Speed of plastic nosecones

[pugachu]

Last year I bought a mostly complete Aerotech Initiator startup pack for less than the price of the included 29/40-120 casing...

I really didn't need another project in the build pile, and I already have a stock Initiator, so I plan on 'glassing this and putting a 54mm mmt in it..

Any idea if the stock nosecone will hold up to the mach 2 it sims at with a K1103 (the max that will fit, while still leaving room for HED)

I'd rather not make a mold and make a 'glass nosecone, unless it really needs it.

What's the hardest that ya'll have pushed non-reinforced plastic nosecones? I don't want to fill it with 2-part foam, as I need the room for recovery.

 

[Art Upton]

about ~15 years ago, I had a 2.65" carbon fiber payload tube slice a plastic nose cone at the shoulder as it approached some high speed barrier above regular mach. It was a Red Line Kosden by Aerotech full K as it was a baby L 54mm casing. The 2.65 booster tube was kraft tubing using a 54mm ACME fin can that fits inside the BT-80HD. [I found the 54mm ACME can fits BT-80HD inside like a glove and the 38mm fin can fits inside 54mm LOC tube like a glove]

That caused the rocket payload parts to break up while the fin can and booster/motor continued to fly up, and then come back down in a bad way.

This makes me think the Nosecone was fine at Mach 1, it was when it got near the next bump in the air that caused a problem.

I always thought if I had not used the "available" 2.65 carbon payload tube I had laying around it might have been a better flight as that carbon was sharp compared to fiberglass.

Ironic I found the broken parts in the shed last week going thru stuff I need to sell.

 

[kjhambrick]

@pugachu --

I've only flown a plastic nose cone to about Mach 1.2 or so EDIT: Mach 1.14 or so ( redid my arithmetic ) ...

Note that I always fly with a single 1/16 inch polystyrene rod shear pin into the nose to keep it attached at burnout and during the drogue phase.

I wouldn't worry about the plastic nose cone at Mach 2-ish.

But what about the molded plastic Aerotech fins ?

-- kjh

Flights with an AltAcc for two rockets with a plastic nose cone from way back when:

Key: ot - Ocitillo Test Range, sf - ROC Spring Fest, ts - Tripoli Vegas Turkey Shoot, fi - Fiesta Island

Spock's Johnson ( LOC Vulcanite ):


And Vulcanette ( rebuilt and rechristened "T'Pring's P'Toy" ) -- a Vulcanite Scale Model built with glassed AT 1.9 inch tubes and nose.



Site Temperatures were between 60 and 80 F for all flights ( SoS in the range 340 m/sec to 347 m/sec ).

EDIT: arithmetic and punctuation

 

[lr64]

A great deal would depend on what KIND of plastic was used. Don't take this as gospel, but poking around the internet results in the following figures for glass transition temperature, which is usually a guide to when the stuff isn't much good anymore, structurally. UHMW is an exception, with a glass transition temperature far below 0, but a service temperature of 100C.

PET 67-81C
PVC 82 (it's easy to persuate a PVC pipe to act like a wet noodle. Oddroc devotees, take note.)
polystyrene 100
ABS 105
acrylic (i.e. Plexiglas, etc.) 100-115
polycarbonate 147
PEEK 143 but some flavors have a "useful operating temperature" up to 250C

Of course, there are lots of other plastics

 

[kjhambrick]

<<snip>>PVC 82 (it's easy to persuate a PVC pipe to act like a wet noodle. Oddroc devotees, take note.)<<snip>>

Dang !

I had to look up pursuate !

-- kjh

 

[J Blatz]

AeroTech 2.6 NC is lightweight and not made for this kind of use

 

[lr64]

Dang !

I had to look up pursuate !

-- kjh

Can't get away with a simple typo around here!

 

[pugachu]

I wouldn't worry about the plastic nose cone at Mach 2-ish.

But what about the molded plastic Aerotech fins ?

-- kjh

I was not going to use the stock fins, and was going to make matching fins from 1/8" thick G10 fiberglass. they are fairly large, and swept back, so there may be a stiffness issue. I need to 'feel' them when attached, to get an idea if I need to reinforce with tip to tip CF.

 

[lr64]

The middle third or half of the material in solid G10 fins is there merely to increase mass and lower flutter speed, thus placating the powerful carbon fiber lobby. Similar concerns lead to the use of woven fabric instead of criss-crossed layers of uni.

 

[lr64]

The middle third or half of the material in solid G10 fins is there merely to increase mass and lower flutter speed, thus placating the powerful carbon fiber lobby. Similar concerns lead to the use of woven fabric instead of criss-crossed layers of uni.

