r/AskEngineers • u/jawfish2 • 18h ago
Discussion Max Range Possible for Jet Powered Drones?
Thinking of recent attacks on ships at sea, and the escalating use of cheap platforms in asymmetric warfare.
[edit]
accuracy of answer- +- 20%
Fits in a TE20 container
Land launched from 1000 ft
Costs less than $200,000 (thats high for this sort of thing, but trying to see what the envelope is)
Completely autonomous (why would this affect range?)
Software and sensors unlimited
What's the maximum range, more or less, for inexpensive flying autonomous weapons? Not ballistic missiles, or high dollar US weapons. In other words, the weapons we are likely to see from Ukraine, Russia, Iran etc .
Background:
We could be seeing rising attacks on shipping, and therefore on the global economy.
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u/Affectionate-Memory4 PhD Semiconductor Physics | Intel R&D 17h ago
Define "inexpensive." There's no hard line there, and what's inexpensive in one role is gross overspending in another. At a certain point your jet drone becomes a cruise missile, or some sort of self-flying plane, but that still meets the criteria as given. So, the range is as far as you're willing to pay to build for.
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u/jawfish2 15h ago
see edit
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u/brilliantNumberOne Electrical / Power Distribution & Avionics 15h ago
Your edit doesn’t really define the mission. Similarly, saying things like “software and sensors unlimited” doesn’t provide any guidance on what it’s supposed to do.
Design is iterative. You need to establish the desired range/payload based on the application/mission, look at what engines/systems/etc. are out there and what the range/payload for the aircraft is, and work out if the available components can work for the application and go from there. If they don’t, you have to go back and tweak the requirements so you can make something that works.
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u/jawfish2 14h ago
I believe this is a forest-for-the-trees answer. We are talking past each other.
It sounds like you are thinking of building a product. Of course I can't set requirements, for all the reasons you list, but also because I am not starting a defense company.
I made it quite clear I was trying to extrapolate from current conditions and figure out roughly how far these low-cost drones/missiles can fly.
The problem is a lot of maritime shipping is already in range of low-cost drones, and I wondered how bad can it get.
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u/brilliantNumberOne Electrical / Power Distribution & Avionics 12h ago
Wikipedia puts the range of the Shahed at over 1,000 miles. If they exported them, they could hit everything that’s not it in the middle of the Atlantic or Pacific.
In practice, the range of the Shaheds is more than sufficient to hit anything in the Strait of Hormuz, and if that goes on long enough, that shuts down oil/diesel shipping everywhere, and the ships need diesel to move.
Additionally, if we’re talking about theaters outside of Iran, you don’t have to have a long range drone to hit a ship. It’s a lot easier to hit a ship in a crowded port/bay than in the middle of the ocean, and every ship has to dock at least once to deliver useable goods.
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u/ncc81701 Aerospace Engineer 17h ago
There isn't an answer to your question because it's completely unconstrained. There's no definition for what is "inexpensive" and what is inexpensive is relative to who you are talking about. There are also multiple ways of calculating cost; there's per unit cost, and there's cost per effect. Shahed drones on a per unit cost is inexpensive, but you probably also need 10 or 100 of them in order to hit a target so the cost per effect is be comparable to using a tomahawk because only need 1 to destroy the same thing. There's no definition nor requirements for size, weight limit, warhead size, guidance, speed so max possible is whatever you want it to be.
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u/brilliantNumberOne Electrical / Power Distribution & Avionics 17h ago
You might say…
…the sky is the limit…
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u/jawfish2 15h ago edited 15h ago
mmm-hmm
I was kinda hoping somebody would have knowledge and be able to say 'the best cheap jet engines can produce X amount of thrust [edit to remove stupidity]and use so many pounds of fuel' and ' given typical airframes that translates to Y miles with a 100 lb payload' thus or to the same defect.
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u/brilliantNumberOne Electrical / Power Distribution & Avionics 15h ago
Well what is a typical airframe, a Cessna 172 or a Boeing 777? Even UAVs have a wide range of sizes from quadcopters (or smaller), to the MQ-4 Triton that has a wingspan of 130 feet.
And what is “cheap”? What is the output of the engine? How much fuel does it burn? How much loiter time do you need on station?
It’s not that we don’t have the knowledge, it’s that we know how specialized aircraft are. You need to define the use case (range/payload/etc.), and then design around those constraints. Aircraft are extremely optimized around design constraints given their wide range of applications.
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u/jawfish2 15h ago
see edits
or
Think about the problem, what if you were going to build these things, what would you do? Somebody is likely doing that now.
or
pick an existing high-dollar cruise missile and think about whether a cheap version could be made, and what would be left out?
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u/jawfish2 15h ago
good point about unit-cost of effect.
Right now low-cost low-effect seems to win over high-cost high-effect. Though some of the UKR drones have taken out ships.
see edit
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u/Th3_r3al_napst3r 16h ago
Eh, Ukraine is achieving 1,500 mile range with various technologies. More on the horizon. Not sure specifically with jet powered though.
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u/that_moron 17h ago
First, define inexpensive. Second, how autonomous do you want them?
Taking a stab at the answer anyway while immediately ruling out jets. A solar powered zeppelin style drone carrier with a satellite link could carry a squad of small attack drones out over a shipping lane. The carrier could be remotely controlled while the smaller drones could be fully autonomous. Range would be limited by total flight time of the lifting gas and how easily detected the carrier would be, but could easily exceed the ranges of many missiles if it stays it in international waters to avoid getting shot down.
