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4hv.org :: Forums :: Projects
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Model Rockets and GPS Tracking

Author Post
Fri Apr 14 2006, 12:45AM Print View
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2435
Because it appears that there are some people interested in the rockets that this GPS flies in, I have made a post (8 replies down) that goes into detail about their construction and the ground support equipment that is needed to make them fly. Title changed to keep things on topic

continued from here

So I tried 'scoping the power coming into the xecom modules, and the ripple was vary small (like 2mv), not that it would do any good since the xecom people refused to give me a ripple speck because it 'was very complicated'. So I built the clc filter outlined in the product manual, and the ripple stayed about the same. But then I tried sending some data out the link, and noticed that whenever the things starts transmitting it drops the voltage by ~.1v. (.6v of that being dropped across their 'filter').

So the project sat for another couple of months

Then for my birthday I got a maxstream xtend dev kit These modules also claim 20mi open/3kf suburban range, despite the fact that they have 2x the transmit power (1w) and 2x the sensitivity (-110db). Unfortunately I had to turn down the power to make it work off 3.3v (only .5w is supported) and the rx sensitivity (at the 115kb/s it is only -100db) so I was back to what the xecom's claimed. But these guys didn't have the range problem :) When I was trying them I had them at opposite sides of the house (where the xecom's barely connected) and they stated ~90% signal strength. So I decided they were a keeper, and made up a prototype

(that is it without the modules/battery)

And when that worked, I designed up a board.

I will try to save the bloody details, but let me say that I started by installing eagle around 12noon with the intention of sending it to sparkfun to have it made, and at 4am I printed it out just to see what it looked like. Then in my sleep deprived lack of judgment I decided I would make it the first board I ever etched. And went to sleep.

About 4 hours later I awoke, and prepped a piece of Cu clad. Around 12noon I boiled 170ml of water, measured out 42.5g (NH4)2SO4, dawned the goggles and headed outside. About 10 minuted later I was here

Then I grabbed my cordless drill and .1" hs steel drill bit and started murdering the board. (it was the best I could do, my next board will be drilled using a makeshift dremel drill press). Then I started populating the board, and after making a few major changes to the routing I was here (about 8:00pm now)

So then I put it all together

And the obligatory next to a coke can pic

This was all finished last Thursday, but it was today that I finally got around to giving it a real range test. But the manual says 3kfeet in suburban, so with 1/2 tx power and 1/2 rx sensitivity, I would expect 1/4 that (~0.15 mile)
So on my way home from school I powered it up and got this map after I imported the data into topo!

(that red like at the bottom is .1mi) and did a measure from the furthest point to my house, and got .15 mile (actually I measured then calculated, and was very surprised when I got exactly the same number). This would suggest that it is 5mi open range. This should be plenty, since the rocket only goes 2mi (hopefully higher, but probably lower), and even it it does go out of range you just drive closer to it and once you get close enough the link automatically reconnects.

I should get a chance to launch it the third Saturday of June.

Some specks
w/ out battery - 2.99g
w/ 2A/hr battery that will give ~15 hours of tracking operation - 5.50g
size -
diameter - fits in a 1.5" tube
length - 2.7" long just the tracker, 9" long with battery/antenna
cost -
finished module- ~$200
total spent ~$700
suburban - 3kfeet
open - 5mi?
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Tue Jun 20 2006, 09:42PM
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2435
I finally launched it And it worked

You see, real Krogens spend fathers day out in the desert in the 110F weather playing with rockets and the dune buggy your dad traded for a wallpaper steamer 20 years ago that you got out there in the trailer you got for fathers day... In any case, the scorching heat didn't affect the launch too much, the only problems were that anything metal was too hot to touch and we had to put the N2O tank (for the hybrids) in a ice chest to get the pressure down below 1kpsi...

