The Blog


Andy Green_ Autosport 2012_2 [pic credit Stefan Marjoram]
Andy Green at the Bloodhound SSC

A British team is developing a car that will capable of reaching 1,000mph (1,610km/h) at Hakskeenpan in the Northern Cape. Powered by a rocket bolted to a Eurofighter-Typhoon jet engine, the Bloodhound SSC (SuperSonic Car) vehicle will mount an assault on the land speed record. Wing Commander Andy Green is writing a diary about his experiences working on the Bloodhound project and the team’s efforts to inspire national interest in science and engineering.

Earlier this month I was speaking to a British Airways audience at their annual flight safety day.  My aim was to tell them how we set the first-ever supersonic record back in 1997, with Thrust SSC, and to talk about how we planned to get to 1000 mph with BLOODHOUND, safely.  It was also a useful chance for us to show our homework to a group of industry safety specialists – in this case 200 commercial pilots and aircraft engineers.  If there is something that we haven’t thought of yet, they will find it!  From my point of view, this is one of the great strengths of Project BLOOODHOUND.  The more expert advice we have, the more confident we can be that we’re going in the right direction.

BLOODHOUND-CFD-Oblique-view

Aerodynamics on Bloodhound SSC

As I told the BA group, the requirements for a safe Land Speed Record are really very simple:

  1. Keep the Car shiny side up.
  2. Stop before the end of the track.

Keeping the Car shiny side up is primarily an aerodynamic problem and, after 6 years of research, we remain confident about the shape that we’ve developed.  Our aerodynamics engineer Ben Evans gives a great summary of this 6 year marathon in ‘The Path to Predictability’.  As he points out, we’ll be testing the aerodynamics on every run, and only going faster when we know that the Car will stay on the ground.

Stopping the Car is slightly different.  For the whole time that the Car is accelerating, I can always throttle back if something doesn’t look right: more speed is always optional.  However, when the Car comes bursting out of the measured mile at over 1000 mph, slowing down before the end of the track has just become compulsory.  The end of the track may be 5.5 miles away, but the Car is doing a mile every 3.6 seconds, so that’s really not very far…..

Getting this bit right is so important that BLOODHOUND, uniquely, has 3 different options for stopping.  The first is jet fighter-style airbrakes, which can be deployed gradually from 800 mph.  Alternatively (or if there’s a problem), we’ve got a brake parachute that will generate about 9 tonnes of drag at 670 mph.  And if there’s a problem with the chute, then we’ve got a second identical brake chute, just in case.

BLOODHOUND-SSC-Airbrake-Mechanism

Airbrake Mechanism on Bloodhound SSC

The airbrake mechanism is squeezed under the jet engine.  Clearly both sides must deploy at the same rate, otherwise I will rapidly be going round in circles.  Twin hydraulic pistons drive a single slider plate, which in turn is connected to both airbrake doors so that both move together.  If that is difficult to picture, then have a quick look at the airbrake animation on the BLOODHOUND website.

Thanks to another great piece of work by URT, the finished slider has just been delivered to our Technical Centre in Bristol.  Want to come down and see it for yourself?  Join our 1K Supporters’ Club and we’ll invite you down for one of our open days.

Key to stopping the Car from 800 mph with the airbrakes is getting them to deploy at the right rate.  Too fast, and we’ll overstress and damage the doors.  Too slow and we won’t stop quickly enough.  In addition, they need to be ‘fail safe’ – in other words, if we lose electrical or hydraulic power on the Car, then the airbrakes need to deploy automatically (because slowing down is still compulsory, even if you’ve got problems).

This is where Parker Hannafin comes in.  We’ve just received 3 hydraulic control blocks from Parker, which will take care of the airbrake deployment, at the right rate, with or without power. One less thing to worry about.

The suspension components are still arriving at Bristol, with the front upper wishbones recently delivered by 4Front Racing.  These are fabricated in steel, in multiple parts, and then welded, heat treated and ground.  The upper wishbones transmit the front wheel loads to the chassis, so they’ve got a lot of work to do.  We only need a few more suspension bits before we’ll be able to conduct the first test-build of the whole front suspension.

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James and Jon with the airbrake slider.

The front suspension assembly bolts onto the front of the cockpit monocoque.  The inside of the cockpit is now being fitted out, while the PPA Group is making the first of our cockpit windscreens.  The screen is made in layers and then bonded together, with each layer formed from a block of solid acrylic which is heated and stretched.

This ‘stretched acrylic’ is the same as that used for jet fighters like the Typhoon, and makes the screen far more resistant to large impacts, like a bird strike.  BLOODHOUND is using a 25 mm thick screen, which is just a little thicker than the Typhoon.  As we’re going faster at ground level than any jet fighter in history, a thicker windscreen makes sense.  The extra thickness should allow the BLOODHOUND to survive the impact of a one kilogram bird at 1000 mph.  I really hope we don’t have to test that for real.

