Need HELP with making a rocket!

[jqavins]

You'd think that there's enough information there to Google it for myself "vgeby fpv camera", but I'm coming up empty. I went to amazon.co.uk and searched, and I still can't find it. Would you post the manufacturer's model number? That should enable us over here to find it for ourselves.

In any case, from what I can see and guess, I bet it's overcomplicated and too expensive. It seems, if I'm guessing right, to be meant for transmitting live from a quad copter or the like back to the controller so that the pilot can operate the vehicle from an on board PoV. For a rocket, that's unnecessary, as you won't be doing any piloting, it will probably move very quickly out of range of your receiver unless you've got a good directional antenna, and then you wouldn't be able to keep the antenna pointed fast enough for a sufficient quality data link for video.

What you'll be doing with video is one of two things. Either:

1. You'll be recording during the flight and watching later, or
2. You'll be doing a ground-breaking R&D project that gets the whole community excited and really impressed in the space of less than a year on a student budget.

For option 1, it looks like this camera is overkill, if what I've deduced about it is right. Overkill in at least one respect, and I don't know if it's adequate in another, since I can't tell if it has any on-board recording.

For option 2, I don't know, maybe it would be a good choice, but I don't think that's really worth talking about.

 

[smstachwick]

I agree. Something more like a GoPro or 808 keychain camera would be better, but given that 808s are basically a hobby unto themselves with usability varying wildly from very basic to bricked out of the box…

(Thread here)

I’d either spring for a GoPro (maybe a used and very basic one) or the Estes Universal Astrocam I PMed you. An old, mostly disused smartphone may work as well.

 

[Ayush Chauhan]

UPDATE!
Hello guys, The parts for the rocket have finally arrived.

I ordered the the kit above.

For now I am making a model of the rocket on Open Rocket Software and I will run simulations with different motors. Then I will make a CAD model of the rocket and run CFD simulations. Then I will get on to assembling the rocket.

How do you guys like the plan?

Thanks

 

[jqavins]

Great. It's been a long time, so there are surely things I don't remember, and I'm afraid I am not inclined to reread the whole thread. As I recall, you decided to take our advice and got a smaller kit to build first. Have you built it? Flown it? How did it go?

For the rest of the plan, why are you doing the CAD and CFD? If it's for the experience of doing it, that's great. For any directly practical reasons, it's unnecessary. By all means, do it if you want to, just know that Rocketarium's design and testing ensure that it is stable and safe when build as designed, and OpenRocket's simulations are adequate to ensure that it will be stable and perform well using your own actual, measured weights, and to predict optimal ejection delays, rod exit speeds, and apogee altitudes with various engines.

OR is all you need.
OR is all you need.
OR is all you need.
OR is all you need.
OR is all you need.
OR is all you...
(Go fly it yeah, yeah, yeah. Go fly it yeah, yeah, yeah.)
OR is all you need.

 

[smstachwick]

UPDATE!
Hello guys, The parts for the rocket have finally arrived.
View attachment 590779
I ordered the the kit above.

For now I am making a model of the rocket on Open Rocket Software and I will run simulations with different motors. Then I will make a CAD model of the rocket and run CFD simulations. Then I will get on to assembling the rocket.

How do you guys like the plan?

Thanks

I was wondering if you’d return!

I’m sure we’d all be interested in seeing the sim results. You sound like you’re being thorough with your tests of this kit at least.

Fly the field and be safe.

 

[Ayush Chauhan]

I was wondering if you’d return!

I’m sure we’d all be interested in seeing the sim results. You sound like you’re being thorough with your tests of this kit at least.

Fly the field and be safe.

Thank you!

I will surely update you on the simulations... Since I have the pressure of A-levels, I will only be making the rocket on every Monday for 2hrs. So it might take some time to make the full model and get the sim results.

 

[Ayush Chauhan]

Great. It's been a long time, so there are surely things I don't remember, and I'm afraid I am not inclined to reread the whole thread. As I recall, you decided to take our advice and got a smaller kit to build first. Have you built it? Flown it? How did it go?

