The Bloodhound Gang: PH Meets

With final assembly underway, PH catches up on progress with the Bloodhound SSC project

Forget the Land Speed Record for a moment; the all-comers international crown for cool understatement, and the solidity of brass trouser furniture, must belong to Andy Green. The man who broke the sound barrier in Thrust SSC back in 1997 will also be piloting Bloodhound, with a jet-and-rocket powertrain that's aiming to break the 1000mph barrier. But while Green admits that he's taking a journey into the unknown, he does a very good impression of being unconcerned about the risks implicit in travelling fast enough to cover a mile in 3.5 seconds.

800mph is the target for 2015

When pressed he does admit to having one concern - his hearing. Bloodhound's cockpit is positioned directly below the air intake for the Rolls-Royce EJ200 jet engine that, despite delivering 4.8 tonnes of thrust, represents the less powerful part of the car's powertrain. And because this is operating in far denser air than it was designed to at these speeds, it's necessary to slow the incoming charge down to less than 600mph if the engine is to safely digest it; deceleration that is going to be happening just a couple of feet above Green's head.

"It's going to be a very, very high energy experience for the air," he says, with the sort of understatement you'd expect from an RAF fast jet pilot, "the cockpit will be the noisiest place on the planet, pretty much - certainly the noisiest place I will have ever experienced."

Which is why, as well as hopefully being the fastest car in the world, Bloodhound will also be carrying the most sound insulation.

You've almost certainly heard of the Bloodhound project, which has been going for several years. But it's about to grab the world's attention in a big way. Final assembly of the car is well underway in the team's industrial unit in Avonmouth - hence the invitation for PH to come and meet the team - with the chassis nearly complete and the jet engine installed. Shakedown testing is scheduled to start in May at Newquay airport, with the car travelling at speeds of up to around 200mph while wearing a set of wheels fitted with tyres from a Cold War era Gloster Meteor. And then the team will travel to South Africa, and a specially prepared 12-mile long course on the Hakskeen Pan, a natural salt flat. The target is to break the existing 763mph record this year, pushing it to around 800mph, before returning next year with a more powerful car that will target 1000mph. So not lacking in ambition, then.

The Land Speed Record has always been a British obsession, with UK drivers having held it for nearly two-thirds of the time since the first recognised one was set in 1898 (by a Frenchman in an electric car, at a spectacular 39mph.) But as the speeds have climbed so the challenge of going faster has risen too. Designing and building a car capable of going faster than 763mph has taken huge engineering effort, with the arrival of rocket power to provide the extra performance.

That's right, in addition to the EJ200 - which is a prototype unit with just 20 hours of rated life left in it - Bloodhound will use Norwegian made NAMMO solid rocket motors, which have been designed to dramatically cut the cost of launching smaller payloads into space. A single one will be used for the 800mph and then a cluster of three for the 1000mph runs - necessary as drag increases at the square root of speed. There's not enough oxygen in the atmosphere for the NAMMOs so they will be fed oxidizer in the form of high-test peroxide by a high-speed pump powered by a 5.0-litre supercharged Jaguar V8. Total output is 21.5 tonnes of thrust - equivalent to 135,000hp. That's enough, in theory, to push Bloodhound from rest to the 1000mph record in just 55 seconds.

Like the stats, the physics are mind-bending. Even designing wheels capable of handing such loadings has been a huge challenge - Bloodhound will ride on solid alloy wheels which will be rotating at 10,200mph at 1000mph, putting a force of 50,000G on the outer rims. At least they'll allow Bloodhound to be steered from the front - Thrust's twin-jet engine configuration meant that it had rear-steering, which Green remembers as being "a silly idea - it's actually unstable, which isn't something you want at supersonic speeds. When you look at the theory there's a reason it's limited to fork-lift trucks." But the relationship of the aluminium wheels with the salt surface - which has been hand-cleared of rocks over a three-year period - will vary dramatically according to speed.

"As we go faster tiny steering inputs will develop large shockwave symmetries and generate aerodynamic forces," Green explains, "tiny inputs will produce very dramatic effects. At 200mph the steering is mundane - it will feel like driving on snow - at 300 to 400 it will be all over the place and by 700mph it will be super responsive. All this happening in about 25 to 30 seconds." Green spent last season racing Radicals to help him hone his sense of the balance of the car.

Despite the rear fin and wings, all steering will be done by the wheels - the rear aero is there to keep the car stable and to trim it to deliver zero lift. Braking will also be done mostly through air resistance. "Just killing the engines at 1000mph will produce 3G deceleration," says Green, "that's losing 60mph per second - what most people would regard as a crash." Below 800mph air brakes can be deployed, with the further reassurance of two parachutes and then - below 200mph - carbon fibre discs to stop the car next to the 'turnaround crew'. FIA rules on the Land Speed Record mean that runs have to be completed through a measured mile in opposite directions within one hour, meaning it needs to be replenished with 500kg of jet fuel, 1000kg of high test peroxide, petrol for the V8 and to have the solid rocket fuel capsules replaced, plus a full inspection.

Braking is important - "it's the only non-optional bit," says Green, but it's also likely to be the main barrier to preventing the Land Speed Record from climbing much further.

"The biggest factor against going faster is the time it takes to slow the car down," explains Mark Chapman, Bloodhound's Chief Engineer. "It's easy in principle to put a bigger rocket on and to accelerate faster, to go quicker and quicker. The problem is that you are relying on aerodynamics to slow the car down, meaning there's a limit on how much car you can open up to achieve that. It's not a problem if you have an infinite length of track, but in Hakskeen Pan we've found what we think is the largest suitable surface in the world, and we've only got 20km to play with. Yes, in theory, you could go quicker - there is always a bigger rocket engine. But that's going to give you more and more problems when it comes to slowing down at the end."

The atmosphere inside the Avonmouth workshop is so calm and British that you can almost forget what a ground-breaking project is happening here. Unlike previous LSR attempts the Bloodhound project is being run professionally, with a (mostly) paid team. Its official role is to inspire a new generation of engineers - it's the largest STEM (Science, Technology, Engineering and Mathematics) outreach programme in the world, with the plan being to livestream all of the runs and record attempts, both in terms of video feeds but also fully shared data from the 500 telemetry channels - from air pressures and exhaust temperatures through to Green's heart rate. Even the blueprints for the car are available to download online.

"There's no point hiding anything, it's not like we're trying to maintain a technical advantage here like in racing," says Chapman, "we're not like Red Bull looking at Mercedes, or Airbus looking at Boeing - we're running into challenges we're the first people ever to face. There isn't a book on Supersonic Car Design For Beginners. That doesn't exist - if anything, we're writing it."

[Images: Stefan Marjoram, via Flickr, renderings from Bloodhound by Flock and Siemens]

OP Posts Only

Prev 2 Next

OP Posts Only

Author

Discussion

antoinettelocket

Original Poster

6 posts

108 months