Satellites have an electric future

Ion thruster Thrust comes from a stream of charged atoms (ions) accelerated to very high velocities

One of the most interesting trends in satellite production in the next few years is likely to be the wide introduction of electric propulsion (EP).

More and more satellites will be launched not with chemical thrusters to manoeuvre them in space but with ion propulsion units.

We've seen electric engines fitted to scientific spacecraft in recent years, but not so much on commercial satellites.

Boeing has charged out of the box on this one, agreeing to build four "all electric" telecommunications spacecraft for Asian and Mexican operators.

The attraction is mass - or rather, lack of it.

Chemical thrusters require large tanks of propellant; electric engines, while they don't provide quite the same initial boost, do not need anything like the same volumes of fuel and can work for much longer.

The downside is that it takes you longer to put a satellite in its final orbital slot; the big plus, however, is that you get a much lighter satellite.

That weight saving can either be given over to more payload (transponders in the case of telecommunications satellites), or allow the satellite to squeeze on to a smaller, cheaper rocket.

The latter strategy is the one now being looked at seriously for the future of Galileo, Europe's new satellite navigation system.

It needs 30 spacecraft in orbit to operate a full network (with spares); and because Galileo will be an on-going service, there will be an on-going requirement for replacement satellites.

Galileo satellite A Galileo satellite can be produced now for a unit price of about 30m euros

Galileo, as we all know, is a hugely expensive project, costing billions of euros.

Part of that cost comes down to the price of the rockets used to get the platforms into the sky. If that could be tackled, our taxes would go further.

Currently, Galileo satellites are launched two at a time on a Russian Soyuz rocket.

It costs roughly as much to launch those two satellites as it does to build them. So, if you could get a third satellite aboard, you'd suddenly jump to a new cost regime.


Galileo constellation (Esa)
  • Galileo is owned by the EU but is being procured by the European Space Agency
  • Some 30 satellites are likely to be launched in batches in the coming years
  • Galileo will work alongside the US GPS and the Russian Glonass sat-nav systems
  • Europe's full system promises real-time positioning down to a metre or less
  • It should deepen and extend high-value markets already initiated by GPS
  • Some say economies are over-reliant on GPS; Galileo ought to make sat-nav more robust

This week, at the Farnborough International Airshow, the two companies making Europe's Galileo spacecraft put pen to paper on their contractual relationship.

OHB System of Bremen, Germany, and Surrey Satellite Technology Limited (SSTL) from Guildford, UK, can now turn out a Galileo satellite for about 30m euros.

That has come down from roughly 40m euros per spacecraft when they were first engaged to do the job by the European Commission and the European Space Agency.

But getting the cost down much further is really a launch issue, and electric propulsion could be the solution.

"It is feasible to take Galileo satellites up with electric propulsion, if the technology is available and mature enough," commented OHB's Ingo Engeln.

"You need more time to get the satellites in place, of course, but for the next generation this should be no problem."

And Giuliano Gatti, who works on the Galileo project for Esa, added: "It would mean you could get one satellite on Vega, three on Soyuz and up to six on the Ariane 5."

Europe has a lot of experience already in ion engines.

The concept is simple enough. Strip the electrons off a stream of xenon gas atoms so that they become charged (ions). Then put those ions in a magnetic field and accelerate them to extremely highly velocities in one direction to provide thrust for your satellite in the opposite direction.

You may be aware of Goce, the European Space Agency's gravity mapping satellite. This flies so low to make its maps that it must continually fire its ion engine to counteract the wisps of atmosphere still present at an altitude of 260km.

It was launched in 2009 with just a 40kg tank of xenon and is still working.

Goce satellite Gravity mapper Goce has been firing its electric engine non stop since 2009

Of course the penalty is that ion engines put you in the slow lane.

Chemical thrusters might not burn as long, but they give you great initial acceleration and a satellite can be ejected from its rocket and be ready for use in its correct position in the sky in a matter of weeks.

With electric propulsion, it would take months.

"Where the EP variant will come into its own is in the future, once the Galileo system is in place and you have to consider replenishment, perhaps of single spacecraft," commented John Paffett.

"At the moment, Soyuz and Ariane are quite efficient ways of populating a constellation; but what if you have a single spacecraft failure?

"It makes no sense to put an additional four or six spacecraft into an orbital plane. So the question then becomes: how cheaply can you acquire a small launch vehicle, drop a satellite off in any arbitrary orbit and have EP do the transfer from there?"

The contract signed between OHB System and SSTL brings another 80m euros' worth of work to the Guildford company.

OHB also signed a contract with Culham's ABSL at the show. The British company will be providing the batteries that go into Galileo satellites.

Jonathan Amos Article written by Jonathan Amos Jonathan Amos Science correspondent

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  • rate this

    Comment number 52.

    @48 Little_Old_Me

    I hope that it's an inevitability that the tech will be developed. Mostly because of what is an inevitability; the Earth will eventually become uninhabitable. Assuming we don't wipe ourselves out, or some catastrophic natural event doesn't see to us, we will eventually have to fly the nest so to speak. I have confidence that the current tech barriers could be overcome.

  • rate this

    Comment number 51.

    50.JohnSP - ".....What's your dream?"

    A world where we humans, en masse, realise that the great things about life are the very things we have collaborted on (modern medicine, scienftific advances relieving the daily grind of subsitance farming for many et al) instead of near constantly fighting amoungst ourselves for one upmanship......

