Soyuz – What next?

Many of my readers will be aware the Soyuz MS-10 spacecraft failed to get into orbit on Thursday 11 October. It was on a mission to take fresh crew to the International Space Station (ISS).

Mission patch for Soyuz MS-10

A major fault occurred at an altitude of about 50 km when the booster rocket failed, causing the spacecraft to start falling back to Earth. Fortunately, the space capsule containing the crew separated successfully from the faulty rocket and the astronauts landed unharmed.

The Russian Space agency is now investigating the cause of the failure. The next mission to rotate the ISS crew,  Soyuz MS-11,  was  scheduled to take place on 20 December, but this has now been put on hold. Hopefully the cause of the failure will be identified and rectified, enabling the launch to happen as originally planned. However, if Soyuz is grounded for a longer period then the existing crew will have to abandon the ISS (using a Soyuz spacecraft which is attached to the station) until Soyuz is allowed to fly again or American missions start. This would be the first time that the ISS has been unoccupied since Nov 2000, when the first crew arrived.

This failure underlies how dependent America and the other nations are on Soyuz, a spacecraft first flown more than 50 years ago. For the rest of this post I’ll talk about this spacecraft which has effectively become the space station ‘taxi’.

The First Mission

On 23 April 1967, six years after Yuri Gagarin had became the first man to go into space, a Soviet Soyuz spacecraft was launched carrying cosmonaut Vladimir Komorov. He completed 18 orbits and then returned to Earth.

Mission patch for the first Soyuz mission

Sadly, during reentry the parachute failed to open properly and the spacecraft was destroyed when it hit the Earth at high speed and burst into flames – killing Komorov and giving him the unfortunate distinction of being the first person to die in space flight.

Despite this initial setback, the Soyuz spacecraft was successfully flown back into space the following year, when cosmonaut Georgy Beregovoy, a decorated World War 2 hero, completed 81 orbits and landed safely.

A Soviet 10 kopek stamp showing  Georgy Beregovoy. The Soyuz rocket is in the background – image from Wikimedia commons

Since Beregovoy’s mission, Soyuz has been launched into space a further 137 times, and has proved to be a great success, outliving the vastly more expensive  technologically advanced Space Shuttle. It has established itself to be a reliable and safe way of getting into Earth orbit.  In fact, since the retirement of the Space Shuttle in 2011, it has been the only way of getting astronauts to and from the ISS.  A fact worth bearing in mind given the somewhat tense relationship between Russia and the West.

The spacecraft

The Soyuz spacecraft was designed in the Soviet Union in the early 1960s. The chief designer was a man called Sergei Korolev (1907-1966), who was the driving force behind many of the early successes in the Soviet space programme.

Korolev in 1956 – image from Wikimedia Commons

Korolev had a chequered career. In 1938 he fell foul of the authorities and was arrested by the Soviet secret police, tried and sentenced to death. The sentence was reduced to imprisonment and he spent number of months in a Soviet gulag – a hard labour camp – in a remote part of Siberia. Conditions were extremely harsh and many prisoners died from cold, disease and sheer exhaustion.  Towards the end of the Second World War he was rehabilitated by the Soviet government and rose up the ranks in the 1950s to head the space programme. He died in Jan 1966 at the age of 59, his final years plagued by ill health caused by his time in the gulag.  In the 1950s and 1960s  the Soviet space programme was kept under intense secrecy and, unlike his American counterparts,  Korolev was unknown outside a small elite. His achievements were only made public after his death.

 

The Soyuz spacecraft, shown above, consists of three modules:

  • The first part of the spacecraft is the service module (labelled A). This contains the main engines, fuel, oxygen, computers, communications equipment and the solar panels used to generate electricity
  • The reentry capsule (labelled B) is shaped like a hemisphere and is the only part of the spacecraft which returns to Earth. The cosmonauts enter the capsule just before reentry. It is very cramped and is only designed for the crew to stay in for a short period of time. It does not, for instance, have a toilet.
  • The spherical-shaped orbital module (labelled C) is where the crew live during a mission, although  because all Soyuz missions  are at the moment to and from the ISS, astronauts only spend a short time there.

At launch the spacecraft sits on top of a 45 metre (150 feet) tall Soyuz rocket. The solar panels are folded away, and are unfolded when the spacecraft is in orbit.

Image from Wikimedia commons

As mentioned above, conditions in the reentry capsule are very cramped. It carries a crew of three squeezed into only 2.5 cubic metres of usable space. This is the volume of a cube measuring 1.36 by 1.36 by 1.36 metres. These cramped conditions meant that, in the early Soyuz spaceflights, the cosmonauts couldn’t wear bulky spacesuits and the associated life support equipment. This unfortunately lead to the deaths of the cosmonauts in the Soyuz 11 mission in 1971 who suffocated when a faulty valve caused all the air to escape from their capsule. Had they been wearing spacesuits they would have survived. After this accident Soyuz was redesigned to carry only two cosmonauts, both wearing spacesuits, although this was later increased back to three. The redesigned spacecraft was known as the Soyuz Ferry because its mission was to transport cosmonauts to and from the Salyut space station.

Over the last 50 years Soyuz has gone through several further updates and the latest version, known as Soyuz MS, was first launched in July 2016. The upgrades are mainly to computers, electronics and navigational systems and the internal layout of the spacecraft. The fundamental design hasn’t changed since Kamorov’s first flight back in 1967.

A safe and reliable way of getting into space.

