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Model Rockets and GPS Tracking

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Michael W.

Tue Nov 28 2006, 12:01AM

Registered Member #50 Joined: Thu Feb 09 2006, 04:07AM
Location: Vernon, B.C, Canada
Posts: 324

The take off reminds me of a land to air weapons missile....

...

Sat Dec 02 2006, 03:55AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Unfortunately that is what the ATF (that 3 letter government agency responsible for regulating such things) thinks too... I hope that we eventually beat them in court and get APCP declassified as an explosive (because it isn't one to start with; burn rates are only like 1cm/s for really fast motors), but then again we have been fighting for years and it has only resulted in more restrictions

In any case, sorry about taking so long to get these pics uploaded, been busy with school

4 tests taken since Monday and an essay on some random history related topic due Tuesday. Just did a speech on why hobbyists should be able to buy APCP 2nd period...

In any case...

The ground support equipment...

overall view of the GSE and the homebrew launch pad we made

The launch controller and the box with all of the hybrids stuff

The odds&ends, and my ever growing assortment of motor casings

the rockets we launched last week and the rest of the current models.

We also have a box of broken rockets and a box of random parts but they aren't really worthy of Chris's bandwith

I want to post a pic of my class 4 magazine packed to the brim with motors/igniters (hopefully all legal) but there is a nagging feeling that posting a pic of my explosive stockpile on a public forum isn't the best idea

If anyone asks I gave it to John.

Post is getting pretty big, after the next post I will post pics of the motors in better detail.

Self Defenestrate

Sat Dec 02 2006, 04:02AM

Registered Member #87 Joined: Thu Feb 09 2006, 01:36PM
Location: San Jose
Posts: 191

Is that an 18mm casing in the far upper right, in your motors pic? Where do you find reloads for it? And whats the big guy on the bottom of the pic? Looks hybrid.. sweet collection.

...

Sat Dec 02 2006, 06:04AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Argg, I had this whole post typed out but I was spell checking and somehow I hit backspace outside of the text area and lost it

That is an 18/20 aerotech casing. A quick google search should bring up a variety of hobby stored selling the casing ($30ish) and the reloads ($10 for 3 D's)

In any case...

going down the stack of motors from top/bottom I have:
1. 18/20 aerotech casing. The 18 stands for the diameter of the motor (in mm) and the /20 stands for the total energy that casing can store (20newton/seconds), which is the standard method of identifying reload casings from aerotech. The reloads are identified the same way a 'normal' single use BP motors are; letter for the class of total impulse (a/b/c/whatever) followed by the average thrust (newtons), dash, delay from motor ignition to ejection charge firing (seconds). The primary use for this motor is to put a D motor (in a 25mm casing) into a motor mount made for a a/b/c motor (18mm casing), which is made possible by the higher energy/volume for APCP over BP. Casing costs $30 and reloads are $3.

2. 29/120 casing aerotech casing. This is the standard mid power rocket motor. You can get e/f/g reloads for it, and it does not require any permits to use. The casing costs $60 and reloads cost from $5-$15 depending on size.

3. 38/240 casing. It can use H reloads. This is an entry level high power motor, Because of that it requires a variety of permits, primarily a LEUP from the government and a level 1 certification from Tripoli or the NAR to buy it. Unless you buy/launch it at the same launch then you can skip the LEUP, and you can skip the certification by having a teacher inspect you rocket and be present when you buy the motor (if the rocket works then you are certified). The casing costs $30 and the closure (for/aft) are $30 a piece. You can use the closures for all 38/whatever motors. Reloads are ~$20 a piece.

4. pro38 3g casing. This is a newer motor design, that does not require the closures (so the casing is cheaper) and has preassebled reloads (instead of the 10 minutes of rocket science to assemble an aerotech motor). The N-g's refers to how many 3" long slugs of APCP is in the motor (all companies cast the in small pieces). This uses 'baby' I reloads, meaning that they are at the low end of the I certification class. The casing is $60ish and the reloads are ~$35

5. pre38 4g casing. This is basically the same thing as the 3g, but 30% bigger

Casing is like $80 and reloads are ~$45

6. This is the most powerfull motor I have (by 20%). It is an aerotech 54/1280. Yes it is 2" in diameter, and yes it has 1280n/s of total energy. That means it can put out 100lbs of thrust for 3 seconds. (I wish I could convert that into joules for all of you coilgunphiles...). It requires a level 2 certification, which means take a test and then launch your rocket. The casing costs $60, and the for/aft closures are $35 a piece. Reloads are $70ish a piece.

