PH speaks to Andy Green after he was forced to pull the plug on Bloodhound’s latest run
Since we last checked in with Bloodhound’s testing programme the car has reached some significant milestones – and having recovered from minor damage to hit the 500mph mark on Wednesday, everything seemed to be going fairly smoothly for the team. However, today’s attempt at reaching 550mph had to be aborted short of achieving the goal; a setback to the casual observer, but not to Andy Green, whose previous record-breaking experience has taught him to take such things in his stride.
“This is all part of the process,” he tells PH when we speak to him from the Hakskeen Pan soon after the conclusion of the test. “The jet started really nicely, it was crisp off the line with very little cross-wind and the car was running beautifully straight. I got up to a little over 450mph and then got a flickering overheat light for the jet engine bay. It’s the second time we’ve had this problem this week, so I throttled back.
“We’d also done a minor modification on the parachute last night; I just analysed the video and that appears to have worked perfectly which is really good. And the other thing I wanted to get out of this run was just to establish what the grip rate is on the desert, because it’s a very low-grip surface so we’re still working out how quickly we can slow the car down. I pretty much nailed that; I got to exactly after I could feel the wheels starting to slip, which is perfect. So we didn’t get to peak speed by a little bit, there’s some work to investigate the overly-hot engine bay, but everything else went really well, so personally I’m really pleased with that run.”
Those who’ve seen a Red Arrows display in person, and heard the steady calm of Red One’s voice through the PA system as he twists and turns a few thousand feet above, will have some understanding of the composure with which Green recalls the run. The ex-RAF pilot and current land-speed record holder is seemingly unflappable – but how did he react to receiving a warning light at more than twice the top speed ever recorded during an F1 race?
“In my recollection of the run, the caption came on, I looked at the speed, looked at the caption, made a decision that, ‘alright, we’re going to have to abandon this run’ and started throttling back. I paused, and then because we wanted to test the chute at a high speed, throttled back at about 475-480 and then put the chute out within a couple of seconds as the car slowed down through 450. Having watched the video, all of that decision making happened in less than a second, simply because I’ve considered ‘if that happens then I’ll do this’ so it actually happens in real time much faster than I remember it looking back at it.”
This isn’t the first challenge the team has faced since they arrived in South Africa last month, and it surely won’t be the last. That’s not necessarily a bad thing, though; while going fast is all well and good, identifying and overcoming such obstacles will likely be a bigger priority for now, allowing Bloodhound to hit the even greater speeds they’re aiming for next year.
“[Earlier in the testing programme] we had an aborted run because there were no anti-bounce software on the switches in the cockpit, we had a switch bounce of less than ten milliseconds and the jet engine shut down. We’ve now got some anti-bounce software which is what normal road cars have fitted as standard, we simply didn’t have it fitted to the car because we didn’t know we were going to need it. And this is what high-speed testing is about, this is exactly why we’re here. So the fact that we’ve had a minor overheat is part of understanding what the airflow is like because it’s so complex and such a complex shape in the engine bay that, even if you did a full computational fluid dynamics assessment of what the flow is going to be like in there, you’d probably finish up with at best a rough guess and at worst a completely wrong answer.
“So this is one of the things we’ve got to test, it’s a little hotter than we were expecting. The engine bay is able to take very high temperatures but the fire wire goes off at a relatively low temperature [it burns and breaks at 160oC, triggering the alarm] to warn us if something is getting hot in there, which it appears to be. We’re going to find out whysome insulation, some more airflow; there are lots of different solutions to this and that of course is part of modifying the car for higher speed running last year, so this is all part of the process.”
There’s still plenty of work to be done on the car, then. But how does Bloodhound feel to drive compared to Green’s previous record-breaker, Thrust SSC?
“It’s a lot crisper, a lot more precise. Both cars have very firm suspension but I get a much better feel through this car – for instance, it was impossible to work out where the wheel lock was in Thrust SSC, I got no feeling. I could actually feel it today, to my surprise, which was encouraging. The car is more sensitive to crosswinds than Thrust SSC, but this is not the finished car. We haven’t yet added the rocket pack which will move the centre of gravity, reduce the yaw static margin and reduce the crosswind sensitivity. So the aerodynamics are set up for next year’s jet and rocket car, for this year’s testing the aerodynamics are actually slightly cross-wind sensitive, so there has been up to 90 degrees of steering in the cockpit to try and keep the car straight, and we’re running to a relatively 10mph crosswind, but with those limits the car’s running really nicely.”
That 90-degree figure may have caught your attention, but Green brushes over it as if he’s recalling his breakfast order. What does a 90-degree steering input in a land-speed record car actually entail?
“That’s two to two-and-a-half degrees at the wheels, the equivalent of putting about 30 or 40 degrees of steering input into a normal road car. Now, 30 or 40 degrees doesn’t sound like much, but for example – and please don’t try this – if you snapped on 40 degrees of steering at motorway speeds it would really surprise you. It’s a lot of steering at high speed, certainly a lot of steering at 400-500mph, but because of the lateral grip of these metal wheels on what is a very slippery surface the steering inputs have to be reasonably rapid, and on occasion reasonably large, in order to keep the car pointing in the direction I want.
“And of course I’m using two different steering techniques: I’m using very rapid inputs for velocity related steering, so to stop the car yawing off line. If it’s being pushed sideways by crosswinds, though, we’ve now got a displacement where physically the car is off line, that has to be a very slow steering correction because you can’t just throw a six-tonne car sideways and put it back on line. I’m controlling the direction with very rapid inputs to stop the yaw rate building up in a 13-metre long, six tonne car, and then slowly adjusting the displacement to keep it on line, so it’s two different steering inputs depending on what I’m actually trying to do.”
From the onboard footage (see below, from 4.40) it’s possible to see exactly what he’s talking about, the car’s path across the desert floor a far less linear one than you might imagine. What’s not so apparent from that cockpit camera, however, are the velocities and g-forces which Green is experiencing. With so much to focus on and such flat, featureless surroundings, how great actually is the sense of speed from within the cockpit?
“Enormous. Doing 100mph feels fast, particularly because it only takes a few seconds to get there, and then 200 feels much faster because it only takes a few more seconds to get there. Suddenly, 30 seconds into the run, I’m doing 3-400mph and the ground just keeps coming at me faster and faster and faster and faster. Which is of course the purpose of a land-speed record car, it’s unparalleled performance, the highest performance of any racing car in history because it’s trying to become the highest performing racing car in history.” Bloodhound still has a long way to go to earn that title, though, and the rest of the testing programme will be crucial in getting there. So how soon does the team to expect to be back at it?
“We’re taking the opportunity while we’re checking the air flow around the engine to do various other jobs. We’ve got a big long list of engineering tasks, several of which we’ve said ‘well, when we’ve got a day or two we’ll do that’ so this weekend is basically going to clear off all of the outstanding jobs fixing minor wiring loom problems and replacing a couple of the pins that hold the engine in place, because they’ve got to a stage where we want to replace them. There’s lots and lots of jobs, so we’ve got a couple of engineering days now and then we’ll be aiming to get the car fighting fit for next week.”
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