Venerable ‘Aunty’ BBC in it’s unerring quest to write-off the sciences in this country has a new article in it’s ‘magazine’ section entitled: “How to build your own Sputnik”.

Now, you might expect a bit of practical information here about how the original Sputnik-1, launch in 1957, was actually constructed and what sort of design considerations would be necessary to ensure your “DIY Sputnik” does not fail…

…unfortunately not.

The BBC article roundly suggests that a DIY Sputnik could be constructed from ‘off the shelf, retail components. The DIY Sputnik of the BBC article is housed in a “biscuit tin” (with foil!) and consists of a Tomy* Baby Monitor, a Mercury Thermometer, 4x large batteries, a party balloon, a backup “power pack”, a domestic thermostat and a battery powered fan.

*Quite why Tomy is the brand recommended by the BBC for this design is something I’m yet to discover.

Now, I can understand why you’d want the batteries, thermometer, thermostat and fan. The batteries are quoted as being ‘large’. You do not want your batteries to be large. You want them to have a good lifetime but you do not want them to be any bigger than absolutely necessary. It is also suggested in the article that your Sputnik should carry a ‘backup’ power pack. I’d suggest that this is unnecessary mass; whatever causes your primary power cells to fail would probably also cause your backup cells to fail in this sort of mission - probably explosive decompression or overheating but I’ll get on to that later too.

The thermometer seems like a good idea, you would want to monitor the temperature inside the biscuit tin. However, the BBC article suggests a mercury thermometer which could be a little hard to read when your Sputnik is way up there and you are down here. Perhaps a simple thermocouple, the most common form of electronic temperature sensing, would be a better idea?

Then there’s the thermostat (for turning the battery operted fan on no less). The BBC article stipulates a ‘Domestic thermostat’. Isn’t this rather eccentric considering that most domestic thermostats require mains voltage and the fan it would be switching would be a low powered DC affair? You’d need an inverter just to power the thermostat.

The fan itself is a relatively good idea, Sputnik 1 had one and it serves the purpose of moving heat around the casing to avoid excessive localised heating and providing some thermal management of the electronics suite. You’d wan’t to be rather careful on the size, mass, type and fitting of your fan tho. When your fan spins up (controlled by your thermostat) it will impart spin on your whole sputnik. This may make correct orientation rather tricky.

There is a wireless access point included in the inventory. I’m at a bit of a loss as to why it is here, there are no computers on board and it’s unlikely anyone will be ‘wardriving’ in LEO.

Now we come to the curious inclusion of a party balloon and a baby monitor (Tomy is best I am told). The article explains that the balloon, if slightly inflated before launch could be used as a ‘pressure sensor’.

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

Sure it can! That’s why you wanted Tomy’s finest on board isn’t it? So you could hear the balloon pop! Only that wouldn’t work, would it? Anyone who was awake during their school physics lessons should be able to tell you that if the pressure was zero your baby monitor wouldn’t hear a thing as no sound can travel in a vacuum.

We’ll give the author the benefit of the doubt here though and assume the balloon ruptures prior to the pressure reaching near-vacuum so at least a small sound reaches the baby monitor.

It still doesn’t work. As the pressure dropped, some small components in your Baby monitor known as capacitors will have been expanding, rupturing and distorting leading to its demise. If that doesn’t stop it working, you could be pretty certain that the consumer power cells you obtained ‘off the shelf’ will have already ruptured and stopped providing power. Most people would just fit a barometric switch (just like Sputnik 1!)

But that’s all a bit beside the point. This thing is housed in a biscuit tin (according to the helpful BBC diagram). Now while many containers have been designed to withstand a vacuum, biscuit tins are not one of them.

Sputnik 1 was constructed within two metal hemispheres, hermetically sealed together with 0-rings and a bolted flange. It was designed from the ground up as a pressure vessel in it’s simplest fashion.

Even if you could somehow seal the lid of a biscuit tin up properly, the whole thing would explode the moment it was exposed to a vacuum as it just doesn’t have anywhere near the structural integrity required to sustain the difference of 1 atmosphere.

The casing of the real Sputnik was also designed to withstand the extensive heating of the sun. Don’t forget, your satellite will be exposed directly to the sun for more than half of the time it is up there (the higher the altitude, the greater the duration of exposure per orbit). The article intimates that this sort of casing may prove hard to come by but helpfully suggests using ‘foil’.

The real Sputnik used a polished 1mm thick layer of aluminum-magnesium-titanium. Perhaps just a little out of the price range of the average ‘Blue Peter’ creation (unless they have another phone-in)

The article rambles on about how LEO is littered with ’space debris’;

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.

It’s not quite that crowded up there you know. Your [inert, depressurised]biscuit-tin Sputnik will be a small device and as such present a very small surface for collision. Vehicles such as the Space Shuttle and ISS are pretty big and are actively moved away from larger pieces of space debris and designed to withstand hits from very small ones. They, of course, present a large surface area and are many more times more likely to conflict with debris.

What’s really going to kill your ‘DIY Sputnik’ (other than the general stupidity of its design) will be re-entry. At the 134 mile periapsis of the original Sputnik 1, your biscuit-tin-in-the-sky will be experiencing the drag of the upper-atmosphere. This will gradually and inexorably reduce the orbit until the buiscuit tin, baby monitor and all, burn up due to the frictional heating of the atmosphere.

At this point I’m thinking this is just a sort of excercise for the reader (or the reader’s kids) to undertake and place down the garden on a simulated ‘mission’ but no…

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.

This is something you should really consider before opening your mouth. As a back-of-the-envelope calculation, I reckon, to launch Sputnik again (83.6kg) to LEO using a dirt-cheap Zenit launch would cost in the region of £160,000 if bundled up with other paying payloads.

Do they really intend to burn the license-fee payers money firing buiscuit-tins into LEO?

I’m of the opinion that the article’s suggestion that a satellite can be built with commodity components of this level and with no apparent engineering skill is nothing short of fantasy. The ‘bad science’ (or complete lack of science) thrown in for good measure is insulting.

Satellites, at the very least, remain outside the grasp of the general-public’s purse and engineering capabilities. The expertise and funding still required to produce even a minimally functional satellite remain the preserve of academic institutions, corporations and governments.

The original BBC article can be found here

Tags: bad science, bbc, diy sputnik, farce, sputnik