Monday, December 29, 2008

Water rockets!

Well, I was wondering how could water under pressurised condition(yeah, i know liquids are incompressible) ever propel a rocket! That was when i first saw the problem statement of the ROCKETRY event of Kurukshetra '08 and decided this is not for me! Now when I look into this field, I'm really amazed by the amount of physics involved with water rockets(or bottle rockets)!

Now that i'm so impressed by the working of water rockets, i'm determined to post a small article on it!

  • A 2-litre used coke [or whatever] bottle
  • A hacksaw
  • A compressor(To pump air)
  • Any ligth weight material to make the nose and fins(The same plastic from which the bottle is made would do well)
Now, I dont wat to give step by step instructions to construct the rocket. Instead I'll scatter few pictures. Being a "Techy" person you could grasp the details from these pics. ;-)

The nose and fin setup is just enough for you to get an insight into the construction. And yeah, about the nozzle setup, as I've not yet built a water rocket myself, I'm not sure about that part. Depending on the type of compressor or pump you use, you can have your nozzle set up in the corresponding style.

Now, lets get into my favourite part - how it works! ;-)
I always like KISS - Keep It Short and Simple :P. So, let me keep it short. The major parameters on which the working of the rocket depends are (i) Pressure inside the chamber, (ii) Diameter of the nozzle, (iii) Quantity of water inside the bottle. And yeah, the flight of the rocket also depends on the weight of the bottle used and the alignment of fins.

The Pressure:
The pressure determines the stored energy inside the bottle which in turn determines the thrust developed. As water is incompressible, energy is not transferred to it. It is stored only in the compressed air. The launch pressure may vary with the size and the type of bottle used. It may be between 500 kPa to 1000 kPa.

The Nozzle:
The nozzle may be the standard soft-drink bottle's one with an approximate diameter of 22mm. Or it may be of a reduced size - 9mm diameter approx. The size of the nozzle affects the thrust produced by the rocket. Larger diameter nozzles provide faster acceleration with a shorter thrust phase, while smaller nozzles provide lower acceleration with a longer thrust phase.
Quantity of Water:
The quantity of water is a very important parameter. It determines the duration of the thrust phase. Mathematically, the ratio of the volumes water and air in the bottle for maximum efficiency is 1:2. For an efficient flight, the thrust should be in three phases. In the first phase, the exhaust is completely water. This flow must be laminar for maximum thrust. In the second phase, the amount of water would have been reduced. So the exhaust consist of both air and water and the flow will be turbulent. This will be seen as a spray of water particles from the nozzle. The last thrust phase consists of exhaust of air.

The above picture shows the laminar and turbulent flow phases clearly.

Well, this is all I've read about water rockets till now. There are still a lot of technicalities associated with water rockets. And now its your turn to build and launch your own rocket. Happy Launchin'! :-)

Friday, December 26, 2008

Kurukshetra '09

At last I'm into what i had been wanting to do for a long time - Technical writing[or simply writing about technical stuff :P]! And whats better than Kurukshetra to start with! Kurukshetra is the International Techno Management Festival of CEG. It attracts more than 15,000 participants from various countries. Last year's version was a huge success and this year it is expected to be bigger and better!

THE MAJOR EVENTS [The ones I like :D]

XCEED - The Xceed challenge, this year, comprises of Robotics events. One is the usual Line Tracer event and the other the most engaging Robo Soccer. Comprising of one autonomous and one manual event, Xceed is gonna be conducted at three centres - Pune, Bangalore and Hyderabad.

DALAL BULL - This is one of the much awaited events of Kurukshetra '09. Its nothing but a simulation of the stock market. The online version of this game has already started. Check out the Kurukshetra '09 website for details. The onsite event willl span over three days during the fest.

ROCKETRY - Build a multi-stage rocket propelled by used cola bottles[Plastic ones ofcourse!] - as simple as that! But when I started looking out for info on building a water rocket, I was simply taken aback by the technicalities involved in this field! I'll be soon writing an article on water rockets.

The things given above are just drops from the ocean of Kurukshetra '09. Visit and get the real taste of it!

Awaiting the battle of brains to begin!