Go Back   Team-BHP > Around the Corner > Shifting gears


Reply
 
Thread Tools Search this Thread
Old 26th January 2013, 13:26   #61
PGA
BHPian
 
Join Date: Apr 2012
Location: Ludhiana
Posts: 122
Thanked: 130 Times
Default

Thanks a lot for this exposition. I haven't had the time to go through it in detail coz I have been on the move for last couple of days and will remain so till about 10 Feb. But undoubtedly it is a great effort and and express my gratitude that you did to explain it to me.
Will revert back to you.
Cheers for the republic today
PGA is offline   Reply With Quote
Old 26th January 2013, 13:56   #62
Senior - BHPian
 
R2D2's Avatar
 
Join Date: Oct 2008
Location: Punya Nagari
Posts: 1,670
Thanked: 789 Times
Default Re: About Rocket Science & Engines

Great thread for us mortals As a sci-fi fan I find this thread very interesting.
R2D2 is offline   Reply With Quote
Old 28th January 2013, 12:49   #63
BHPian
 
CLIX's Avatar
 
Join Date: May 2012
Location: Bangalore
Posts: 121
Thanked: 85 Times
Default Re: About Rocket Science & Engines

Very interesting AlphaKilo.

I have a question : Is it right for me to infer from some of the theories presented, that; the Earth's velocity around the the sun varies based on the point of the ellipse (orbit) it is on. Getting faster when it is moving towards the sun; getting slower as it moves away. Slowest at Apogee; Fastest at Perigee.
??

Last edited by CLIX : 28th January 2013 at 12:51.
CLIX is offline   Reply With Quote
Old 28th January 2013, 18:45   #64
BHPian
 
AlphaKilo's Avatar
 
Join Date: Nov 2010
Location: VOMM-EDDW-EDDM
Posts: 773
Thanked: 362 Times
Default Re: About Rocket Science & Engines

Quote:
Originally Posted by CLIX View Post
Very interesting AlphaKilo.

I have a question : Is it right for me to infer from some of the theories presented, that; the Earth's velocity around the the sun varies based on the point of the ellipse (orbit) it is on. Getting faster when it is moving towards the sun; getting slower as it moves away. Slowest at Apogee; Fastest at Perigee.
??
Very precisely inferred. yes, it does and so does the inclination. The reason why Europe or artic countries have long days in summer and very short days in winter! The 11° inclination of the earth causes the incidence angle of the sun vary between summer and winter. Long days - sun above the equatorial plane, short days - sun below the equatorial plane.

For us south-indians, since we are just 8-9° from the equator don't see much of a difference whereas the northies and further up see a difference.

Edit: Thank you for your kind encouragment guys. I am flattered. As promised I will continue soon with interstellar/interplanetary navigation. Untill, questions/discussions are most welcome.
AlphaKilo is offline   Reply With Quote
Old 31st January 2013, 13:17   #65
BHPian
 
AlphaKilo's Avatar
 
Join Date: Nov 2010
Location: VOMM-EDDW-EDDM
Posts: 773
Thanked: 362 Times
Default Re: About Rocket Science & Engines

Question Hour:

For all those who had been following this thread, here comes the first question:

1. Read the text in the following link carefully and can you find out which orbit (LEO/MEO/GEO/GTO) is being referred here to?

http://www.thehindu.com/sci-tech/sci...cle4364325.ece

Let's see how many have concentrated in the class properly !
AlphaKilo is offline   Reply With Quote
Old 31st January 2013, 13:23   #66
Senior - BHPian
 
sagarpadaki's Avatar
 
Join Date: May 2010
Location: Bengaluru
Posts: 2,608
Thanked: 1,210 Times
Default Re: About Rocket Science & Engines

That would be a Geostationary orbit, since the article says 22,300 miles which is ~~ 36000 kms
sagarpadaki is offline   Reply With Quote
Old 31st January 2013, 13:30   #67
BHPian
 
AlphaKilo's Avatar
 
Join Date: Nov 2010
Location: VOMM-EDDW-EDDM
Posts: 773
Thanked: 362 Times
Default Re: About Rocket Science & Engines

Quote:
Originally Posted by sagarpadaki View Post
That would be a Geostationary orbit, since the article says 22,300 miles which is ~~ 36000 kms
That was a real quick reply mate! Good job. Happy to know one concentrated

P.S: Well, as promised the interstellar/planetary navigation will come up this weekend.
AlphaKilo is offline   Reply With Quote
Old 31st January 2013, 14:31   #68
BHPian
 
CLIX's Avatar
 
Join Date: May 2012
Location: Bangalore
Posts: 121
Thanked: 85 Times
Default Re: About Rocket Science & Engines

Yet another question!... May be partially off topic.