But the gps worked great... I got a chance to launch it in 'my brothers' (the airframe was given to him for christmas, I designed it, he assembled it, and I do the rest) rocket off a 328N/s motor and a 556 N/s motor, and I launched mine twice off my 1022N/s N2O/PVC hybrid motor. The gps lost lock at liftoff/landing (due to high G forces and emi from the ssnst we use to ignite the hypertek), but I got a ton of good data and proved the system works

Attached is all of the goods in excel format. If you have problems with them, let me know and I will try to get it in a format that works for you. There is a spreadsheet for each launch (the rockets labeled peter are my rocket which is a 4" diameter, 7' tall beast weighing in at about 10 lbs being powered off the 1KN/s hybrid, the ones labeled erik are my brothers which is a 1.5" diameter, 8' tall skinny thing that weighs about 5 lbs and was launched off a NH4CLO4/rubber composite the first of which was a 328N/s and the second was a 556N/s), the first column is the gps time in seconds since the beginning of the week, which is followed by long/latt/elev, which if followed by the speed, then by the gps health (the numbers are sorta meaningless in decimal format, generally the higher the better), then an empty column showing the end of the data from the gps. The next 3 are ones I made to make the data more readable (to me at least) which gives the altitude in feet above ground level, speed in mph, and the change in speed converted to G's (take these numbers with a few grains of salt, as the speed on the gps isn't really all that great at the high G events, which it would be interesting to know the value). The last column is comments I added. The ones that refer to parachutes and deployment are referring to the second parachute that deploys at 800ft agl to slow the rocket to a more reasonable speed (looking at the speed chart shows this quite clearly). There are 3 charts in each document that show the data in a graphical form. The last one is a composite of all the graphs overlaid on top of each other so you can see how performance changed with each launch. I did a little bit of shifting the data around to make the results easier to compare.

This all corresponds quite nicely to what rocksim said the data should be. For my rocket it said the max speed should be 111m/s, the measured was 115m/s for the second launch (I think the that first launch was having some gps problems all around, all the data seems a little off, or the fill was bad, one or the other). The max altitude calculated was 2100ft, the measured was 2200. The max acceleration was calculated as 12.3g, I measured 11.8g. Pretty damn good
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Sat Nov 25 2006, 05:15AM
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2435
Not a SINGLE reply? What is with you people... I mean I have explosives, chemistry, electronics, wireless communication, heck there is even a little HV involved

In any case, I just wanted to make note of the launch earlier today (even if it only for personal reference).

It didn't start out too good. We drove out, set up the pad, loaded the ejection charged, fired up the GPS, filled the N2O tank, fired, all looking good.
10 seconds later
'chute should be coming out about now...
5 seconds later
sh*t sh*t sh*t wizzzzbrrrrrr
5 seconds later
(and I have GPS data to show that it was only a 20 second launch)

sorry no pics yet (still need to unpack the camera) but the nose cone made out of 1/8" think PVC just crumpled like an according and buried itself ~8" into the dessert rock-sand (anyone that has been to the Mojave knows what I mean, it is not quite sandstone but it is getting there). The tube shattered (almost all of it). The motor got shot out the back of the rocket ~12" (ripping a 1/4' birch plywood bulkhead that had been fibergalssed in). I believe that this occurred as the rocket crumpled and created a pressure surge when it impacted. The circuit board responsible for controlling the data completely shattered. Worst of all (because I wanted to use it later that day) was what happened to the GPS system. The (lithium ion) batteries were literally in a ball at the bottom (there was a 1/4" solid steel rod at the tip of the nose cone to keep the gps from sliding forward; it is now bent at a 30degree angle). The ceramic patch on the GPS antenna slid down 1/8". The metal shield around the GPS board was smashed pretty good, but the only damaged to the board was a few lifted traces where the connector was soldered on. (but it is enough damage that it will not fly again). That board that I slaved away to produce will never fly again either. I am thinking about framing it A few lifted traces, the plastic on one of the caps is missing, a few busted out LED's, the connector for the maxsteam module dead. Fortunately the maxstream module survived! The antenna was wrapped up in a ball with the batteries, but I am pretty sure that it will indeed fly again (one of the 4 pieces that survived--the motor retainer ring, the motor (I think, need to pull out the tank and give it a good inspection) the maxstream module, and the charge canisters). I hope to find enough time to redesign the board to have some 'normal' senors (pressure/accelerometer) that will just be logged into a little flash memory that can be downloaded at the end of a flight (I only need the gps data realtime so that I can find the rocket afterward) Maybe during christmas, or possible even spring break again.

