Low powered 75mm motor for testing

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Not really a laughing matter. Let me ask you this. What club are you planning on flying this rocket with, since no one else has really asked...?


READ. THE. FREAKING. BOOK.

You'll learn more from the book about basic rocket principles than you will pissing folks off on TRF. You and your classmates are in college. You should be able to open a book and read it and be able to apply the basic concept of what you've read to the topics at hand. If you aren't able to draw conclusions from the literature you are reading, time to seek out another book. Same goes for websites... There are more than a few that explain basic rocket principles.

At this point, you're just winding everyone up on the forums. This is why the student groups have been a sensitive topic as of late. No one wants to come in and get their basic L1 and learning concepts before moving onto their big rocket, then they vanish. It's just a resume builder for them.


No... Don't shift the blame elsewhere. Be more vocal about it. You're just rolling over playing dead and trying to get pity points out of the rocketryforum folks. Do your due diligence and read up on everything you possibly can. There are other sites than TRF where you can learn focused information on topics that you've been discussing. Use them. The basic questions you are asking are not going to be covered in an L2 exam.

Get crackin'. If you ask the right questions you may get some guidance to these sites, though at least one has been mentioned in this thread already...
one of my replies out of the hundred or so on here, i mention that it took 4 months for the committee to go from "build a L3 rocket to hit 20K feet from scratch and an active drag system for space port this year" to "build a L2 rocket kit to hit 10K with an active drag system"
i have been very vocal about my concerns since day 1 when i posted on TRF about our project and received some infomation about how its going to be really really tough and dangerous to do this in 5 months. I have always said this to the comittee but they have pushed and pushed the students to do an L3 rocket. Im not expecting any pitty. My OP mentioned nothing of victim or pitty, just asked a question about motors and a good starting point.

I have read the book, well, most of it. Since it is older, it did not cover everything but it covered most. Information about the parachutes has been very helpful.

ill reply more in a bit. trying to catcha train
 
ok, thanks. i will look into those. Its all about the drag amount im guessing in order to have a smaller chute to fill a smaller volume.
I have looked up some information and i have seen that a drouge chute that reduces velocity to 50MPH before main deployment is ideal. So far im at 67MPH but hta is with the main opening 10 seconds after the drouge. I might just pop the main based on altitude such as
Not entirely true unless you specifically mean just the level 1, which is kind of a gimme compared to 2 and 3... I did have my level 2 cert on my resume and the last three places I worked at (all in aerospace, not SpaceX, but the third was Orbital ATK) brought it up in the interview and seemed impressed by what I told them about HPR in response to their questions.
I specifically mentioned L1 in my post. Especially since 95%+ of these kids that show up and are once and done. If it was brought up in an interview situation, almost none of the one and done folks wouldn’t be able to intelligently talk about it in an interview situation. L3, very different story.
 
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I've not commented on these up to this point but I'm going to offer some advice. This is coming from a fellow college student on a rocketry design team.

One of your biggest issues is your attitude. You need to act more professional and courteous to those giving you their knowledge. Looking in without knowing anything about you or your team, you come across as childish and ignorant. It is okay to now know things, but being dismissive when receiving information is part of the reason people are not wanting to help you. I agree with those saying that this is just an accident waiting to happen. The team I am on gets regular support from multiple L3 certified people, I am L2 and so is one other member. I understand the push from the professors, but you are not free of blame. One thing that should have been done long ago was for your team to take some time (more than 1 hour, ideally ~12hrs each) to research the requirements that gave and read about rocketry and then compile this into a report of some sort that you can present. In this report would be a REALISTIC timeline that has contingencies for launches cancelled due to weather and for delays in shipping and building. This would have shown them some real work on your part and that this project wasn't feasible to begin with. Included in your research should have been looking at the other colleges that do similar things and lay out how they do it. A lot of us have our own websites to advertise the team for sponsors. I understand that this is a capstone project and not a design team, but you would have seen that design teams, that have many more members, take the same time or longer. You only have 5(?) people total which means you would each have to put in a much larger amount of time per week. The committee is not going to take you seriously if you just go to them and say "we can't do it" without any explanation. If you went to them with a proper report with timelines and the requirements for each person in terms of hours you might have had a much different results. The reality is that the professors on the committee is also to blame, but your attitude and lack of professionalism is also to blame for the lack of people wanting to help. Take your time to write out your posts and act like a professional who is working on a project and less like a child being forced to do something that they don't want to.

