The Brakes That Stop a 1,000 MPH Bloodhound SSC 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."
Killowatts are power, not energy (Score:4, Informative)
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 (Score:2, Informative)
Friction brakes, that's unusual (Score:5, Informative)
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.
Re:FLAPS! (Score:5, Informative)
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.
Re:not a car (Score:2, Informative)
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:Killowatts are power, not energy (Score:5, Informative)
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:Stronger? (Score:5, Informative)
Re:not a car (Score:4, Informative)
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.
Embarrassing to who? The team? Steam engine builders local 402 circa 1897? Humanity? The fact that the Land Speed World Record is what it is for a steam engine means that it might be harder than it looks. Now if society had spent hundreds of $billions over the past century optimizing the steam engine like they have the ICE, you might have a point. From the site you listed:
"No one is going to suggest that this vehicle represents a major technical breakthrough, a relatively small improvement has been won at a cost of enormous complexity but it is unquestionably a triumph of determination, persistence and absolute refusal to give up in the face of adversity. Does it exemplify the "spirit of adventure"? Unquestionably!"
Good on them. I don't know about you but I don't have any world records to my name. I also never thought I'd get so fired up (no pun intended) defending a steam engine...
Re:Killowatts are power, not energy (Score:3, Informative)
The problem was that, even though they don't use the brakes at high speeds, those break disks are still on the wheels and spinning at whatever speed the wheels are spinning at, for the entire duration of the run. And apparently just that centrifugal force was enough to shatter carbon brakes. Vibrations at 1000 mph over desert ground certainly didn't help either.