Since 1971 there have been no fatalities on a Soyuz mission and the spacecraft has proven itself to be a safe, relatively cheap and reliable way of getting people to and from the International Space Station (ISS).  The recent failure was the first for 43 years and it important to emphasise that the  astronauts escaped unharmed.

In 2011 the cost of a flying a Space Shuttle mission to the ISS worked out at about $500 million in today’s money (NASA 2011). In contrast, the cost of using the older Soviet-era Soyuz technology worked out more than eight times cheaper at the equivalent of $60 million per mission (Wade 2016).

The table below shows the number of missions flown by the Apollo, Soyuz, Space Shuttle and Shenzou spacecraft.

Only manned missions are included. So, although the Shenzou spacecraft has gone into orbit 11 times only 6 of these missions had humans aboard.

 

NASA and Soyuz

NASA pays Russia $70 million per seat for each astronaut who flies in Soyuz (Wall 2013). This figure, which is roughly the same as the per seat cost of the Space Shuttle ($500 million for a crew of seven), enables the Russian space agency to make a significant profit.

However, NASA won’t be entirely reliant on buying seats on Soyuz for much longer.  As readers of my blog will know, rather than designing and building new craft to fly crew to and from the ISS, NASA administers a US-government funded programme called Commercial Crew Development (CCDev). After a lengthy evaluation process NASA announced on 16 September 2014 that Boeing and SpaceX had received contracts to provide crewed launch services to the ISS.

When the final decision was made, NASA hoped that the winning companies would be able to launch manned missions to the ISS by 2017. However, perhaps unsurprisingly, there have been numerous delays in the development of both spacecraft and the launch dates have slipped.

According to the current launch schedule (https://www.nasa.gov/launchschedule/ ), the target dates for unmanned test flights are:

  • ‘March 2019′  for Boeing CT100
  • ‘January 2019’ for SpaceX Dragon v2

However, it must be be pointed out that they are only target dates and it is possible that they will slip further.

If there are no further delays and these test flights do take place as planned and are successful, then in June 2019 the SpaceX Dragon v2 spacecraft will be the first American spacecraft to carry astronauts into orbit since the retirement of the Space Shuttle. This will be followed by the Boeing CT100, shown below, in August 2019.

DragonV2

 The Dragon V2 spacecraft – image from NASA 

Replacement of Soyuz

In the longer term Soyuz is due to be replaced in 2023 by a new spacecraft called Federation.  The design of Federation is still at the early stages but it will be capable of both low Earth orbit missions such as ferrying astronauts to and from the ISS and also missions deeper into space, such as orbiting the Moon (Nowakowski 2016).

Artist’s concept of the Federation spacecraft. image from  Roscosmos


I hope you have enjoyed this post. To find out more about the Science Geek’s blog, click here or at the Science Geek Home link at the top of this page.


Notes

1 The total includes all Soyuz missions which were launched with humans on board, including the two missions where the spacecraft failed to get into orbit.

2 After the last spaceflight to the Moon, there were 4 further Apollo spaceflights:

  • 3 to the Skylab space station in 1973 and 1974.
  • 1 joint mission with the Soviet Union known as Apollo-Soyuz in 1975.

3 The total of 135 Space Shuttle missions includes the ill fated Challenger mission in 1986 when the spacecraft broke apart 73 seconds after take off.

References

NASA (2011) How much does it cost to launch a Space Shuttle?, Available at:http://www.nasa.gov/centers/kennedy/about/information/shuttle_faq.html#1 (Accessed: 15 October 2017).

Nowakowski, T (2016) Russia runs first tests of its next-generation “Federation” manned spacecraft, Available at: http://www.spaceflightinsider.com/organizations/roscosmos/russia-runs-first-tests-of-its-next-generation-federation-manned-spacecraft/ (Accessed: 15 October 2018).

Wade, M. (2016) Cost, Price, and the Whole Darn Thing, Available at:http://www.astronautix.com/c/costpriceanholedarnthing.html (Accessed: 15 October 2018).

Wall, M (2013) NASA to pay $70 Million a seat to fly astronauts on Russian spacecraft,Available at: http://www.space.com/20897-nasa-russia-astronaut-launches-2017.html(Accessed: 25 April 2016).

Space stations past and present

The International Space Station (ISS) is now 20 years old. In this post I’ll talk about the history of the ISS and other space stations, and I’ll also touch on some of the politics involved.

Image from NASA

 

Early space stations

 

Although America was the first country to put a man on the Moon, the Soviet Union led the way in long duration spaceflights and was the first country to launch a space station, where humans could  live and work for longer periods of time. Before the advent of space stations, astronauts were confined to cramped space capsules.  Continue reading “Space stations past and present”

Jocelyn Bell and the Breakthrough prize 2018

Pulsars were first detected in 1967 by a research student called Jocelyn Bell when she was taking observations for her PhD thesis. Her supervisor, Anthony Hewish, went on to win the Nobel prize in 1974 for the discovery, and her contribution was overlooked. Many at the time felt that Jocelyn Bell should have been given at least a share in the prize, since she was the person who had initially spotted the signal from the first pulsar.

Jocelyn Bell 

This was finally addressed this month when she was awarded the $2.3 million Physics Breakthrough Prize for the discovery. Previous recipients include Stephen Hawking, researchers at Cern who discovered the Higgs boson, and physicists on the Ligo experiment who detected gravitational waves.

According to the BBC website, Bell has decided to donate her entire winnings to set up a fund to help women, under-represented ethnic minority and refugee students to become physics researchers.

Bell who is now 75 years old told the BBC:

‘I don’t want or need the money myself and it seemed to me that this was perhaps the best use I could put it to.’

