It’s heart wrenching to see how world is progressing and we are still behind. Stuck in Fatwa’s and concept of Halaal..Haraam.
Here we are sharing an article published in The Economist on April 16th 2016.
SPACEX and Blue Origin, two American space companies, can now return their rockets to Earth and reuse them, which promises to reduce launch costs. But what if, instead of bringing the boosters back to Earth, you could build one that never leaves it? Your propulsion system could be arbitrarily large and powerful, since you wouldn’t have to lift it; your spacecraft, no longer needing engines or fuel, could be stripped down to its barest essentials.
Such a split sounds impractical, but beams of light could make it work. One of the counterintuitive implications of the theory of relativity is that, although light has no mass, it still has momentum. Thus when light bounces off a mirror it exerts a tiny pressure; if the light is bright enough, and the mirror light enough, the mirror will start moving.
n the 1970s Robert Forward, a physicist, showed that very powerful lasers could push a spacecraft with a reflecting “sail” to a tenth the speed of light or more. Moving thousands of times faster than rockets can, such probes might reach planets round other stars in decades, rather than in hundreds of thousands of years. But the incredible technical challenges of such a scheme meant that Forward’s ideas were never developed in any practical way.
That could be about to change. On April 12th, the 55th anniversary of Yuri Gagarin’s first flight into space, Yuri Milner, a Russian physicist and billionaire investor, announced a plan to develop the technologies such interstellar flight would need. Mr Milner—who was named after Gagarin—is devoting himself to the challenges of deep space. Last year he said he would spend $100m to bring recent advances in computing to bear on the search for extraterrestrial intelligence (SETI).
When he first looked at laser-powered interstellar travel, Mr Milner says, the idea triggered both his scepticism as a physicist and his cynicism as a businessman. But he has concluded that, as in the case of SETI, technological capacities developed for other reasons will be a boon. Given current trends in microelectronics, nanotechnology and lasers, he thinks that within a generation attempts at interstellar flight might be no more costly than today’s most ambitious scientific programmes. So he is going to spend $100m on a “Breakthrough Starshot” research programme aimed at making that dream possible.
Beam me up
The basic problem with using light to drive a spacecraft is low efficiency. A gigawatt laser beam—1GW being a billion watts, roughly the power output of a large nuclear plant—provides a bit less than seven newtons of thrust: a force equivalent to that required to lift a glass of beer. For such thimblefuls of thrust to amount to anything much, they have to be applied to a very light spacecraft indeed: ideally one with a mass not much larger than a gram.
It is a measure of the outlandishness of this endeavour that fashioning such a nanoscale spacecraft almost seems like the easy bit. Zac Manchester, a Harvard researcher involved in Mr Milner’s scheme, has already crowdfunded a project that produces satellites the size of postage stamps. In the fairly near future a camera, a decent computer, a communications laser and a tiny speck of plutonium for on-board power—all capable, like the electronics in “smart” artillery shells, of surviving extraordinary accelerations—might plausibly sit on a single silicon “starchip”.
Building a similarly low-mass sail may prove a much taller order: perfect mirrors typically weigh quite a lot. But Philip Lubin of the University of California, Santa Barbara, one of the researchers who inspired Mr Milner’s enthusiasm, says the sail only needs to reflect one wavelength of light: that of the laser. It could be transparent to all other wavelengths. That makes things simpler. With coatings engineered on an atomic scale, a layer of glass just a few tens of atoms thick might be able to do the job.
The propulsion system Mr Milner sees as the final goal would consist of perhaps 10m lasers, each delivering 10 kilowatts or so, spread over a square kilometre of otherwise empty desert. For a launch their output would be combined into a single 100GW beam focused on a sail just a few metres across up in space. If that sail and its starchip were to have a mass of just five grams, then after ten minutes of the array’s 670-newton attention the probe would be a third of the way to the orbit of Mars and travelling at a quarter of the speed of light—fast enough to get to the nearest stars in less than 20 years. After flashing by its target planets—there is no possibility of braking—it would send back data with its on-board laser. No current observatory could pick up such a signal—but the kilometre-wide launch array should be able to. The optical systems used to meld the output of the lasers could be used in reverse as a vast and sensitive telescope.
Far fetched as all this sounds, purely in terms of energy it is not that much grander than everyday space flight. Rockets deliver many gigawatts of power, but to big objects. Dr Lubin points out that a space-shuttle’s motors produced a stonking 45GW at lift-off and in a bit less than ten minutes were capable of giving their 100-tonne spacecraft a kinetic energy only a few times smaller than that of a starchip travelling at a fifth the speed of light.
Still, a dozen or more technologies will need to improve by orders of magnitude for a starshot to be feasible. Or, rather, a series of starshots: the array could be used again and again, and if starchips can be made they can surely be mass produced.
In some areas a lot of improvement is likely. Laser power is getting cheaper, as are the storage systems needed to suck up many gigawatt-hours of energy and disgorge them in minutes. Advances are also steadily being made in the sort of solar-power systems needed to supply the necessary gigawatts to the desert array and the computers needed to operate it.
Other advances will be more challenging and, being more specific to a starshot, less likely to be developed for other purposes. One such is how to protect a piece of microelectronics from impacts with specks of interstellar dust at a relative speed of 80,000km/sec. Perhaps the most daunting task is “shaping” the output of millions of lasers into a 100GW beam focused on a spot thousands of kilometres distant, all the time taking the turbulence of the atmosphere into account.
That will require subtle fine tuning of the output of millions of lasers. For comparison, the biggest telescope on the drawing board today has 798 separate mirror elements —and the challenges for telescopes focusing light from elsewhere are much less extreme than those facing arrays that emit light by the gigawatt. Those challenges may prove insurmountable.
Enthusiasts might say that the problems were similarly immense in the early days of rocketry, but less than 25 years after the first V-2 flight, men arrived on the Moon. Inspiring, perhaps; perturbing, too. Rocketry was a military discipline, from its origins in China to the modified ballistic missile that sent Gagarin on his way. And although lasers have lots of civilian uses, the military has a keen interest in them. Much of the recent progress in combining separate lasers into a single coherent beam and making them more powerful as a potential weapon can be traced to the Defence Advanced Research Projects Agency, the Pentagon’s funder of far-out tech.
A 100GW array could be quite a weapon. The energy in one of the mooted ten-minute blasts needed for a starchip is equal to that unleashed in the bombing of Hiroshima. If a mirror in orbit were used to reflect the beam back to Earth it would be impossible to defend against.
This means that just as Mr Milner’s team has a lot of technology to sort out, it faces other potentially show-stopping challenges. His project leader, Pete Worden, is a retired Air Force general with experience in space weapons and arms control as well as an astronomer. That should help. Like his boss he accepts that such powerful technologies might need to be under some sort of international control. Were such oversight possible, it might be fitting as well as prudent. If humans are to stand on the threshold of the stars, it would be nice if they could do so together.