Space Sunday: taking an elevator into space

An artist’s concept of a “carrier” – the “elevator car” of a space elevator – climbing the elevator cable. Credit: unknown

The space elevator is perhaps one of the most intriguing ideas for reaching space. It was first conceived as a thought experiment in 1895 by the grandfather of astronautics, Konstantin Tsiolkovsky. In it, he considered the building of a massive tower reaching up to geostationary orbit at 35,756 km (23,000 mi) above the surface of the Earth, and which at the top would have sufficient horizontal velocity to launch vehicles into orbit. The vehicles themselves would be carried aloft by elevators like the ones climbing the Eiffel Tower.

Tsoilkovsky knew the construction of such a tower would be next to impossible, there simply were no materials capable of withstanding the compressional pressures exerted the mass of such a tower as it was built upwards – nor are there today. However, in 1960, another Russian,  Yuri N. Artsutanov suggested that rather than building the elevator up from the ground, it could be built both down and out from geostationary orbit, using tension along the cable from its lower end and through the “counterweight” of the outward extent of its length to maintain is tautness and balance. Referring to the design as a “heavenly funicular”, Artsutanov estimated it would be capable of delivering up to 12,000 tonnes of payload to geostationary orbit per day.

An artist’s impression of a solar-powered car ascending the “Sky Hook”. Credit: unknown

Six years later, working entirely independently of Artsutanov, four American oceanographers – John Isaacs, Hugh Bradner, George Bachus and Allyn Vine (after whom the deep-ocean research submersible Alvin was named) – published their idea for a “sky hook” that essentially used the same approach: build a cable both “down” and “out” from a geostationary starting point. Their idea became the inspiration for Arthur C. Clarke’s 1979 novel The Fountains of Paradise, which did much to promote the idea of space elevators in the public mind.

Since then, the idea has received many re-visits, and has also given birth to a number of experiments and ideas for the use of tensile cables  – referred to as “tethers” for doing things like “lowering” experiments into the upper atmosphere for research (such ideas being tested during the space shuttle era) and for creating “artificial gravity” in spinning space vehicles travelling to Mars. A space elevator even appeared in Kim Stanley Robinson’s Mars trilogy as the means to get from orbit down to the surface of the planet. Today, the space elevator is the subject of study by the International Space Elevator Consortium (ISEC), which holds annual conferences on the subject and supports research programmes into space elevator concepts.

The appeal of space elevators  – if they can be built – is that they could deliver huge amounts of payload and manpower to orbit around Earth for a relatively low-cost when compared to using traditional rocket launches. And deliver them not just to geostationary orbit, but to other points above the surface of Earth, referred to as “way stations”.

For example, a “way-station” at around 420-450 km (262-281 mi) altitude would impart a horizontal velocity for vehicles “launched” from it to keep them in a low Earth orbit. similarly, a way station placed above the geostationary orbit point, at say 57,000 km (36,625 mi) would impart enough horizontal velocity to a vehicle “launched” from it that it could escape Earth on a flight to Mars.

The space elevator concept, show an ocean anchor point, and the various “way stations” along its length, capable of supporting operations a low Earth orbit (LEO), geostationary orbit (GEO) and high earth orbit (HEO) altitudes, the latter of which could support missions to Mars and further out into the solar system. Credit: ISEC

But before this can happen, there are some significant issues to overcome. The “simplest” of these is that of finding a suitable anchor point on Earth.

To work at geostationary orbit, the primary station on an elevator would have to be positioned over the equator. The problem here is, an awful lot of the equator is ocean (78.7%), making the construction of such an anchor-point at best difficult. While the remainder of the equatorial region is over land, it brings with it the overheads of political haggling and leveraging to gain an anchor-point.

In The Fountains of Paradise, Arthur C. Clarke solved this problem by conveniently moving Sri Lanka (which he called by its ancient Greek name of Taprobane (Tap-ro-ban-EE) 1,000 km (625 mi) south of its current position to straddle the equator. Unfortunately, we can’t do that in the physical world.

The more significant issues, however, are exactly how to build the elevator tether and how to gradually and safely lower it through the denser part of Earth’s atmosphere, and without its “downward” mass simply ripping it apart before it can be anchored.

