Mangalyaan : ISRO's Mars Orbiter Mission

The Military Issues & History Forum is a venue to discuss issues relating to the military aspects of the Indian Armed Forces, whether the past, present or future. We request members to kindly stay within the mandate of this forum and keep their exchanges of views, on a civilised level, however vehemently any disagreement may be felt. All feedback regarding forum usage may be sent to the moderators using the Feedback Form or by clicking the Report Post Icon in any objectionable post for proper action. Please note that the views expressed by the Members and Moderators on these discussion boards are that of the individuals only and do not reflect the official policy or view of the Bharat-Rakshak.com Website. Copyright Violation is strictly prohibited and may result in revocation of your posting rights - please read the FAQ for full details. Users must also abide by the Forum Guidelines at all times.
SSSalvi
BRFite
Posts: 666
Joined: 23 Jan 2007 19:35
Location: Hyderabad
Contact:

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby SSSalvi » 23 Sep 2014 19:42

^^^
There are two slides with the photos of 2 oldie Indians in NASA. 1 or 2 sentences are spoken by them pertain to a REGULAR international space missions tracking network used by ALL countries. Replace India with France, Germany .. and you will find that those sentences are still valid .. only thing that rediff will change is that a couple of French or German guys making those statements.

India can also make those statements when our stations ( actually these networks are more of a international property than 'our' and 'their' ) give support .. yes SUPPORT .. not 'use our station'.

Mention of other countries in this clearly comes out as a polititical necessity.

Incidentally both the Indians belong to a region where Indian political power is currently.

( International co-operation in Space missions out of Earth is a necessity .. you can't 'see' Mars or any space object on 24*7 basis from any point on Earth. You have to use other locations when the object goes below horizon.

For deep space missions you can't use boats because they are not stable to provide a vibration free platform for big antennas with narrow beams .. it is technical requirement .. elementary ,Watson, elementary :wink: )

disha
BR Mainsite Crew
Posts: 7251
Joined: 03 Dec 2006 04:17
Location: gaganaviharin

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby disha » 23 Sep 2014 20:10

prasannasimha wrote:
Actually the sphere of influence etc is used to solve the interplanetary transfer using the patch conic approximations to simplify an "N " body problem into a series of 2 body problems.


http://en.wikipedia.org/wiki/Patched_co ... roximation


Something I learned today. +1 to DDM and -1 to me :((

Regarding the rediff article about "NASA Support"., the article attributes non-existing contributions from NASA for genuflecting Indians! First thing we need to do seriously is to trash such articles.

Chandrayaan/Mangalyaan are India's missions and Indian missions alone. Further Indians have been more open and honest., pointing out - here we are launching a bus and this is the scientific goal. If you think you have a good instrument to measure that, we would like to offer you the bus and in the process also learn how you measure something. Nobody is doing us any favour by putting their science experiment on our bus.

Without Chandrayan, we would not have confirmed water on moon. The heartburn among americans when that was announced was seen to be believed.

And for tracking purposes, they are covered under international agreements where everybody has to cooperate. We are sharing one earth onlee,,,

Victor
BRF Oldie
Posts: 2628
Joined: 24 Apr 2001 11:31

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Victor » 23 Sep 2014 21:09

^^^A third of NASA engineers and scientists are Indian, many of them in the top layer, so there is "an Indian connection" to every American space project. There is cooperation but also cutthroat competition. India's Hanle station in Ladakh is priceless to global astrophysics and space efforts and more like it will sprout in future. It's not that we cannot have our own network to support Byalalu in Africa, S. America and Fiji, it just helps everyone to cooperate in interplanetary efforts. After MOM things will move fast in that area. In our neighbourhood--whole of Asia to Mid-East--we are totally self-reliant for military tracking.

Amber G.
BRF Oldie
Posts: 6860
Joined: 17 Dec 2002 12:31
Location: Ohio, USA

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Amber G. » 23 Sep 2014 21:11

prasannasimha wrote:
disha wrote:(>>>(From AmberG)
(I have been interested in astronomy and space orbit mechanics for decades but I heard the term SOI only recently - in last few years)<<<

It is *for* the DDM. It is like telling them, we are near to Mars. Otherwise DDM will be lost in searching ether in space.


Actually the sphere of influence etc is used to solve the interplanetary transfer using the patch conic approximations to simplify an "N " body problem into a series of 2 body problems.


http://en.wikipedia.org/wiki/Patched_co ... roximation


Thanks. (I have also became familiar with this term (SOI), a few yeas ago only, but as I said I have not heard this term from any of my physics professors in my classical mechanics classes).

