Plastic Nose Cone over Mach

[roytyson]

So there have been several build threads with the Mach1 kits and going over mach wit them. Question (or worry) for me is the stock Estes style nose cone. WIll it survive 2 seconds over mach? Will the heavier Loc nosecone be better and survive?
Just not sure what direction to go. A wildman fiberglass nose cone will work with a fiberglass sleeve but will have to build up the bottom of the cone to match the body tube.

Thanks

 

[Eric]

I would love to see or hear about a nose cone failure from aerodynamic heating or forces. I'm planning on pushing my Mach 1(Estes) nose to the limits and see if it fails.

 

[tfish]

here's some screen grabs from a 54mm min dia with a J800. The rocket used a LOC plastic nose cone. The 38mm LOC nose cones are even thicker.




Tony

 

[Andrew_ASC]

I would love to see or hear about a nose cone failure from aerodynamic heating or forces. I'm planning on pushing my Mach 1(Estes) nose to the limits and see if it fails.

Get me the nosecone length, radius, and expected sim Mach number. I’ll return with aeroheating calculations and throw compressible gas dynamics theory at your Estes cone, lol.

If anybody knows the plastic material Estes uses, compare the melt temp to aeroheating temp.

 

[Andrew_ASC]

I’ve heard explaining from Steve Shannon that the nose and etc doesn’t get hot long enough to do damage in most hpr flight.

 

[MClark]

The 38 and 54 LOC nose cones are pretty much indestructible.
Estes I would say it depends on the cone, size and construction. The molded one piec with the longitudinal mold line are not as strong as the two peice where the cone and shank are glued together.

 

[crossfire]

PML makes a very nice plastic cone. Dose anyone know how they fit Mach 1 tubes. I myself was wondering about the 3" size.

 

[Andrew_ASC]

Give me nosecone length, radius, and a Mach number. I’ll dork your aeroheating problem. Consider your total temperature across an oblique shockwave solved.

 

[roytyson]

Here is the data I have so far. The nose cone info Im not at home (traveling with family for Christmas), but my guess is a standard NC60 Estes nose cone, but couldn't find any data.

 

[Eric]

Give me nosecone length, radius, and a Mach number. I’ll dork your aeroheating problem. Consider your total temperature across an oblique shockwave solved.

1.64 diameter, 8.35" long, Mach 2.1.

 

[Andrew_ASC]

Compressible gas dynamics theory says with oblique shock effects across the nosecone that it will have a maximum temperature of 459.94 degrees Fahrenheit, Eric.

 

[Eric]

How long at that speed would it take to reach that temperature?

 

[GalantVR41062]

When heating parts for machining (engine blocks and heads etc) in ovens it's 1 hour per inch. So you could figure based on thickness of the cone and the seconds at speed.

~John

 

[grouch]

Cut the back off the nose cone and fill it with expandable foam.

 

[Andrew_ASC]

How long at that speed would it take to reach that temperature?

Sad moment in engineering. I can’t hand solve that question. The finite element solutions by hand were for very thin flat plate fins found in heat exchangers or simple blocks. In undergrad mech engineering we were told once a curved geometry involves thermal loadings to answer heat transfer questions involves a software based engineering computer analysis. The only other internal heat problems we had were pipe systems with water flowing and like insulation on the outside for hand solve. At this point for your problem it becomes a differential equation solution set and is no longer trivial when it takes a computer program and a 3D model to solve. Sh*t made a computer grind away for an hour plus for a silly block with a hole in it.

Even engineers have limits. You’ve hit my limit here. Fair valid question though you have.

In a practical sense I would guess a time span longer than burn time for the nosecone to begin heating up to that temperature. Not certain but it’s not instant like flipping a light switch. Most of these hobby rockets do not have thermal problems because of how small the timespan is at high Mach.

 

[MClark]

TFish, Tony's post he used a plastic cone to approximately M2 successfully.
If you are going faster it's time to step up to better materials.

M

 

[Andrew_ASC]

I guess the experimental method would be stuff the nosecone into an oven at 450 F then take an IR grade food laser and measure it’s temperature on surface of plastic and time it to see how long it takes to heat up or damage. That’s the best idea non computerized engineering software I can come up with. Use a spare Estes nosecone.

 

[Steve Shannon]

Look, people use torches to treat the surface of plastic nosecones to help spray paint adhere. Tony showed data reflecting an external temperature of 102°F, not even as warm as a hot tub. There’s just not enough dwell time for excessive heating. Fugedaboutit!

 

[Andrew_ASC]

Thanks Steve.

 

[ksaves2]

Me thinks a few seconds above Mach 1 isn't going to hurt a thing. If one is pushing above Mach for 25 seconds then whatever paint if used will
be ablated off parts of the nosecone, body and leading edge of the fins. If using thin plastic for an extreme as described, me suspects heating might be a really big problem but that would be a stupidhead move to use a plastic nosecone for serious ventures above Mach.

Pete Knight's speed record speed run in the X-15 nearly ended in disaster if the motor had burned a bit longer:
https://www.youtube.co/watch?v=wHuBsBOF4R8

And that ship had an ablative coating sprayed on it too over the iconel-X alloy.

