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Amateur Rocket Heads Into Space
scubacuda writes "Space.com has an article on a group of amateur rocketeers (the Civilian Space Xploration Team) hoping to send the first amateur rocket, Primera Spaceshot 2002, into space by the end of June from the Black Rock Desert in Nevada. If all goes well with the Federal Aviation Administration (FAA), the team will send a rocket stands about 17 feet tall (5.18 meters) and weighs 550 pounds (249 kilograms) 62 nautical miles (114 kilometers) in the atmosphere (12 miles higher than the 50-mile altitude largely regarded as the boundary of space). (MSN version here)"
HPR people have been scaling up solids (using AP&rubber - basicly the same stuff the shuttle boosters use) for over a decade now - big AP rockets are not that unusual these days and have been flown to at least 100k ft (20 miles) - they are just expensive to build (propellent can cost several $1000).
100kft is a magic number - at that point the FAA loses juristiction (we fly the smaller stuff with FAA waivers) and you have to apply to a different part of the federal govt. - the paper work is pretty intimidating - it's designed to stop people dropping dangerous things on other countrys and causing international incidents.
Building amateur liquid propellent motors is hard - you have to get the fuel and oxidiser into the combustion chamber - that means a pressure higher than the chamber pressure - either a turbo pump - or a pressure system of some kind (for example gaseous O2 as an oxidiser at a high pressure, or an inert gas say N2 at pressure pushing a liquid say LOX or kerosene) pressure systems mean more weight.
One system we have been flying with recently is a hybrid based system - a liquid oxidiser with a solid fuel (basicly the combustion chamber's wall burn). It turns out that nitrous oxide (yes laughing gas) is a room-temp cryogenic liquid that self-pressurizes at above chamber pressure - this means it self-pumps and can be throttled. Paint ball tanks make great light-weight pressure vessels and nitrous is available at your local speed shop, flights are cheap. It does have some downsides - it burns so efficiently that rockets make no smoke and are hard to track, it's also hard to light (of course it gets real cold when it expands).