For space kids who grew up reading science fiction, this idea requires no explanation.  For those unfortunate readers who did not have this experience, we offer this quick summary:

The warm, gentle sunlight that we feel here on Earth is really only a tiny fraction of the sun’s full output.  Even the hottest places on Earth- say, Death Valley or the Sahara Desert- are only receiving a small percentage of the solar radiation that hits the atmosphere above them.  Luckily for us, we are protected from most of it by that thick blanket of air.  Outside of that protection, the wind from the sun is a blasting torrent, a constant tsunami of radiation and particles.

And of course, sunlight exerts a certain amount of pressure.  The pressure is very weak down here on Earth, but if you get off the Earth and move into the full blast of the solar wind, everything changes.  Suddenly you’re in the full tsunami, and the pressure exerted by it is much greater.

Consider what you’ve got here.  It’s a stream of propulsive force which, in human terms, is inexhaustible- and unlike the intermittent thrust of rockets, this is constant propulsion, which allows you to build up enormous speed over time.  In the world of space exploration, this is the Holy Grail.  It is the thing that can finally free us from that necessary evil of space flight: fuel.  The sad fact is that when you’re using conventional rockets, the fuel is the biggest part of the weight.

Now, we’ll always need a big push to get out of the atmosphere and attain orbital velocity, and chemical rockets are still the only way to get that (though other ideas have been discussed- more on this in future articles).  However, once you get into orbit and you’ve got all that sunlight,  why not use it?  Throw out a kite and ride!

That’s the definition of a lightsail: a kite that uses the solar wind to move a spacecraft.  In the old days, this was pure sci-fi, because we didn’t have any materials that were strong and light enough to do the job, but recent advances in materials science have provided lightweight plastics that are bringing the goal within reach.   Not only that, but we now have a couple of possible embellishments that build on the basic concept and use the power of light in different ways.

As mentioned above, there are actual prototypes being readied for launch this year.  The Japan Aerospace Exploration Agency, a rising power in the field of space exploration, is planning to send up a craft called IKAROS in May.  In an effort to cut costs, the craft will be launched aboard the same rocket with Japan’s Venus Climate Orbiter, the partner to the European Space Agency’s Venus Express which we discussed a few weeks ago.

IKAROS takes the idea of a lightsail a step or two further.  Here, the plastic membrane is not only used for propulsion, but also contains three other systems: a thin-film electrical power generation system, a set of steering devices and a dust-counter.  They do all this on a layer of polyimide that is only .0075 mm thick.  When fully deployed, IKAROS will be a square with a diagonal length of 20 m.  Its mission will be in two stages.  In the first stage, the sail will be deployed and used to generate electricity.  This will be the first time a lightsail has been used for this purpose, and if the mission ended right there, it would have already started a revolution in the field of space electronics.

But hopefully, IKAROS will keep on going.  The second phase of its mission is to actually use solar power to navigate the craft.   The destination of IKAROS is uncertain, but it will be steered toward Venus.  As mentioned above, it will be sent into orbit on the same rocket with the Venus Climate Orbiter, and hopefully both craft will eventually arrive at that planet.

IKAROS is the first of two proposed Japanese missions.  The second one will take place in the late 2010′s, and will consist of a hybrid craft which combines all of the technology of IKAROS with an ion propulsion system.

The ion drive uses electricity generated by solar power to excite xenon fuel.  The excited fuel is focused into a jet by passing it between two powerful magnetic fields, and leaves the engine at high velocity.  The advantage of an ion engine is that the xenon fuel is capable of delivering a large amount of thrust in proportion to its weight, which means that a spacecraft can carry enough fuel to keep going for years.

When you combine this system with the lightsail idea, you get a hybrid craft that can use both systems to maximum advantage.   For instance, such a craft might use its lightsail while it’s near the sun, riding the solar wind and storing up electricity.  Later, when it gets farther out where the sunlight is weaker, it might fold up its sail and use the stored electricity to run the ion drive.

Here in the US, the Planetary Society is making its second attempt at testing a lightsail.  Their first one, Cosmos I, was tragically lost when its launch rocket crashed, but now the Society has embarked on an ambitious project to deploy three sails over the next few years.   While the Japanese project is focused on broad technologies that will be used for multiple projects in the future, the Planetary Society is focusing more on practical and specific jobs, such as monitoring the sun for solar storms and providing stable Earth observation platforms.

Their first sail, Lightsail I, will be launched this year and will demonstrate the deployment of the sail and its use for propulsion.  The second sail will do the same, but will move to a much higher Earth orbit.  The third sail in the Planetary Society’s program will leave Earth orbit and navigate to the Earth-Sun libration point, L1.  This will be an ideal location for weather-sensing satellites and other devices, which in the future will hopefully be propelled into their positions by lightsails.

The Planetary Society’s ambitions are set on greater goals someday.  Louis Friedman, the Society’s executive director, recently posted an article on their website about the glowing possibilities offered by this line of research.  One possibility that he brought up is the idea of using a lightsail with an Earth-based laser for propulsion instead of sunlight.  With something like that, you could send a beam of coherent light at another star and ride it all the way there.  When you arrived, you could set up another laser and point it back at Earth, then ride the beam back home.  Whereas the basic solar sail idea only allows travel within the solar system, the laser idea could give us access to the stars.

It’s a long way off, but someday it could happen.  In the meantime, we need to do the basic groundwork, and that’s what’s about to happen.  Both the JAXA craft and Lightsail 1 will go up this year, and the results of those projects will show the way to the future.

In 1964, Arthur C. Clarke wrote a short story called “The Sunjammer,” which was about a race between solar-propelled spacecraft.  It was published in a popular boys’ magazine, and was read by a whole generation of kids in love with space.  Some of those kids are probably working on these projects today- and some of them are also reading and writing about them.

