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Comment by redgridtactical | Hacker News Reader

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 electronics and mil-spec capability keeps shrinking and this is a pretty stark demonstration of where that trend leads. A few years ago this would have required an IMU that cost more than this entire build. The democratization angle cuts both ways though - the same accessibility that makes this cool for hobbyists makes it genuinely concerning from a proliferation standpoint.

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> The gap between consumer electronics and mil-spec capability keeps shrinking

My friend's brother works in munitions and had, in his spare time, designed and prototyped a missile that could be built for about 10k. He pretty much was ignored by the contractor he works for.

Shockingly, as of a couple weeks ago, they are all hot and bothered to talk.

I wonder what could have possibly sparked that... lol

That tracks. The defense primes have zero incentive to make things cheaper — their business model is cost-plus. A guy building something for 10k in his garage is an existential threat to programs billing 500k per unit. Of course they ignored him until the geopolitical situation made it impossible to keep ignoring.

> That tracks. The defense primes have zero incentive to make things cheaper

Same in medical imaging industry.

Well, there are cheap portable ultrasound scanners and endoscopes.

True.

I was talking about those that are meant for hospitals. Was peripherally involved with a fledgling startup that was developing something cheap. Hospitals straightaway said noway.

They would be desirable in places with poor advanced imaging penetration like Brazil. Usually only the largest city in a state has this sort of imaging.

If you build a tool optimized for human destruction, you are feeding a system where violence is the default currency

We are heading to robotic wars where abilities and cost efficiency are the key factors. Like today drones in Ukraine war. Attack + defense + automation, + money + production

It's not really terribly new actually, in the past, rapid advances in consumer technology have enabled other sort of weapon guidance systems. For instance, the development of extremely compact television cameras available to consumers directly lead to the development of the Walleye television bomb. It happened when one nerdy guy was fucking around with his new camera and realized that he could automatically track track features in an analogue television signal using some quite basic analogue electronics. Point the camera into the general direction of the target and you can then "lock on" to some target feature and based on contrast it could tell how that feature was moving around in the image.

He implemented a 1D tracker in his garage, took it to work and showed people. A few years later these bombs are taking out bridges and even sometimes hitting moving trucks.

People made self-guided missiles with 1940s technology, in the 1940s. It can't be too much of a surprise if someone right now can make guided missiles in their garage with 2026 electronics. At this point the "guided" feature is trivial, the "missile" part is doable, and the weapon has probably become the tricky part.

Throwing an aside here that anyone interested in 1940s war technology must check out the old BBC documentary The Secret War (1977) which goes into depth on solving the engineering challenges of the war.

Well worth a watch. I think I watched it on Youtube.

I think the hard part was and will usually continue to be making the whole thing work effectively together with enough performance to actually work in practice. It's a lot of details across a lot of disciplines to get right.

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 restrictions on GPS prevent ballistic missiles, not MANPADs. Typical limits are 515 m/s and 18,000 meters (try using your phone's GPS on a commercial flight, it works fine near a window). Update rate is probably the biggest issue with GPS and MANPADs.

Are these chips so much better at calculating GPS position than general purpose CPUs or consumer FPGAs? Feels like a silly restrictions for anyone capable of building a ballistic missile. On the other hand it seems relatively computationally expensive to do a speed check every time for low energy devices.

What you are likely thinking of is the "selective availability" system, which intentionally provided slightly inaccurate data to civilian clients, while military receivers could decrypt the most accurate info. But this has not been used for many years now.

Other than that, GPS is a one-way system, it does not know you exist, how fast your receiver is moving or "give" different information to one client vs another.

Even if it did, this is essentially a toy and moving slower and lower than a general aviation plane.

It uses accelerometers and other sensors because they can be sampled and integrated hundreds of times a second. The $5 gps module is 9600 baud serial and provides one update/second (or maybe 5/sec depending on which part number you pick).

No, he's thinking of the "CoCom limits". It's built into the receiver.

There's a lot of room within those 18km/59000ft and 1000kts/1200mph limits.

Chinese GPS chips dont have those restrictions.

I even have 1 that can remove up to 8 active jamming signals.

Gotta love what you can buy for $20

It would be interesting to see if those are only for external sale vs restricted for sale within China.

If China allows those unrestricted chips to be sold internationally but not domestically it would be a strategic long-term decision, I would think. Destabilize the neighbors but not themselves.

The more likely reason is that their government has simply not gotten around to restricting it.

I mean, do you have the impression they are destabilizing anything with this (implying these GPS restrictions are actually needed)?

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

> A few years ago this would have required an IMU that cost more than this entire build.

Are you sure about this? MEMS IMUs have been popular and cheap for ~10-15 years.

More than the electronics, I would be curious about the performance of 3d-printed plastic parts on a rocket. Are they strong enough?

People have been doing 3d printed model rockets for a while now. With no payload they experience higher acceleration than this will.

3d printed PLA and spiral wound cardboard is generally fine for hobby rockets, until they start going supersonic - then you need metal.

I'm not sure the launch tube could withstand the heat of the rocket exhaust though. Although that might depend what it is printed with.

Owning a system designed for surface to air weapon carries life imprisonment any USA, without any intent for violence, just simple possession or conspiracy to possess[]. Doesn't even matter if you have an NFA stamp, there is no exception except if it's done with authorization and behalf of the government.

Merely having a device intended to guide the rocket is also the same penalty.

[] https://www.law.cornell.edu/uscode/text/18/2332g

Seems like the quick fix is to rebrand this from "MANPADS" to "anti-tank", right? Then it would just be a standard destructive device?

AI slop comment

Bingo. Against guidelines.

beep boop

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