The AIM-4, Pk, and Hit to Kill, or why the AIM-4 was, in my opinion, the deadliest air-to-air missile the US had in the '60s.
A short thread on why the hit-to-kill method employed by the AIM-4 Falcon was more effective than the influence fuzes of its contemporaries.🧵
The best place to start is with missile development status in 1951. Thanks again to @MassiasThanos for finding this document (ADA8001650 p.158).
At the time, the relative effectiveness of various methods for warhead kill was unknown. As such, different methods were explored.
The Falcon was intended to exploit the advantages that its highly accurate guidance and autopilot system provided it. By ensuring a direct hit, the warhead could be much smaller (1/3-1/10 the size), performance could be higher, and front-aspect shots were more reliable.
This is not to say that the warheads of other missiles were not lethal. They were very dangerous to all sorts of different targets, both fighter and bomber, but the Falcon stood out, especially in regards to bomber interception.
Since I have no information on Sparrow III warhead effectiveness, I will be using Sparrow II data from CARDE instead, with continuous rod and blast-frag.
The CARDE assessment was a simulation designed to assess the performance of the AAM-N-3 Sparrow II against a TU-95 target.
Though this only gave rough estimates, it still proved that an expected radar missile shot against a heavy bomber was not very likely to result in a kill.
The fears expressed in 1951 of fuze issues ended up coming true, though not in quite the same way.
The radar fuzes of early AIM-7s suffered significantly over Vietnam, even at higher altitudes. They would fail to detect the target, or detonate too early.
This trend of a lack of lethality continued with the Sidewinder. With more optimistic numbers, the AIM-9B's measly 25-pound warhead gave a catastrophic kill percentage of 30-40%.
The 9B's infrared influence fuze also suffered from severe issues and was rear-aspect only.
Why were these numbers so low? We go back to the methods that most warheads use to destroy or damage a target. Fragmentation. This means that pK is a dice roll. Due to miss distance and fragment distribution, there is a chance that none of the fragments will do any damage!
By lowering miss distance, you can ensure that more fragments will hit in a small area, increasing the point damage and the probability of damaging something important in that area, but it still does not ensure a kill.
The Falcon's accuracy allowed it to bring that miss-distance down to zero. By detonating 2.5-5 pounds of HBX explosive wherever it hit, it could ensure severe damage and increase the chances of bringing down a bomber.
This was for multiple reasons. The first was that of blast effects. The Mk 108 used by Germany in the Second World War was exceptionally effective.
The combination of blast and fragmentation, from only 3 ounces(!) of PETN explosive, could nearly cut a Bristol Blenheim in half.
The second reason was the semi-penetrating effect of the AIM-4.
The Falcon's wing-mounted contact fuzes were placed behind the warhead. This means that, like a timed fuze for a cannon shell, the AIM-4's warhead would penetrate the aircraft's skin before detonating.
This effect was noted even before the development of the Falcon, with the extremely high effectiveness of the Folding Fin Aerial Rocket in bomber interception. Even a single hit could bring down a heavy bomber.
This also brings us back to the first document, which mentions the low weight of the Falcon allowing the carriage of multiple missiles.
Falcons were designed to be launched in a salvo. Two or three for the early Falcons, and two for the late Super Falcons.
As such, Pk assessments were extremely high for the Falcon family. The Super Falcon, when employed against bombers, was expected to far outperform any of the influence-fuze-based missiles.
Unfortunately, I've struggled to find a study for the AIM-4 comparable to the CARDE assessment of the Sparrow II, so like-for-like will have to wait until I can get my hands on test documents.
With the death of the AIM-4 program and the exaggerated issues with hit-to-kill against maneuvering targets, this method of bringing down targets was abandoned.
As higher missile maneuverability becomes possible, especially through bank-to-turn guidance, I believe we may see a return to hit-to-kill missiles for air-to-air. Their reliability and weight savings may prove a significant draw over even advanced blast-frag warheads.
