...this seemed like the best section, as under pyrotechnics it says "other non explosives"... maybe low explosives is better? well, you all can move it if you think so.

anyway...

My friends and I are looking into entering a rocketry competition representing our school.

Here is the web site for it:

<a href="http://www.rocketcontest.org" target="_blank">www.rocketcontest.org</a>

There you will find rules, guidelines, etc.

We are entering it with the intent to win. There is a lot of prize money involved, and we plan on giving it 100%.

Here is a synopsis of the competition: Construct a two stage rocket to travel as close to 1500 feet into the air as possible, while safely transporting two eggs.

Here is what we will be provided with...

</font><blockquote><font size="1" face="Verdana, Arial, Helvetica">quote:</font><hr /><font size="2" face="Verdana, Arial, Helvetica">Your team gets over $160 worth of products required to design, build, and fly your rocket for this contest: a 30-page Team America Handbook; a 350-page comprehensive book on sport rocketry called the Handbook of Model Rocketry; a CD-ROM containing a sophisticated computer program called RockSim for doing rocket design; a miniature electronic altimeter (altitude-measuring device) with its batteries; and a copy of Sport Rocketry magazine, the largest periodical published on the hobby.</font><hr /></blockquote><font size="2" face="Verdana, Arial, Helvetica">There are many limitations, too many to mention.

If we do end up signing up (almost certain), then I will be sure to be discussing it a lot on this forum (only in this thread, that is).

So, before any discussion about the actual construction of the rocket begins... I have a few questions...

How hard do you all think this will be? I know it will be a good bit of work, but how difficult would it be to expect a flight altitude of within 50 feet, as well as safely transported eggs, every time?

Aside from the entry fee ($160), how much money do you think this might cost us to do? That is including materials for construction and much testing, etc. This might be a difficult question to ask... but I was just wondering what you all might guess this might cost. Do you think we could do it for $100-200, not including entry fee?

...

Also, if you read some on the page you will notice that there is a lot of prize money available. If my teame wins (or is top 5), I will most definitely share some of the winnings with the forum. This may help justifiy a topic that is semi-off topic. :)

So, what do you all think?

You'll be hard pressed to win with a 200 dollar budget. Nice idea though, I'd say go ahead and do it, regardless of whether you win or not. It'd be a fun exercise. Id say, to get it within 50 ft is very possible, its all in how you plan. Say you had a computer onboard that triggered a parachute to come out substantially before apogee, say at 1475 ft. then you would almost certainly get incredibly close. Maybe this would be out of your scope (as it would be of mine) Other than that, 1500 ft really isnt that high, and wouldnt require too much propellant to get it up there. Maybe around a G class engine. Noltair might have some good ideas for you, pretty sure he knows some stuff about rockets(i saw a post of his on a rocketry forum)

<small>[ September 30, 2002, 10:36 PM: Message edited by: firebreether ]</small>

I hate this sort of contest. The reason I hate it is becuase you dont actually built a rocket. For me the engine is the rocket and everything else can go to hell. In this sort of contest you buy your NAD certified engines, you buy the NAD certified plastic case, you buy the NAD certified altimeter, you buy the NAD certified parashute and you tie it all together with your NAD certified shock cord, you put the eggs in polystyrene (NAD certified ofcourse) you cover everything with a layer of paper mache and write 'My rocket' on it and when it fires you have exactly the same chance of winning as every other gibbering idiot thats turned up with 160 dollers and a heartbeat.

The program will give you a rough idea where 1500 feet will be but the exact angle of the rocket, wind direction turbulence, actual motor performance and if your eggs survive the landing turn it into little more than a lottery. Ok, I'm being too harsh, engineering makes some difference but its everything I hate about this sort of rocketry, particulaly as its the only way it could be done. If people turned up with *real* homemade rockets, people would be injured. Enter it if you want, enjoy the trip, dont expect any real design to have any effect on your chances of winning.

In an attempt to rescue my post from being something other than whining I tried to find some data on high performance solid fuels. The results were dissapointing, with every page either conflicting with every other page, or being word for word carbon copies of eachother. Values of specific impulse for blackpowder (Its not high performance, but it is often quoted) has been between 50 and 150 secs. Anyone have some reliable values?

Theres a file on the FTP called "Composite Rocket Fuels" which I recommend you having a look at.

Here is a composition from that file:

</font><blockquote><font size="1" face="Verdana, Arial, Helvetica">quote:</font><hr /><font size="2" face="Verdana, Arial, Helvetica"> A very powerful mixture, Isp=250 :
Ammonium Perchlorate 75%
Powdered Aluminum 10%
PVC in THF 15%
All the ingredients should be dampened with THF (tetrahydrofuran) before
mixing. Do this in an area with very good ventilation and wear rubber gloves
to keep from contacting the THF with bare skin. This mixture is best used in
a perforated grain to help the solvent evaporate.</font><hr /></blockquote><font size="2" face="Verdana, Arial, Helvetica">You should also look at the rocket propellants section of the PFP (I think that the PFP has been taken off the web or something but you can download a copy from <a href="http://www.connect.to/juice" target="_blank">http://www.connect.to/juice</a>) as that has some interesting propellants including those used by NASA.

