What is the most common comment to be heard in a car or aircraft workshop?

Well, let me tell you. Smoothing out certain common technical expressions in order to preserve the ears of the young or fastidious, it goes like this:

“Oh, bless my soul! Whoever designed this jolly engine bay must be a rather silly fellow, and possibly the offspring of a goat and a Lady of the Night. To get at the jolly turbo I have to take out the jolly radiator, the jolly generator, and the jolly power steering pump before I can get anywhere near the jolly turbo nuts and bolts. If I could make the acquaintance of this jolly designer I would like to shake him warmly by the throat and enquire of him whether he has ever actually worked on a jolly engine in all his jolly life. I would further welcome the opportunity of inserting a couple of Snap-On spanners into a bodily orifice”.

Those who are acquainted with workshops will have no difficulty in translating this.

In fact you only have to lift up any modern car bonnet to see the point. There is an awful lot of kit crammed in there, much of it spang in the way of other kit. The 1930’s days of opening a double-hinged bonnet and getting complete access to all component parts is a long-forgotten memory.

It is a matter of expectations. Look at an aircraft – any aircraft, however pointy – and you expect to see removable cowlings and hints of access panels all over the thing. De rigueur. Buy yourself a sleek new Jaguar or Mercedes and you expect that to look like a shiny bar of soap from front to back. Any hint of an external access panel apart from bonnet, boot, doors and fuel filler and you’re off to look at a BMW or Porsche instead. (In fact by my reckoning the last car anybody built with really good engine access was the Jaguar E-Type of nearly 50 years ago).

Which is why nowadays the most prized mechanics in engineering are those equipped with the brains of Einstein, X-ray eyes, and above all the tentacles of an octopus.

If you are aware of any such persons, please let BLOODHOUND know. They could use them.

The BLOODHOUND getting-at-things problem is not unique – no, of course it isn’t. But it’ll do until ‘unique’ comes along. Of course the BLOODHOUND fuselage needs quick-access hatches and removable panels. It’s never going to be a bar of soap like a modern road car – rather more like the panel-infested fuselage of a fighter jet. Smooth, streamlined, sleek, certainly – but you do have to get at things.

In fact, many of BLOODHOUND’s access problems are very similar to a jet fighter’s. And a jet fighter design team will have hundreds of design engineers usually working for a decade or more to get it right. BLOODHOUND started five years ago, and now has maybe 18 in-house designers…

Let us say you are the Chief Designer of a new jet fighter. The Head of Structures ambles into your office and wants to know about access requirements. So you call in the heads of all the other departments to put in their bids. The initial result – naturally, mini-empires being what they are – is a steadily increasing number of holes being laced together by a steadily decreasing structural frame in order to make way for said holes. The thing becomes a sort of enormous jigsaw puzzle.

Is this the truth?

Well, not exactly.

Firstly, a jet fighter is designed around the engine(s) and weaponry – as indeed is BLOODHOUND, of course – but secondly, in the aircraft you’ll normally have the luxury of knowing the shape, size, weight, dietary and mothering requirements of the great majority of components at a pretty early stage in the proceedings.

Hmm…

Upon reflection I’ll re-phrase that. In the aircraft you THINK you know these things – a view which not infrequently turns out to be a triumph of hope over experience.

 

Bloodhound in thrall

BLOODHOUND has much the same problems but with one added piquancy. All jet fighter designs are Mach-critical, certainly – but no jet fighter has ever yet been tasked to fly at Mach 1.4 at an altitude of 13 cm. So while fighter design kow-tows deeply to aerodynamics, BLOODHOUND is utterly and totally in thrall to it – an ogre with its foot on the neck of everyone on the design team. Aerodynamics trumps all, period. So it gets particularly difficult to always decide early on where and how you can put in access panels…

And then there are the things you need to get access to. In BLOODHOUND’s case you didn’t always know the size, shape, weight, smell or personal hygiene requirements of every component from the get-go, largely because so many components are complete one-off’s. No fighter, for example, also employs a huge integral rocket. (Rocket-propelled weapons, yes, but these are mostly – not always but mostly – carried on external pylons under the wings). And I can say with absolute certainty that no aircraft of any kind has ever employed a Cosworth F1 engine in any way, shape, or form.

