Previously at HAS...

short summaries of our past society meetings

 


 

Tuesday 1st November 2016: "To Orbit and Back, Again and Again" - Arthur Milnes (HAS)

 

 

 

 

 

 

 

 

Arthur’s talk was about the Space Shuttle, the only reusable spaceship capable of taking human beings and cargo into near space, orbiting the Earth before returning safely, and then doing it all over again.

How did the Shuttle come to be built and prove to be so successful?

The space race began when Russia beat the Americans to the launch of the first satellite – Sputnik in 1957. NASA was born the year after. The Mercury and Gemini missions paved the way to developing the giant Saturn V (see above) and the technology to launch its starting weight of 2,950 tons into Earth’s atmosphere and to accelerate 45 tons of that rocket to a speed of 24,000 miles an hour to escape Earth’s gravitation pull. It stood 363 feet tall and had five huge engines generating a total of 3,750 tons of thrust.

Columbia was the first Shuttle, and it flew from Florida on the 12th April 1981. The whole assembly weighed 2,200 tons and stood 184 feet above the launch platform. The largest section of the tank was the hydrogen container holding 115 tons of liquid hydrogen; the smaller section of the tank contained 692 tons of liquid oxygen. The tank was jettisoned after the fuel had been used and burnt up during re-entry, the only non-reusable component of the Shuttle.

The Solid Rocket Boosters are unstoppable once lit. They will burn for two minutes providing 70% of the thrust required to propel the Shuttle to 24 miles above the Earth. The boosters were built from an incredibly strong steel tube in four main sections and when put together with 177 one inch steel bolts, measured 149 feet in length and 12 feet in diameter. The bolts had to withstand pressures of between 13 and 17 million pounds trying to blow the joint apart.

These boosters could control the direction of their exhaust blast, allowing them to rotate the Shuttle onto its back to take up orbit trajectory. After two minutes and at a height of about 24 miles, the boosters separated from the Shuttle continuing upwards on a ballistic path to 36 miles before falling into the Atlantic to be recovered, refurbished and reused.

Four Shuttles were built initially: Columbia, Challenger, Discovery, Atlantis, all named after famous American ships. After Challenger was lost, Endeavour was built as a replacement.

They were 122 feet long, had a wingspan of 78 feet and weighed 110 tons. They were designed to each fly 100 missions, but none did. The missions were designated STS followed by a number - STS stood for Space Transport System. Each one flew a distance equal to a flight from Earth to Mars. Even with the huge push of the solid rocket boosters, more thrust was required to take the Shuttle to a speed of 17,500 mph so it could escape Earth’s gravity.

The extra push was provided by the Shuttle’s main engines, which consisted of three large engines each producing a thrust of 156 tons that was controllable, vitally important for a safe flight. They could be throttled back to about 65% of power as the Shuttle accelerated through the sound barrier to reduce structural stresses from shock waves, and then could be throttled back up to 104% as the Shuttle climbed into thinner air. The Shuttle carried 46 smaller engines to help it to manoeuvre in space and glide back to Earth. There were two orbital manoeuvering system rockets, 16 smaller reaction control system rockets at the front and 28 of them at the rear. The 44 reaction control system engines were fired in short bursts to manoeuvre the Shuttle to successfully dock with the ISS.

The two orbital manoeuvering system engines were each capable of 6,000 pounds of thrust and were used to achieve final orbit and when boosting the ISS to a higher orbit. They also came into play to slow the Shuttle down so it could begin its descent. It had been flying upside down so the thrusters turned it 180 degrees so its 20,000 thermal protective system tiles covering the Shuttle met the atmosphere first to prevent it from burning up during re-entry.

There were disasters and some near disasters with plenty of heart stopping moments in the story of the Space Shuttle, but to complete the tale Arthur thought he would probably need another 50 minutes and, if we were willing, he would give us a further insight into this remarkable vehicle at a later date.

 


 

Tuesday 4th October 2016: "Is the Pale Blue Dot Special?" - Dr. Duncan Forgan

Duncan, a research fellow at the University of St. Andrews and founding member of SETI, began by asking if our planet is ordinary or unique, and wondered if Earth could be the only inhabited planet and the only place with intelligent life.

If there are alien societies out there, why haven’t we encountered them, considering it should be possible for them to have spread across our Galaxy within ten million years?

Drake’s equation suggests there are many planets around many stars that could support life, so there should be intelligent civilisations out there.

When looking for life elsewhere, a good place to start is to study known extrasolar planets – planets orbiting other stars.