If you would like to know more, please see my post from last year on the discovery of pulsars below.

———–

In 1967 Jocelyn Bell, a 24-year-old student from Cambridge University, was doing the research for her PhD. She was using a radio telescope to study radio waves emitted from compact astronomical objects known as quasars, and when she analysed the data, she noticed a signal which appeared to pulse on and off every 1.3 seconds. After doing this continuously for about an hour, the pulsing signal would stop altogether, but it would start again precisely 23 hours 56 minutes later after it had first started. As Jocelyn Bell – and indeed all astronomers – knew, the Earth rotates on its axis once every 23 hours 56 minutes, a period of time called a ‘sidereal day’, and the fact that the pulsating signal was detected at the same time in each sidereal day meant that it must almost certainly be coming from space rather than being man-made as shown below.

 

Not only was the time interval between each pulse very short at only 1.3  seconds, but this time interval was completely constant and didn’t vary to any significant degree.  The fact that the pulses were very short in duration and so regular meant that whatever was emitting the pulses must be extremely small in astronomical terms.  A larger object – something, for example, the size of the Sun – would not be able to generate such precise pulses. For a while Bell and her PhD supervisor Antony Hewish considered the possibility that the mysterious signals were generated by a signaling beacon left by an alien civilisation. For this reason, they briefly nicknamed  the unknown object ‘Little Green Men-1’. However, this explanation was rejected when it became clear that the pulses contained no information and when they also discovered additional pulsing sources in other parts of the sky.

Pulsars

The origin of the mysterious signals turned out to be a hitherto unknown class of astronomical objects, known as neutron stars. Neutron stars are very small, typically around 20 km in diameter, but have an enormous mass – between 1.1 and 3 times the mass of the Sun.  Having such a large mass squeezed into a small volume means that their density is incredibly high.  A cubic centimetre of neutron star material would weigh about 500 million tons. They are called neutron stars because they consist mainly of neutrons, which are subatomic particles found in the nucleus of ordinary atoms. In a neutron star the neutrons are so tightly squeezed together that they are touching each other. Neutron stars also have very strong magnetic fields – around 1 trillion times stronger than the Earth’s.

Neutron stars which rotate extremely rapidly, around once a second, are known as pulsars, and these are the objects which Bell and Hewish had detected. This rotation causes electrically charged particles around the neutron star to move rapidly in the intense magnetic fields. This causes electromagnetic radiation (such as radio waves) to be emitted in two cone-shaped beams along the magnetic North and South poles of the pulsar, shown as B in the diagram below.

In the diagram above A is the axis around which the pulsar rotates and B is the magnetic axis.

As you can see, the magnetic poles are at an angle to the line through the North and South poles of the pulsar about which it rotates. This means that the cone-shaped beams will rotate around the axis of the pulsar and only when either of the beams is pointing directly at the Earth will it be detected. A pulsar behaves like a lighthouse – the light is on all the time but appears to a viewer to switch on when it is pointing towards them and switch off when it is pointing away.

Neutron stars are formed when a large massive star explodes at the end of its life in a violent event known as a supernova. Most of the outer parts of the star are blown out into space by the force of the explosion. The remaining material in the star’s core collapses, forming a neutron star.  In fact, if the remaining material from the star’s core is more than three times the mass of the Sun, a neutron star won’t be formed at all.  Instead, an even more compact object called a black hole will result.

Large stars with a diameter of tens of millions of kilometres rotate relative slowly, taking around one year to complete one rotation. As the star collapses into a small massive object, millions of times smaller in diameter, a law of physics called the conservation of angular momentum causes its rotation to speed up massively.  A  more familiar example of this is from the world of ice skating: ice skaters spin more rapidly when they pull in their arms.

Why this knowledge has been useful to astronomy

In the last 50 years more than 2000 pulsars have been detected. Understanding the properties of pulsars has led to further discoveries in various areas.  For example, it has led to greater understanding of the diffuse gas between stars known as the interstellar medium, and it has also been used to test Einstein’s theory of general relativity. I will discuss these advances in more detail in future posts.

Knowledge of pulsars was also used in a very interesting way in the 1970s.  Four spacecraft were launched, destined to the leave the Solar system and head out into interstellar space. The missions are described in more detail in my previous post Artefacts from Earth.  On each spacecraft there was a diagram devised by the American astronomer, Frank Drake (1930-), consisting of a circle with 15 lines coming out of it.

The centre of the diagram, from which the lines radiate, represents the Sun.  The right-hand end of the longest line (at 3 o’clock) represents the centre of the galaxy. The end of each of the remaining line represents a pulsar and the length of the line between the Sun and the pulsar represents the distance to the pulsar.

The diagram relies on the fact that each pulsar has its own distinct period between pulses. So if, in the far distant future, an alien civilisation were to recover the spacecraft they would be able to identify the pulsars from their periods.  To enable this, each of the lines depicts the length of the pulsar’s period not in seconds (which as a man-made unit would be meaningless to an alien race) but in multiples of a ‘fundamental time unit’ that an alien might understand.  The alien civilisation could then have sufficient information to identify the fourteen pulsars and the distance of the Sun from each pulsar, and thus work out the location of our Solar system within the galaxy.

The Nobel prize controversy

Jocelyn Bell and Antony Hewish published their results in February 1968 (Hewish et al 1968). The discovery of this entirely new type of astronomical object was a major advance. Interestingly, it had been suggested as long ago as 1934 by the astronomers Baade and Zwicky that neutron stars would be the end result of supernova explosions. However, this prediction was ignored. Before 1967 most astronomers regarded neutron stars as hypothetical objects which might or might not actually exist in reality.

