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My first thought was, "why not a pulsejet? Didn't that crazy guy in NZ use one to build a DIY cruise missile some years back?" Well, it turns out pulsejets are

by _iyig 7y ago

My first thought was, "why not a pulsejet? Didn't that crazy guy in NZ use one to build a DIY cruise missile some years back?" Well, it turns out pulsejets are horrendously inefficient [0]. If the missiles were fired from northern Yemen per the article's map, there's no way a pulsejet could have even gotten close to its target with the same load of fuel. I'm led to wonder whether piston engines could've made the trip, and whether Saudi air defense could've shot such a (slower) drone down. Giant-scale RC plane engines exist... anyone know how big these have to get before export controls kick in? EDIT: forgot source link. [0] https://aardvark.co.nz/pjet/jet_efficiency1.shtml https://aardvark.co.nz/pjet/jet_efficiency1.shtml

rdtsc 7y ago
I think the idea is that it wasn't a complete clean room Yemeni design, but rather an altered Iranian design, which in turn copied from a Soviet missile: https://en.wikipedia.org/wiki/Kh-55 https://en.wikipedia.org/wiki/Kh-55 The engine was switched from a more efficient turbofan to a turbojet TJ100. But switching to a piston and propeller engine might have been to much of a change and would have require a complete redesign.
- caf 7y ago
  The article is concluding that the Quds-1 is not an altered Soumar (which is the missile based on the KH-55) - the list of differences up to and including the significantly smaller diameter and different engine make that unlikely. Rather it is mentioned that TJ100-alike engines are used in Iran's drone program (as distinct from cruise missiles), and this raises the possibility that the Quds-1 is a derivative of one of those.
  - rdtsc 7y ago
    But the general design class is the same, it even confused the Saudis it was the same rocket. I guess I was trying to say is if it was designed from scratch with a piston engine it would look very different. But because there were already similar designs and models they had access to, it made sense to stick with that same general class of rockets.
- Stevvo 7y ago
  The same company that produces the TJ100 also produces the TP100; it's pretty much the same engine but a turboprop instead of a jet, it's the only viable propeller powered alternative I can see as piston engines are simply too heavy. You get a lot let thrust with a lot more weight on something like a Rotax 912, commonly used in drones.
ryacko 7y ago
Not an expert (member of a community of armchair generals actually), but uprating an engine will increase power density at the expense of durability and some fuel efficiency. They could build planes, attach an uprated car or motorcycle engine to the front, and point it at the destination. It might have a 90% success rate, which is sufficient.
- jacquesm 7y ago
  Where did that 90% come from?

by _iyig 7y ago

rdtsc 7y ago

I think the idea is that it wasn't a complete clean room Yemeni design, but rather an altered Iranian design, which in turn copied from a Soviet missile: https://en.wikipedia.org/wiki/Kh-55 https://en.wikipedia.org/wiki/Kh-55 The engine was switched from a more efficient turbofan to a turbojet TJ100. But switching to a piston and propeller engine might have been to much of a change and would have require a complete redesign.

caf 7y ago
The article is concluding that the Quds-1 is not an altered Soumar (which is the missile based on the KH-55) - the list of differences up to and including the significantly smaller diameter and different engine make that unlikely. Rather it is mentioned that TJ100-alike engines are used in Iran's drone program (as distinct from cruise missiles), and this raises the possibility that the Quds-1 is a derivative of one of those.
- rdtsc 7y ago
  But the general design class is the same, it even confused the Saudis it was the same rocket. I guess I was trying to say is if it was designed from scratch with a piston engine it would look very different. But because there were already similar designs and models they had access to, it made sense to stick with that same general class of rockets.
Stevvo 7y ago
The same company that produces the TJ100 also produces the TP100; it's pretty much the same engine but a turboprop instead of a jet, it's the only viable propeller powered alternative I can see as piston engines are simply too heavy. You get a lot let thrust with a lot more weight on something like a Rotax 912, commonly used in drones.

ryacko 7y ago

Not an expert (member of a community of armchair generals actually), but uprating an engine will increase power density at the expense of durability and some fuel efficiency. They could build planes, attach an uprated car or motorcycle engine to the front, and point it at the destination. It might have a 90% success rate, which is sufficient.

jacquesm 7y ago
Where did that 90% come from?