Stick with us, and you won’t miss a thing.

Sources:
Satellites and Spacecraft: Small Solar Power Sail Demonstrator “IKAROS” at JAXA website:  jaxa.jp/projects/sat/ikaros/index_e.html

IKAROS Project page at JAXA website: jspec.jaxa.jp/e/activity/ikaros.html

Let’s Set Sail for the Solar System by a Solar Yacht!  at JSPEC website: jspec.jaxa.jp/ikaros_cam/e/03.html

Lightsail- the Future of Solar Sailing at the Planetary Society website:  planetary.org/programs/projects/solar_sailing/

Friedman, Louis D.: Lightsail: A New Way and a New Chance to Fly on Light at the Planetary Society website:  planetary.org/programs/projects/solar_sailing/tpr_lightsail.html

The SDO mission is the first in NASA’s scientific program called Living With a Star (LWS). This program is being put in place to further our knowledge of solar variability and the impacts that this has on our planet. The SDO mission itself was designed with the aim of studying the solar atmosphere in an attempt to understand its influence on Earth and near-Earth space.

The planning and development of the project is being undertaken by NASA’s Goddard Space Flight Centre and they will also be responsible for managing the operational phase of the mission once its gets underway. Important milestones in recent months have included moving the instrument to Kennedy Space Centre where it is undergoing final testing to ensure it can withstand the rigors of being launched into space and also the conditions it will face during its life orbiting the Earth. A launch date is expected in early 2010 with the mission planned to run for an initial 5 year period.

The aim of the SDO mission is to study how the magnetic field of the Sun is generated and converted into solar activity which comprises solar flares, solar wind and coronal mass ejections. Solar flares and coronal mass ejections can discharge millions of tons of charged particles and solar material into interplanetary space at millions of miles per hour and this can stream towards Earth on the solar wind. This is generally known as space weather and can be potentially dangerous to astronauts in outer space as well as posing problems for technology on and around Earth including satellite communications, electricity supply and navigation systems.

The observatory will be put into an orbit where it can monitor the Sun continuously during its 5 year mission and the three scientific instruments on board will be capable of taking a range of measurements. These instruments will work simultaneously and they include the Extreme Ultraviolet Variability Experiment (EVE) which will measure the Sun’s ultraviolet brightness as often as every ten seconds to record changes in this. The Helioseismic and Magnetic Imager (HMI) will measure sound waves bouncing around the interior of the Sun and also the strength and direction of magnetic fields on its surface which should allow a picture of the Sun’s interior to be built up. The Atmospheric Imaging Assembly (AIA) will take pictures of the various layers in the Sun’s atmosphere in an effort to understand how changing magnetic fields release the energy which leads to solar flares and coronal mass ejections.

Together the suite of instruments on SDO will result in observations that should help scientists gain a much fuller understanding of the complex solar dynamics which impact on Earth and the near-Earth environment. Ultimately this should lead to the development of a capability for assessing and predicting solar variations and this should help to provide an early warning to any potential problems heading our way as a result of solar activity. 2010 should be an exciting year in the continued study of the Sun and with the recent success of the Sunrise Telescope and the operational capabilities of the Solar Dynamics Observatory our knowledge of the Sun could take a giant leap forward in the near future.

The Sunrise telescope is a collaborative project between the Max Planck Institute for Solar System Research (MPS) and a number of partners based in the USA, Spain, Sweden and Germany.  These partners include research facilities such as NASA’s Columbia Scientific Ballooning Facility, the ESRANGE Space Centre in Sweden and the High Altitude Observatory in Colorado. The aim of the mission was to launch a telescope into space which could provide high-resolution images of the Sun’s surface which would assist in studying the magnetic field in the solar atmosphere.

The main instrument for the mission was built by Kayser-Threde under MPS supervision and this comprises a light weight solar telescope of 1m aperture. Other instrumentation includes a spectrograph and magnetograph and with its array of technological features it was expected that the telescope would provide observations of the Sun’s surface which could detect features as small as 30km in diameter. On completion of the telescope a successful test launch was achieved in 2007 and this was followed with the telescope being launched into space from the ESRANGE Space Centre in northern Sweden. The launch date was in June 2009 and a giant helium balloon carried the telescope to an altitude of 37 kilometers above the Earth for a six day period.

While viewing the Sun is possible from the ground, turbulence in the lower atmosphere tends to cause image distortion and by launching the telescope into the stratosphere it was considered that more accurate images could be achieved. At this height the telescope can also view the Sun in ultraviolet light which is not possible on the ground as the ozone layer absorbs this type of light. This was of particular interest to the mission team as variations in solar radiation show up more clearly in ultraviolet light. The telescope was kept aligned for observations by an innovative control system which kept it focused on the Sun during its flight and on completion it detached from the balloon and parachuted safely back to Earth.

While the flight itself took place in June, the results have only started to be released in November and these have shown that the telescope has been a spectacular success. It has provided some stunning images of the surface of the Sun to a level of detail which has never been achieved previously. These show details of the complex interplay that exists on the surface of the Sun and also excellent close ups of the grainy surface structure itself which is known as granulation.

The first views of the results have demonstrated that the telescope is capable of providing information which should help scientists greatly increase our understanding of the Sun and its activity. A total of 1.8 terabytes of data was collected and analysis of this is ongoing. Hopefully as further results are released they will provide ever more impressive details to enhance the study of the Sun and provide a leap forward in our knowledge.

Further flights of the telescope are planned and this will place the Sunrise project at the forefront of solar study. If future flights are as successful as the first then we can expect our understanding of the Sun to move forward in the coming years.

Check out the launch of the Sunrise Telescope below: