Indian Space Programme Discussion

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vina
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Re: Indian Space Programme Discussion

Postby vina » 17 Dec 2014 10:01

disha wrote:Wrong analogy., you can as well dunk yourself in the ocean and be a submarine and hold a beaker with a cork in it. You know where the cork will be in this case. :P


Or, you can sit in a hovering helicopter ( the condition when the upward force generated by the rotor is exactly the same as gravity acting on the helicopter and it's contents) , we all know what happens to the cork floating on a beaker of water. That also is like your submarine example a condition where Net Force = Zero

So in Inglees, what you are saying is that Net Force = Zero, does NOT mean that g = 0 and hence you can't put g= 0 in the Pharmoola?


So, what if you are in a "Net Force " is zero condition (or if there is actually a positive force accelerating ) in a rocket and instead of a beaker of water, it is actually a tankful of liquid propellant? Will there be "ullage" (nice big words, but really it is 10th std physics)? For solids, remember there is no ullage, and coming back to GSLV/PSLV, the cores are solid so this ullage business is a red herring, but all the same, even if we assumed that the GSLV/PSLV core stages were liquid, will it matter under such conditions ?

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Re: Indian Space Programme Discussion

Postby symontk » 17 Dec 2014 10:14

vina wrote: For solids, remember there is no ullage, and coming back to GSLV/PSLV, the cores are solid so this ullage business is a red herring, but all the same, even if we assumed that the GSLV/PSLV core stages were liquid, will it matter under such conditions ?


Yes, the ullage motors (solid motors) are for liquid stages in PSLV (not sure about GSLV though). If it was all liquid PSLV, ullage is not required. There is a marked difference between how solid motors peak performance is and liquid engines steady performance. In case of liquid since it has steady performance and impulse will remain for some time after the separation, there is no ullage required. For GSLV, there is no ullage for cryo stage. However for PSLV 4th stage, the fuel is pushed down since the amount is less, so again no ullage required

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Re: Indian Space Programme Discussion

Postby member_28108 » 17 Dec 2014 12:30

Solid rockets do not have an ullage space. Ullage space is present in tanks with something liquid in it. In fact ullage referred to the space above the liquid in a wine barrel and later for other tanksand was later also used for the boil of space in a cryogenic container .Solid rockets do not have flowing propellant so don't have such a space. Also it is only the first stage of GSLV Mk2 that is solid the second stage has hypergolic propellants and obviously the CUS stage is using cryogenic proellants. All the issues relate to gimballing for booster/stage 1 and for the switch over from stage 1 to 2 .

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Re: Indian Space Programme Discussion

Postby symontk » 17 Dec 2014 13:36

prasannasimha wrote:Solid rockets do not have an ullage space. Ullage space is present in tanks with something liquid in it. In fact ullage referred to the space above the liquid in a wine barrel and later for other tanksand was later also used for the boil of space in a cryogenic container .Solid rockets do not have flowing propellant so don't have such a space.


Theoretically you are correct, but in PSLV ullage rockets are placed outside the liquid stage which can be clearly seen, almost middle of the stage, may be related to CG

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Re: Indian Space Programme Discussion

Postby member_28108 » 17 Dec 2014 17:48

Ullage rocket can be there for a liquid motor.This should not be unusual. Basically an ullage rocket will be required to return the fuel which has floated away from the engine intake in microgravity conditions.So at that stage an accelreation is provided to allow the fuel to settle in the tank prior to pumping into the main engine. Of course the ullage motor can be strategically placed to take advantage of any other requirements like CG etc and also has to factor in when ullage has to be done typically between a coasting and when acceleration is required typically after an interstage separation. Something like how we hit the back of the seat when we accelerate the car.

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Re: Indian Space Programme Discussion

Postby member_28108 » 17 Dec 2014 18:21


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Re: Indian Space Programme Discussion

Postby member_28108 » 17 Dec 2014 18:22

Dec 17, 2014
N2O4 propellant filling operation of Second Stage - L110 is completed by 17:15 hrs (IST)
N2O4 propellant filling operation of Second Stage - L110 has commenced at 15:30 hrs (IST) and under progress
UH25 propellant filling operation of Second Stage - L110 is completed by 13:00 hrs (IST)
UH25 propellant filling operation of Second Stage - L110 is under progress
24 and a half hour countdown for the mission has commenced at 09:00 hrs (IST) on Dec 17, 2014
Dec 16, 2014
24 and a half hour countdown for the mission will commence at 09:00 hrs (IST) on Dec 17, 2014
Mission Readiness Review (MRR) and Launch Authorisation Board (LAB) met on Dec 16, 2014 to review progress of prelaunch activities and cleared launch for Dec 18, 2014 at 09:30 hrs (IST)


