Engineering a 1000-mph car

  • 16-Oct-2015 03:56 EDT
BLOODHOUND_SSC09-15_Poster_Side_July2015.jpg

The Bloodhound Project is accelerating toward its 1000-mph World Land Speed Record attempt. (To view additional images, click on the arrow at top right of this image.)

Engineering a car designed for a 0-1000 mph (1610 km/h) time of 55 seconds is one of the world’s most unlikely, most daunting, and most exciting challenges. That is the task of Mark Chapman, Chief Engineer of the U.K. supersonic Bloodhound Project and his team, now on course to attempt a new World Land Speed Record that at Mach 1.4 blends automotive and aerospace engineering technologies to achieve a spectacular target never before considered outside the realms of space fiction.

It is eight years since Chapman took a telephone call and made the life-changing decision to join the small, highly specialist project to build on the supersonic success of Thrust SSC, which achieved 763.035 mph (1227.986 km/h) in 2007. It has taken four years longer than planned as the design evolved and hurdles overcome, but now runway test programs are in place starting in the U.K. in March 2016 that will take the Bloodhound car initially to a relatively modest 200 mph (322 km/h) before culminating in scheduled 800-mph (1287-km/h) record-breaking runs in South Africa in October 2016. The 1000-mph record attempt will be in 2017.

An afterburning 90-kN (20,230-lbf) Eurojet EJ200 jet engine as used for the Eurofighter Typhoon, and triple Nammo rockets—total rocket thrust 120 kN (26,980 lbf)—will blast the Bloodhound toward the record. Then airbrakes are deployed, with braking parachutes (a transonic drogue type used in the 1960s and ’70s and manufactured based on that design by SES, as a back-up safety system as speed drops below 650 mph (1046 km/h). Rotary wheel brakes will be applied from about 160 mph (257 km/h).

Interviewed by Automotive Engineering in London, where the Bloodhound was unveiled to the public, Chapman spoke of the most professionally satisfying achievement of the project to date; it wasn’t some esoteric area of complex aerodynamics, powertrain, or materials technology: “It was how we solve problems. There isn’t any precedent for this car. Unlike Formula One, which is also pushing technology boundaries, you can’t just look across a pit lane and say, ‘That’s how Mercedes or Red Bull has done it; let’s do something similar.’ This is completely different to anything anyone has done before; it’s thinking on your feet and solving it totally yourself.”

The project is seeing the integration of many technologies, said Chapman: “We are developing a vehicle that is part jet fighter, part spacecraft, and part racecar.”

One difficulty for the project has been finding specialists with the extraordinary breadth of experience required: “But we did so—and have seen them blossom in an environment where we don’t know the right answer! Our design team has just five members (we peaked at 15), with a further 15 responsible for building the car.”

Chapman’s background has been in the aerospace industry, beginning with a British Aerospace (now BAE Systems) apprenticeship in 1987, later gaining a degree in aeronautical engineering.

Aerodynamics challenge

Of all the many hurdles to overcome with Bloodhound, Chapman cited aerodynamics as the most challenging: “Getting the car to stay on the ground but also getting it to go in a straight line. At Mach 1.4 we don’t generate a significant downforce. We want the car to sit completely neutral—just at 1 g. Too much downforce and it would break through the crust of the desert.”

Achieving this has been a major part of the Bloodhound project: “Fully fueled, the car weighs about 7.75 tons. There is some variation in positive or negative downforce, ranging from about 1 to 2 tons.”

For its 2016 high-speed tests in South Africa, Bloodhound will use only the EJ200 engine and one rocket. These will provide sufficient power to reach 800 mph (1287 km/h).

“The air intake we have at present is optimized for Mach 1.1. So—and this is one thing we need to test—we think we are on the edge of being able to use reheat from stationary; at present we can’t use full ’burner until about 80 mph. We have a design for the auxiliary doors on the side of the intake to let in extra air. The AV-8B Harrier had a similar design. So if we need to increase our acceleration for the record run—what limits our speed is not power but length of desert—we could do so.

“To pump the oxidizer for the rockets we have a Jaguar AJ133 5.0-L supercharged V8 auxiliary power unit (APU). Jaguar uses the engine for its F-Type R sports car. We also have an all-wheel-drive F-Type R as the medical rapid response vehicle, plus two Jaguar XJRs with the same V8 engine as rapid response fire vehicles—effectively a pair of 200-mph fire engines!”

