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$96 3D-printed rocket that recalculates its mid-air trajectory using a $5 sensor

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Re: $96 3D-printed rocket that recalculates its mid-air trajectory using a $5 sensor

#341

Post by 3abiton »

ralferoo wrote: post #238

I remember an anecdote our robotics lecturer told our university class in 1995, which was about how in the west we try to make expensive things that are the absolute best of technology and how the other side didn't have that luxury and relied on ingenuity. He described a cold war Russian missile they had somehow obtained and were tasked with trying to reverse engineer. Ostensibly, it was thought to be a heat seeking…

This is an interesting thought, as if I remember correctly, there was this theory that once something is known to be possible to discover, it only takes dedication to achieve it (George Dantzig as an example)

Re: $96 3D-printed rocket that recalculates its mid-air trajectory using a $5 sensor

#342

Post by rexpop »

NoMoreNicksLeft wrote: post #302
srean wrote: post #62

Earlier quoted context omitted.

They are using white phosphorus on populated areas in South Lebanon. That's as vile as one can get.

[flagged]

Reasonable people know to take your flippant tone for the colorful warning of a rotten, toxic brain.

Re: $96 3D-printed rocket that recalculates its mid-air trajectory using a $5 sensor

#344

Post by torginus »

the__alchemist wrote: post #201
torginus wrote: post #141

Earlier quoted context omitted.

I think MEMS gyroscopes and accelerometers used in consumer drones should be just about good enough to measure orientation and acceleration, and those are cheap and easy to get. You could integrate acceleration to get speed - the flight is short enough to make compounding errors easy to ignore. I think thanks to drones and RC hobbyists, there's a generally nice body of knowledge on how to get good enough data from co…

> You could integrate acceleration to get speed - the flight is short enough to make compounding errors easy to ignore. False, given how noisy MEMS IMUs are, and the accuracy required. Even Ring Laser Gyros drift quickly.

I did a bit of googling and this was the first result:

https://www.h4-lab.com/store/p/qmu102

This sensor has a 16G limit, which is well above what an amateur rocket cold and the compounding velocity error at 10G would be something like 0.0002 (m/s)/s. Which is way more than good enough, at least for short flights measured in minutes max.

Re: $96 3D-printed rocket that recalculates its mid-air trajectory using a $5 sensor

#345

Post by FergusArgyll »

redgridtactical wrote: post #13

The engineering is genuinely impressive for $96, but naming the repo "MANPADS-System-Launcher-and-Rocket" on GitHub is going to attract exactly the kind of attention you don't want. ITAR implications aside, the interesting part is the mid-flight trajectory recalculation on a $5 sensor. That's the same basic problem military guidance systems solve with hardware that costs thousands. The gap between consumer electronic…

beep boop

Re: $96 3D-printed rocket that recalculates its mid-air trajectory using a $5 sensor

#346

Post by jacquesm »

computerdork wrote: post #269
kdheiwns wrote: post #263

Earlier quoted context omitted.

If you think shelf life, QA, safety, blah blah blah matters when a rocket is 100 bucks, I have just three words: you will lose. The Ukraine war is being fought with a bunch of cheap toy style drones dropping grenades everywhere. The US got their bases blown to pieces across the Middle East by cheap drones that gently float through the air like a paper airplane in comparison to absolutely any missile. And let's not fo…

You have a point - cheap drones have changed warfare - but you might be simplifying the issue. As some warfare experts online have discussed, it isn't that cheap drones are the only weapon that is used in Ukraine (or warfare in general), it is one option in vast array of options based on the situation (although, agreed, it is taking on a much bigger significance). Look at the war in Iran. They did a pretty standard p…

Bombing stuff is relatively easy, holding territory is not.

Re: $96 3D-printed rocket that recalculates its mid-air trajectory using a $5 sensor

#347

Post by jacquesm »

mosura wrote: post #74
hrmtst93837 wrote: post #46

Earlier quoted context omitted.

[flagged]

For different definitions of cheap though. While the pure gyro/accelerometer stuff does suffer from major problems the improvements in SLAM using just cameras in the last 15 years are insane.

That's because for short term they are really good, for the longer term the drift is too large so you will need many layers of sensors with different characteristics.

Re: $96 3D-printed rocket that recalculates its mid-air trajectory using a $5 sensor

#348

Post by jacquesm »

torginus wrote: post #149
hrmtst93837 wrote: post #46

Earlier quoted context omitted.

[flagged]

You can calibrate any sensor, its just a manufacturing step, and while cheap ones may be inaccurate and drift over time, I'm pretty sure the good enough ones (which cost tens of dollars, not fractions of a dollar) are accurate enough to work for the seconds-to-minutes flight time of a rocket like this.

Seconds, yes. Minutes, not so much. Then you will need another layer.

Re: $96 3D-printed rocket that recalculates its mid-air trajectory using a $5 sensor

#350

Post by cozzyd »

shrubble wrote: post #69
redgridtactical wrote: post #13

The engineering is genuinely impressive for $96, but naming the repo "MANPADS-System-Launcher-and-Rocket" on GitHub is going to attract exactly the kind of attention you don't want. ITAR implications aside, the interesting part is the mid-flight trajectory recalculation on a $5 sensor. That's the same basic problem military guidance systems solve with hardware that costs thousands. The gap between consumer electronic…

Consumer GPS chips are specifically nerfed for using them in rockets; they give erroneous readings on purpose if altitude is above a certain height and/or if speeds exceed a certain speed. That’s likely why the mid-course correction software uses other methods.

The altitude limit by itself is not a problem (just make sure you fix the kinematic model). Consumer u-blox chips work great in balloons
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