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The US has a lot of experience designing hypersonic missiles -- I remember when they were testing various material configurations in hypersonic guided missiles
by jandrewrogers 4y ago
The US has a lot of experience designing hypersonic missiles -- I remember when they were testing various material configurations in hypersonic guided missiles 30 years ago. Some of those platforms exist as operational systems today. Design of hypersonic missiles is largely limited by material physics and configurations thereof. The US ability to fabricate unique exotic materials allows them to search a much larger part of the performance and capability phase space before settling on a production design.
Historically, most of the bugs in new US hypersonic designs stem from an unwillingness to sacrifice terminal guidance performance for the sake of velocity. Sensor packages rapidly and unavoidably disintegrate due to atmospheric ablation in-flight, which makes terminal guidance very difficult (because your sensors barely work by the time they get to the target). Anyone can build a hypersonic missile if you are willing to forego high-quality terminal guidance, and most do. This is an extremely difficult engineering problem when operating at the fundamental limits of material physics but the US has been unwilling to field systems that don't address it.
- jandrese 4y agoSo you can build missiles that fly extremely quickly to a part of the sky where the target is no longer occupying?
- ARandomerDude 4y agoOr at the ground and hit the wrong target, potentially with very bad consequences.
- killjoywashere 4y ago@edenceover is probably referring mainly to the boost-glide vehicles that are moving at up to mach 20 ... through atmosphere. The air-breathing cruise missile type designs go slower (only mach 6-ish) but at that speed you can have a sane discussion about guidance. This rocket-guidance problem, by the way, is where the Black-Scholes model came from.
- govg 4y agoDo you mean Ito's Lemma? As far as I know, Black-Scholes itself had nothing to do with rocket guidance.
- killjoywashere 4y agoyes, thanks.
- jasonwatkinspdx 4y agoThe sensor stuff is a common but exaggerated discussion point in online discussions about this. There's a ton of previous work. Pershing II used terrain matching of SAR images for terminal guidance ages ago. The main technology for making this work is just electrically neutral ablative heat shields, which there are a variety of companies making commercially today. Other historical examples for say visual IR use quartz windows, etc. There's complications due to the heat and related plume, but the sweeping claims about this point are usually off the mark.
- jandrewrogers 4y agoQuartz isn't durable enough for hypersonic IR windows in dense atmosphere. When tested decades ago, actively-cooled sapphire, diamond, and even more durable exotics ablated too quickly for that purpose. I don't know what they are using today but the inability to find an IR transparent material that could survive long enough was a central design problem. This can be seen in the odd compromises made to the seeker design of e.g. THAAD, which doesn't spend much time in the lower atmosphere.