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Since the end of the Cold War in 1991, the US Navy's ability to conduct air superiority and offensive strikes has been slowly diminishing. Today, we stand at an inflection point, where the F/A-XX program to deliver a new strike fighter to the Navy is in Jeopardy.
🧵
This thread is a pitch for a congressional write-in campaign. The first part is a history of the degradation of the Navy's air wing. The second part is an analysis of a recent oversight hearing. The last post of this thread contains instructions for emailing your representatives.
In the 1980s, the A-6F was proposed for development. This was to be an updated A-6E including modern avionics, new engines, and AMRAAM. This would have provided the Navy with a relatively low cost program, retaining a two-seat crew with a large payload and good mission systems.
Some very interesting stuff going on here with the Shenyang aircraft. 🧵
Exhaust appears visually similar to the F-22's with 2D thrust vectoring and shrouding. Wing shaping is nothing particularly special but seems good. Like JH-36, it retains some conventional control surfaces.
The all moving wingtips are a novel solution. I don't know what the trade offs are but they must be at least somewhat worth it. Potentially these are considered lower risk, higher strength, or more effective than the semi-morphing control surfaces on the JH-36.
The intake design is interesting. Unlike JH-36, which uses caret intakes underneath and uses a DSI above, the Shenyang aircraft uses what appears to be two DSIs below. The gear appears to fold sideways into a bay ABOVE the side bays, giving it a J-20-esque four bay arrangement.
With the renewed interest in the Europa wars, this may be the best time to bring up the unusual short ranged missile developed for space-superiority craft.
The AIM-95E "Europa Agile," the only missile designed for operation in deep space AND within thin atmospheres.🧵
First off, I apologize in advance for the lack of photos on this topic. All existing photos of Agile are of the ones designed in the 1970s for operation within Earth's atmosphere. Therefore, you will have to imagine some of these changes to the system.
The Agile for aerial use was cancelled in the mid 1970s after about $50m was wasted developing several different airframes and seekers. This spelled the end for the program as most know it, but this would only be the starting point for the Europa Agile.
For my entire life I have been taught about the importance of effective searches. Since May 2024, I have fought with an unwanted feature that has made my experience worse.
A rant about "AI Overview," AI assisted search and their impact on using Google as a tool for research.🧵
Google has billed these features as "taking the legwork out of searching" and "able to answer complex questions." This is a bald faced lie.
The AI has wasted more time than it has saved me, lied about results, and forced me to learn methods to get around it rather than to use it.
I do a lot of research using keywords that I need matched exactly. For example, right now, I was looking up the specific thrust of the General Electric F414 engine used in the X-59, an experimental plane in development for NASA. This should be a simple question to answer.
For years, I've been working towards building a website to house all of my opinions and research. Today, it goes live with the launch article: Jet Fighter Generations Aren't Real.
This website comes with a major change in how I produce and share content, so please read. 🧵
First, here's a link to the article. I would have put it in the tweet above, but this website hates external links, and so it wouldn't have been shown to many of you.
For this reason (among others), I politely ask you to spread the word about this website.greatdefensesite.org/articles/fight…
X has unfortunately limited the topics I can present, the formats I can present them in, and the wording I can use to make a point. This website, for all its claims of free speech, has countless filters and algorithm features that harm post visibility. I'm tired of that.
I think I've found my least favorite Sidewinder variant. From everything I can tell, it's a perfectly serviceable heat-seeking Air to Air missile with decent capabilities. But I hate it.
This is the Republic of China's Tien Chen-1 (天劍一).
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The TC-1 was the ROC's first attempt at an indigenous air-to-air missile. From what I can tell, it appears to be slightly better than the AIM-9P-5, which is a great showing, but again, I hate it.
To explain why I hate a missile that looks like an AIM-9L, we have to take a few steps back. When the AIM-9D was developed as a follow-on improvement to the AIM-9B, the Sidewinder went through a major redesign.