Comment by hrmtst93837
10 hours ago
Cheap sensors look impressive in demos but drift and calibration wreck repeatability unless you babysit launches so nobody in defense is sweating this yet.
10 hours ago
Cheap sensors look impressive in demos but drift and calibration wreck repeatability unless you babysit launches so nobody in defense is sweating this yet.
They should be sweating, because if the other side can fire 100 rockets for $10k that are close enough to not immediately and obviously be off target, and you don't know whether a more expensive one with actual explosives is hiding within that barrage, you now have 100 targets to try to intercept, and suddenly your costs have gone up dramatically while the other sides costs has barely moved.
100 rockets for $10k is not happening. The price floor is not dictated by the electronics (which did get cheaper), it's dictated by the rest of the system: propulsion, warheads, arming and safety, QA, traceability, climate and shelf life stability.
Take a look at Raytheon's manufacturing line: https://www.youtube.com/watch?v=kCCkVAHSzrc That's what it takes to have missiles that are nearly guaranteed to perform to specification every time. You can stockpile the packaged missiles in a non-climate-controlled shed for years, replenish them at sea while being showered with salt water, subject them to shock of a nearby blast while in a VLS, and they will still launch, go up to Mach 13, and catch an incoming ballistic missile nearly every time.
Sure, Iran's ballistic missiles are simpler than SM-3, but they are still subject to most of the constraints. They still need perfectly cast large size solid rocket motors that don't crack after being stored for a year, they need warheads that only go off when they are supposed to, they still need to trace every part for QA, etc. There's a vast gap, largely invisible to amateurs, between garage prototypes and stockpiled AURs.
> propulsion, warheads, arming and safety, QA, traceability, climate and shelf life stability.
The further down the list you go, the more optional the requirements get in a sufficiently dire scenario.
Shelf life doesn't matter if you are firing them as quickly as you can make them, especially if you actually can make them as quickly as you need them because they're so simple. QA and traceability may matter less if you just accept that you'll occasionally lose a launcher, and even occasionally have a stray missile land in someone's living room because that's better than having a non-stray Shahed in said living room.
In terms of safety, I bet it'll still beat "cutting open existing munitions and literally duct taping random other fuzes to them", which seems to be the bar for "good enough".
5 replies →
Without necessarily disagreeing with your point, the driving consideration for Raytheon's production line is arguably not reliability. It's being able to charge the customer for perceived reliability. It's very hard to know from the outside how much of it is theatre, even if earnestly arrived at. There are incentives for these things to be expensive.
1 reply →
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 forget. The US had napalm, helicopters, bombers, incredible logistics, cutting edge equipment of all sorts. Vietnam had a bunch of sticks in a hole covered in poop. Those sticks sent Americans crying home and we still get movies and games with them crying about how bad it was.
In war between great powers, yeah, high tech works because it's scary and civilians don't want to have that kind of stuff coming home. In a war where civilians are being targeted by great powers who terrorize them by blowing up schools and hospitals, a lot of people are thinking about how many weapons they can make to defend their home and for cheap. If America thinks an invasion is a good idea, they're going to be bringing their 50 million dollar tanks face to face with a few $100 toy rockets. And those toy rockets will be picking off tanks like fish in a barrel while a drone streams it in 4K live to the internet. I really do not think American who support current happenings are ready for the absolute mental torment they're going to endure if this continues.
13 replies →
TFA is literally about a $96 rocket.
> propulsion, warheads, arming and safety, QA, traceability, climate and shelf life stability.
You're entirely missing the point.
These do not need to be reliable for the scenario I hinted at. They also do not need to be armed.
They need to be large enough that if one of them is a higher quality rocket (not part of the $10k) that contains actual explosives, you have serious destruction on your hand. Maybe something that looks large enough for that will drive the cost up and we're talking $20k or even $100k instead of $10k.
The precise cost is largely irrelevant, as long as the total cost is a tiny fraction of the cost of a missile interception.
The point is you'd be multiplying the cost assymmetry by forcing a massively outsized response. Because if you don't try to intercept them, every future barrage will include a real rocket. If you do try to intercept them all, you'll be burning through massively expensive interceptors to take out a bunch of cheap toys.
If I was ever considering an insurgency, or a war, I'd be stocking up on vast quantities of toys, with the intent of making every radar constantly lit up by a number of possible threats.
3 replies →
> price floor is not dictated by the electronics (which did get cheaper), it's dictated by the rest of the system: propulsion, warheads, arming and safety, QA, traceability, climate and shelf life stability.
I wonder how much of that Ukraine is bothering with. Or Iran. Certainly Hezbollah are building down to a budget.
9 replies →
For a sub-minute flight the drift budget is actually pretty forgiving — a MEMS gyro drifts maybe 1-3 deg/sec, and if you're fusing with accelerometer data you really just need "which way is up" and "am I still pointed at the target." A $5 IMU can hold that for tens of seconds.
Where you're right is repeatability. Mil-spec works the same on launch 1 and launch 500 across temperature extremes. Consumer MEMS you'd need to characterize each unit individually — fine for a demo, impractical at any scale.
Good $3 MEMS gyros are about 100x better than that now - look at anything new made by Invensense in the past couple years. And their drift is pretty Gaussian-distributed, so the error scales as sqrt(n). If you combine 8+ of them on one board you can get about 5deg/hour stability...
Hm. Is it, though? If what you wanted to do was produce a large batch of calibrated IMUs, building a rig to do so wouldn't be an enormous undertaking.
Or do you mean to characterise the assembled vehicle?
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.
Visual SLAM on a rocket would be wild. The frame rates you'd need at those velocities are brutal though — feature tracking falls apart fast when your entire visual field is changing at hundreds of m/s. Drones are the sweet spot where camera-based nav really shines.
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.
Cheap sensors are the future ;) onboard ML can help with signals interpretation.
But do they drift enough to hit girls schools?
I think the problem sits in the white house, not in the sensors.
Oof
Ask Claude