23 replies to this topic

[Jezztor]

John Orr Memorial (WITS University, South Africa) Lecture by Ron Ayers, chief aerodynamicist and research leader of the Thrust SSC supersonic car project. (12/03/02)
Compiled by Ulrico Grech-Cumbo / Jezztor


This evening I had the privilege of attending a lecture by 80 year old Ron Ayers, chief aerodynamicist and chief of research on the THRUST SSC supersonic car, which as we know, still holds the land speed record. Bare in mind I am summarizing a two hour speech.

Project background:

· The idea was thought out by Richard Noble (in 1994), renowned land speed record attempt driver. He initially wanted to be the driver of the Thrust SSC but later in development time, he realized that there would be too much pressure.

· Richard Noble approached retired Ron Ayers, and told him that he wanted him to design and build a supersonic car (1200km/h = speed of sound). Ron initially told him to “bugger off and think of something better, or something” as he said, but his curiosity got the better of him. He re-approached Mr. Noble and told him that he would commence research into the previously never researched supersonic aerodynamics.

· The project ran for three years, commencing in 1994, and ending in 1997 with a successful record. Three men initially started the project, and that grew to over sixty by the end, (including air-surveillance and emergency squads).

· The entire project cost 2.8 million pounds, and by the end, were still 1 million US dollars in debt!

· The final car was also the full-scale prototype

Drivers:

· As Richard Noble stepped down from his driving idea, the team received hundreds of letters in connection with driving possibilities. Ron humorously added that they even received several letters saying “I have just turned 18, I know how to drive a car and I am willing to put my life on the line to drive the Thrust SSC”.

· 15 odd potential drivers were selected initially, with background experience coming from drag racing to military aircraft pilots & interceptors.

· According to their CV’s, eight people were then singled out.

· These 8 people were put in a chamber, set at 30 degrees Celsius, for 24 hours, sleep being prohibited. (This was to ascertain endurance capabilities and to simulate temperatures experienced at Black Rock Desert in Nevada)

· The candidates had to do a test during this time which comprised of a joystick and a graphic with a sphere in the center of a bulls-eye graph. The sphere would jump out of center at irregular intervals and the candidates would have to correct with the joystick. Their reaction time and precision was recorded.

· After this, five potentials were left. They were put in overpowered rally cars and set out on a circuit. This only eliminated one candidate.

· The remaining four were told to write two reports, the first being an essay on what potential problems the drivers could encounter. The second was the driver’s ideal layout of the instrument panel.

· The ‘winning’ candidate was Andy Green.

· This whole process took 4 months

Car technical: (the part we’ve all been waiting for)

· The car’s overall length was 17 meters.

· The car’s entire weight with fuel and lubricants was 10 tons.

· The car was constructed by titanium frame methods.

· The body of the car was two inches thick.

· The heat protection that was used for after-burner protection was titanium.

· The wheels weighed 150kg’s each, were made of solid aluminium (sponsored by Dunlop) and had a rotational acceleration of 30 000 g’s (!)

· The turbines used were 35 year old Rolls Royce fighter jet turbines which were found in a scrap yard. These were bought for 1000 pounds each.

· The turbines can generate 10 tons of lateral force, and together generate 100 000 HP (!)

· Acceleration force of the scale model was 50 g’s (!)

· The model accelerated from 0-1250 km/h in 0.8 seconds! It was powered by 30 (?) rockets on a model rail.

· The braking system of the Thrust SSC consisted of two elements : a parachute (which was released at around 400 mph upon deceleration) with an auxillary parachute, and carbon fiber disc brakes that are used on concorde’s.

· The bearings were made by SKF bearings, they were ceramic bearings. At supersonic speed, the bearings temperature only rose 20 degrees Celsius from point of rest. (!)

· The main instruments in the cockpit was a mechanical-link steering wheel, throttle pedal, brake (button for parachute, pedal for brakes), and a speedometer reading 0-1000 mph!

· Because the front wheels needed to be as wide as possible for stability, they were positioned underneath the ‘sidepods’ of the turbines. This disallowed them to steering capabilities, so therefore rear-wheel steering was investigated. This was carried out on a Rover Mini chassis.

· For aerodynamic and heat reasons, the center of the car behind the rear wheels was narrow and long. The steering wheels could not be placed one infront of another because the rearward one would not be in working contact with the ground. The wheels were therefore slanted and kept side-by-side.

· The car generated 175 dB of sound

· The car traveled 21 km each way for each run.

