All posts by vidur

Astronomy Night observation for the coming weekend Sept. 2018

Dear All,

The monsoon the receding and the season for stargazing is about to start. I would like to propose a night observation on the upcoming weekend Sept 15 (Saturday) at a campsite near Tijara. Rajasthan. We have conducted three such observations here in the past and the sky has been very supportive combined with rural skies which gives a limiting magnitude of 5.5 visually. You are welcome to bring your family and friends to enjoy the fist stargazing of the season.

The place is located about 75 KM from gurgaon and 110 KM from delhi. It is located 10KM off the Delhi – Alwar highway which makes it an optimum place within the driving distance from Delhi NCR. In last 3 observations organised, there have been 25-30 members participating each time. Age group of participants have been between 13 and 85 years.

The weekend of September 15 will show Moon, 4 planets, summer milky way along with plenty of DSOs in the evening whereas late in the night, winter constellations will show up making it a perfect setting for stargazers. We may also get to see the fading comet 21P/Giacobini–Zinner as it will be at its closest and brightest tonight.

The venue, a campsite used by my company for astronomy observations for school kids is absolutely safe with boundary wall, dark skies, tented accommodations, evening and mid night snacks along with dinner and breakfast. Tea coffee shall be provided in the evening and near mid night for us to keep going. Tents are provided for people driving their own vehicle to snooze for a couple of hours so that they are well rested and can hit the road in the morning. All you need to do is to pay Rs 1,850/- per person to avail the facilities and enjoy the night sky.

The weather seems promising with clear skies over the weekend. Temperature is expected to be between 22 and 34 degrees. Warm clothes are advised to be carried for the night. Carry your telescopes, cameras, star maps and any other thing you may require to explore the night sky.

Those of you interested in joining me can contact me at +91-9560338860 or simply reply to this email with your confirmation.

Hope to see many of you next weekend.

Clear skies
Sneh Kesari

Talk at Planetarium

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”

Abstract:

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.

Amazing Picture of the Day 6/6/2016

courtesy: Wikimedia Commons
volcanic euruption on Io seen from NASA’s New Horizons probe

Check out Tvashtar volcano on Io seen spewing molten material into space, as seen from New Horizons probe in 2007. Io experiences massive tidal forces from Jupiter’s gravity and this kind of volcanic eruption is not uncommon for Jovian moons. For a sense of scale, the volcanic plume is about 330 Km in altitude. New Horizon was built by John Hopkins Applied Phyisics Lab for a mission to Pluto. This photo was taken when it flew past Jupiter for a slingshot course correction towards Pluto.

Tonight’s Sky: June 2016 – Saturn in Opposition

Saturn in Scorpius
Looking South 2131 IST
Summer is here and one cannot miss Saturn and Mars in the night sky. Looking south-east, Saturn is a stunning magnitude 0 star right now, appearing towards the west limb of Scorpius ( more in Ophiuchus ). Saturn hits opposition tonight so its really bright. Also its rings are tilted 26 degrees to us earthlings, which means that small telescopes can get a really good viewing including the famous gap in the rings called the Cassini division. Mars also hit opposition a few days back so both planets should make backyard astronomers and enthusiasts extremely happy

Now don’t just sit there and read this. Grab your gear and get out and have fun under the sky.

Frontiers of Space Flight Technology

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. De Laval Nozzle CFD, Courtesy flowsquare.com

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.

SpaceShuttleAtlantis
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
TPS1
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.

The X-37B Orbital Test Vehicle waits in the encapsulation cell of the Evolved Expendable Launch vehicle April 5, 2010, at the Astrotech facility in Titusville, Fla. Half of the Atlas V five-meter fairing is visible in the background. (Courtesy photo)
The X-37B Orbital Test Vehicle waits in the encapsulation cell of the Evolved Expendable Launch vehicle April 5, 2010, at the Astrotech facility in Titusville, Fla. Half of the Atlas V five-meter fairing is visible in the background. (Courtesy photo)

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

isro RLV liftoff
ISRO Reusable Launch Vehicle (HEX-1) Launch
ISRO RLV TD
ISRO Reusable Launch Vehicle Closeup

Gear Up for Perseids Meteor Shower

Mark your calendar

The perseids meteor shower peaks on Aug 13th 2015 this year. The best part is there is no moon this time to spoil the show. But wait we live in Delhi, there is always the rains .. which might get the gold medal for this year’s spoilsport, followed by smog which might manage to get a silver. Pfooey!!. Forget what I said. Good things happen to optimistic people. Get out there and enjoy nature’s finest light show.

For the un-initiated, the Perseid meteor shower originates from the debris field of Comet 109P/Swift Tuttle, which visited us in 1992 and will do so again in 2125 when it may potentially slam into us. Nah I am not losing sleep over it. I leave the worrying to the next generation.

Its expected that you might to get see 80 meteor per hr ( ZHR ), which is pretty good. Perseids are called so because they seem to radiate from the constellation Perseus. Hence the name. The radiant ( the imaginary point where the meteors shoot out from ) of the Perseid meteor shower is at around right ascension 02h20m, declination +58°, All of the meteors will appear to be traveling directly outward from this point. The best place to look to see as many meteors as possible is not at the radiant itself, but at any dark patch of sky which is around 90° away from it, since it is at a distance of around 90° from the radiant that meteors will typically appear at their brightest.

courtesy: sky and telescope
courtesy: sky and telescope

Observing Tips

1- Keep warm clothes and waterproofed clothing with you, it does get somewhat cold and damp at night
2- Keep company. Showers can sometimes not be too active as predicted. Its nice to have someone around to chat to till then
3- Contribute. You can time meteors and report them to IMO.
4- Observe from a safe and rural location if possible. City lights almost ruin everything.