My point was, from my point of view, the technique of perturbation (patch conic approximations) is very useful if one is doing calculation by hand. With computers these days, brute-force solving (numerically) the differential equation, IMO, is much simpler.

Something like using log tables (or Taylor's expansion for doing physics problem) was VERY useful when I was in college but with calculators these days most do not need log tables, and can not care less if they know that log2=.30103 :).

So what I was interested was, is there any "significance" - which can be explained in layman's term.

For example, many (including many posts here in brf in earlier pages) described it, as : if at point P Sun's gravitational force is equal to Earth's gravitational force, then point P is at SOI of earth. This is not true.

(For those who are curious - you take the ratio as not square of distance but rather (2.5) power of the distance - the details - why you do it is rather complicated math)

IOW, one can describe orbit, distance etc in layman's term.. how does one describe SOI in such simple terms..

I may be missing something really obvious.. so if someone can point it out, it will be nice. Thanks in advance.

harbans
BRF Oldie
Posts: 4883
Joined: 29 Sep 2007 05:01
Location: Dehradun

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby harbans » 23 Sep 2014 21:11

This is a link that has pretty good composite coverage on the MOM with diagrams, animations etc right from launch time. Do check it out:

http://www.spaceflight101.com/mars-orbi ... dates.html

SaiK
BRF Oldie
Posts: 36402
Joined: 29 Oct 2003 12:31
Location: NowHere

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby SaiK » 23 Sep 2014 21:15

dinesha et al, i don't read the pisskology factor that way.. think about using nasa assets of deep space communication setup as a denial of technology in terms of babooze budgetry needs - why build something, when we can support you? we get to control your missions basically.

what i think is mr panda is not saying is, this is strategically bad, but good in terms of business onlee (again if..). now, it is entirely upto us to rely on our own deep space networks.. and this is the shocker dhoti shiver and not delivering WMDs to anywhere on the planet. deep space comm is where we need to focus in the future along with ion engines and deep space nuke power technologies.

Amber G.
BRF Oldie
Posts: 6860
Joined: 17 Dec 2002 12:31
Location: Ohio, USA

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Amber G. » 23 Sep 2014 21:17

disha wrote:
+1 to DDM and -1 to me :((


Okay, FYI here is -400,000 to DDM ... and that too to "respectable" WSJ.. and all you have to do is to read the headlines onlee... :) )
NASA’s Maven Craft :eek: Beats India’s Mangalyaan in Space Race :eek: to Mars

Raja
BRFite
Posts: 105
Joined: 01 Jan 1970 05:30

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Raja » 23 Sep 2014 21:18

Don't want to derail this thread but this stupid claim that started out as an email spam (and even got into toilet newspaper) is not true and any smart jingoist should not get caught with his pants down spewing it as truth. Indians don't make up anywhere close to a third of NASA (or Google or Microsoft etc.)

Victor wrote:^^^A third of NASA engineers and scientists are Indian, many of them in the top layer, so there is "an Indian connection" to every American space project. There is cooperation but also cutthroat competition. India's Hanle station in Ladakh is priceless to global astrophysics and space efforts and more like it will sprout in future. It's not that we cannot have our own network to support Byalalu in Africa, S. America and Fiji, it just helps everyone to cooperate in interplanetary efforts. After MOM things will move fast in that area. In our neighbourhood--whole of Asia to Mid-East--we are totally self-reliant for military tracking.

member_28108
BRFite
Posts: 1852
Joined: 11 Aug 2016 06:14

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby member_28108 » 23 Sep 2014 22:04

Amber G. wrote:
prasannasimha wrote:
Actually the sphere of influence etc is used to solve the interplanetary transfer using the patch conic approximations to simplify an "N " body problem into a series of 2 body problems.


http://en.wikipedia.org/wiki/Patched_co ... roximation


Thanks. (I have also became familiar with this term (SOI), a few yeas ago only, but as I said I have not heard this term from any of my physics professors in my classical mechanics classes).

My point was, from my point of view, the technique of perturbation (patch conic approximations) is very useful if one is doing calculation by hand. With computers these days, brute-force solving (numerically) the differential equation, IMO, is much simpler.

Something like using log tables (or Taylor's expansion for doing physics problem) was VERY useful when I was in college but with calculators these days most do not need log tables, and can not care less if they know that log2=.30103 :).

So what I was interested was, is there any "significance" - which can be explained in layman's term.

For example, many (including many posts here in brf in earlier pages) described it, as : if at point P Sun's gravitational force is equal to Earth's gravitational force, then point P is at SOI of earth. This is not true.

(For those who are curious - you take the ratio as not square of distance but rather (2.5) power of the distance - the details - why you do it is rather complicated math)

IOW, one can describe orbit, distance etc in layman's term.. how does one describe SOI in such simple terms..