Hard boil the eggs :D

<small>[ September 30, 2002, 11:18 PM: Message edited by: xyz ]</small>

Marvin wins the Rant-o-the-day contest! :p

But seriously, he is quite right. I'm just getting into rocketry myself, and will be building my own engines and everything else.

Getting an altimiter that will trigger the parachute at the proper altitude is definetly a very good idea (who knows if its banned in the rules...I didn't read em). If you can't use one, you'll probably need a bigger budget for the engines needed for testing. (what engines do these use anyway? a specific aerotech or something? or can you choose?)

You'll also need lots of money for eggs. :D

If you NEED to get 1500ft, build an engine that will easily take it up to 2000ft. A bit of wind or other weather effects can seriously degrade performance. If you can get acces to it, I would go for ammoniumperchlorate fuels.

"You may not, however, build the rocket motor; your rocket must be powered only by commercially-made model rocket motors (G power level and below) that are listed on the NAR Engine Certification List."

Shit. The whole fucking contest comes down to sheer aerodynamics and lightweight construction. Is that rocketry, not even making your own engine? Hell, a rocket is essentially nothing more than a flying engine! What a pussies!

Coming from personal experience, try to build a rocket that will first go 250ft (probably a single stage to begin with). Once completed move on to make one that goes 500ft.. then 1000ft then 2000ft. Vulture is right about making a rocket that is engineered to go quite a bit higher than the minimum hieght, because as a rule of thumb, on competition day, whatever can go wrong, will go wrong. And I don't know how much expierence you have with rocketry, but it is something that really does take practice to make a well functioning rocket. And the cost of the project will depend both on how much you are paying for you supplies and how many tests you perform before you are satisfied.

Also your landing will be just as important as the flight itself, because you could go 10000 feet, but if you crack your eggs, then your out. I would advise that along with a good parachute system, to also have LOTS of foam in your payload (something like the stuff inside of sofas would work nice).

<small>[ October 01, 2002, 01:30 PM: Message edited by: NoltaiR ]</small>

Oh yeah, and why settle for such a small scale competition.. here are some REAL competitions:
rocketry.org

Bowery Award for Amateur Rocketry (details)
I hereby, and until notice to the contrary, endow the Bowery Award for Amateur Rocketry with $1000 going to the next amateurs launching a vehicle to a height in excess of 200 kilometers, to be disbursed at my sole discretion.

Stark Draper Open Source Rocketry Award (details)
I hereby, and until notice to the contrary, endow the Stark Draper Open Source Rocketry Award. This prize will consist of 3 ounces of gold or the monetary equivalent going to the next amateur team launching a vehicle to a height in excess of 200 kilometers, which in my opinion qualifies as an open source entry. These funds will be disbursed at my sole discretion.. (More details on web page)
X Prize Foundation (details)

On May 18, 1996 the X Prize competition was announced in St. Louis. A prize of $10 million is being offered to the first amateur (non-professional) group to successfully launch and recover a reusable craft to an altitude of 100 kilometers (62 miles) twice in a 14 day period. The vehicle must carry one pilot, but must be built to carry 3 adults weighing 198 pounds each.

when i was at school the science classes had a rocket competition, the sole aim was to go as high as you possibly could, with out cracking an egg. and there was an added bonus if you could land it within X number of meters from where you launched(forget the exact distance...this was about 6 years ago)

i never got to enter, because as per usual i was suspended when they ran it. however i did sneak down to school to watch(fuck i'm gay i acctually snuck into school :D ).
was pretty pathetic, most of the younger kids from years 8 and 9, formed groups and pooled there money together to buy several D size estes motors, then fired them all at the one time.
a few people from year 12 acctually made KN/Su motors.

i'd say it would worth entering the competition, just for the hell of it. you never know where things might lead. you may end up finding out about other, more fun, competitions.

Even though we are fairly limited in what we can do to make the rocket, I am very inexperienced in rocketry, and this will be a good introduction regardless.

One more thing, I think some of you didn't quite get the bit about wanting to go as close to 1500 ft as possible. What that means is to go EXACTLY 1500 ft, not over OR under. If you fire it 50,000 ft.... you are no better than if you had fired it 10 feet.

Now, I will probbaly be posting again in this threadwhenever I have more details about our plans, our materials, and so forth. Thanks for the input thus far!

