**Breaking the Sound Barrier on Land**

The concept of breaking the sound barrier is often associated with air travel, but it's also relevant to land speed records. As an object approaches the sound barrier, the air around it begins to stack up like a pile of pancakes, making it harder to push through. Once this barrier is broken, the object creates a sonic boom.

The process is similar on land, where the sonic boom hits the ground being run on. In high-speed motorboats, this drag is referred to as "spray drag." The additional drag created by giving momentum to the air or water leads to a higher speed requirement for breaking the sound barrier on land compared to in the air.

**Land Speed Record History**

The first person to break the sound barrier was Chuck Yeager in 1947, flying the Bell X-1 at an altitude of around 26,000 feet. However, it wasn't until 1997 that the sound barrier was broken on land by the Thrust SSC team. This achievement required a super sleek and powerful vehicle with wheels, weighing around 10 tons and generating an equivalent 100,000 horsepower – roughly 1,000 times more power than a typical Mazda2.

The record-breaking speed of 763 miles per hour (1229 km/h) was achieved over a short distance, but the initial goal was to break the sound barrier on land with a vehicle capable of reaching 1,000 miles per hour. That's where Dr. Ben Evans and his team come in, working on the Bloodhound LSR project.

**The Bloodhound LSR**

The Bloodhound is currently the contender for the land speed record, scheduled to make its run soon in the Hakskeenpan dry lake bed in South Africa. This stretch of flat land is so even that you can see the curvature of the earth over a 10-mile distance, with elevation changes of only 300 millimeters.

The Bloodhound team has been testing the vehicle, which has already reached speeds of up to 628 miles per hour (1012 km/h). With its equivalent of 135,000 horsepower or 10 gallons of liquid horse juice per second (as Dr. Evans humorously put it), the Bloodhound has the potential to reach 1,000 miles per hour.

**The Human Body Limitations**

However, there are still holes in this equation that need to be addressed. The main challenge is sustained g-forces, which affect the human body differently than instantaneous g-forces experienced during a crash. In a land speed record attempt, the driver would experience sustained g-forces from launch to the moment they pull out the parachute.

Dr. Evans explained that in principle, the only way to overcome this barrier of how much distance can be covered is to accelerate and decelerate quicker. However, this leads to another challenge: the human body's limitations. Fighter jets can reach higher g-forces for a relatively short time, but sustained g-forces are what make breaking the 1,000 miles per hour barrier so difficult.

**The Future of Land Speed Records**

In conclusion, while we don't know if it's possible to break the sound barrier on land with a vehicle reaching 1,000 miles per hour, Dr. Evans and his team believe in principle that the Bloodhound has the potential to do so. Will they succeed? Only time will tell.

Big thanks to Dr. Ben Evans for taking the time to speak with us about this fascinating topic. If you're interested in learning more or watching an extended cut of our interview, be sure to check out the Donut Underground YouTube channel.