RIP Crazed II

Enough bad news...

Not to be discouraged we launched the small(er) rocket on the last conventional (Ammonium Perchlorate Composite -- 200g of it that burns in 2seconds) that I will get for a while (well, until my dad gets a LEUP). Because we had never managed to get the 'chutes to deploy properly, a complete redesign was in order. Instead of having a 'chute fire at apogee and one at 800' AGL we just had a chute that fired at apogee, and a charge connected to a 20 second timer in the same tube. This worked flawlessly, and it was dead calm so we decided to run the West Coast Hybrids (.com) J motor that I got 2.3 years ago (for the second time, the first time it exploded, so Scott send me a new ones, which sat until I had a rocket I could use it in). It was supposed to go about a mile, and possible hit mach. So I spent a while carefully assembling it (I wanted to make damn sure that it didn't explode again, I wasn't looking forward to building 2 rockets and a gps tracking system) and put it on the pad.

Opened the N2O valve, O2 tank, hooked up the NST... Walk back to the controller... Starting to form butterflies in my stomach... Press that arm key... Flip the N2O switch... Watch for the stream of N2O... Butterflies unbearable... Nice N2O cloud... 5-4-3-2-1... Hit BRB (big red button)... Nothing... Just the hiss of the O2. Sh*t. Well better than it exploding I guess

Pull motor apart, igniter wire isn't burnt. Hmm... Check HV, good... Check wire... Good... Put rocket back together. Fill, fire, nothing. Double sh*t.

Pull motor apart. Notice that all of the parts are freezing cold (actually colder than freezing, ice was slowly forming due to the sub 10% humidity). Only one reason for that; N2O leak. Pull floating injector out... All covered in sand Who put that in there Pull motor completely apart and clean. Reassemble. Fire. Nothing Getting pissed...

Pull motor out again, insides frozen, sun low on the horizon... Replace floating injector (I had a spare since the one from when the motor exploded was fine). It had damn better work now...

Open N2O tank... Start filling... 30 seconds later no plume. Out of liquid Switch out tank. Start filling... Nice plume... Push button... Get a little hiss. Start praying to the rocket gods that it works... Little smoke... There is hope... More smoke! Clouds and clouds of it! Why won't it leave the pad? Oh god, you are NOT going to blow up on me... BZZZZZzzzzzz Liftoff! Yes! It worked! Hurray!

Unfortunately I didn't get much telemetry data, but the altimeter did tell me that it went 4738ft AGL. And I know that the timer was set to fire too early (I had it set for 20 seconds, but I am pretty sure that it went off when the rocket was still on its way up) and I only filled the motor at 700psi instead of the 900psi max.

Oh well....

If I get any interest I will update the post with the pics/telemetry data/videos. Heck, I would be happy to write a nice long thread about the rockets if anyone in interested...

Somewhat ironically I typed this post up while watching Titanic
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Sat Nov 25 2006, 05:38AM
Registered Member #63
Joined: Thu Feb 09 2006, 06:18AM
Posts: 1423
Yeek! I have enough trouble stomaching my own failed electronics, let alone hours and hours (or days or weeks) slaved into electronics AND rocketry for it ALL to then crumple.

Can we see the data from the GPS? :P
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Sat Nov 25 2006, 06:39AM
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2435
Just for you MattyB

It is in space deliminated format, importing into excel should give nice columns.

Sorry I didn't do it for you, I woke up at 6am and now is is 10:30pm after a day of launching rockets and I am getting a tab bit tired.

