Category: Space Sunday

On Thursday, October 11th, 2018, the Soyuz MS-10 spacecraft carrying two crew – American astronaut Nick Hague and Russian cosmonaut Alexey Ovchinin to the International Space Station (ISS) suffered a core second stage failure, triggering an emergency launch abort. Both Hague and Ovchinin survived the ordeal – although the way some of the media were reporting things, one might have thought they were hoping otherwise.

Soyuz utilises a R7 booster family of launch vehicle. This comprises a single-engined core element (confusingly called the 2nd stage, surrounded by 4 liquid-fuelled strap-on boosters referred to as the first stage. Each of these also has a single motor with, like the core stage, four combustion chambers. At launch, all five elements are fired, with the four strap-on boosters running for around 2 minutes. Then, with their fuel expended, they are jettisoned.

It is at this point – 2 minutes into the vehicle’s ascent from the Baikonaur Cosmodrome, Kazakhstan, that things went awry,  and gave observers watching from the ground the first indication of trouble – telemetry being relaid to mission control in Star City, near Moscow give little indication of a problem, causing commentators there to keep to their prepared scripts even as the drama unfolded.

Due to the way they fall clear of the core stage, the four strap-on boosters perform a controlled tumble with their exhaust plumes still visible. Seen from the ground, this forms distinctive and almost symmetrical pattern around the core stage called the “Korolev Cross” in honour of the father of modern Soviet / Russian space flight, Sergei Korolev, who also designed the original R7 rockets.

On this occasion, however, following separation, a decidedly asymmetrical Korolev Cross briefly formed, before the sky around the rocket became spotted with debris as if something had broken up.  At the same time, video of the cabin in the Soyuz vehicle’s decent module, where the crew sit during both ascent to orbit and their return to earth, showed Ovchinin  and Hague suddenly experiencing a brief period of weightlessness, almost as if thrust from the vehicle’s second stage had ceased, before they were pushed back into their seats and the plush toy suspended in front of the camera (used as a very rough-and ready G-force indicator) suggested a rapid acceleration.

This sudden acceleration was the result of the launch escape system kicking-in, separating the payload shroud containing the upper two modules of the Soyuz from the failing rocket. The manoeuvre recorded a 6.7 G acceleration right when the crew would have been expecting a 1.5G climb up to orbit as a result of jettisoning the spent strap-on boosters.

Once clear of the rocket, the fairing deployed a set of aerodynamic breaking flaps, slowing it to allow the Soyuz descent module to detach. The normal parachute and retro rockets where then used to bring the capsule back to Earth and execute a safe landing.

Precisely what caused the failure has yet to be determined. As well as recovering the two crew safely and returning them to Baikonour unharmed, teams have also been busy recovering parts of the failure rocket, and Roscosmos believe they’ll be in a position to use the parts so far recovered together with telemetry from the vehicle’s ascent to provide a preliminary report on the failure within a week.

In the meantime, space experts have been examining video footage of the launch, and it would appear some form of malfunction during the separation of one of the four strap-on boosters may have caused it to actually collide with the core rocket. In his analysis of the flight, Scott Manley points to both the asymmetrical pattern of debris from the booster separation and what appears to be a radical slewing in the exhaust plume of the core stage as evidence there was some form of collision.

Some confusion also exists over what actually happened during the abort sequence. Like Apollo crewed rockets, Soyuz has a tower-like escape system at its top. In an emergency, rockets mounted in the tower fire, pulling the crew module clear with a brief acceleration of about 14 G. As the reported acceleration with MS-10 was less than this, there was speculation the escape system hadn’t been used.

However, the Russian escape system, called the Sistema Avariynogo Spaseniya (SAS), unlike American systems, has two sets of motors: those in the tower, and a set of lower-thrust motors mounted directly on the payload fairing, and capable of around 7 G acceleration – the reported speed of the Soyuz on separation. It’s theorised it was these motors that pulled the Soyuz clear, the vehicle not having reached a velocity warranting the use of the tower rockets in order to pull the Soyuz clear.

Continue reading “Space Sunday: of Soyuz aborts and telescopes” →

A pair of Columbia University astronomers using NASA’s Hubble Space Telescope and Kepler Space Telescope have assembled compelling evidence for the existence of a Neptune-size moon orbiting a gas-giant planet 8,000 light-years away. If their findings are correct, it will be the first moon found orbiting a planet beyond our solar system.

