Bare Necessities: N5800 C-Star Flying Case

[butalane]

Yup, it was intact until it hit the ground, and then it only deformed:

The airframe in front of the motor (you can see it as slightly shinier because we polished it) mushroomed out the motor case, and then the fincan slid down and bent over the mushroomed section. The fins did stay on (though they bent too).

That was pretty awesome...

What I would do for a good source of 7076 tube...

 

[REK]

More than likely I was correct about the nose cone coming apart. Of course that happened after the corkscrew event. That is an awesome picture.

 

[CarVac]

More than likely I was correct about the nose cone coming apart. Of course that happened after the corkscrew event. That is an awesome picture.

No, you are not correct. The nosecone is completely intact.

 

[REK]

No, you are not correct. The nosecone is completely intact.

When I mean "coming apart" I meant that it separated not got destroyed. Read carefully...

 

[Coop]

Has anyone, besides CTI, ground-tested the motor? I realize the N5800, to burn on the ground, is an enormous expense and seems rather wasteful, but if you really think the properties of the motor during burn are causing --or at least contributing to-- the many --MANY-- rockets that ended their lives on this beast, wouldn't analysis of that be warranted?

(Fascinated by the discussion, by the way...)


Later!

--Coop

 

[REK]

Has anyone, besides CTI, ground-tested the motor? I realize the N5800, to burn on the ground, is an enormous expense and seems rather wasteful, but if you really think the properties of the motor during burn are causing --or at least contributing to-- the many --MANY-- rockets that ended their lives on this beast, wouldn't analysis of that be warranted?

(Fascinated by the discussion, by the way...)


Later!

--Coop

I myself am thinking of doing the approach of static firing the motor. I will have cameras and such watching the events of the static fire. If anything it really would be a learning curve.

 

[mannyskid]

I don't think the nozzles are eroding away the way you guys think. I'm pretty sure that it is from impact, even from just the massive G force from that rocket impacting the playa and being embedded in the case. My nozzle looked just like yours,



I definitely remember seeing a nozzle sized impact mark on the playa near the corpse of my rocket

I have a fired N10,000 nozzle that is intact and I use it as a paper weight. I have also seen the nozzle of an N10,000 that came in ballistic and was cracked much like both of out nozzles. I have seen N5800 nozzles that didn't have the tail cone closure (ultimate Wildman) that were also intact. I do think that the motor is to blame, I mean look at all the shreds I don't think that the motor is really to blame.....

 

[REK]

Your nozzle looks beat up, if you think about it the impact would have to be the nozzle first to hit the ground. I do not believe the shock force of the impact would damage just the ending of the nozzle. It would have more than likely be destroyed in pieces from such an impact like that. I also do not believe the nozzle has much to do with the shreds of other rockets, but more that something occurs during the burn that causes rockets to rotate. So far out of all the flights I am only convinced by three confirmed rotating rockets. Ground testing this motor is a must in my plans.

 

[Aksrockets]

Ground testing this motor is a must in my plans.

I'd really take Manny's advice on this one. It sounds like he has all the experience to conclude that these failures are caused by the ground.

BAM! Just saved you $1200. I accept thank-you cards, high fives and money. On rare occasions, all 3.

Alex

 

[REK]

I'd really take Manny's advice on this one. It sounds like he has all the experience to conclude that these failures are caused by the ground.

BAM! Just saved you $1200. I accept thank-you cards, high fives and money. On rare occasions, all 3.

Alex

How about I give you the motor casing for warning me lol. $1200 is a crack load. I am still doing it though, I think it would be fun and would not be a waste.

 

[CarVac]

How about I give you the motor casing for warning me lol. $1200 is a crack load. I am still doing it though, I think it would be fun and would not be a waste.

Motor casing, huh?

I was kinda hoping the 6GXL would survive this, but because our aluminum airframe was stronger than the case (stronger material, same thickness) the case yielded upon landing. There went 600 bucks...

 

[mannyskid]

There went 600 bucks...

I know your pain all too well my friend.....sigh.

 

[CCotner]

That was pretty awesome...

What I would do for a good source of 7075 tube...

YES OMG YES THIS PLEASE

I am so tired of spending $100+ on a fricking slug of 7075 and then boring it out to 1/16" WT tube.. 95% of the material is wasted. But there aren't any sources of tube I can find.