Such was the impact of the discovery that it led to the Nobel prize for physics in 1974. Two astronomers were awarded the prize – but Jocelyn Bell was not one of them. Antony Hewish and Martin Ryle were the recipients, the former for the discovery of pulsars and the latter for his work in radio astronomy.  Jocelyn Bell’s contribution was not recognised.

Antony Hewish (1924- ) 

Many at the time felt that Jocelyn Bell should have been given at least a share in the prize, since she was the person who had initially spotted the signal from the first pulsar. The British astronomer Fred Hoyle was particularly vocal on the issue and stated publicly  that Bell should have been given a major share of the prize to acknowledge her contribution. Bell herself said very little about the controversy in the years immediately afterwards. The few statements she made were, in general, supportive of the Nobel prize committee’s decision. In the 1960’s and 1970’s it was commonplace for the senior person leading a team of scientific researchers to get the credit for a major discovery on behalf of the entire team. This is largely still true today.

Bell went on to have a successful academic career and always has been a passionate advocate for getting women more involved in science. From 2002 to 2004 she served as the president of the Royal Astronomical Society, the organisation for British Astronomers. She was the first ever woman to hold that role.  She later served as the first ever female president of the Institute of Physics. In 2006, nearly 40 years after the discovery, she said in an  interview:

In those days, it was believed that science was done, driven by great men . . . And that these men had a fleet of minions under them who did their every bidding, and did not think. It also came at the stage where I had a small child and I was struggling with how to find proper childminding, combine a career, and before it was acceptable for women to work. And so I think at one level it said to me ‘Well men win prizes and young women look after babies.’

Postscript: a different kind of pulsar discovered in 2016

Stars such as the Sun do not end their lives in violent supernova explosions resulting in neutron stars. Instead, when they have used up all their nuclear fuel, the outer layers of the star are blown away into space and form a bright glowing shell of gas called a planetary nebula, shown below.

Planetary Nebula

The remnants of the star’s core collapse into a dense hot star called a white dwarf, an object which is roughly the same size as the Earth.  For the last 50 years astronomers have predicted that some white dwarfs might also form pulsars, although because white dwarfs are much larger and rotate more slowly than neutron stars, the radiation would be much weaker than neutrons star pulsars, making them harder to detect and the pulses would be much longer.  This prediction was finally confirmed in 2016 when a team led by Tom Marsh from Warwick University discovered that the white dwarf star AR Scorpii was a pulsar with a period of about 2 minutes.

References

Baade, W.and Zwicky, F. (1934) ‘Remarks on supernovae and cosmic rays’, Physical Review, 46(1), pp. 76-77.

Hewish, A., Bell. S. J., Pilkington, J. D. H, Scott P. F. and Collins, A (1968) ‘ Observation of a rapidly pulsating radio source’, Nature, 217(), pp. 709-713.

 

September 18 The Shortest Day

Not many people know this, but next Tuesday 18 September, is the shortest solar day of the year. I’ve decided to re-blog my post from 2015 on this interesting fact.

The Science Geek

Revised 10 September 2018

Most people are probably unaware of this but the length of a solar day, which is the natural day measured by the rising and setting of the Sun isn’t  always 24 hours. It varies slightly throughout the course of the year and that September 18 is in fact the shortest solar day in the year. This post discusses this curiosity, which is not widely known.

Background- the variation in the length of the day.

Although a day for practical timekeeping purposes is always 24 hours, the actual length of a solar day, which is the time difference between two successive occasions when the Sun is at its highest in the sky, varies throughout the year. As shown in the graph below, it is at its longest, 24 hours 30 seconds, around Christmas Day and is at its shortest, 23 hours 59 minutes 38 seconds, in mid-September.

Day length

How the length of a solar…

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The International Space Station updated

Since the publication of the original post on 2 August 2018, NASA have delayed the planned launch dates for the American spacecraft to carry astronauts to and from the International Space Station. In my original post I referred to the Boeing and SpaceX spacecraft taking astronauts this year, which was an ambitious target, bearing in mind that it was already August and neither spacecraft had flown an unmanned mission! Perhaps unsurprisingly the planned launch dates have slipped into 2019 and I have updated my post to reflect this.

Original post below——

This year marks the 20th anniversary of the International Space Station (ISS).

Image from NASA.

The first module of the ISS, called Zarya, was launched by a Russian rocket back in November 1998. Zarya was not an inhabitable module and its function was to provide electrical power, storage and propulsion to the ISS during the initial stages of assembly. Interesting the word ‘Zarya’ is Russian for sunrise and Zarya, being the first step in building the ISS, was to signify a new dawn in international cooperation.

The first module of the ISS called Zarya – Image from NASA  Note: the solar panels shown are no longer used and have been retracted.

The ISS has a modular design and in the twenty years since Zarya numerous modules have been added, gradually growing it into the structure we see today.  A key milestone was achieved on 2 November 2000 when a Russian Soyuz spacecraft bought the first crew to the ISS. The ISS has been manned ever since that date, providing a permanent human presence in space. The current crew of the ISS is known as Expedition 56 and consists of: three Americans, two Russians and one German.

