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The Brakes That Stop a 1,000 MPH Bloodhound SSC

Soulskill posted about 2 months ago | from the stop-speed-racer-stop dept.

Transportation 262

cartechboy writes: "The problem: How do you stop the 1,000 mph Bloodhound SSC? The solution: Apparently you use steel rotors from AP Racing, which managed to absorb 4.6 kilowatts of energy on a test stand without failing although the Bloodhound team hasn't spun them up to the full 10,000 rpm just yet. During testing, a set of carbon rotors from a jet fighter shattered under the stress during a half-speed, 5,000-rpm test, thus the team switched to steel rotors. It's like stopping a bus from 160 mph on a wet road. That's how the engineers behind the Bloodhound SSC—the British land-speed record car designed to break the 1,000-mph barrier—described the task of stopping their creation once it's finished breaking the sound barrier. We'll have to wait to see if the steel rotors can handle the full 10,000 rpm run, but until then, it looks like steel is stronger than carbon when it comes to some instances."

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262 comments

4.6 kilowatts of energy (0)

Anonymous Coward | about 2 months ago | (#47058153)

hey asshole, that's power, not energy...

Re:4.6 kilowatts of energy (1)

Anonymous Coward | about 2 months ago | (#47058303)

It was a typo. It was suppose to say "4.6 jiggawatts"

Re: 4.6 kilowatts of energy (0)

Anonymous Coward | about 2 months ago | (#47058979)

Jigga who?

Killowatts are power, not energy (3, Informative)

YesIAmAScript (886271) | about 2 months ago | (#47058155)

And 4.6kW isn't that much power anyway. About 60HP.

I've seen resistor boxes used for testing EVSEs that take 6.6kW and of course don't fail.

Re:Killowatts are power, not energy (-1)

Anonymous Coward | about 2 months ago | (#47058367)

1) power is energy

2) 4.6kW, is about 6HP, not 60HP.

Re:Killowatts are power, not energy (1)

Anonymous Coward | about 2 months ago | (#47058437)

Power is energy over time.

Re:Killowatts are power, not energy (2, Informative)

Anonymous Coward | about 2 months ago | (#47058455)

Power is energy per time. But 6HP is correct.

Re:Killowatts are power, not energy (1)

hackertourist (2202674) | about 2 months ago | (#47058639)

Brakes on ordinary cars are typically several times more powerful than the car's engine, so we're talking about several hundred kW of available braking power for an ordinary saloon. On one hand, Bloodhound is a 6-ton machine going 250 km/h when the brakes are applied which would suggest the figure needs to be higher than that. On the other hand, it'll have far less grip than rubber tires on tarmac can generate so it's not the maximum power dissipation that counts.

Re:Killowatts are power, not energy (0)

harrkev (623093) | about 2 months ago | (#47058967)

At hundreds of miles per hour, the car aerodynamics would probably be closer to an aircraft. Why not use some sort of air brake -- little flaps that stick out causing wind resistance? Once you get down to, say, 300 MPH, there are certainly commercial car brakes that can handle that -- NASCAR does it every day.

Re:Killowatts are power, not energy (2)

Connie_Lingus (317691) | about 2 months ago | (#47059163)

watch TFV...

it clearly states that air brakes will slow the machine from 1000mph to 160mph and the brakes are simply used for fine-tuning the stop location.

Re:Killowatts are power, not energy (5, Informative)

hackertourist (2202674) | about 2 months ago | (#47059261)

As others have said, Bloodhound already uses airbrakes for higher speeds. The disk brakes are used when the airbrakes become ineffective at lower speeds.
NASCAR is 200 mph, not 300 (and 1/4 the weight). And NASCAR brakes don't have to survive rotating at 1600 km/h. At that speed, the centrifugal force is more than most materials can handle. Bloodhound's wheels are some of the biggest engineering challenges in the project, they have to withstand something like 50,000 G. The brakes are a bit easier because they're smaller, but still a major problem.

Re:Killowatts are power, not energy (0)

Anonymous Coward | about 2 months ago | (#47058999)

I've seen resistor boxes used for testing EVSEs that take 6.6kW and of course don't fail.

