There are a lot of references to speed and going fast in our culture, especially in video games, cartoons, and movies. Sonic the Hedgehog can run at supersonic speeds. Speed Racer is busy revvin’ up the powerful Mach 5. And in this summer’s hit movie Top Gun: Maverick, Tom Cruise flies the Darkstar hypersonic plane to “Mach 10”.
Ever wonder just how fast Mach 10 is?
To find out, we talked to Aaron Cassebeer, the senior director of engineering at Stratolaunch. His team is building a real-life hypersonic aircraft called Talon-A, designed to fly through the sky at Mach 6, or six times the speed of sound! That’s more than 3,000 miles per hour. It’s a cool piece of technology with some really challenging problems that pop up when you try flying that fast.
Have a question you've been wondering about? Send an email or voice recording to the podcast team to tell us what you'd like to hear in future episodes.
Perry Roth-Johnson (00:06):
Hello, this is Ever Wonder? from the California Science Center. I'm Perry Roth-Johnson. There are a lot of references to speed and going fast in our culture, especially in video games, cartoons and movies. Sonic, the hedgehog can run at supersonic speeds, Speed racer is busy revving up the powerful Mach 5, and in this summer's hit movie Top Gun Maverick, Tom Cruise flies, the dark star hypersonic plane to Mach 10. Ever wonder just how fast Mach 10 is? To find out we talked to Aaron Cassebeer, the senior director of engineering at Stratolaunch. His team is building a real life hypersonic aircraft called Talon-A, designed to fly through the sky at Mach 6 or six times the speed of sound that's more than 3000 miles per hour. It's a really cool piece of technology with some really challenging problems that pop up when you try flying that fast. Okay, let's get into it.
Perry Roth-Johnson (01:11):
Aaron Cassebeer. You are the senior director of engineering at Stratolaunch. Aaron, welcome the show.
Aaron Cassebeer (01:16):
Ah, thanks for having me. It's uh, it's great to be here.
Perry Roth-Johnson (01:19):
So Aaron, I know your company Stratolaunch is working really hard to make hypersonic flight a more routine thing again, and we'll dive into how all that works in a moment. But first I just wanna spend some time unpacking this word, you know, hypersonic, cause it's sort of a jargon word that aerospace engineers and aviation geeks might throw around. I think a lot of people may have heard of hypersonic flight recently in the media, like in the movie Top Gun Maverick where Tom Cruise flies this dark star hypersonic plane to Mach 10 or maybe more realistically, uh, in the news with reports this year of the Russian government firing hypersonic missiles in the war in Ukraine or even last year with reports of the Chinese government testing, hypersonic weapons that got U.S. Military officials at the Pentagon, very concern. So I'm hoping you can help explain it to our listeners. Like what is hypersonic flight? Can you just give us some basic examples?
Aaron Cassebeer (02:08):
So hypersonics, like you said, has become kind of a, a catch phrase lately in the, in the media, but in a very simplified view of it, hypersonics is flight. That is it least five times the speed of sound. So Mach 5 flight is considered hypersonic flight, which is five times the speed of sound and anything above that is also considered that. So Mach 10 would be 10 flying at 10 times the speed of sound.
Perry Roth-Johnson (02:33):
And the speed of sound. At least at sea level, it's like 700 odd miles an hour, right?
Aaron Cassebeer (02:39):
That's correct. It's about 700 miles per hour. So Mach 5 flight is, is in excess of 3000 miles per hour.
Perry Roth-Johnson (02:45):
I just wanna do like one more cultural touchpoint, the Concorde, even though it's not flying anymore. It's another like fast plane that people are familiar with probably because people could actually fly on it commercially, but it didn't go hypersonic. It, it, it wasn't going, uh, quite as fast. It was just supersonic just faster than one time the speed of sound. How is flying hypersonic different from flying supersonic in something like a Concorde?