7. Hypertek Hybrid. This is where the true rocket science starts... This motor consists of 3 main parts. There is a 835cc spun aluminum tank (top) the steel 'injector bell' (the magic piece), and the reload that screws into the bottom. The motor works by... In the injector bell you have a 1/4" hole, with an o-ring in it. You slide a piece of 1/4" stainless tube into this hole, and hook it up to your N2O tank. there is a small vent tube in the motor that allows the N2O to be pumped in by the pressure of the tank. Once the motor is full, you get liquid N2O out the vent, which makes a nice plume. Then you also have a 3/8" tube around the 1/4" tube that you pump gaseous O2 in with, and pressurise the motor chamber with 50psi of pure O2. Then you have a small piece of normal 24awg stranded speaker wire, cut flush, hooked up to a 7.5kv/30ma NST (SSNST). To fire you hook up power to the nst, which makes a spark in the O2 atmosphere and starts the PVC burning (this is actually quite powerfull, and to the untrained eye it would appear that the motor is already ignited.) This burns through the plastic zip-ties that are holding the 1/4" tube in the seal, and lets the N2O flow and start the motor. The motor + 3 reloads costs $200 (bundle) and reloads are $30 a piece. Also needs a liter of N2O ($5/lb) so that works out to $10-20 of N2O (depending on how much you vent).

8, This is a new brand of motor (I have serial number 004). These motors are considerably simpler than the hyperteks, but work just as good. They only have a single tube, which has parts slid into it. First, you slide in the forward closure, which has a vent in it. Then you slide in the 'floating closure' which has a piece of 1/4" nylon tube going through it. then in goes a PVC grain (1" sch80 pipe) and a graphite nozzle. You then hook the nylon tube into your N2O tank and fill. You can ignite it either by having a piece of APCP in the top of the motor, or using the O2/HV that the hyperteks use. (it exploded using the first method, so we are using the second one now). Once you have the motor running off O2/PVC then it burns through the nylon fill tube, releasing the N2O into the motor and it ignites. Casing is $200ish, reloads are $10ish + N2O cost.

BTW, you can see a decent walk through of the assembled GSE in the video linked as 'flawlessly' 5 posts up, or the second thumbnail from the left at the bottom of the post.

...

Mon Sept 10 2007, 05:02AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

UPDATES!

To replace rev2 (which died such a horrible death last thanksgiving), I have been slaving away on rev3, making it smarter, more powerful, and with more sensors!

I broke out my dev tools spring break last year, and have been working on/off on the software/hardware since. I decided to use the same transceivers and GPS that I used in the rev2, but added the folowing:
* PIC18f2550 microprocessor running at 25MHz (software configurable to 48MHz if need be)
* AT45DB321D 32Mbit flash chip for data storage, 10hours at 100samples/sec
* LIS3LV02DQ 3 axis +/-6.5g accelerometer .01g resolution
* MMA2202G +/-50g z axis accelerometer, .5g resolution
* MPXA4115A6U Altimeter, 10ft resolution
* MAX1763 and ADP3339 5v boost converter and 3.3v linear regulator for the 5v/3.3v buses

So I started work on a prototype, and getting some code done using this monstrosity...

I ended up doing the schematic at work, during my '20%' time that ended up being more like 80% since there wasn't anything for me to work on

It wasn't easy, but I managed to cram it all into a 1.5" by 4" 2 layer board...

Which I then tried to etch myself

But I mirrored the wrong side of the board, so then I decided to work smarter not harder and send out to batchpcb. $30 later I was here:

Then I used my hot air station to solder the stack of parts onto the board. And then I spent most of the weekend debugging, amazingly enough not a single one of the components worked on the first try, the pic had a severed clock line and was missing a pullup in the mclr line, the power supply had a miscalculated resistor, the GPS was missing a pullup, the transmitter had the !shdn line tied low instead of high, the 50g accelerometer was rotated 90degrees (so it measured acceleration in the wrong direction), the 6.5g accelerometer was also rotated (ie, pin 1 was on the pin14 pad), the dataflash had the di/do pins swapped, and the altimeter was missing the pullups on the I2C buss.

Luckily I managed to fix all of my mistakes (I blame them on most of the development being done between 9pm and 1am...) with only a few jumpers, and only the ones for the altimeter weren't covered up by something else.

Behold...

I hope to launch her in the middle of October, and if things go well I should be able to hit about 8k feet pulling nearly 40Gs and hitting over mach in Krazed III using a J800 motor

BTW, 1337th post

...