When there is a large earth quake like may be the one in Indonesia that caused the Tsunami havoc, I would think the earth could "wobble" in its orbit causing minor changes in the orbit; minor changes in the duration of the rotation; minor changes in the duration of the revolution.
Is that possible? Or should I just mind my own business; leave the earth alone?
CLIX is offline   Reply With Quote
Old 31st January 2013, 15:09   #69
Senior - BHPian
 
Join Date: Oct 2008
Location: Bangalore
Posts: 1,085
Thanked: 583 Times
Default Re: About Rocket Science & Engines

Quote:
Originally Posted by CLIX View Post
Yet another question!... May be partially off topic.

When there is a large earth quake like may be the one in Indonesia that caused the Tsunami havoc, I would think the earth could "wobble" in its orbit causing minor changes in the orbit; minor changes in the duration of the rotation; minor changes in the duration of the revolution.
Is that possible? Or should I just mind my own business; leave the earth alone?
It wouldn't really cause a change in the earth's orbit around the sun (only external forces can do that) - But it would certainly have affected its rotation around its own axis to some extent (because of the redistribution of mass) both in terms of rotation speed and a wobble of its rotation axis.

However the estimates are that these are extremely small to be noticeable to us humans (of the order of a few microseconds in the length of the day) !!
kala is offline   Reply With Quote
Old 1st February 2013, 12:05   #70
BHPian
 
CLIX's Avatar
 
Join Date: May 2012
Location: Bangalore
Posts: 121
Thanked: 85 Times
Default Re: About Rocket Science & Engines

Thx Kala.
I assumed it was AlphaKilo answering! Noticed today that the name is a little different
CLIX is offline   Reply With Quote
Old 1st February 2013, 14:25   #71
Senior - BHPian
 
Join Date: Oct 2008
Location: Bangalore
Posts: 1,085
Thanked: 583 Times
Default Re: About Rocket Science & Engines

Quote:
Originally Posted by CLIX View Post
I assumed it was AlphaKilo answering! Noticed today that the name is a little different
Ha ha.. Saw a topic that happened to be in my area of interest while I was browsing the Shifting Gears forum, so jumped in with what little I knew about it

Just finished reading the whole thread - Great work, AlphaKilo ! Thanks for making a lot of TBHP'ians aware that Rocket Science isn't that big a "Rocket Science" !

This used to be my area of work till about 25 years ago (I must have quit that job at about the time when AK was born - I notice), and was pleasantly surprised to notice that I still remember a lot of the stuff that he was talking about. A couple of minor errors that I'd like to point out :

1) The inclination of earth's axis is approx. 23.5 degrees from its orbit normal - not 11 degrees. If it were 11 degrees, anyone who lived north of 11 degrees latitude (north of the horizontal line passing through somewhere around Coimbatore) would never have been able to see the sun directly overhead at any time of the year. Also Geostationary satellites would have had daily "eclipses" almost throughout the year except for a few months around June and December. (With a 23.5 inclination, these eclipse seasons last only about 1.5 months every 6 months).