So at some point as the totality of design comes together, someone has to take a long, hard look at how to get at everything – and indeed, how to get it installed in the first place, since you are going to look a very great numpty if you need to put in, say, a 12 cm square thumblegrummit and have only left an 11 cm access so to do. Likewise with the jet, the rocket, me – sorry, sorry, Andy Green – in the cockpit, etc. (In fact I still harbour a hope that they might get that a bit wrong, so that Andy, a racing Giraffe, can’t quite get in, whereas I, being more like a racing ferret, might have a better chance. I have to say this hope is kinda fading, but you never know your luck…)

In fact, as so often in design, the big obvious things are not always the major problems. You need to get at or replace the jet? So take off some of the rear fuselage panels, undo the bolts holding the upper rear space-frame to the lower, and lift the upper up complete with EJ200. Not exactly a nip-out-during-the-tea-break job, but basically straightforward, huh?

Not straightforward. Think of yourself as the designer. Where are those two bolts which only the circus-trained octopus can get at? Like death or taxes they’ll be there somewhere…

This sort of thing goes on. This is a one-off design. Somewhere – somewhere – it would be ever so easy to paint yourself into a corner you just hadn’t quite foreseen.

Ridiculous? Not so. Say there are a cluster of high-pressure nitrogen systems in the front end of the car. Their allocated spot has been fixed since early BLOODHOUND puppyhood. There is a quick-access hatch to connections by which they can be re-charged in situ. But… if you need to actually take one out, is there any one bolt you simply cannot get at without taking half the car apart? Or any connector – hydraulic, nitrogen, oxygen, electrical - ditto?

Not simple…

Enter the triad of BLOODHOUND’s James Painter, Annie Berrisford, and Stuart Allen. (Well, enter the whole design team in fact, since this is something everybody gets ensnared in – but primarily James, Annie and Stuart). James is Engineering Lead on Vehicle Integration. James looks to me like a rather stylish 25 year-old, but that can’t be right because he’s already had a distinguished engineering design career ranging from jet engines to Indy car transmissions to race-car turbochargers and turbo-generators, plus starting his own consultancy company a few years back. One of those engineering polymaths which BLOODHOUND seems to specialise in. Then Annie, lead on Vehicle Operations (see: An Engineering Nursemaid). Then Stuart, the composites expert – but we’ll come back to composites.

Vehicle Integration obviously starts off with deciding where everything needs to go. The short answer might appear to be (a) where there’s room for it, and (b) where power cables, pressure lines, hydraulic pipes etc have the shortest practical runs from A to B. But in fact it’s not as simple as that, nor anything like it, which will probably come as no great surprise to anyone following the BLOODHOUND adventure, which is apt to become – well, tortuous at times. Every component of BLOODHOUND is going be hell’s rugged of course, but even so there are some bits and bobs you wouldn’t want to park somewhere ferociously hot (which means not near the jet or the Cosworth exhaust) and others you’d like to keep clear of the worst of the vibration (which means DEFINITELY not near the rocket, the full extent of acoustic vibration of the Falcon at full grunt being as yet still a Here Be Ye Dragons area). And still others where you’d most distinctly prefer the weight to be up the other end of the car. So you take into account all that…

And once you’ve got a place for everything and everything in its place – why, only then can you finalise the small matter of getting at it.

 

A need to get at it…

The access issues sort of come at you in four layers. Firstly the initial build, so you don’t get left with that 12 cm thumblegrummit sitting beside the car with everybody standing around it scratching their swedes and saying how the hell are we going to get that in? Secondly, reasonable access for major maintenance. Not entirely dissimilar.

Then it starts to get a bit more difficult…

The third must-have is accessibility for the Start-of-Day and End-of-Day checks. There is time for these, yes – but not all the time in the world. There is time for taking fairly large panels off – but not all the time in the world. There is time for a (currently) 36-point action plan for waking the car up in the morning and soothing it to bed at night. Some of these actions are fairly simple – say, two per cent – but others are, shall we say, rather more challenging. Torque-checking certain bolts, for example – such as them as holds the front of the car to the back of the car, which have to be regarded as a tad getting on towards vital. Plus quite a number of other bolts which in their own right are equally structurally critical. All of which need access, even if it means borrowing Grumpy from Snow White and inserting him upside-down into a cavern which even he might find a smidgeon tight around the elbows.