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Re: Indian Space Programme Discussion

Postby KrishG » 17 Dec 2014 19:05

Vehicle Assembly! 8)


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Re: Indian Space Programme Discussion

Postby Varoon Shekhar » 17 Dec 2014 19:55



Excellent, detailed information. In the next few days and weeks, they should talk about the various technological and/or engineering challenges that had to be overcome, in the building of the GSLV Mark 3. The L-110, with 4.2 diameter, and two engines, must have presented a significant challenge, as would have the S-200( this was mentioned years earlier, as being the tougher task) boosters. The heat shield or payload fairing with a greater width( 5m?), plus as the article refers, the various stage separation systems, nozzles et al, would have been challenging.

Without divulging trade secrets, they should go into this into a little more detail! Even with the Mark 2, I don't recall reading an article about the difficulty in developing 3 different turbo pumps( main+ fuel and oxidiser), making them work together, all the seals, bearings, materials et al that had to be manufactured. They could have made a general statement to this effect, something that lay readers could understand.

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Re: Indian Space Programme Discussion

Postby member_28108 » 17 Dec 2014 21:44

Dec 11, 2014
The solar arrays and antenna reflectors of GSAT-16 spacecraft are successfully deployed by 17:30 hrs (IST) on Dec 10, 2014.

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Re: Indian Space Programme Discussion

Postby member_28108 » 17 Dec 2014 21:45

Image

Unfortunately cant watch it but hope for updates on twitter and BR

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Re: Indian Space Programme Discussion

Postby Dilbu » 17 Dec 2014 22:29

GSLV will fail onlee. :(( :(( :((

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Re: Indian Space Programme Discussion

Postby vina » 17 Dec 2014 22:47

Hmm. To me, it seems that ISRO has done something new and innovative with the CE-25 crogenic stage. something that has not been done anywhere else as far as I can see. I will come to that in a bit.

The thing about all this separation and "slosh" and "ullage" / whatever ,bit is this. As long as the the engines are firing, there is a clear liquid surface that is formed (the cork floats in the water), and there is no issue what so ever. So what happens when the thrust is turned off for whatever reason ? The vehicle is coasting under it's own inertia under the effect of earth's gravity. In effect, this is in Free Fall. From high school physics, we know that a freely falling body (like the rocket in this condition, or approximately when we are in a roller coaster /giant wheel in it's downward leg as most kids know and feel, or a satellite in orbit) is weightless (this is not either microgravity or g = 0) . Now under conditions of weightlessness (ie coast with engines off in a rocket), the liquid fuel , since it is now weightless, will have surface tension effects predominating ( like the photos and videos we are all familiar with of water forming into spheres in space etc..and no, you dont need to go to "Vomit Comet" to do that, just putting a plane into a free fall and holding a cup of water will make that happen).

So obviously in such conditions, if you want to start the liquid engine (either for the first time if staging, or restarting while coasting), you need to find someway of making the liquid fuel behave "normally" like in a non weightless condition. The easiest way is to give it a momentary acceleration and the surface is instantly formed again and the liquid is as "normal". You can have things like springs separating the stages giving the "kick" (heavy, inefficient,can be done once), or you can have ullage motors, small motors that give the same small kick (either solids or gas based jets etc) , or if you really want multiple starts more complex schemes like confining some of the fuel and oxidizer into small tanks that are kept full and then pressure fed into the chamber etc.

How does all this work in practice ? There are two ways to go about it. ie ensuring that the thrust is always on, and you have ullage problem in the first place and the second is to manage the ullage. During stage separation , this gives rise to two schemes, a) Parallel staging, where there is an overlap in the of the firing of the two stages so that thrust is always on b) Tandem staging , where the previous stage gets separated , the vehicle coasts for a few seconds and then the next stage fires when there is enough separation between the spent stage and the vehicle.

Now in the lower strap on booster stages, the parallel staging is quite obvious. There is overlap in firing, thrust is always on, and the core stage (even if liquid like in the Ariane V) fires even in mid air without any issues. It is in the 2nd stage and higher that is interesting. The Russians went about it with their R7 / Soyuz and derivatives very elegantly. They basically put the inter-stage in a truss, so that they could simply fire the next stage engine (the exhaust flows out through the space truss) , just as the previous stage engine tails off and the stage separates "hot" , and you achieve parallel staging and avoid the ullage business totally during separation. In addition, you have enough control forces at hand since the engines are thrusting to control the vehicle.

