Bare Necessities: N5800 C-Star Flying Case

Issus said:

Which GPS are you planning to use? Be aware that most MTK and Sirf based GPS units will not function at all above 60,000ft. A Venus chipset and some uBlox are the only ones i know of which will, through having actually putting them up that high (with balloons). A Venus638 will most likely get a lock within a few seconds of you leaving ITAR restrictions, I don't know of any other GPS that wont take several minutes to come out of ITAR.

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If you click on the link in the first post of this thread you can find a lot of information, including this, about the design. They've got this covered.

CCotner said:

I agree wholeheartedly with Kevin on this one. Attention to detail is everything. However, if we re-make a new nosecone, we'll have to either make it from carbon fiber (sacrificing everything possibly because of GPS problems), or order more of the e-glass/basalt hybrid from Soller composites-they took ages to ship to us in the first place. Which means we can't fly in the 2012 flying season at Black Rock (and remember there's a minimum 60 day if we file our own waiver under the university rules). We would be inelegible for the N5800CS record prize, which would in all likelyhood be claimed by Bryce or CJL anyway. We fly with this nosecone.

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Not trying to be a downer here, but this sounds like a classic case of Go Fever. I've seen many a project fail, all because they just had to get in that one last flight.

sylvie369 said:

If you click on the link in the first post of this thread you can find a lot of information, including this, about the design. They've got this covered.

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Ah, i couldnt look at the link when i posted as I was on my phone.


I would suggest ordering the glass/basalt hybrid, call them to tell them its urgent - and do your patch. If it arrives in time to make another nose cone you're all set. If it doesn't then you can risk using the current one.

Instead of microballoons, I would've used fumed silica. Beyond that, I think you've done what you can for this nosecone.

-Kevin

Nothing is real without photo's!

Rocketman248 said:

Not trying to be a downer here, but this sounds like a classic case of Go Fever. I've seen many a project fail, all because they just had to get in that one last flight.

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I'll say that it's not 'Go Fever', but rather a rational decision based on expected value of the flight. Basically, the reason we committed to the project was the expectation that we could win some prizes. Yes, it's somewhat greedy, but we're also (newly-)poor college students.

Plus I have confidence in the integrity of the nosecone's core, based on tap testing. If the outer layer peels off, I think it's unlikely to compromise the internal structure, since exposed leading edges of the basalt fabric are nonexistent. Our only qualms were that any peeling-off of the outer layer would induce asymmetry that would hurt stability.

Great project!

alexzogh said:

Nothing is real without photo's!

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Here are some. And a link to FB with more photos.
https://highpowerrocketry.blogspot.ca/2012/09/bare-necessities-n5800-competition-entry.html

Jeroen

Rocketman248 said:

Not trying to be a downer here, but this sounds like a classic case of Go Fever. I've seen many a project fail, all because they just had to get in that one last flight.

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I think in this case it's more of "Calculated Risk" -- they recognize the ideal, but it fails in other parameters, and coupled with their analysis of the existing nosecone, they've determined the risk isn't sufficient to postpone the flight.

-Kevin

troj said:

I think in this case it's more of "Calculated Risk" -- they recognize the ideal, but it fails in other parameters, and coupled with their analysis of the existing nosecone, they've determined the risk isn't sufficient to postpone the flight.

-Kevin

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That's exactly what it is. There's less and less reason for us to fly unless we fly now, and we're reasonably sure the nosecone will be fine now. It is impressively tough, stiff, and the skin is covered in a smooth coat of epoxy everywhere (the high-temp stuff) as well as a layer of ablative microballoons.

For those who care, I isolated the probable cause of the lamination failure in-mold. We used a machined aluminum 2-part (female) mold, laid up fiber on the inside of said mold, and then pressurized the interior of the mold with expanding foam (GLR's megafoam) in a balloon. We've done this successfully several times in our smaller, machined 38mm nosecone mold (our original plan for the summer was to take the J record with a design exceptionally similar to Curt Von Delius's brilliant JMAX) with great success. We used balloons made of a very thin, very stretchy latex material that were fairly close to the right size for the mold to begin with.