Mission patch for Expedition 56 – Image from NASA

Key role of the Space Shuttle

Image from NASA

The American Space Shuttle, which flew between 1981 and 2011, was key to building the ISS. The Shuttle had the capacity to take large modules in its cargo bay and crews of up to six astronauts on assembly missions. Many of these missions involved extended spacewalks. Indeed, without the Space Shuttle it would not have been possible to build the ISS. In fact, post 1998, construction of the ISS became the almost the entire focus of the shuttle programme. This is illustrated by the statistic that of the 43 space Shuttle Missions flown after the launch of Zarya, 38 (89%) of them went to the ISS to deliver a new module and components to the station, bring fresh supplies or to bring fresh crew to the ISS and return the old crew to Earth.

The ISS today

The ISS is shown in the image at the top of this post. Although some minor construction missions are planned later this year and in 2019, the components to be added are relatively small and construction is essentially complete. The ISS is a very flat structure. It is 73 metres long and a maximum of 109 meters wide, but its maximum depth is only a few metres. It has a mass of 420 tons. Its most noticeable feature are the eight separate sets of solar panels, which look like giant wings and in total generate up to 90 kilowatts of electric power (NASA 2018).

The orbit of the ISS 

The ISS orbit is almost perfectly circular, just over 400 km above the Earth’s surface. At this altitude, although it is classified as being in space, which begins at an altitude of 100 km, (see my previous post), here are sufficient traces of the Earth’s atmosphere to cause the ISS to lose energy as it moves against the air resistance caused by this very thin gas. This causes the ISS to very gradually spiral down to Earth as it loses a small amount of energy on each orbit. The distance a satellite drops in altitude is known as its orbital decay and for the ISS is 2 km per month, which works out at about 70 metres per day. If nothing were done the ISS would gradually return to Earth within a few years and as it hit the thicker atmosphere it would disintegrate. To prevent this happening the ISS has a set of thrusters, which are fired periodically to boost it into a higher orbit. Visiting spacecraft also fire their rocket motors to the same effect.

Because it is both large and travels in a low orbit, the ISS can be easily seen from Earth. It is visible to the naked eye as a slow-moving, bright white dot. Its brightness is due to sunlight reflecting off its solar panels. The best time to see it is either after sunset or before sunrise, when the station remains sunlit, but the sky is dark.  This is shown in the diagram below.

The ISS takes about 90 minutes to complete an orbit. As it moves around its orbit:

  • the ISS is visible at night between sunset, point A, and when it disappears behind the Earth’s shadow, point B;
  • between points B and C the ISS is in the Earth’s shadow it receives no direct sunlight and cannot be seen;
  • between point C, when it emerges from the Earth’s shadow, and point D, sunrise, the ISS is visible;
  • between points D and A, the ISS cannot be easily seen against the brightness of the daytime sky.

Because of its size, the ISS is the brightest artificial object in the sky and has a similar brightness when overhead to the planet Venus.

 

Research at the ISS

A good deal of research is carried out at the ISS. This is described in more detail at the following website  https://www.nasa.gov/mission_pages/station/research/overview.html.  Much of this research is based upon the fact that that the strength of gravity is very close to zero in the ISS. This is known as micro-gravity and the only place it is possible to create a micro-gravity environment, for longer than a few minutes, is in space. Some examples of this research are given below.

  • Fluids can be almost completely combined in micro-gravity, so physicists can investigate fluids that do not mix well on Earth.
  • In micro-gravity environment combustion occurs differently. Flames have a spherical shape. In the diagram below, the candle on the left is in normal gravity, whereas the candle on the right is in micro-gravity.

Image from NASA

  • Research has been carried out as to how plants develop in micro-gravity. Interestingly, results have shown that plants use light rather than gravity to determine which direction is ‘up’.

But perhaps the most interesting area of research are the effects on the human body of spending long periods on time in near weightlessness. This area is important, because in the next few decades when astronauts travel to Mars they will have to spend at least six months in zero gravity when travelling to the red planet and a further six months on the return journey. Some of the effects which have been found are.

  1. Without any weight to work against, muscles gradually will get smaller and lose their strength. This includes the heart muscle.
  2. Fluid shifts around the body causing fluid pressure in the brain to increase.
  3. One of the most serious problems is that, without gravity, a strong skeleton is not needed to support the body. Studies have shown that astronauts lose 1-2 % of their bone mass for each month of weightlessness; the calcium from their bones is excreted in their urine. So much calcium may be lost that it can cause kidney stones.

Research on the ISS has shown that to retain their muscle mass, and ensure their heart stays in good condition, astronauts need to spend many hours a day exercising.  Because there is no weight for their muscles to work against, astronauts often spend a large fraction of the day running on a treadmill, using elastic harnesses to provide resistance.

However, nothing has been discovered which can prevent the loss of bone density. The rate of bone loss continues at 1-2% per month and does not level off after long durations in space. After more than two years in low gravity, astronauts’ bones would be so weak they would easily fracture and would be unable to support their weight then they returned to Earth. This may be a limiting factor for how long humans can spend in zero gravity environments, especially since it takes a significant time for the bone density to return to normal.

A further limiting factor is that on long duration spaceflights astronauts will be exposed to high doses of radiation. This can cause genetic damage making the astronauts more prone to cancer in later life.

Taller Astronauts

Spending time in a microgravity environment causes the spine to elongate. On Earth, gravity keeps the vertebrae in place by constantly pushing them together. But without gravity, the vertebrae will naturally expand slightly, causing a person to become taller.

 

Typically, astronauts in space can grow up to three percent of their original height. For example, in 2016 when Scott Kelly came to Earth after spending nearly a year in space he was 2 inches (5 cm) taller. However, this gain in height is only temporary. When under the effects of gravity again astronauts return to their original height.

