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Faster than a speeding bullet...In 2014 a small team from the UK
will dispatch a car to Africa with the aim of it speeding across
the desert at 1000mph. We find out how chemistry powers the car to
success.Josh Howgego
14 | Education in cHEmistry | May 2012 www.rsc.org/eic
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weak intermolecular forces. The strength of the material is
therefore highly anisotropic that is, not the same in all
directions. The challenge for the engineering team is to work out
how to weave carbon fibres into composites so that the directional
strength of the carbon-carbon bonds is best exploited.
PowerAnother interesting challenge the team faced was how to
power the car. In the end they have opted for two power sources; a
Eurofighter Typhoon jet engine, which will power the car up to a
speed of about 350mph, and then a rocket the largest ever built in
the UK.The projects rocket engineer is
Daniel Jubb. Despite Bloodhounds educational overtones he is not
the most traditional advert for school he left at 13 to be home
schooled and start a rocket engineering firm with his
grandfather.Like many boys the young Jubb
had a passion for pyrotechnics, but rather exceptionally he had
managed to launch over 100 rockets by the age of 10. My grandfather
and I would drive out to the test site with several different
[rocket] configurations that wed come up with ready to go, Jubb
tells me, wed fly several of them to try and get some performance
data points. The
which prompted the team to choose the softer desert surface of
the Hakskeen Pan in South Africa. This is essentially hard-baked
mud, and will allow the wheels some lateral grip.The final choice
for the wheel
material was aluminium. Aluminium is extremely light (2.7gcm-3)
and strong, but slightly softer than rival material titanium, which
is prohibitively expensive.
The bodySections of Bloodhounds shell are made from different
materials, carefully designed to fulfil different roles. The most
important part is the carbon fibre shell that forms Bloodhounds
nose and protects thepilot.Carbon fibres are made from thin
sheets of graphite woven into a strong polymer to create a
filament. They are extremely strong (see table) in tension along
their axes (because of the strong carbon-carbon bonds) but, the
layers of graphite like those in a pencil are only held together
by
In an unassuming, square brick warehouse, a team are building a
car which will travel at 1000miles per hour. Called Bloodhound,
this13metre long machine is the brainchild of Richard Noble, a man
who knows what its like to be the worlds fastest man, having driven
Thrust2 at a speed of 633mph (not quite the speed of sound) in
1983. But it seems that its not (just) a desire for insane speed
that drives him.
Reengineering our livesNobles goal with the Bloodhound project
is to inspire a new generation of scientists and engineers. He was
inspired by the Apollo effect during the space race of the 1960s
the excitement hugely increased the number of young people wanting
to study science. You cant excite people with electric cars and
wind turbines says Noble. A 1000mph car might just do it
though.There is also a serious side to the
mission. What is the single biggest threat facing us today?
Noble asks in a recent video on the projects online TV channel
(http://bit.ly/z2Ffde). In short, Noble thinks challenges like
cutting emissions and supplying food to a growing population demand
bold ideas from scientists and engineers and at the moment there
arent enough of them to try.
Bloodhound is a daring and imaginative project from whatever
angle you care to come at it. This is the mother of all research
projects; there are lots of scientific problems the team need to
solve.
WheelsAt 1000mph Bloodhounds wheels will spin at about 170times
a second, and generate a stress of about 50k times the force of
gravity (g) at the rim. Although some older land speed cars have
used inflated tyres, for Bloodhound the stresses involved mean only
a solid wheel can cope.However, a solid wheel largely
determines the surface the car will run on. Land speed records
are often attempted on salt pans, which are very flat and very
hard. This gives good grip but little friction, and is ideal for
high speeds. Since Bloodhound will use solid wheels, a salt pan
could be dangerous. With no give in the wheels at all, any tiny
irregularities in the surface could cause a big bump. It was this
factor
In short Inabidtobreakthe
worldlandspeedrecord,theBloodhoundprojectaimstoinspiremoreyoungpeopletostudyscience
Bloodhoundispoweredto1000mphbyanHTPfuelledrocket
material Density gcm3
Tensile strength mPa
Youngs modulus
Aluminium 2.7 280 0.1
Steel 7.8 400 0.05
Titanium alloy 4.6 950 0.21
Carbon fibre 1.6 2000 0.91
Daniel Jubb, rocket engineer (has a moustache most men would
kill for and a job title to match) demonstrates to eager
onlookers
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1983 Richard Noble pilots Thrust2 to a speed of 633mph.
