Unbelievable however true facts, concerning NASA’s James Webb SpaceTelescope

On Dec twenty-five, 2021, ejection associate degree unforeseen complication, the James Webb Space Telescope can launch from the French Co-operative Republic of Guyana. whereas astronomers hold their collective breaths, awaiting each necessary step to travel right before science operations begin, we all will jointly appreciate what a marvel the telescope really is. Here square measure ten facts — physical object to some, the tip results of a career of labor for others — for everybody to fancy.

The most delayed telescope in history is on the brink of expertise not just an instant of truth, but a series of them over the approaching few months. First, the telescope should survive its Dec twenty-five launch, which should purpose it exactly on target to the L2 Lagrange purpose. Then, it should with success break away from the launch vehicle and so deploy its star panels rapidly. After that, the tower assembly, the sun shield, and also the primary and secondary mirrors should all with success deploy steps involving many single-point-of-failure mechanisms. A series of thruster firings should conjointly manifest itself, eventually resulting in Webb inbound at its destination: in orbit around the L2 Lagrange point.

If — and given that — all of those steps succeed, then NASA’s James Webb Space Telescope can begin taking knowledge as ne’er before, exploring the Universe with unexampled power associate degreed an unmatched series of instruments and capabilities. There square measure a series of discoveries we’re much certain to build once science operations begin, in addition, because the potential for locating no matter resides out there amidst the large ocean of the unknown cosmos.

And yet, despite all of that, it’s conjointly value appreciating a number of the superb and novel engineering that’s gone into the planning and execution of this telescope. while not any bustle, here square measure ten unbelievable and hard-to-believe facts concerning NASA’s latest and greatest observatory: the James Webb Space Telescope.

1.) The James Webb Space Telescope is truly lighter than its precursor, the Edwin Hubble Space Telescope. This one may be a real shocker to the majority. underneath most circumstances, if you would like to make an even bigger version of one thing, it’s attending to be heavier and additional large. For comparison:

Hubble was two.4 meters in diameter, with a solid primary mirror, and a collection space of four.0 sq. meters.

James Webb is half a dozen 5 meters in diameter, created out of eighteen totally different mirror segments, with a collection space of twenty-five. 37 sq. meters.

And yet, if we tend to were to place them each on a scale here on Earth, we’d realize that Webb incorporates a mass of ~6,500 kg, or weight of fourteen,300 pounds. once Edwin Hubble was launched, for comparison, it had a mass of ~11,100 kilos and a weight of twenty-four,500 pounds; with its upgraded instruments, it currently incorporates a mass of ~12,200 kilos and weight of twenty-seven,000 pounds. this is often an amazing effort of engineering, as each part on James Webb, wherever applicable, is lighter than its Edwin Hubble analog.

2.) James Webb’s mirrors square measure the lightest giant telescope mirrors of incomparable. every of the eighteen primary mirror segments, once it’s 1st factory-made, is within the form of an arced disk, and possesses a mass of 250 kilos (551 pounds). By the time they’re completed, however, that mass has been reduced to a mere twenty-one kilo (44 pounds), or a ninety-two reduction in weight.

The manner this is often accomplished is fascinating. First, the mirrors square measure remove their {hexagonal|hexangular|polygon|polygonal form} shape, which offers a small reduction in mass. then again — and here’s wherever it gets good — much all of the mass on the “backside” of the mirror is machined away. What remains has been tested to make sure that it will:

retain its precise form even underneath the stresses of launch not break underneath vibrations and tension, despite its brittle nature survive the expected variety and speed of meteorite impacts be sensitive to the required changes in a form which will be adjusted by the actuators connected to the rear. All in all, these eighteen mirrors can kind one mirror-like plane to associate degree accuracy of eighteen to twenty nanometers: the simplest of incomparable, all with the lightest such mirrors ever factory-made. 

Though they seem gold, James Webb’s mirrors are literally created out of Be. Yes, there’s a gold coating applied to every one of the mirrors, however, it might be ruinous to manufacture the mirrors entirely out of gold. No, not owing to the terribly high density, nor owing to gold’s plasticity, each of that square measure properties it positively possesses. the massive drawback would be thermal growth.

Even at terribly low temperatures, gold expands and contracts considerably with tiny temperature changes, which may be a dealbreaker for the fabric of alternative for Webb’s mirrors. However, Be shines on this front. By cooling down Be to refrigerant temperatures and sprucing it there, you make sure that there’ll be room-temperature imperfections, however, those imperfections can disappear once those mirrors square measure cooled once more to operative temperatures.

Only once the Be is factory-made and machined to its final form is the gold coating then applied.

The whole quantity of gold within the James Webb SpaceTelescope’s mirrors is merely forty-eight grams: but two ounces. all of James Webb’s eighteen mirrors must be outstanding at reflecting the kind of sunshine it’s designed to observe: infrared radiation. the number of gold applied must be simply right; apply deficiently and you won’t cowl the mirror entirely, however, apply an excessive amount of and you’ll begin to expertise growth, contraction, and deformation once the modification of temperature.

The process by which the gold coating is applied is thought of as vacuum vapor deposition. By putting the “blank” mirrors within a chamber, wherever all the air is exhausted, you then inject a tiny low quantity of gold vapor within. Areas that don’t have to be compelled to be coated, just like the back facet of the mirror, square measure cloaked off, so solely the graceful, polished surface finally ends up coated with gold. This method continues till the gold reaches the required thickness of solely ~100 nanometers, or concerning ~600 gold atoms thick.

All told, there’s solely forty-eight grams of gold within the James Webb SpaceTelescope’s mirrors, whereas the uninteresting backsides get struts, actuators, and flexors connected to them.