Aaron Cassebeer (03:09):
When you get to that kind of that boundary, we, we loosely call it five times the speed of sound or Mach 5. There are some things that change for the designers, for the engineers and for the airplane. And so one thing is that there are literally physical changes in the air that changes the vehicles flying through it at those speeds. There's things like, uh, molecular disassociation and ionization...
Perry Roth-Johnson (03:33):
You're like ripping the air molecules apart.
Aaron Cassebeer (03:35):
It literally the, the physical phenomena or the physical way that the air molecules interact with the aircraft or the shape of the, the airplane as it moves through that air, it actually changes and it changes how you have to design the aircraft to fly. And then there's another big piece too, which is when you fly that fast, you start to have issues with heating. And so a vehicle when it is flying that quickly, um, you, you start to actually have to engineer and solve problems that didn't exist on a vehicle like Concorde, or like, you know, a commercial airliner that you fly in, you know, um, any day of the week. And so the vehicle has to, um, be able to withstand temperatures that are very, very high. So to give you an example, um, just roughly speaking a vehicle that's flying Mach 7 can, the hottest part of that vehicle can experience temperatures approximately 3000 Fahrenheit. Wow. Just to give you a rough, just to give you a rough idea. Right. And so you now, as an engineer, you actually have to be thinking about, well, wait a second. What, what materials don't melt at 3000? Right. Right? How do you protect, how do you protect your airplane from literally melting, falling apart and making sure that the electronics inside they still function? What happens is as you go faster and faster. The design challenge for the engineers gets harder and harder.
Perry Roth-Johnson (05:04):
Yeah. And, and is hypersonic flight a new thing or is it just like in the media a lot lately?
Aaron Cassebeer (05:11):
No hyper hypersonic. Flight's been around for a long time and you, you know, the United States has been a leader in hypersonic flight from the very beginning. It goes back to the fifties and sixties when there were some very interesting, very exciting X planes, um, that were designed in, in the United States and flown out here, uh, actually mostly in the Western United States to break through, uh, that perceived barrier of hypersonic flight. That was the really, uh, interesting time for hypersonic flight was the push towards vehicles like X-15, if you go and look up that vehicle, uh, that vehicle's actually in the Smithsonian in Washington DC and, and that, that vehicle flew almost 200 times. Wow. Uh, and so it's been around for a long time. It's had its ebbs and flows of, um, of being popular, I guess I'll say it that way. Uhhuh and, uh, lately of course, like you said, it's back in popularity, it's back in demand.
Perry Roth-Johnson (06:06):
Why is it in Vogue again now? Why, why are so many governments and companies working on hypersonics, now?
Aaron Cassebeer (06:12):
There are some near pure threats that we have. You talked about Russia and China, and those are two excellent examples. They've invested heavily in these technologies and these capabilities. And they've been able to rapidly develop some vehicles and fly those vehicles, uh, in ways that heavily chips away at our ability to be, you know, the leaders in that, in that area. That's a challenge for us because as Americans, we like to think of ourselves as a leading innovator in the world on the global stage, right? And so that is the number one driving reason why you see a lot more media attention, you see the government, you see our lawmakers making some changes and increase funding in hypersonics. And that's because of that threat and that concern.
Perry Roth-Johnson (06:59):
So basically like we want to have that technology home grown so we can keep up with our peers around the world.
Aaron Cassebeer (07:05):
Absolutely. You could see this in many other sectors of aerospace and, and technology. You know, we like to be the leaders and be pushing the boundaries and doing, having the firsts.
Perry Roth-Johnson (07:16):
And then why did Stratolaunch, uh, specifically start working on a hypersonic vehicle?
Aaron Cassebeer (07:22):
Our investors saw a clear need for this investment to help participate and to help close that gap such that America could not only, you know, match what our competitors are doing, but then of course, leap ahead and try to be the lead, the lead global innovators and leaders in this area from a technology standpoint, honestly, just from a technology standpoint. It's really cool. Yeah. It's really cool to be able to fly things that quickly. And as we know, you know, whenever you take a leap in really interesting things are found and learned that we didn't even know existed before we did it.
