ISRO Interview Experiences | Mechanical

ISRO  Interview Details

•  The panel consists of 5-10  senior scientists, IIT faculties etc. 

• They may ask you to choose your top 3-5 favourite questions. They may or may not ask questions from your favourite subjects. 

• You need to give a full explanation of every question/topic asked. 

• Be familiarized with Blackboard teaching as you may have to explain on the blackboard. 

• They may ask you about your B.Tech final year project. But It completely depends on them. 

• For M.Tech students prepare well the M.Tech thesis topic. 

• Reach the interview venue before time. 

• Check all documents, a day in advance. 

• Don’t forget to keep a pen with you in the interview room.

ISRO interview Experience

4 Aug 2018 at delhi

After a brief introduction, they asked my fav. Sub they are as follows HT, MD, FM, Thermo

1. What is max stress in a bar which is hanging vertically?

2. If I want to design this bar what will be the min length I should take?

3. If I put the whole system in water then whether the length increase or decrease?

4. How many laws of thermodynamics u know? What is the first law of thermodynamics?

5. Draw adiabatic process on pv chart?

6. What are the conditions of the adiabatic process?

7. Derive $PV^{\gamma} = c$ ?

8. Draw two stage and one stage compressor?

9. What is intercooler? What amount of work has been saved by intercooling?

10. What if I do aftercooling ( means one more intercooler after 2nd stage)

11. I want to manufacture the glass (pointing glass present in front of interviewer) so draw a drawing of glass?

12. Then they asked last q. From one of my extracurricular activities, in that I attended workshop on rubber powered aircraft so they ask what is it?

NAME- Rajat Kumar Singh (AIR-1, ISRO, MECHANICAL-2017)

Venue- New Delhi
Interview reporting time: 8 AM
Interview happened at: 12:25 PM
DATE: 22 Sep 2017

There were 9-10 people including one female member sitting around U shaped table.

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?
Me -DRAWN

M2- what if there is external pressure and no internal fluid?
Me- drawn.
M2- good

M3- draw one cantilever with a point load at one end. Tell me the deflection at the 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?
Me-4/3 sir.

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
smiled).
(i was thinking inko bhukh ni lagi kya :p)

M6- if I give you perimeter= 12 m can you find the dimensions for the maximum area?

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 a 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.

ISRO Mechanical interview on 24th Dec at SAC Ahmedabad 

Panel 8 persons( 7M + 1F)

After introduction chairman asked me favourite subjects and I replied SOM TOM MD and HMT Power Plant and then a rapid fire round of 30 minutes started

1. Define degree of freedom for a mechanism. What is the degree of freedom in space and plane?

2. What is Grubler’s formula to find dof of mechanism?

3. Draw a mechanism having all revolute pairs with 5 links and find dof.

4. Then in the same mechanism he told me to fix another link and asked what will be effect on dof?

5. What is redundant link and redundant dof?

6. Name different types of gears

7. Comparison between involute and cycloidal profile.

8. Draw tooth geometry and show pressure angle.

9. What is contact ratio?

10. What is path of contact and show when there will be first contact between teeth of gears?

The session of TOM was about to end but then chairman told that you have classified all types of gears but forgot one i.e. epicyclic gear train. I think he wanted me to also show internal gearing.

11. Draw epicyclic gear train and find dof.

12. Draw universal joint. Does the velocity ratio in universal joint remain constant or vary? If varies then write formula and show variation of velocity ratio with angular position of shafts.

Then some questions from Heat Transfe:

13. Suppose a cuboid in furnace at 300°C is brought suddenly to room temperature then write governing differential equation and show temperature variation with time.

14. I drew exponential decreasing curve and he was asking why curve is not touching room temp. line why it is going to infinity?

So this was a short session of Heat Transfer and then suddenly an interviewer asked

15. What is balancing and types.
16. Tell me the necessary condition for a rotating disk to be balanced.

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