Author Topic: PSLV design  (Read 3822 times)

Offline vineethgk

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PSLV design
« on: 04/27/2016 07:35 AM »
There is a pretty generic PSLV question that has been in my mind for some time. Since it pertained to the fundamental design of the vehicle, I thought I might try opening a new thread for it, and for any related discussion on the PSLV design. Please do let me know if you feel there is an existing thread that serves the same purpose.  :)

Here we go...

Why did ISRO go for a solid PS3 stage right after a liquid PS2? (since my understanding is that solids would incur a weight penalty if used as upper stages, correct me if I'm wrong..) Was it the absence of a suitable of liquid engine of required thrust or performance? Or was it some specific thrust requirements that could be best met by a solid stage as against a liquid one?

Thanks in advance..

Offline K210

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Re: PSLV design
« Reply #1 on: 04/27/2016 09:33 AM »
In ISRO's book "From fishing hamlet to mars" its stated the reason for this is there were more people in ISRO in favour of solid fuel against liquid fuel at that time. Fourth stage of pslv was also supposed to be solid fuel but that didnt work out because the vehicle would not be able to deliver the necessary velocity. Hence they were forced to develop the L-2 stage which eventually became the L2.5 stage we have today.

At that point in time ISROs main goal was to make a vehicle that worked even if it was not very efficient.

Offline rocx

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Re: PSLV design
« Reply #2 on: 04/27/2016 11:28 AM »
And if you're not so certain about your technological capabilities, solids upper stages have the advantage over liquids that airstart is a whole lot easier.
Any day with a rocket landing is a fantastic day.

Offline vineethgk

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Re: PSLV design
« Reply #3 on: 04/27/2016 11:31 AM »
Thanks a lot, K210... I did not realise that the book had so much of details regarding the development history of ISRO's launch vehicles. Its a shame I did not read it earlier. My bad..

Sent from my ASUS_Z010D using Tapatalk


Offline vineethgk

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Re: PSLV design
« Reply #4 on: 01/10/2017 07:55 AM »
Does anyone know the reason why the PS4 stage in PSLV sits right inside the payload fairing? Was it a weight saving measure? And I believe that is the reason why, in the case of PSLV, the payload has to be taken into the vehicle assembly building and integrated with the PS4 and payload fairing in situ after the rest of the rocket is assembled? In the case of GSLV, the payload is enclosed within the fairing in a different processing room, and the integrated whole is taken to the vehicle assembly where it is lifted and placed on the stack.

Offline hkultala

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Re: PSLV design
« Reply #5 on: 01/10/2017 08:14 AM »
Does anyone know the reason why the PS4 stage in PSLV sits right inside the payload fairing? Was it a weight saving measure?

Just look at your picture again. What other reasonable options would there be when the tank is so small?

Offline vineethgk

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Re: PSLV design
« Reply #6 on: 01/10/2017 08:23 AM »
Does anyone know the reason why the PS4 stage in PSLV sits right inside the payload fairing? Was it a weight saving measure?

Just look at your picture again. What other reasonable options would there be when the tank is so small?
I must admit I'm a perfect noob when it comes to principles of LV design. But is it usual for the rockets with smaller upper stages to have them within the payload fairing rather than as a separate unit? I mean, the problem I see here is that you would need to have real clean room in the vehicle assembly building so that they can enclose the payload within the payload fairing there.

Offline Welsh Dragon

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Re: PSLV design
« Reply #7 on: 01/10/2017 10:37 AM »
Atlas V 5 m versions have half the Centaur in the fairing, Star 48 on Delta II was/is, Waxwing was on Black Arrow, and I'm pretty sure there's been more small solid upper stages in the fairing in early rockets.
« Last Edit: 01/10/2017 10:54 AM by Welsh Dragon »

Offline vineethgk

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Re: PSLV design
« Reply #8 on: 01/10/2017 11:24 AM »
Atlas V 5 m versions have half the Centaur in the fairing, Star 48 on Delta II was/is, Waxwing was on Black Arrow, and I'm pretty sure there's been more small solid upper stages in the fairing in early rockets.
Ah.. I see.. Thanks. But are those upper stages mentioned above optional or an integral part of the LV configuration? PS4 has been an integral part of PSLV, that's why..