Perry Roth-Johnson (08:04):
So let's talk about, you know, the specific vehicles you guys have in your, your hanger right now. So there's the carrier aircraft, which is nicknamed Roc, uh, which is also the world's largest wingspan plane, right. Um, and also a small hypersonic aircraft, uh, called Talon-A, um, before we get into like how each of those look at a high level, can you just describe what a typical mission for these vehicles will look like?
Aaron Cassebeer (08:29):
The Roc aircraft, our carrier aircraft, um, its job is to take another vehicle in this case Talon-A, you know, Talon-A is mounted to the underside of the center wing of, of the carrier aircraft. And so the carrier aircraft's job is to basically bring that, that hypersonic vehicle Talen A up to, um, a higher altitude so that we can air launch it. Mm. So literally what you're talking about is connecting two airplanes to each other, taking off, flying and climbing up to a higher altitude. In this case, let's call it, uh, you know, approximately 30,000 feet and you air launch the vehicle, which means you, you, you literally, as you're flying along airborne, you drop the Talon-A vehicle at altitude. And as the tall a vehicles falling away, it literally starts to activate all its subsystems and it's, it starts to fly on its own. It, it ignites its engine. It actually has a liquid rocket engine. Um, very similar to, uh, the X-15. If you go look up that vehicle, it's, there's a lot of similarities, actually. Um Talon-A is unmanned though. So whereas X-15 was a rocket engine, power hypersonic vehicle Talon-A is actually fully autonomous. So there's no human on board. There's no remote control Talon-A, uh, is doing everything on its own and computer and flight software, literally managing, managing the vehicle as it's flying through these conditions. So you drop you drop the Talon-A vehicle at altitude from Roc, Roc continues to fly along and comes back for a landing and the Talon-A vehicle lights its engine, climbs to an altitude that's still within the atmosphere. So you're still, we're not going to space, we're not, you know, we're not leaving the atmosphere. We're we are, we are, we are flying through low density atmosphere, which is, you know, we're talking up to 160, 70,000 feet. And so there's enough air molecules that you can still consider yourself. You know, you're not in space, you there's air density, but, uh, but there's enough of them that you can actually really heavily heat the vehicle. And so the vehicle passes through the hypersonic test condition, you know, in this case, we're talking Mach 5, Mach 6, approximately. And, uh, once we deplete all of the propellants, basically the fuel in the oxidizer that feed the engine and make the engine create, you know, produce thrust. Once we deplete those, uh, we'll turn off the engine and we'll, we'll glide back. Unpowered with no thrust back to a, a runway, a conventional runway. And so we'll land this vehicle. That's another key thing about Talon is it's actually reusable. We'll be able to land this vehicle and we'll be able to bring back all the experiments that we've carried on board. And we'll be able to basically ref uh, lightly refurbish the vehicle and then launch it again within a couple weeks.
Perry Roth-Johnson (11:19):
It's almost like a mini space shuttle that doesn't go to space and doesn't launch from a launchpad.
Aaron Cassebeer (11:25):
It, it is. They serve different purposes. You know, a space vehicle is designed to punch through the atmosphere. You know, you, you have a, typically have a rocket on board, right? You punch through the atmosphere and you launch yourself into space and you have specific reasons why you do that Talon-A is meant to specifically not punch through the atmosphere. We wanna stay up in that part of the atmosphere, where, where we can test things in a hypersonic environment. And we can basically, um, accelerate technology through Talon-A, basically carry payloads. It's, Talon-A is effectively a test bed. It's a, and so what we do is we carry experiments. We carry new technologies. We carry things that haven't flown before. We take things that maybe they've been developed by scientists in the lab and engineers in the lab, and now we actually get to fly them and we get to prove that they work. That is the entire purpose of Talon-A. Talon-A itself is not the experiment. Talon-A is not meant to fly faster than, you know, to be the, the fastest flying vehicle that's ever flown. That's, you know, there's other vehicles that are designed to do that. This vehicle is designed to fly hypersonically into it often, and to do it such that we can give our customers an opportunity to fly things reliably, often, and to be able to, to push their experiments to new boundaries that they haven't seen before in the lab.