The middle third gives less than 4 percent of the bending stiffness, but 33 percent of the weight.

 

[mperegrinefalcon]

If you want to do extreme flights like that you need to go with composites. Plastic nosecones and fins are not rigid enough imo.

 

[Art Upton]

@pugachu --

I've only flown a plastic nose cone to about Mach 1.2 or so EDIT: Mach 1.14 or so ( redid my arithmetic ) ...

Note that I always fly with a single 1/16 inch polystyrene rod shear pin into the nose to keep it attached at burnout and during the drogue phase.

I wouldn't worry about the plastic nose cone at Mach 2-ish.

But what about the molded plastic Aerotech fins ?

-- kjh

Flights with an AltAcc for two rockets with a plastic nose cone from way back when:

Key: ot - Ocitillo Test Range, sf - ROC Spring Fest, ts - Tripoli Vegas Turkey Shoot, fi - Fiesta Island

Spock's Johnson ( LOC Vulcanite ):
View attachment 643201

And Vulcanette ( rebuilt and rechristened "T'Pring's P'Toy" ) -- a Vulcanite Scale Model built with glassed AT 1.9 inch tubes and nose.

View attachment 643202

Site Temperatures were between 60 and 80 F for all flights ( SoS in the range 340 m/sec to 347 m/sec ).

EDIT: arithmetic and punctuation

Are not LOC 38 and 54mm nose cones much more thick compared to 2.56" Nose cones by AT?

The LOC Nose Cone in the 38mm Rocket Fence Posted into the Black Rock Playa did not have an issue flying on a J570 motor in that picture I posted in another thread.

 

[pugachu]

After hearing the suggestions, I will proceed with making a mold and FG cone for this.

Thanks for indulging me

 

[lr64]

It might be easier to just reinforce a pre-made nose cone with some internal rings and stringers, leaving most of the space empty.

 

[bad_idea]

Since you're glassing the tube - increasing its OD - what about cutting some overlapping fiberglass gores and epoxying them to the outside of your cone, both to reinforce it and to bring the OD up to match that of the tube? If that's not strong or stiff enough, you could also glass the inside of the cone, though that could be trickier.

Note: I've not actually tried this myself so can't say how it will hold up. It's just an idea that's been in the back of my mind for a rocket of similar construction and performance that I've been designing.

 

[Initiator001]

If you want to do extreme flights like that you need to go with composites. Plastic nosecones and fins are not rigid enough imo.

In 1989 AeroTech/ISP VP Dan Meyer wanted to do an experiment with the AeroTech kit plastic parts.

He built a model using the HV Arcas kit as a starting point. He inserted a phenolic tube into the 2.6" paper main body tube which had been slotted to accept the plastic HV Arcas kit fin tabs. The kit payload section was pretty much stock and the nose cone was not modified.

For propulsion this model used an ISP 54mm K1100 motor modified with delay and ejection charge. The K1100 had been designed for ground launching military target drones.

Dan flew the model at Black Rock out of a tower. Blink, and it was gone. Amazingly, the model was later recovered intact.
The nose cone appeared normal but the leading edges of the plastic Arcas fins exhibited some heating deformation.
Estimated performance of the model was Mach 2.

 

[pugachu]

For propulsion this model used an ISP 54mm K1100 motor modified with delay and ejection charge. The K1100 had been designed for ground launching military target drones.

Thanks for the insight. Just curious, how different in design and performance was that K1100 compared to the 54/1706 RMS K1100T that we know and love?

 

[tfish]

LOC 54MM nose cones are tough.
The below old school 54mm min has about 12 flights on K700 and K1275. IIRC best mach was 1.98



The below Estes Fat Boy has 8 'i" Flights on it..mostly I435. Glassed body tube and glass inside nose cone.



Both projects about 23 years ago..

Tony

 

[mperegrinefalcon]

In 1989 AeroTech/ISP VP Dan Meyer wanted to do an experiment with the AeroTech kit plastic parts.

He built a model using the HV Arcas kit as a starting point. He inserted a phenolic tube into the 2.6" paper main body tube which had been slotted to accept the plastic HV Arcas kit fin tabs. The kit payload section was pretty much stock and the nose cone was not modified.

For propulsion this model used an ISP 54mm K1100 motor modified with delay and ejection charge. The K1100 had been designed for ground launching military target drones.

Dan flew the model at Black Rock out of a tower. Blink, and it was gone. Amazingly, the model was later recovered intact.
The nose cone appeared normal but the leading edges of the plastic Arcas fins exhibited some heating deformation.
Estimated performance of the model was Mach 2.

That is really impressive, I would not have expected it to survive that. Thanks