Which is, in fact, a thought. Add Grumpy to the Octopus Man they would like to recruit.

Oh, and then there are the wheels and suspension front and rear, with particular emphasis on regularly getting at the wheels for visual inspection plus crack-testing by eddy-current or dye-penetrant or possibly both, being as how a supersonic wheel-burst could seriously ruin everybody’s day, especially Andy’s.

Rear wheels – more difficult to get at than you might think, but not insuperable. Front – well, again not insuperable, but the fronts are buried along with the brake-packs and the whole front suspension / steering module – items you also want to take a look at. So you design the whole module to be (fairly) readily dropped down out of the car as an integrated unit. But that isn’t so easy because the front end is the composite end…

Well, again we’ll come back to that.

So, there are these daily checks to do, for which there is time. Not all the time in the world, but time.

But then we get to Problem Four. The Land Speed Record turn-around. At which point time suddenly becomes compressed in a most virulent manner. And worth more than mere gold.

For the LSR rules state that the speed of a vehicle is the average speed of two runs through the timing trap, one each way, to be carried out within the time-span of one hour.

Aaah…

At 1,000 mph Andy Green will flash through the one-mile timing trap in 3.6 seconds. Which means that from the instant he exits the trap he now has precisely 59 mins 56.4 secs in which to turn round and do it again. A minute of that will be used up slowing down, another up to two minutes in turning round through 180 degrees to point the other way, and one minute or two minutes more in idling the jet long enough to stabilize temperatures before shut-down.

So now you have approximately 54 mins 56 secs left…

And a very, very great deal to do. Which requires a very, very great deal of pre-planning.

Broadly speaking – very broadly speaking, because it’s much more integrated than this – Annie’s task is to identify what has to be done, and James’s to work out how to make it possible.

The what-has-to-be-done list is formidable.

You have to change the hybrid rocket casing for a freshly-charged one. A task which means a quick-access hatch low down abeam the front of the rocket so you can reach (just) the quick-disconnect union of the HTP feed to the rocket, disconnect the sensors, and then ease out four metres of rocket – which will be a tad warm-ish – through the rear of the car, a bit like sliding out a really hot enema without the patient noticing. Then slide in a fully-fuelled one – cold but much heavier – re-connect the sensors and the HTP feed, and re-secure the fixing flange at the back end.

At the same time you have to re-charge two high-pressure nitrogen systems.

And plug in external electric power. And plug in electronic data downloads from the black boxes of the car systems recorders. And the rocket sensors. And the jet run-data. And the Cosworth run-data. (Okay, most of this will already have gone out by telemetry during the run – but not all of it, and you can always have a telemetry hiccup, so you definitely have to download it).

And at the same time you have to drain and re-fill the Cosworth’s cooling tanks – ironically, with a separate umbilical to the engine itself to manage its temperature during the turn-around, maybe with warm liquid or maybe a bit cool – running will tell. But certainly you have to replenish the ice in the main coolant tank. Picky things, these F1 engines. And also re-fuel the Cosworth. This not because BLOODHOUND couldn’t carry enough Cosworth fuel for two runs – weight being critical but not that critical – but because of fuel temperature after the first run. So more quick disconnect (QD) access points…

On top of this there are also some might-be-needed tasks. If Andy’s used the brake-chutes you’ll need to change the ‘chute canisters for fresh-packed ones. In theory if Andy’s had to use the ‘chutes on a record run it implies some sort of airbrake snag, in which case the car’s not going anywhere – but that’s the theory as of now. And theories can change once the hound starts to run. Similar is quick access to the front and rear winglet screw-jacks to adjust their angle of incidence. On the face of it you’d be unlikely to glance at the wheel-loading data download, scribble on the back of an envelope, and alter the winglet angles in between runs. But who knows what run-experience might throw up? And in any case you’ve got to have good access to the jacks.

And then there’s the jet, again. The fuel tank must be re-filled, and the tank breathings from the vent led away for reasons we will shortly come to. Two more QD connections.

The EJ200 is spooled up by high-pressure air fed through an air turbine starter (ATS), which pressure in BLOODHOUND’s case is provided by an external start-cart. This has to be connected up, as does a hose to lead away the exhaust from the ATS. Another two QD connections.