Not only was there considerably more fabric to squish outward this time, the fabric was considerably thicker. I think what happened is that the 2nd or 3rd layer bubbled away from the surface slightly as CarVac laid it, and the others stuck to it; thus the balloon would have had to slide all the subsequent layers past each other to get them laying flat. We used a standard party balloon this time rather than our previous balloon because the previous one seemed too small. The balloon was not nearly so stretchy and the foam probably used most of it's expansion pressure (so to speak) stretching the balloon rather than applying pressure to the laminate.

What do you have for the final mass of this nosecone?

It is going to be heavy. Before the surface treatment and without the internal tube, it weighed 4 pounds and 11 ounces.

CarVac said:

It is going to be heavy. Before the surface treatment and without the internal tube, it weighed 4 pounds and 11 ounces.

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That's OK. You guys clearly have as a top design objective, survivability. Chris on the other hand, has a divergent and challenging goal set of both survival and achieving an N-record flight.

CarVac said:

It is going to be heavy. Before the surface treatment and without the internal tube, it weighed 4 pounds and 11 ounces.

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Sounds like a beast! Does it really sim to 110K with almost 5 in the nosecone and I presume a few more in the finacan recovery and airframe?

CCotner said:

snipped...As CarVac mentioned, the nose cone tip is steel. .....

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Where do you intend to launch? A steel tip will not go at a TRA launch.

Mark


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MClark said:

Where do you intend to launch? A steel tip will not go at a TRA launch.
.

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First of all, it has already been approved to fly at XPRS, and the documentation we posted to the AeroPac board clearly stated the tip design. If it becomes a problem, we can last-minute CNC a beryllium-copper tip. Second, though, it really wouldn't make the slightest difference; the non-ductile metal concern is primarily for motor cases and fins which could fragment (think shrapnel) in a CATO. If it falls on something, it won't matter what it's made of, the 12 pound motor case will core-sample through a car regardless of what's on the top of it.

I agree in reality it does not matter. The issue is the insurance for the entire launch is voided. The call if it is OK must be made by the TRA BoD.

Mark

New Ocean said:

Sounds like a beast! Does it really sim to 110K with almost 5 in the nosecone and I presume a few more in the finacan recovery and airframe?

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It simulates to 115,000 feet with 13.5 pounds other than the motor. The fincan is really shockingly light; the tailcone is practically air. It's just the metal parts up front which add up. But because of that, and because the nosecone is so long (28 inch [7.2:1] conic, for minimum high Mach drag and minimum CP shift), it doesn't require fins as large as competing rockets to remain stable at Mach 4. Thus, our drag advantage makes up for the weight disadvantage. (This is CarVac on CCotner's computer.)

115K on an N! Still hard to wrap the mind around that concept. Do you have a simulation output, graph etc for this?

I find it interesting, given our almost completely different design approaches, how close the sims actually are (mine's simming 115k right now too). I'll definitely be interested to see how yours does, especially given the smaller fins. Do you have any plans to coat it with some kind of high temperature paint or anything like that, or are you flying the rocket bare? Also, have you considered an aluminum tip? The high thermal conductivity and low stress should mean that the heat won't be a problem for an aluminum tip, and that completely eliminates the insurance issue.

Just a little trivia mixed with my own opinion...

I believe most problems with GPSes are the reality of flying a hundred dollar consumer device, not enforcement of COCOM limits. These tiny devices are not up to the task of operating in a high G, high velocity, rapidly changing environment and they freak-out. Adding redundant units in a tight space frequently aggravates the problems and does not increase the odds of recording a good trajectory.

(ask yourself why so many of these devices fail to re-acquire lock even after the rocket slows and approaches apogee)

-->MCS


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MCS said:

(ask yourself why so many of these devices fail to re-acquire lock even after the rocket slows and approaches apogee)

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I always thought that was because it was over 100,000 feet.

I'm not going to lie. I think Chris and Mudd are no way going to hit above, 100k. I mean think about it. I know this motor is something else, but people have been flying N motors for years and so far have yet to break 50k. To say that you will exceed it by double, no way.

Perhaps you guys already know this, but RASAERO has its fair share of glitches to. Just like how Rocksim miscalculates Mach+ flights by assigning a cD that makes no sense.