For the rest of the plan, why are you doing the CAD and CFD? If it's for the experience of doing it, that's great. For any directly practical reasons, it's unnecessary. By all means, do it if you want to, just know that Rocketarium's design and testing ensure that it is stable and safe when build as designed, and OpenRocket's simulations are adequate to ensure that it will be stable and perform well using your own actual, measured weights, and to predict optimal ejection delays, rod exit speeds, and apogee altitudes with various engines.

OR is all you need.
OR is all you need.
OR is all you need.
OR is all you need.
OR is all you need.
OR is all you...
(Go fly it yeah, yeah, yeah. Go fly it yeah, yeah, yeah.)
OR is all you need.

I am just doing the CFD and CAD designs for the experience of it and just cuz its fun.

I will however will be putting an Altimeter in the Arcas rocket.

I will be using this as the Altimeter for the flight. So I will need some help with how to set up Altimeter in the rocket. The reason for putting the altimeter is because I will be modelling the flight path using coding in python just to make things complete as I am taking this as an official project.

 

[Ayush Chauhan]

Hello guys,

Its been some time since I last updated you guys! Sorry for that, was a bit busy with study and other external projects.

I have finally got time to work on the rocket (Frangible Arcas Kit) I just finished making the rocket's model in Open rocket and started testing different 24mm motors. I noticed one thing.



If you see in the graph at apogee the vertical velocity of the rocket is about 113.5 m/s meaning the rocket can climb further if the deployment charge is not fired. The deployment charge fires at about 10 seconds at with the vertical velocity is 113m/s as you can see below:



My question is:
If we somehow were able to control the deployment of the charge and make it so that the charge gets deployed when the vertical velocity of the rocket is 0m/s at that point it will be at it's natural apogee. When we deploy the charge at 113.5m/s the rocket will not climb any further.

I have a Altus Metrum Easy Mini v3.0 Dual Deployment Altimeter, not sure if this will be able to control at what time the deployment charge goes off. But can we use or manipulate easy mini to do that?


Also just in case you are wondering how the Arcas Design looks like, here it is:



Please provide feedback if you think I can make any improvements with the stability of the rocket. At the moment to make this rocket stabilized I put a 200 grams weight in the nose cone of the rocket (not sure if I should be doing this).

I will also make a CAD model for the case for Easy mini so it stays in place during the flight and 3D print it (I will also make sure to have enough gap for the deployment charge's pressure to travel up the body tube so the parachute deploys). I put the easy mini in the middle of the rocket. Please give suggestions on that too, if I can improve anything.

Thank you! As always guys for supporting me do this project!!

 

[smstachwick]

Hello guys,

Its been some time since I last updated you guys! Sorry for that, was a bit busy with study and other external projects.

I have finally got time to work on the rocket (Frangible Arcas Kit) I just finished making the rocket's model in Open rocket and started testing different 24mm motors. I noticed one thing.

View attachment 605906

If you see in the graph at apogee the vertical velocity of the rocket is about 113.5 m/s meaning the rocket can climb further if the deployment charge is not fired. The deployment charge fires at about 10 seconds at with the vertical velocity is 113m/s as you can see below:

View attachment 605907

My question is:
If we somehow were able to control the deployment of the charge and make it so that the charge gets deployed when the vertical velocity of the rocket is 0m/s at that point it will be at it's natural apogee. When we deploy the charge at 113.5m/s the rocket will not climb any further.

I have a Altus Metrum Easy Mini v3.0 Dual Deployment Altimeter, not sure if this will be able to control at what time the deployment charge goes off. But can we use or manipulate easy mini to do that?


Also just in case you are wondering how the Arcas Design looks like, here it is:
View attachment 605942


Please provide feedback if you think I can make any improvements with the stability of the rocket. At the moment to make this rocket stabilized I put a 200 grams weight in the nose cone of the rocket (not sure if I should be doing this).