Well I have a fair bit of experience with rocketry and know that there are several items you do not need to worry about.
The first item is electrical ignition I just used a pair of wires and a lantern battery to launch rockets.

The main problem with the rocket design is the weight distrbution. The two main components that will take up the most weight will be the eggs and the engines. I would try to distribute the weight thought out the main body of the rocket so that it is fairly balanced, it will be impossible to have the rocket perfectly balanced.

The recovery system should be designed so that it takes the payload down fairly quickly because the longer it is in the air the more likely it is to drift away and do undesirable things. You probaly will have to use a parachute recovery system. Gliding recovery systems would be very difficult for a payload the size and weight of an egg and a tumble system, while fairly easy to achieve is too risky (unless you like scrambled eggs :p ).

The launch will be one of the most tricky stages, as that is when you will have to use the most thrust, and because the payload will be under the most G's. Remember to rocket will have to overcome the force of gavity before it even leaves the launch pad.

Overall. Design the rocket to fit around the eggs . Incorperate their weight, size and fagileness into the design.

Although I have a lot of experience with homemade rockets.. I don't have a lot of experience with making them work (out of the 30 or so that I have ever tried to make.. only about 3 or 4 made it over 500 feet and about 10 that made it over 100 feet). But I can certainly tell you that my biggest problems were keeping the fuel burn steady, not too fast, not too slow; also even more than that, it is a bitch to make a good homemade nozzle because just the slightest error in size of hole or strength can leave you with nothing more than a low flying arial shell.

Since I am a rather experienced rocketist, I can assure you that 1500 ft is not high at all. With your budget, the best idea would be to buy a commerical kit, put a commercial engine in it, and let it rip. You will need a bit more than 200$US though.

As for getting to exactly 1500 ft, you have two options: precise calculations (and experiments) to correctly design your rocket to reach the designated altitude (you can add drag elements later if you're too high) or deployment of a dragging element (such as a parachute) on the way up to stop the rocket at the right altitude (Firebreether's idea...). The second idea will yield better results, but with more work. However, if you chose the first idea, you won't really have a lot of work to do (and your success is dependent on the weather), i.e. it's not an incredible challenge...

Anyway, if you don't know anything about rocketry, I advise you to check out your local Tripoli or NAR section for info. These guys can help you. Also, they will teach you basic safety precautions.

In my case, I prefer experimental rocketry (building everything from scratch). There's no feeling like lighting a home made engine on the test bench!

2 things....

1) I dont have to make the engine/fuel, and I don't THINK i have to make the nozzle, however I am not certain of that.

2) I cant use a kit. That isn't "making" a rocket.

In what direction will the egg need to most padding? Like, which direction will it be forced the most? I am guessing down, which means we will want to include extra precautions in that respect.

We are still in the VERY early stages, as we have yet to get very organized, or sign up, or anything.

I checked the rules of your contest (rapidly though).

Indeed, you do not have to design any part of the engine. However, the rocket has to have 2 stages (that's a bit more challenging). Also, you cannot terminate the flight with a parachute or other design. So that you are left with the first option. Still, it is not impossible with a tight budget, even if you have to make all the rocket. Indeed, most kits are just carboard and plastic or balsa fins anyways. Easy to make...

There was a similar competition on "Junkyard Wars". If I remember correctly, the team that won did not have that much problem with the egg (but then again, I could be wrong). In any case, that's the easiest part to design and test. Just make a shock absorbing case, add your egg and drop them from a certain height. Landing speed is easy to calculate. With a few trials, it will give you the maximum speed at which your rocket should land. That should set the parachute.

As for the design of the rocket, just iterate using the software (it probably already has all the NAR rocket motor thrust curves included). One last suggestion: KISS (Keep It Simple Stupid)...

Have the eggs upright in the rocket and not lying sideways as an egg needs about 20 times the force to break it if it is upright compared to if it is on it's side.
The egg will need the most padding toward the top of the egg if you use a parachute to stop the rocket at 1500ft then the deceleration will force the egg upward.
I would put the most padding on the top, a bit less on the bottom, and then the least (but still a lot) on the sides.

You could make a block of gelatin/epoxy/other material with the eggs set in the middle

Well, my novice rocketeer, I just thought I'd add my $2 worth (2 cents doesn't buy much anymore)

Consider parallel staging. If you can find some older books on rocketry, some may have info on parallel setups (think Space Shuttle).

