Nano Rocket #1 : Hand Thrown with TTL Serial Communications

RE: Nano Rocket #1 : Hand Thrown with TTL Serial Communications

BigG — Fri, 08 May 2020 14:53:46 GMT

will have to think about how to process and display the data from the accelerometer (x,y,z) to try and come up with a single measure of acceleration as the rocket is launched, flying and hitting the ground. Anybody any ideas?

My suggestion is to start by making it simpler by first throwing it vertically up in the air with minimal trajectory. The data should then display the overarching effect of gravity as well as spin characteristics (depending on how you threw the device). You should measure time of travel separately. Also take multiple samples.

Then move to throwing it horizontally from a defined height. Here measure distance travelled before landing and time of travel etc.

Then finally throwing it in a trajectory as you've demonstrated.

Hopefully then you can start to paint a picture of acceleration in 3D.

RE: Nano Rocket #1 : Hand Thrown with TTL Serial Communications

shabaz — Tue, 05 May 2020 12:37:59 GMT

Hi Dubbie,

Very cool project : )

I've always thought it would be cool to strap sensors on model rockets, especially to see the differences caused by (say) smoother surfaces causing different flight patterns, but never got around to it. Very interesting to see your results.

RE: Nano Rocket #1 : Hand Thrown with TTL Serial Communications

beacon_dave — Tue, 21 Apr 2020 15:39:12 GMT

Should also be slightly more discreet than using a set of bathroom scales when conducting experiments in the elevators in the local department stores [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-e9164f80-f69e-4817-b354-4f6fd6cac0ef/contentimage_5F00_3.png:16:16]

RE: Nano Rocket #1 : Hand Thrown with TTL Serial Communications

jw0752 — Fri, 10 Apr 2020 14:01:11 GMT

Hi Dubbie,

I liked your experiment. If I understand the physics of your experiment your rocket should be under 1 G as it sits on the table. The acceleration that you give to it as you throw it should show up as a G reading above 1 G. As soon as it leaves your hand, whether it is still going up or falling back down, it should experience zero Gs as it will be in free fall. The only slight deviation would be any friction with the air that will produce a slight negative acceleration and any rotation that will also produce an acceleration that would show up as a G force to the sensors. As it hits the ground it will experience an elevated G force due to the rapid deceleration. It will be interesting to see how this relates to the data you have collected. If there is some way to integrate the sensor data over the flight time it might make more sense and if you can throw it in such a way that it doesn't rotate about any axis this will simplify the data set.

John

RE: Nano Rocket #1 : Hand Thrown with TTL Serial Communications

genebren — Fri, 10 Apr 2020 13:57:07 GMT

Nice little experiment. Hopefully you will figure out the mystery of data.

RE: Nano Rocket #1 : Hand Thrown with TTL Serial Communications

abrain — Fri, 10 Apr 2020 13:13:32 GMT

Nice one Dubbie!

One thing that might be interesting on the accelerometer data is to start off with looking at the magnitude of it all - something like the following in Excel:

=SQRT(POW(A1,2)+POW(B1,2)+POW(C1,2))

This is assuming that your x,y,z accelerations are in columns A, B and C and you want the "answer" in column D, and it's starting from row 1.

The minor problem with this is that it will give you the absolute magnitude - you should see a good initial spike as you launch, then another as it comes back to hit the ground with a bump!

I'm a little surprised at the start of the data - it looked to me that you had the device nice and flat on a table when you started, so I'd have expected 2 of the lines to be about 0g, and one at around 1g, but one of the channels seems to be at -0.5g, which is interesting - that must all come from it being at a slight angle on your bench.

100Hz sampling looks perfectly good enough, it looks like you've captured it bouncing as it hit the ground - a good throw too!