2)
Quote:
Originally Posted by AlphaKilo View Post
In-order to be able to escape the atmosphere, we use rockets, which act like a transport system for the satellites to reach the desired orbit. These rockets are designed to reach the magic number of 11.8 m/s (escape velocity) which will propel any object out of the earth's gravity pull. Once after escaping the atmosphere, the satellite is either seperated from the transport rocket or is injected into its orbit by a mini-rocket attached to the satellite. The momentum (energy with which the object was propelled into this motion) is carried forward and is used to reach the desired altitude.
The escape velocity of 11.8 km/sec (The unit should be km/s, not m/s) is actually the velocity that a rocket must achieve if it needs to launch a satellite to deep space - i.e escape the gravitational pull of the earth entirely (as correctly mentioned above) - but not to take it out of earth's atmosphere - the atmosphere has nothing to do with it. The velocity achieved by rockets that inject satellites into earth centred orbits is lower - (typically 7 to 8 km/secs), so the rocket design goal is to take the satellite to an altitude that is part of its intended orbit (typically the perigee point) and impart it the precise velocity that is required to achieve the desired orbit. (as AK has correctly described in the paragraph below that)

3) Also I disagree with AK's definition of "Specific Impulse" (I_sp) as the time for which each engine can go on providing thrust (in the first post). "Specific impulse" is just a measure of the efficiency of an engine. It is actually the thrust delivered by the engine per unit propellant usage rate (i.e thrust generated divided by the weight of propellant consumed per unit time). It just so happens that when you put in the units of thrust,weight and time into the equation, the result happens to have a unit of "seconds". It has absolutely no relevance to any physical elapsed time.

AK - please do not consider this as criticism. I know it would have been absolutely impossible for me to have put across all these stuff in simple layman's terms in spite of me having worked in this field for over a decade. So kudos to you for the excellent effort, do keep it up !
kala is offline   Reply With Quote
Old 1st February 2013, 14:42   #72
BHPian
 
AlphaKilo's Avatar
 
Join Date: Nov 2010
Location: VOMM-EDDW-EDDM
Posts: 773
Thanked: 362 Times
Default Re: About Rocket Science & Engines

Quote:
Originally Posted by CLIX View Post
Thx Kala.
I assumed it was AlphaKilo answering! Noticed today that the name is a little different
Hehehehe Caught sleeping in the class!!

Quote:
Originally Posted by kala View Post
Ha ha.. Saw a topic that happened to be in my area of interest while I was browsing the Shifting Gears forum, so jumped in with what little I knew about it
Just finished reading the whole thread - Great work, AlphaKilo ! Thanks for making a lot of TBHP'ians aware that Rocket Science isn't that big a "Rocket Science" !
This used to be my area of work till about 25 years ago (I must have quit that job at about the time when AK was born - I notice), and was pleasantly surprised to notice that I still remember a lot of the stuff that he was talking about.
You are most welcome sir and I am in fact flattered by your appreciation. I am very honoured to have an expert like you contributing here and would be great if you can share more of your knowledge. (Even I will learn!!)

Quote:
A couple of minor errors that I'd like to point out :
Inclination and Escape velocity - Thanks for pointing out the error sir. I should say I slept off while writing that longgggg post (escape vel.) .
Apologies to all who might have been misguided.

Quote:
but not to take it out of earth's atmosphere - the atmosphere has nothing to do with it. The velocity achieved by rockets that inject satellites into earth centred orbits is lower - (typically 7 to 8 km/secs)
yes sir but the term atmosphere here led to a confusion I believe, I just wanted to give an idea to readers that what actually escaping the Earth means. There are two different escapes,

1. reaching a LEO/MEO/GEO

2. Escaping out of Earth's sphere of influence

and to emphasize my intention of talking about 1. i mentioned atmosphere. But you are right in pointing out the actual difference, which I believe by now our readers will be able to differentiate between.

Quote:
so the rocket design goal is to take the satellite to an altitude that is part of its intended orbit (typically the perigee point) and impart it the precise velocity that is required to achieve the desired orbit. (as AK has correctly described in the paragraph below that)
Recent analysis from the launch of TDRS(NASA) satellites and Galileo (European Navi. sat reaching for MEO) are arguing that more than perigee boost, apogee boost is fuel efficient. I am not sure about this though, but will add the info as and when I come across that.

Quote:
3) Also I disagree with AK's definition of "Specific Impulse" (I_sp) as the time for which each engine can go on providing thrust (in the first post). "Specific impulse" is just a measure of the efficiency of an engine. It is actually the thrust delivered by the engine per unit propellant usage rate (i.e thrust generated divided by the weight of propellant consumed per unit time). It just so happens that when you put in the units of thrust,weight and time into the equation, the result happens to have a unit of "seconds". It has absolutely no relevance to any physical elapsed time.

