Physics xtra credit project: Build two 1-time-use candyrocks

[Zippiot]

The professor has taken a great interest in this project and just changed their mind on the requirements. Instead of building a single rocket and doing all the calculatios on it, she wishes for me to build 2 rockets with different sized and shaped motors with the same amount of propellant.

A simple cored inhibited grain will be used, 225 grams of propellant each. One will be long and slender the other short and stubby. Supposed to build 2 near identical rockets and compare results. But before launch I need to do static tests and estimate which will go higher and which will be faster. My concern so far is that the different weight distributions will affect rocket performance...

Still gotta do many calc's but I no longer need to do Pressure and a few others.

About how big is a 225 gram motor using 60/40 kno3/sugar?
Gotta find a new place to launch or is it under H sized motor (max the current locations allows)

[jthompso]

Richard Nakka's B-200 motor was designed for a 225 gram KN-Sucrose grain--this put his motor in the H class so potentially you could be dealing with a pretty powerful motor. Here's the link to his information:

http://members.aol.com/ricnakk/engine1.html

[Zippiot]

Reading through his article he used the 65/35 ratio...anyone think my 60/40 would bring it below H class?

If not I'll ask to use a smaller batch size

[Ray]

ISP will be down a bit for a 60/40 mix (fuel rich). Even if you assume an ISP of 100 you are in "H" class impulse.

Anything over 125g of propellant or 1500g liftoff weight needs a full waiver from the FAA.

[heada]

If flying in California, you also need a pyro license.

A blurb from another forum that I'm a member of:

"This is for all California residents that purchase, transport, store or launch high power rockets. If you’re going to “Purchase, transport, store or launch high power rocketsâ€

[Zippiot]

So max 125 gram propellant, keep it legal[ish] and upon looking closely at nakka's b-200 motor...I cant imagine how big of a batch I would need to make. Most I ever made before was a dixie cup full, and that was eceedingly large.

I sent her an email asking to bring the propellant down to 125grams, I hope you guys dont mind if I quote you on that topic.

[Anders Troberg]

It would be interesting to see a comparison between a normal nozzle and an aerospike nozzle. Perhaps that's a twist you could sell to the professor?

[heada]

So max 125 gram propellant, keep it legal[ish] and upon looking closely at nakka's b-200 motor...I cant imagine how big of a batch I would need to make. Most I ever made before was a dixie cup full, and that was eceedingly large.

I sent her an email asking to bring the propellant down to 125grams, I hope you guys dont mind if I quote you on that topic.

The FAA will allow a flight using up to 125g of propellant without a FAA waiver. The ATF requires that all propellant be 62.5g or less unless you hold a LEUP. You will notice that almost all manufactured G motors have less than 62.5G of propellant (2 exceptions come to mind and they require a LEUP to own/use). The FAA limit being 125g allows for a cluster of 2 G motors (each having no more than 62.5g)

If you'd like, I can provide links to the FAA and ATF regs.

-Aaron

[Ray]

You will notice that almost all manufactured G motors have less than 62.5G of propellant (2 exceptions come to mind and they require a LEUP to own/use).

Not true. ATF requires a LEUP for APCP propellants over 62.5 grams. Sugar motors, Hybrid motors, BP motors do not fall under this rule. I'm not sure, but ANCP motors aren't subject to it either.

The FAA requires notification for any rocket weighing over 1 lb lift off weight but under 1500g or 4 oz of propellant but under 125 grams propellant. For rockets over those limits, you'll need a full waiver. Don't ask me why they mix standards in the regs, but that's how they are written... You need to notify the nearest airport and let them know you'll be flying. They'll want to know where, how many flights, how high you expect to fly, the hours you'll be flying the rocket and a description of the rockets to be flown. They may have some other questions for you along the way...this is a notification of flight, not asking permission. Be polite but firm. Be smart too, don't try to fly at the end of a runway or near an airport.

Federal Aviation Regulations 101 (FAR 101) is the part of the code you need to comply with. Google it, read it, understand it.