AKA, space heaters? 6.6kW is nothing.

http://www.sciencedirect.com/s... [sciencedirect.com]

In accordance with the ITER specifications this switch will be used for continuous operation with DC currents up to 70 kA and shall be capable, on command, to transfer this current to a resistive load under a voltage up to 10 kV in less than 1 ms.

So, we are talking about an *impulse* of about 700TW... or 700,000,000kW for metric impaired.

Stronger? (1)

hubie (108345) | about 2 months ago | (#47058159)

If I had to guess, it isn't that steel is stronger in this case, but better at heat conduction/dissipation.

Re:Stronger? (1)

Drethon (1445051) | about 2 months ago | (#47058251)

If heat is a problem, it seems like regenerative breaking could be a better option.

Re:Stronger? (0)

Anonymous Coward | about 2 months ago | (#47058275)

Um, what? Regenerate into what? The SSC isn't exactly a battery-powered car, is it?

Red Lectroids drool! (3, Insightful)

Thud457 (234763) | about 2 months ago | (#47058489)

pish, the obvious design is to dump the energy into the oscillation overthruster. That way you don't have sudden deceleration when you collide with the mountain.

Re:Stronger? (1)

holmstar (1388267) | about 2 months ago | (#47058757)

Why not just dump the electricity into a resistive coil? No need to store it.

Re:Stronger? (1)

Bartles (1198017) | about 2 months ago | (#47059071)

Does it just sit in there until someone lets it out? You're dumping enough energy to get a car up to 1000mph hour into a coil. That coil better be very large, and have a huge heatsink or you're going to have a fire.

Re:Stronger? (1)

gl4ss (559668) | about 2 months ago | (#47059121)

have it melt some stuff in a crucible? or what?
or launch the energy as emf?

Re:Stronger? (2)

NatasRevol (731260) | about 2 months ago | (#47059219)

A freaking lightning bolt coming out of the tail as it slows would be spectacular.

Re:Stronger? (-1, Flamebait)

Anonymous Coward | about 2 months ago | (#47058327)

If heat is a problem, it seems like regenerative breaking could be a better option.

1) Shut the FUCK up and learn to spell. Breaking is not braking, you stupid fuck.

2) After you learn to spell, kill yourself. It will be the most noble act you can ever perform.

Re:Stronger? (0)

Drethon (1445051) | about 2 months ago | (#47058465)

After you good sir.

Re:Stronger? (2)

The Grim Reefer (1162755) | about 2 months ago | (#47058359)

If heat is a problem, it seems like regenerative breaking could be a better option.

It's a jet and rocket powered car. How are you going to regenerate those with brakes? How much weight will they add? And finally, have regenerative brakes been built that would even be practical at 10K RPM?

Re:Stronger? (1)

Anonymous Coward | about 2 months ago | (#47058529)

When the brake pedal (or control or whatever) is pushed, redirect the jet / rocket exhaust out the front and accelerate in the opposite direction. It is just force vectors. You might need some ablative shield on the front where the exhaust exits. Sure, there will be some amount of loss as you do this (with a U shaped pipe or whatever) and it will need to handle the heat, but should prove more robust than exploding brakes.

Re:Stronger? (2)

The Grim Reefer (1162755) | about 2 months ago | (#47059021)

When the brake pedal (or control or whatever) is pushed, redirect the jet / rocket exhaust out the front and accelerate in the opposite direction. It is just force vectors. You might need some ablative shield on the front where the exhaust exits. Sure, there will be some amount of loss as you do this (with a U shaped pipe or whatever) and it will need to handle the heat, but should prove more robust than exploding brakes.

Uh huh. While that sounds great in theory, you need to keep in mind this is a 1000 mph land vehicle. What happens if at full speed the redirected thrust doesn't function quite right? At best the pilot/driver will need to change his/her underwear. Worst case he/she has to be hosed out of what is left of the car as it will become one fast moving uncontrollable centrifuge of death.

