How to build a solid-fuel rocket

[harry14]

Hello, I have to build a science project, and since I'm interested in aeronatuics I thought why not build a rocket? Problem is I've no idea about their working, I'm trying to research on them and searching for websites which will give me an idea of how they work. If you can please enlighten me with a few links, please do so, also I would like to know what's some differences between solid-fuel rockets and solid motor propulsion rockets as offered by science buddies, do the latter work using a motor as a propellant?
I would also like to know what things I can use as fuel for my rocket, thanks.

[deleted-93346]

This is an exciting area to work in. Check out our web page for ideas:
http://tinyurl.com/7jetsps
Also take a look at:
http://www.estesrockets.com/
to see some info on rocket kits and parts.

ROCKETS CAN BE DANGEROUS !!

You will absolutely need adult supervision while working with the solid fuel rocket engines (motors) and when firing rockets. You will need to check local laws concerning rocket launching: contact your fire or police departments for advice about where and when it is permitted to launch rockets, In many parts of the country fire season has started and rocket launches may be strictly prohibited -- check this early before investing time and effort building a rocket that you won't be able to launch!

I'm ill this morning, but I've contacted our experts coordinator for help, so watch the board for more detailed help later today or tomorrow. Best of luck.

[harry14]

Yeah I have adult supervision with me, I'll take all precautions possible. I saw the estes link, the thing is I don't want to order the fuel or the casings, I want to make them myself, I want to build the whole rocket myself, then only will I understand its working and dynamics properly.
I wanted to ask some questions for my rocket-building :
1.How does weight, thrust, drag and lift affect the flight of the rocket?
2.What fuel component can be best made and used for the rocket, the old gunpowder mod of saltpeter and sucrose? Ammonia based fuels? Or something else?
3.How do I decide the dimensions and shape/size of the different parts?
4.How do I attach the parachute to the rocket and make it work when the fuel burns out?
5.Also I was curious to know if I could use Rust in a small amount as a burn rate catalyst? Would it work?

[rmarz]

harry14 - DO NO TRY TO BUILD A SOLID PROPELLANT MOTOR YOURSELF, UNDER ANY CIRCUMSTANCES. Although you have done some research about some of these materials, the materials you describe are not stable and do not exhibit controlled burn rates when in a confined environment. Black powder, gun-cotton and other materials will burn slowly, for several seconds, in an open atmosphere, but once the burning starts in a near closed environment, the rate of burn will accelerate and become a millisecond or two. This is what makes a rifle bullet achieve velocities of several thousand feet per second, and cartridge pressures of many 10's of thousands of pounds per square inch. As for adding iron oxide as an inert material to slow the burn rate, you don't have enough eyes or limbs to get through the experimentation successfully. Sorry for the rant, but it really is for your own safety. Use the Estes or other reputable hobby motor for your experiment. There is a lot to learn from all the other aspects of the experiment.

Weight, thrust, drag and lift are the 4 components for flight. They are the vectors for winged flight (when the opposing values are equal, weight = lift and thrust = drag, you have what is referred to as an airplane in unaccelerated level flight. The airplane is in perfect equilibrium. In a rocket, the same factors apply. When normal (perpendicular to the earth's surface) thrust exactly equals the force of gravity, the rocket will be suspended in mid air. When normal thrust starts to exceed gravity, you will start vertical acceleration. In a perfectly vertical ascent, only thrust and weight (gravity) are at work. As soon as the trajectory is anything but perfectly vertical, the other force vectors of drag and lift enter the equation.

There are many sources that can answer your questions about parachute deployment and the design and control issues for your rocket. Good luck, be safe, use a commercially built motor with good supervision.

Rick Marz

[harry14]

Alright if you say so, I won't build the motor propellant by myself, I'll have to order one then, so can you suggest a good rocket motor available online? (from Estes/hobbyists)
Thanks for the information, so basically can I make a body out of a paper sheet dowel, roll it, use white glue, make the fins of the nozzle out of cardboard? Would the cardboard/paper dowel body burn at launch or mid-flight?
Also how can I know how the dimensions of the body/nose/nozzle will affect the flight of the rocket and how can I optimize the working of the parts?
I mean ofcourse weight of the rocket with the fuel can be known, but how do I calculate out the thrust and lift my rocket gets? Or to what altitude my rocket goes? What ways are there to calculate those things?