 

[CCotner]

I don't know that the motor is at fault. The odd string of observed incidents at t~2.7 s is... unsettling. The fact remains however that it performs just fine on the ground in static testing or it wouldn't have been certified. So, SinfulDarkLord, ground testing one probably won't yield any useful data.

The case is about a foot shorter, now; I wonder if it would be useful as an EX case.

 

[Aksrockets]

How about I give you the motor casing for warning me lol. $1200 is a crack load. I am still doing it though, I think it would be fun and would not be a waste.

Roast some hot dogs and marshmallows while you're at it.
I bet N5800s make some killer smores.
Thats one expensive ground candle.

Dont push the earth out of orbit too much.

Alex

 

[mannyskid]

I bet N5800s make some killer smores.

Naw, an N3400 Skidmark would make much better s'mores. Bits of titanium sponge add WAY more flavor than atomized aluminum....

 

[REK]

Roast some hot dogs and marshmallows while you're at it.
I bet N5800s make some killer smores.
Thats one expensive ground candle.

Dont push the earth out of orbit too much.

Alex

See how much fun you can have static firing it lol? I might as well just try and do that :wink:.

 

[CarVac]

Roast some hot dogs and marshmallows while you're at it.
I bet N5800s make some killer smores.
Thats one expensive ground candle.

Dont push the earth out of orbit too much.

Alex

Don't try it with Mojave Green.

 

[REK]

YES OMG YES THIS PLEASE

I am so tired of spending $100+ on a fricking slug of 7075 and then boring it out to 1/16" WT tube.. 95% of the material is wasted. But there aren't any sources of tube I can find.

I had found a good source, but I forgot to bookmark it. I will keep searching for it.

 

[REK]

I don't know that the motor is at fault. The odd string of observed incidents at t~2.7 s is... unsettling. The fact remains however that it performs just fine on the ground in static testing or it wouldn't have been certified. So, SinfulDarkLord, ground testing one probably won't yield any useful data.

The case is about a foot shorter, now; I wonder if it would be useful as an EX case.

Of course it would be useful as an EX case. It is reloadable is it not :wink:?

 

[3stoogesrocketry]

CCotner , why are you buying 7075 ? Online metals sells 4 inch od .125 wall thickness 6063 t52 for 8 bucks a foot . Chuck it up , turn it down to your 3.9 od and your all set .

Eric

 

[CarVac]

CCotner , why are you buying 7075 ? Online metals sells 4 inch od .125 wall thickness 6063 t52 for 8 bucks a foot . Chuck it up , turn it down to your 3.9 od and your all set .

Eric

6063 is soft and weak compared to 7075, which is much stronger and machines much more nicely. He knows that you can get 6063 cheap (we have made a tube mandrel with that before) but when you want the strong stuff, not much beats 7075.

 

[3stoogesrocketry]

I understand its weaker but ..... It will not fold under thrust .

 

[CCotner]

6063-T6 has a yield strength of at least 23ksi and is intended to be used for decorative purposes, like window flashing.
7075-T6 has a yield strength of at least 63ksi, and is intended for aerospace structures.

That difference in strength (and corresponding differences in stiffness, and in compression vs tension) are what allows engineers to make lighter structures for equivalent loads. That's how we (try) to increase performance.

 

[warnerr]

https://www.aerospacemetals.com/aluminum-distributor.html lists 7075 tubing

 

[3stoogesrocketry]

Ok , so if your worried about compression , use 2024 . It has a yeild strength of over 53ksi , is 23 percent lighter then 7075 , and 15 dollars a foot What is your maximum compression load under thrust ?

 

[bobkrech]

Ok , so if your worried about compression , use 2024 . It has a yeild strength of over 53ksi , is 23 percent lighter then 7075 , and 15 dollars a foot What is your maximum compression load under thrust ?

matweb.com is your friend. 7075 = 2.81 g/cc, 2024 = 2.78 g/cc, 6061 = 2.70 g/cc. 2024 is only ~1% lighter than 7075, 6061 is ~4% lighter. The strength of aluminum depends on the heat treating, however all common aluminum alloys rapidly looses strength above 200 C.

 

[3stoogesrocketry]

Yes Bob typo on my part . My book says 2.3 . Yarde is also a good source for 7075.

 

[CCotner]

Yarte Metals does not sell 7075 tube of any kind or size. AerospaceMetals didn't have anything in stock that was even close to the right sizes. I was unable to find 2024 tubing with a thick enough wall to machine it to the needed dimensions.

 

[3stoogesrocketry]

Have you tried Yarde ?