O-Engine Altitude Questions for High School Rocket Club

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JackO

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Hey guys,

Apologies for asking such a basic question, but I'm tired of coming up empty with Google. Does anyone know a reliable way to calculate max altitude of a supersonic rocket? Alternatively, does anyone have a comprehensive chart of altitude records by engine type going through O/P engines?

Our rocketry club (all high school students with a few mentors) has received funding from the school to begin testing propellant for our 50,000 feet attempt. Our plan is to build a 30,000 NS case-bonded finocyl rocket engine using many of the same techniques as Derik Deville. We will static test this rocket and fully characterize the propellant beforehand. So my incredibly basic problem is whether or not this mid-O engine can take our rocket to 50,000 feet even if we designed it perfectly. Every rocket altitude calculator gives me a different answer and I'm having issues with rocksim's custom engine input, which I will be re-visiting soon.

To summarize, will a 30,000 NS rocket engine with a 6" diameter send a well-designed rocket to 50,000 feet?

I hate it when I see threads where inexperienced members ask for help without any detail or seeming effort put into their posts especially when this community offers such extensive advice, so I tried to be detailed.

Any and all help is appreciated.

-Jack
 
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BDB

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I suggest downloading the ThrustCurve app. It is the easiest way to do these kind of quick calculations.

But if you are serious about launching to 50,000 ft, you better rely on more than quick calculations. You need serious simulations: start with OpenRocket; it's free and easy to use.

Do your homework on this one. 50,000 ft is a lot more involved than you may think. That's my goal too. But I'm planning on taking several years to accomplish it.
 

JackO

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Hey BDB,

Absolutely, we don't take 50,000 feet lightly. I will download ThrustCurve, thanks for the suggestion.

To give some more info: We are budgeting a semester for static and avionic tests before our launch next year. Also we are using RockSim and BurnSim for detailed calculations, I just can't seem to load our custom engine into RockSim so am turning to simpler programs to quickly calculate the engine requirements for such an altitude.

-Jack
 

JackO

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Hey OverTheTop,

Perfect, thank you for that link. That is the proof-of-concept I've been looking for.

-Jack
 

NateLowrie

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Hey guys,

Apologies for asking such a basic question, but I'm tired of coming up empty with Google. Does anyone know a reliable way to calculate max altitude of a supersonic rocket? Alternatively, does anyone have a comprehensive chart of altitude records by engine type going through O/P engines?

Our rocketry club (all high school students with a few mentors) has received funding from the school to begin testing propellant for our 50,000 feet attempt. Our plan is to build a 30,000 NS case-bonded finocyl rocket engine using many of the same techniques as Derik Deville. We will static test this rocket and fully characterize the propellant beforehand. So my incredibly basic problem is whether or not this mid-O engine can take our rocket to 50,000 feet even if we designed it perfectly. Every rocket altitude calculator gives me a different answer and I'm having issues with rocksim's custom engine input, which I will be re-visiting soon.

To summarize, will a 30,000 NS rocket engine with a 6" diameter send a well-designed rocket to 50,000 feet?

I hate it when I see threads where inexperienced members ask for help without any detail or seeming effort put into their posts especially when this community offers such extensive advice, so I tried to be detailed.

Any and all help is appreciated.

-Jack
Tripoli records are a good place to start: https://tripoli-records.org/records/single.html

You should be able to build a single stage rocket using a 15,000 Ns motor to hit 50,000. With that impulse I do believe you're better off using a 4" airframe.

Note that you can do it with a 2 stage rocket with far less impulse.

My advice is to pay the $30 and get a copy of BurnSim. You play around with the engine configuration and export any configuration into a rocksim .ENG file you can import for your simulation. It will be your hardware's very best friend and likely save you a case or 2. If you hop over to the research forum we can give you some advice on the design.
 

JackO

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Hey Nate,
Thanks for that link. I have a trial version of burnSim currently (I'm cheap as hell) , as well as RockSim. I'm downloading the full version within the week (gotta get access to download anything on school computers). To be honest, that number comes as a surprise to me, it is much lower than I anticipated. I will talk to Derek Deville about it this week. We were going for the large diameter to better shape the finocyl core.

I would love love to be a part of the Research Section, but I cannot get certified as a minor. Being in that section would be ideal.

-Jack
 

blackbrandt

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Hey Nate,
Thanks for that link. I have a trial version of burnSim currently (I'm cheap as hell) , as well as RockSim. I'm downloading the full version within the week (gotta get access to download anything on school computers). To be honest, that number comes as a surprise to me, it is much lower than I anticipated. I will talk to Derek Deville about it this week. We were going for the large diameter to better shape the finocyl core.

I would love love to be a part of the Research Section, but I cannot get certified as a minor. Being in that section would be ideal.

-Jack
Hey jack! I'm a high school senior. Cool to hear that you guys are attempting this project. Just curious, what rocketry experience do you have?
 

NateLowrie

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Hey Nate,
Thanks for that link. I have a trial version of burnSim currently (I'm cheap as hell) , as well as RockSim. I'm downloading the full version within the week (gotta get access to download anything on school computers). To be honest, that number comes as a surprise to me, it is much lower than I anticipated. I will talk to Derek Deville about it this week. We were going for the large diameter to better shape the finocyl core.

Several people on this forum (Jim Jarvis and have gotten over 100,000 feet

I would love love to be a part of the Research Section, but I cannot get certified as a minor. Being in that section would be ideal.

-Jack
Jack,

It takes a lot less than you think. Several members on this forum like Jim Jarvis and Kip Douglas have done well over 100,000 feet on N to M two stage stacks that total less than 30,000. Kip's thread (https://www.rocketryforum.com/showt...ench-2-0-Two-Stage-100K-Build-Thread-and-More) is a good read. Jim has several threads. Evan Brown is attempting a 100,000 ft 2 stage project on just 10,000 Ns.

The finocyl should be more than doable with a 98mm core if you cast around an aluminum mandrel. FredA has some experience with that type of motor. You might PM him.
 

JackO

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Hey jack! I'm a high school senior. Cool to hear that you guys are attempting this project. Just curious, what rocketry experience do you have?
Hey Matt,
Thanks for asking, I'm only a sophomore in high school, but I'm dedicated leading this project. I've built a few I engines in the past and launched a minimum diameter 475 NS engine to ~8000 feet. There are a lot of smart people in our club, and I have learned a lot since that launch. I'm trying to learn more about the challenges of large engines through the two M engine tests we will perform to characterize the propellant. I'm also applying for aerospace internships this summer.

-Jack
 

JackO

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Jack,

It takes a lot less than you think. Several members on this forum like Jim Jarvis and Kip Douglas have done well over 100,000 feet on N to M two stage stacks that total less than 30,000. Kip's thread (https://www.rocketryforum.com/showt...ench-2-0-Two-Stage-100K-Build-Thread-and-More) is a good read. Jim has several threads. Evan Brown is attempting a 100,000 ft 2 stage project on just 10,000 Ns.

The finocyl should be more than doable with a 98mm core if you cast around an aluminum mandrel. FredA has some experience with that type of motor. You might PM him.
Awesome, thanks Nate! I look forward to checking out all of these threads after school tonight. I really am pretty surprised yet relived how over-powered our engine is. I thinks we will cut down the diameter to 5" and use the extra space for insulation.

We were planning on using a foam mandrel for convenience and cost, but I will PM FredA for sure I always appreciate additional contacts.

-Jack
 

new2hpr

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Rocksim doesn't do very well at all with altitude estimation when you're going above Mach, especially 3+, which you might see.

I don't think the altitude will be your issue, it will likely be construction methods to hold together at those speeds. Good luck, look forward to updates!
-Ken
 

rharshberger

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Rocksim doesn't do very well at all with altitude estimation when you're going above Mach, especially 3+, which you might see.

I don't think the altitude will be your issue, it will likely be construction methods to hold together at those speeds. Good luck, look forward to updates!
-Ken
I would recommend running your sim in OpenRocket, Rocksim, and RASAeroII (RA2 is free, but requires contacting the developer via his website, iirc here on TRF he is username"aerocfd".
 

JackO

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Rocksim doesn't do very well at all with altitude estimation when you're going above Mach, especially 3+, which you might see.