· Fuel was consumed at an alarming rate – 18 liters per second!

· The fuel tank with fuel weighed 1 ton, but for each run, only 0.6 – 0.7 tons of fuel was used (that is 7% of the entire car weight, so CoG was not affected too much, also because the car is traveling in a straight line)

· The fuel tank was only 1 meter behind the driver, who is positioned in the center of the car for safety reasons (infront of turbines, deformable space in case of impact / accident)

· The engines created gyroscopic forces because the turbines turned in the same direction, but it was not a problem at all experienced by the car. It possibly even helped keep the car in a straight line.

· The frontal area of the car is roughly 5 meters squared.

· Because the car was run in the desert, much dust was thrown up by the sonic waves and general turbulence of the car. The dust in the air doubled (or even tripled) the air density, making aerodynamic drag a relatively large counteracting force.

· CFD was used in the project but not to simulate aerodynamic properties. It was used to analyse both pressure and forces acting on the car. It was not used as a design aid.

· The car’s average speed between the two record-breaking runs, was 763 mph (1220.8 km/h!)

Safety:

· Apart from the driver being clad in fire proof garments, the cockpit was equipped with a self-detonating foam extinguisher as well as a water extinguisher. The cockpit was equipped with compressed air, utilizable for 30 seconds in the event of an emergency, so the driver didn’t breathe toxic fumes.

· An ejector seat was investigated, but professionals in the field told the team that from time of ejection initializing to getting out of the cockpit completely, would take 0.25s which was not fast enough, as at supersonic speed the car could have rolled by then, and ejecting into the ground is hardly advisable!

· The team discovered that at supersonic speed, nose deviation upward of as much as half a degree, would send the car flipping and rolling, uncontrollably. They therefore devised an ‘active suspension’ idea. They used travel-meters in correspondence to the front suspension, and as soon as any upward lift was experienced, hydraulic travel-meters would counteract the length of travel by extending the rear suspension at the same rate, at pretty much instantaneous time. The car had a ‘rake’ position (front suspension setting lower than rear).

· Although an ejection seat was not used, the explosion rocket motor was used at the front of the car in the same situation as above. The motor applied a 3 ton (!) force downward on the front suspension, so to lower the nose if any upward deviation was experienced.

· The team fused the engines so that if one cut out, the other would too, so not to spin the car on its Z-axis, and turn and eventually roll.

· A 4liter supercharged jaguar was used as an emergency vehicle. The rear seats were taken out, and quick-inflating airbags were kept in the back. In the event of a roll, these airbags would be put under the 10ton car, and roll it over so they could get the driver out.

· In the case of the car’s nose raising, the situation would be automatically rectified before the car had even traveled ¼ of its length, at supersonic speed. Speechlessly incredible!


Interesting facts:

· A surveillance microlite was in the air to make sure there was no air traffic, and to analyse the weather conditions. Upon the first supersonic boom, the pilot said it was as if a shotgun was shot behind his head, and the force of the supersonic wave punched his stomach in, and shot the microlite 3 meters up, even though the microlite was flying about 300m above the testing surface.

· The team brought 90 tons of equipment along to USA, on one single aeroplane.

· Black Rock Desert is a dried out lake. The ground of the Black Rock Desert is covered in snow and eventually water, once a year. The area of the desert is roughly 350 square kilometers, and the entire surface area of the desert is covered in water 10cm deep. Wind then gradually dries the water up and creates an extremely hard and flat surface.

· The surface is so hard that despite the car’s mass and downforce, the tracks were only measured to be 10cm deep as a maximum.

· The car deviated (left, I think) at a certain speed (so it was thought) on every run, but then it was presumed that an underground stream still flowed in one area, which slightly softened the sand.

Hope you enjoyed that;
Jezz

[kober]

Thanks Jezz, that's fantastic material. I saved it already...

[Pioneer]

Originally posted by Jezztor
Richard Noble approached retired Ron Ayers, and told him that he wanted him to design and build a supersonic car (1200km/h = speed of sound). Ron initially told him to “bugger off and think of something better, or something” as he said, but his curiosity got the better of him. He re-approached Mr. Noble and told him that he would commence research into the previously never researched supersonic aerodynamics.

Supersonic aerodynamics never previsouly researched? I find that statement questionable.

[MrAerodynamicist]

I expect its more to do with ground vehicles at supersonic speeds, prevously only planes/rockets and such had gone supersonic. Its likely that there is a lot less research for flows so close to the ground and all the problems that occur.

one thing not mentioned is that they gave up with the active suspentiuon in the end and locked it in a nose down sense.