Perry Roth-Johnson (12:49):
It's almost like, um, a really fast cargo plane, uh, and people, I guess, pay you money to like put cargo on it.
Aaron Cassebeer (12:56):
People joke, uh, this has been used before. I actually think it's a great analogy, but it's, it's, it's, it's a think of it as a, a pickup. It's a Ford. F-150. It just happens to fly hypersonic okay. So it's, it's actually a utility vehicle. Okay. Um, it is a high performance vehicle, but it's also a utility vehicle. And it's offering that utility of being able to test things and be that test bed. And so it, it offers people a way and customers a way to test things where they can't otherwise test it on the ground, like in a wind tunnel or another facility. Right. When you fly something and you you're, when you go to, you know, Mach 5, 6, 8, 10, 15, for the first time, that's really risky. It's really, it's dangerous. It's risky. It, you might crash the vehicle. And so you want to find every opportunity you can to reduce risk and to learn as quickly and affordably as possible. Talon-A is a means to quickly and affordably do that.
Perry Roth-Johnson (14:01):
Okay. So let's transition a little bit into, uh, you know, the mothership, the carrier aircraft Roc, um, cause that's how Talon launches. Talon is not taken off from the runway in Mohave by itself. Right. Um, what is the Roc carrier aircraft look like?
Aaron Cassebeer (14:16):
That's a great question. It's unique. It's, it's very unique. So it has the largest wingspan, um, of any aircraft ever flown, uh, it's 300 and uh, 85 feet. And it has, it actually is the highest thrust aircraft that we know of that that has ever flown as well. Um, it has six, six engines off off of 747. And so, so, it's got a lot of thrust. It's got a huge long wing and it's got two big fuselages, which are separated such that the center line of the vehicle is wide open underneath. And the reason for that is it's it's configured so that you can actually mount something very large, much larger than Talon, uh, underneath that carrier aircraft wing so that you can air launch things from the size of Talon, all the way up to something that's potentially 500,000 pounds and, and you know, much larger. And so the carrier aircraft is unique is very unique because it can do a lot of things and it can, it can launch things of the size that basically no other aircraft on the planet can do, you know, some people listening in might say, well, I don't understand why, why do you, do you need to another, add another airplane?
Aaron Cassebeer (15:29):
That sounds really complex. Yeah. You know, the reason you do it is cause it actually helps you for on performance. It, it significantly improves our efficiency and our performance to be able to make Talon-A more successful and so if you were to try to take off from a runway with Talon-A it's it's physically possible, it can happen, but it makes the design much more difficult. It takes a lot of energy to get from here to 30,000 feet in, in the air. And so not having to do that and allowing Talon to launch at a higher altitude, um, is a huge performance benefit to us,. So it basically allows us to fly for longer at hypersonic condition is what it does.
Perry Roth-Johnson (16:07):
I wanna go back to that stat. You said about the, the wingspan, you said 385 feet that that's bigger than an American football field, right?
Aaron Cassebeer (16:16):
Perry Roth-Johnson (16:16):
Like it is, I think those are 300 feet long.
Aaron Cassebeer (16:18):
Yeah. If you were to place a rock on a football field, you know, lengthwise, you know, the wing parallel to the football field, you know, it would basically be goalpost to goalpost it's it's um, when, when you walk in the hanger and you know, you experience this as well, you walk into the hangar, you can't, you can't see the whole airplane. You look up in your field of view. You, you can't even really see it because you're, you're basically too close to it. You actually have to walk a hundred yards away to even be able to get the whole airplane in view. It's just, it's huge. It's hard to explain honestly.
Perry Roth-Johnson (16:52):
Aaron Cassebeer (16:53):
I'll be honest, I've normalized it cause I've been around it for like a really long time.