Normally a jet fighter is not bothered about these last two excretions. But a jet fighter is not going to have High Test Peroxide (HTP) on the scene…

Well, clear the decks. Because BLOODHOUND very certainly will. And I do mean clear the decks because at some point, probably quite late-on in the turn-around sequence, you have to pump nearly a tonne of HTP into the rocket oxidant tank. And HTP is not nice stuff. Perversely, it will not ignite by itself – but spill it onto anything which produces a catalytic reaction and it will instantly de-compose into super-heated steam hot enough to cause whatever it’s been dropped on to combust. (See: Tobacco, flesh and testing). And a noticeable amount of kit and liquids within BLOODHOUND will act as enthusiastic catalysts. So when it comes time to tank-up on HTP the rest of the turn-around team will stuff fingers in ears and retire to a safe distance – preferably Cape Town, although that may not be entirely practical. Then two or three refuellers in protective kit will do the job while another in the same kit stands by with a high-pressure water hose and ganglions sticking a foot (30.5 cm) out of his body ready to dilute any spillage. Which of course Should Not Happen. But all the same…

And the HTP re-fuel means yet more Quick Disconnectors – one to fill the HTP tank, another to lead its vent-valve breathings away, and yet a third to provide a de-ionised water flood to dilute the HTP in an emergency.

The list of access panels is sort of growing. Especially the list of quick-access panels.

 

But there is nothing un-stressed…

So what’s the difference between a quick-access panel (QA) and – er, well, an access-access panel, for want of a better word?

Well, the theory is that an access-access panel – even, say, a metre-square panel held in place, for example, by maybe 200 screws around the flange, can still be rigid enough to form part of a structurally stressed-skin. Whereas a QA panel needs to be – well, quick-access. And ideally, for BLOODHOUND, not structurally stressed.

Except that in BLOODHOUND there is no part of anything – bone or skin – which is not stressed. Okay, most of the rear fuselage panels over the space-frame are technically ‘non-structural’ – but the airflow pressures flowing around BLOODHOUND beat at them just the same. Some pressures very high, some very low – and some shifting from high to low as speed mounts and the shockwaves build up and move the pressure zones. So you are never going to thump an access-access panel anywhere on BLOODHOUND and hear a hollow bong – you’ll hear a solid thud, just as you will on a jet fighter panel. Or a Challenger tank panel.

QA panels can also be stressed structural components, but obviously the problems are greater. The complication and cost increases by the square root of the stress-level involved – which you may have to live with. But what also increases… is the weight.

It is an immutable fact of high-speed life that holes are heavy. At a glance this may sound silly, but think about it a moment. Every access panel has to be strong in its own right. So may – indeed almost always will – need at least need some extra bracing inside it. And every access panel requires at the very least a flange behind it to attach it to. And screws to so attach it. And possibly an internal structure to brace the flange, particularly in the case of quick-access panels. And then the QA catches themselves…

Oh yes, holes are heavy.

And that’s just at the back end, where the main stresses are taken up by the space-frame. In the front end things are different…

The front end – from just behind Andy’s seat forwards – is all carbon-fibre composite sandwich structures – in other words all stressed-skin. (See: Wattle and Daub). Immensely, immensely tough – but since it is monocoque construction relying hugely on skin-laminate strength, any holes are a much more serious proposition, because they interfere with structural stress-flow and therefore require much more space-age fortification to compensate.

Want to prove it? Okay, try this for yourself. It will cost you one egg.and a mucky hand. Put the roundy end of the egg into your palm and the pointy end into your fingers, and squeeze. Unless you’ve got a much stronger paw than mine, chances are you won’t break it. Don’t believe me? Try it. An eggshell is nature’s stressed-skin, unlikely as it may sound.

Okay, now put a blemish in the eggshell. Say, pushing a small needle into it. Anywhere – doesn’t matter where – and then do the squeezing again. Cracks propogate from the tiny hole and you have a handful of raw egg in an instant. So now wash your hands.

In the BLOODHOUND composites you can cure the hole – but it does put on structural weight. And it does put on thickness.

This is why the composite front end of BLOODHOUND is so much more difficult than the back end from the access point of view. Is it solvable? Yes, it is solvable. But you would like the holes to be as small as possible.

So roll up, roll up, Grumpy and Octopus Man…