[rmarz]

harry14 - I haven't built a solid propellant vehicle in over 50 years (yes, they had them back then), so I don't really know the current availability of the commercial motors. John posted a few sites in his response, and I'm sure there are many others if you do a search on amateur rocketry on the web. There are probably many plans and safety guidelines as well. If you research many of these topics you will gain a much better understanding of the details. Perhaps a visit to a local hobby store that sells these motors (and possibly rocket kits) will help you gain more insight.

Knowing the weight of the assembled rocket and motor, and using the motors published specifications of thrust and burn times, will give you some beginning information as to the acceleration potential and time-of-flight. But, this is an experiment, so many more variables will be involved.

Rick Marz

[theborg]

I understand and am impressed with your desire to design every aspect of the rocket. However, as mentioned, this can be quite dangerous. Significant design, testing and quality control goes into the commercial rocket motors. There are a significant number of variables, like fuel/oxidizer mix uniformity, that if not properly accounted for can result in catestrophic failure. I suggest you research the principles of rocketry. This link is a good resource to get you started.

http://www.nasa.gov/audience/foreducato ... ckets.html

Along with explanations to several of your questions, the link to the additional resources has an explanation of how to use math to determine max flight height.

For motor performance, research the terms:
Thrust - the amount of force produced by a rocket motor
Specific impulse (Isp) - the efficiency quality of the fuel

For body design, research the terms:
Center of Gravity (CG) - point through which thrust acts
Center of Pressure (CP) - point through which drag acts
Your nose cone, body and fin design will affect these greatly and if they are not correctly accounted for will cause your rocket to be unstable in flight.

You can build rockets out of the materials you list, but I suggest one of the rocket kits sold at any hobby shop. They have ones that have all different component parts of a rocket, allowing you to design your own, but still with parts specifically made for the job. However, since it seems clear this is your first time dealing with this topic, I would suggest getting a small ready to build kit just to get a feel for all the different variables that go into rocketry.

This link provides tons of info on commercially available rocket kits and accessories, including motors:

http://www.estesrockets.com/rockets

One more note, many areas have restrictions and/or require permits to launch model rockets. You will need to check with your local city or county government.

Look forward to hearing how your experiment goes.

[harry14]

Thanks a lot, I know it's my first time, and I know I would be better off with a ready to build kit, but then how will that itch of making it yourself be satisfied?
Anyways even if I want to order a kit/motor that's going to be a problem, In US, people get their mini Estes motors around Rs.550, in India you get these at 1500, thanks to tax, almost 3 times the original price, makes it very hard to purchase a decent motor or a kit

[theborg]

Well, I certainly admire your independent, do-it-yourself, attitude. Let me say that the kits still satisfy the itch you speak of. The great thing about kits are that they provide all the appropriate parts, but rarely are snap together. You still have to put them together. The more advanced kits require you to do a fair amount of design work, and all the construction.

Now as for the cost, It helps to know you are in India, but I have no frame of reference to suggest where you might get the components we are talking about. Even if you want to build your rocket from scratch, I am still firm on the advice that you buy a commercially available rocket motor. However, the following link provides good instructions on how to make a rocket from scratch without a kit for those willing to work through a lot of trial and error.

http://www.jamesyawn.net/modelrocket/intro/index.html

[harry14]

Thanks a lot, the itch part was a little exaggerated, anyways I'll try to buy a motor if I can, but I think I'll manage building and testing through the kit built from scratch, I'll keep you posted on how the experiment goes.

[theborg]

Continue to post with further questions. As mentioned, the Center of Gravity and the Center of Pressure will be important to the stability of your rocket in flight. For an explanation, i've included the following linkes:

Center of Gravity (CG):
http://exploration.grc.nasa.gov/educati ... rktcg.html

Center of Pressure (CP):
http://exploration.grc.nasa.gov/educati ... rktcp.html

For a nice strait and stable flight, design your rocket so that the CG is above the mid-line, closer to the top of the rocket (This can be done by adding weight to the nose) and the CP is below the mid-line, closer to the back of the rocket (This can be done by adding more or larger fins to the back end). Basically, you want your rocket a bit top heavy. If these two points are to close together or are reversed your rocket will be unstable and tend to tumble end over end in flight.