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Skywatching

Old tech takes us into space

A few days ago, a SpaceX launcher and spacecraft took four astronauts to spend several months on the International Space Station.

The new space systems are safer, more efficient and more sophisticatedly controlled, and boosters can fly home and land for reuse. However, today's launches look much like those of the '50s and 60s. Basically, as yet we have not come up with anything better than the multi-stage rocket, where one rocket piggybacks others partway up.

Surprisingly, the first multi-stage rockets were invented in the 14th Century by the Chinese. They mounted several small rockets on the front of a big one. When the big rocket had burned all its fuel, the smaller ones fired off, having been given a leg up.

Modern multistage space vehicles are still based mainly on the ideas of two people: Konstantin Tsiolkowsky and Wernher von Braun.

If we want to get to the International Space Station, for example, we need a space vehicle system that can lift what we want to deliver to a height of about 410 kilometres and accelerate it to a speed of almost eight kilometres a second.

This takes a lot of fuel, and since a rocket spends most of its operational time in the extreme upper atmosphere and in space, it has also to carry the oxygen needed to burn that fuel.

Then, to contain it we need tanks. To deliver it to the engines we need pumps. The whole lot needs to be supported in a structure that can accommodate accelerations many times that of gravity, handle severe vibrations and stresses, and function in space.

This means lots of weight. Even so, in a modern rocket, the weight of fuel and oxygen can be up to several times the total weight of the hardware.

As the fuel and oxygen are consumed, the tanks become increasingly empty, and more and more of the structure becomes dead weight. There is no point in carrying it all into orbit, and indeed, as yet we have not been able to make a single-stage rocket that is a useful means of getting out into space.

We have standardized on the use of multi-stage rockets. We make a stack of rockets and put what we want to deliver into space, the payload, usually on top.

At launch, we fire the bottom, or first stage. Because it has the most weight to lift, it is usually the biggest. Sometimes we need to strap on additional rockets — boosters — in order to get more thrust. The first stage gets us to 50-80 km, above most of the atmosphere and up to a speed of a several thousand kilometres an hour.

When its fuel and oxygen is all used up, the first stage is dropped. In the past it used to be discarded. In the modern, SpaceX system, some fuel and oxygen are retained in the first stage and used to land it safely back on Earth.

Since this is a large and expensive piece of hardware, being able to reuse it leads to large cost savings. The second stage now fires. At the same time the path of the spacecraft is tilting down, until when it reaches orbital speed, it is moving parallel to the ground.

When this has exhausted its fuel, or the required velocity has been reached, it too is discarded. Leaving it attached to the spacecraft just means more dead weight to manoeuvre and also the risks associated with any unburned fuel.

The spacecraft is now freely in orbit. It is equipped with low-power thrusters that can be used to make the small changes in speed, direction or attitude needed to rendezvous with the space station. If we want to go further, for example, to the Moon, we can add an extra stage.

Reducing the amount of excess weight we have to lift or accelerate reduces costs and in many cases make the missions possible. Even after decades, the ideas of Tsiolkowsky and von Braun still define how we access space.

  • After dark, Saturn and Jupiter lie close together, low in the southwest
  • Mars is rising in the east.
  • Venus lies in the dawn glow with Mercury below and hard to spot. 
  • The Moon is Full on the 30th. 




Moon's a watery world

For many years astronomers have been puzzling over the question "Why is the Earth so wet?

Two thirds of our planet is covered with water, and the parts of the Earth above the water level are covered with features shaped by water. Astronauts on the moon looked back on a blue world, patched with pure white clouds, evidence of a uniquely wet world. 

However, is it uniquely wet?

The Apollo astronauts brought back a large collection of samples of lunar soil and rocks. One thing they had in common was that they were all very dry. This makes sense.

The moon has almost no atmosphere, so there is no greenhouse effect and all the incoming solar energy hits the ground. The result is daytime temperatures reaching about 130 Celsius, and then falling at night to -170 Celsius.

These temperatures vary with latitude, as they do on the Earth, There are some places, such the depths of craters that never see the Sun where the temperature is as low as -250 Celsius.

This combination of baking and freezing in a vacuum is a good way to dry something, especially if this process has been repeating since the moon and Earth formed, about 4.5 billion years ago.

However, given that both formed from the same ingredients, the moon must also have been a watery world once. Is it still?