The Chinese Long March (the blow up diagram of their launch sequence is interesting) and our GSLV MK2 in the cryogenic stage and also our Agni missiles use the R7/Soyuz kind of staging. That is the reason the GSVL Mk1/2 wont need separation motors for their cryogenic stage. The American vehicles, like Saturn V had mostly tandem staging (as they had a solid skirt in their inter stages)and would have needed separation motors during staging and it would needed a few seconds gap for the bell/nozzle of the stage to clear the skirt before the next stage could fire.

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Re: Indian Space Programme Discussion

Postby shravanp » 17 Dec 2014 22:58

Dilbu wrote:GSLV will fail onlee. :(( :(( :((



Finally Dilbu saar is here. This mission is as critical as LS elections.

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Re: Indian Space Programme Discussion

Postby vina » 17 Dec 2014 22:58

What is the innovative thing that ISRO have done with the CE-25?
Image

Look at this picture.The truss is not at interstage, where the nozzle is, and if you see the see-thorough diagram in the brochure, you can see that the bell/nozzle actually sits in a solid circular interstage skirt and they do have separation motors to initiate the stage separation for the CE-25/LM110 .

From the picture, it is very clear that there is no external skin /shell for the CE-25!. There is a ring at the bottom, on which a smaller tank (LOX?) is supported and the truss frame encloses the smaller tank, and then the larger tank (LH2?) sits on the truss frame . The ISRO logo and the LVM3 Flight logo are painted on the larger tank itself! No outer shell at all! And then right on top, there is another ring, which supports the payload and avionics bay, and that is supported by just the grey pillar that connects it to the lower truss.

Pretty unique and quite innovative structural design . It completely eliminates the shell of the stage. (and hence also the weight of that shell). I haven't see it in any other launch vehicle so far. Kudos!

If only they get rid of the WeakAss engines and get in the LOX/hydrocarbon stage ASAP :roll: :roll:

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Re: Indian Space Programme Discussion

Postby member_28911 » 17 Dec 2014 23:32

Image

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Re: Indian Space Programme Discussion

Postby Praveen » 17 Dec 2014 23:58

KrishG wrote:Vehicle Assembly! 8)



Around 1:40 minutes into the video, the weight of CARE is shown as 4140.90 Kg while the ISRO's launch kit says that CARE Launch weight is 3735 Kg. Which is right?

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Re: Indian Space Programme Discussion

Postby disha » 18 Dec 2014 03:24

vina wrote:From the picture, it is very clear that there is no external skin /shell for the CE-25!. There is a ring at the bottom, on which a smaller tank (LOX?) is supported and the truss frame encloses the smaller tank, and then the larger tank (LH2?) sits on the truss frame . The ISRO logo and the LVM3 Flight logo are painted on the larger tank itself! No outer shell at all! And then right on top, there is another ring, which supports the payload and avionics bay, and that is supported by just the grey pillar that connects it to the lower truss.

Pretty unique and quite innovative structural design . It completely eliminates the shell of the stage. (and hence also the weight of that shell). I haven't see it in any other launch vehicle so far. Kudos!


And that I agree. I was wondering the same thing and shaking my head - "is that what they have done? :shock: " - that is a bold move and very confident on their tank design, structure, heat management and I hope that is the case for the final version and not just the case for LVM3 since it carries liquid N2 only.

There is another reason of seeing truss'es in new generation rockets., the material tech and computer simulations have advanced enough that the trusses cane be made strong to withstand aerodynamic loads but "weak" enough to be cut and separated. A similar case was made using vent holes. But then vent holes have a good ability to go out of control and burn up the cables.

If only they get rid of the WeakAss engines and get in the LOX/hydrocarbon stage ASAP :roll: :roll:


Now now - on that part., the LOX/HC engines are useless. ISRO can dabble in it to gain technology expertise., however ISRO should concentrate on scaling up the CE7.5 (the staged combustion engine) and also the CE25 (the gas generator engine) and clustering the "weakass" engines to make it more powerful. And of course scaling up on their solid stage boosters (they are almost there, putting soon the second largest operational booster and the largest in Asia).