I may be missing something really obvious.. so if someone can point it out, it will be nice. Thanks in advance.

The patch conic approximation is still used for interplanetary travel as long as we are not targeting things like Lagrangian points or its equivalents. These have been found to work well enough that brute force methods need not be used and (Remember I am not a mathematician but a cardiac surgeon so some one can correct me) current solutions to n body problems can give rise to singularities in the solutions so this poses problems in analysis so it is not as simple as it sounds. Also these fuzzy techniques that are used to predict the interplanetary transport network using computer networks are not exactly "economical' wrt time and take a longer time and has been used (for example the Genesis mission) and the Hiten Japanese probe was salvaged using this method but for straight forward transfers the patch conic method still is useful and accurate enough.

Amber G.
BRF Oldie
Posts: 6860
Joined: 17 Dec 2002 12:31
Location: Ohio, USA

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Amber G. » 23 Sep 2014 22:11

Amber G. wrote:
saravana wrote:Amber G, I have a very noob question. why does it have to depend on this? Can't it be timer based? if all the parameters are known, like location, velocity etc, wouldn't it be fired based on elapsed time from say, t0?


Again, hope the answer is useful..
Short answer is "This is how isro scientists designed it.". (IOW, they thought that this is better than depending on "timer" value)

Few items for background and rational behind the above method..

- For navigational purpose - to find where MOM is (or it's position wrt to Mars), the radio navigational system with accurate clocks (atomic clocks have accuracy about 1 in 100 TRILLION - MOM does not have an atomic clock but reference frequency from ground station gives it an accurate clock). Even if you consider accuracy of 1 part in 10 million (actual values are better).. One can determine position of MOM within 50 Km wrt to earth, and a meter or so wrt to Mars. Better than we need.

- Similarly the velocity can be measured VERY accurately (using Doppler)..

With those above two value, one can VERY accurately calculate the PRECISE (better than we need) trajectory and delta-V needed and initial point (T_0) when we should start the rockets. (One can probably have a margin of 20-30 seconds - or about 100 Km wrt to Mars to start the sequence)

- The amount of fuel used, direction of the rockets and other control are less precise (than say 1 in million ). The direction gyro's can probably be accurate up to a milirad (about tenth of a degree), timers to control the nozzle - about a msec or so etc)

The amount of fuel to be used, how long the engines should run, and when to stop the engines, is best determined by actual acceleration felt by the system (and total delta-V). For this inertial systems are most reliable and simple to use (and their accuracy is better than we need)...

The system is set so the engines are stopped as soon as total delta-V is achieved (measured by those internal accelerometers)


To add, Link given by Harbans above says: (same point as I was making)

It is known that LAM can lose up to 2% of performance in terms of specific impulse over time which could also be the case for the MOI burn. To achieve the planned change in velocity of 1,100 meters per second, MOM will use its accelerometers to track the burn progress and shut the engine down when the target delta-v has been achieved – compared to an engine cutoff commanded after a given burn time that does not take into account the actual delta-v. The MOI burn will also be the longest retrograde firing ever performed by the LAM.


BTW, Interesting part (to me at least).. at present MOM has about 290 Kg of fuel left (it started with 850 Kg but most was burned near earth for initial journey).. It is going to use about 240-250 Kg of in MOI. (If LAM did not work, and one has to use side thrusters alone it would have used some thing like 280 kg or more .. leaving very little fuel )... So if everything goes well there will be 40-50 Kg fuel left...

Hopefully after a few months, we still have some fuel left to do some further delta-V reduction and go in a closer orbit or use the fuel some fun way..:)

ravip
BRFite
Posts: 270
Joined: 11 Aug 2016 06:14

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby ravip » 23 Sep 2014 22:16

Here is one silly noob question..mod Abdul's pls forgive....lazy to Google the answer so asking for gyaan...

1. If the satellite moves at a speed of 22 km/sec during transition to mars, what is the effect on the structural integrity of d satellite and how can it with stand such great forces, as seen in pictures the solar arrays are so thin and delicate.

2. Is there any possibility that our enemy country can jam signals from our command centre during crucial command transfer or uploading to the satellite.

Uttam
BRFite
Posts: 302
Joined: 15 Apr 2003 11:31
Location: USA

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Uttam » 23 Sep 2014 22:25

:roll: Why are we discussing here what the moronic media says across the world? Please let this thread be what its title suggests and take our complains about media elsewhere.