Steel rotors may not be elegant, but they are also fairly simple and we've understood the tech for a long time. I think I'd prefer a drag chute and rotors over some vectored thrust contraption. It's not like they are going to be doing continuous laps in this thing. Plus they won't need to entirely redesign the vehicle to accommodate a bunch of duct work and heat shielding.

Re:Stronger? (2)

xaxa (988988) | about 2 months ago | (#47058667)

Possibly he's mistaken regenerative brakes for resistive/rheostatic brakes. On diesel-powered railway locomotives (which are almost always electric motors powered by a diesel generator) there's a bank of resistors. The motors are run as generators, the electricity put through the resistors and lost as heat: http://en.wikipedia.org/wiki/D... [wikipedia.org]

However, this vehicle doesn't have electric motors, so it's not applicable.

Re:Stronger? (0)

Anonymous Coward | about 2 months ago | (#47059015)

Possibly he's mistaken regenerative brakes for resistive/rheostatic brakes. On diesel-powered railway locomotives (which are almost always electric motors powered by a diesel generator) there's a bank of resistors. The motors are run as generators, the electricity put through the resistors and lost as heat.

The principle behind regenerative brakes is the same (use of an electric generator to slow down); the only difference is that the power output of the generator is put to a more useful purpose (charging a battery).

However, this vehicle doesn't have electric motors, so it's not applicable.

Using the drive motor as a generator is just convenient because it is already there; nobody's stopping you from adding braking generators to a system that does not use motors.

Nevertheless, 4.6kW is not a lot of power, easily handled by regular friction brakes. So the article doesn't really add up.

Re:Stronger? (-1)

Anonymous Coward | about 2 months ago | (#47058567)

Where are you thinking the recovered energy will go? The giant supersonic batteries?

Brainless EV greentards and their fantasy physics....

Re:Stronger? (1)

Drethon (1445051) | about 2 months ago | (#47058621)

Was thinking it could power internet egos, though I forgot they need far more energy.

Re:Stronger? (0)

Anonymous Coward | about 2 months ago | (#47058699)

Like the egos of people with no physics, mechanics or engineering backgrounds broadcasting their fecal ideas for everyone to see as if they're important?

Re:Stronger? (1)

Drethon (1445051) | about 2 months ago | (#47058841)

Well the more responses the more people might read what is being responded to. So I guess those responding think it is important for some reason.

Re: Stronger? (0)

Anonymous Coward | about 2 months ago | (#47058997)

Hey, I resemble that remark!

Re:Stronger? (1)

Bengie (1121981) | about 2 months ago | (#47058777)

Electric Heating coils, like what trains use.

Re:Stronger? (1)

Kielistic (1273232) | about 2 months ago | (#47059065)

I assure you that dumping waste energy as heat as in classical braking systems will be far more effective and robust than any "regenerative" system. If you are having heat dissipation problems you will likewise have overload problems anywhere else you try to direct that energy- along with heat dissipation problems. Although most likely your regenerative system would just be destroyed by the forces involved.

Watts is not energy (1)

Anonymous Coward | about 2 months ago | (#47058185)

4.6 kilowatts of energy

Kilowatts is a unit of power, not energy. Sheesh.

Aerodynamics (1)

Anonymous Coward | about 2 months ago | (#47058195)

I think aerodynamic drag, even without a parachute, will help out a lot with the stopping.

Re:Aerodynamics (1)

Ralph Wiggam (22354) | about 2 months ago | (#47058313)

I don't think any materials for the parachute or the shroud lines could handle the jolt of when it first opens at those speeds.

Re: Aerodynamics (1)

Anonymous Coward | about 2 months ago | (#47058469)

Sure it could, they're called ballistic parachutes. Trick is you don't just open the whole thing all at once, you might start with a small drogue or even a steamer. They also have devices designed to gradually open a chute. I agree though, I wonder why they don't think aerodynamic drag is enough. Hell, throw some speedbrakes on there like an airplane, they go these speeds all the time and don't have the luxury of landing in the salt flats.

Re: Aerodynamics (2)

KingOfBLASH (620432) | about 2 months ago | (#47058559)

Actually if your airplane is going 1,000 mph into your descent, you, sir, have a problem.