The 25 mm screen sits just in front of BLOODHOUND’s jet engine intake, and shapes the supersonic airflow before it gets there.  The angle of the screen is very shallow, to generate the right shockwave pattern, and this oblique angle means that I’ll be looking through over 50 mm of solid plastic to see where I’m going.  The screen will need to be optically perfect, so this first sample is an important test of the process.

Further back in the Car, the jet engine relies on an ‘airframe mounted accessory drive’ or ‘AMAD’ gearbox.  The AMAD contains the engine starter turbine, as well as the electrical generator and hydraulic pump that will power BLOODHOUND.  All of this will be supported by the AMAD bulkhead, which weighs only 5.3 kg and will be supporting over 100 kg of gearbox and systems.  BLOODHOUND engineering is like a normal race car but with everything multiplied everything by 10.

At the back of the Car, works continues on the Fin.  While the final parts are being released for manufacture, we’ve had a test piece made for one of the intercostals (internal ribs).  Here again, keeping the weight down is important, so the intercostal is only 2 mm thick.  Extra tooling holes and close-formed plugs have meant the part has remained stable under machining and has come out to exactly the shape of the drawing.  Having proved the manufacturing process, we can now start making the other 200 parts of the Fin in earnest.  A mixture of motor sport companies will work on the small parts, while aerospace expertise will deliver the big bits, for the hardest working fin in history.

BloodhoundSSC_rear_dynamic_16x9_Feb2014

Bloodhound SSC rear with rocket and jet firing.

We’re also just about to exceed 20,000 names on the tail fin.  Want to join us at 1000 mph?  Put you name on the fin and you can!

 

 

Andy Green_ Autosport 2012_2 [pic credit Stefan Marjoram]

Wing Commander Andy Green

A British team is developing a car that will be capable of reaching 1,000mph (1,610km/h). Powered by a rocket bolted to a Eurofighter-Typhoon jet engine, the vehicle will mount an assault on the world land speed record. Bloodhound will be run on Hakskeen Pan in Northern Cape, South Africa, in 2015 and 2016.

Wing Commander Andy Green, the current world land-speed record holder, is writing a diary about his experiences working on the Bloodhound project and the team’s efforts to inspire national interest in science and engineering.

The build programme for our 1000 mph Car marches on.  BLOODHOUND SSC is the ultimate kit car, with around 3500 bespoke components, plus fasteners (including 15,000+ rivets in the rear chassis alone).  Of course, that doesn’t stop me greeting the team with a helpful ‘Hi guys – have you finished it yet?’ each time I go down there.  Not just yet, is the answer, but we’re still on track to run in South Africa next year.

BLOODHOUND SSC-Kit Car from Hell

The kit car from hell.

Great news for the Project, with the recent announcement of Castrol joining as a major sponsor.  They have been part of an amazing total of 21 World Land Speed Records, going back to 1924.  In an era when milk was still being delivered on horse-drawn milk floats, the company was supporting Malcolm Campbell in setting his first World Record, at an astonishing 146 mph.  Most recently, Castrol supported Thrust SSC in 1997, when we hit 763 mph and became the only supersonic Record Car in history.  Now the company is up for an even bigger Engineering Adventure.  Well done them.  Check out the video here

A key part of running a Land Speed Record Car is being able to stop it, as discussed in last month’s updateBLOODHOUND will have a truly huge amount of energy at 1000 mph – about 660 Mega Joules.  To put that in perspective, a 70 tonne High Speed Train, blasting along at 125 mph, has about 560 Mega Joules of energy – 100 less than our car.  It’s enough energy to boil over 300,000 kettles, so it’s a safe bet that we can’t stop BLOODHOUND with wheel brakes alone.

Our brilliant aerodynamicist and performance expert, Ron Ayers, has calculated that about 52% of BLOODHOUND’s energy will be absorbed by aerodynamic drag, 36% will be absorbed by the airbrakes (and/or drag chutes) and 11% will be dissipated by the vehicle’s rolling resistance.  That makes 99%.  The remaining 1% will be absorbed by the Car’s wheel brakes.

BLOODHOUND SSC-Campbell 1924

Campbell rules the world record, 1924

If the wheel brakes are only going to absorb a measly 1% of the energy, then why are we even bothering to fit them?  Well, partly because we need them for the UK runway tests next year, at the Newquay Aero Hub, where the brakes will have to do most of the work.  Want to come and watch?  Join our Supporters Club Gold Members and we’ll send you an invitation.

For the runway runs, BLOODHOUND will have brakes on all 4 wheels, with dual circuits, to give us lots of stopping power and redundancy.  The runway at Newquay is 2700 m (9000 ft) long, which is huge until you’re doing 200+ mph in a 6 tonne Car, when it’s not quite so huge anymore.  We’ll be using carbon/carbon brakes, the same as those used by aircraft and high-performance race cars, to give us the best braking performance on the runway.

