Page 55 - All About Space 68 - 2017 UK

droplets. During the Shuttle's operations it was an considered it not worth the effort, as it needs big
ongoing controversy that this pollution was being insulated tanks because it’s so cold and diffuse,
showered over the Florida waters. By contrast its with ten per cent the density of the kerosene used
three bi-liquids were much less obtrusive, visually by Saturn V, Soyuz and Falcon 9. This is also burnt
and environmentally. When hydrogen and oxygen with oxygen, but produces mostly carbon dioxide. A WORLD OF
are burnt they produce only water, the 3,300 Though best performance is achieved by running INFORMATION
degrees Celsius (5972 degrees Fahrenheit) efflux slightly fuel rich, the extra carbon in the exhaust
of water vapour radiates strongly in infrared but produces the opaque yellow-orange plumes and
little in visible light. This can be seen in footage of slight smoke.
shuttle launches with the main engines producing Possibly the most curious engine characteristic
a transparent blue looking efflux with bluer belonged to the British 'Black Arrow' satellite
shock diamonds in it. Rocket engines produce launcher – in the beginning, it was decided to
a supersonic flow of gas, properly designed, the use kerosene combined with hydrogen peroxide.
high pressure gas in the chamber should reach the Hydrogen peroxide has many advantages - it's 20
speed of sound at the narrow throat, accelerating per cent denser than oxygen and doesn't need
even further as the funnel-shaped nozzles convert refrigeration. It doesn't produce as much energy
the pressure into speed. At the point the gas leaves as kero-ox, but mixes with kerosene at 8/1, leading
the nozzle it should be at the same pressure as the to compact rockets that are mostly one big tank
surroundings, and all travelling straight back from with a little one for the kerosene. Its exhaust is
the rocket. This process also creates the diamond- comparatively cool water and carbon dioxide, so
shaped shockwaves visible in some exhausts. Black Arrow's combustion was invisible, films
Hydrogen is the top end propellant — it produces show the rocket seemingly levitating off the pad
the best performance — but many designers have with no sign of flame. RH

Virgin Galactic's hybrid Hydrogen peroxide Unsymmetrical
Different hybrids have different and Kerosene dimethylhydrazine and
plumes, but Virgin's Nitrous Used in the UK rocket programme, nitrogen tetraoxide
Oxide and rubber hybrid has been eight times the quantity of Used in the Chinese space
nicknamed the 'flying tyre fire' for peroxide burns with kerosene, programme, this combination of
its smoky trail. making an invisible exhaust. chemicals produces a red flame.

WAITING TO BE
DISCOVERED

© Adrian Mann

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