  • rate this

    Comment number 50.


    I think it's a matter of believing we can do it as we can't ever be sure of future happenings (scientifically impossible). Trends predict the advance of technology (Google 'Moore's law'), the rest is down to our imagination. What's your dream?

  • rate this

    Comment number 49.

    Don't bring Jesus into a scientific debate, he's about as relevant as a stone axe is to modern mining techniques... Medieval minds applying medieval principles and morals on a modern world, I can't think of anything more backward for inspiring modern thinking. Religion has a lot to answer for most of it is bad, rather than creating harmony it mostly destroys it. So think on, or change the record

  • rate this

    Comment number 48.

    So many people of scientific thinking seem to think it is inevitable that we'll develop the technoology to travel to deep space.

    But the only rationale appears to be that because technology has improved throughout human history it will carry on doing so forever, at an exponential rate of increase.

    Where's the evidence this will continue ad infinitum to hold true?

  • rate this

    Comment number 47.

    32.Entropic man - ".....The Mayflower settlers bet their survival for religious freedom....."

    Another one of the great misunderstood pieces of human history. The only persecution they were suffering from at home was not being allowed to persecute believers of other/no religions.......

  • rate this

    Comment number 46.

    Dear BIG BANG theorists (the TV programme not the sience): don't bury your heads in tech, look out and up. And then ask: why do we need to make this tech? The important issue is: how can we get the human race to be kind to each other? Where to start (Vs electric motors in space vehicles); how about what beliefs about human beings leads to harmony? I suggest a look at a guy called Jesus.

  • rate this

    Comment number 45.

    @43 Entropic man

    Given the daily actions of the Human species as a whole I think I'd settle on the it's too dangerous hypothesis. Apart from a very small minority most Humans are highly uninspiring, and a highly intelligent species with an equally highly developed morality would likely see us as particularly vulgar and to be avoided at all costs.

  • rate this

    Comment number 44.

    So using Ion engines means Charging more will cost less.

    What's not to like, not before time really.

  • rate this

    Comment number 43.

    "Where is everybody?"

    Perhaps the answer is that money which might be spent on interstellar spaceflight is used instead for pork barrel politics, and that bureaucrats across the universe will only fund radio telescopes to listen, rather than transmit.

  • rate this

    Comment number 42.

    Although, regardless of the specifics of the propulsion system the limit enforced by c means that travelling the sorts of distances we'd require in space would still make the journey one of epic proportions. Only a complete re-write of physics would get us zipping round the universe. The only other idea I've seen is folding space time, but I don't own a singularity generator.

  • rate this

    Comment number 41.

    #40 Drunken Hobo

    Rockets use energy from combustion to heat and accelerate atoms. Ion propulsion uses electrical energy. You want more thrust, put in more energy from nuclear fusion or whatever to heat and accelerate more atoms.
    Alternatively, you could decouple the ship from the Higgs field, reducing its mass and inertia, and giving more acceleration from the same specific impulse.

  • rate this

    Comment number 40.

    38 Entropic man
    "I can think of no conceivable rocketry development capable of coming anyway near that."

    Just as well, you'd be in danger of winning a Nobel Prize if you could!

  • rate this

    Comment number 39.

    #36 Andy S, #37Under-Used
    "Anyone tell me why the BBC have no reports on the massive solar flare eruption from the sun on Thursday, thats due to hit earth in the next few hours?" is reporting that the storm may give some increase in aurora activity, but is not generating high enough ground currents to be a problem.

    Alas, its no longer newsworthy, except to us.

  • rate this

    Comment number 38.

    #33 Drunken Hobo
    "at 1g, it would take "only" 3/4 of a year to reach 0.8c"

    A Saturn 5 accelerated 1% of its total mass to 18,000 mph in 15 minutes at 3G, a 1G endurance of 45 minutes. It mostly burnt fuel accelerating fuel.
    Your spacecraft would have to match a Saturn 5 for nearly 10,000 times as long. I can think of no conceivable rocketry development capable of coming anyway near that.

  • rate this

    Comment number 37.

    @36 Andy S

    I wondered that too. Especially as it hit X1.4 which from my understanding is a pretty big deal.

  • rate this

    Comment number 36.

    Anyone tell me why the BBC have no reports on the massive solar flare eruption from the sun on Thursday, thats due to hit earth in the next few hours. On Thursday morning on BBC news the presenter said, "and coming up, the solar flare", blah, blah and then... nothing? And then you did re-runs of John Terry leaving court all day AND evening. Its about time you changed your format.

  • rate this

    Comment number 35.

    @ powermeerkat

    the developments of Teflon or Velcro as spin-off of space activities are pure urban legends, as can be easily found with a simple search

    [which does not diminish the value of space activities, in fields such as telecom, Earth observation, navigation.. ]

  • rate this

    Comment number 34.

    @32 Entropic man

    Sure; I'm one of those people myself. I'm merely questioning the practicalities not the instinct or romance or endeavour etc. It's a shame really as I'll be long dead before the chance becomes even a remotely possibility.

  • rate this

    Comment number 33.

    30 Entropic man - Accelerating at 1g, it would take "only" 3/4 of a year to reach 0.8c (ignoring relativistic effects).
    This is of course assuming technology capable of doing that, which may be a few thousand years away...


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