Once they are done with the above., India will effectively have a moon rocket. Far earlier than the Chinese or the Russian ones. (And you heard it here first).

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Re: Indian Space Programme Discussion

Postby member_28108 » 18 Dec 2014 06:53

Einstein summarized the results of his reasoning in his Principle of Equivalence, which can be stated thus:
All experiments will give the same results in a local frame of reference in free fall and in a local frame of reference far removed from gravitational influences.

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Re: Indian Space Programme Discussion

Postby shaun » 18 Dec 2014 07:22

Godspeed CARE !!

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Re: Indian Space Programme Discussion

Postby Victor » 18 Dec 2014 07:56

Live on Youtube

Wonder why it has that exposed part between stages. Little nervous about airflow disturbance but maybe it will be jettisoned soon enough not to be a problem.

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Re: Indian Space Programme Discussion

Postby Dilbu » 18 Dec 2014 08:10

GSLV will fail onlee. :(( :(( :((

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Re: Indian Space Programme Discussion

Postby member_28108 » 18 Dec 2014 08:17

What time is the launch scheduled?

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Re: Indian Space Programme Discussion

Postby symontk » 18 Dec 2014 08:19

Best of luck to ISRO and its scientists

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Re: Indian Space Programme Discussion

Postby shaun » 18 Dec 2014 08:19

9:30 ist

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Re: Indian Space Programme Discussion

Postby member_28714 » 18 Dec 2014 08:30

symontk wrote:
skekatpuray wrote:Those could be vernier boosters.


I think its for thurst vectoring, I could be wrong too



The commentry just said those two smaller rocket attached to the boosters are to assist with booster ejection

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Re: Indian Space Programme Discussion

Postby Victor » 18 Dec 2014 08:41

Many people suddenly left the viewing gallery? Maybe they want to see the launch from outside.

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Re: Indian Space Programme Discussion

Postby Victor » 18 Dec 2014 08:44

Liftoff.

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Re: Indian Space Programme Discussion

Postby dinesha » 18 Dec 2014 08:49

Congratulations to ISRO & all of us.

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Re: Indian Space Programme Discussion

Postby dinesha » 18 Dec 2014 08:51

CARE separated..

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Re: Indian Space Programme Discussion

Postby Suraj » 18 Dec 2014 08:51

Twitter:

ISRO @isro · 1m 1 minute ago

LVM3 X / CARE Mission Update: Heat shield separated successfully.
0 replies 37 retweets 27 favorites
ISRO @isro · 3m 3 minutes ago

LVM3 X / CARE Mission Update: L110 stage performance normal.
0 replies 50 retweets 27 favorites
ISRO @isro · 4m 4 minutes ago

LVM3 X / CARE Mission Update: S200 stage performance normal.
0 replies 53 retweets 32 favorites
ISRO @isro · 5m 5 minutes ago

LVM3 X / CARE Mission Update: Lift off normal.
0 replies 99 retweets 36 favorites

ADDED

LVM3 X / CARE Mission Update: L110 stage separated.

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Re: Indian Space Programme Discussion

Postby symontk » 18 Dec 2014 08:51

George wrote:

The commentry just said those two smaller rocket attached to the boosters are to assist with booster ejection


Understandable as the S-200 is thrust vectoring, and there are several new advancements being tested for first time

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Re: Indian Space Programme Discussion

Postby Suraj » 18 Dec 2014 08:52

LVM3 X / CARE Mission Update: CARE module separated and started its descent.

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Re: Indian Space Programme Discussion

Postby Pratyush » 18 Dec 2014 08:53

Fingers crossed for a successful orbital insertion.

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Re: Indian Space Programme Discussion

Postby Suraj » 18 Dec 2014 08:53

ISRO @isro · 3s 4 seconds ago

LVM3 X / CARE Mission Update: CARE module in its tense atmospheric re-entry.

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Re: Indian Space Programme Discussion

Postby Suraj » 18 Dec 2014 08:54

[youtube]pD0RtxuGxug&feature=player_detailpage#t=1537[/youtube]
Launch begins at 25:40

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Re: Indian Space Programme Discussion

Postby dinesha » 18 Dec 2014 08:56

Main Para deployed..

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Re: Indian Space Programme Discussion

Postby Victor » 18 Dec 2014 08:57

DD should have had a camera on the CG boats. But well done ISRO, hearty congrats.

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Re: Indian Space Programme Discussion

Postby member_28911 » 18 Dec 2014 08:57

Image


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