As mysteries continue to swirl around the balloon and three other so-far-unidentified objects shot down by the US in recent days, at least one thing has been clear: the weaponry used to knock them out of the sky. Be it the original, alleged Chinese surveillance balloon downed off South Carolina, or the objects targeted over Alaska, Michigan and Canada, all have been shot down by the same type of missile - the AIM-9X Sidewinder.
Here's what you need to know about it:
Who makes and uses them?
Raytheon Technologies Corp. produces the missile, which comes from a broader class of weaponry that has been in the US arsenal for decades. While the weapons are primarily manufactured for US forces, the missile is also sold in large quantities to a range of American allies. Raytheon says that it has 31 foreign military sales partners, with countries including South Korea, the United Arab Emirates and Indonesia having purchased the missile. Mainly conceived as an air-to-air weapon, the latest AIM-9X version is one that can also be used from the ground and against land-based targets. It is widely deployable in a range of modern aircraft including the F-16 Fighting Falcon and F-22 Raptor aircrafts. This versatility has allowed it break records by helping the advanced F-22 fighter jet score its first air-to-air kill. The US does not disclose the exact number of such missiles in its arsenal, but it's likely to be significant with the US Air Force receiving its 10,000th such missile in 2021.
Why are they being used to shoot down UFOs?
Using a missile helps minimize the risk to the pilot of the jet fighter by allowing them to stay at a much larger distance from the target, according to Iain Boyd, the Director of the Center for National Security Initiatives at the University of Colorado. "It would have to go much closer to the target to use a cannon and there have been reports of the aircraft sensors being interfered with," he said. While the Sidewinder wasn't designed for shooting down flying objects like balloons, they are cheaper and less likely to destroy payloads on the flying object that officials want to recover, unlike a radar-guided weapon like the AIM-120 AMRAAM medium-range missile, said retired US Air Force Colonel Michael Pietrucha. Their heat-seeking abilities may also make them more well-suited for doing so, he said. "You've got two conditions. In the daytime, you have the sun heating the balloon -- you're shooting from up-sun because it sees this giant sunlight reflection and will absolutely guide on that. And at night the balloon is warmer compared to the night sky," said the former irregular warfare operations officer and electronic warfare instructor who flew 156 combat missions in F-4G and F-15E jets. Even if the flying object does not generate heat, the missile will still be able to find it as "it's the relationship to the background that matters more," Pietrucha added. "The way you shot down balloons back in the day was incendiary ammunition against a hydrogen balloon. But that was 100-plus years ago."
How much do they cost?
The US Department of Defense is seeking to procure 255 of the missiles for $111.9 million in the 2023 financial year. That comes out to a cost of $439,000 each. But there are significant discounts involved and other countries will usually need to pay for associated equipment, parts and training costs as well. Malaysia sought to procure just 20 AIM-9X-2 missiles for an estimated $52 million in 2011, for example, after including such secondary costs.
How do they work?
The AIM-9X Sidewinder is a heat-seeking, supersonic, short-range missile. Its main components include an infrared homing guidance section, an active optical target detector, a high-explosive warhead and a rocket motor. The infrared in particular allows the missile to home in on targets in a range of settings at any time of the day. The 186-pound (84 kg) device is powered by solid fuel, and it has a length of 9.9 feet (3 meters). The so-called Block II variant of the missile has enhanced features, including a lock-on-after-launch capability so the pilot shooting the device does not have to rely on just visual aiming. When a pilot aims an AIM-9X, he or she will see a circle on the target on the heads-up display and hear a "growl" in the headset, said former US Air Force fighter pilot Pietrucha: "If you get a good growl, you're locked." The person shooting the missile will have a feedback loop that allows them to assess the quality of the shot.
What's their history?
Sidewinder missiles have a long history in the US military. They were first developed in the 1950s by the US Navy before being adapted by the US Air Force. It was the first heat-seeking guided missile to become operational. Early variants could only be used at very close range and could not be deployed at night. But subsequent improvements made it an ideal weapon for a variety of situations, and a later version of the missile was used during the Vietnam War. The missile is said to be the most proliferated air-to-air missile in the West with over 100,000 in circulation, according to the University of Colorado's Boyd. The AIM-9X is the latest iteration of the Sidewinder and began to be deployed in 2003. Still, defense officials acknowledge their use against unidentified flying objects such as balloons is novel. The military concluded that its smaller warhead and its shorter range allowed the AIM-9X to be deployed more safely and effectively compared to other missiles like the AIM-120, General Glen VanHerck, the commander of North American Aerospace Defense Command and US Northern Command, told reporters on Feb. 6.