I will also make a CAD model for the case for Easy mini so it stays in place during the flight and 3D print it (I will also make sure to have enough gap for the deployment charge's pressure to travel up the body tube so the parachute deploys). I put the easy mini in the middle of the rocket. Please give suggestions on that too, if I can improve anything.

Thank you! As always guys for supporting me do this project!!

You are correct, generally the desirable thing to do is select the delay time such that deployment velocity will be low. However, weathercocking, manufacturing tolerances, and other variables mean that deployment velocity will never be zero. Sometimes it can in fact be quite high.

I’d suggest looking into different motor types, as the 8 seconds offered by the F32 is clearly not sufficient. The AeroTech F67W offers 9, the F52C offers 12, but these are 29mm types. I think some reloadables offer 14.

Deployment altimeters generally deploy right at detected apogee though, not at zero airspeed. If it were looking for zero airspeed it would never deploy and the rocket would come down like a streamlined anvil.

So I guess it’s up to you. Deployment electronics, or 29mm mount? I’d think it would be simpler to upgrade the mount, but it’s your rocket.

Regarding the nose weight, be sure that you have sufficient rod exit velocity, at least 30 mph, and also be sure your recovery system can take the strain of a 200g weight separating into the airstream. Also be sure to think about what happens if/when it bangs into the airframe. High-power recovery harnesses are quite long for this reason.

 

[smstachwick]

Oh yes! I have found some dealers that are selling G-class motors for an affordable price. And when you say reloadable motors and single-use motors, could you please differentiate them?
Thanks

Reloadable motors come as a hardware set and a reload kit. The hardware is cleaned and reused after each flight, the reload kit is disposable. Single-use ones are just thrown away and typically come preassembled.

Reloadables offer lower cost per flight at the higher up front cost of acquiring hardware, and the risk of losing an expensive casing.

AeroTech’s reloadable system is dubbed RMS (Reloadable Motor System) and is quite popular here in the US. IDK its status in the UK.

 

[smstachwick]

Oops! I replied to one of the oldest posts in this thread. Please disregard

 

[Ayush Chauhan]

You are correct, generally the desirable thing to do is select the delay time such that deployment velocity will be low. However, weathercocking, manufacturing tolerances, and other variables mean that deployment velocity will never be zero. Sometimes it can in fact be quite high.

I’d suggest looking into different motor types, as the 8 seconds offered by the F32 is clearly not sufficient. The AeroTech F67W offers 9, the F52C offers 12, but these are 29mm types. I think some reloadables offer 14.

Deployment altimeters generally deploy right at detected apogee though, not at zero airspeed. If it were looking for zero airspeed it would never deploy and the rocket would come down like a streamlined anvil.

Is there a way to add something that checks which way the rocket is facing and then deploy the charge when the rocket is facing downwards as its descending after reaching 0m/s vertical velocity (max apogee).

However, 29mm mount is doable but that will cause the rocket to be less stable because the 29mm motors are heavier so I would most probably have to add 50ish grams of weight on the nose cone of the rocket so it's stable.

The problem is I already made a 24mm mount, so I think I might have to order a 29mm mount for the Arcas kit.

But also since F52C and F67W are more powerful motors that also means the rocket will deploy the charge at a very high vertical velocity again instead of the charge being deployed at 0m/s vertical velocity. I need to find a way to do that cuz this will just be wasting all moto's energy and I want an efficient flight.

Regarding the nose weight, be sure that you have sufficient rod exit velocity, at least 30 mph, and also be sure your recovery system can take the strain of a 200g weight separating into the airstream. Also be sure to think about what happens if/when it bangs into the airframe. High-power recovery harnesses are quite long for this reason.

What do you mean by "if/when it bangs into the airframe. High-power recovery harness are quite long for this reason."? The 200g weight will be sealed to one place in the nose cone. Now one thing that I am worried about is whether the deployment charge is strong enough to push the 200g weight or at lest the body backwards.

 

[smstachwick]

Is there a way to add something that checks which way the rocket is facing and then deploy the charge when the rocket is facing downwards as its descending after reaching 0m/s vertical velocity (max apogee).