If you can clean up your act, I'd be willing to help. I have been out to many rocket launches and have helped launch my design teams rocket to ~30k ft. There are many people that are able to help. You still need someone local to look over your work and for launches, but there is a wealth of information that is available to those who can be respectful of those who have the information.

One thing you really need to look up is how the motor works. SU motors are nice and easy for certs but they don't teach you how the motors work themselves. This is why I am present when my teams builds their motors. it saves our L3 mentor from needing to be there and I can teach them the proper ways to assemble the reloads. These motors are not small by any means and contain enough energy to seriously hurt or kill your entire team and they need to be respected.
 
I specifically mentioned L1 in my post. Especially since 95%+ of these kids that show up and are once and done. If it was brought up in an interview situation, almost none of the one and done folks would be able to intelligently talk about it in an interview situation. L3, very different story.
Fair enough.

I might just pop the main based on altitude such as 500 ft AGL
Most dual deploy altimeters are set up to deploy the main based on altitude as standard. The velocity under drogue isn't that critical, 67 mph is fine. The drogue's main role is to stabilize your payload section and keep it pointing away from the rest of the rocket so that the main doesn't get tangled, not really to slow the rocket down.
 
I've not commented on these up to this point but I'm going to offer some advice. This is coming from a fellow college student on a rocketry design team.

One of your biggest issues is your attitude. You need to act more professional and courteous to those giving you their knowledge. Looking in without knowing anything about you or your team, you come across as childish and ignorant. It is okay to now know things, but being dismissive when receiving information is part of the reason people are not wanting to help you. I agree with those saying that this is just an accident waiting to happen. The team I am on gets regular support from multiple L3 certified people, I am L2 and so is one other member. I understand the push from the professors, but you are not free of blame. One thing that should have been done long ago was for your team to take some time (more than 1 hour, ideally ~12hrs each) to research the requirements that gave and read about rocketry and then compile this into a report of some sort that you can present. In this report would be a REALISTIC timeline that has contingencies for launches cancelled due to weather and for delays in shipping and building. This would have shown them some real work on your part and that this project wasn't feasible to begin with. Included in your research should have been looking at the other colleges that do similar things and lay out how they do it. A lot of us have our own websites to advertise the team for sponsors. I understand that this is a capstone project and not a design team, but you would have seen that design teams, that have many more members, take the same time or longer. You only have 5(?) people total which means you would each have to put in a much larger amount of time per week. The committee is not going to take you seriously if you just go to them and say "we can't do it" without any explanation. If you went to them with a proper report with timelines and the requirements for each person in terms of hours you might have had a much different results. The reality is that the professors on the committee is also to blame, but your attitude and lack of professionalism is also to blame for the lack of people wanting to help. Take your time to write out your posts and act like a professional who is working on a project and less like a child being forced to do something that they don't want to.

If you can clean up your act, I'd be willing to help. I have been out to many rocket launches and have helped launch my design teams rocket to ~30k ft. There are many people that are able to help. You still need someone local to look over your work and for launches, but there is a wealth of information that is available to those who can be respectful of those who have the information.

One thing you really need to look up is how the motor works. SU motors are nice and easy for certs but they don't teach you how the motors work themselves. This is why I am present when my teams builds their motors. it saves our L3 mentor from needing to be there and I can teach them the proper ways to assemble the reloads. These motors are not small by any means and contain enough energy to seriously hurt or kill your entire team and they need to be respected.
I do agree with what you have said. Thank you for the information and ou must have not read my replies in the beginning when I was not dismissive. I have been very grateful and thankful for the information I have received here. Below are all my posts stating so. I have not been dismissive or childish about it. We don’t have a mentor.. its that plain and simple. There is no other way to answer that question. I have mentioned many times in this thread why we don’t have one, and its due to previous years of universities trying to do this in 5 or 6 months and the local fields don’t want to risk it. This is why we were able to do our basic L1 and L2, but anything above that, they scrambled when we have asked for help.

your last paragraph is exactly why i asked the Original question in the first palce haha. I have only used 2 motors, the h550 and the j270..