Scott Kelly – Image from NASA

Getting to and from the ISS

Since the end of the Shuttle programme the only way astronauts can get to and from the ISS is by the Russian Soyuz spacecraft, a point worth remembering now that relations between the US and Russia are rather strained.  Soyuz was first flown in 1967 and its design has changed little since then. Like the Apollo spacecraft which took astronauts to the Moon, it is a single use spacecraft.  Currently NASA pay $70 million for each astronaut who flies in the Soyuz spacecraft (Wall 2013), which enables the Russian space agency to make a significant profit.

In the next few years US spacecraft should return to space.  Rather than build a new craft to fly crew to and from the ISS, NASA administer a US-government funded programme called Commercial Crew Development (CCDev). After a lengthy evaluation process NASA announced in September 2014 that Boeing and SpaceX had received contracts to provide crewed launch services to the ISS.

When the final decision was made, NASA hoped that the winning companies would be able to launch manned missions to the ISS by 2017. However, perhaps unsurprisingly, there have been numerous delays in the development of both spacecraft and the launch dates have slipped.

According to the current launch schedule (https://www.nasa.gov/launchschedule/ ), the target dates for unmanned test flights are:

  • ‘late 2018 / early 2019’ for the Boeing spacecraft
  • ‘November 2018’ for SpaceX.

However, it must be be pointed out that they are only target dates and may slip further.

If there are no further delays and these test flights do take place as planned and are successful, then in April 2019 the SpaceX Dragon v2 spacecraft will be the first American spacecraft to carry astronauts into orbit since the retirement of the Space Shuttle. This will be followed by the Boeing CT100, shown below, in the middle of the year.

The Boeing CT-100 Starliner Space Capsule – image from NASA. In lmid 2019 this spacecraft may take astronauts to and from the ISS.

Next post

I hope you’ve enjoyed this post. In my next post I’ll talk about the costs of the space station, international cooperation in space and how I see the future of the ISS.

 

 

NASA (2018) International Space Station facts and figures, Available at: https://www.nasa.gov/feature/facts-and-figures (Accessed: 30 July 2018).

 

Wall, M (2013) NASA to pay $70 Million a seat to fly astronauts on Russian spacecraft,Available at: http://www.space.com/20897-nasa-russia-astronaut-launches-2017.html(Accessed: 30 July 2018)

 

 

The International Space Station

Note 10 September 2018.  The information in the section ‘Getting to and from the ISS’ has been superseded by information in the updated version of this post.

This year marks the 20th anniversary of the International Space Station (ISS).

Image from NASA.

The first module of the ISS, called Zarya, was launched by a Russian rocket back in November 1998. Zarya was not an inhabitable module and its function was to provide electrical power, storage and propulsion to the ISS during the initial stages of assembly. Interesting the word ‘Zarya’ is Russian for sunrise and Zarya, being the first step in building the ISS, was to signify a new dawn in international cooperation.

The first module of the ISS called Zarya – Image from NASA  Note: the solar panels shown are no longer used and have been retracted.

The ISS has a modular design and in the twenty years since Zarya numerous modules have been added, gradually growing it into the structure we see today.  A key milestone was achieved on 2 November 2000 when a Russian Soyuz spacecraft bought the first crew to the ISS. The ISS has been manned ever since that date, providing a permanent human presence in space. The current crew of the ISS is known as Expedition 56 and consists of three Americans, two Russians and one German.

Mission patch for Expedition 56 – Image from NASA

Key role of the Space Shuttle

Image from NASA

The American Space Shuttle, which flew between 1981 and 2011, was key to building the ISS. The Shuttle had the capacity to take large modules in its cargo bay and crews of up to six astronauts on assembly missions. Many of these missions involved extended spacewalks. Indeed, without the Space Shuttle it would not have be possible to build the ISS. In fact, post 1998, construction of the ISS became the focus of the shuttle programme. This is illustrated by the statistic that of the 43 space Shuttle Missions flown after the launch of Zarya, 38 (89%) of them went to the ISS to deliver a new module and components to the station, bring fresh supplies or to rotate crew.

The ISS today

The ISS is shown in the image at the top of this post. Although a few more construction missions are planned later this year and in 2019, the components to be added are relatively small and construction is essentially complete. The ISS is a very flat structure. It is 73 metres long and a maximum of 109 meters wide, but its maximum depth is only a few metres. It has a mass of 420 tons. Its most noticeable feature are the eight separate sets of solar panels, which look like giant wings and in total generate up to 90 kilowatts of electric power (NASA 2018).

The orbit of the ISS 

The ISS orbit is almost perfectly circular, just over 400 km above the Earth’s surface. At this altitude, although it is classified as space (which begins at an altitude of 100 km, see my previous post ), there are sufficient traces of the Earth’s atmosphere to cause the ISS to lose energy as it moves against the air resistance caused by this very thin gas. This causes the ISS to very gradually spiral down to Earth as it loses a small amount of energy on each orbit. The distance a satellite drops in altitude is known as its orbital decay and for the ISS is 2 km per month, which works out at about 70 metres per day. If nothing were done the ISS would gradually return to Earth within a few years and as it hit the thicker atmosphere it would disintegrate. To prevent this happening the ISS has a set of thrusters, which are fired periodically to boost it into a higher orbit. Visiting spacecraft also fire their rocket motors to the same effect.

Because it is both large and travels in a low orbit, the ISS can be easily seen from Earth. It is visible to the naked eye as a slow-moving, bright white dot. Its brightness is due to sunlight reflecting off its solar panels. The best time to see it is either after sunset or before sunrise, when the station remains sunlit, but the sky is dark.  This is shown in the diagram below.

