Spacex Starship with Superheavy

tal041482

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Hi everyone, New to the forum, and i know for now i will be taking a lot more then i am giving but todays question is, My son and I are working on building a Starship with Super heavy booster (Scratch Built 3d Printing) I know I have some laws that i need to follow regarding amount of thrust and final weight. I have confirmed that i am going to be within those rules but im close obviously.

Due to the distance between the First and Second stage, It looks like i am going to need to have a means to ignite the second phase after separation of the Super heavy Booster. I was doing some research and it looks like i can build an Arduino accelerometer to do this, However after some thought i might need a dual ignition source for the separation and the ignition, I was looking at using a small A motor to create a separation and Recovery deployment charge but I'm not sure what manner i would like to do that yet. I may 3d print a tube and use a gas blow off from the first stage for separation, That of course adds weight and I'm getting close to max weight.

we are looking at building this to "scale" so overall it will be a huge rocket, We are still in the design and size phase but so far its coming together nicely in concept just have a few items to finalize before we fire up the printer and get to work.
 

neil_w

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How large are we talking, what motors are you planning to fly on? What is your level of rocketry experience? There are commercially available electronics designed to handle this sort of thing. I am guessing an A motor is *not* the right approach.

(Welcome to the forum!)
 

tal041482

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How big, This is a great question, according to my simple math if we looking at appx 6ft tall, (I know huge right) Motors to fly on I have actually designed a way to use c,d,or e motors for the first stage depending on crazy I want to be (interchangeable tubes for holding engines) we are looking at using standard Estes rocket engines (at least for now) I have built quite a few home built rockets, I have used blow off tubes in the past, and they seem to work well for routing the gases from the engine up to "pop" the stage and keep my electronics (Altimeter, etc) safe from the hot gasses. I guess my biggest concern is stage 2 igniting early while the first stage is still attached and having a massive unsafe fireball careening though the air.
 
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How big, This is a great question, according to my simple math if we looking at appx 6ft tall, (I know huge right) Motors to fly on I have actually designed a way to use c,d,or e motors for the first stage depending on crazy I want to be (interchangeable tubes for holding engines) we are looking at using standard Estes rocket engines (at least for now) I have built quite a few home built rockets, I have used blow off tubes in the past, and they seem to work well for routing the gases from the engine up to "pop" the stage and keep my electronics (Altimeter, etc) safe from the hot gasses. I guess my biggest concern is stage 2 igniting early while the first stage is still attached and having a massive unsafe fireball careening though the air.
What is your certification level currently? Is it NAR or Tripoli? Are you a member of a NAR or Tripoli club?

These are not trick questions. If you are a NAR or Tripoli member, or if you are certified, you will already know the answers to what the regulatory (legal) requirements are for flying high powered rockets. If you are contemplating a 3D printed 6' tall rocket, it likely will require a motor or motors that require at least an L1 cert (160.1 - 640 Newton-seconds), if not L2 (640.1 - 5,120 Newton-seconds). It's going to be heavy. Doing this with standard Estes motors would likely require dozens of them. Clustering large quantities of BP motors is an art form. Staging them would be a nightmare. Estes E12 motors are the among the most CATO prone motors available. Clustering dozens of them could be very entertaining - and dangerous.

You mention needing to understand required thrust to weight ratios. Anyone flying 6' tall rockets likely has a certification and knows the minimum safe T/W ratio is 5:1, assuming maximum thrust is at ignition and not later in the burn.

You mention using an Arduino accelerometer. That's telling as well. Very few of us folks roll our own Arduino electronics. Not only do you have to do an electronics design and build out all of the components for the electronics, but you have to program and test the software. That's seriously challenging.

Your concern about the second stage igniting early while the first stage is attached is also telling. This is how all BP multi-stage rockets do upper stage ignitions (which is what you are contemplating using). On the other hand composite motor staging (which is likely what is needed here) is generally done by the altimeter sensing the change in acceleration OR using timers (old tech, these days) to fire a BP charge to separate the stages and THEN igniting the second stage.

The other members above are being circumspect in their responses to be polite (withholding judgement). I can sense their skepticism.

I'm going to be brutally blunt here. No offense, but your questions raise concerns that your dreams are getting ahead of your skills and knowledge. Building and flying large, staged rockets is among the most complex things to do in High Powered Rocketry. Please find a club in your area and join them. There will be lots of people in a club that can help guide you along the path to HPR. You cannot figure out everything you need to learn and do by asking questions on TRF.

You can find out about clubs in your area by doing research on the NAR (https://www.nar.org/) and Tripoli (https://www.tripoli.org/) websites.
 

tal041482

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What is your certification level currently? Is it NAR or Tripoli? Are you a member of a NAR or Tripoli club?

Hey Thanks for the Blunt response, I don't ask anyone to hold back if so i would not ask questions

My experience has been 90% kit rockets and nothing i have designed, With that said i am not a member of any clubs or have any certifications

These are not trick questions. If you are a NAR or Tripoli member, or if you are certified, you will already know the answers to what the regulatory (legal) requirements are for flying high powered rockets. If you are contemplating a 3D printed 6' tall rocket, it likely will require a motor or motors that require at least an L1 cert (160.1 - 640 Newton-seconds), if not L2 (640.1 - 5,120 Newton-seconds). It's going to be heavy. Doing this with standard Estes motors would likely require dozens of them. Clustering large quantities of BP motors is an art form. Staging them would be a nightmare. Estes E12 motors are the among the most CATO prone motors available. Clustering dozens of them could be very entertaining - and dangerous.