Again I will remind you I just got my L2. We have had a total of 2 flights, so yes, I am ignorant to this stuff, as I have admitted many times.

I put many hours into the time it would take tot do this, in fact, many forum users told me it would be dangerous and irresponsible and I followed their advice to try and talk the committee into a different but related project. The first project report which was due 2 weeks (October) into class I specifically told the committee the expected timeline. Post 78 on this thread mentions this. The committee originally wanted a L3 rocket in 4 months and then an active drag system in 2 months. Our state gets roughly 3 or 4 launches a year due to weather, this was brought up to their attention many many times. It was not until Mid January when the committee realized it was not going to work for our team to do all of this. I received an email yesterday from the committee still wanting us to pursue the launch this week with what we have… they don’t get it and wont get it. I have told them I will not launch and if they want to fail me then do so, but I will not launch like I said in post 64.


thank you for reading this post and understanding whats going on. Its been super tough to deal with a committee who does not really care about standards


“ok, based off of the recommendations, i have narrowed it down to 4 motors. From here, i am good. thanks for the help.”

ok, moving on to post #15
“thats cool. thanks for that information. I did not know that”

post #22
“all the stuff i have learned about HPR has been from these forums and posters such as yourself. Its been very very very helpful.”

post #23
“i agree, but none wanted too. as soon as they find out its for a university, they scramble., everything i have learned about HPR has been from here. So far, i think we have done pretty good for the amount of time we have had. Nothing about grain bonding was ever covered in our written L2 exam, so i wouldnt call it basic or common knowledge, hence the reason for a mentor, but since that is slim to none, i asked on here hoping to get the correct guidence, and i did, which was great”

post #29 again, I was grateful for the help.
“i now know what grain bonding is, and will be contacting the motor supplier for instructions for our motor if needs be. Thanks.
This thread can be closed or locked if needs be i have learned lots and lots from you guys and grateful for it.”

then I took a small brak with some comments here and there between post 29 and 56 where I state:

“Thank you for the help and that great check list. We have many sims of our rocket with correct weights and measurements. I really do appreciate your help with this. We have ONE level 2 flight for each of us and thats it. We are NEW L2's. This is not a L3 flight”

post 58 someone mentiosn that we are new L2’s and most likely would not know about grain bonding.
“It is important for everyone to remember, he has only flown one rocket twice. Once on a H550 cert one , then J270 in the same rocket for cert two. The L2200 will be his 3rd flight, ever.”
 
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second half:
post 61 I thank again for the information:

“Thank you for letting me know that the L2200G is for experienced L2's. We are finding that out quickly. i have sent emails to our local club for months now with zero response. Everyone is so busy with jobs and family, that im not blaming them for not wanting to help a university”

Post 64:
“Im SUPER glad you and others are telling me not to launch and to wait. I told my team last night and the filed that i would rather wait and launch when we have tested everything because NO ONES LIFE is worth it. its way way to dangerous.

Attached is our sim of the rocket. Can i send the Images of our ADS idea to you in a private message?

also, the launch information has been set to default so others can change it to wahtever they want on this file. i forgot to mention that”

post 68
“you and me both. I am concerned as well, and im feeling the pressure from the school and the capstone committee. Its alot of unwanted stress. I have told them we have to be safe or we could ruin it for the field and other launchers... hey, maybe this is why its hard to find a mentor?”

post 78 where I explain what the school originally wanted
“I was talking to someone else and ORIGINALLY the school wanted us to do a L3 rocket from scratch, spaceport americaup, 20k flight, and an active drag system. I told them that was way to much to do, so they chopped it down to a L2 10k flight with an ADS and next year the new students will take the same rocket to spaceport, but next years students will be in the same boat as us haha”

post 89 where I had admitted again that I feel ignorant because of this
yup, we have had no support, no lectures on rocketry, no books, no nothing. I actually went out and got the model rocektry handbook and gave it to the professor at my own cost.
It almost makes me feel stupid in a way because i know literally nothing except the small L2 j270 i used
Post 91, I thank the forums again for the information
thanks for this information. I left most launch prefs at default until we get all the correct weights. I THINK our launch rail is 8 feet that the filed is letting us use.
Ground hit is a little high, a bigger chute or less mass is a good idea. Ill bring that up to them tonight.
we have 2 or 3 eggtimer brand altimeters and GPS going in for redundancy
As for weights, would a total constructed weight be good? or do i need to get the weights of EACH component separately?
in OR, how do i add epoxy weight and posistion to the rocket?