I don't know the top speed you can land, but I would bet it's not much more than 200mph....

Re:Aerodynamics (1)

gandhi_2 (1108023) | about 2 months ago | (#47058507)

So open it gradually.

Re:Aerodynamics (1)

jandrese (485) | about 2 months ago | (#47058557)

That's what I was thinking. Some smallish spoilers that can be extended out of the sides of the car would add a tremendous amount of braking power at 1000mph.

"it looks like steel is stronger than carbon" (1)

Anonymous Coward | about 2 months ago | (#47058199)

Um, duh? Materials science 101, chubs. But I guess when you have people talking about space elevators in all seriousness, you can't expect too much realism...

Steel is stronger than carbon in many instances (4, Interesting)

holophrastic (221104) | about 2 months ago | (#47058207)

I think people forget that "stronger" is meaningless. In the case of steel vs carbon, carbon is going to be stronger for a given weight, but that just makes the word "stronger" even more meaningless.

Steel usually wins out against most materials when it comes to survival. Steel bends, and bends back. Just about everything else loses by being brittle. Aluminum is the best example, being about three times lighter, but incredibly brittle. Carbon is also very brittle, just at the microscopic level. It'll fray, and slowly degrade until it comes a part -- like most fabrics.

Steel deforms, and then melts back together and deforms again. In order for friction to destroy steel, it needs to actually wear it away one particle at a time. Being so much heavier/denser, there are that many more particles to wear away. That's the win.

Why are people surprised when mass wins in a mass-bound effort? The challenge here is to get a heavy car to go really fast, and to then slow it down. That's always been a mass vs mass game. More mass always wins.

My question remains: if the carbon solution were as heavy as the steel solution, would it survive? But we all know that you can't cram that much carbon fibre into the same style of braking system.

Re:Steel is stronger than carbon in many instances (0, Troll)

Anonymous Coward | about 2 months ago | (#47058381)

Hey dipshit, "strength" is a precise term in materials science. Could you software clowns keep your autisitc yaps shut when you're out of your depth?

http://en.wikipedia.org/wiki/S... [wikipedia.org]

Fucking Asperger's nitwits who like the sound of their own "genius" voices. Shut the hell up moron.

"Being so much heavier/denser, there are that many more particles to wear away."

What the fuck does that even mean, nippledick?

Re:Steel is stronger than carbon in many instances (0)

Anonymous Coward | about 2 months ago | (#47058631)

hey dipshit, insulting other people for describing things in a way that makes sense to them just makes you look like a fucken retard. Grow up

Re:Steel is stronger than carbon in many instances (2)

holophrastic (221104) | about 2 months ago | (#47058905)

Umm, whatever your industry's definition of "strength", you'll find that it morphs across the three disciplines involved here. You'll also note that your own industry's definition of "strength" doesn't distinguish between various directions. So if I were to say that steel is stronger laterally, vs carbon's strength longitudinally, I'd still be within your industry.

Your industry also flexes in terms of the definition of the term "failure under load". Failure in some instances means breaking under the stress applied, but in others in means breaking as a result of the stress applied. In this case, we're talking about a spinning disk. If the material can withstand the load without the spinning, but then breaks due to the spinning, the term "strength" either does or does not cover the actual environment being discussed.

All of that aside, you'll note that this is not a materials sciences web-site, nor is it a theorhetical sciences journal. It is a site specifically for autistic yaps who make billions of dollars by transforming complicated depths into familiar fundamentals.

So why are you here?

Re:Steel is stronger than carbon in many instances (0)

Anonymous Coward | about 2 months ago | (#47058445)

But we all know that you can't cram that much carbon fibre into the same style of braking system.

carbon brakes are not actually carbon fiber, but graphite-like. http://en.wikipedia.org/wiki/Reinforced_carbon%E2%80%93carbon

Re:Steel is stronger than carbon in many instances (1)

holophrastic (221104) | about 2 months ago | (#47058935)

oops, my mistake. I didn't mean to type fibre. Thanks!

you know not what you speak of (5, Insightful)

SuperBanana (662181) | about 2 months ago | (#47058599)

Steel bends, and bends back. Aluminum is the best example, being about three times lighter, but incredibly brittle. Carbon is also very brittle, just at the microscopic level. It'll fray, and slowly degrade until it comes a part -- like most fabrics.