I'm pretty much out of the rocketry scene, but my last (and untested) project was to build a linear-staged model, with non-detachable stages. Allow me to elaborate: traditional model rocket staging is done by ading booster stage engines complete with short body tubes and wider fins (to compensate for center of gravity shifted rearward). BUT consider, if the main (top) engine was mounted far forward in the body tube, the booster engines could be mounted behind, with just a loose friction fit. As long as they don't fall out before launch, the spent boosters will eject upon next-stage ignition. As for the larger fin area, consider that the eggs move your CG forward. Lotta guys I knew in HS used cotton balls to protect the egg. I dunno what they were using for engines. Also, is it permitted for you to build your own launch pad? If so, consider designing for a launch tube. With a closed breech, the exhaust gasses will give an extra boost. The suggestion of a gel block to protect the eggs sounds best.
-I never bothered with eggs. I went straight to impact-detonated warheads.-

Harry

I like the idea of winning the $10 million for civilian space travel. Better start testing, you only have till 2005!

[URL=http://www.cnn.com/2002/TECH/space/10/16/xprize.contest/index.html]

<small>[ October 25, 2002, 06:31 PM: Message edited by: Fukineh ]</small>

Iv been trying to work on a new rocket fuel. So far iv only use kno3 sugar but soon i will be buying some ammonium persulfate and seeing if thats any good. Ammonium persulfate has 8 oxygen compared to 3 in kno3 and with a simmiler density i think that maybe if the oxideiser reacts readyly enough that i could almose get twice the range. Its a little more toxic (ok a lot) and not much has been tested on it so i will need to havea look and its propities before building my rocket. Has anyone here ever tryed ammonium persulfate?

i have a bag of 250grams of Amoniumpersulfate, so i will try it, and post the static test results.

</font><blockquote><font size="1" face="Verdana, Arial, Helvetica">quote:</font><hr /><font size="2" face="Verdana, Arial, Helvetica"> persulfate has 8 oxygen compared to 3 in kno3</font><hr /></blockquote><font size="2" face="Verdana, Arial, Helvetica">It's not because it has more oxygen atoms that it is a more powerful oxidizer! That's a very wrong assumption you are making here.
Persulfates can only liberate one oxygen atom per molecule and that's one of the oxygen atoms that connects the 2 sulfur atoms by a peroxide bond. The 7 oxygen other atoms are strongly bonded to the sulfur and have nearly zero oxidizing powers, except at very high temperatures.

(NH₄)₂S₂O₈ -&gt; (NH₄)₂S₂O₇ + [O]

The other reaction product, ammonium disulfate, is a solid and doesn't decompose into gas unlike other ammoniumsalts IIRC.

Persulfate does have a higher oxidizing potential than KNO₃, but that has only an effect on chemical reactivity.

BTW, please type chemical formulas correctly.

<small>[ October 27, 2002, 09:41 AM: Message edited by: vulture ]</small>

I have some great experiance with this type of (model) rocketry. I have made a 2 stage egg lofter. It is actually rather easy. In the kit you mentioned the Hand Book of Model Rocketry. In that book I believe it has a complete chapter on makeing egglofters and its properties. Getting the altitude is fairly simple. I use a combination of model rocket software and simple trial and error to achieve it to great success. The rocket itself can easily be made with under $50 in supplies. I have made many 2 stage rockets, usually spending only $15 to $20. And one last thing, please make sure you get the CP & CG (center of pressure/gravity) correct and use some software to validate that. I have seen several egglofters with negative or neutral stability go up flip over and drive into the ground - one of mine actually did that but believe it or not the egg survived (it was wrapped with foam - ihave found this to work better that bubble wrap.

Go to my website and click on the rocket section and the links for some good info. <a href="http://www.ghostcustom24.50megs.com" target="_blank">Ghostcustom24</a>

If anyone wants to play with a more energetic, yet simple, propellant try this
15-25% Magnesium powder
10 - 30% HTPB (hydroxyl terminated polybutadiene - a two part rubber)
remainder is Ammonium Nitrate.

Messing about with the proportions is a good way to modify specific impulse, burn rate, burn temperature, and burn rate coefficient eg
25% Mg, 12%HTPB 63% AN gives (at 1000 psi) Isp of 250, flame temp 4800F
15%Mg 20%HTPB 65% AN gives (at 1000psi) Isp of 220, flame temp of 3100F

You could use a KClO4/sucrose mix for a traditional rocket.
Or, since it doesn't make much of a difference, you could make it a stylish whistle-type rocket with 67% potassium perchlorate, 29% sodium benzoate, 1% iron oxide, 3% petroleum jelly.

This may all be very nice information, but if you read the rules you may notice that only commercial engines are allowed (pathetic).
So winning will come down on figuring out the right aerodynamics.
This means it's purely a physics contest.

Ahhh... that's unfortunate. :( The site's down at the moment. ONLY allowed to use commercial engines? What's the point of calling it a contest?

Because comming up with the correct calculations is more of a challenge thana 'brute force' comepetion. Anyone can get ahold/make powerful rocketfuels, but it actualy takes some thought/ testing to come up with calculations such as are going to be needed to win.