The most promising material for the tether construction is carbon nanotubes (CNTs). These are artificially “grown” structures with a number of unusual properties, one of which it their sheer strength: up to 10 times that of an equivalent steel cable, which comes at a fraction of a cable’s mass. CNTs have been known about for around 20 years and are seen as having a range of potential applications: construction, electronics, optics, nanotechnology, etc. However, there is one slight issue with their use in large-scale projects. So far, no-one has successfully “grown” a nanotube longer than 1.5 metres.

Even so, experimental cables have been lifted to altitudes of around 1 km (0.6 mi) using weather balloons and had scale “carriers” run up and down them to test how an elevator tether and its payload would react to the influence of wind and weather. Now, researchers at the Shizuoka University Faculty of Engineering are taking the practical research a step further, by deploying an experimental “space elevator” in space.

On Monday, September 7th, 2018, the  Kounotori-7 H-II Transfer Vehicle (HTV) resupply vehicle is due to be launched to the International Space Station (ISS). As a part of the six tonnes of supplies the vehicle will be carrying will be two small “cubesats” – satellites that are each just 10 cm (4 inches) on a side.

Computer model of the cubesats and their (not to scale) tether deployed in Earth orbit. Credit: Shizuoka University

These will be deployed in space, connected by a 10 metre (33 ft) tether. Once the tether is under stable tension, a little electrically powered “car” will traverse it, marking the first time a vehicle has travelled along a tether in space. The test is intended to see how a space elevator tether might react to payloads moving along it in whilst in the “vacuum” of space, together with the stresses placed on it and its “anchor points”, etc.

It’s a small step along the way to establishing a space elevator, but the test will be watched with interest by Japan’s massive construction firm, Obayashi Corporation. In 2012, they announced they would have the world’s first space elevator operating by 2050. They are actively sponsoring research into CNT development, and believe the issues of growing long strands of CNTs and “knitting” them together into a tether will have been resolved by 2030.

Obaysahi Corporation’s design for their GEO station on the space elevator, which the company says will use “inflatable” modules to reduce mass. Credit: Obayashi Corp.

Once built, Obayashi plan to have “carriers” travelling at 192km/h (120mph) along it to lift payloads of 100 tonnes or 30 people with life support systems into space at a time. The “way stations” mentioned above would be included, supporting satellite and deep-space missions, while the geostationary station would be used to construct and deploy solar power satellites and provide research facilities. Obayashi have even determined the cost of the elevator’s construction: 1 trillion yen (US $90 billion) – which is roughly one-fifth of the cost of the Chūō Shinkansen maglev train project being constructed between Tokyo and Nagoya.

Whether Obayashi can achieve their goal or not is highly debatable. Certainly, the time frame would at best appear ambitious, given the overall state of the required technologies. There’s also the none-to-small issue of establishing and maintaining a human presence at geostationary orbit. This would likely be required in order to supervise construction activities and ensure there is an equipment repair capability. However, Obayashi is not alone in announcing plans to establish a space elevator. In 2017, the China Academy of Launch Vehicle Technology indicated it plans to be operating a space elevator by 2045.

In the meantime, the Shizuoka University experiment, which will include cameras to film what happens, should prove interesting, if successful.

Catch a Comet

Comet 21P/Giacobini-Zinner, aka “21P”, a short-period comet, will make its closest approach to Earth on Monday, September 10th, 2018, as it makes its way around the Sun in its variable 6.4 to 6.6 year orbit.  For those in the northern hemisphere, it will be visible though binoculars or modest telescopes as a bright green object in the eastern sky, “in” the constellation of Auriga, below and to the right of Auriga’s brightest star, Capella.

Where to find Comet 21P/Giacobini-Zinner: look to the east and locate Capella in the constellation of Auriga, relatively high above the horizon, then trace a diagonal line down and to the right from it to bright orange Betelgeuse in Orion’s shoulder. 21P will appear as a green object visible through binoculars about 1/3 of the way along the line and a little below it.

The comet will officially reach perihelion, or its closest point to the Sun, around  06:40 GMT (2:40 a.m. EDT; 07:40 BST), but will be visible in the sky for the next several nights for those with binoculars or telescopes- contrary to the headlines found in some tabloids, it will hardly “light up the skies”. Its orbit carries it between the Sun and the orbit of Jupiter, with the latter exerting enough gravitational influence on the comet to cause the variations in its orbital period.

21P is responsible for the Draconid meteor shower, which occurs every October as the Earth crosses the comet’s orbit. It is the result of dust given off by the 2 km (1.2 mi) diameter comet as it is heated by the Sun, burning up into the Earth’s upper atmosphere and burn up. Normally a low-key meteor shower, the Draconids might be a little more noticeable this year due to the comet’s recent passage.