The aluminum nosecone tips are superfluous for 99.7% of the fliers out there including myself but oh do they look cool. Kurt

 

[Andrew_ASC]

Mi-15 and MA-25s ablatives on X-15 by Lockheed Martin. You can buy repair kits of it. Expensive.

 

[ksaves2]

Mi-15 and MA-25s ablatives on X-15 by Lockheed Martin. You can buy repair kits of it. Expensive.

Why bother? That's what metal fins and nosecone tips are for. Kurt (Merry Christmas, just got back from midnite mass.)

 

[Rocketjunkie]

I've had LOC 54mm nose cones to mach 2 (L750 in G10 tube, 2 lb. less motor) with only melting of the primer under the engine paint. No damage at all to the plastic after dissolving the paint off. (LDRS X in 1991) The shorter ones were mine, Ken Pritchett owned the other 2. The photo was taken at Bruno's

 

[David Schwantz]

I just got the LOC NC with sleeve from Mach1 last night. They are much thicker than the stock supplied one. They do not fit Mach1 tubes though. The sleeve it too large DIA it got stuck in tube and had to be removed with force. Will take lots of sanding to make it fit.I also ordered a fiberglass one from Apogee, it will also fit with the sleeve, sleeve still way tight though. Would you prefer glass or plastic? I ordered a tracker from Eggtimer, how are you guys attaching the shock cord to sled in the NC?

 

[cbrarick]

I've done LOC, PML and the old Wildman plastic nose cones to well over mach 1, never a problem. Only managed to burn the paint once - on my wildman dual deploy thanks to a L935. You'll recognize the lift off as my avatar.......

 

[roytyson]

I just got the LOC NC with sleeve from Mach1 last night. They are much thicker than the stock supplied one. They do not fit Mach1 tubes though. The sleeve it too large DIA it got stuck in tube and had to be removed with force. Will take lots of sanding to make it fit.I also ordered a fiberglass one from Apogee, it will also fit with the sleeve, sleeve still way tight though. Would you prefer glass or plastic? I ordered a tracker from Eggtimer, how are you guys attaching the shock cord to sled in the NC?

And that is part of my dilemma. I have to figure out how to get a tracker (Eggfinder) into the nose cone. I love Labrats' nose cone adapter and was hoping to find a nosecone that would work with that, but I can build something if need be. I also take issue paying $15 in shipping for a $15 dollar nose cone from Mach1. I asked Steve about this but never received a response. What is clear from this thread, is there is no clear answer to the dilemma we all are seeking: an all fiberglass nose cone for Mach1 BT60 tubing. Its too bad that the manufacturer of the tubing for Mach1 can't come up with a glass nose to match the tubing. Or maybe they can, and its just not cost prohibitive.

 

[David Schwantz]

And that is part of my dilemma. I have to figure out how to get a tracker (Eggfinder) into the nose cone. I love Labrats' nose cone adapter and was hoping to find a nosecone that would work with that, but I can build something if need be. I also take issue paying $15 in shipping for a $15 dollar nose cone from Mach1. I asked Steve about this but never received a response. What is clear from this thread, is there is no clear answer to the dilemma we all are seeking: an all fiberglass nose cone for Mach1 BT60 tubing. Its too bad that the manufacturer of the tubing for Mach1 can't come up with a glass nose to match the tubing. Or maybe they can, and its just not cost prohibitive.

Roy, I have a 38 mm NC sled coming from SMT, won't ship till after Jan 1 Steve said. Also have a Lab rats coming, will use what works best. Egg finder Mini tracker also on its way. Will let you know what all looks like when it gets here. I have not cut the back end off the LOC NC yet. Waiting to see if the glass one from Apogee will work with everything stuffed inside. OOps, forgot but I also have a Wildman 38mm NC on its way. I think any would work, but only the best for this Mach1 bird

 

[Not Quite Nominal]

Sad moment in engineering. I can’t hand solve that question. The finite element solutions by hand were for very thin flat plate fins found in heat exchangers or simple blocks. In undergrad mech engineering we were told once a curved geometry involves thermal loadings to answer heat transfer questions involves a software based engineering computer analysis.

Even engineers have limits. You’ve hit my limit here. Fair valid question though you have.

I’m not an engineer, but I did drop out of one of the finest engineering schools. Also I occasionally stay at a holiday inn express.

Being raised in the generation before overwhelming computing power was ubiquitous, I have a simple philosophy: when confronted with a (numerically) hard problem, I try to find an easy problem that bounds it.

In this case: I know the stagnation temperature at this airspeed, I know the time it spends at this airspeed, and have some idea of the thermal inertia of the material.

I expect five seconds or so of 450 degrees on one pound of thermoplastic to be essentially zero. Pop that sacrificial nose cone in the oven for five or ten seconds to verify.

 

[OverTheTop]

We have the luxury of only having to be supersonic for a very short period of time in this hobby. Up to M1.4 I would probably have no concern. Above that I would be asking what experience others have had. So far it looks like M2.0 is a safe number.

As for stuffing stuff into the NC, I would probably tape the required elements to some form of sled (corrugated cardboard maybe, if you are in a hurry) and then bubble-wrap. Consider the peak acceleration with your motor of choice when figuring out how robust the sled and attachment needs to be.

 

[Eric]

Stock Mach 1 (Estes) nose cone adapted for labrat sled. Just a piece od 38mm coupler inside the nose.