1997 Thrust Super Sonic Car (SSC), piloted by Wing Commander
Andy Green is the first car to break the sound barrier, racking up
a nimble 763mph.
2000 (Exact date not disclosed). Americans begin work on a rival
landspeed record attempt project; the North American Eagle
which
aims to reach a speed of 808mph and wrestle the title from the
British. Spookily, the NASA-starfighter from which the craft is
built has the tail number 763, which is the current land speed
record in mph!
2007 American adventurer Steve Fossett disappears whilst in the
final stages of preparing an assault on the record with his car
Sonic Arrow. The car is currently
up for sale and there are rumours of an unknown buyer. Fossett
is believed to have been killed in a plane crash.
october 2008 The Bloodhound project gets the go ahead from
science minister Lord Drayson who says there is every possibility
that the Bloodhound team will reach the absolute speed limit for a
car on wheels.
oxidiser) and liquid hydrogen (the fuel). Bloodhound chose a
different route a hybrid rocket, using solid fuel rods made from a
synthetic rubber and a liquid oxidant.Initially we thought that
nitrous
oxide [(N2O) or laughing gas] might be the way to go for the
oxidant explains Jubb. We also considered nitrous acid (HNO2) and
looked at the classic combination of kerosene and liquid oxygen.
But eventually we decided upon HTP.HTP (High Test Peroxide) is
an
86% solution of hydrogen peroxide (H2O2) in water, and
Bloodhound will carry 963kg of the stuff. HTP gives off oxygen in
the following decomposition reaction:
H2O2 H2O + O2 + heat
Because the reaction is so exothermic, the water produced is
immediately converted into steam which expands quickly and is
forced through an aperture, producing thrust. Initially the HTP is
just allowed to trickle over a silver bead catalyst pack, which
helps initiate the decomposition reaction. In phase two, the flow
of HTP is increased. To generate the level of power that Bloodhound
needs (about 122kN of thrust), it must be very fast, so engineers
have installed an engine from a Formula 1 car to pump it across the
catalyst pack. This raises
value on being able to stop the car if anything goes wrong. And,
of course, it had to be as safe as possible.A rocket is essentially
a
combustion reaction in a tube, so it requires three things:
heat, oxygen and a fuel. A rocket is an enclosed space, so it must
use an oxidant in this case a compound that reacts to give off O2
to provide the gas consistently during the firing.
FuelThe first decision to be made was about the physical state
of the fuel and oxidiser. Most rockets use liquid fuels. The space
shuttle rockets, for example, used liquid oxygen (the
way we had more fun was to build a faster and better rocket and
the way we got there was to use a scientific approach.
The chemistry of rocketsJubb and the Bloodhound project had to
consider several different options before eventually achieving the
right balance for the cars rocket. There were some quite exacting
requirements; it had to be quite short burning, but reach maximum
thrust (for maximum acceleration) as quickly as possible. An off
switch was essential because the pilot, Wing Commander Andy Green,
places great
Land speed record timeline
16 | Education in cHEmistry | May 2012 www.rsc.org/eic
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Intriguingly the speed of sound is dependent on air temperature.