I have read the regulatory information regarding weight and thrust, with that said per the slicing algorithms for the rocket I fall at just under the max weight permitted for a non certified armature rocket (.983 LBS) the limit i see in our requirements is appx 1.2 lbs, However i may be under calculating weight as on a re-read it looks like the 1.2 lbs also is supposed to include propellent load,

The Reason i was asking about the thrust to weight ration was that i can always print the rocket to a smaller scale to keep under the laws if i need to, I have some experience with (3) rocket clusters and have designed a controller
that give me great reliability However it is still an estes rocket and i have a few late ignitions because well it happens, And yes i have seen and have experienced a par of rapid unscheduled disassembly from estes E motors.


You mention needing to understand required thrust to weight ratios. Anyone flying 6' tall rockets likely has a certification and knows the minimum safe T/W ratio is 5:1, assuming maximum thrust is at ignition and not later in the burn.

Like i said im here to learn and ask questions, Thanks for the ratio.

You mention using an Arduino accelerometer. That's telling as well. Very few of us folks roll our own Arduino electronics. Not only do you have to do an electronics design and build out all of the components for the electronics, but you have to program and test the software. That's seriously challenging.

This is actually my specialty, I build electronics all the time, but also one of the reasons i asked the questions I did not see a commercially available option for doing this.

Your concern about the second stage igniting early while the first stage is attached is also telling. This is how all BP multi-stage rockets do upper stage ignitions (which is what you are contemplating using). On the other hand composite motor staging (which is likely what is needed here) is generally done by the altimeter sensing the change in acceleration OR using timers (old tech, these days) to fire a BP charge to separate the stages and THEN igniting the second stage.

Yes I have only done the Estes style rockets where they are directly connected however due to the distance between the firsts and second stage makes direct ignition impossible, and that is the reason I am asking the question, in all honesty i am a minimum of 4 months from even considering flight, and with all of that being said i know i have a lot to learn on the higher power side of rocketry and truth be told not sure if i want it to be super high power or if changing the scale is the right path to go.

The other members above are being circumspect in their responses to be polite (withholding judgement). I can sense their skepticism.

I'm going to be brutally blunt here. No offense, but your questions raise concerns that your dreams are getting ahead of your skills and knowledge. Building and flying large, staged rockets is among the most complex things to do in High Powered Rocketry. Please find a club in your area and join them. There will be lots of people in a club that can help guide you along the path to HPR. You cannot figure out everything you need to learn and do by asking questions on TRF.

You can find out about clubs in your area by doing research on the NAR (https://www.nar.org/) and Tripoli (https://www.tripoli.org/) websites.
Thanks for the advice it is the reason i am here!
Thank you
 
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This is actually my specialty, I build electronics all the time, but also one of the reasons i asked the questions I did not see a commercially available option for doing this.
Here are the major vendors for altimeters. If you are good at electronics, including soldering, then Eggtimer is right up your alley.

Eggtimer - best bang for the buck (kits)
Missile Works - best ready made at a reasonable price
PerfectFlite Direct - StratologgerCF is the sweet spot (price, size, function), but no inventory for months.....
Featherweight Altimeters - Home - Solid, but higher priced
Altus Metrum - Cadillac features, Cadillac $$$
 

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Like i said im here to learn and ask questions, Thanks for the ratio.
Note that the 5:1 thrust ratio is only a rule of thumb. You are better off, with anything marginal, using a more accurate method where a simulator calculates the rail exit velocity, and you compare this to a speed that the rocket should be stable. A slow-accelerating rocket can still fly safely off a longer rail as long as it is fast enough when it clears the rail.

For a simulator I personally use RockSim, but OpenRocket is a free simulator available on the interweb. Many people use these for checking the designs before flight.
 
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the limit i see in our requirements is appx 1.2 lbs,
I'm curious how you come up with 1.2LB. A 6' Starship/Super Heavy comes to a scale diameter of 5.5". If you are printing with 1.5mm wall thickness (bare minimum) and 100% infill, that comes to 2.7 LB. That is without a parachute, recovery harness, any hardware you need to add plus electronics and battery. You could go with a lower infill, but then you have to understand how the matrix will handle the acceleration lest it shred.
 

tal041482

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I'm curious how you come up with 1.2LB. A 6' Starship/Super Heavy comes to a scale diameter of 5.5". If you are printing with 1.5mm wall thickness (bare minimum) and 100% infill, that comes to 2.7 LB. That is without a parachute, recovery harness, any hardware you need to add plus electronics and battery. You could go with a lower infill, but then you have to understand how the matrix will handle the acceleration lest it shred.

Thanks for that, I did just go back and look at my slicer settings and it looks like my infill was incorrect, Thanks for the double check on that. So back to the drawing board, or at least change the dimensions,

Just out of curiousity was your slicer able to do the entire thing in one shot? mine was a tedious process of each layer
 
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Thanks for that, I did just go back and look at my slicer settings and it looks like my infill was incorrect, Thanks for the double check on that. So back to the drawing board, or at least change the dimensions,

Just out of curiousity was your slicer able to do the entire thing in one shot? mine was a tedious process of each layer
I didn't use a slicer, I used math...
 
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Starship & Super Heavy are basically cylinders. I calculated the scale down ratio from their combined height to 6 feet and then used that to calculate the diameter. Calculate the volume of the cylinder then subtract the volume of a cylinder 3mm smaller. Multiply by the density of the material. I used ABS which is close to 1g/cm cubed. 2.7 lbs at 100% infill.
 
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