It seems incredible that the technology that went into building the first successful satellite 50 years ago can now be found lying around the average house. You could even build one yourself, as Paul Rubens explains below. Fancy having a go? Then, sign up to the Magazine's Sputnik Challenge at the bottom of this page. THE SPUTNIK CHALLENGE Do you fancy having a go at building your own Sputnik? This article explains how it could be done If you fancy having a go, sign up to the Magazine's Sputnik Challenge using the form at the bottom of this page We could even pop along to film your efforts And we'll investigate how to get your DIY Sputniks launched

What a DIY Sputnik might look like In 1957 the Sputnik 1 satellite was seen as a technological marvel, the result of many years work by some of the Soviet Union's most talented engineers and scientists. But by today's standards, was it really such a big deal? In 2007, how hard would it be to build a fully working Sputnik in the comfort of your own living room? In simple terms, the Sputnik satellite was a metal sphere almost 2ft (61cm) in diameter, containing a radio transmitter. It also had a battery; equipment to measure temperature; barometric and temperature activated switches; and a fan to stop it getting too hot. It sent its famous "beep beep" radio signals to earth, altering the transmission to indicate changes in temperature or a sudden drop in pressure caused by a puncture in the satellite's case. And that's about it. You could probably find most of these components lying around your home. There are transmitters in mobile or cordless phones, wireless internet routers and baby monitors, and you may well have a thermometer in the medicine cabinet. A party balloon can act as a simple pressure switch of sorts - a partially inflated one would certainly expand and burst if the pressure outside dropped to zero. And temperature switches can be found all over the house, including in the thermostat for the central heating system, or in the electric oven or washing machine. Electronic gadgets contain batteries, and fans can be found in home computers or the kitchen extractor. The only thing you may have trouble laying your hands on is a large metal sphere with whiplash aerials poking out. While finding all the components may be easy in 2007, actually getting them to work together would require a little expertise. There's also the small matter of all those wrecked domestic gadgets and appliances left in your wake. SPUTNIK IN A BISCUIT TIN 1. Tomy baby monitor - transmitter and aerial 2. Wireless router - backup transmitter and aerial 3. Mercury thermometer - temperature sensor 4. x4 large batteries - power supply 5. Balloon - pressure sensor (expands and pops if case punctured) 6. Power-pack - backup power supply 7. Domestic thermostat - activates fan and changes radio signal 8. Battery powered fan - moves heat to casing (once tin lid is on) 9. Biscuit tin with foil - houses components and reflects solar radiation

In practice it would probably be better to buy the parts you need from an electronics supply shop. But how hard would it be to get them all to work together? "Technology now is way ahead of what was available in 1957, and making your own fully functional Sputnik would now be very simple indeed," says Jan Buiting, editor of Elektor Electronics, a hobbyist magazine. "I wouldn't be surprised if you could build one in a container smaller than a matchbox, weighing about as much as a wristwatch. The components, including a transmitter, battery and the sensors you'd need would probably cost less than £50," he says. Day's work In principle, you'd need temperature and pressure sensors connected to an off-the-shelf microprocessor. This, in turn, would be connected to the transmitter, and you could get away with one with as little power as half a watt, according to Buiting. Taking the Magazine at their word... do you fancy building a Sputnik? Then you'd need to connect the microprocessor to your home computer and write a little program that takes the pressure and temperature information and encodes it in whatever way you like into the signal sent from the transmitters. Add a battery and perhaps a fan programmed to come on when the temperature rises above a certain level, and you'd have yourself a Sputnik, he says. "It really shouldn't be a problem to build and program the whole thing in under a day," he adds. Once you've assembled your Sputnik box, there's a few finishing touches you'll need to carry out before it's ready to send into orbit. You'll need to put it in a strong airtight shell, because otherwise the pressure sensor would be in a vacuum, with no pressure to measure. Dr Ralph Cordey, a satellite expert at EADS Astrium, Europe's largest satellite builder, says you'll also need to take steps to prevent the electronic components getting damaged by radiation. "You are not looking at the most difficult of environments but I'd recommend some level of shielding," he says. Space debris "Essentially you'd need to pack the satellite in a metal box of some sort to protect it." The colour you choose to paint it could be crucial Further cooling measures would also be prudent, he advises. "The fan will help get heat out of the middle of the satellite to its surfaces, so it can radiate away. But you also need to think about the colour of your space craft, because dark surfaces will heat up if they are facing the sun or a planet." The original Sputnik was powered by over 50Kg of batteries, which kept the satellite transmitting for 22 days. Even though advances in technology mean that batteries - like those found in mobile phones - are now quite light, they will run out eventually, so if you want your Sputnik to transmit for more than a few weeks then the addition of a few solar panels would be sensible. But none of these measures will guarantee its longevity, however. That's because many of the common low-earth orbits are now littered with debris, testament to the many satellites and delivery systems which have followed Sputnik 1 into space over the last 50 years. Without the ability to manoeuvre around these space hazards, it's very likely that sooner or later your home-made satellite will hurtle into a piece of this rubbish and be obliterated. Do you fancy building you own Sputnik? We've given you an idea how easy it could be, now the Magazine wants to hear from willing volunteers. We can even come and film you putting it together. We'll also investigate how to get your Sputniks launched. Name

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