Bloodhound uses a mix of materials; the front third of the car is a carbon-fiber monocoque to provide a very strong tub. It takes all frontal loads. Aft of the cockpit area is a metallic structure comprising the titanium stressed skin that sits on top of aluminum ribs.

“Chassis frequency and stiffness are almost more important than the strength of the car,” said Chapman. “We are trying very carefully to keep frequencies at an order of magnitude between the wheel hop frequency of 3 Hz and desired chassis frequency of 30 Hz.”

Overall length of the car is almost 14 m (46 ft) and wheelbase about 8 m (26 ft); “we are looking for deflections of only a few mm,” he said.

For its 200-mph tests on a runway, the car will use rubber-tired (recertified by Dunlop) wheels from a BAC Lightning fighter of the 1960s and ’70s (not to be confused with the World War II Lockheed P-38 nor the latest Lockheed Martin F-35 Lightning II). This editor first achieved 1000 mph in a RAF Lightning in the 1970s—but at 35,000 ft.

The tires, very narrow and running at high pressure 200psi, are good for about 250 mph (400 km/h). “No one has ever produced tires that go much above 400 mph,” explained Chapman. “So when we run on the desert we are on solid aluminum wheels. Otto Fuchs (the company developed the classic forged aluminum wheel for the Porsche 911 in 1964—the Fuchsfelge—and currently wheels for many other models) did a special forging for us, and Scottish company Castle Precision Engineering, who make turbine discs for Rolls-Royce, machined them.

“For braking during the sub-200 mph tests, on rubber tires, Bloodhound will have an AP Racing carbon-carbon system on all four wheels; on the desert, for higher speed tests, we only have brakes on the front. They use steel rotors because if you spin a carbon disc at 10,500 rpm they will explode!”

Fighter pilot's cockpit

The Bloodhound’s cockpit layout was designed around the requirements of its driver, the current World Land Speed Record holder, Royal Air Force fighter pilot, Wing Commander Andy Green. It includes three screens providing various engine data, an F1-style steering wheel with systems’ operating buttons, a foot throttle for the jet engine, and a brake pedal.

“It combines a bit of F1 and aerospace. Ergonomics such as emergency levers for fuel cut-off of the EJ200, and others that manually release the parachutes, are laid out in a similar way to those of an aircraft,” stated Chapman.

An electric rack and pinion system steers the car’s front wheels. Bloodhound’s turning circle is 250 m (820 ft).

For the record attempt, Green will strap into the cockpit, start the EJ200, and get its temperatures and pressures up to required levels before “taxi-ing” at low speed to line up for the record run. Then it’s brakes off, jet engine throttle to maximum dry power accelerating Bloodhound to 80 mph (129 km/h) before selecting maximum afterburner (this sequence is subject to change with the possibility of maximum ‘burner from brake release) to pass 300 mph (483 km/h).

Green pulls back triggers on the steering wheel to activate the rocket light-up sequence. The Jaguar engine APU will start: “We use that to pump a small amount—about 10% flow rate—of hydrogen peroxide (H2O2) to the catalyst pack; this pre-heats the pack. Peroxide decomposes to steam and oxygen across a nickel silver catalyst. If we delivered 50 kg of peroxide per second it would quench the pack and it would never get hot enough; the catalyst must get sufficiently hot (around 600°C) at just the right time, at which point the full flow rate of peroxide can be delivered after a second or so.”

The rockets ignite at about 350 mph (563 km/h). They burn at full power for 20 seconds, to hurl Bloodhound through Mach 1 and on to the 1000-mph target and through a speed trap under FIA control, as Green immediately cuts the rockets and throttles-back the EJ200, the car’s drag providing immediate 3 g deceleration. The airbrakes are deployed and 5 mi (8 km) from the “trap,” and the vehicle stops.

But there is far more to do before the record can be achieved.

The car must make two runs in opposite directions. Effectively about 50 min is available to back-up crews to refuel, carry all checks, and turn it around.

Said Chapman: “This requires a choreography of checking rocket, jet, and gasoline engine fuels and cooling systems; it is almost as big a challenge as getting to 1000 mph!”

Then it will be “just” a matter of reaching at least 1000 mph again—the car’s theoretical Vmax is 1050 mph (1690 km/h)—and entry into the record books.

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