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UK to 'power' European space activity

Jonathan Amos | 17:54 UK time, Thursday, 23 July 2009

The European Space Agency has opened its new technical centre in the UK. It's an important moment for Britain.

The UK is the fourth largest contributor to Esa's budget and yet, until now, it's been the only big member-state not to host one of the agency's technical or administrative centres.

The Diamond Light SourceThe new unit is based at the Harwell Science and Innovation Campus near Oxford. It's the site of the huge Diamond synchrotron light source, among other tenants.

Harwell has a private-public ethos - where commercial companies and public institutes rub shoulders. The intention is that they're supposed to spark off each other.

Esa hopes this approach can help pull new ideas into the agency, and also spin-out new products and services to business.

And one particular expertise the agency wants to acquire at the new Harwell unit has caught my eye - novel power systems.

We're all familiar with the solar panels that spacecraft carry. These take the light energy from the Sun and turn it into the electricity needed to drive the onboard systems, including the all-important scientific payload.

These panels work well in the inner Solar System, but move further out or land on a planet which rotates through day-night and seasonal cycles and you start to encounter problems.

Take Jupiter, for example: its orbit is five times further from the Sun than Earth's. This means a spacecraft at that distance receives 25 times less sunlight than in Earth orbit.

The European Rosetta spacecraftEurope is sending its Rosetta probe to meet a comet out near Jupiter. It has to fly with two 14m-long solar arrays to gather enough solar energy to run its systems.

Rosetta shows it's do-able, but Jupiter really is the limit. Go beyond the gas giant, to Saturn or Neptune say, and solar panels will not give you sufficient juice to warm the spacecraft and run a worthwhile science payload.

And that's where radioisotope systems come in, using the heat given off by unstable atoms either to simply maintain an operational temperature on the spacecraft, or to go one step further and use that heat to generate electricity.

The first system is referred to as a Radioisotope Heater Unit (RHU); the second is what is known as a Radioisotope Thermoelectric Generator (RTG).

Both generally use plutonium dioxide as their radioactive source.

The Nasa-Esa Cassini spacecraft in orbit around Saturn today would not be working without its RTG technology. Europe's ExoMars rover which is planned for the next decade will need an RHU to stay warm enough to function on the Red Planet's surface.

If Esa were launching ExoMars tomorrow it would have to get an RHU off the Americans or the Russians. Europe has no real experience in dealing with these space systems.

Step forward Harwell. It will be tasked with developing that competence.

The ExoMars roverThose who know their atomic history will recall that it was this part of the Oxfordshire countryside which led the UK's post-war civil nuclear programme. It was at Harwell where Nobel Laureate John Cockroft set up the Atomic Energy Research Establishment.

The AERE eventually gave way to the UK Atomic Energy Agency, a tenant at the innovation campus and one of the partner organisations helping to develop it.

Now, I know some people will take a particular view on space radioisotope systems, as was evidenced by the fuss when Cassini made its Earth flyby on its way out to Saturn; but it should be stated clearly: RHUs and RTGs are not the nuclear fission devices you find in power stations. They work in a different way, harnessing the heat of natural decay.

What's also clear is that Harwell will not, in the first instance at least, be handling any radioisotopes on site. It is expected this will all be done in those companies across Europe which produce radioisotopes for medical use, for example.

What Esa's Harwell centre will do is lean on the local heritage and present-day expertise to forge a new capability for the agency, to become its technical lead and knowledge base for these new systems.

cassini.jpgAs the director general of Esa, Jean-Jacques Dordain, told me this week:

"If we are going for robotic exploration, we need power sources; and anything we can do not to be dependent on other space partners for such important aspects of a mission is very important to Esa."

Harwell will not focus solely on radioisotopes; it will also work on new solar cell and battery technologies, which have obvious benefits to all.

It's a truism that if it works in space, it will work anywhere; and the difficulties of making systems perform in that extreme environment forces one to be innovative. In other words, pursuing space research has spin-offs for the technologies we use on Earth everyday.

So standby: future Esa missions are likely to be leaving Earth with new power systems whose development has been led from Britain.

(And before I close this post, if you want to see what one UK company is already doing with space power systems, take a look at ABSL Space Products which is based down the road from Harwell in Culham.)


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