I'm sorry, but you know not what you speak. Aluminum is used on millions of planes for, what, almost a century? There are very malleable forms of steel (like the springs in your car) and very brittle forms of steel (like some kitchen knives.) Go and look at the carbon fiber wings on thousands upon thousands of aircraft.

Go look at the carbon fiber rear seat/chain stays and front forks on millions of bicycles.

People commonly attribute specific qualities to broad material categories like "steel" or "aluminum" like you just did, which is completely ignorant of the fact that all these materials can be engineered for different properties.

Carbon fiber is the most engineer-able material available, just about. Choosing a fighter jet part was pretty stupid, given it was engineered for weight, very occasional use, and lots of airflow, etc. They could almost certainly have a proper ceramic rotor designed for them, but it's probably too expensive or they got sponsorship with AP (given the article etc. this seems likely.)

Re:you know not what you speak of (1)

Bengie (1121981) | about 2 months ago | (#47058851)

Airplanes need to use very special flexible joints because Aluminum is so brittle. Aluminum becomes very weak very fast when it flexes to the point of being deformed. Steel, not so much, unless you put a ton of carbon in it.

He was correct when it comes to the general properties of steel, but not all cases.

Re:you know not what you speak of (1)

bluefoxlucid (723572) | about 2 months ago | (#47058887)

You can use brittle materials on airplanes. Some airplanes are carbon fiber framed.

Re:you know not what you speak of (1)

holophrastic (221104) | about 2 months ago | (#47058989)

I find it interesting to note that all of your examples are of structural, non-frictional components, which doesn't really apply here. I'd have argued that while most metals are readily engineered for differing properties, 90% of those efforts fail miserably in frictional, high-heat, high-wear applications, where the base material undergoes chemically-significant physical forces -- like friction.

In any event, my comments were not intended to describe all steel and all carbon. Instead they were meant to describe the steel and carbon being used in the report. I don't really care about any others in this thread.

On the other hand, if you'd like to get into my personal experiences with aluminum on hang gliders, or my professional expreiences with aluminums and steels in commercial environments, or my pseudo-professional experiences with aluminums, steels, and irons in kitchen environments, my knowledge is narrow but deep in the first, broad and deep in the second, broad and shallow in the third.

Re:Steel is stronger than carbon in many instances (1)

holmstar (1388267) | about 2 months ago | (#47058915)

In order for friction to destroy steel, it needs to actually wear it away one particle at a time. Being so much heavier/denser, there are that many more particles to wear away.

Or, you know, heat it up so much that it starts to melt. That's a real possibility for this application. A previous poster suggested rheostatic brakes (basically regenerative braking, where the electricity is dumped into a big resistor instead of being stored for later use). It would add weight and complexity, but if regular brake disks can't dissipate the energy fast enough, then something like that might be necessary.

Re:Steel is stronger than carbon in many instances (1)

LordLimecat (1103839) | about 2 months ago | (#47059251)

That's always been a mass vs mass game. More mass always wins.

So, lead brakes then.

The solution (5, Funny)

cdrudge (68377) | about 2 months ago | (#47058223)

The problem: How do you stop the 1,000 mph Bloodhound SSC?

Friction brake, electromechanical brake, eddy current brake, drogue parachute, inclined plane, arrester bed, rubber bands, brick/stone wall, etc. You'd think engineers would have been able to think of these things...

If they use a really long bungee cord not only could they use it to brake the vehicle at the end of one run, but use it for initial acceleration on the return run too!

Re:The solution (5, Funny)

NotDrWho (3543773) | about 2 months ago | (#47058349)

They tested the brick wall stopping method. It did not end well.

Re:The solution (2)

cdrudge (68377) | about 2 months ago | (#47058399)

But it stopped. And depending on the thickness of the wall and size of the subsequent debris field, it probably stopped it the quickest compared to other methods. Subsequent runs became much more difficult though.