[Ben]

Ayers was a missile engineer. Not many ground effect issues with those.

Ben

[Jezztor]

Pioneer - you're right, sorry, I should have said GROUND VEHICLES at supersonic speed.

MrA - no, apparently the press made up that story...they did go ahead with the active suspension idea, it was luckily never needed.

kober - my pleasure

Jezz

[zppd]

Thanks Jezz, good read. I didn't know that much engineering went into this rocket.

35 year old turbines?? wow!

Check out this picture.. note the shock waves formed above the car
http://ourworld.comp...raves/Waves.jpg

The body of the car was two inches thick.

[Schummy]

This car and this project were exciting. I loved it!

[VWV]

I found this on the G-Force site http://www.gforcerac...ustssc_main.htm

Technical Spec

Chassis:
Welded T45 tubular steel space frame

Body Shell:
Aluminium Carbon Fibre and Titanium

Engines:
Two Rolls Royce Spey 205s

Steering:
Worm drives acting on the rear wheels

Wheels:
Four, Solid forged Aluminium
Rear Arranged in Staggered formation

Length:
54ft (16.46 Metres)

Width:
12ft (3.65 Metres)

Weight:
7 Tons (7.11 Tonnes)Primary

Braking System:
At 650mph (1045kph) Single 7ft 6in (2.28metres) Irvin Parachute
At 400mph (645kph) Irvin ParachutesSecondary Braking SystemFront One pair of 17in (432mm) carbon disks. Two piston callipers acting on each wheel.

Rear Single 17in (432mm) carbon discs. Two piston callipers acting on each wheel.

Data Engine output 1000,00hp (75Mw) at maximum speedSpeed in excess of 850mph (1370kph). Acceleration 0-600mph (0-965kph) in 16 secondsLubricationCastrol synthetic lubricants, brake fluids, hydraulic fluids and greases.

For further information go to http://www.eng.vt.ed...sc/auto_lsr.htm

[MrAerodynamicist]

Originally posted by Jezztor
MrA - no, apparently the press made up that story...they did go ahead with the active suspension idea, it was luckily never needed.

I remember the story from a BBC[?] TV program that they showed a few weeks after the record was set, as: they started off using it but they had some problems with it and towards the end they did the running with the nose locked down?

[12.9:1]

The book - THRUST by Richard Noble is must reading for any one contemplating a massively
over ambitious project ! Nobles achievement, - conquering huge inertia, as well as wind resistance.

By the end of the book it is clear, that possibly only an other test pilot could have mastered an
inherently unstable {rear steer} vehicle, with glacial steerring response - he would input a bit
of say left steer 1.5 sec. worth, then wait 3 sec. to see if that would dampen the ever present
oscillations, on and on down the course @ 700+ mph.

Richard Noble
Andy Green

[Fudman]

Previous post stole my thunder.... Couldn't agree more GET THE BOOK. Noble's force of will to keep the project running was simply astouding. There are all sorts of fascinating items for the technically minded as well, pics of CFD, rocket tests, rear-stear Mini to name a few.

According to the book the active suspension WAS used for the record runs but in a modified form that prevented the cars attitude rising above the critical angle for "flying" should a system failure (electronic/hydraulic/mechanical) occur. With the active in the locked position the car generated too much downforce at the front causing it to bottom out and become uncontrolable.

The BBC & ITV documentaries of the project were available for sale a few years back (I purchased both when living the UK) and may still be available, check their websites...

[MrAerodynamicist]

well its all from memory so I might well be wrong!

[desmo]

Another good source of info on the Thrust SSC project is an article in Racetech magazine on the effort published in (I believe) '98, it was the cover story. I can't find my copy at the moment, but remember it as a very interesting read.

[Jezztor]

Fudman - as your post was beaten, you beat mine

I did some research and also found that I was right, the active suspension was used, and the nose lock situation caused many problems with excessive downforce and even a prediction for the inability to reach supersonic speeds because of too much drag.

For those of you who live in South Africa, there was a fantastic article on that too, in '98. I saw the racetech one, it was also very good. There is so much information so certain parts of the article lacked much technical depth, but limited space is limited space.

Jezz

[Ben]

The BBC documentary showed the meeting where it was suggested that the active suspension be locked up. Jerry Bliss went apeshit and almost walked out. They did try it but it didn't work so they ran it in active mode. It wasn't really active at all just a hydraulic ride height adjustment though.