Thu Apr 10 2008, 05:40AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Mixed news on the gps tracker front...
The Good:
It flew 4 times, and I got a good bit of data out of it :)
One typical flight's data is shown here:
Altitude data:
Altitude 1

Accelerometer data:
Acceleration 1

(not that these graphs were made with the 1hz data sent down the up link, because I never had time to get data stored in the flash memory--that should be working by the time I fly rev4 this fall Also the altitude hasn't been calibrated yet, and it reads about 10% low)

The Bad:
The 4th flight we lost sign of the rocket and the tracker crapped out at apogee, and after a day of searching we just couldn't find the rocket

For the rest of the data and more information about the rocket and the tracker see their respective webpages. rocket and flight data tracker

There is a rev4 in the works, this time with a lot more effort into making sure the damn thing actually transmits something for the whole flight...

Dr. Shark

Thu Apr 10 2008, 10:10AM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

Two comments: First, this is an absolutely awesome project, I am glad you gave it a bump to the top, otherwise I probably wouldn't have looked at it. Really motivates me to put more work into my projects, but probably I am just too old, meh! I looked at some pages about rocket candy rockets, I suppose I should figure out what the laws are like in this country and look into rocketry myself. As a kid I played with the Estes engines you get at hobby shops without any permit (A, B and C class?) but I guess real rocketry is a very different game.

Second, it sucks you lost the rocket, really sorry for you. I was wondering though, how do people with no GPS trackers find their rockets? Or is it common to sacrifice them after just a few flights?

...

Thu Apr 10 2008, 07:43PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Thanks

You are supposed to be able to just watch them go up, possibly loose sight of them for a few seconds until they eject their parachute, watch them fall to the ground and just walk over to pick them up.

The problem is that this is such a small rocket (in comparison to the size rocket normall launched on a K motor) that you can't see it at all, even the parachute it ejects at apogee is only 18" in diameter; I am not even sure if a human eye is capable of seeing something that small a mile away.

The 'standard' method to deal with this is to put a small transmitter on the rocket, and use a directional antenna to figure out what direction the rocket goes in, but I decided that I would take it a step further and send data back down through the radio, which evolved to the system I have going now.

If only I could keep it working for the duration of the flight...

Dr. Shark

Fri Apr 11 2008, 04:29PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

So you gave up any hope on finding it? I am sure that's a lot of money down the drain, with the commercial hybrid motor you had in there and all the electronics.
But on the bright side, you still got all the PCB artwork and ÂµController code, so probably rev4 should not be too much work, right?

Actually I am really curious about the hybrid motor you were using. It's a N2O / cellulose motor, right? I was wondering why that is the fuel of choice, since the N02 probably needs to be stored in a pressurized container, whereas other fuels such as H2O2 or N2O4 are more or less liquid at room temperature. Is this because you don't need a fuel pump, because the pressure is sufficient to force the fuel into the burn chamber?

Lots of questions, I have actually tried google but I could not find too much information. If you know a page that has a few good articles about hybrid rockets, a link would be appreciated!

PS: Make sure to check out this guy

that must be teh awesomest 1337 rocket evah!

...

Fri Apr 11 2008, 05:59PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

It is estimated there was roughly $1000 invested in krazed III

As to rebuilding the tracker; I do have a spare PCB and most of the sensors (would still need to buy a new gps and transciever), however I am taking this oppertunity to redesign the tracker as to be more resistant to these intermitant failures. Mainly, there will be no connectors on the board (save for screw terminals to connect an arm switch and the pyro charges), the antennas and batteries/chargers will be integrated into the device (to keep up with the no connectors rule), and more modern components will be used (which will cut the cost from $500 to about $250 in parts). Luckly I will be able to reuse a lot of my old code, and the experinece I gained in building revs 1-3. I am also going to focus more on watchdog timers, interupts, etc, etc, to make sure that the code doesn't freeze anymore

There is a little bit of info on the motor in an earlier post (item 7 of the post on 12/2/06), but is is actually a N20/PVC motor. I am not sure why we switched over from cellulose, I believe the total impulse is very similar between the two, it probably comes down to the fact that you can easily mould/machine pvc but paper is tricky. We use N2O because it is just the right pressure for what we are doing (about 750-1000psi at room temperature) so the motor is self pressurising. Also, pund for pound there is a ton of O2 in there (about 30% O2), and per $ you get a lot for your money (about $10-15 per lb O2). It is also very stable, in order to get it to decompose into N2/O2 you need to heat it to a few thousand degrees, unlike H2O2 which can explode if you just look at it wrong. Not to mention the fact that you can get your tank filled at any hotrod shop

this guy has a lot of info about hybrids, or you could look at some of the manufactures pages

It a shame that H2O2 rocket couldn't be launched, on the bright side there are a few projects that are almost as large going up at BALLS in september. Some of those rockets are scheduled to hit in excess of 100kft, and I believe some of them are going up as high as a 'S' class motor (ie, the mootor I flew krazed III on was 1,000n/s, an S is 1,000,000n/s

)

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