New enthusiast here

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Joshua F Thomas

Well-Known Member
Joined
Jun 4, 2019
Messages
664
Reaction score
342
Hello all!

I'm a physics/chemistry double major student at a university in Connecticut. I've been a spaceflight enthusiast for a long time, and decided to explore model rocketry this summer - lighter class load gives me more free time.

I'm starting with a small Estes rocket to become familiar with how everything works, and have connected with a local group in my area, so I feel like I'm off to a good start.

I've also been learning how to build microcontrollers with Arduino. I'd like to be able to combine these two things and send up an Arduino with a pressure sensor for use as an altimeter, so I can get some very rough rocket performance data. I'm sure there are already pre-built things for this, but I'd like to build this myself.

My questions are:

1) How are payloads usually mounted in model rockets?
2) How much mass can I launch on a given rocket, assuming I know the mass of the rocket and the particular engine(s)?

Any/all advice is appreciated. Thanks in advance!

-Joshua
 
Hi Joshua,

Welcome to TRF...

To answer your questions:

1) There are a number of ways that payloads are mounted in model rockets, some are mounted externally (like the 808 cameras used for look down video), most are internal. Some are loose inside the bays, some are simply cushioned with wraps of foam or wads of paper, others are firmly fixed to "sleds". Some are simply allowed to freefall (think candy) or parachute down (think army men and GI Joe figures). It depends on the type of payload being launched.

2) There's no hard and fast rule. Best idea is to create a sim of your rocket using a program such as OpenRocket (available for free) or RockSim (a paid program from Apogee Components), and run it to see what you can do.
 
Welcome!
A good rule of thumb is a 5:1 thrust to weight ratio. ThustCurve is a real simple on line calculator where you put in some basic parameters and will yield similar results to any of the programs mentioned above.
 
Thank you! I will check out these resources.

For electronics I would like to make sure they aren't damaged in on launch or landing, so the 'sled' option sounds like a good one. Are there examples of these I might be able to look at?
 
Welcome to the hobby and TRF, Joshua.
If you've hooked up with the CATO club in Connecticut, you'll have plenty of brains to pick for the information and guidance you are looking for.
I wish you well in your designs.
 
Welcome! I'm a chemistry professor at URI.

There are some great rocketry clubs in New England. Check out www.catorockets.org and www.rimra.org. RIMRA just had a launch last weekend, and CATO is planning to fly this weekend.

I bought an Arduino kit last year and have thought about building a microcontroller like you are talking about. I haven't gotten around to it yet, but several people here on TRF have posted similar builds. Just search around here and you'll see lots of cool stuff that people have tried.

Hope to see you at a launch sometime,

Brenton
 
You've picked a great hobby to take an interest in! Welcome to the forum. As you've already stated, before you get too far down in the weeds, buy an estes launch set and go fly. Keep it simple at first.

Almost every question you can think to ask, and many that you won't think to ask, are answered here: https://www.amazon.com/Handbook-Mod...tine+rocketry&qid=1560441152&s=gateway&sr=8-2

Put it on your Christmas list. ;)
 
Hi Joshua- I’m in CT as well. I’ll be at the CATO launch on Saturday and have some experience with altimeters too. I would recommend the Bosch Bmp388, a great sensor and there are some easy Arduino libraries and tutorials out there. Ex:

https://learn.adafruit.com/adafruit-bmp388/arduino

Our code is in C but it might still be useful for reference:

https://github.com/flightsketch/firmware

What rocket did you choose? An Arduino nano and small lipo should fit in a wide range of low/mid power models.

Fly often and ask many questions as you can, this group is an invaluable resource!

-Russ
 
Hi Joshua- I’m in CT as well. I’ll be at the CATO launch on Saturday and have some experience with altimeters too. I would recommend the Bosch Bmp388, a great sensor and there are some easy Arduino libraries and tutorials out there. Ex:

https://learn.adafruit.com/adafruit-bmp388/arduino

Our code is in C but it might still be useful for reference:

https://github.com/flightsketch/firmware

What rocket did you choose? An Arduino nano and small lipo should fit in a wide range of low/mid power models.

Fly often and ask many questions as you can, this group is an invaluable resource!

-Russ

Hello Russ! Looking forward to meeting you at the launch tomorrow!

I have a Bosch BMP280 board from adafruit, and have got it up and running for pressure logging. Will be adding an SD card board for logging.

I have the original Arduino - I bought the starter kit. I'd like to be able to use it, if possible.

See you soon!
-Joshua
 
Welcome Joshua,

It sounds like we have similar interests. I've been flying microcontrollers in my rockets for 3 or 4 years now. Here's a photo of how I mounted a recent project. For this one, I've been experimenting with a NEO 6M GPS module. My preferred microcontroller is the Adafruit Adalogger because it includes the SD card slot right on the board, saving space, wiring, and weight. It can be powered directly from a small LiPo battery.

To mount this experiment, I cut a piece of 1/4 inch balsa the exact size of my payload bay (BT70 in this case). I applied a couple coats of sealer and sanded it lightly to remove all the fuzz from the balsa. Then I just used the adhesive backing on the breadboard to mount it to the balsa. Since it's a perfect fit in my payload, it won't move around much. Since the connections to the GPS module were simple and to save weight, I removed the power rails from both sides of the breadboard. This has worked very well for my test flights and I've had some very good results. Although it's not shown in the photo, a 500 mAh LiPo is taped to the opposite side of the balsa sheet. It will run this setup for 5 or 6 hours.

IMG_0394.JPG

A couple of others have mentioned simulating the rocket design and I think this is a good idea. You can weigh the assembled payload and then enter it into the simulation as a mass object. I've used both OpenRocket and RockSim and they are very helpful in characterizing the performance of your rocket/payload with a variety of different motors.

Good luck.
--MARK

NAR 65148, L1
 
Welcome Joshua,

It sounds like we have similar interests. I've been flying microcontrollers in my rockets for 3 or 4 years now.

Mark, much thanks for your post. I've been looking at a tube rocket kit based on the BT70 for my second rocket, and your ideas will help me tremendously.

I had indeed found OpenRockets and have been playing around in it. Amusingly my experience with Kerbal Space Program applied immediately, about knowing how to balance center of gravity and center of mass to keep the rocket nose-up!

-Joshua
 
Back
Top