If you were to visit the Arctic during the summer, you would first notice the mosquitoes. The second would be that the weather is nice and warm. However, if you were to push a thermometer into the ground, you would find that some distance below the surface, the temperature is below freezing, even in high summer.

This is the permafrost, because it stays frozen throughout the year. Under the insulating layer of soil, the temperature hovers around an average value, staying constant over the year. If this average is below freezing, water down there is always frozen.

On the same basis, if we were to stick a thermometer into the surface of the moon, at some depth we will find the temperature unchanging, around a chilly -40 C.

We have measured the moon's average temperature in other ways, such as using radio telescopes. Short radio wavelengths tell us the temperature of the surface layers. Longer ones tell us the temperatures deeper down, where they are unchanging.

During the early history of the Earth, a lot of water mixed in with the construction material was ejected into the atmosphere, initially as superheated steam. Eventually temperatures fell enough for the first rain to fall, and it rained for a very long time, forming the oceans.

Even today, most of the Earth's water is buried deep in the planet. The moon is smaller than the Earth, leading to the loss of its atmosphere to space, and it cooled off faster.

However, it did form from the same mixture of construction materials, so we should expect there to be quite a lot of water on the moon, somewhere.

Sensitive instruments have detected water molecules at the moon's surface, probably from somewhere inside. Solar radiation would break these up into hydrogen and oxygen, which are lost to space.

However, there are accumulations of ice in deep craters, particularly in the polar regions, in places where the sunlight never reaches. This is certainly encouraging from the point of view of space exploration, because it means people on the Moon can use the local product.

This water would be good for more than just drinking. It can be chemically split into hydrogen and oxygen, yielding components for rocket fuel-and breathable air. If there are large quantities of water ice buried deep in the moon, life for the visitors will be far easier. However, building in permafrost is a challenge.

  • After dark, Saturn and Jupiter lie low in the southwest
  • Mars is rising in the east.
  • Venus lies high in the dawn glow with Mercury below. 
  • The Moon will reach First Quarter on the 21st. 


Finding the stuff of life

Earth was born about 4.5 billion years ago, along with the Sun and all the other bodies making up the Solar System.

Since living things appeared on Earth pretty well as soon as the planet was cool enough for water to puddle on its surface, the raw materials of life must have arrived by then.

All life on Earth is based upon the element carbon, so some primordial mix of carbon compounds must have been available for things to get started. What were these chemicals? How did we get them? If we can answer these questions, we can get an idea of how life got started.

We stand little chance of finding these primordial carbon compounds by looking at the Earth. Over time, the material from which the Earth formed has been part of living things, built into rocks, recycled by sub-duction and re-emergence at the surface, probably multiple times.

It is unlikely there are anything more than faint traces of these primordial carbon compounds left, and if so, how could we conclusively identify them?

Out in space there is still a huge amount of Solar System construction material left over. It ranges from fine-grained dust to lumps hundreds of kilometres in diameter. On any clear night we will see the odd meteor, or shooting star: a short-lived bright streak across the sky.

This marks the arrival of a grain or chip of this construction material. It is moving at tens of kilometres a second and the heat of friction when it crashes into our atmosphere vaporizes it. The result is a continuous tenuous rain of fine dust, adding up to tens of tonnes each day, distributed over the whole world.

Planet construction has not yet finished. However, this dust has been vaporized and has reacted with the gases of our air. It does not tell us what the material was like before it hit our atmosphere.

On occasion larger pieces arrive, and survive to reach the ground more or less in one piece, or at least as large fragments — meteorites. Sometimes those pieces are bits that have been knocked off the Moon, or other planets, such as Mars.

Most meteorites are made of the cosmic material. However, the heating and chemical changes that happened during their fiery passage through the atmosphere destroys important evidence, and then, sitting on the ground, in the weather, waiting for us to find them adds further contamination.

We do know however that some of them contain evidence of carbon compounds. Clearly, to get unadulterated material we need to go out into space to collect it. We have visited comets and asteroids. However, none of those gave us the primordial carbon compounds we seek.

Then came asteroid Bennu.

This asteroid first became of interest when we realized it might actually hit the Earth. It is a roughly octahedral-shaped object about 500 metres across, weighing almost 80 million tonnes.

However, what makes it really interesting is that it is really dark coloured. Could this be due to large concentrations of carbon compounds?