As to the whole seeing you work explode in front of you thing... It is just a part of the hobby ;) That rocket is getting old now (I got the original kit for my 13th bday, all that is left of it now is the motor retainer ). You see, the hobby is no fun if it works; you need to be alpha (or at least beta) testing something when you go out... It is worth if for that feeling right before you hit the button and the resulting BRRZZZZzzzzzz (that is actually what the hybrids sound like, they are unstable and have a sweet buzzing sound). The frosting of the cake is when it comes back down 10 seconds later and starts buzzing right before it makes that 8" crater
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Sat Nov 25 2006, 07:24AM
Registered Member #63
Joined: Thu Feb 09 2006, 06:18AM
Posts: 1423
ROFL (no offense) at Z-SPEED:

0.839347 <-- parachute presumably [supposed to] deploy here at apex?
-7.930543 <-- or here?
-25.961449 <-- Sh*t...?
-60.647758 <-- sh*t.. sh*t..
-75.275162 <-- sh*t sh*t sh*t.
-93.247856 <-- P*ss... **winces**
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Sat Nov 25 2006, 10:17PM
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2435
Pretty much

We only got the big(er) rocket on tape going up, so that wasn't all that eventful. Just a normal hybrid motor ignition.

The small(er) one was a bit more eventful at the takeoff, so here you go. It is in .wmv, hopefully you can all play it... If not pm me and I will find a way to get you a format you can play. They are 5mb a piece.
whole launch from me opening the N2O tank to when it goes out of sight.

the ignition sequence slowed down 4x and at a higher resolution

excell document with some graphs of speed and altitude

Some stills:

the 2 big rockets up against out truck and the yellow one on the pad

The GPS getting satelites and inside the nose cone of the yellow rocket.

The laptop doing the data logging and the reciever (don't want any sand in there)

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Steve Conner
Sun Nov 26 2006, 03:26PM
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Excellent thread ...! You're obviously crazy about rocketry, and other members seem to like it too, so why not change the thread title to "Model Rockets and GPS Tracking" and we can discuss the rockets as well as the GPS dongle. Or if you'd rather, I guess I can move the rocketry part to the explosives forum.

... wrote ...

sorry to hear the dongle got wrecked btw
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Sun Nov 26 2006, 07:26PM
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2435
Ok then, here we go...

A short history
I have been launching rockets with my family as long as I can remember (probably since '95 when I was 5 years old) and my dad had launched his share of them when he was a kid. Slowly the rockets got bigger/more expensive. First it was making them 2 stage, then 3 stages, then we started to go to bigger motors. First it was E's, then G's, now I am almost up to a K, but I would need a new certification to buy them. (if you are not familiar with the way these motors are classified, an B motor has 2x the total energy of an A motor, a C motor has 2x the energy of a B motor, etc. A G motor has about 100newton/seconds --or 25lb/s or 10kg/s-- of thrust).

There were 2 problems with the 'conventional' motors either made out of pressed black powder-BP (from 1/2A to an E) or ammonium perchlorate + rubber composite-APCP (from D to the solid boosters on the space ship). The first was that APCP is really expensive; like $100/kg. The second is that the ATF has (as of October 10) made it illegal to buy/transport any motor with >62.5 or propellant, unless you get a LEUP (like $100 a year, and you give up your 4th amendment rights, and you need to have a huge property to observe the proper distances). So most people had 2 choices, get out of HPR, or to not use explosives. Choice 1 isn't really a choice, so everyone had to find a way to not use explosives.

Luckily we were mid-adopters of 'hybrid motors'. Instead of simply burning a block of APCP or BP, it uses PVC as the fuel (lets see you regulate that ATF). But if you just light PVC on fire out in the open it burns kinda slow, not really great for making a rocket motor out of. So we needed to find a way to get an oxidiser in the chamber. What better oxidiser to use than pure O2? But it is hard to store pure O2 (we want about as much O2 as we need PVC). So we decided to use N2O (the same nitrous oxide used for racing cars). It was perfect; it dissociated into N2/O2 when in the intense heat of the combustion chamber, had a vapor pressure of 1,000psi so we didn't need a pump to get it in the combustion chamber, isn't a regulated substance, and is reasonably cheap (like $5 a lb).
note-- by 'we' I am referring to a large group of people that I was not really involved in. Just bought their working motor.

