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Mini ionic motor to set small satellites free


April 2, 2012

The ionic motor developed at EPFL is designed to extend the capabilities of the new genera...

The ionic motor developed at EPFL is designed to extend the capabilities of the new generation of nanosatellites

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Researchers at the École Polytechnique Fédérale de Lausanne (EPFL) have created a prototype mini motor designed to extend the capabilities of the new breed of small satellite. The motor weighs roughly 200 grams (7 oz) – including the fuel and control electronics - and could be used to change the orbit of small satellites, or even propel them to more far flung destinations that would usually require larger, more expensive spacecraft.

Designed to provide the new generation of nanosatellites with an efficient propulsion system that would grant them true autonomous capabilities and allow them to carry out exploration or observation missions, the new mini motor can be mounted on satellites as small as 10x10x10 cm (3.9x3.9x3.9 in).

“At the moment, nanosatellites are stuck in their orbits,” says Herbert Shea, coordinator of the European MicroThrust project and director of EPFL’s Microsystems for Space Technologies Laboratory. “Our goal is to set them free,”

Instead of combustible fuel, the motor runs on a chemical compound known as EMI-BF4. This is an “ionic” liquid, from which the electrically charged ions are extracted and then ejected to generate thrust.

The prototype ionic motor that could be integrated into small satellites

In the EPFL mini motor, the ionic liquid is drawn from a reservoir using capillary action and directed to an array of tiny silicon nozzles. These nozzles are so small there over 1,000 of them per square centimeter (0.15 square inch). The ions are then extracted by an electrode held at 1,000 volts, and accelerated before being emitted from the back of the satellite at speeds of around 40,000 km/h (24,855 mph). To ensure that both the negative and positive ions are ejected, the polarity of the electric field is reversed every second.

While the ionic motor only provides acceleration of around a tenth of a millimeter per square second – or roughly 0-to 100 km/h (62 mph) in 77 hours – it is the steady acceleration in frictionless space that can see a microsatellite increasing from its launch speed of 24,000 km/h (14,913 mph) to 42,000 km/h (26,098 mph) after six months of acceleration. Just 100 ml (0.02 gal) of propellant would be enough to take a satellite to the Moon in six months.

The electric field is reversed every second to eject both the negative and positive ions

The ionic motor is due to power the kamikaze CleanSpace One nanosatellite that will clean up space debris by grabbing it and dragging it out of orbit into Earth’s atmosphere so both the nanosatellite and space debris are incinerated on reentry. It will also be used on a swarm of Dutch nanosatellites that are being sent to record ultra-low frequency signals on the far side of the Moon. The EPFL team plans to finalize their ionic motor design in around a year, before it is used on CleanSpace One in three to four years.

Here's a video from EPFL with Herbert Shea describing the ionic motor.

Source: EPFL

About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag.   All articles by Darren Quick

I wonder - if the tank was large enough - just how long would the motor last and in what form would the degredation proceed?

Mr Stiffy
2nd April, 2012 @ 05:23 am PDT

At an average of 36,000 kph it would go to mars and back in 6 months. It would get to the moon in hours.

Gethin Coles
2nd April, 2012 @ 06:15 am PDT

@Gethin Coles - You could at least READ the article.....

As for the article (which I read) this is great news for anyone who wants ANYTHING in space, making it much cheaper to operate, and to achieve its desired orbit. Also, its great that they plan on taking old satellites and dragging them back to earth for re-entry...it's getting a little crowded up there and we certainly don't need it any worse.

Derek Howe
2nd April, 2012 @ 03:52 pm PDT

My first thought is: could this engine be attached to incoming space rocks to steer them away from a collision course with earth?

Ron Turpin
2nd April, 2012 @ 08:28 pm PDT

@derek Howe what makes you think I didn't read it? It states launch speed 24,000 kph. The moon is about 360,000 km away. Oh wait... I was forgetting about escape velocity. In which case the article should mention that it will take 6 months to reach escape velocity. If its was launched at escape velocity, it really could get to mars in a few months

Gethin Coles
3rd April, 2012 @ 06:29 am PDT

how about tow a space pod with some passengers in it around space for a year or two

3rd April, 2012 @ 10:24 am PDT

You forgot to state the MASS that is being driven / accelerated - and whether that includes or not the mass of the engine and propellant it's self.

"While the ionic motor only provides acceleration of around a tenth of a millimeter per square second – or roughly 0-to 100 km/h (62 mph) in 77 hours"

Mr Stiffy
4th April, 2012 @ 03:08 am PDT

Gethin coles I am pretty sure they have got their numbers right it. The speed of 24,000 most likely is keeping the satellites in a stable orbit. 24,000 km/h (14,913 mph) to 42,000 km/h (26,098 mph) after six months of acceleration. so when it starts going to the moon it is really not going at a speed of 24,000Km/h as space travel is not what I do for a job nor is understanding the sling shot effect so I cannot cast doubt on their numbers. But one would think those who are making this Mini ionic motor are the ones who know what it can do so no more BS if they leave out numbers and you want to try to be smart find the numbers they are out there. Otherwise don’t make up stats, you are like a person trying to find out how long a plane takes to go from one city to another by using airspeed as ground speed when the plane is flying in to a strong wind.

Lachlan Palmer
4th April, 2012 @ 03:40 pm PDT

I'm pretty sure that the whole point of this thing is that they don't have to strap it to a gigantic heavy-lift rocket with multiple orbital stages to get it to escape Earth's orbit. Some of you seem to be missing the point here. :P

Will Sharp
11th April, 2012 @ 09:33 am PDT
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