WEBVTTKind: captionsLanguage: en- Back in October, theSSC Tuatara set the recordfor the fastest productioncar in the worldat 316 miles an hour.That is crazy fast for a production car,but it got me thinking,what's the top speed any car has gone?Well, it turns out it's overdouble that, 763 miles an hour.And that record was set...Hold on, is that right?23 years ago?Well, car technology hasobviously advanced itthen so why hasn't anyonebeaten this record?- Well, I mean the oldtextbook you can go and buythat tells you this is how you designa 1000 mile per hour car, right?- Well, that's Dr. Ben Evans.And he's part of the teamlooking to break that recordby building a car tohit 850 miles an hour.And 850, that's cool and all,but you know what else is cool?1000 miles an hour.Is that even possible?I mean, what does it taketo make a car go 1000 miles an hour?Well, today we're gonna break it all downand it turns out it'spretty, pretty complicated.So let's get into it.(upbeat music)(beep)Big thanks to Audible forsponsoring today's episodeof Bumper 2 Bumper.Now your old uncle Jerry over herehas a lot of free time on his hand,and there's only so muchbirdwatching I can do.I've seen literally all birds,but I heard about this thingcalled the interweb book thingyand it's called Audible.I found out they had thesethings called audiobookswhere a voice reads me a bookthrough this headphone things.It's great.A voice reads to me.Okay, what the heck it's magic!And I've been listening to Greenlightsby Matthew McConaughey narratedby Matthew McConaughey.You know, I do pretty goodMatthew McConaughey impression.All right. All right. All right.Nailed it.Now Audible isn't just limitedto literally thousands of audiobooks,oh no no, they have allsorts of exclusive podcasts,theater performances andguided wellness programs.So hurry up and try outAudible for yourself.Head on over to audible.com/bumper2bumperor text on your little phone thing,BUMBER2BUMBER to 500-500,you get 30 day free trial.Okay, I gotta get back to this audiobook.Take me away Matthew, take me away.I'm picturing him withhis shirt off right now.You don't know it, but he's naked.All right quick physics recap.In order for a car to accelerate,there has to be an imbalancebetween the force pushing it forwardand the resistance trying to slow it down.As long as there's more forward force,the car will continue toaccelerate faster and fasteruntil it's met with anequal amount of resistanceat which point it willeven out at its top speed.So to help us visualize this,made a little Donut balance.And on this side, oh (beep).This side will representthe forces necessaryto drive the car forward.And this side represents theforces creating resistance.Let's say this shot ofliquid equals 100 horsepower,about the same as a Mazda2.Now on a frictionless surfacewith zero resistance in a vacuum,you wouldn't need more than 100 horsepowerto get to 1000 miles an hour.But in the real world,that 100 horsepower,it's gotta go through a drive trainwhich creates mechanical resistance.It's gotta overcome rollingresistance from the tires,and it's gotta push back air resistance,pushing back on the car.Now these forces createresistance on the carwhich is why 100 horsepower Mazda2isn't breaking the sound barrier.In fact, it's barelybreaking 100 miles an hour.That's a 10th of the speed we need.So to go 10 times faster,why don't we try givingit 10 times more power?So now we're at 1000 horsepower.1000 horsepower 1000 miles an hour.Big bang boom we got it.Well, it turns out thatit's not that easy.An actual 1000 horsepowercar, like the Bugatti Veyronit only reaches about 250 miles an hour.And one of the main reasonsis more air resistance.The faster you go, the more it stacks up.(chuckles)Now let's actually look at the equationfor determining air resistance.It includes the density of the fluidwhich is just our atmosphere,the velocity of the object,that's how fast it's going,the coefficient of drag,which is just a measurementof how well the shape of anobject can move through a fluid,and the cross-sectional area.But really the most important thingis this a little two right up here.Because the velocity is squared,it means that an increase in speedresults in a quadraticincrease in air resistance.Meaning that if you double your speed,the drag force it doesn'tdouble, oh no, it quadruples.So we have a few ways inwhich we can combat this.We can keep increasing thepower or we can reduce the drag.Well, sometimes reducingdrag isn't an optionbecause it can be the only thingkeeping the car on the ground.Passenger cars naturally havea shape that generates lift.Look at the cross sectionof an airplane wingand look at a car, theylook pretty similar.Now if we didn't doanything to combat the lift,and then a car like a Mercedes A-Classwith the lowest coefficientof drag for production cargoing about 250 miles an hourwould generate enough liftto counter 98.3% of its own weight.The car would be theequivalent of 55 pounds.Now a bump in the road or slight breezewould be enough toknock the car off courseand the steering, well,it would be almost uselessas front tires would have no traction.So to combat this, weneed to add some downforcebut that downforceinherently creates drag.So reducing drag is pretty muchout of the question for now.Our only option is to increase power.- More power baby.- So if this is equivalentto 100 horsepower,then this is equivalentto 10,000 horsepowerabout the same horsepowerthat's in a top fuel dragster.And these drag racerscan hit 300 miles an hourin under four seconds.But dragsters like this onlyrun a quarter mile at a time.Well what if we just say,we just let one of them keep going?Could it reach our goalof 1000 miles an hour?What do you think?No, they can't.And the easiest way toexplain why this is,is because dragsters are builtso specifically for one taskthat they can barely survivejust one run that they do.Their clutches, literallythey last one runduring which they weld themselvestogether from friction.So if we wanted a dragster to keep going,you're gonna need morecooling, you'd need more fuel,you need a bigger transmission,you need beefier engine internals.And all of that meansyou have more weight,more weight means we need morepower, which means more fuel.And to have that more power,we need to cool all that,which means more weight.It's a snake, eating its own tail.Hmm! Yum, yum!Ah, I love my tail.Hmm my tail so good.Yum, yum, yum!And we haven't even gotten intothe mechanical limitations.So let's look at the Veyron for instance.Now forget wind resistance,forget rolling resistance,forget parasitic losses and all that jazz.It can still only go as fastas its engine can spend.So say we want the Veyronto reach 500 miles an hourwith its current rev limit of 6,600 RPM.We could on paper do that.And in fact, we did the math.