Vayutuvan
BRF Oldie
Posts: 10346
Joined: 20 Jun 2011 04:36

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Vayutuvan » 23 Sep 2014 22:25

Prasannasimha ji: AmberG ji is correct. "brute force" methods as you put it are not only not brute force but they are the only way to solve some real-life previously unsolvable differential equations and PDEs today. One reason is that there are no closed form solutions (i.e. nice looking functions) and the other is that the differential equation is defined on a domain whose properties are not constant through out (they might be a function of their spatial location (x,y,z) or depend on the displacement or stress or strain or temperature).

Almost all functions even in single variable are non-integrable. They can be proved to be dense in the function space which has uncountable number of functions. Please keep in mind that one needs to integrate functions (almost always in several variables and sometimes these are vector valued functions as well) to solve differential eqns or PDEs. The better the approximation, the better the solution.

As for singularities, they should be handled one way or the other. For example Lamgrange point is a point (an abstract point) if all planetary masses are considered point masses but that is hardly the case in reality. In reality, there is no real point mass (as long as we stay with in classical mechanics and non-relativistic velocities).

If the physical problem does have a solution, a corresponding the mathematical problem coming out of the mathematical model of the physical problem should have a solution. If it does not, then the model is not physically correct. Added to this there we also have to be cognizant of the fact that any physically realizable computing device - digital or analog - can compute only numerical functions that too with only finite precision.

These mathematical problems are always always a system of algebraic equations and almost always have side constraints. So if one gets into a situation where this mathematical system does not have any solutions are more than one solution then one has to find a better theory or better modeling or both to show that there is a solution and it is the required solution. This happens when either the model has not been constructed properly or enough number of constraints are not imposed.

For example constraints like vector sum of reaction forces should be strictly equal to the vector sum of the applied forces summed up (for non-linear problems this could mean a local solution only and would not match the way the physical system behaves). In practice strict equality is not detectable (again due to numerical error accumulation resulting from finite precision) so some kind of norm (and I am familiar with only normed spaces) is used to show that the vectors are equal for all practical purposes. This is usually shown taking each vector to be a point in a n-dimensional space and showing that both the points lie inside of an n-ball of \epsilon radius where is \epsilon is a parameter dependent on the application - usually 1.oe-8 or 1.0e-12 for almost all engineering and classical mechanics applications and 1.0e-3 or 1.0e-6 for most engineering applications.

Sometimes if the system is over-determined, some degrees of freedom are fixed which is called gauge fixing. I think guru AmberG would be able to throw more light on what is gauge fixing. One of these I have to get off my backside and really understand what this gauge fixing thingy is. Certain amount of intuition about the physics of the problem you are trying to solve is required to choose the appropriate gauge to fix.

(Corrected spelling. and grammatical errors and tried to make the exposition a little better)
Last edited by Vayutuvan on 24 Sep 2014 03:20, edited 2 times in total.

TSJones
BRF Oldie
Posts: 3022
Joined: 14 Oct 1999 11:31

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby TSJones » 23 Sep 2014 22:26

ravip wrote:Here is one silly noob question..mod Abdul's pls forgive....lazy to Google the answer so asking for gyaan...

1. If the satellite moves at a speed of 22 km/sec during transition to mars, what is the effect on the structural integrity of d satellite and how can it with stand such great forces, as seen in pictures the solar arrays are so thin and delicate.

2. Is there any possibility that our enemy country can jam signals from our command centre during crucial command transfer or uploading to the satellite.


If you are asking if an enemy satellite can jam India's satellite relay signal to Nasa's global system the answer is yes. but highly doubtful unless somebody wants to start a war.

Comer
BRF Oldie
Posts: 3574
Joined: 11 Aug 2016 06:14

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Comer » 23 Sep 2014 22:37

Some international feel good factor

https://i.imgur.com/cj1mWIM.jpg

member_28108
BRFite
Posts: 1852
Joined: 11 Aug 2016 06:14

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby member_28108 » 23 Sep 2014 22:40

matrimc wrote:Prasannasimha ji: AmberG is correct. "brute force" methods as you put it are not only not brute force but they are the only way to solve some real-life previously unsolvable differential equations and PDEs today. Almost all functions even in single variable are non-integrable. They can be proved to be dense in the function space. Remember one needs to integrate to solve differential eqns or PDEs. The better the approximation the better the solution. As per singularities, they should be handled.if they cannot be handled, either your model is incorrect or one needs to develop better theory to show that the solution lies in certain region - usually done through constraints. For example constraints like reaction forces should sum (vector sum) up to the applied forces summed up or certain gauge fixation is done. I think guru AmberG would be able to throw more light on what is guage fixing. One of these I gave get off my backside and really understand what thus means in physical terms.


