Overnight we agree that it's okay for me to use sodium
bicarbonate (baking soda) rather than sulphuric acid,
so this morning the race is on to produce some more
oxygen and hydrogen to test on camera. We also have
to produce as much hydrogen and oxygen rocket fuel as
we can. This proved difficult. The ‘graphite’
electrodes we’ve been using – the ‘lead’
from pencils – were found not to be pure graphite.
We tried the ‘lead’ from different types
of pencils, and all of them corroded away after a short
time in our electrolytic cell. Luckily, the place that
is our workshop is used for car maintenance, and Jonathan
(Hare) manages to find a graphite bush on the floor!
We can cut this up to make perfect graphite electrodes.
Good old J – he saves the day. We’ve still
a problem though, as we only have copper wire to connect
the electrolysis cell to our power supply, and under
these conditions bare copper will just dissolve away
in our cell. We have constantly to strip the ends of
the electrode connections and expose some fresh copper
to maintain any kind of effective circuit. We get there
though; by 3 pm we have the job done, and we’ve
collected lots of one-litre pop bottles full of our
rocket fuel; a 2:1 hydrogen:oxygen mixture.
It’s time for a test launch of our hydrogen/oxygen-powered
rocket. With a one-litre bottle full of the 2:1 hydrogen:oxygen
mixture, we managed to reach a height of about 5m. With
two-litre bottles, however, the explosion of the hydrogen/oxygen
mixture generates so much heat that it deforms the PET
(poly-ethene teraphthalate) from which the bottles are
made. To make matters worse, these larger bottles don't
even lift off the launch-pad on ignition. Unfortunately,
even though the smaller, one-litre bottles work well
on their own, they just don’t have enough thrust
to carry the required payload – an egg, a parachute,
and a small camera. Kathy’s water-pressure rocket
on the other hand is just perfect. It can generate enough
thrust to fire a two-litre bottle to a height of about
10m, even with the payload on board.
By contrast, poor Jonathan’s not had much luck
with his steam rocket by the end of this second day.
Even if he fails to get his design off the ground by
late tomorrow afternoon, we'll still have Kathy’s
design to fall back on though.