ISRO Mechanical Interview Experience by Rajat Kumar Singh is shared here. Rajat gave interview in September 2017 and accepted the offer. Please feel free to contact him for details and questions if you have any at his facebook (Rajat Kumar Singh).
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The interview details are as follows.
NAME- Rajat Kumar Singh
Venue- New Delhi
Interview reporting time: 8 AM
Interview happened at: 12:25 PM
DATE: 22 Sep 2017
After filling some forms we all aspirants were made to sit in a conference hall. Slowly one by one people were called for interview. My turn came after 4 long hours. I was the last person to be called before lunch. We were told not to carry certificate folder in the interview room.There were 9-10 people including one female member sitting around U shaped table.Upon entering I was asked to sit on a chair near the whiteboard.
Chairman- good afternoon. Please introduce yourself.
Me- good afternoon mam and sirs. My name is Rajat Kumar Singh, I told them about my schooling, college,etc..(it was very short introduction). And my areas of interests are ENGG. MECHANICS, SOM, HMT, FLUID MECHANICS and MACHINE DESIGN.
(actually,i was not fully prepared for machine design so slowly told “machine design”)
M1- what is your last subject?
Me – sir Machine design.
(i thought ab to gya mai)
M1- ok rajat, what is fail-safe approach?
Me- after 3-4 second, sir it is an approach in designing, we design our system or machine in such a way that there is minimal loss in terms of money and safety. For example, in the design of shaft and key, we make our key weakest member. In boiler design also we provide safety valve so that in case of overpressure our boiler will be safe.
M2- Take a marker and draw a thick cylinder.
Me- i made two concentric circles.
M2- how will you classify thin and thick cylinders?
Me- sir if the wall thickness is less than about 7% of internal diameter we treat it as thin otherwise thick.
M2- okay, draw one more cylinder over it and there is fluid inside it. Tell me how will hoop stress vary for both cylinders?
M2- what if there is external pressure and no internal fluid?
M3- dwaw one cantilever with point load at one end. Tell me the deflection at free end.
Me: (trying to impress, started deriving the formula)
M3- just tell me the formula
Me- WL^3/(3 EI)
M3- cut it in two pieces and tell me about shear forces at different points.
Me- drawn two half beams and showed the shear forces.
M3- draw its shear force and bending moment diagram
Me- drawn easily.
M3- how will shear stress vary?
Me- drawn transverse shear stress variation.(D shaped)
M3- what is the relation between average and maximum shear stress?
Me- 3/2 times of average.
M3-What if beam is circular?
M4- there is a rectangular beam hanging with a cable on a crane. The weight of beam is 10 tonnes. Angle b/w cables is 60 degree. What will be tension in the cable?
Me-(drawn) suppose weight is uniformly distributed then at each ends weight is 5 tonnes each. Applied force balance and calculated tensions easily.
M5- do you know projectile motion?
Me- yes sir.
M5- at what angle the range is maximum?
Me- at 45-degree sir(smiled)
M5- write rigid body equation of motion?
Me- d(m*v)/dt = F (i don’t know it was right or wrong but they
(i was thinking inko bhukh ni lagi kya :p)
M6- if i give you perimeter= 12 m can you find the dimensions for maximum area?
Me- it was easy.
got the answer.
Female member(F)- rajat i think you are tired now take a seat.
Me – thank you mam.
F- we will ask something related to ISRO. Do you know what was last mission all about?
Me- mam it was the launch of PSLV C39. India is developing its own GPS, for that we already sent 7 satellites but mam there was some problem in one of the satellites. So we were replacing that satellite with newer one. This mission was unsuccessful because heat shield did not separate.
F- what is heat shield?
Me-this is like a cover for our payload. Due to air resistance, surface temperature increases enormously. To protect our payload we use heat shield.
F- we are done now. Thank you.
Me- thank you mam
(everyone was smiling, a big sign of relief at that moment)
My interview went for about 35-40 minutes. This was purely technical.
The main thing is if you are not very well prepared don’t be nervous. In introduction only tell them about your favorite subjects. They didn’t ask about my project. I answered almost everything but if u don’t know the answer tell them directly.
I got 83.11 in the final result.
RAJAT KUMAR SINGH
AIR-1, ISRO, MECHANICAL-2017
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Wish Rajat and all of your great luck ahead.