Two simulated pictures of a distant galaxy. Left, the resolution Hubble could achieve. Right, the HDST. Source: AURA. The James Webb Space Telescope (JWST) will be the largest and most powerful space telescope ever produced, an incredible addition to humanity's search of the stars - when it's launched in 2018. It's saddled with incredibly high expectations, due mostly to its role as the anointed successor to NASA's super-successful Hubble space telescope. Yet even before the JWST has been assembled, space scientists are looking forward, dissatisfied in advance with the limitations posed by a mirror that is only two and a half times as wide as Hubble's. Their solution? The High Definition Space Telescope (HDST), which is proposed to launch in the 2030's with a mirror almost twice as large as the JWST's. Of course, when it comes to space telescopes, size isn't everything. The Association of Universities for Research in Astronomy (AURA) report that proposes the HDST notes that when Hubble goes dark just a few short years from now, humanity will be left with no powerful tool for looking at the universe in certain wavelengths. JWST will look primarily in the infra-red portion of the EM spectrum, while Hubble incorporates more long-wavelength visible and near-IR light, allowing different sorts of investigations. A true Hubble successor, one that could pick up and continue its historical quests with updated technology, would require a whole different launch. JWST is Hubble's successor mostly because it will be the largest and most famous piece of space technology. So, while the increase in resolution allowed by the HDST's increased size would certainly be helpful, it's the ability to take different sorts of readings that could motivate science organizations to pool their money and fund this enormous venture. AURA projects that costs could rise to $10 billion or above, but the JWST itself has cost something like $8 billion, so with decades in which to fundraise that might not end up being such a lofty goal. Despite the incredible proposed size and the level of sophistication in its imaging equipment, AURA believes that each of HDST's component projects are individually quite doable. Its main mirror, which is proposed to be nearly 40 feet in diameter, has the same unfolding, segmented design as that of JWST itself - though with more and larger segments than current technology allows. The report actually only stopped at the size it did due to limitations in cargo space available on the heavy launch vehicles most likely to dominate at the time of launch. And since its components can operate at high temperatures, it will have non of the JWST's problems with maintaining cryogenic conditions, which has been one major source of delay and increased cost. Kepler has already discovered thousands of alien worlds. What might the HDST discover about them? Despite the Hubble-buzz that surrounds the HDST, AURA says that one of the main motivations to build it is actually to continue the mission of the Kepler space telescope - NASA's tailored hunter of exoplanets, which has identified and examined thousands of worlds orbiting stars other than our own. Astronomers are doing what they can to study these alien planets, but current technology is pushed near its limit just proving they exist at all. The HDST would allow them to start taking detailed readings of alien atmospheres, allowing not just detailed study of exoplanets, but a wide-ranging search for planets with signs of alien life. If it is ever built, the HDST will quickly become the favorite toy of a large portion of the world's astronomers. AURA wants to get a wide swathe of the community onboard with helping to lobby governments to fund the project, which will likely be a tough sell in the wake of JWST's own super-expensive launch. They hope that by making the telescope useful to as many astronomers as possible, they can pool enough funding to launch in 20 years or less. http://www.extremetech.com/extreme/209493-astronom...