I do agree that differential equations and partial differential equations which have multiple or infinite solutions need computers to get a best approximation but it seems that the patched conic approximation is still used for most interplanetary flight except for low energy/ ballistic capture transfers

UPrabhu
BRFite -Trainee
Posts: 99
Joined: 21 Sep 2004 11:51

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby UPrabhu » 23 Sep 2014 22:44

Saravana,

Timer based will be open loop. With accelerometers it is closed loop and if enginer underperforms or overperforms, using accelerometers u can burn the engine longer or cutoff early. With timer based you will not able to do this.

Amber G. wrote:
saravana wrote:Amber G, I have a very noob question. why does it have to depend on this? Can't it be timer based? if all the parameters are known, like location, velocity etc, wouldn't it be fired based on elapsed time from say, t0?


Again, hope the answer is useful..
Short answer is "This is how isro scientists designed it.". (IOW, they thought that this is better than depending on "timer" value)

Few items for background and rational behind the above method..

- For navigational purpose - to find where MOM is (or it's position wrt to Mars), the radio navigational system with accurate clocks (atomic clocks have accuracy about 1 in 100 TRILLION - MOM does not have an atomic clock but reference frequency from ground station gives it an accurate clock). Even if you consider accuracy of 1 part in 10 million (actual values are better).. One can determine position of MOM within 50 Km wrt to earth, and a meter or so wrt to Mars. Better than we need.

- Similarly the velocity can be measured VERY accurately (using Doppler)..

With those above two value, one can VERY accurately calculate the PRECISE (better than we need) trajectory and delta-V needed and initial point (T_0) when we should start the rockets. (One can probably have a margin of 20-30 seconds - or about 100 Km wrt to Mars to start the sequence)

- The amount of fuel used, direction of the rockets and other control are less precise (than say 1 in million ). The direction gyro's can probably be accurate up to a milirad (about tenth of a degree), timers to control the nozzle - about a msec or so etc)

The amount of fuel to be used, how long the engines should run, and when to stop the engines, is best determined by actual acceleration felt by the system (and total delta-V). For this inertial systems are most reliable and simple to use (and their accuracy is better than we need)...

The system is set so the engines are stopped as soon as total delta-V is achieved (measured by those internal accelerometers)

member_28332
BRFite -Trainee
Posts: 21
Joined: 11 Aug 2016 06:14

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby member_28332 » 23 Sep 2014 22:48

saravana wrote:Some international feel good factor

https://i.imgur.com/cj1mWIM.jpg


For a moment, there were no countries, no squabbles, no political boundaries. Just people supporting each other and working together. Felt wonderful. The power of education removes pettiness in the world.

Comer
BRF Oldie
Posts: 3574
Joined: 11 Aug 2016 06:14

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Comer » 23 Sep 2014 22:55

UPrabhu wrote:Saravana,

Timer based will be open loop. With accelerometers it is closed loop and if enginer underperforms or overperforms, using accelerometers u can burn the engine longer or cutoff early. With timer based you will not able to do this.

*snip*

Thanks, that makes sense.
EDIT: then again, it adds another amount of complexity to the whole system. I guess the tradeoff must be worth it.

Amber G.
BRF Oldie
Posts: 6860
Joined: 17 Dec 2002 12:31
Location: Ohio, USA

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Amber G. » 23 Sep 2014 23:20

ravip wrote:Here is one silly noob question..mod Abdul's pls forgive....lazy to Google the answer so asking for gyaan...

1. If the satellite moves at a speed of 22 km/sec during transition to mars, what is the effect on the structural integrity of d satellite and how can it with stand such great forces, as seen in pictures the solar arrays are so thin and delicate.

2. Is there any possibility that our enemy country can jam signals from our command centre during crucial command transfer or uploading to the satellite.


1) Solar arrays are deployed after MOM's departure from earth, and the during the whole journey as this is "free fall" or "zero g" there are NO stress forces. (That is why you can have large - very large - and thin and delicate panels with flimsy support structure on a spaceship.

Only time these arrays (or MOM) will now face "stress" is MOI rocket firing... but the stress will be less than 1/10th of what those panels will feel on earth if they are just sitting in a shop (because of their weight)

2) Yes, it *can* happen but not likely :) (For that matter, an "enemy" can even destroy the whole command center by chemical bombs and that will require much less technical know-how than jamming the signals).

Victor
BRF Oldie
Posts: 2628
Joined: 24 Apr 2001 11:31

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Victor » 23 Sep 2014 23:29

Raja wrote:Don't want to derail this thread but this stupid claim that started out as an email spam (and even got into toilet newspaper) is not true and any smart jingoist should not get caught with his pants down spewing it as truth. Indians don't make up anywhere close to a third of NASA (or Google or Microsoft etc.)

