Inflatable Telescopes and Solar Sails
Since it was put into orbit in April 1990, the Hubble Space Telescope has been the primary tool for gathering images in space. But just getting the Hubble into orbit was a major accomplishment for NASA. Hubble is 43.3 feet (13 meters) long and 14 feet (4 meters) wide, and it weighs about 25,500 pounds (11,000 kg). It would cost more that $25 million to put that type of structure into space today, and that's not counting the costs for materials to build another Hubble. Yet, to extend our view into space, scientists must be able to place an even more powerful telescope in Earth orbit.
NASA scientists are now using inflatable technology to build a telescope that is nearly twice as large as Hubble but that weighs only about one-sixth as much as Hubble. The 82-foot Advanced Radio Interferometry between Space and Earth (ARISE) will also dwarf Hubble in how far it can see into space. According to early estimates, ARISE will have a resolution 3,000 times better than Hubble. Interferometry is a process by which more than one antenna is used to construct highly detailed photos. In this case, ARISE will be used to take pictures of black holes, interstellar planets and other stars.
Despite ARISE's much larger size, it is expected to be quite easy to transport into space. The ARISE telescope's reflector, or antenna, and poles will be constructed out of an advanced thin-film polymer material that can be folded up and stuffed into a small canister, which is then placed on top of the main spacecraft. The reflector itself will be woven into a mesh netting. The canister that holds the reflector is just 1.31 feet (.4 m) tall with a diameter of 5.9 feet (1.8 m). This page shows a good illustration of how the canister is stacked on the spacecraft carrying the ARISE telescope.
The ARISE spacecraft will likely be launched into space onboard a smaller spacecraft than is available today. When the ARISE spacecraft reaches orbit, the mesh netting antenna is released, but it is not this part of ARISE that actually inflates. Instead the three poles, or booms, that connect an inflatable ring around the netting to the spacecraft will inflate. To inflate the poles and the inflatable ring, the Sun's energy is focused on a heat exchanger containing liquid hydrogen on the spacecraft. This heat allows gas to form, which then flows into the poles and ring. Once the poles are rigid, the antenna will also remain rigid. The entire inflating process will take place in just minutes.
In 1996, the Space Shuttle Endeavor deployed an experimental antenna prototype to test this new technology. This 46-foot (14 meter) prototype was successfully inflated over several hours, and generated a great deal of interest in the further development of inflatable spacecraft. NASA has said that the ARISE telescope is scheduled for launch in 2008.
The same technology being used to develop the ARISE telescope could one day be used to construct solar sails that could propel spacecraft beyond the edges of our solar system at incredible speeds. Solar sails will unfurl in space using the same process that inflates the ARISE's poles and inflatable ring. The sail is actually an ultrathin mirror made of carbon fibers that can capture the sun's energy to propel an attached spacecraft to speeds up to 200,000 mph (324,000 kph).