I don't think the altitude will be your issue, it will likely be construction methods to hold together at those speeds. Good luck, look forward to updates!
-Ken

Hey Ken,

Thanks for letting me know. I will do more research on RockSim and you're right we'll be hitting Mach 3. We'll be building everything out of aluminum and a steel-tip nosecone. Thanks! I'll make a build thread in the next few weeks.

In a related topic, would it be possible to braze the aluminum fins on (minimum diameter)? Students are not allowed to weld on campus, so we don't have any facilities for that.
Do you guys think brazing would be structurally sound?

-Jack
 

JackO

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I would recommend running your sim in OpenRocket, Rocksim, and RASAeroII (RA2 is free, but requires contacting the developer via his website, iirc here on TRF he is username"aerocfd".
Ok great, I'll check them out. Thanks Rich.

-Jack
 

Chuck Rogers

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...... and RASAeroII (RA2 is free, but requires contacting the developer via his website, iirc here on TRF he is username"aerocfd".
A little mix-up between RASAero II and aerocfd. RASAero II is free, and can be downloaded directly from www.rasaero.com . No need to contact the developers (myself and David "Coop" Cooper"), you can just go direct to the website and download the RASAero II software.


Chuck Rogers
Rogers Aeroscience
 

rharshberger

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A little mix-up between RASAero II and aerocfd. RASAero II is free, and can be downloaded directly from www.rasaero.com . No need to contact the developers (myself and David "Coop" Cooper"), you can just go direct to the website and download the RASAero II software.


Chuck Rogers
Rogers Aeroscience
Sorry Chuck my mistake.
 

EeebeeE

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I also suggest you download RAS Aero software which will give you more accurate altitude projections when factoring in mach speeds. You will still need Open Rocket to help determine total mass and CG, as well as determining size and type of recovery system. You may find 50K tough to reach with a 6" airframe. Might want to consider 5" if you can. Punching a 6" hole in the sky meets with a ton of resistance especially at mach speeds.
 

Exactimator

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In a related topic, would it be possible to braze the aluminum fins on (minimum diameter)? Students are not allowed to weld on campus, so we don't have any facilities for that.
Do you guys think brazing would be structurally sound?

-Jack
Have you checked for a Maker Space near you? They might have welding equipment you can use.
 

RocketFeller

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In a related topic, would it be possible to braze the aluminum fins on (minimum diameter)? Students are not allowed to weld on campus, so we don't have any facilities for that.
Do you guys think brazing would be structurally sound?

-Jack
When you say "minimum diameter" do you mean an aluminum airframe over the motor casing or do you mean fins attached to the motor casing? Either way, but especially if you are talking about fins attached to the motor casing, I would be worried about distortion.

In most cases some sort of fin can is employed on all aluminum rockets, at least from what I understand. Then again, I've been known to be wrong at times...
 

tfish

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Hey guys,

Apologies for asking such a basic question, but I'm tired of coming up empty with Google. Does anyone know a reliable way to calculate max altitude of a supersonic rocket? Alternatively, does anyone have a comprehensive chart of altitude records by engine type going through O/P engines?

Our rocketry club (all high school students with a few mentors) has received funding from the school to begin testing propellant for our 50,000 feet attempt. Our plan is to build a 30,000 NS case-bonded finocyl rocket engine using many of the same techniques as Derik Deville. We will static test this rocket and fully characterize the propellant beforehand. So my incredibly basic problem is whether or not this mid-O engine can take our rocket to 50,000 feet even if we designed it perfectly. Every rocket altitude calculator gives me a different answer and I'm having issues with rocksim's custom engine input, which I will be re-visiting soon.

To summarize, will a 30,000 NS rocket engine with a 6" diameter send a well-designed rocket to 50,000 feet?

I hate it when I see threads where inexperienced members ask for help without any detail or seeming effort put into their posts especially when this community offers such extensive advice, so I tried to be detailed.

Any and all help is appreciated.

-Jack
Jack, To start with you've got a very good mentor.

If you look at the Tripoli Research O motor records there are 2 using 6" motors/Rocket. The better of the two used 36 pounds of propellant and flew to >39K (lower then your goal). A recent O altitude flight used a 98mm "O" motor. Motor specs on it unknown. The rocket and motor where all optimized and achieved 68K+.

