字幕表 動画を再生する 英語字幕をプリント imagine traveling from New York to London in just a couple of hours, or waking up in California on flying to China in time for lunch. Hypersonic flight could advance travel in ways we haven't seen since the invention of flight itself. But flying at hypersonic speed isn't easy. It presents incredible engineering and logistical challenges. So how close are we hypersonic travel Before we get the hypersonic speed, we should probably really talk about supersonic speed. Basically, supersonic speed is when you're traveling faster than the speed of sound, which is something we can and frequently do. Certain military airplanes will fly above Mach one on the Concorde commercial plane famously flew at supersonic speeds from 1976 2003. Supersonic speed is really, really fast, but hypersonic speed is in a league of its own, so hypersonic means typically velocities above Mach five, or even in the velocity is about 3800 miles per hour. Now, going at least five times faster than the speed of sound may seem crazy, but it's actually a milestone We've reached multiple times in the past, from the general public's perspective, probably the most visible example of hypersonic flight is watching. A space shuttle re entered the atmosphere now. Okay, sure, the space shuttle reaches hypersonic speed just by falling back to Earth. But in the 19 sixties, NASA did achieve man hypersonic travel through actual propulsion with an X 15 jet setting a speed record that, while on official, has yet to be broken. And there's pretty good reason for that effect so far. Flying Harper, sonically in the atmosphere, are catastrophic for the airplanes. Now we know parts of the official arts they would actually charge right you would have met because the studio off the aircraft was getting consumed. This is where the problem with long duration hypersonic travel starts. When you're traveling below the speed of sound, the temperature around the aircraft stays close to the ambient temperature. But once you break the sound barrier, a shock wave is created and the gas molecules behind the shockwave become compressed. This makes the air around the plane hot like really, really hot near hypersonic speeds. It's so hot that it could damage the materials that make up the body of the airplane. Now traditional airplanes are made of aluminum alloy. Is that have a melting temperature of about 600 degrees Celsius, and advanced aircraft will have titanium bodies with even higher melting points. But the air around an aircraft flying at Mach 10 can reach 3000 degrees Celsius. So how did vehicles like the space shuttle not burn up completely when they re entered the atmosphere at hypersonic speeds? Historically, what we've done is we just put on the heat shield that's 568 10 times heavier than it needs to be and thicker than it needs to be, because you can never be too careful. You want your people your payload to get back and one piece. But those heat shields typically burn off completely during re entry, and re applying a heat shield for every single flight wouldn't exactly be practical or possible for hypersonic commercial travel. Different materials are needed to withstand these extreme temperatures, and researchers are exploring all kinds of options, from tantalum carbide to boron nitride nanotubes. If hypersonic speed does this kind of damage to planes, what about the people inside? Fortunately, traveling at hypersonic speeds isn't harmful as long as it's constant. Rapid acceleration or a sudden change in direction is another story, so some simple money over that can be done with our liners. If you were to do the same, turn on Mark 10 the accelerations that will be generating within the coming for the passengers will be about 40 G's, right, 40 times the reputational acceleration, which would basically kill everybody on board. Another potential concern could be increased radiation from flying at higher altitudes, which a hypersonic jet would need to do. There's also the issue of losing cabin pressure while travelling that high up in the stratosphere. But flying commercially already comes with similar risks that airlines prepare for. Of course, none of these problems really matter if we are able to reach speeds of Mach five and above in the first place. Just because we've done it before doesn't mean it's easy to replicate historically way have just strap people to a rocket fired him into space. But if you wanted to fly from New York to Los Angeles on a hypothetical hypersonic airliner, a rocket isn't very efficiently to do things. One idea is to use something called a supersonic combustion ramjet or scram jet. A rocket has to carry the liquid oxygen it needs for combustion making it incredibly heavy, a not efficient for commercial travel. A scramjet, on the other hand, is able to use oxygen from the atmosphere to create combustion, even at hypersonic speeds. But the scramjet is still a work in progress. In 2015 Boeing's scramjet equipped X 51 flew Mach 5.1, but only for about 3.5 minutes. It was also unmanned and was launched from an aircraft already in flight, which isn't exactly what we have in mind for a long duration hypersonic flight. Despite this, there is real progress being made in hypersonic engineering just in a different kind of setting. So if you think about like a cruise missile flying at five times the speed of sound, that's incredibly hard to stop. And so that's what's driving a lot of the interest in the topic. Right now. Both China and Russia have claimed to have tested hypersonic weapons systems, and the U. S is currently trying to catch up, and this wouldn't be the first time hypersonic research started in military applications. It was after the war toe during the development off intercontinental ballistic missiles during the Eisenhower administration that there was a lot of research done in her purse. Onyx. Most of the fundamental concepts that we know today are they die from those times. Boeing is one company that's hoping to make the jump from military applications to commercial flight. It's concept for a hypersonic airliner comes after working with Darhk Ba on a hypersonic space plane and working on the scramjet powered X 51 with the Air Force. Boeing plans for this potential airliner to be able to travel at Mach five, reducing your transpacific commute toe a measly two hours. I mean, who doesn't want to travel from New York to Los Angeles in 15 minutes? Right? Every time the airlines make my seat narrower and make me have less legroom, I wish even harder that were flying at Mach five. And I could get to where I'm going in 15 minutes and only have to be stuck in the cattle car for that long. And that's the potential of hypersonic speed. The ability to connect anywhere in the world in that amount of time would be an incredible achievement. It's also critical to study as we plan to explore places like Mars because entering that planet's atmosphere would be done at hypersonic speed, the public imagination, perspective and the desire to have successful space missions. We need to do a good job of kind of working to these technologies in these research problems, its aerodynamics. It's material science. It's a computer science for controls and electrical engineering. It's all of these things that it's all a group that plays into this bigger hole. Nicey have personal travel similar toe what prehistoric fish be 300 million years ago when they left water on, they began life on land. So the gong kissed off air and space is just so fundamentally step in the evolution off humankind similar to love. The next step in connecting our little blue planet and eventually exploring planets outside of it might be conquering hypersonic speed. So how close are we to hypersonic travel? I think sustained hypersonic flight in a military. Since you know, in the form of, say, an unmanned vessel or something, you might see that in the next 345 years. I think that would be a pretty quick turnaround on that. As long as funding keeps up, I believe that with the correct level of funding with the enthusiasm of a population, it would be difficult to put a personal growth. For instance, in an aircraft fly beyond the mark. 6.7. I was a tiffin next 15 within the next 10 years, that dream of commuting around the world in a few hours, though for now you'll still have to deal with the long red eye intercontinental flight. Thanks for watching. How closer we and let us know in the comments what topics you want us to cover in future episodes. If you want more help closer, we click here to watch our play list and don't forget to, like, share and subscribe.