I was wrong. 36% of NASA is Indian, not 33%.

36% of scientists at NASA are Indians: Govt survey

If you thought that Global Indian Takeover was just a hollow cliche leaning on a few iconic successes like Pepsi's Indra Nooyi, Citibank's Vikram Pandit and steel world's Lakshmi Mittal, there is a slew of statistics now to give it solid ballast.

The extent to which desis have made an impact in the US was reeled off in the Rajya Sabha — as many as 12% scientists and 38% doctors in the US are Indians, and in NASA, 36% or almost 4 out of 10 scientists are Indians.

If that's not proof enough of Indian scientific and corporate prowess, digest this: 34% employees at Microsoft, 28% at IBM, 17% at Intel and 13% at Xerox are Indians.


The above figures are not TOI's but the Indian Government's:

The figures of Indian successes were given to the Rajya Sabha on Monday by D Purandeshwari, minister of state for HRD, in defence of the country's higher education system and the state of research.


If you feel these are wrong, you'd do us all (incl GoI) a favor by backing up your assertion with a link.

Amber G.
BRF Oldie
Posts: 6860
Joined: 17 Dec 2002 12:31
Location: Ohio, USA

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Amber G. » 23 Sep 2014 23:30

saravana wrote:
UPrabhu wrote:Saravana,

Timer based will be open loop. With accelerometers it is closed loop and if enginer underperforms or overperforms, using accelerometers u can burn the engine longer or cutoff early. With timer based you will not able to do this.

*snip*

Thanks, that makes sense.
EDIT: then again, it adds another amount of complexity to the whole system. I guess the tradeoff must be worth it.


... Not really. (Many will say it reduces the complexity). In practical terms, the accelerometer "readings" (These equipments AD converters change value of acceleration to frequency, and what is needed "integration" (to compute delta-V).. that is the total count of pulses).. are done by counting pulses..almost exactly if that system was based on a timer. (Instead of counting pulses from a quartz crystal or some thing similar you count pulses from these accelerometers - which are self contained and therefore less things to go wrong)

Viv S
BRF Oldie
Posts: 5303
Joined: 03 Jan 2010 00:46

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Viv S » 23 Sep 2014 23:41

Victor wrote:
Raja wrote:Don't want to derail this thread but this stupid claim that started out as an email spam (and even got into toilet newspaper) is not true and any smart jingoist should not get caught with his pants down spewing it as truth. Indians don't make up anywhere close to a third of NASA (or Google or Microsoft etc.)

I was wrong. 36% of NASA is Indian, not 33%.

36% of scientists at NASA are Indians: Govt survey



Singhs & Guptas In NASA!

D.PURANDESWARI, MINISTER of State in the Human Resource Development Ministry, is a happy woman these days. Against all odds, and among colleagues whose incompetence is legendary, her performance is drawing raves from all over the world. Thanks to her tireless campaign, 36 percent of the scientists at NASA are now Indians, as are 38 percent of doctors in the United States, according to a statement she made to the Rajya Sabha, as reported in The Times of India on March 11.
.
.
These new numbers, however, are the results of a “government survey” and were presented by a minister, so I shook myself awake. Ah, my blinkered vision! In all my years as a research scientist for NASA, how had I missed the large number of Indians — four out of ten — whom I must have passed in the hallways? Had I not noticed the hordes of Guptas, Venkats, Singhs and Srinivasans? Given her reputation for punctiliousness, the minister no doubt looked at the numbers from all NASA centres combined. So I went where individuals not affiliated with expensive government surveys go — to http://nasapeople.nasa.gov/Workforce/default.htm — and clicked on demographic information, which brought up a chart for the workforce profile at NASA.ce.
.
.
The number of such scientists was about 8 percent of the total, of which a significant fraction are likely to be Indians. If you further restrict the search to those holding PhDs, the count is 293 out of 1,919, which is 15 percent. These numbers, of course, do not tell the whole story. Many NASA scientists are sub-contractors, as was I, and are not counted as employees. Even if you include them all, however, and make the most generous assumptions about the number of Indians who have any connection with science at NASA, that number will likely lie between 3 and 6 percent of the science workforce.
.
.
Now, you might ask why D. Purandeswari would put her foot in her mouth over a meaningless statistic. The answer to this is far more disturbing than the fantastic numbers in her survey: she was using the number of ex-Indians at NASA to justify expenditure on higher education in India. Now all we need to do is transfer D. Purandeswari to the Department of School Education and Literacy.
Last edited by Viv S on 23 Sep 2014 23:44, edited 1 time in total.

