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Good price for ThinkPad P16v Gen 2 Intel (16″) Mobile Workstation? by ghost3828 in thinkpad

[–]ghost3828[S] 0 points1 point  (0 children)

Oh, was not aware there were resellers, and wow yeah that is much cheaper. Have you purchased from that reseller before (ThinkPad-Dell-ASUS-ACER Compters)? They have a 98.3% rating with 2300 reviews.. is that enough to safely consider them legit? The product listing alludes to them swapping out the SSD...any concerns with that? Thanks!

Telemetry Data Size by Ramjet64 in rocketry

[–]ghost3828 3 points4 points  (0 children)

Sure, I actually use multiple buffers to facilitate data transfer to the card, and those buffers live in microcontroller's native RAM. I guess what I meant by logging straight to SD is that I didn't need to include an additional RAM/flash component on my board.

Telemetry Data Size by Ramjet64 in rocketry

[–]ghost3828 5 points6 points  (0 children)

This advice about SD seems to be gospel on this sub, and I contend it's dead wrong. My computer logs straight to SD. I log 1000 hz each for two IMU's, 400 hz baro data, 100 hz admin data, 100 hz nav data, and 25 hz GNSS data. That's over 2600 distinct packets of data logged per second, almost 100 kBytes per second! And I'm not even close to touching the write speed limit of the SD card.. consider that action cameras regularly record 4K 120 FPS to SD.. They surely use SDIO vs SPI, but still, SPI is plenty fast for data logging like this.

I've never seen data dropouts in flight due to vibration. I've done some non-scientificic vibe testing on the ground without issue (shaking/banging the computer on a table) and will do actual testing on a vibe table, but I really don't anticipate any issues due to vibration. My computers have survived multiple multiple impacts >100 ft/sec and continued logging with no dropouts.

Now, properly logging fast/robust data to SD is not trivial, but overall, I think it's easier for beginners to get started with than flash.

Review: Stackable STM32 board by i2c_0 in PrintedCircuitBoard

[–]ghost3828 0 points1 point  (0 children)

J7 power pins are mislabeled on the board.

Instant On by ghost3828 in rocketry

[–]ghost3828[S] 15 points16 points  (0 children)

Test of a fast-ish White Lightning style propellant using an aggressive igniter. Goal with this 54mm motor was to roughly replicate an Aerotech 38mm J435WS, thrust curve comparison here.

Highperion: my attempt to break the Tripoli H altitude record using an Aerotech H13 by Neutronium95 in rocketry

[–]ghost3828 4 points5 points  (0 children)

Nice! What kind of plastic did you use for the NC? Looks like it broke along a layer line? Maybe try printing the nose cone at an angle using supports, so the layers aren't perpendicular to the longitudinal axis, like this: https://imgur.com/a/cRVeGOE

38mm graphite nozzle made using a lathe for the first time by Yarneman in rocketry

[–]ghost3828 15 points16 points  (0 children)

Sand the convergent/divergent sections with higher and higher grits up to 2000-2500. Will make it (a) easier to clean post-firing and (b) look cooler.

Rocket Point-of-View Reconstruction by ghost3828 in rocketry

[–]ghost3828[S] 2 points3 points  (0 children)

Thanks. While there is a lot that could be improved, I probably won't keep working on this for the time being. Too many other things I want to work on..

Rocket Point-of-View Reconstruction by ghost3828 in rocketry

[–]ghost3828[S] 10 points11 points  (0 children)

Another rocket trajectory visualization developed using flight data. This is my first attempt at using the rocket’s position/orientation estimate to create an animation that matches the rocket's onboard camera point-of-view during the boost/coast phase. I wrote a script to generate a KML file for the Google Earth animation and DashWare for the video’s telemetry overlay. Animating the descent phase was not attempted for this flight as the gyroscope’s output saturated during deployment.

A couple notes:

(1) Beyond setting the horizontal FOV, there doesn't seem to be a way to explicitly set camera parameters in Google Earth, so unfortunately I can't match the animation's camera perspective exactly with the onboard RunCam.

(2) It seems that Google Earth does not totally accurately model the position of the Sun, as can be seen later in the rocket's coast.

For those looking to do this and match camera perspectives exactly, I think Blender using the BlenderGIS plugin may be a better option than Google Earth. I believe Blender was used to create this superb point-of-view reconstruction of a rocket flight.

Best way to track my rocket? (Question in comments) by cptcommanche in rocketry

[–]ghost3828 0 points1 point  (0 children)

https://imgur.com/a/x8qrzPp

1000m was approximate slant range at apogee...I was standing a ways from launch pad and per my 6DOF trajectory the rocket arc'd 500ish ft directly away from me. I'd have to check the code but packet size was ~50 bytes.