The ISS takes about 90 minutes to complete an orbit. As it moves around its orbit:

  • the ISS is visible at night between sunset, point A, and when it disappears behind the Earth’s shadow, point B;
  • between points B and C the ISS is in the Earth’s shadow it receives no direct sunlight and cannot be seen;
  • between point C, when it emerges from the Earth’s shadow, and point D, sunrise, the ISS is visible;
  • between points D and A, the ISS cannot be easily seen against the brightness of the daytime sky.

Because of its size, the ISS is the brightest artificial object in the sky and has a similar brightness when overhead to the planet Venus.

 

Research at the ISS

A good deal of research is carried out at the ISS. This is described in more detail at the following website  https://www.nasa.gov/mission_pages/station/research/overview.html.  Much of this research is based upon the fact that that the strength of gravity is very close to zero in the ISS. This is known as microgravity and the only place it is possible to create a microgravity environment for longer than a few minutes is in space. Some examples of this research are given below.

  • Fluids can be almost completely combined in microgravity, so physicists can investigate fluids that do not mix well on Earth.
  • In microgravity environment combustion occurs differently. Flames have a spherical shape. In the diagram below, the candle on the left is in normal gravity, whereas the candle on the right is in microgravity.

Image from NASA

  • Research has been carried out as to how plants develop in microgravity. Interestingly, results have shown that plants use light rather than gravity to determine which direction is ‘up’.

But perhaps the most interesting area of research are the effects on the human body of spending long periods on time in weightlessness. This area is important, because in the next few decades when astronauts travel to Mars they will have to spend at least six months in zero gravity when travelling to the red planet and a further six months on the return journey.

  • Without any weight to work against, muscles gradually will get smaller and lose their strength. This includes the heart muscle.
  • Fluid shifts around the body causing fluid pressure in the brain to increase.
  • One of the most serious problems is that, without gravity, a strong skeleton is not needed to support the body. Studies have shown that astronauts lose 1-2 % of their bone mass for each month of weightlessness; the calcium from their bones is excreted in their urine. So much calcium may be lost that it can cause kidney stones

Research on the ISS has shown that to retain their muscle mass, and ensure their heart stays in good condition, astronauts need to spend many hours a day exercising.  Because there is no weight for their muscles to work against, astronauts often spend a large fraction of the day running on a treadmill, using elastic harnesses to provide resistance.

However, nothing has been discovered which can prevent the loss of bone density. The rate of bone loss continues at 1-2% per month and does not level off after long durations in space. After more than two years in low gravity, astronauts’ bones would be so weak they would easily fracture and would be unable to support their weight then they returned to Earth. This may be a limiting factor for how long humans can spend in zero gravity environments, especially since it takes a significant time for the bone density to return to normal.

A further limiting factor is that on long duration spaceflights astronaut would be exposed to high doses of radiation. This can cause genetic damage making the astronauts more prone to cancer in later life.

Taller Astronauts

Spending time in a microgravity environment causes the spine to elongate. On Earth, gravity keeps the vertebrae in place by constantly pushing them together. But without gravity, the vertebrae will naturally expand slightly, causing a person to become taller.

 

Typically, astronauts in space can grow up to three percent of their original height. For example, in 2016 when Scott Kelly came to Earth after spending nearly a year in space he was 2 inches (5 cm) taller. However, this gain in height is only temporary. When under the effects of gravity again astronauts return to their original height.

Scott Kelly – Image from NASA

Getting to and from the ISS

Since the end of the Shuttle programme the only way astronauts can get to and from the ISS is by the Russian Soyuz spacecraft, a point worth remembering now that relations between the US and Russia are rather strained.  Soyuz was first flown in 1967 and its design has changed little since then. Like the Apollo spacecraft which took astronauts to the Moon, it is a single use spacecraft. The astronauts return to Earth in a small capsule which has a heat shield to protect it during the most dangerous part of the mission, re-entry into the Earth’s atmosphere. Currently NASA pay $70 million for each astronaut who flies in the Soyuz spacecraft (Wall 2013), which enables the Russian space agency to make a significant profit.

In the next few years US spacecraft should return to space.  Rather than build a new craft to fly crew to and from the ISS, NASA administer a US-government funded programme called Commercial Crew Development (CCDev). After a lengthy evaluation process NASA announced in September 2014 that Boeing and SpaceX had received contracts to provide crewed launch services to the ISS.

When the final decision was made, NASA hoped that the winning companies would be able to launch manned missions to the ISS by 2017. However, perhaps unsurprisingly, there have been numerous delays in the development of both spacecraft and the launch dates have slipped.

According to the current launch schedule (https://www.nasa.gov/launchschedule/ ), the target dates for unmanned test flight of both spacecraft are actually this month, August 2018, although precise date haven’t been specified. If there are no further delays and these test flights do take place this month and are successful, then in November 2018 the Boeing CT 100 spacecraft will be the first American spacecraft to carry astronauts into orbit since the retirement of the Space Shuttle. This will be followed by the SpaceX Dragon v2 the following month.

 

Next post

I hope you’ve enjoyed this post. In my next post I’ll talk about the costs of the space station, international cooperation in space and how I see the future of the ISS.

 

 

NASA (2018) International Space Station facts and figures, Available at: https://www.nasa.gov/feature/facts-and-figures (Accessed: 30 July 2018).