thanks

post 102 I thank them again with many explanation marks
THANK YOU!!!!!!

and finally post 113
ok, thanks. i will look into those. Its all about the drag amount im guessing in order to have a smaller chute to fill a smaller volume.
I have looked up some information and i have seen that a drouge chute that reduces velocity to 50MPH before main deployment is ideal. So far im at 67MPH but hta is with the main opening 10 seconds after the drouge. I might just pop the main based on altitude such as 500 ft AGL
 
Fair enough.


Most dual deploy altimeters are set up to deploy the main based on altitude as standard. The velocity under drogue isn't that critical, 67 mph is fine. The drogue's main role is to stabilize your payload section and keep it pointing away from the rest of the rocket so that the main doesn't get tangled, not really to slow the rocket down.
thank you for this explanation. The good news is, i got the rocket to be stable at 4.1 cals and drogue to slow rocket to 45MPH, even though thats not its main job. I re-did the entire sim from a scratch model with no added things. Something was way off on the file when 3 of us had differnt values for altitudes by 3000 feet.
My vote is to get rid of the 9lb payload and use an aeropak adapter to use a 54mm motor to test the flight of the rocket and behavior before adding the payload as well as the ADS. This will at least give us a clue to what to do next
 
So you've got 2 months left before you wrap up the school year and you want to have a successful flight on your big rocket. How do you get from here to there? Let's start by looking at failure modes. Your major risks of failure are, in approximate order of likelihood:
1. Recovery system failure (parachutes, recovery harness, hardware/connections)
2. Deployment system failure (altimeters, ejection charges, shear pins)
3. Structural failure (fin comes off, rocket folds over, etc.)
And, of course, the big daddy is "run out of time".

Here's the approach I would recommend taking for the rest of the project.
1. Build an AV bay now to fit both your LOC IV and your big rocket. I believe that they're both 4" diameter, so that should be possible. You'll need some hardware and supplies (U-bolts, threaded rods, charge wells, plywood sled, fiberglass end caps, e-matches, black powder, etc.). There's a thread here dedicated to pictures of AV bays, so you can get lots of ideas there. Make it with redundant altimeters and GPS tracking so you can just drop it into your big rocket when that is ready to fly.
1a. Ground test ejection charges in the LOC IV.
2. Test fly your AV bay in a dual deploy configuration on your LOC IV. This lets you get your bugs out on a less valuable rocket. Fly it o a small motor--you want to see all of the deployment events. Make a checklist for flight that you can drop right into your big rocket flight checklist.
3. Finish out your big rocket. Make sure you have recovery hardware and harness, parachutes, etc. Ground test ejection charges in the big rocket. Update your simulations with final rocket weights and CGs with the mass override function.
3a. Go through your launch checklist a couple of times to find where things don't make sense or what you want to change.
4. Fly your big rocket on a smaller motor (K1000?). I wouldn't fly the 9-lb payload, which means you might be able to use the chute you have right now instead of buying another one. This is about making sure that the systems all work, and that you're comfortable flying the motor and the big rocket. You'll find some more things in your checklist that you want to change as you go through it. Ask someone experienced with large motors at the club you're launching with to look over your shoulder as you assemble your motor. For motor selection, either use the RAS to fly a 2-grain 75mm motor in your big case or adapt down to a 54mm K motor. I would select the motor for ~ 10:1 thrust to weight ration and an altitude of maybe 3000 feet. You want to make sure that you can see all of the ejection events and not go so high that you'll need your tracker (fly with it anyway!).
5. If and only if everything has gone well so far, fly the big motor with the payload. Invite incoming students to the launch and prep so that you can transfer some of the things you've learned to them so they're not quite so far behind. I'm guessing that you won't get to this step. That's OK. You've done a lot this year and learned a lot too.
 