Perry Roth-Johnson (16:57):
Yeah. Um, you don't think it's weird anymore probably.
Aaron Cassebeer (16:59):
Yeah. I've been around Roc since the very beginning of that program more or less, you know? So, um, yeah, so I've kind of normalized it, but most people it's, it's actually really fun cause when you bring new people into the hanger, there's kind of that moment where they, their eyes just go wide open and, and they just they're shocked. They they're, they, they always say the same thing. They say, man, I knew it was big, but I didn't think it was gonna be that big.
Perry Roth-Johnson (17:25):
Right. I definitely had that moment too. And, and I noticed, um, when our host, Kate, you know, was, uh, uh, trying to take a picture of us standing in front of it, you know, she had to keep backing away in a way. And it was like the same experience we have at the California Science Center with space shuttle Endeavor where it's like hard to fit in your camera's view finder without like getting so far away that the people you're trying to take a picture of are just like, you know, a few pixels wide.
Aaron Cassebeer (17:51):
Yeah. It's a, it's it's a, it's a feed of engineering. It's amazing.
Perry Roth-Johnson (17:55):
The nickname Roc. Where did that come from?
Aaron Cassebeer (17:58):
Oh yeah, that's a good one. That's a good, that's a good, uh, uh, probably little known, uh, fact, I guess. So the, um, Roc R-O-C not, not R-O-C-K it's R-O spelled R-O-C. It was a, uh, it was a mythical bird which carried, uh, an elephant in its talon's if I remember correctly, but okay. It's effectively, uh, a large bird that, that, you know, that could carry things in its claw. And so that's what Roc's job is to do. Roc's job is to carry large things and to deliver them to an altitude, they can, they can launch them.
Perry Roth-Johnson (18:37):
So as, as we're coming to the end here, Aaron, uh, it sounds like stratolaunch is a really exciting, cool place to work. Uh, where can people either follow you online or follow stratolaunch online, you know, to follow your guys' work?
Aaron Cassebeer (18:48):
Uh, stratolaunch.com of course is our website. That's, that's pretty easy to find us. Instagram, Facebook, uh, Twitter, we, we have accounts across all those platforms, YouTube as well. You know, when we, we oftentimes when we're flying the Roc aircraft, we actually have live streams of the flight. So we actually are, you can watch in real time cool. Often, uh, when we're flying and that's very cool. Um, we also have a lot of really interesting videos up of when we make some significant progress. We share those, like recently we had a video where we mounted Talon, uh, to the, to Roc for the first time. We literally mounted it under the wing. Nice. And there's some really great videos out there for that. And then also, um, LinkedIn, you're gonna be able to find many of the engineers that work here. Um, you're gonna be able to find everything from job postings and, um, and recruiting events and things of that, of, of that nature. So you can follow us through any of those normal kind of channels professional or social media channels.
Perry Roth-Johnson (19:45):
Well, it's been great talking to you, Aaron. Uh, thanks for demystifying hypersonics for our listeners a little bit, uh, and appreciate you joining us on the show.
Aaron Cassebeer (19:52):
Absolutely. And, uh, I only barely brush the surface of the topic and I promise you if you get in, if you get in deep, uh, it's a lot more fun. It's really interesting. It's a really challenging place to be and it's, uh, it's pretty darn cool.
Perry Roth-Johnson (20:08):
That's our show, and thanks for listening until next time keep wondering. Ever Wonder? from the California Science Center is produced by me, Perry Roth-Johnson, along with Jennifer Aguirre, Liz Roth-Johnson is our editor. Theme music provided by Michael Nickolas and Pond5. We'll drop new episodes every other Wednesday. If you're a fan of the show, be sure to subscribe and leave us a rating or review on Apple Podcasts. It really helps other people discover our show. Have a question you've been wondering about? Send an email or voice recording to email@example.com, to tell us what you'd like to hear in future episodes.