Amber G.
BRF Oldie
Posts: 6860
Joined: 17 Dec 2002 12:31
Location: Ohio, USA

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Amber G. » 23 Sep 2014 23:43

Victor wrote:I was wrong. 36% of NASA is Indian, not 33%.

36% of scientists at NASA are Indians: Govt survey

.


Victor, if you do your own checking you will find that above story is akin to US Rep Michele Bachmann claiming that Obama india trip was costing 10,000,000,000 Rs a day.

There were no official figures from NASA and that MP should be shameful for making a fool of him/herself. (Estimate from what I hear from Indians who actually work in NASA - is about 4-5%... that is a very respectable number)
Last edited by Amber G. on 23 Sep 2014 23:45, edited 1 time in total.

saip
BRF Oldie
Posts: 3660
Joined: 17 Jan 2003 12:31
Location: USA

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby saip » 23 Sep 2014 23:44

Victor, Ms Purandeswari got fooled too and quoted from those stupid emails floating on the internet. There may be quite a few but no where near 33% Indians at NASA.

ramana
Forum Moderator
Posts: 54023
Joined: 01 Jan 1970 05:30

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby ramana » 23 Sep 2014 23:53

Someone should ask Mr. Panda if he is authorized to speak for NASA. And verify if he meant what he said.

Comer
BRF Oldie
Posts: 3574
Joined: 11 Aug 2016 06:14

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Comer » 23 Sep 2014 23:54

Thanks again Amber G. This has been a good education for me.

Amber G.
BRF Oldie
Posts: 6860
Joined: 17 Dec 2002 12:31
Location: Ohio, USA

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Amber G. » 23 Sep 2014 23:57

... Also a story got published in Business Standard that "IIT Kanpur Mafia runs MIT :)

The fall out was really interesting...I think even Vajpayee mentioned it once.. (To his credit, he was not fooled .. but many people were)

(The origin was one of MIT professor's( Kenneth Keniston) quote at some gathering .. "most of our distinguished faculty is Indian…the joke is that [MIT] is run by an IIT Kanpur mafia."

SaiK
BRF Oldie
Posts: 36402
Joined: 29 Oct 2003 12:31
Location: NowHere

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby SaiK » 24 Sep 2014 01:07

excellent point uprabhu. that was what I was thinking.

amber ji, it is a trade off - complexity & reliability vs risks., i would include the feedback corrections and not relying on one technique as a designer/risk taker stakeholder.

Victor
BRF Oldie
Posts: 2628
Joined: 24 Apr 2001 11:31

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Victor » 24 Sep 2014 01:13


Ah, trust "Finger" Tehelka :) to speak well of India and Indians, and the author is a novelist too, adept at fiction. The link he provided does not lead to any racial information, just demographics based on age, sex etc. Maybe I missed it. Anyway, I am willing to accept that the minister being a minister could fnck up the numbers like they have done all along and half of NASA is not Indian.

Microsoft backs cricket to woo Indian employees
Employees of Indian descent estimate they make up about 15 percent of Microsoft's 35,000 workers in the greater Seattle area. The company does not keep track of such figures

That's only in Seattle.

Sorry for the sidetrack. Back to regular programming.

SagarAg
BRFite
Posts: 1164
Joined: 12 May 2011 15:51

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby SagarAg » 24 Sep 2014 01:40

Thank you Gurus for soo much gyaan. I feel like deeply involved in MOM mission. Kudos to scientists "Guided by wisdom, executed by youths".
Is everyone lungi ready for lungi dance Martian ishtyle :D
Dilbu saar bhere r u..

TSJones
BRF Oldie
Posts: 3022
Joined: 14 Oct 1999 11:31

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby TSJones » 24 Sep 2014 02:07

SaiK wrote:dinesha et al, i don't read the pisskology factor that way.. think about using nasa assets of deep space communication setup as a denial of technology in terms of babooze budgetry needs - why build something, when we can support you? we get to control your missions basically.

what i think is mr panda is not saying is, this is strategically bad, but good in terms of business onlee (again if..). now, it is entirely upto us to rely on our own deep space networks.. and this is the shocker dhoti shiver and not delivering WMDs to anywhere on the planet. deep space comm is where we need to focus in the future along with ion engines and deep space nuke power technologies.


India should build its own system. we are in agreement on that. use your own stuff is best in the long run. Russia and china doesn't use our network.