So that is where I am now.

I have 2 main rockets that I have been working on.

There is mine, who (as previously mentioned) was bought at the ROC launch on my 13th birthday. It was a Public Missiles (.com) Amram 4 (4 being the diameter of the rocket in inches) and as the name implies it was a scale version of an Amram missile.
At first this ran off a small I motor, but then we upgraded to a CPR based parachute deployment system. Instead of relying on the motor to give a blast to force out the parachute it has a small PIC based controller that uses a little altimeter to detect the apogee (apex) of the flight to eject a small (12") parachute, and then at 800ft AGL it fires a large (50") parachute. This prevents the rocket from drifting too far away from where you launched it. Then we upgraded to a large I motor, and then to a large J motor (we used the 54-1280 case because you could also use it as a part of a hybrid motor, however the company making the conversion kit stopped selling them). This got us to ~5800ftAGL. But it was expensive, $100 a launch.
That is where the hybrid came in.
At first we tried to use a West Coast Hybrids J motor, but it exploded on us. So we went out and bought a Hypertek, which worked flawlessly. And it worked flawlessly for many flights, until last Friday (11/24/06) when it didn't eject any parachutes and came down pretty hard.
In case you were wondering; it got the name Crazed because when we painted it (after adding the CPR) we put down a layer of white paint, then yellow fluorescent paint. This gave a very neat effect (you can see it if you look at the full size pics of the yellow rocket). It later got the nave Crazed II when the bottom exploded (see above link) and it was rebuilt.
I am thinking that crazed III will be made out of 2" tube and be lacking the canard fins. Just a 2" by 6' long yellow cylinder with a 1000n/s motor in it.

But since that rocket 'just worked' we needed a new one. So for Christmas my little bro (the one you see standing behind the green rocket in the videos 2 posts above this) got some tube and fins and whatnot, and I designed him a rocket. Then him/our dad built the airframe, and I hacked together a CPR wanabe parachute deployment system. Unfortunately it didn't work worth a crap, and after crushing a few feet of tube (that rocket was light enough that coming down ballistic only put a dent in it) I decided it was time for a complete redesign. And my new one works perfectly

So after getting the airframe working correctly, it was time to test out the WCH motor, and that is described in detail in an earlier post. Not quite perfect, but better than exploding

I will try to add some pictures after someone else posts. I try to keep my posts <10mb to keep Chris happy

BTW, in case you didn't find all of my videos in the thread, I have linked the folowing thunbnails to them:

Crazed I exploding, and then working. Then the fast/slow versions of the green rocket
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Mon Nov 27 2006, 10:05PM
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
I agree with steve, great stuff!

Too bad i'm such an aircraft-newbie like this!

I've read the archived thread and it sounded very interesting.ž
Regarding your buck converter, you can often find some nice (and small) converter chips on old motherboards, P1 and P2 like (new ones use large mosfets and multi-phase controllers for almost anything).
Anyways you shouldn't be getting that much voltage drop with such regulator.
If I get it, now you are using a 3V lithium battery as a power source?
Glad it works now.

Good videos also; You look big for a 16y old , from that I would think you are 20+
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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....
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Sat Dec 02 2006, 03:55AM
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2435
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.
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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.
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Sat Dec 02 2006, 06:04AM
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2435
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.
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Mon Sep 10 2007, 05:02AM
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2435

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.


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
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Thu Apr 10 2008, 05:40AM
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2435
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:

Accelerometer data:

(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...
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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?
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Thu Apr 10 2008, 07:43PM
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2435

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...
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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 µController 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!
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Fri Apr 11 2008, 05:59PM
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2435
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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