The planet, Kepler 1625b, is between 5.9 and 11.67 times the size of Jupiter. It orbits a G-class main sequence star with around 8% more mass than our own in the constellation of Cygnus, every 287.4 days. The planet has been known about for some time, but whilst re-examining the data gathered by the Kepler space observatory that led to its discovery, Alex Teachey and David Kipping from the University of Columbia noticed anomalies in the way the planet dimmed the star’s light as it transited between the star and Kepler – anomalies that in ordinary circumstances should not have been there, but which were enough to get the astronomers 40 hours observing time using the Hubble Space Telescope.

Able to study the star with four times greater precision than Kepler, HST was used to observe Kepler 1625 both before and during one of the planet’s 19.5 hour transits across the star. In doing so, it recorded not only the anticipated dip in the star’s brightness, but also a second dimming along the same orbital path, starting some 3.5 hours after the first had started. The Hubble data also revealed that Kepler 1625b started its transit across the star 1.25 hours earlier than it should have.

When put together, the most likely explanation for both the “premature” transit and the extra dimming of light from Kepler 1625 is that a vary large, somewhat distance moon is orbiting the Jupiter-like Kepler 1625b. The presence of such a body in orbit would set a common barycentre (centre of gravity) between the planet and the moon that would cause the planet to “wobble” from its predicted location in its orbit, leading to variations in the start times for transits. Similarly, the presence of a large moon orbiting it would cause the additional dimming in the star’s brightness during a transit.

Before the exomoon’s existence can be confirmed, further observations by Hubble are required. However, the preliminary data gathered suggests it could be around 1.5 percent the mass of its parent star – which is a very close mass-ratio between the Earth and its moon. However, given both the massive planet and its moon appear to both be gaseous in nature, should the moon’s existence be confirmed, it raises intriguing questions as to how it was formed.

In the case of solid satellites like the Moon, their creation is likely due to a collision between Earth and another planetary body that left debris that coalesced into the Moon. Such a path of formation for a gaseous body, however, is exceptionally unlikely: anything impacting with Kepler 1625b, for example, would likely be absorbed into it, rather than throwing off matter to form a separate orbiting body.

One of the most intriguing theories for the moon’s possible existence is that it may have started life as a separate planet orbiting Kepler 1625, but over time it came under the gravitational influence of the massive Kepler 1625b, and over time was drawn into orbit around it. If this should prove to be the case, it could have interesting implications for future exoplanets and the moons that may be found orbiting them.

NASA Delays Commercial Crew Launches and Tensions with Russia Increase

NASA has confirmed that the first uncrewed test flights of the SpaceX Crew Dragon and Boeing CST 100 Starliner commercial crew transports intended to fly astronauts to the International Space Station (ISS) have been delayed.

Under the original schedule, the uncrewed flight test for Crew Dragon had been scheduled for November 2018 and would have been followed by a 2-week crewed flight with NASA astronauts Bob Behnken and Doug Hurley in April 2019.  Under the new schedule, these flights will now  occur in January and June 2019 respectively.

Similarly, the first uncrewed flight for the CST-100 Starliner is now planned for March 2019 with the crewed test previously scheduled for mid-2019 now set for August 2019.

If SpaceX and Boeing maintain the new schedule, NASA believe the first operational commercial crew mission could take place in August 2019 – which would suggest a Crew Dragon would be the vehicle used, given the CST-100 would just have completed its crewed test flight, requiring some post-mission analysis. The second operational will then follow in December 2019. Both of these dates straddle the end to the US government’s extended contract to use seats on Russia’s Soyuz vehicle to send US astronauts to and from the ISS.

While unrelated, the news of the delays came as US / Russia tensions concerning the hole found in a Soyuz capsule became strained once more.

As I’ve previously noted (see here and here), at the end of August a slow leak was detected in a Soyuz MS-08 docked at the ISS. Initially, it was thought the hole causing the leak was the result of debris puncturing the Soyuz hull. However, it emerged the hole appears to have been drilled. Core thinking around it was that a mistake had been made during the vehicle’s fabrication or in preparing it for flight at the Baikonur cosmodrome, and then hastily covered up. In either case, it is believed a substance unfit for purpose was used in the repair, which gradually degraded in space prior to failing completely, causing the pressure loss.

Continue reading “Space Sunday: exomoons, dwarf planets and spaceflight plans” →

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.

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.

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.

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.

Continue reading “Space Sunday: taking an elevator into space” →