Victor
BRF Oldie
Posts: 2628
Joined: 24 Apr 2001 11:31

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Victor » 24 Sep 2014 02:41

Youtube: Mangalyaan Entry into Mars orbit - LIVE from ISRO

Times for US in EST PM Tues, 23rd (AFAIK onlee)
06:47 change to medium gain antenna
09:26 forward rotation starts
09:42 eclipse starts
09:44 attitude control with thrusters
09:47 engine burn starts
09:51 mars occult starts
09:52 telemetry off
10:00 confirmation of burn start
10:07 eclipse ends
10:11 engine burn ends
10:12 reverse manouver starts
10:17 telemetry resumes. Doppler provides first info on burn and success
10:21 reverse manouver ends
10:24NASA, ESA, ISRO stations confirm insertion

SSSalvi
BRFite
Posts: 666
Joined: 23 Jan 2007 19:35
Location: Hyderabad
Contact:

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby SSSalvi » 24 Sep 2014 02:51

In MAVEN MOI telecast there definitely were a few Indians in control stations .. but they could be counted on fingers .. Nowhere near 2 - 3 %

Shalav
BRFite
Posts: 588
Joined: 17 Jul 2000 11:31

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Shalav » 24 Sep 2014 03:14

Live feeds

DD Channel on YouTube: https://www.youtube.com/watch?v=VZL_Vwy0JqI
ISRO Live feed: http://webcast.isro.gov.in/

Tanaji
BRF Oldie
Posts: 3272
Joined: 21 Jun 2000 11:31

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Tanaji » 24 Sep 2014 03:39

Another dumb question : Why is the final MOM orbit elliptical and not circular or polar? Am I correct in guessing that these orbits require more fuel for station keeping and to get into that orbit in the first place? Do these orbits provide any advantage over elliptical orbits?

Amber G.
BRF Oldie
Posts: 6860
Joined: 17 Dec 2002 12:31
Location: Ohio, USA

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Amber G. » 24 Sep 2014 03:47

SaiK wrote:excellent point uprabhu. that was what I was thinking.

amber ji, it is a trade off - complexity & reliability vs risks., i would include the feedback corrections and not relying on one technique as a designer/risk taker stakeholder.

Saik - Yes some time it is a trade off, some time it is not as in this case IMO we get both simplicity and reliability. (It is simple, reliable and cost effective), and although people's definition vary, I will not call it "feedback correction".. There is no "feedback" in the sense that the accelerometer does NOT regulate anything, other than shutting off the fuel.
(It is like, when gas-pump automatically shuts off when car tank is full - only feedback is shutting off - a traditional "feedback" system controls/regulates the rate)

My point was, simply to recognize those engineers, as I think no one else has done that. Those systems are very critical and engineering there is remarkable.

shravanp
BRF Oldie
Posts: 2396
Joined: 11 Aug 2016 06:14

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby shravanp » 24 Sep 2014 03:49

Dilbu mantra needed now.

SriKumar
BRFite
Posts: 1894
Joined: 27 Feb 2006 07:22
Location: sarvatra

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby SriKumar » 24 Sep 2014 03:59

ravip wrote:Here is one silly noob question..mod Abdul's pls forgive....lazy to Google the answer so asking for gyaan...

1. If the satellite moves at a speed of 22 km/sec during transition to mars, what is the effect on the structural integrity of d satellite and how can it with stand such great forces, as seen in pictures the solar arrays are so thin and delicate..
I know Amber G. has answered this, but a couple of points. A high velocity does not cause a force, only a high acceleration does. So, if you accelerated from 0 to 22 km/sec over a year, you'd feel a very low force- 0.001 g's. (same thing as being a plane- why do passengers not feel a huge force when moving at 880 kmph).

The other thing to note is that the satellite (and the rocket) already had a huge forward velocity even before it was born. It was born on earth, and all of us on earth move (translate) at 30 km/sec. Even you and I have that velocity- velocity of the earth as it moves around the sun. This is a major component of the satellite velocity (22 km/sec). The only force that the satellite would feel is during launch and the during the orbit-raising maneuvers and during the upcoming LAM burn to slow it down.

SriKumar
BRFite
Posts: 1894
Joined: 27 Feb 2006 07:22
Location: sarvatra

Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby SriKumar » 24 Sep 2014 04:03

Amber G.
the example of analog accelerometers where charge was measured to integrate over time and determine delta 'v' was very interesting and quite charming actually. Its like 'physics works, physics is consistent' (is the best way I can put it). If you have other examples of this, please do post.

At large:
I was thinking about the orbit trajectory....and it seems to me that the polar orbit seems to have a couple of advantages e.g. no eclipse, no occultation. Wonder if it was considered. Also, I wonder if there is another (redundant) system checking for delta-V apart from the accelerators, just to have some level of redundancy or atleast a reference point (like bouncing signals off the surface of Mars/doppler).


Return to “Military Issues & History Forum”

Who is online

Users browsing this forum: No registered users and 48 guests