[heada]

If you ask the ATF they will tell you that APCP, ANCP and KNCP based rocket motors are under their regulations. BP motors that contain more than 62.5g of propellant would be under this rule as well.

http://www.atf.gov/explarson/0504rocketryqa.pdf question #1 (any rocket motor containing more than 62.5g of propellant) question #8 (any motors of AN or KN is considered an explosive) question #2 is interesting, and may be a loophole if constructed correctly. If you make the motor yourself and use it at the same site that you make it at (no transport allowed) then you are not required to get a LEUP but you are still required to store it in a type4 magazine.

While hybrids (NO2 + fuel) do not currently require an LEUP, I would not be surprised if they are next on the list.

If you question this, please feel free to contact the ATF:

Explosives Industry Programs Branch
650 Massachusetts Avenue, NW.
Washington, DC 20226
Phone: 202-927-2310
Fax: 202-927-8887

Here is a direct contact that others have dealt with on this issue:

Richard E. Lake
Industry Operations Investigator
Bureau of Alcohol, Tobacco, Firearms & Explosives
2707 N. 108th Street, Suite 202
Omaha, NE 68164
(402) 952-2635 Main
(402) 952-2638 Direct
(402) 952-2606 Fax

As far as the FAA regs, you quote them all correctly, with one addition. With a NOTAM (Notice to Airmen) that is filed with a notification only (more than 1 lb less than 3.3 lbs) you can not fly within 5 miles of an airport. Waivers (granted by the FAA) can allow you to fly within the 5 mile limit.

-Aaron

[Zippiot]

I have a LEUP, got it a few months ago when I tried composite motors.
I am seeing different regulations on every search I do...The most consistant is a rocket under 125 grams propellant that weighs under 3.3 pounds is not considered to be high powered and can be launched and transported without an FAA waiver.

3.3 pounds seems huge to me, so does a F class motor even though I shot off a few of those using composite aerotech reloads. So if these sites are correct my luep and a rocket with less than 125grams propellant that also weighs less than 3.3 pounds should be fine.

You sure KN is the explosive and not KP? I didn't see you write anything about Potassium Perchlorate, whose isp can be as high as 200. Much stronger than KNO3 and propellants using KP (or is it PP) are considered composites too.

[heada]

Please, don't take my word on the ATF regs. I will read them in the light that I would like them read. I highly suggest you call your local ATF agent and ask them directly. Since you already have a LEUP, almost all the questions about making and flying your own motors are moot.

3.3 pounds seems big, until you get into big rockets. This fall I launched a 29.5 pound rocket to 3500 feet using a K600 motor. I have in the past launched a rocket that went 6000 feet, 810mph and pulled 48Gs (it was less than 2 pounds, but on an I435 motor) There are other people that make my rockets look tiny.

-Aaron

[Zippiot]

What is the key to making a rocket fast? I see many rockets with the same class motor, just some go 300 mph and some go 600...


I am reading through the sites you linked and I'll post back later if I'm set to go.

[Zippiot]

Just got a reply from the professor, she said It's fine for me to build whatever is safe/legal. I replied asking about the aerospike, I really want to try to build one but I still need a little image of how the spike is secured...

She wants it to be a comparison of sorts, using the same propellant compare motor shapes on rocket performance. I might be able to switch it to an aerospike to convergent-divergent compairson but my limited knowledge of aerospikes would prolly make the test unballanced. I would assume that the conv/divr would for sure win b/c I dont know what angles exactly to make the aerospike.

Well I may try the aerospike, just for kicks but I gotta finish the regular motors first.

[heada]

If you are looking for pure speed, look for a fast burning motor that creates high amounts of thrust (AeroTech Warp9 or CTI V-Maxx) Put this into as light a rocket as you can that is minimum diameter. Basically, optimize the rocket for less drag while keeping the rocket as light as possible with as much kick in the motor as possible. The LOC/Pricision Weasel is a good rocket that will go fast on 29mm motors.

High speed does not always mean high altitude. If you want altitude, you have to find not only a very light/low drag rocket but also find an optimal mass for that rocket and optimal burn time.

-Aaron