A quick Burnsim (a Research motor simulation program) with a mild well behaved formula gives a propellant length around 37" . Throw in 6 more inches for a nozzle and retention, 3" on the top end of the motor gives a rough length of 46" long which is a very short and heavy 30K n/S O motor. If you move down to a 5" motor things look like 46" of propellant . Throw in 5 for noz etc..3 for top of motor gives you a 5 inch motor roughly 54" long.

It takes X amount of propellant to make a 6" dia rocket go to 50K
It takes Y amount of propellant to make a 5" rocket go to 50K
Blah Blah Blah for 98mm.

Some of the issues have to do with the length of the motors. Long skinny motors..all that propellant wants to exit the nozzle at the same time and things are getting beat up inside...erosive. The bigger the motor (cores) (=less propellant) have more room for all the propellant to exit the nozzle with not as much stuff getting beat up on the way out.

Just some things to think about

Tony
 

JackO

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I also suggest you download RAS Aero software which will give you more accurate altitude projections when factoring in mach speeds. You will still need Open Rocket to help determine total mass and CG, as well as determining size and type of recovery system. You may find 50K tough to reach with a 6" airframe. Might want to consider 5" if you can. Punching a 6" hole in the sky meets with a ton of resistance especially at mach speeds.
Hey Eebee,

Awesome thanks for all the info. Yeah, we drew up a scale of the actual rocket on the board today after school and realized that a 4.5 " diameter would be much more appropriate all around. I had picked up the 6" diameter notion based off of the increased burn time and ease in casting, 4.5" should work much better.

-Jack
 

JackO

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Have you checked for a Maker Space near you? They might have welding equipment you can use.
Hey Exactimator,

I had not heard of the concept. I did a quick search and did not find anything nearby that looked within our budget. We'll probably end up borrowing the equipment from a member's family. Either way, we won't need any welding done until next year.

-Jack
 

JackO

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When you say "minimum diameter" do you mean an aluminum airframe over the motor casing or do you mean fins attached to the motor casing? Either way, but especially if you are talking about fins attached to the motor casing, I would be worried about distortion.

In most cases some sort of fin can is employed on all aluminum rockets, at least from what I understand. Then again, I've been known to be wrong at times...
Hey Dan,

I intended to weld/braze the fins directly to the casing, but since this engine might end up being pretty over-powered, we may end up using a fin can of some kind of another. I'll look at some of the other configurations members of the forum have gone with.

-Jack
 

JackO

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Jack, To start with you've got a very good mentor.

If you look at the Tripoli Research O motor records there are 2 using 6" motors/Rocket. The better of the two used 36 pounds of propellant and flew to >39K (lower then your goal). A recent O altitude flight used a 98mm "O" motor. Motor specs on it unknown. The rocket and motor where all optimized and achieved 68K+.

A quick Burnsim (a Research motor simulation program) with a mild well behaved formula gives a propellant length around 37" . Throw in 6 more inches for a nozzle and retention, 3" on the top end of the motor gives a rough length of 46" long which is a very short and heavy 30K n/S O motor. If you move down to a 5" motor things look like 46" of propellant . Throw in 5 for noz etc..3 for top of motor gives you a 5 inch motor roughly 54" long.

It takes X amount of propellant to make a 6" dia rocket go to 50K
It takes Y amount of propellant to make a 5" rocket go to 50K
Blah Blah Blah for 98mm.

Some of the issues have to do with the length of the motors. Long skinny motors..all that propellant wants to exit the nozzle at the same time and things are getting beat up inside...erosive. The bigger the motor (cores) (=less propellant) have more room for all the propellant to exit the nozzle with not as much stuff getting beat up on the way out.

Just some things to think about

Tony
Hey Tony,

You're absolutely right; I'm extremely grateful to be able to get Mr. Deville's advice. His projects are really incredible.

I am very familiar with BurnSim (I've read Prof. McCreary's book). Before we get the length sorted for the full engine, we're going to characterize the new formula. I brought up the 6" diameter here because I wanted to reduce the erosive burning (which I am going to read up some more on) as well as ease of casting and longer burn time as the club will always take safety over performance. Thanks for the advice everyone. We'll drop the diameter to 4.5". Just on the fence about the .25" wall versus the .187" wall as the finocyl grain will be case-bonded.

-Jack
 
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