !

Dave F.

 

[Ez2cDave]

correct Dave, and 'gores' is no doubt the correct term for what I was referring too. also, I am thinking that this is a case where the stiffness of Chuck's carbon will be a benefit as it will be easier to cut, wet out, and lay.

two layers with alternating seams along with a solid metal tip and foam should survive the limited time a Mach 2+

Theory,

I used the word "gores" ( triangular sections of cloth sewn together to make parachutes ) figuratively, without being 100% sure that the same term would be applicable in this situation.

Looks like Chuck will be going with Fiberglass, as he needs the "RF-transparency for his GPS system.

Dave F.

 

[Rail Dawg]

Good stuff gentlemen. This will be a good learning experience on how to beef up a nose cone.

Having the tip manufacturered is a good first step. Going to go with aluminum unless Andrew ASC says otherwise. Will use the threaded rod method making sure it’s perfectly straight.

Lots of fiberglass. Should do the trick.

Chuck C.

 

[Rail Dawg]

Altimeters question since we're getting to that part of the build.

Back in the 2000's many altimeters would blow the charge right after arming on the pad. It of course was a frustrating experience. Hard to tell what caused the problem but most of us thought it was wind blowing across the static ports. Only on altimeters that armed immediately and not after x amount of feet or time after liftoff.

I'll be running 2 of the Marsa 33LHD altimeters with a PerfectFlite StratologgerCF as a back-up.

Any of you still see premature charges blowing on the pad these days?

Thanks.

Chuck C.

 

[tim cubbedge]

Haven’t seen it in a while & last time I did, it was user error. The guy hooked an ejection charge directly to battery. If that’s a concern, you might try a WiFi switch from Eggtimer where you can arm altimeter from a safe distance.

 

[Andrew_ASC]

Chuck,

If Andrew ASC can run the supersonic aerodynamic sims, get the Nose Cone dimensions over to him, ASAP.

By seeing the thermal data, he should be able to give you an accurate "number" for the required length of the metal tip.

TIP MOUNTING : I recommend a "solid block" inside the Nose Cone ( possibly JB Weld, with a "cast in place" All-Thread rod that the Nose Cone Tip will thread onto - must be "DEAD-CENTER", in all respects ).

YES . . . If the GPS is mounted in the Nose Cone, Fiberglass is mandatory over Carbon Fiber, due to RF shielding properties of CF !

Dave F.


View attachment 379116

I can only predict how hot that nosecone ultimately gets. The curves on a nosecone require finite analysis thermally with a Solidworks package I no longer have access to post graduation. The length of aluminum tip it is unknown because it’s not hand solvable that I know of but I would reckon a few inches of solid aluminum would be fine. Aluminum makes a great heat sink, forget the steel you won’t need it. Steel anything non recovery hardware related will make launch approval harder. Sorry to be the downer. Wish I could help more.

 

[Ez2cDave]

Well if Aerotech can't keep up with 38mm+ sizes, you can always go with no-hazmat Loki lol. The beauty of a free market and you support a smaller fish

I can only predict how hot that nosecone ultimately gets. The curves on a nosecone require finite analysis thermally with a Solidworks package I no longer have access to post graduation. The length of aluminum tip it is unknown because it’s not hand solvable that I know of but I would reckon a few inches of solid aluminum would be fine. Aluminum makes a great heat sink, forget the steel you won’t need it. Steel anything non recovery hardware related will make launch approval harder. Sorry to be the downer. Wish I could help more.

Andrew,

You are correct about it not being "hand-solvable", at least not in my repertoire of mathematical skills.

Agreed 100% on Aluminum over Steel for the tip material . . . As for length, my "calibrated eyeball" says a Base Diameter of 2"-3" with contours matching the Nose Cone, all the way to the tip, with a radiused tip vs. a sharp tip.

POINT TO REMEMBER : Never apologize for supplying facts and giving honest answers . . . You are an extremely valuable member of the "Steely-Eyed Missile Men" of the Support Team and it is a pleasure to work with you, sir !

Dave F.

 

[Paulb06]

Oops

 

[boatgeek]

Altimeters question since we're getting to that part of the build.

Back in the 2000's many altimeters would blow the charge right after arming on the pad. It of course was a frustrating experience. Hard to tell what caused the problem but most of us thought it was wind blowing across the static ports. Only on altimeters that armed immediately and not after x amount of feet or time after liftoff.

I'll be running 2 of the Marsa 33LHD altimeters with a PerfectFlite StratologgerCF as a back-up.

Any of you still see premature charges blowing on the pad these days?

Thanks.

Chuck C.

I don't have experience with the Marsa products, but I've never seen an issue like that with the Stratologger.

 

[Nytrunner]

Discussion on heating in your flight regime found here https://www.rocketryforum.com/threads/heat-at-mach-2-25.17581/

 

[Rail Dawg]

Discussion on heating in your flight regime found here https://www.rocketryforum.com/threads/heat-at-mach-2-25.17581/

Great thread!

Thanks for posting that.

Chuck C.

 

[Ez2cDave]

Great thread!

Thanks for posting that.

Chuck C.

Chuck,

Several items in that thread have "warning bells" going off in my head.