Re:The solution (4, Funny)

EvilSS (557649) | about 2 months ago | (#47058963)

But it stopped. And depending on the thickness of the wall and size of the subsequent debris field, it probably stopped it the quickest compared to other methods. Subsequent runs became much more difficult though.

Yes, the problem was cost. Using the brick wall meant that all parts of the car, including the driver, were single use only. They at least need the car to be reusable. Driver optionally so.

Re:The solution (1)

MiniMike (234881) | about 2 months ago | (#47058869)

I heard that they were actually mortarfied with the results...

Re:The solution (1)

bswarm (2540294) | about 2 months ago | (#47058387)

You forgot to include a boat anchor.

Re:The solution (1)

Charliemopps (1157495) | about 2 months ago | (#47058881)

Right, that's the first thing I thought of. This is an incredibly stupid way to stop a high speed vehicle. They're going to have to replace those things every run.

Many moons ago I worked for a bicycle company building bikes for the Olympics down-hill racing team that year. (yes, I've had every weird job you can think f if you follow my posts at all.) Those breaks and wheels had to be replaced after 2 runs, and cost $800 per set.

I suspect whats happening here is some sort of endorsement. Their putting their driver at risk in exchange for investment. Hopefully they have a backup chute in case these silly brakes fail.

Re: The solution (0)

Anonymous Coward | about 2 months ago | (#47059211)

From the summary, they will be using a parachute for most of the stopping power - the land brakes just have to take over from about 160 MPH. That is probably around the speed where their car's parachute isn't catching enough air to be all that useful anymore. Remember, they have to deploy the parachute at around 1000 MPH, and it has to grab just enough air at that speed to slow them down without totally ripping away from the car. At relatively slow speeds, that same parachute won't grab enough air to slow you down much further.

Kilowatts per ...? (0)

Anonymous Coward | about 2 months ago | (#47058305)

Second, minute, hour, century??

I've got lightbulbs absorbing more than 4,6kW...

Re:Kilowatts per ...? (1)

Russ1642 (1087959) | about 2 months ago | (#47058343)

Killowatts per parsec. Something, something, Kessel Run.

Journalism students attempting technical reporting (2)

mpoulton (689851) | about 2 months ago | (#47058309)

4.6kW, eh? That's 6.2 horsepower. I'm gonna go out on a limb and say that number is wrong by several orders of magnitude. 4.6MW is more likely.

Why no parachute? (1)

kruach aum (1934852) | about 2 months ago | (#47058325)

Why don't they just invest in strong ropes, good bolts and a parachute, like literally every other rocket car?

Re:Why no parachute? (0)

Anonymous Coward | about 2 months ago | (#47059001)

They do have parachutes. And air brakes. But they also need to have wheel brakes.

dom

It's a monster (5, Interesting)

Ralph Wiggam (22354) | about 2 months ago | (#47058351)

My favorite thing about the Bloodhound SSC is that it uses a 4.2L V12 engine producing 750bhp...to run its fuel pump.

Re:It's a monster (2)

njnnja (2833511) | about 2 months ago | (#47058541)

Slight correction - it's a 2.4L [bloodhoundssc.com] engine...to run the fuel pump.

Re:It's a monster (1)

Russ1642 (1087959) | about 2 months ago | (#47058771)

Also it's a V8 not V12.

Re:It's a monster (1)

Threni (635302) | about 2 months ago | (#47059201)

So you're saying it's pretty much just a souped up Ford Cortina...

Re:It's a monster (3, Funny)

KingOfBLASH (620432) | about 2 months ago | (#47058547)

Hey! You should label posts like that NSFW. I just creamed my pants at an inopportune time.

Re:It's a monster (1)

EvilSS (557649) | about 2 months ago | (#47058995)

My favorite thing about the Bloodhound SSC is that it uses a 4.2L V12 engine producing 750bhp...to run its fuel pump.

Even with the subsequent corrections, that actually is very cool.

Who needs brakes? (4, Funny)

macraig (621737) | about 2 months ago | (#47058363)

Why not just skip the brakes, save the money, and eject the driver/pilot and let the sucker crash and burn? Could be an awesomely popular YouTube video.