Deployment altimeters exist. Usually they work by monitoring pressure altitude and triggering charges when it starts going back down, as this indicates apogee. Eggtimer makes popular kits but there are many.

However, 29mm mount is doable but that will cause the rocket to be less stable because the 29mm motors are heavier so I would most probably have to add 50ish grams of weight on the nose cone of the rocket so it's stable.

I forget, what kind of stability margin do you have? Generally you want to shoot for between one and two calibers. More than that increases weathercocking and your forward velocity at deployment.

The problem is I already made a 24mm mount, so I think I might have to order a 29mm mount for the Arcas kit.

Probably. Either way, you’re going to have to do something about deploying at over 100 meters per second, your rocket will probably not be strong enough to survive that even once. Upgrading the mount might be simpler than soldering electronics and wiring up charges.

But also since F52C and F67W are more powerful motors that also means the rocket will deploy the charge at a very high vertical velocity again instead of the charge being deployed at 0m/s vertical velocity. I need to find a way to do that cuz this will just be wasting all moto's energy and I want an efficient flight.

Understood. Remember the difference though between average thrust and total impulse. An F32T generates a nominal 32 Newtons of average thrust and a certified total impulse of 56.9 Newton-seconds.

An F52C generates a nominal 52 Newtons of average thrust and a certified total impulse of 66.2 Newton seconds. The average thrust is much higher but the total impulse is only slightly higher.

So you do get a lot more airspeed and a little more altitude, but four seconds of extra delay is a *lot* of coasting time. If it’s not more than you need, than it should be right on the money. I can’t imagine it’s going to be more than a hair short. Therefore your deployment speed should be lower with an F52-12C.

What do you mean by "if/when it bangs into the airframe. High-power recovery harness are quite long for this reason."? The 200g weight will be sealed to one place in the nose cone. Now one thing that I am worried about is whether the deployment charge is strong enough to push the 200g weight or at lest the body backwards.

When you have a nose of any size or type ejected from the body tube, it will flop around in the airstream. Once the chute opens, it will swing like a pendulum. Sometimes it will come into contact with the rest of the body unless you properly plan out the placement of your parachute and the length of your shock cord. You’re going to have to ask yourself if it’s strong enough to survive a 200g nose smashing into the fins or body tube at speeds close to that of the oncoming air, which can sometimes be 30mph or more if you’re launching in windy conditions and your rocket weathercocks a lot.

As for determining the success of ejection in the first place, you could always run a ground test. Secure the rocket to something anchored sturdily, face it in a safe direction, and run the motor or activate your electronic deployment charge. You’ll want to coordinate with range personnel to arrange a safe spot to do this.

Either that or a more experienced flier could help you judge the fit. Generally you want a snug but not tight fit unless you have a high risk of drag separation.

(minor edits)

 

[Ayush Chauhan]

I forget, what kind of stability margin do you have? Generally you want to shoot for between one and two calibers. More than that increases weathercocking and your forward velocity at deployment.

The stability on my rocket is 8.78cal.
Someone told me that the stability should be above 8cal so I made the rocket so it's 8cal stability.

Probably. Either way, you’re going to have to do something about deploying at over 100 meters per second, your rocket will probably not be strong enough to survive that even once. Upgrading the mount might be simpler than soldering electronics and wiring up charges.

Yea I might just order a 29mm motor mount kit.

Understood. Remember the difference though between average thrust and total impulse. An F32T generates a nominal 32 Newtons of average thrust and a certified total impulse of 56.9 Newton-seconds.

An F52C generates a nominal 52 Newtons of average thrust and a certified total impulse of 66.2 Newton seconds. The average thrust is much higher but the total impulse is only slightly higher.

So you do get a lot more airspeed and a little more altitude, but four seconds of extra delay is a *lot* of coasting time. If it’s not more than you need, than it should be right on the money. I can’t imagine it’s going to be more than a hair short. Therefore your deployment speed should be lower with an F52-12C.