 

Wall, M (2013) NASA to pay $70 Million a seat to fly astronauts on Russian spacecraft,Available at: http://www.space.com/20897-nasa-russia-astronaut-launches-2017.html(Accessed: 30 July 2018)

 

 

Lunar eclipse 27 July 2018

On 27 July 2018 there will be a total eclipse of the Moon, which will be viewable from many areas of the world. This will be the first total lunar eclipse able to be observed in the UK for nearly three years and it will be worth making the effort to see, especially since, for viewers in Europe, Africa and eastern Asia, it will occur at a sociable hour in the evening.

NASA Image Lunar Eclipse

The Moon during a recent total lunar eclipse – image from NASA

 

What happens during a lunar eclipse?

A lunar eclipse occurs when the Earth prevents some or all of the Sun’s light from hitting the Moon’s surface. This is shown in the diagram below:

 

Image from Wikimedia Commons

In this diagram in the region marked Umbra the Earth completely blocks the Sun. In the region marked Penumbra the Earth partially blocks the Sun.

 

The stages of the July 27 lunar eclipse

The next diagram below shows how, to someone on Earth, the Moon will move through the Earth’s shadow on 27 July. The six points labelled P1, U1, U2, U3, U4 and P4 are known as the eclipse contacts and are the times when the eclipse moves from one stage to the next.

 

 

Diagram from NASA

 

At point P1 the Earth will start to block some of the Sun’s light from reaching the Moon.  This will start at 5:15 pm GMT and is the start of the penumbral phase. The Moon’s brightness will dim a little, but this will be quite difficult to notice with the naked eye.

 

As the Moon continues in its orbit, more and more of the Sun’s light is obscured, until after about an hour some of the Moon will get no direct sunlight.  This is known as the partial phase. It will start at point U1 which will occur at 6:24 GMT. The part of the Moon which receives no direct sunlight will appear dark, as shown in the picture below.

.

Lunar_eclipse_ Partial

The partial phase of a lunar eclipse – Image from Wikimedia Commons

 

After a further hour the Earth will block all direct sunlight from reaching the entire Moon. This is shown as U2 is the diagram and this total phase will start at 7:30 PM. In the total phase, rather than disappearing completely, the Moon goes a dull red colour as shown in the picture at the top of this post. This is because, even though no direct sunlight can reach the Moon, some light from the Sun is bent round the Earth’s atmosphere towards the Moon. This light appears red because visible light from the Sun is a mixture of different wavelengths – red light has the longest wavelength and violet the shortest. Most of the light of the shorter wavelengths  (orange, yellow, green, blue, indigo and violet) is removed from this light bent by the Earth’s atmosphere by a process called scattering, which I discussed in an earlier post https://thesciencegeek.org/2015/09/30/why-is-the-sky-blue/ . The same effect causes the western sky to be red after sunset on a clear day.

Interestingly, if we could stand on the surface of the Moon and view the eclipse we would see a red ring around the Earth.

The Moon will emerge from the total phase (point U3) at 9:13 GMT, the partial phase (point U4) will end at 10:19 PM and the eclipse will finish (P4) at 11:29 PM.

Which areas of the world can see the eclipse?

The eclipse timings are summarised below

Data from NASA (2009)

Not all areas of the world will be able to see the eclipse. This is because the Moon will have already set after the eclipse starts or will not have risen before it finishes. Other places will only be able to see part of the eclipse.

  • In Manchester where Mrs Geek and I live, the Moon will rise at 9:06 PM local times which is 8:06 PM GMT, so when the Moon rises the total eclipse will already be underway.
  • In Manila, the Moon will set at 5:44 am on July 28, Philippine Standard Time (PST) which is 9:44 PM GMT, so viewers will miss part of the final partial phase because this will occur after the Moon has set.

I have adapted the diagram below from NASA (2009) and this shows where in the world the eclipse can be seen.

The regions labelled A to L are as follows

 

 

 

How often do lunar eclipses occur?

Even though the Moon takes roughly a month to orbit the Earth, lunar eclipses do not occur every month. The Moon’s orbit around the Earth is tilted at about five degrees with respect to the Earth’s orbit around the Sun, as shown below.

.

Moon Tilt

This means that during most lunar months, as seen from the Moon, the Earth passes just below or just above the Sun rather than obscuring it. There are only two time windows in a year when a lunar eclipse can occur.  These two points are known as the nodes (See note 2). Even then most lunar eclipses are partial eclipses where the Earth only partially covers the Moon.

 

Notes

 

  1. GMT versus UTC

Although the term Greenwich Mean Time (GMT) is often used in popular writing it is no longer used by astronomers.  Instead, they use two different times which agree with each other to within 1 second.

  • Universal Time, often abbreviated to UT1, is the mean solar time, the time determined by the rising and setting of the Sun at the Greenwich Meridian, zero degrees longitude.
  • Co-ordinated Universal Time, usually abbreviated to UTC, is the time measured by atomic clocks and is kept to within 1 second of UT1 by the addition of leap seconds.

 

In common use, GMT is often taken to be the same as UTC, which is the approach I have taken for this post. However, it can also be taken to mean UT1. Owing to the ambiguity of whether UTC or UT1 is meant, and because timekeeping laws usually refer to UTC, the term GMT is normally avoided in precise writing.

 

  1. Nodes when eclipses can occur

The two nodes when a lunar eclipse can occur aren’t the same dates every year but change from year to year due to an astronomical effect called precession of the line of nodes.

References

NASA (2009) Total lunar eclipse of 2018 July 2017, Available at: https://eclipse.gsfc.nasa.gov/LEplot/LEplot2001/LE2018Jul27T.pdf (Accessed: 8 July 2018).