Vigyan Prasar in association with Nehru Planetarium is organizing popular lecture at 10:00 AM tomorrow 23 August 2016 at Sky theater at planetarium. Interested people can join the programme.
The Speaker: Akshat Singhal,
Marie-Curie Fellow – Europe’s most competitive and prestigious awards, Early Stage Researcher (ESR) fellowship within the project Grawiton – European Marie Curie Action INT at Gran Sasso Science Institute in L’Aquila, Italy.
Title of Talk: “The sound of black holes”
Recently mankind has detected first gravitational waves as predicted by Albert Einstein 100 years with his theory of General Relativity. This discovery was considered as one of important discovery in the centuary. One of the most challenging experiment physicists ever undertook, measuring the change in length smaller than 1/1000th of a diameter of proton over 4km. We will discuss how many challenges are overcome and how did we achieve this endeavor.
Human beings have been launching spacecraft since World War 2. Rocketry, in principle has not changed much from the early days of rocketry in ancient China to Von Braun who invented the worlds first rockets like the V-2 capable of sub-orbital flight and atmospheric reentry. Chemical rockets are rather simple in concept. A generally explosive fuel + oxidizer mixture forms the propellant, which is burnt in a controlled fashion in a reaction chamber. The hot gases exit a nozzle providing a large amount of thrust to the rocket.
Since then we’ve done several fancy things to a rocket. We’ve put a space capsule on the top, making it possible for man to travel out of earth’s orbit. We’ve attached airplanes to the rocket body which we lovingly knew as a space shuttle. Space shuttles were not a NASA creation alone. The Soviet Union created its own version of the space shuttle called ‘Buran’. Buran completed one unmanned spaceflight in 1988 which was an unmanned test flight. The program ended shortly due to budget cuts arising from the collapse of the Soviet Union. NASA’s space shuttle programme was however the successful and ambitious effort in human spaceflight till date.
NASA’s Space Shuttle Atlantis
Soviet Buran Orbitter
The space shuttle was a a marvelous piece of engineering. Not only it put humans in orbit. It also had a massive payload capacity. Powered by two giant solid booster rockets and cyogenic engines, the shuttle could lift a total payload mass of 27 tonnes to low earth orbit. The shuttle programme also pushed the frontiers of spacecraft reentry technology. The shuttle on atmospheric reentry slams into the atmosphere at a speed in excess of Mach 25. For the new reader thats 25 times the speed of sound or 8.7 Km/s. Normally for small objects, the reentry shield is a carbon-ablative material. Ablative materials were used by early spacecraft like Apollo and Gemini programmes. They are also used in ballistic missile payloads. In simple talk these are shields made out of carbon. As the material heats up, it slowly burns off, keeping the payload relatively cool. However these things are difficult to fabricate for larger objects. Another problem with the ablation system was that once the temperature fell in a zone where shielding was needed but low enough to prevent the ablation, they would cease to function making them somewhat unreliable.
The space shuttle introduced a different type of heat shielding. This strategy is called “thermal soak”, where the shield has an enormous capacity to trap heat. You could heat the substance to over a 1000 degrees in one end, and still hold it with your fingers at the other Super Insulators like this ceramic cube is red hot inside, but cool enough to be lifted by bare hands
This strategy is wildly popular and used by all space programs. However there have been issues with tiles in how they are integrated onto the spacecraft. The ceramics are usually brittle and many times have caused serious problems. The Columbia space shuttle disaster in 2003 is a typical example where a piece of insulating foam from the main external tank hit the leading edge of the shuttle’s wing, destroying some of the tiles. This was enough to cause the orbiter to burn up during atmospheric reentry and instantly kill the crew. Losing a few tiles had been a common occurrence on previous shuttle missions too, the risk associated with losing this critical thermal protection was well known too. However since then NASA has taken a lot of measures to ensure that such accidents would not happen on future missions.
In recent years, space programs have had to face major budgetary cuts all over the world. NASA’s budget fell from 1% of US GDP to approximately 0.5% of the GDP. For comparison this number was about 4.4% at the peak of the Cold War. The Russian space program has also seen similar cuts for a variety of reasons, both political and economical. In times of financial crisis governments usually trim funding for space programs. For mankind’s space ambition to survive, it could no longer afford to be a drain on large amounts of cash. So a concept of reusable launch vehicles was conceived. Bulk of the spaceflight industry comprises of launch systems that put satellites in orbit. It made sense, if we could find a way to do it cheaper and faster.
RLV technology is not that novel. The US operates unmanned spacecraft routinely. The X-37 is a reusable unmanned spacecraft that is boosted into orbit by chemical rockets, but lands back on the ground like a conventional plane.
One of the biggest pioneers of reusable technology is South African capitalist, Elon Musk’s SpaceX Corporation. SpaceX has been able to make significant strides in space technology in a rather small amount of time. In the man’s own words
“If one can figure out how to effectively reuse rockets just like airplanes, the cost of access to space will be reduced by as much as a factor of a hundred. A fully reusable vehicle has never been done before. That really is the fundamental breakthrough needed to revolutionize access to space”
This is no longer science fiction. In April 2016, the first stage of a Falcon-9 spacecraft landed safely on an offshore barge. This was after one year of hard work and four other failed attempts. I put this video below, and I must admit, it is pretty darn cool. According to SpaceX lot of work still needs to be done to make this technology reliable, but there is no doubt that it is a game changer in the space industry.