Ohk! I understand. I will run some simulations tonight with a 29mm motor mount. And variety of different motors.
And see which motor is the best.

When you have a nose of any size or type ejected from the body tube, it will flop around in the airstream. Once the chute opens, it will swing like a pendulum. Sometimes it will come into contact with the rest of the body unless you properly plan out the placement of your parachute and the length of your shock cord. You’re going to have to ask yourself if it’s strong enough to survive a 200g nose smashing into the fins or body tube at speeds close to that of the oncoming air, which can sometimes be 30mph or more if you’re launching in windy conditions and your rocket weathercocks a lot.

As for determining the success of ejection in the first place, you could always run a ground test. Secure the rocket to something anchored sturdily, face it in a safe direction, and run the motor or activate your electronic deployment charge. You’ll want to corrdinate with range personnel to arrange a safe spot to do this.

Either that or a more experienced flier could help you judge the fit. Generally you want a snug but not tight fit unless you have a high risk of drag separation.

That makes sense! The shock chord is an elastic chord that's 6mm in width and is 90.4 cm long. In my opinion it should be strong enough to take such strong force.

 

[waltr]

The stability on my rocket is 8.78cal.
Someone told me that the stability should be above 8cal so I made the rocket so it's 8cal stability.

Yes, I saw the 8.8Cal in your sim. That is way too much and leads to wind cocking.
1 to 3 Cal is plenty.

 

[smstachwick]

Are you sure you’re not mixing that up with 8% of the overall length? That’s another rule of thumb that you may encounter, more commonly with stubby rockets though.

 

[jqavins]

Yes, I saw the 8.8Cal in your sim. That is way too much and leads to wind cocking.
1 to 3 Cal is plenty.

1 to 3 calibers is usually enough, and 8.3 calibers is certainly too much here. Long, skinny rockets need more than 1 to 3, and this is kind of tall, but not so tall as to need 8. Whoever told you 8 calibers was just plane wrong.

Another way to express the static is the CP to CG distance as a percentage of the total length. The caliber measure is the distance between the CP and the CG, divided by the diameter. For "normal looking" rockets, one to two is good. Another way, which some people consider superior, is to divide the CP to CG distance by the rocket's length. In that case, about 10% to 15% is good, no matter the diameter. A "normal looking" rocket tends to be about ten to twenty times as tall as its diameter, so these two methods come out the same. For long skinny rockets, and for short fat rockets, l'm one of those in the percent of length camp.

Your length over diameter (which is called fineness) is almost 23. So a static margin over 2 calibers probably called for. Your current margin, expressed the in the percent of length way, is 39%, so it's excessive any way you slice it. To get to 12.5%, the margin expressed in the more usual way, with your rocket's dimensions, would be 2.96 cal. Which is good news, since it means you can take out a lof of that nose weight, I'd guess somewhere in the ballpark of half of it.

OK, next, it's common, though not universal, to put the electronics up high in the rocket. With electronic deployment, you want room for the charges and parachute above it, but if it's only an altimeter then there's no reason not to put it way up. Sometimes people even put it in the nose cone. That can help you out, and I'll let you work out why it's a good idea.

Finally, you wrote "If you see in the graph at apogee the vertical velocity of the rocket is about 113.5 m/s..." That's not possible, and I'm shocked that no one before me has pointed this out. Why is this impossible? Because at apogee, the vertical speed is always zero; that's what apogee means! (Well, sort of.) If you look at simulation results, and you read that the vertical speed at apogee is anything other than zero, then you're reading it wrong.

 

[jqavins]

Are you sure you’re not mixing that up with 8% of the overall length? That’s another rule of thumb that you may encounter, more commonly with stubby rockets though.

Ninjad. That seems like a good hypothesis, but 8% is kind of stingy based on what I've read elsewhere.

 

[86mustang408w]

I've read thru a few pages, have you launched any rockets yet? For practice with the chute release, camera, altimeter? Just curious..

