Future tech Bloostar
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Spanish company Zero 2 Infinity hopes to float its rockets past the thick lower atmosphere on balloons
The most demanding part of an orbital launch is not reaching 28,000 kilometres (17,400 miles) per hour in space, but powering through the thick lower atmosphere; this uses a significant part of a rocket’s propellant load and puts stress on the craft. Around 80 per cent of Earth’s atmosphere is in the first 11 kilometres (6.8 miles) of altitude – the height jet airliners fly at – and aerodynamic drag, the force pushing back on the rocket as it flies, depends on the density of the air and the speed of the rocket.
As their speed rapidly increases just after launch, rockets plough through the relatively thick air, experiencing ‘max q’, or maximum dynamic pressure, where aerodynamic forces peak, and many launchers – including the Space Shuttle – throttle back their engines to keep within safe limits. But Spanish start-up Zero 2 Infinity plans to make the launch of small satellites cheaper and safer by cutting out this problem entirely, instead using a balloon to carry rockets above the lower atmosphere.