RASAERO has a problem with the double wedge or hexagonal feature. If you put in a swept distance of like 3/4 (very steep angle, steeper than CJLs before he did air foiling) and by changing the number very little, I get from 60k (what I expect) to 80k (the limit I think is possible) to 200k (absolute crap).

Please don't post anything about the above, it is my opinion, leave it.

Between the three of us (Chris, Cotner, and myself). We are all taking radically different approaches.

Chris is attempting the composite rocket. My best friend is a composites expert and really wants to fly and 3-4" all composite bird. There are certain constraints that forces you to have, great. More power to you.

Mudd has a rocket that is a machinists rocket. well engineered, unique and beautiful machine work. Lack of commercial components is what makes your project truly one of a kind.

Mine is in my opinion more simple, (KISS) nearly all commercially available (except fins). The main ingenuity comes from the work on the fins. It's basically a upscale Space Cowboy airfoiled with radial taper then tweaked to our dimensions. Made out of aluminum.


Three extremely different ways to skin a cat. But we each have to get that cat under control which has yet to be done.

I hope we all make it and we can see what kind of altitude is possible with this motor.

Carry on.

Bryce

bandman444 said:

I'm not going to lie. I think Chris and Mudd are no way going to hit above, 100k. I mean think about it. I know this motor is something else, but people have been flying N motors for years and so far have yet to break 50k. To say that you will exceed it by double, no way.

Perhaps you guys already know this, but RASAERO has its fair share of glitches to. Just like how Rocksim miscalculates Mach+ flights by assigning a cD that makes no sense.

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Ahh, but my prediction doesn't just come from RasAero. It also comes from Ansys Fluent. I'll be the first to admit that the altitude sounds outlandish, but at the same time, at this kind of speed, small changes can make enormous differences in performance. Also, I believe it's been rehashed a few times already, but the N5800 is a bit different from the N motors which have been flown up to this point for altitude records, so comparing this to the existing N record isn't very relevant, if you ask me. In addition, there have been sounding rockets which achieve incredible altitude on very little power, indicating that it should indeed be possible, though difficult (since we have somewhat more stringent recovery requirements than they did).

If it hits mach 4, a reasonably heavy (yes heavy) airframe with a 20:1 length to diameter ratio should have no problem hitting 100,000 feet. If this rocket burns out at 25 lbs and mach 4... It should coast very well indeed.

I just threw some numbers at Rasaero and the results are well over 100k without any optimization.
If it does not wiggle, come appart or have the CD go to heck because of the nosecone becoming rough...............
.....it will go over 100k

Mark

CarVac said:

We are not sure. Your mention of it in your thread was the first time I ever saw that there was a firmware revision to fix it. We had initially planned to use timers for apogee, but we might use barometric if it will not experience the bug.

Can the firmware be downloaded somewhere?

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Raven firmware can't be updated in the field.

Please don't fly without checking with Adrian as to the version you have and ask him to review your planned configuration.

mikec said:

Raven firmware can't be updated in the field.

Please don't fly without checking with Adrian as to the version you have and ask him to review your planned configuration.

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it cant?

cjl said:

Ahh, but my prediction doesn't just come from RasAero. It also comes from Ansys Fluent.

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Missile DATCOM agrees, too.

cjl: Does your rocket sim to the same ~130,000 feet in RASAero?

Also, bandman444, one reason ours sims so much higher than yours is the fact that we have an extreme tailcone that necks down to barely larger than the diameter of the nozzle (and in my understanding, yours does not). At the current optimistic weight estimate of 11.6 pounds (we just redid it), it sims to about 119,000 feet. Without the tailcone, it sims to 93,000 feet.

CarVac said:

cjl: Does your rocket sim to the same ~130,000 feet in RASAero?

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Yep - depending on the details (RAS doesn't like a spanwise thickness variation on the fins, so I've tried adapting for that a couple of ways, but it's anywhere from 100k up to 140k, depending on how that's entered as well as depending on launch site conditions).

CarVac said:

Also, bandman444, one reason ours sims so much higher than yours is the fact that we have an extreme tailcone that necks down to barely larger than the diameter of the nozzle (and in my understanding, yours does not). At the current optimistic weight estimate of 11.6 pounds (we just redid it), it sims to about 119,000 feet. Without the tailcone, it sims to 93,000 feet.

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A tailcone makes an enormous difference, that's for sure.