 

[Ayush Chauhan]

Finally, you wrote "If you see in the graph at apogee the vertical velocity of the rocket is about 113.5 m/s..." That's not possible, and I'm shocked that no one before me has pointed this out. Why is this impossible? Because at apogee, the vertical speed is always zero; that's what apogee means! (Well, sort of.) If you look at simulation results, and you read that the vertical speed at apogee is anything other than zero, then you're reading it wrong.

According to the graph I am pretty sure I was reading it right. I aware that at apogee the vertical velocity of the rocket is 0m/s but in the graph it showed otherwise.

OK, next, it's common, though not universal, to put the electronics up high in the rocket. With electronic deployment, you want room for the charges and parachute above it, but if it's only an altimeter then there's no reason not to put it way up. Sometimes people even put it in the nose cone. That can help you out, and I'll let you work out why it's a good idea.

I was been told that at apogee it's more likely for your rocket to be horizontal as it will make a sort of parabola and this makes sense, which is the reason why I decided to put the altimeter in the sort of rough middle of the rocket.

 

[Ayush Chauhan]

I've read thru a few pages, have you launched any rockets yet? For practice with the chute release, camera, altimeter? Just curious..

Nope. The rocket that I am making right now will be my first launch.

 

[Ayush Chauhan]

Yes, I saw the 8.8Cal in your sim. That is way too much and leads to wind cocking.
1 to 3 Cal is plenty.

I will get rid of the 200g weight in the nose cone of the rocket in that case. Which should also increase the altitude by a little and decrease the caliber to about 3-5 cal.

 

[Ayush Chauhan]

Also guys, just to mention I will be working on this project only on saturdays and sundays because during the week the workload on the school and my tuition is too much to squeeze in this project too. So please bare with me if I take too long to reply. Hope you guys understand!

Thank you all for your support!

 

[Ayush Chauhan]

Yes, I saw the 8.8Cal in your sim. That is way too much and leads to wind cocking.

What exactly is wind cocking?

 

[86mustang408w]

What exactly is wind cocking?

When the rocket leaves the rod it will dramatically make a turn, that sums it up. Thats why I asked if you have ever launched a rocket. Your first one will be a G motor????

You may be in for disappointment(unless it doesn't matter and you just want a grade), and to me a kind of a safety concern. Even for you...

 

[CalebJ]

According to the graph I am pretty sure I was reading it right. I aware that at apogee the vertical velocity of the rocket is 0m/s but in the graph it showed otherwise.

I was been told that at apogee it's more likely for your rocket to be horizontal as it will make a sort of parabola and this makes sense, which is the reason why I decided to put the altimeter in the sort of rough middle of the rocket.

The only thing I see plotted on that graph is a red line for altitude. What else are you seeing that makes you think the vertical velocity is 113.5m/s?

 

[techrat]

What exactly is wind cocking?

When the rocket launches it will turn INTO the direction of the wind, like a weathervane does.

 

[smstachwick]

What exactly is wind cocking?

A rocket behaves like a weather vane, rotating about its center of gravity to point itself into the wind. How much it does this depends on its airspeed, the wind speed, and its stability margin.

1-2 calibers (or 8-15% of your overall length, if I’m recalling that version correctly) will produce safe results. That’s stable enough that it won’t turn cartwheels but not so stable that it goes cruise missile in the merest zephyr.

 

[Ayush Chauhan]

When the rocket leaves the rod it will dramatically make a turn, that sums it up. Thats why I asked if you have ever launched a rocket. Your first one will be a G motor????

You may be in for disappointment(unless it doesn't matter and you just want a grade), and to me a kind of a safety concern. Even for you...

No, I will use a F or E motor for my first launch.

 

[Ayush Chauhan]

A rocket behaves like a weather vane, rotating about its center of gravity to point itself into the wind. How much it does this depends on its airspeed, the wind speed, and its stability margin.

1-2 calibers (or 8-15% of your overall length, if I’m recalling that version correctly) will produce safe results. That’s stable enough that it won’t turn cartwheels but not so stable that it goes cruise missile in the merest zephyr.

View attachment 606170

Alright, understood.