At the time of perihelion, Giacobini-Zinner will be some 58.5 million km (36.3 million mi) from Earth. Depending on its relative position with that of Earth each time it swings around the Sun, it can come as close as 5.2 million km (3.3 million mi), although such close passes are rare. In fact, this year marks the closest the comet has come to Earth since 1959.

True-colour image of Comet 21P/Giacobini-Zinner, photographed by Alexander Vasenin. Capella can be seen in the top left corner, Betelgeuse to the right of centre at the bottom. Credit: A Vasenin, provided under a Creative Commons license.

Watching a Rocket Launch From Space

The OS-X1 being prepared for its September 7th launch. Credit: Chinanews.com

China’s first private launch company, OneSpace Technology (Líng Yī Kōngjiān Kējì, or “Zero One Space Technology”) completed its second successful sub-orbital launch on Friday, September 7th – and it was a launch caught from an unusual angle.

Called the Chongqing Liangjiang Star, the OS-X rocket is 9 metres (33 ft) in length and once operational, is intended to reach altitudes of up to 100 km (60 mi), allowing customers to test technologies and fly research experiments into suborbital space.

The first OS-X flight took place in May 2018, reaching an altitude of 40 km (25 mi) in May 2018. The September 7th launch took place from the Jiuquan Satellite Launch Centre in Gansu Province, north-west China, with the rocket and a small unspecified payload reaching a maximum altitude of 35 km (21.7 mi)  and a maximum velocity of Mach 4.5.

OneSpace Technology has been compared to SpaceX in its nature. The organisation was initially established in 2015 using funding from the  State Administration for Science, Technology and Industry for National Defence, but operates as a private venture organisation. The rockets it is developing – which will include both sub-orbital and orbital launchers – are designed and built entirely in-house.

The unusual aspect of the launch is that as well as being filmed from the ground, it was captured from space. The launch had been timed to coincide with an overflight by China’s Jilin-1 Earth observation satellite.  Launched in 2015,this operates in a 535 KM (332 mi) circular orbit above the Earth, and is China’s first high-resolution imaging satellite. The video it captured of the launch was released on China’s Weibo social media website prior to also being shared on Twitter and You Tube. SciNews combined the orbital footage with video taken from the ground of the launch to provide a composite film of the event.

As well as offering both sub-orbital and orbital commercial payload opportunities, OneSpace eventually plan to offer crewed flights to orbit.

Kepler Resumes Operations

At the end of August, I noted that the Kepler Space Telescope may be finally nearing the end of its operational life due to declining fuel reserves. These reserves have been under steady use for the last four years, after the telescope suffered failures in two out of four of the reaction wheels used to hold the telescope steady during observations.

The observatory had been due to start its 19th 80-day observational campaign on August 6th, 2018. However, on August 24th, 2018, it was confirmed the observatory had placed itself back in a “sleep” mode, presumably due to the low fuel situation.

For the first four years of its primary mission, the space telescope observed a set star field located in the constellation Cygnus Since 2014, Kepler has been collecting data on its second mission, observing fields on the plane of the ecliptic of our galaxy. Credit: NASA / Wendy Stenzel

However, on September 5th, NASA confirmed the sleep mode had actually been triggered by a fault in one of Kepler’s eight manoeuvring thrusters  – the motors that use its fuel reserves which orienting and holding itself steady. That motor has now been effectively shut down, allowing Kepler to come out of “safe” mode and resume operations.

On the plus side, this means Kepler is once again making observations. On the minus side, the loss of the motor leaves Kepler more susceptible to solar pressure, requiring more frequent use of the remaining thrusters to hold it steady, using more fuel in the process.

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2 thoughts on “Space Sunday: taking an elevator into space

  1. When I read Clarke’s novel, like, 30 years ago I’ve found it a plonker without much of literature value. But the idea of space elevators was a good one.

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    1. Sir ACC’s plots can be plodding (and I speak as one who grew up reading his books – blame my father!). However, The Fountains of Paradise was responsible for first awakening my curiosity about Sri Lanka, which in turn led to spending a good deal of time visiting the island over the course of several years (and in fact having several visits to Sir Arthur’s home for what he jokingly referred to as “tiffin” but was usually tea / coffee and cake!). So that book has a special place on the bookshelf!

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