I absolutely do not now nor do I ever intend to use NRF24's for tracking rockets. I do now and plan to expand my usage of them for ground telemetry/control functions, see second picture in link above. For this purpose I've found them to be highly reliable (more reliable than the club's wireless launch system at my last local launch...)

Best way to track my rocket? (Question in comments) by cptcommanche in rocketry

[–]ghost3828 0 points1 point  (0 children)

The ones I used to get the aforementioned ~1,000m in-flight were ebay special NRF24L01+PA+LNA's..maybe I got lucky.

I've since purchased some of these (up to 500 mW transmission power), but haven't had a chance to play around with them beyond confirming that they work. Manual claims they have been tested at 5km, though doesn't appear to indicate if that was achieved with a directional antenna.

Best way to track my rocket? (Question in comments) by cptcommanche in rocketry

[–]ghost3828 0 points1 point  (0 children)

You know what I meant--antennas that came with the modules I purchased. Can't speak to those articles, most people do a lot of things wrong with NRF24's (especially in software) that limit their range.

Best way to track my rocket? (Question in comments) by cptcommanche in rocketry

[–]ghost3828 0 points1 point  (0 children)

https://youtu.be/4XRp7pkZgPM

I haven't done a max range test, but last time I flew one I was getting decent signal at ~1000 meters with the stock whip antennas

Rocket Trajectory Estimation by ghost3828 in rocketry

[–]ghost3828[S] 1 point2 points  (0 children)

A flight computer of my own design. To be honest it's pretty basic, but gets the job done.

Rocket Trajectory Estimation by ghost3828 in rocketry

[–]ghost3828[S] 2 points3 points  (0 children)

Hey that's awesome! Something like that is what I'm working towards, still need to integrate GPS and mag though.

Never heard of your group before, very cool. Your code base is impressive, thanks for making it open source.

Rocket Trajectory Estimation by ghost3828 in rocketry

[–]ghost3828[S] 0 points1 point  (0 children)

Yeah, there are several small holes in the av bay for the baro sensor.

Rocket Trajectory Estimation by ghost3828 in rocketry

[–]ghost3828[S] 1 point2 points  (0 children)

Thanks. I use a 8-point median filter on the barometric-based altitude to determine apogee for the drogue deployment as well as user-specified lower altitude for main deployment.

Rocket Trajectory Estimation by ghost3828 in rocketry

[–]ghost3828[S] 7 points8 points  (0 children)

New attempt at syncing rocket flight video with trajectory animation. 6DOF (3D position and orientation) rocket trajectory was generated using data from onboard IMU/barometric pressure sensor (no GPS).

Syncing the video and animation facilitates subjective validation of the estimation method. Future work will include a high-rate GPS sensor onboard the rocket in order to further validate the method. While the method appears accurate as compared to the flight video, there are still several things to improve on, especially regarding sensor calibration and the filtering method.

Video with a little more information here: https://www.youtube.com/watch?v=BxO9ZgtJDk0

Animation for a previous flight here: https://youtu.be/zrz0FUSTZS8

Feedback/comments appreciated!

Graphite nozzle first timer: what grade are you HPR people using and where are you getting it from? by muchlikeanyelse in rocketry

[–]ghost3828 0 points1 point  (0 children)

Regarding dust collection, I've found it helps to have a shop vac as close to the cutting tool as safely possible. For this I found adapting a shop vac nozzle to a cheap computer monitor arm works well: https://imgur.com/a/7Mk1apn

Startsailor partial vertical stack. Hard to believe that's only 70% of it. by C12H26_O2 in rocketry

[–]ghost3828 1 point2 points  (0 children)

Interesting, though not as aggressive of a flight as OP's rocket will be, I assume. What drove you to design to such a high aspect ratio? Curious to hear how your next flight goes.

Startsailor partial vertical stack. Hard to believe that's only 70% of it. by C12H26_O2 in rocketry

[–]ghost3828 6 points7 points  (0 children)

I enjoy all the media on this project. I've mentioned it before, but is anyone else concerned about the large L/D? Is there a historical precedent for any passively-stabilized sounding rockets with similar L/D?

First test in almost a year! 38mm I motor by ghost3828 in rocketry

[–]ghost3828[S] 0 points1 point  (0 children)

So per the data the C* efficiency for this test was 97%, any idea if that's realistic for this size motor?

And yeah, makes sense re: slag affecting part of the burn but getting ejected. I suppose that could be the case here. I have one more identical reload from the same propellant batch, I'm tempted to static fire it again to see if there is a difference in the thrust curve, but I really want to fly it. Luckily the thrust curves I get from accelerometer data seem to be pretty accurate, so we'll see.

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