Ben

[Kaiser]

Great post, I remember when the project was ongoing, the driver had a great sence of homour. IIRC the car had some electronic sound deadener, the driver called it the courage button, car starts to make scary noises, hit the button,instant courage.

as far as supersonic ground cars, and no previous research, there was the Budweiser rocket car, which might or might not have reached supersonic speeds.(me thinks they missed it by a RCH)
http://www.roadsters.com/bud/

[MrAerodynamicist]

The claim by that Budweiser car is rather weak IMO. They didn't even hear a sonic boom

[Jezztor]

The Budweiser car did not reach supersonic. It was a question posed to Mr Ayers, but the thrust SSC is the first car to have reached supersonic.

the original preliminary estimate 739.666 miles per hour (1183.4656 km/h) was proclaimed as the final speed.

That is not supersonic speed

Jezz

[Ben]

As an aside, I read a story once which described the consternation when the rocket's speed was given as 37mph by the radar tracking. It later transpired that the rader had picked up an Edwards Air Base supply truck on a perimeter road!

Anyway, the budweiser car definitely didn't go supersonic. They could side step the sonic boom question by saying ground effects could have surpressed it. With SSC it was clear that an audible sonic boom was present as with an aircraft.

No disrespect to Stan Barret mind you, he had a sidewinder missile strapped 100mm behind his head. Brave man.

Ben

[Christiaan]

I attended the talk in Cape Town. Ron is quite and eccentric man, I had a chat for about half an hour with him afterwards. I am on my way to becoming a CFD boff so we talked extensively about CFD. He said that the simulation performed by I think Swansfiel University was within 2-10% accurate to the testing done on a scale model. The bodel itslef was very interesting as well. Unfortunately I left all my notes on this project in my car. I'll post more stuff soon.

[Jezztor]

Looking forward to it, Chris. That accuracy remark is something I obviously forgot to take down.

Jezz

[Christiaan]

Okay, the interesting aspects for me as an aspiring CFD boff and some sort of engineer were

- the theory on flow in the transonic region (transition from sub to super sonic) to is not quite known even today. This meant that they needed to accelarate the car as rapidly as possible through this region because no amount of CFD and model testing could give them fool proof results.

- the shape of the thrust was detemined purely from design philosophy, as in two engines for balance, weight foward was desireable position for the CG for yaw,pitch and roll stability, and a tail fin far rear to provide a good moment arm for steering.

- it turns out that the two engines provided more than enough power and were running way below full capacity.

- a model was used to verify the results from Swansfield University's CFD simulations. It was run on a perfectly flat laser laid 1km long track (this track had a maximum error of 0.6mm for the full 1km stretch) and powered by 22 small rockets. It reached a speed of 1250km/h in 0.8 secons and had 10kHz peizoelectric sensors all ver tghe body to measure the pressure distribution. The test results were within 2% of the CFD results. This was quite a feat for those days.

- the car did have active suspension to tilt the car by about 1 degree. The window was half a degree either way t tilt the car up or down and accelerate it by about 50g in the direction, so you can imagine it was extremely unforgiving of error. The sytem had 5 failsaife logic circuits but had a problem in that it was that the system had a reaction time of 0.25 seconds, which was too high by about 0.1 seconds. This meant that the car couldn't react quicly enough to stop itself from taking off into the air if something happenned. this is why the put the explosion rocket motor at the front of the car which provided 3tonnes of downforce in 0.01 seconds. Fortunately they never had to use it.

- the radial acceleration on the smooth aluminium wheels was 35000g

- the car's controller had 120 data points and two on board computers

- given the weight of the car, and the interaction between it and the groung, the ground itself acted as a tyre

I think thats all that Jezz hadn't mentioned

[Jezztor]

Originally posted by Christiaan
Okay, the interesting aspects for me as an aspiring CFD boff and some sort of engineer were

- the shape of the thrust was detemined purely from design philosophy, as in two engines for balance, weight foward was desireable position for the CG for yaw,pitch and roll stability, and a tail fin far rear to provide a good moment arm for steering.

The choice of two engines didn't have to do with balance, it had to do with power/speed ratings and safety (they didn't want a central engine behind the driver). The balance matter has to do with the positioning of the two engines.

- given the weight of the car, and the interaction between it and the groung, the ground itself acted as a tyre

And as a damping system / shock relief.

-

Nice info Christiaan - he went into a lot more technical detail at your lecture it seems. I did mention some of the above points, but didn't get the 22 rockets accurate, for some reason my father and I recalled 30.

Good work, mate

Jezz