I'll quote the posts :https://www.rocketryforum.com/threads/heat-at-mach-2-25.17581/

QUOTES :

Rob,

While I don't have a Kestrel, an all carbon 75mm bird that I flew to Mach 2.2 melted the clearcoat on much of the nosecone and portions of the fins. The clearcoat is supposedly rated to 500 degrees F.

-Eric-

When I flew my 2" rocket on L730's, the nose cone would regularly look like the picture below. The speed with this motor would be right at Mach 2. I tried some higher temperature paints from the big box stores, but didn't find anything that worked. Now, I paint my high speed nosecones with the Cotronics/Duralco 4525 epoxy, and that seems to work pretty well. I have noted that the "regular" fiberglass nose cones from Performance Rocketry can bubble a little under this epoxy, but it is certainly better than paint. The "graphite" cones plus contronics survive unscathed, at least up to Mach 2.6 for short durations.

Painting with this epoxy is a little like trying to paint with cottage cheese - it's not really designed for the job. However, it can be done, and with a little technique and a lot of sanding, the results can be pretty good.

I also paint the leading edges of the fins with cotronics. I have never seen the epoxy itself fail, but it wouldn't surprise me if the underlying epoxy would degrade over multiple flights.

Jim

View attachment 36613

You're asking the wrong question.

The math is not that difficult, but the real question is what is the heat load and how will the NC and the leading edges handle it. (The airframe doesn't get hot.)

The heat load is proportional to the product of the air density times the Mach Number cubed. You need to perform a trajectory calculation to develop a time, velocity, and density table to determine the cumulative heat load versus time, and then look at the mass per unit area, the specific heat capacity, and thermal conductivty of the NC and leading edge material to determine the temperature history of the surfaces.

Bob

If you just want to know what the stagnation temperature would be at the tip, you can use this calculator: https://www.grc.nasa.gov/WWW/K-12/airplane/atmosi.html.

For example: 5000 ft and 1871 miles/hr is exactly Mach 2.5. Then select 'Total Temperature' from the drop-down selection, and it will show 667F.

Jeroen

Hello,
I did some research and found a dow corning 2 part rtv that is an ablative.
Dow corning 3-6077 RTV Silicone Ablative with penetration rate 0.035 mm/sec
at 45W/cm2 (approx 40 BTU/ft2-s).

https://www.specialtyadhesives.com/dow_sealants/3_6077_RTV.pdf

Greg

 I did some research and found a dow corning 2 part rtv that is an ablative.
Dow corning 3-6077 RTV Silicone Ablative with penetration rate 0.035 mm/sec
at 45W/cm2 (approx 40 BTU/ft2-s).

This is one way of looking at solid heat transfer problem. Although, one should be careful about talking about ablation versus the temperature profile diffusing into the solid by conduction. The rates might be different. Some materials may ablate or erode directly from the solid phase to the gas phase. Other materials like silica phenolic or carbon phenolic will form a char layer (where the volatiles, etc. have cooked out) that blows or erodes away. This is the case in phenolic nozzles for large solid rocket motors. So, the ablating part is different than the heat conduction. The rates are different. Behind the char layer, heat diffuses into the virgin phenolic by ordinary conduction. Actually, carbon phenolic has not only been used in solid rocket motors, but also on re-entry heat shields.

One also can talk about the rate of heat diffusivity into the solid by conduction. One approximate way to do this is to use the method of Goodman, where one assumes a parabolic temperature profile diffusing into the solid. One could probably come up with an estimate of how fast the temperature profile advances into the solid. If the thermal conductivity of the solid is high and the thickness of the solid object is small, one can check the Biot number and say that the temperature profile is essentially flat and that the temperature of the whole solid changes with time uniformly. If this were the case for thin fins, one could estimate that all the thermal energy in the gas thermal B.L. could be in equilibrium with the thermal energy in the solid. For our kind of problems, the rise in the carbon fin temperature might not be too bad, because the thermal capacitance (density times thermal capacitance) of the solid might be on the three orders of magnitude higher than the gas. (Solids are much denser than gas.)

Bob

There are no "volatiles" in professional phenolic epoxies to boil off. Phenolic epoxies have a graphitic type backbone, and when it gets extremely hot, well above 350C, the resin pyrolizes which means it looses OH and H radicals as it converts to char (graphite). Pyrolysis of phenolic epoxy will not occur in s short M=2.25 rocket flight as the temperature of the resin won't get that high. Paints however will blister under under this level of heating.

Bob

Hello,
And excuse me science guy for no wanting to blow everybody away with talk
of chemical radicals and using such a low tech and general term as volatiles.

And yes it the nose cone does reach 350deg c temperature at mach 2.3 to mach 2.5 ,depending on altitude, but since this is the peak speed of the
flight there is not enough time for the heat flux to do major damage to the vehicle.

For lighter or higher impulse vehicle this will become a problem,This will also
be a problem for carbon fibers that do not use phenolic epoxies.

We actually used graphite foil overlaid on the carbon fiber to conduct the
heat away from the highest heat area of the nose cone ,which has a
high temperature resistance and strength in a very thin foil.

For vehicles that are going for the 100km altitude or sub orbital flight,These
vehicles are going to see temperatures in excess of 1000deg f depending
on altitude.

Greg

END QUOTES:


We need to look at this situation very closely . . . AndrewASC, please take a look at this data !

Dave F.