It’s hard to think of many spinoffs from the $100 billion project to build and launch the International Space Station. In fact, there is precious little done on the ISS that isn’t focused on just keeping the thing in orbit.
One exception is the Alpha Magnetic Spectrometer, which is designed, among other things, to determine whether cosmic ray particles are made of matter or antimatter.
The spectrometer consists of a giant magnet that deflects charged particles and a number of detectors that characterise the mass and energy of these particles. It was bolted to the ISS last year and is currently bombarded by about 1000 cosmic rays per second.
Today, Roberto Battiston at the University of Perugia in Italy and a few pals say that the technology developed for the spectrometer could be used for protecting astronauts from radiation during the long duration spaceflights in future.
The journey to the asteroids, Mars or beyond is plagued with technological problems. Among the most challenging is finding a way to protect humans from the high energy particles that would otherwise raise radiation levels to unacceptable levels.
On Earth, humans are protected by the atmosphere, the mass of the Earth itself and the Earth’s magnetic field. In low earth orbit, astronauts loose the protection of the atmosphere and radiation levels are consequently higher by two orders of magnitude.
In deep space, astronauts loose the protecting effect of the Earth’s mass and its magnetic field, raising levels a further five times and beyond the acceptable limits that humans can withstand over the 18 months or so it would take to get to Mars or the asteroids.
An obvious way to protect astronauts is with an artificial magnetic field that would steer charged particles away. But previous studies have concluded that ordinary magnets would be too big and heavy to be practical on a space mission.
However, superconducting magnets are more powerful, more efficient and less massive. They are much better candidates for protecting humans.
The only problem is that nobody has built and tested a superconducting magnet in space.
That’s where the Alpha Magnetic Spectrometer comes in. This machine was designed and built with a superconducting magnet that can operate in space.
Now Battiston and co have used the knowledge and experience from building this machine to study how it could be put to use on a deep space mission for humans. For example, they use the software developed to simulate the behaviour of the superconducting magnets on the spectrometer to study how a human-rated system might work.
This simulates not only the magnetic field but also the forces it generates and how they are distributed, an important consideration in superconducting systems.
In particular, they compare two different designs for the way wires are wound onto the magnet–one using ordinary torroidal windings and another using a double helix-type winding.
Their conclusion is that the double helix offers significant advantages because of the way the forces are distributed within it. These would require less external support, which would reduce the mass of the entire system.
That’s a potentially interesting project–the International Space Station has always been thought of as a stepping stone to the Solar System so it is appropriate that its technology could provide a foundation for future missions.
However, this isn’t the whole story. What Battiston and co fail to mention is that after 15 years of design and testing at a cost of a cool $2 billion, the superconducting magnet system allegedly could not be made reliable enough to fly in space. In the end, it had to be hastily replaced with permanent magnets just a few months before the Space Shuttle carted it into space last year.
NASA and other space agencies have always known that sending humans into space is hard and expensive. What they’ve failed to grasp is that they are having to spend more and more to do less and less.
The Alpha Magnetic Spectrometer is a case in point. The only significant science being done on the $100 billion ISS is with the spectrometer. And the only reason it is attached to the ISS is because of the power it was supposed to need for its original superconducting design: only the solar panels on the ISS could provide enough, we were told. The presence of humans is more or less irrelevant.
Maybe future systems could be made reliable enough to protect humans. They might even be made light enough to be launched into space. But it doesn’t look likely that they can be made cheap enough to be justifiable in the short to medium term.
Here’s the bottom line: humans are an expensive cargo that add little if any value when it comes to science in space.
So the message is clear–if we want the best return from our space-bound bucks, we’ll be better of sending robots for the foreseeable future. And they don’t need any kind of magnetic protection–superconducting or otherwise.
Ref: arxiv.org/abs/1209.1907: ARSSEM: Active Radiation Shield for Space Exploration Missions