Sound is essentially vibrational waves in matter (in this case the
air). If the air is cooler it has less energy and the particles
(oxygen and nitrogen molecules mostly) move less quickly. This
means at cooler temperatures sound travels more slowly through the
air. (See also http://bit.ly/xuegKm).This is why land speed record
teams sneakily
try their runs early in the morning when the air is cool. The
lower the temperature the better: at 15C the speed of sound is
761.2mph. At 25C its a little higher: 768mph. Although of course
this doesnt change the absolute speed of the car, it does alter the
Mach number (M), which is defined for a given temperature as:
M = actual speed / speed of sound
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concentrated nitric acid and then careful testing with
increasing concentrations of H2O2.Chemistry is central to the
rocket
powering Bloodhound, but Jubb has called on other areas of
science to fully understand how the rocket works, such as the
dynamics of the superheated gases. The project team had to
understand the kinetics of the reaction to work out how fast the
rocket will burn. They designed an entirely new computer program to
simulate this, which could prove useful for rocket design in other
applications.
The legacy will be ...?Bloodhounds influence could reach far
beyond itself, into education, engineering and through the
scientists it inspires, to all the unimaginable inventions and
innovations they will create. Bloodhound aims to break the 800 mph
record in 2013 and reach 1000 mph in 2014, but for the long lasting
benefits of the project, we may have to wait a little longer.
Josh Howgego is a chemistry PhD student and writer based in
Bristol.
Further reading The Bloodhound project
http://www.bloodhoundssc.com
Bloodhound education, including free resources for schools
http://bit.ly/bldeduc Development of the Bloodhound hybrid rocket
http://bit.ly/bldhybrkt
(H=98kJmol1) as the bonds formed release more energy than is
required to break the H2O2 bonds.Consequently, the reaction is
thermodynamically spontaneous it takes almost nothing to get it
going. That means the aluminium tanks which store the HTP have to
be passified to remove any nucleation points which could set the
HTP going (chromium ions from stainless steel components are a
particular worry says Jubb). The passification involves a rigorous
regime of ultrasonic cleaning, immersion in
the temperature to 600oC which is enough to ignite the rocket.
This technique keeps Andy Green happy because, if he does feel the
need to abort the run, he can switch off the HTP pump and the
rocket will quickly run out of oxidiser.
Spontaneous reactionThe strength of H2O2 as a fuel is also its
downside: the decomposition is so favourable that H2O2 is
dangerous. The reaction is entropically favoured (S=70Jmol1K1) and
enthalpically favoured
The speed of sound
The desert surface of the Hakskeen Pan, South Africa where
Bloodhound will reach speeds of over 1000mph
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The vision for the Bloodhound project is to inspire a new
generation of students to become scientists and engineers. To help
achieve this aim, the project is supported by a website full of
free information and resources.You can register for the
Bloodhound Education Programme and become involved with the
project by filling in your details here: http://bit.ly/bldeduc This
will give you access to a huge range of teaching
materials and full open access to the design, build, test and
record breaking attempts of Bloodhound.
More inForMationThere is much more on the Bloodhound website
which will be of interest and help to engage students with science
and engineering: Careers information
http://bit.ly/bloodhoundcareers Facts about the car
http://bit.ly/bloodhoundcarfacts Video interviews with the design
team http://bit.ly/bloodhoundinterviews Projects you can be
involved with http://bit.ly/bloodhoundopportunities Events
showcasing Bloodhound and its technologies
http://bit.ly/bloodhoundevents
Why not use the Bloodhound story as an introduction to teaching
catalysis? As the article describes, the car uses the catalytic
decomposition of H2O2 as an important source of thrust.This
classroom experiment gives a very
visual demonstration of the relative properties of some
potential catalysts for decomposing H2O2. Several measuring
cylinders are set up each containing a little washing up liquid and
a small amount of a catalyst.
Hydrogen peroxide is poured into the cylinders and a foam rises
up the cylinders at a rate that depends on the effectiveness of the
catalyst. Download the instructions from Learn
Chemistry at http://bit.ly/H2O2demo, or watch the demonstration
at http://youtu.be/Ta4DomSDzF8This demonstration is also available
as
a guided investigation for students. A worksheet and teacher
notes are available at http://bit.ly/H2O2invest.
Teaching catalysis Free resources for schools
The Bloodhound Team
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18 | Education in cHEmistry | May 2012 www.rsc.org/eic