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Unread postAuthor: D_Hall » Fri Nov 20, 2009 11:16 am

Lentamentalisk wrote:Composites (AP) are notoriously slow at igniting, and may "chuff" on the pad for a while before they get up to pressure.

EASY to solve. Damned near trivial in fact. I've never understood why the hobby world tolerates this situation when there are many proven ways to fix it (You don't see the Space Shuttle chuffing!).

Easiest solution: Shaved propellant and a weather seal make for fast ignition.
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Unread postAuthor: Lentamentalisk » Fri Nov 20, 2009 12:54 pm

@D_Hall:
That was some impressive work you did there. But as you noted, there is no way for a rocket powered by estes engines to break the sound barrier, due to the drag. However, with AP, it is possible. Some of the high impulse 24mm Fs and 29mm Gs have a high enough thrust spike to overpower the drag at that diameter. The trick is getting a hold on those few specialty motors with an unusually small diameter, and unusually high thrust curve.

Another cause of chuffing that some TARC teams have noticed, is the cold. Launching in the snow, when the motors have been left out, can cause them to chuff for the entire burn time, so they never even launch, but if the motors are kept in your pocket before the launch to keep them warm, then there is no problem.
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Unread postAuthor: VH_man » Fri Nov 20, 2009 3:14 pm

So basically, It isnt possible?

thinking through it it makes sense... the force of Air resistance is a function of velocity and therefore the faster It goes the more force is required to overcome that force.... Makes sense.

So I guess it's the motorized rollerskis? haha. I actually have high hopes for these.
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Unread postAuthor: blackhawk13 » Fri Nov 20, 2009 3:19 pm

why not a spudgun that can get a small (.5inch) projectile at several times the speed of sound? i could get you time at a 100 yard rifle range.

http://en.wikipedia.org/wiki/Kinetic_energy_penetrator
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Unread postAuthor: ramses » Fri Nov 20, 2009 4:05 pm

one could make their own rocket engines. but that might be pushing the rules. a staged rocket could work, ignited by a hybrid cannon...

about the KE penetrator, I was considering something similar for a science project, only with alternate means of propulsion.
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Unread postAuthor: D_Hall » Fri Nov 20, 2009 10:44 pm

Lentamentalisk wrote:However, with AP, it is possible.

True, but availability can be an issue; especially for a student.

Another cause of chuffing that some TARC teams have noticed, is the cold. Launching in the snow, when the motors have been left out, can cause them to chuff for the entire burn time, so they never even launch,

I'll say it again... A decent ignitor and weather seal will solve that problem.


Ramses wrote:a staged rocket could work,

Not if you're using Estes rockets.
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Unread postAuthor: ramses » Sat Nov 21, 2009 8:02 pm

that is why it integrated in my post about homemade rocket motors.
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Unread postAuthor: Lentamentalisk » Sat Nov 21, 2009 8:17 pm

But homemade rocket engines that are done legally without a Level 2 certification (is that even possible?) are even less likely to have a high enough impulse to break the sound barrier.
As someone under 18 it will not be easy to legally break the sound barrier in any way, but if you are up to it, by pushing the limits, you can probably do it.
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Unread postAuthor: D_Hall » Sat Nov 21, 2009 8:31 pm

Lentamentalisk wrote:But homemade rocket engines that are done legally without a Level 2 certification (is that even possible?) are even less likely to have a high enough impulse to break the sound barrier.

Wow. Where to begin with this one.

First off, a level 2 certification is a TRA/NRA thing. It is NOT a legal requirement at all. It is simply an internal requirement that certain clubs have. Get away from those clubs and get into other more "interesting" clubs and you'll find that "level 2 certification" has no meaning.

That said, it is absolutely *trivial* to break the sound barrier if you're willing to make your own. The equipment required is minimal. Quickest/easiest/cheapest route is to go with zinc/sulfer. I will say that if you've never seen a Zn/S rocket, you're missing out. They are absolutely spectacular. They *explode* off the launch pad. Here, let me link to a pic I took once upon a time (sorry it's blurry, they're damned hard to photograph they move so fast!).

Image

As someone under 18 it will not be easy to legally break the sound barrier in any way,

Now THAT is a fair statement. Being under 18 makes it a lot more difficult to obtain all sorts of things.
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Unread postAuthor: VH_man » Sat Nov 21, 2009 8:36 pm

What about some sort of vehicle I could use at college? I have an old weed whacker motor and a bike.... I assume I could make some good stuff with that. And they would totally go for it at my school.
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Unread postAuthor: psycix » Sun Nov 22, 2009 6:44 am

Sounds fun. Go for it!
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Unread postAuthor: Heimo » Sun Nov 22, 2009 7:12 am

For Amateur Experimental Rocketry may I suggest the following site. its one of the best I have seen

http://www.nakka-rocketry.net/

What about some sort of vehicle I could use at college? I have an old weed whacker motor and a bike.... I assume I could make some good stuff with that. And they would totally go for it at my school.


have a look here this should get your imagination going

http://endless-sphere.com/forums/viewtopic.php?f=28&t=13731
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Unread postAuthor: ramses » Sun Nov 22, 2009 2:36 pm

D_Hall wrote:
As someone under 18 it will not be easy to legally break the sound barrier in any way,

Now THAT is a fair statement. Being under 18 makes it a lot more difficult to obtain all sorts of things.


true that, but you can make your own


http://www.geocities.com/CapeCanaveral/ ... orate.html

it's down now, but it is most likely mirrored somewhere. I really should have downloaded it before. Anyway, you could electrolysize (verb form of electrolysis) some KCLO3 from KCL, heat it until it decomposes into KCLO4 and KCL. Dissove out the KCL with cold , and pull off a a double decomposition reaction with NH4NO3 and get AP.

The last reaction would be tricky since KCLO4 has solubility of 25g/100ml at 100 degrees C. One could follow the above procedure with NaCl and instead, but I can't find a solubility curve for NaClO4...

It should also be noted that an inert (carbon or platinum, don't use carbon with KCL as you won't be able to separate the corrosion from the barely soluble KCLO3). Then you will heat it, and have a few pounds of this happen in your lab. You could skip most of the procedure and use KCLO3 in your own composite rocket propellant.

that website had it all, too bad I didn't back it up. I suppose I should download the rest of my "reference" bookmarks now, too.

this site has some, but it is pushing the limits of the rules based on scope. Rocketry is legitimate so, so

VH_man wrote:What about some sort of vehicle I could use at college? I have an old weed whacker motor and a bike.... I assume I could make some good stuff with that. And they would totally go for it at my school.


but you will need a clutch...
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Unread postAuthor: VH_man » Sun Nov 22, 2009 2:45 pm

ramses wrote:but you will need a clutch...


Weed whackers have centrifugal clutches already attached. There would be no need to devise my own solution.
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Unread postAuthor: ramses » Sun Nov 22, 2009 5:14 pm

really? maybe mine is just stuck...
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