(audience laughs)We would need the last gear ratioand the transmission to be 0.42which would be somethingaround like 15th gearif we had to step it all the way up.Or we need 53 inch wheels,which would be a pretty ball awayto solve this physics problem.And while that works on paper,it doesn't account for parasiticlosses, component strengthand the added unsprungweight of the wheels.Not to mention, the enginewould need way more torqueto turn a system that big.Now land speed record carshave come up with a solution for all this,but it isn't more torque it's no torque.No torque.- As soon as we hitkind of four hundred-ishthat sort of region 400miles an hour or so,that's when the switch had to happento thrust driven vehicles.- Now, this is Dr. BenEvans aerodynamiciston the Bloodhound LSRLand Speed Record Project.The current car going for the record.- And it just becomes the more natural wayof propelling yourself forwardonce you're at these sorts of speeds.- Now what he's talking aboutis rocket and jet powered cars.With these there's no torque measuredbecause nothing is turning.Instead, we have pounds ofthrust pushing us forward.How much thrust?Well, the land speed record holderfrom the 1970s reached 622 miles per hourusing a rocket engine making22,500 pounds of thrustwhich in liquid horse juiceterms is about this much.Mazda2, 1970s land speed record holder.(heavily sipping liquid)Now this is about 58,000 horsepower.Now the car was called the Blue Flameand it held the official landspeed record for 13 years,which actually brings meto the next problem in this equation.And that's the record itself.The land speed record is anofficial FIA world recordand to hold it, you can'tjust reach the top speed,oh no, you gotta stay there.And the record is for a flying milewhich means that thespeed is the average takenover a whole mile and then it's averagedagainst another run inthe opposite directionwithin the same hour.Now the Blue Flame waslike a bottle rocket,it relied on its lightweightand bursts of thrustfor its speed.Now that design only gets us so farbecause after 650 miles an hour,air pressure begins to increaseas we enter a space called-- The Transonic regime.- No I'm not talkingabout Jared Leto's cult.Although Jared Leto hit meup, I'll be part of your cult.- Essentially the transonic regimeis as soon as there's airflow around the vehicleis traveling fasterthan the speed of sound.And that happens before the vehicle itselfgets to the speed of sound.And that's when drag really startsto build up around the vehicle.- So basicallyas an object approachesthe sound barrier,the air begins to stack upon the nose of the objectlike a pile of pancakes thatare harder to push throughthan your normal air.And once you break that sound barrier,object pokes through thatpancake and they break apartjust like this analogy andyou create a sonic boom.At least that's how it works in the air.On land that sonic boom hitsthe ground you're running on.- The fact that you'regiving that spray momentum,leads to a drag term and inkind of high speed motorboats,they refer to this drag as spray drag.And it's a similar phenomenon for us.So we've termed this additional drag,which, you know normallyas an aerodynamicistyou don't need to accountfor, a spray drag.- So you can see why it'd be a lot harderto break the sound barrieron land than in the sky.And it wasn't until 1997,50 years after Chuck Yeagerbroke the sound barrierin the Bell X-1 that the sound barrierwas just barely brokenon land by the ThrustSSC.All the components and power needed meantthat this super sleek looking planewith wheels weighed 10 tonsand made the equivalentof 100.000 horsepower.A thousand times more powerthan our little Mazda2.Just to get a peeky towacross the sound barrierfor just a second anda record speed averageof 763 miles an hour.We're not even close tohitting 1000 miles per hour.So how much more do we need to get there?Well, this is where Dr. Evansand the team building theBloodhound LSR come into play.Now it's the current contenderfor the land speed recordand it's scheduled to make its run soonin the Hakskeenpan of South Africa.Now the Hakskeenpan isa dry lake bed so flatthat you can see thecurvature of the earth.Over a 10 mile stretch,the elevation changesby only 300 millimeters.And it's even flatter nowbecause the Bloodhoundteam removed 16,000 tonsof stones by hand.Now with the equivalentof 135,000 horsepoweror 10 of these gallon jugs,Bloodhound has already made itto 628 miles per hour in test runs.And it's gonna go a lot faster.So yes, Bloodhound in theorycould go 1000 miles an hour.It's got the thrust, it'sgot the drag coefficient,it's got the crazy team behind it.But there's still someholes in this equationthat you just can't slap a MoPowa Babeh Sticker over it.And we've talked aboutg-forces and their effecton the body in previous episodes.But the main thing you need to knowis that sustained g-forceis way worse for the bodythan instantaneous g-force.In a crash, you might experience8g or more for a second,but in land speed record attempt,if you wanted to maximizeyour use of the space,the driver would experience sustained Gfrom the moment of launch all the way upto the moment they pull parachute.And then there'd be more sustained Gas the car decelerates to stop.- In principle, I mean the only wayyou can overcome that barrierof fundamentally howmuch distance do you haveis accelerate quicker, decelerate quicker,but then you move into the realmsof what can the human body sustain,and of course, fighter jets and so onwill experience G loadingof much higher than 3g,but that's for a relativelyshort amount of time.- So Bloodhound might be acceleratingas fast as a car can safely accelerate,and if it doesn't have thespace to reach its top speed,they've gotta find a new spot.Literally the land speed recordis determined by the earth.That's the limiting factor.The initial goal when weset out on all of thisover a decade ago, the design briefwas what does a 1000 mileper hour car look like?You know, we still don't knowin reality if that is possible,but we believe in principleBloodhound has the potentialto go at that sort of speed.- But will it?I mean, I don't know, I don't think so.I'm sure that the Bloodhound teamthey're gonna get close to it.I really hope they do.Big thanks to Dr. Ben Evansfor taking the time to speak with us.Maybe we'll put up anextended cut of that interviewfor all of our DonutUnderground followers.By the way if you're interestedin where we got our liquid horse juice,I followed a horse around for a long time.Until next week.Bye for now.(upbeat music)