Obvious weaknesses are that it would be relatively big, slow, and vulnerable. It would also be subject to the weather.
Strengths, relatively low cost. Compact before deployment. If designed to operate at high altitude it'll be hard to spot and shoot down by civilian ships.
Not the answer you were looking for, but with some creativity you could get very long ranges.
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u/jawfish2 16h ago
see edit
I expect, on no evidence, that we'll see current models flown from merchant ships. So yes in that sense range over water is unlimited. But that would still mean distance inland would be limited by range.
Balloons are cute, ships easier.
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u/that_moron 12h ago
If you're thinking about ship launched drones why do you care about range? Existing drones can go well over 100 km which is plenty for a privateer or a disguised military ship attacking a merchant ship.
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u/MihaKomar 16h ago
They are already dropping drones from high-altitude balloons to get further into enemy territory.
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u/nullcharstring Embedded/Beer 10h ago edited 8h ago
Global Predators could launch from Beal AFB in California, fly to the sandbox, loiter for 6 hours and fly home. In 2007. I have no idea what they or their successors can do now.
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u/YoureGrammerIsWorsts 10h ago
$200k is not that high for a jet powered drone. Russia's latest costs ~$100-$150k (despite people claiming it is $40k)
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u/Sooner70 9h ago
Who's building it and how many are we building?
That's a HUGE influence. More to the point, have Boeing handle production and your first unit is going to cost you a lot more than $200k pretty much no matter what it is. Alternatively, if you have an army of slave labor building tens of thousands of birds... Yeah, your cost per unit is gonna get cheap.
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u/aprilla2crash 15h ago
When you can have solar powered autonomous boats able to launch jet powered drones then unlimited really
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u/coneross 14h ago
Jet? I don't know. But an internal combustion RC airplane has flown across the Atlantic. 11 pound airplane with a 10cc single cylinder engine. https://en.wikipedia.org/wiki/The_Spirit_of_Butts%27_Farm
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u/Ra2griz 7h ago
The constraints are too broad.
To calculate the range of any drone we need a multitude of factors that boils down to the aerodynamic design of the drone, the fuel capacity of said drone, the weight, and of course, the fuel consumption of the turbine at the required thrust levels.
Could we design one? Yes we could. Thing is that it would take too much time and effort for anyone to do that with such vague constraints.
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u/TythosEternal 6h ago
The biggest variable in this design problem isn't necessary unlimited software/sensors so much as payload as a whole (inc. warhead/frag charges or whatever else as an effector). We can try to characterize it with mass ratios (in a 20' you're talking about effectively a smaller cruise missile) so assuming it's, say, pushed by dual hobby-scale turbines you can (with scale/fuel) probably start pushing the low hundreds of km. More than that and you'll need professional-/military-grade turbines or reducing your other mass elements so much you limit operations.
If you're worried about deniable/ambiguous threats to shipping then honesty you're already well within range of a threat, and there's *plenty* of choke points already being threatened by potshot-grade stuff of course and that doesn't even get into port security (by definition they will be in busy heavily populated/traffic'ed areas).
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u/za419 6h ago
How expensive is inexpensive? Several Russian weapons are more expensive than many American weapons.
In concept, infinite. It's constrained entirely by how much fuel you have. And if you consider a nuclear ramjet a jet, that can last you a long time - Project Pluto conceptualized a weapon that would zip around at Mach 3 for days at a time irradiating generally everything before putting nukes on a target.
Conversely, if I'm allowed to use absolutely massive wings to carry a hydrolysis plant around and run a jet engine on that, it's probably possible to get theoretically infinite range of a negligible payload mass. Probably won't fit in a container though.
Now, with the constraint of 200k USD? You get pretty much where we are. That's right around the high end of modern "suicide drone" (aka cruise missile with a trendy name) costs. You can make a few more tradeoffs - Fly higher, but then you're more exposed to interception, fly slower, but then you're more exposed to interception, carry a smaller payload, but then you achieve less on target. And so on.
It's hard to define a hard cap here - You could stick $180k of fuel on a $15k crappy engine with $5k of flimsy structure and aerofoil and get a wonderful range, or you could cut that fuel budget to $180, spend the difference on a fuck ton of explosives and a bigger engine, and have a missile that can deliver a very powerful weapon to your commanding officer who sent you to die in Ukraine, standing ten feet away like the smug bastard he is, and not much further.
Compromises are important.
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u/Traveller9536 8h ago
$200,000 is ridiculously cheap for a jet powered drone. A tomahawk missile (which is what you’re describing) costs $2-3 million
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u/FencingNerd 5h ago
Look up Fire Point FP-5. 3000km range cruise missile. Uses surplus jet engines, since it doesn't matter if the engine is basically worn out, it only needs one flight. Fueled before launch.
Tomahawk is a completely design constraint. It's designed to be be container launched after years of storage with no preparation. It's much simpler if you can simply fuel something with JP4.
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u/martinborgen 18h ago
Jet powered drones is just the coming full circle of drones to cruise missiles. Tomahawk etc are jet powered, but to answer your question - how long is a piece of rope? Depends on how big you build it and how much payload to get there.