This is why on  Oct. 20, after orbiting the asteroid for about two years, studying the surface and selecting a landing site, the NASA spacecraft OSIRIS-Rex landed gently on Bennu, grabbed a sample of surface material and boosted off again.

The surface gravity of Bennu is so low it takes over seven minutes to fall 10 metres, so thrusters were used on the way down and on the way up.

The samples will be delivered back to Earth in 2023. There is a Canadian instrument on board. It is a high-precision laser altimeter, which will be used to create a 3D map of Bennu.

Images sent back so far show a starkly lit, rocky surface, not the sort of place you would, without prior knowledge, expect to find the raw materials of life.

  • After dark, Saturn and Jupiter lie low in the south
  • Mars is rising in the east.
  • Venus rises in the early hours.
  • Mercury lies low in the dawn glow.
  • The moon will be new on the 14th. 


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2 full moons in October

It was a dark and stormy night. The full moon stared through the scudding clouds and the bare tree branches.

It seems  in almost all the spooky movies on TV around Halloween, the moon is always full. Interestingly ,the moon is full on that night only once every 19 or so years, and when it does happen, it is always the second full moon that month.

Two full moons in the same month comes up every two or three years. This second full moon of the month is often referred to as a Blue Moon.

This is where the expression "Once in a Blue Moon" came from, referring to something that does not happen very often. However, this definition of a Blue Moon might not be correct. Apparently the 13th full moon in any given year is referred to as a Blue Moon.

The phases of the moon are caused by the changing arrangement of Sun, Earth and moon as the moon orbits the Earth.

A full moon happens when the Earth lies between the moon and Sun, and we see the moon lit with the light coming from behind us.

The complications in the timing of these events arise because Mother Nature does not seem to like whole numbers.

The interval between two consecutive full moons is 29.5306 days, and a year, the time the Earth takes to go around the Sun, is 365.25635 days.

This is why we have to have leap years, leap seconds and other adjustments to keep the date in step with the seasons. There are therefore 12.3687 lunar phase cycles in a year. 

Just as 13 fence posts in a line have 12 gaps between them, the time interval covered by 13 full moons is 354.3672 days. Therefore, if the first full moon of the year turns up early enough in the year, there will time for a 13th full moon before the year ends.

This can lead to a confusing situation. If the first full moon of the year occurs at 1 a.m. on Jan. 1 Eastern Standard Time, then that year will be a Blue Moon year for inhabitants of Ontario and points east.

However, in B.C. that moment will happen at 10 p.m. Pacific Standard Time on Dec. 31 the preceding year, so that year would have been a Blue Moon year for those in British Columbia.

This sort of confusion is why in science we use just one time zone. By international agreement it is Universal Time, the standard time at the Old Greenwich Observatory, in the U.K., located on the zero degrees of longitude meridian.

Compared with the size of the Earth, the moon is unusually large. This has often led to astronomers referring to the Earth-Moon combination as a double planet.

For example, Mars has two moons: Phobos and Deimos, both of which are tiny. One day, when we are standing on the surface of the red planet, looking up, we will see those moons as small, star-like objects.

The fact that the moon looms so large in our skies, and its phases are so obvious, led to it becoming the basis of our calendar, which is where the word month (moonth) comes from.

The problem of managing a lunar calendar based on 12.3687 lunar months for each orbit of the Earth around the Sun has led to abandonment of the moon as a calendar basis over much of the world.

However, the moon's presence in our daily and cultural life is more intimate than just something associated with the date. It has been associated with religious events for thousands of years.

Easter is celebrated on the first Sunday after the first full moon falling on or after the spring equinox.

In addition, think of the amount of classical, jazz and popular music where the moon is featured, or its widespread presence in poetry and art.

This helps explain why, on those stormy nights in those old, spooky movies, the moon is always there.

  • After dark, Saturn and Jupiter lie low in the south
  • Mars is rising in the east.
  • Venus rises in the early hours.
  • Mercury lies low in the dawn glow.
  • The moon reaches Last Quarter on the 8th. 


More Skywatching articles

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About the Author

Ken Tapping is an astronomer born in the U.K. He has been with the National Research Council since 1975 and moved to the Okanagan in 1990.  

He plays guitar with a couple of local jazz bands and has written weekly astronomy articles since 1992. 

Tapping has a doctorate from the University of Utrecht in The Netherlands.

[email protected]



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The views expressed are strictly those of the author and not necessarily those of Castanet. Castanet does not warrant the contents.

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