AK - please do not consider this as criticism. I know it would have been absolutely impossible for me to have put across all these stuff in simple layman's terms in spite of me having worked in this field for over a decade. So kudos to you for the excellent effort, do keep it up !
Sir, I appreciate the fact that you took time out of your schedule to pen down the corrections and I am absolutely honoured.

I am just a budding "Rocket" engineer (well not exactly Rockets! but I believe I am allowed to use that general terminology) enthusiastic to learn. Once again I would like to impress upon you that please find some time to contribute to this thread, so that we can learn from real experts.

@Kala sir, one poking the nose question - may I ask you to explain about your work from the past? (Which dept., which launches you were responsible for and so on! just curious hope you don't mistake me.)

Last edited by AlphaKilo : 1st February 2013 at 14:44.
AlphaKilo is offline   Reply With Quote
Old 1st February 2013, 14:56   #73
BHPian
 
CLIX's Avatar
 
Join Date: May 2012
Location: Bangalore
Posts: 121
Thanked: 85 Times
Default Re: About Rocket Science & Engines

Quote:
Originally Posted by AlphaKilo View Post
Hehehehe Caught sleeping in the class!!
He he! Almost!
Good to see another expert joining in. Look forward to more.
CLIX is offline   Reply With Quote
Old 1st February 2013, 18:02   #74
Senior - BHPian
 
Join Date: Oct 2008
Location: Bangalore
Posts: 1,085
Thanked: 583 Times
Default Re: About Rocket Science & Engines

Quote:
Originally Posted by AlphaKilo View Post
@Kala sir, one poking the nose question - may I ask you to explain about your work from the past? (Which dept., which launches you were responsible for and so on! just curious hope you don't mistake me.)
Skip the "sir" part - please

I worked for ISRO from mid-70's to mid-80's. Was in Sensors design for most of the early years, then went into Mission Planning & Analysis, Orbital Mechanics etc in the later half of my career.

Was part of the project teams for Bhaskara (India's first earth observations satellite), Apple (Our first communication satellite) and INSAT-1 projects apart from some of the smaller Rohini satellite projects.
kala is offline   Reply With Quote
Old 4th February 2013, 15:34   #75
BHPian
 
AlphaKilo's Avatar
 
Join Date: Nov 2010
Location: VOMM-EDDW-EDDM
Posts: 773
Thanked: 362 Times
Default Re: About Rocket Science & Engines

Quote:
Originally Posted by kala View Post
Skip the "sir" part - please

I worked for ISRO from mid-70's to mid-80's. Was in Sensors design for most of the early years, then went into Mission Planning & Analysis, Orbital Mechanics etc in the later half of my career.

Was part of the project teams for Bhaskara (India's first earth observations satellite), Apple (Our first communication satellite) and INSAT-1 projects apart from some of the smaller Rohini satellite projects.
OT Question: Have you met the "Missile Man" of India? I believe he was working on the launch side during the Bhaskara and Rohini days and that you would have had enough opportunities to meet/interact?

Those must have been really primitive days for space research yet one of my favourite decades in terms of space research because I believe the base for today's technology was laid back in those days. (although I was not even born in that time I consider the people who worked during that time in space to be the luckiest ones).

I have often heard from the giants(with 30+ yrs of experience) in my dept. regarding their early days (late 70's/early80's) that how they used to do hand-calculations for contact times and to determine orbital positions of satellites.

Everybody remember those were days without GPS/GLONASS and high-tech radar surveillances were nearly not discovered.
AlphaKilo is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Fiat’s Multiair engine wins Popular Science award Klub Class The International Automotive Scene 4 25th November 2010 10:07
Easing Bangalore Traffic - Rocket Science? leodelg Street Experiences 239 20th November 2010 10:20
Is there an art/science of driving over different types of potholes? khan_sultan Technical Stuff 30 16th January 2010 12:34
Treat for car and science fanatics from Paris- rally cars, engine assembly line pics! sidindica Shifting gears 3 26th December 2008 23:11


All times are GMT +5.5. The time now is 03:08.

Copyright ©2000 - 2017, Team-BHP.com
Proudly powered by E2E Networks