The first was discovered over 20 years ago by the Doppler shift (radial velocity), when scientists look for a tiny wobble of a star caused by an orbiting planet.

There are now various other ways to detect extrasolar planets, including the transit method used by the Kepler spacecraft, which looks for a tiny dip in the light of a star caused by an orbiting planet. This method can also detect an atmosphere – if it exists.

As of the 1st October 2016, 3,532 confirmed exoplanets have been found orbiting 2,649 stars. Some of these are believed to be rocky, but we need to be able to sort out the Venus’s from the Earths – these solar system planets are the same size and each have an atmosphere, but only one is habitable.

Numerous new ways of searching for alien life will be possible in the future using various telescopes on Earth and in space. At the moment we can use radio telescopes to search for radio signals from space, including the large telescope at Aricebo which SETI uses.

Other ideas to look for intelligent civilisations include searching for laser light – one powerful enough could be seen from Earth. We could use infrared light to look for giant structures; there is one exoplanet with what appears to be debris around it and one thought suggests we are actually looking at alien structures.

However, at the moment, our solar system is not really represented anywhere as we are, as yet, unable to detect small planets. The only true Earth-like planet that we know is Earth itself. Duncan finished by saying the search for another pale blue dot is actually the search for ourselves.Duncan began by asking if our planet is ordinary or unique, and wondered if Earth could be the only inhabited planet and the only place with intelligent life.

If there are alien societies out there, why haven’t we encountered them, considering it should be possible for them to have spread across our Galaxy within ten million years?

Drake’s equation suggests there are many planets around many stars that could support life, so there should be intelligent civilisations out there.

When looking for life elsewhere, a good place to start is to study known extrasolar planets – planets orbiting other stars.

The first was discovered over 20 years ago by the Doppler shift (radial velocity), when scientists look for a tiny wobble of a star caused by an orbiting planet.

There are now various other ways to detect extrasolar planets, including the transit method used by the Kepler spacecraft, which looks for a tiny dip in the light of a star caused by an orbiting planet. This method can also detect an atmosphere – if it exists.

As of the 1st October 2016, 3,532 confirmed exoplanets have been found orbiting 2,649 stars. Some of these are believed to be rocky, but we need to be able to sort out the Venus’s from the Earths – these solar system planets are the same size and each have an atmosphere, but only one is habitable.

Numerous new ways of searching for alien life will be possible in the future using various telescopes on Earth and in space. At the moment we can use radio telescopes to search for radio signals from space, including the large telescope at Aricebo which SETI uses.

Other ideas to look for intelligent civilisations include searching for laser light – one powerful enough could be seen from Earth. We could use infrared light to look for giant structures; there is one exoplanet with what appears to be debris around it and one thought suggests we are actually looking at alien structures.

However, at the moment, our solar system is not really represented anywhere as we are, as yet, unable to detect small planets. The only true Earth-like planet that we know is Earth itself. Duncan finished by saying the search for another pale blue dot is actually the search for ourselves.

 


 

Tuesday 6th September 2016: "Aurora, in search of the Northern Lights" - Dr. Melanie Windridge

Melanie combined her love of exploration with studying the aurora and her book is about her travels through the auroral zone, meeting the people who live in there, listening to their experiences as well as discovering the science behind the aurora.

  • The aurora is an incredible, beautiful light show to watch, but it is also so much more than that – the aurora is a plasma. Plasma is the 4th state of matter – an ionised gas made up of charged particles.
  • The Earth’s magnetic field is like a bar magnet, and it protects us from the solar wind, which is also made up of charged particles. The Sun is very dynamic and will sometimes hurl out huge lumps of ionised gas outwards with masses of up to a billion tons! On occasions these Coronal Mass Ejections are directed towards the Earth.
  • Charged particles do find their way into the Earth’s magnetosphere on the day side of the Earth, but in order for us to see the aurora at night they must be coming from behind the Earth. Somehow the particles are being accelerated into the night side of our atmosphere.
  • Magnetic field lines cannot cross each other. The Sun’s field and the Earth’s field can connect (Sun’s field with the Earth’s field), but in so doing, they provide an opening for charged particles to enter – like a door. Then the field lines are pushed around to the back until the Earth’s field lines reconnect in the magnetotail, which is now full of charged particles. This closes the door.

 

JSL ObservatoryNext Observing Session

Public & Members

Sat 25th Feb
20:00 - 22:00

STATUS: CANCELLED. Cloud and rain...