Re:Who needs brakes? (2)

l0ungeb0y (442022) | about 2 months ago | (#47058521)

Because then they wouldn't have a shiny vehicle to send on world tour as a money making exhibit

Re:Who needs brakes? (1)

Drethon (1445051) | about 2 months ago | (#47058537)

As many hits as that YouTube video would get, I don't think it will pay for the replacement.

Re:Who needs brakes? (0)

Anonymous Coward | about 2 months ago | (#47059243)

You must have looked at the latest hits -> real dollars exchange rate. But you forgot the hits -> internet dollars -> bitcoin -> WoW Gold -> EVE ISK -> real dollars route. I wish that chain could have been longer but that is all I could come up with off the top of my head. CAPTCHA is, fittingly, unending.

Re:Who needs brakes? (0)

Anonymous Coward | about 2 months ago | (#47058583)

Why does it have to crash and burn? Australia is a big place, let it coast to a stop.

Re:Who needs brakes? (0)

Anonymous Coward | about 2 months ago | (#47058633)

More awesomely cool...put a ramp at the end of the run. The car gains altitude (for safer ejection height for the driver) AND sets new world record for highest altitude reached by a ground vehicle.

Re:Who needs brakes? (2)

jklovanc (1603149) | about 2 months ago | (#47058701)

Because the land speed record [wikipedia.org] requires you to run in both directions in the same vehicle within an hour.

The record is standardized as the speed over a course of fixed length, averaged over two runs (commonly called "passes"). Two runs are required in opposite directions within one hour, and a new record mark must exceed the previous one by at least one percent to be validated.

Re:Who needs brakes? (4, Funny)

jovius (974690) | about 2 months ago | (#47058853)

I suggest they build wings to that machine. A machine of that size would be easily lifted from the ground at even lower speed than 1000 mp/h. There's less friction higher in the air anyway and they could reach speeds well exceeding 1000 mp/h. The team seems to be stuck with the car paradigm which is already well over 100 years old. I believe that humans will be able to fly with the aid of modern technology. All it needs is a change in thinking, an evolution of mind.

Re:Who needs brakes? (0)

Anonymous Coward | about 2 months ago | (#47059127)

It seems that the land speed record would require the vehicle to actually remain on the land the whole time. If they wanted to break a speed record for a vehicle in the air, they need to hit way more than 1000 mph!

dom

Re:Who needs brakes? (1)

LordLimecat (1103839) | about 2 months ago | (#47059281)

I might be wrong, but my middle school level of physics leads me to believe that would not solve the problem of the pilot's forward momentum.

not a car (5, Insightful)

deadweight (681827) | about 2 months ago | (#47058421)

IMHO these are not cars and the records are fairly meaningless. It is a low flying aircraft being precisely controlled to keep the landing gear down on the runway. Don't believe me - watch what happens if the design is wrong. it will definitely be flying and not in a good way.

Re:not a car (0)

Anonymous Coward | about 2 months ago | (#47058589)

Agreed. But it would be equally impressive if a jet could reach 1000 mph while remaining in contact with the ground (without catastrophic failure)...

Re:not a car (1, Informative)

Animats (122034) | about 2 months ago | (#47058731)

Right. There are wheel-driven land speed records [wikipedia.org] , currently 470.444 MPH with a turboshaft engine, 462 MPH with a piston engine, 307.666 with an electric motor, and 139.843 MPH with a steam turbine.

The 139.843 MPH steam speed record was set in 2009, by a British team [steamcar.co.uk] . This is embarassingly low for a custom-built steam turbine powered land speed record car that looks like an aircraft. They brought the car out to the salt flats at Edwards for this.

Re:not a car (1)

operagost (62405) | about 2 months ago | (#47059231)

The thing with the steam engine is that it produces insane amounts of torque, when HP is what we need for top speed. Jay Leno described it as the "hand of God pushing you along".

Re:not a car (1)

Russ1642 (1087959) | about 2 months ago | (#47058799)

Lots of wheel powered cars can take-off if something upsets them.

