High-resolution photographs of the airframe for North Korea’s Pukguksong submarine-launched ballistic missile have a surprise. The airframe appears be wound filament, not the simple metal airframes we’ve seen on North Korea’s space launchers. That opens up a lot of possibilities for North Korea — and ticks off an important requirement for North Korea to build a solid-fueled ICBM in the future.
In all the showing off of their machine tools we haven’t seen any that could do this job I take it?
None I’ve seen, but I haven’t put the same energy into finding filament-winding machines as I have elsewhere. Then again, I’m not sure this application demands that sort of technology.
Imitation is the sincerest form of flattery. As I noted when the Pukguksong SLBM first appeared, it was no coincidence that the configuration looked a lot like our Polaris 1, and the name Pukguksong translates as “polaris”. This appears to be one more layer of inspiration.
All respect to the fine arguments and the nice catch by Tal Inbar; this indicates that the parade mockups may include some with wound filament cases. It does not preclude constructing mockups with sections of fiberglass piping with various other fittings applied. I do recall seeing filament winding equipment on the ITAR/MTCR shopping list of ‘no’.
The surface roughness on that parade article looks a big rough. I can only speak to my experiences with large hybrids but we were able to obtain complete immersion of the windings and ground the surface smooth, and still have a less than horrible ‘dry mass’. What happens to the aerodynamics with a surface finish like that?
Andy – its all turbulent surface flow downstream of the nosetip and significant radius expansions on stage adapters. I don’t expect to see a noticeable skin drag term difference from surface finishes. Note when NASA stopped painting Shuttle External tanks they gained payload from shedding the paint mass due to the fact the surface roughness was relatively unimportant.
Amateur rocketry people doing hand fiber wrapping have done anything from add a fabric layer over the unidirectional yarn wrap to smooth it out, to using tows rather than yarn, to leaving it rough like that. No discernible differences in drag…
How much does Iran use wound filament airframes for its missiles? Is there a source where I can find more information about Iranian missile airframe types? Wound filaments are a recent development for North Korea but how long has Iran used wound filaments?
I agree. This is right behind behind the interstage cone – could it be just a flexible cover over an open interstage truss? Built light to blow out at staging?
Incidentally; given the obvious explosion-like flaring on canister ejection, I do not assess the Pukguksong-2 ejection as a ‘cold launch’. That looks like a mortar firing the projectile up to the ignition point. As that’s a hot gas event; it presents unique hazards in operation that a true steam-ejection cold launch will not.