When we get to the desert, the brakes are less important, as they are only doing 1% of the work.  It’s an important last bit though.  There’s no point in getting 99% of the braking done and then trundling off the end of Hakskeen Pan at 50 mph.  That would just be embarrassing.  The wheel brakes will shorten the stopping distance by about half a mile and they will also let me slow the Car down to walking speed, turn it through 180 degrees and stop right next to the turn-round crew.  The FIA Land Speed Record regulations require 2 runs in opposite directions, within one hour, so turning round and stopping in exactly the right place is a key part of it.

There is a problem with wheel brakes on the desert, though.  We won’t need to use them at 1000 mph, but they will still be along for the ride, at over 10,000 rpm (that’s 170 revolutions per second).  We tested a carbon fibre brake disc at 10% above this spin speed, to give us a safety margin.  The disc exploded.  This carbon disc was one of the best in the world, the same specification as the RAF’s new Typhoon jet uses.  We already knew that no jet fighter has ever flown at 1000 mph at ground level, and now we know their brakes won’t survive it either.  We need another solution.

BLOODHOUND SSC-RAF Typhoon

Almost (but not quite) 1000 mph at ground level.

The proposed alternative is an unusual one, using steel discs.  No-one uses steel for brake discs in extreme applications.  Steel doesn’t absorb as much energy as carbon and it can be damaged by the extreme heat that race car brakes experience.  Steel does have one key advantage for us though – it’s stronger than a carbon disc.  Steel will survive the extreme loads at 1000 mph, but the question is, will it survive exposure to 1% of BLOODHOUND’s huge amount of energy?

To test the steel brake discs, we went to AP Racing, where the rest of BLOODHOUND’s brake assembly has been made.  We cranked their rig up as fast as it could go, which equates to around 160 mph for BLOODHOUND.  The test team did 10 full stops from maximum speed on the same steel disc.  Maximum temperature on the disc was around 1100 deg C, roughly the same temperature as the inside of a volcano.  Harsh conditions for a brake disc – have a look at this video to see just how tough.

The good news is that the aluminium brake calliper (the fixed bit that holds the pads and brake mechanism) only hit 150 deg C, so no problems there.  The final bits of the test are to conduct a metallurgical analysis of our super-heated steel disc, to check it’s still OK, and then spin it up to over 10,000 rpm (simulating 1000+ mph) to make sure it can still cope.  Once it survives all of that, then we’ve found our desert wheel braking solution.  It’s only 1%, but it’s an important 1%.

BLOODHOUND SSC-Brake Disc Test

Brakes at volcano temperatures.

Travelling at 1000 mph brings some other interesting challenges.  To get into the cockpit, I will climb down through an oval canopy hatch positioned on the top of the cockpit.  This area is subject to a very low pressure at supersonic speeds, as the air accelerates over the cockpit, and this low pressure will try to tear the cockpit hatch off the Car.  At supersonic speeds, that will make my 1000 mph office more than a little windy.  If it got ripped off, the hatch would immediately be eaten by the EJ200 jet engine, and both would be destroyed in the process.

To make sure that the hatch stays on, our stress expert Roland has put a lot of work into making sure that the canopy latches are strong enough.  The finished result has just been delivered and looks great.  The latch doesn’t look much, but it’s stressed to a normal working load of 2,5 kN (quarter of a tonne) – that’s 3 large guys hanging off this little handle all at the same time.

Just behind the ‘office’, the HTP tank (containing one tonne of rocket oxidiser) needs to slot into the carbon fibre monocoque.  The rocket will burn off the whole one tonne load of HTP in a little over 20 seconds. It is located close to the centre of the car to make sure that the vehicle’s Centre of Gravity doesn’t move too much with this considerable change in weight. Therefore the HTP tank sits directly behind my seat.  I have though been promised that there are lots of bulkheads and seals to prevent the HTP joining me in the cockpit at any stage of the journey.

Meanwhile, the tank has now had its first test-fit inside the monocoque.  It’s snug, but it all fits nicely, and we can reach all the key points to install the plumbing and to service it.

The front suspension is also coming along well, with AMRC completing the upper section and now working on the lower parts.  They look simply stunning and I can’t wait to see them all on the Car.  Each upper section was machined from a forged block of aerospace grade aluminium, provided by Thyssen Krup, measuring the size of a coffee table and weighing 300 kg.  After 180 hours of machining, we’re left with an upper suspension piece now weighing just 18 kg, with over 280 kg of material to be recycled for next time.

This phase of BLOODHOUND’s engineering is all about details.  Any mistakes we make now will cost us dear, when we get to the desert in South Africa next year and things don’t work as they should.  If we’re going to have a world-class Engineering Adventure, and push the boundaries of physics at 1000 mph, and do it all safely, then we need to get the details right first time.  It’s a fascinating process to watch, as it all starts to come together.

Still checking……

 

White Rhino waking up after being notched by SA Cricket star, Mark Boucher, in the Pilanesberg National Park.