Friction brakes, that's unusual (5, Informative)

GameboyRMH (1153867) | about 2 months ago | (#47058551)

Very high-end landspeed cars usually use eddy current brakes [wikipedia.org] and only have friction brakes for coming to a complete stop.

More "mundane" (like up to 700kph) landspeed cars use conventional friction brakes - after parachutes have done most of the work of course.

FLAPS! (2)

TheRealSteveDallas (2505582) | about 2 months ago | (#47058569)

Why aren't they using analog flaps to gradually increase drag? At 1000mph you will decelerate pretty quickly by just not applying thrust. Other aircraft can slow down pretty well using them and they don't have the friction of maintaining contact with the ground to help. Bonus for using the same flaps to increase downforce as they open so the mechanical brakes will work better or just deploy a dragster chute once you get below the operating envelope.

Re:FLAPS! (5, Informative)

GameboyRMH (1153867) | about 2 months ago | (#47058617)

You don't want downforce on a landspeed car, adding downforce is almost like dragging the brakes as far as they're concerned. Also air brakes make the vehicle they're attached to squirm around a little - not a problem on a fighter jet or a supercar, but a big problem on a vehicle travelling at speeds you don't want to be on the ground for and that can't turn worth a damn at any speed.

I'm sure it already uses a parachute. Usually these kinds of cars use eddy current brakes to slow to the point that the chutes can be opened, then after the parachutes have done most of their work they use conventional friction brakes to come to a complete stop.

Serial parachutes (1)

Jim Sadler (3430529) | about 2 months ago | (#47058683)

Why not a small, strong parachute to start the slowing followed by progressively larger parachutes? If we are considering only brake shoes or pads then I would think ceramic with some embedded metal pieces might be the way to go. If pre-warmed the ceramic should hold together nicely.

SSC? (0)

Anonymous Coward | about 2 months ago | (#47058809)

Superconducting Super Collider ?

parachutes or water-cooled rotors (1)

redelm (54142) | about 2 months ago | (#47058819)

Traditionally, parachutes (strictly, drogue chutes) are used from these speeds. Other drag increasers (flaps) would also work. So would shutting off the motive force!

If you insist upon friction brakes, then you know you'll have a problem with heat removal. For that, water is best. Either pumped supply or static fill, just let the steam blow out of hub-wards pressure valves at 15-100 psig on hollow rotors..

Time unit (2)

g8oz (144003) | about 2 months ago | (#47058847)

"managed to absorb 4.6 kilowatts of energy"......per what? The number is meaningless without a unit of time.

Re:Time unit (1)

wonkey_monkey (2592601) | about 2 months ago | (#47058965)

The same as is the case with this gem?

It's like stopping a bus from 160 mph on a wet road

which is probably relatively easy if you're given 5 minutes to do it.

Re:Time unit (0)

Anonymous Coward | about 2 months ago | (#47059151)

A Kilowatt does imply a time unit. 1 Watt = 1 joule per second, 1 kilowatt = 1000 joules per second.

SSC? (2)

Geoffrey.landis (926948) | about 2 months ago | (#47059025)

http://www.acronymfinder.com/S... [acronymfinder.com]

Couldn't they mention what they are talking about in the first sentence or two of the summary?

Brakes are for low speed deceleration (0)

Anonymous Coward | about 2 months ago | (#47059113)

If you watch the video on one of the pages linked in the post, they say explicitly that they use drag from airbrakes to slow from 1000mph, and that the steel brakes will only be used to slow from 160mph to a stop near the recovery team. They're just using the steel brakes because they'll (presumably) tolerate being spun at 10000rpm, whereas the carbon brakes disintegrated. Also, the brakes don't need much stopping power because the contact patches of the wheels is tiny on the desert floor; you can add huge brakes, but they'll just lock the wheels up and you'll lose control.

I'm guessing the sequence will be airbrakes at 1000mph --> parachute at 300-350mph (this is what was used on the last record car) --> wheel brakes for final stopping.

steel is stronger than carbon... (1)

DeTech (2589785) | about 2 months ago | (#47059169)

A better way to make the comparison would be to say, "steel is a better material choice in this application".
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