Separate from what to do, here's some suggestions for interacting positively with people on this forum. What you haven't seen is that there are students (middle school to college) who drop in every month who have some giant project and want everyone here to design it for them because they don't really know anything. It gets really old. What gets a positive response is people who have done homework and come in and ask for help reviewing the work that has already been done.

I can guarantee that if you had started this thread with "I need to fly lower than my planned 10K flight to prove out my simulation. I've got this casing already. These motors seem like good options--do you all have feedback on what I should use for a test flight?" That approach shows that you've done some work and are looking for expertise. Your first post came off like you hadn't done anything and wanted us to design it for you based on minimal information. That will never get a good response.

So when you've designed your AV bay, show us some sketches of what you're planning (or screen shots from a CAD model) and ask for feedback. Same thing with your launch checklist. Look at some L3 documentation threads on TRF for launch checklists and come up with one of your own. Post it up and ask for feedback. The key is that you need to do some basic research and design before asking for help.
 
thank you for this awesome reply and check list. Between this list and Kramers list as well as a few others that have personally DM'd me, i am super grateful.

I told the committee yesterday (post 64 of mine) that i would rather fail the class than launch an unsafe rocket. Its not fair to the local field to risk the lives of others and ruin the sport because we have 6 months to build a L3 rocket with an active drag system and thats not enough time with no mentor. So we spent 3 months getting L1 and L2, in fact, we did both at the same launch day. It was an 8 hour sport launch. We received L2 at the end of the year. Mid january is when we received our wildman extreme kit and started the build.
Last night i scratched the entire sim we had i re-started from the begining. I removed the payload because thats adding extra stress to the rocket before we even have a chance to test the rocket. Doing this, the sims said our chute was just fine. We have simied on an L1420, K1000, and even a few 54mm SU motors.
 
I told the committee yesterday (post 64 of mine) that i would rather fail the class than launch an unsafe rocket. Its not fair to the local field to risk the lives of others and ruin the sport because we have 6 months to build a L3 rocket with an active drag system and thats not enough time with no mentor.
Congratulations on taking a first step towards being a good engineer. Knowing when to say no on safety grounds is extremely important.
 
OK, Phil McCracken aside, I read a lot of the posts. Not all, I admit. My eyes started glazing over about page 3.5.
Anyhow...
One thing that I've not seen mentioned is Thrustcurve.org. Use this! If you have a built rocket, just enter the specs into the app or website, and hit run motor guide.
It will help you select the right motors. It's a easy, quick way to get a close estimate on altitude on a variety of motors.
 
OK, Phil McCracken aside, I read a lot of the posts. Not all, I admit. My eyes started glazing over about page 3.5.
Anyhow...
One thing that I've not seen mentioned is Thrustcurve.org. Use this! If you have a built rocket, just enter the specs into the app or website, and hit run motor guide.
It will help you select the right motors. It's a easy, quick way to get a close estimate on altitude on a variety of motors.
Lt72884,
Where are you located grasshopper?
 
Separate from what to do, here's some suggestions for interacting positively with people on this forum. What you haven't seen is that there are students (middle school to college) who drop in every month who have some giant project and want everyone here to design it for them because they don't really know anything. It gets really old. What gets a positive response is people who have done homework and come in and ask for help reviewing the work that has already been done.

I can guarantee that if you had started this thread with "I need to fly lower than my planned 10K flight to prove out my simulation. I've got this casing already. These motors seem like good options--do you all have feedback on what I should use for a test flight?" That approach shows that you've done some work and are looking for expertise. Your first post came off like you hadn't done anything and wanted us to design it for you based on minimal information. That will never get a good response.

So when you've designed your AV bay, show us some sketches of what you're planning (or screen shots from a CAD model) and ask for feedback. Same thing with your launch checklist. Look at some L3 documentation threads on TRF for launch checklists and come up with one of your own. Post it up and ask for feedback. The key is that you need to do some basic research and design before asking for help.

Lt72884,
Where are you located grasshopper?
northern utah
 
@Lt72884 I am also on the East Coast, so it would be difficult for me to provide any mentoring in person, but I am happy to get on Zoom calls and provide some mentoring. PM me if interested.
 
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