Recently India has also been working on a RLV program. Earlier it was code named “AVATAR” which was a RLV concept that used scramjet propulsion. AVATAR stood for “Aerobic Vehicle for Transatmospheric Hypersonic Aerospace TrAnspoRtation”. Since then it has evolved into what is now called the RLV-TD project. ISRO has staged its RLV program in small steps. The first of this was the HEX or Hypersonic Flight Experiment was performed earlier this month in 2016. The experiement was designed to validate flight performance of the spaceplane at Mach 6. The plane itself was boosted into Mach 6 speed by a sounding rocket booster and had no propulsion. In the future flights, it will feature a scramjet engine. The hope is that ISRO’s RLV will be used to deploy small satellites into LEO and return back to earth
The recent 2011 earthquake in Japan demonstrated that nature can strike a havoc in our lives without warning and with devastating consequences. Similarly India also faces annual natural disasters like monsoon flooding, cyclones, land slides etc that occur routinely every year and also relatively rare events like industrial disasters, massive earthquakes and tsunamis like the one that happened in 2004. It is never too late to be prepared for such an emergency however unlikely it may seem to happen.
The first thing you need to do is to estimate all the possible disasters you may be vulnerable to. People living in coastal locations of India are always vulnerable to floods and cyclones in the rainy season. People in the Himalayan and Deccan plateau are exposed to a significant risk of earthquakes and landslides. If you live near Nuclear or chemical plants, you may be vulnerable to what is called Nuclear-Biological-Chemical threats. Identifying the correct threat will help you in planning appropriately for an emenrgency. Sometimes there are more than one type of risks that may be applicable to you.
Get a Kit
You may need to survive on your own after an emergency. This means having your own food, water, and other supplies in sufficient quantity to last for at least three days. Local officials and relief workers will be on the scene after a disaster, but they cannot reach everyone immediately. You could get help in hours, or it might take days. In addition, basic services such as electricity, gas, water, sewage treatment, and telephones may be cut off for days, or even a week or longer.
Some of the things you can keep for any kind of emergency
Water for 3 days, both for phyisical consumption and sanitary purposes. A large jerry cane is a convenient way to hold water
Three day supply of non-perishable food. Sealed ready to eat food or canned food is a good starting place
Can opener if you are packing canned food
Sanitation Supplies: try keeping disinfectants and a soap bar handy
A First Aid kit
Flashlight and batteries. Please make sure batteries are stored seperately and not left inside the flashlight during storage.
It is best to keep these items stored in a convenient location in a small duffel bag, so that you do not waste time locating these things in an emergency.
Nuclear Radiation Fallout
There are three things you need to keep in mind during a nuclear radiation leak incident. Such a disaster may happen due to an accident, terrorism or warfare. To minimize exposure to radiation
Maximize distance between you and the source. The more distance between you and the source, the better it is. This could also mean evacuation or taking shelter indoors
Shielding: The more heavy dense material between you and the source, the better. A concrete structure will provide more protection than a wooden house
Timing: Most radioactivity loses its strength fairly quickly. this does not apply if the source that is emitting radiation has not been contained
Cancer Protection in the Event of a Nuclear Emergency
In 1982, US FDA approved the use of potassium iodide as a means to protect the thyroid gland from radiation poisoning due to nuclear plant emergencies. Radioactive iodine is the most common radioactive material released from fission products, which attacks the thyroid gland causing Thyroid cancer. By overwhelming the thyroid with a “stable isotope” of potassium iodide (KI), the body will not try to absorb the radioactive version.
For people over 12 years old, a 130 mg per day dose of KI is recommended by WHO. For detailed information CLICK HERE
Some known brands for thyroid protection are IOSAT, THYROSAFE (available on ebay.in when I last checked)
Note: KI only protects against thyroid cancer, it doesnt give any protection against other radioactive materials and dirty-bomb products that produce radionuclides rather than nucleoisotopes.
Note: Please DO NOT use iodized salt as a source of iodine in such cases. You may have to eat bucket loads of salt to get the required dosage of Iodine, which would probably kill you instantaneously
Solar Flares are classified according to the amount of energy emitted by them per unit area. The classification is based on the energy released in the 1-8 Angstrom band.
Typically we have 4 major classes designated by letters B,C,M and X, with X being the most powerful of flares. Each of these letter classes is further subdivided into 9 subdivisions. So a X class flare can exist from X1 to X9, with X9 being the strongest flare.
The silence and boredom has ended. It seems that the yellow ball in the sky has decided to show that its not dead yet. After an unusually long hiatus, a large sunspot group just below the solar equator has formed. The spots recently released an M6 class solar Flare on Feb 13th at about 1738 UTC. This was followed up today by a X2 class flare released on Feb 15th on 0156UTC. Both flares have ejecta (coronal mass ejection) hurling towards earth, triggering geomagnetic storms over the polar regions of our planet.
X-Ray emission data from SOHO-CELIAS instrument, Wavelength from 1 t0 500 Angstrom
The flare originated from the sunspot group designated 1158. Astronomers predict that this feature on the sun isn’t done yet and there may be more fireworks soon. Besides the pretty auroras, flares like these can be annoying too. Strong flares have known to cause problems in power transmission lines, destroying sensitive electronics on board satellites and deep space missions.
19.02.2011: Another M Class Eruption, There is 75% chance of more outbursts soon