Offline Welsh Dragon

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Re: PSLV design
« Reply #9 on: 01/10/2017 12:51 PM »
Integral for Atlas and Black Arrow, optional for Delta II

Offline baldusi

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Re: PSLV design
« Reply #10 on: 01/10/2017 06:24 PM »
Look at how Soyuz integrates the Fregat or Proton the Briz-M or Blok-D.

Offline edkyle99

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Re: PSLV design
« Reply #11 on: 01/10/2017 06:34 PM »
I must admit I'm a perfect noob when it comes to principles of LV design. But is it usual for the rockets with smaller upper stages to have them within the payload fairing rather than as a separate unit? I mean, the problem I see here is that you would need to have real clean room in the vehicle assembly building so that they can enclose the payload within the payload fairing there.
By "hanging" or otherwise supporting a stage inside the fairing, its dry mass can be reduced.  This is because load paths transfer away from the stage to the fairing.  Since the fairing is jettisoned during relatively early phases of flight, the mass penalty is minimized.  On the other hand, reduction of dry mass on a final, insertion stage pays off on a 1 to 1 basis, each kg shaved from the stage is one more kg of possible payload.

The other obvious benefit is that larger fairings, necessary given today's payloads, become easier with such a configuration.  Loads on an integral stage tank wall would be more complex with a hammerhead fairing, because they would involve not only structural loads, but also complex aerodynamic loads.

 - Ed Kyle
« Last Edit: 01/10/2017 06:37 PM by edkyle99 »

Offline vineethgk

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Re: PSLV design
« Reply #12 on: 01/10/2017 07:03 PM »
Look at how Soyuz integrates the Fregat or Proton the Briz-M or Blok-D.
Okay. But the impression I had was that unlike PS4 stage, the Fregat, Briz and Blok-D were more like 'optional' upper stages for specific orbital requirements rather than being an integral part of the launch vehicle stack itself, and hence were often counted as part of the payload for the rocket (correct me if I'm wrong here). Perhaps, its more of how the rocket manufacturers choose to look at it, rather than technical differences.

Thanks everyone for the clarification, anyways!

Offline A.K.

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Re: PSLV design
« Reply #13 on: 01/11/2017 06:54 AM »
Although development of Heavy lift launchers are important, we also need Agni V based launch system & 500 kg payload variant of PSLV to remain competent in the launch market.

Offline vineethgk

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Re: PSLV design
« Reply #14 on: 01/11/2017 07:06 AM »
Although development of Heavy lift launchers are important, we also need Agni V based launch system & 500 kg payload variant of PSLV to remain competent in the launch market.
As depicted in the picture, ISRO did a study on a 3 stage variant of PSLV omitting PS2 to handle payloads to the tune of 500 kg. But they concluded that it did not provide significant cost benefits.

As for Agni-V, it may have satellite launch capability with a small upper stage. But as it is a DRDO project, I do not see ISRO dabbling with it as they would consider the segregation of civilian and military space activities vital for its international relations. At best, DRDO may use it internally for their smaller payloads.

Offline sanjaykumar

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Re: PSLV design
« Reply #15 on: 01/11/2017 11:27 PM »
There should be additional rows to show what would be pay load capacity when PSLV is launched from Kulasekarapattinam instead of SDSC Shar.

« Last Edit: 01/11/2017 11:28 PM by sanjaykumar »

Offline vineethgk

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Re: PSLV design
« Reply #16 on: 01/30/2017 01:44 PM »
Yet another PSLV launcher question that has been floating around my mind. PSLV's (and GSLV's) S-139 solid motors are composed of 5 segments, while GSLV-III's newer (and larger) S-200 is composed of only 3. Wouldn't it save ISRO technicians valuable time in stage integration if the S-139 segments were to be redesigned to make them larger, so that the fully assembled motor would be simpler, say of 2 segments ? (Or maybe even attempt to make it a single segment motor like the P-120 Europeans plan for Ariane 6 and the new Vega, though it might be far more challenging.) Apparently, they did manage to make larger segments for S-200 in any case.

Or would the added cost or the  risk of change in vehicle characteristics negate any advantages of such a move?
« Last Edit: 01/30/2017 01:49 PM by vineethgk »

Offline baldusi

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Re: PSLV design
« Reply #17 on: 01/30/2017 04:02 PM »
Yet another PSLV launcher question that has been floating around my mind. PSLV's (and GSLV's) S-139 solid motors are composed of 5 segments, while GSLV-III's newer (and larger) S-200 is composed of only 3. Wouldn't it save ISRO technicians valuable time in stage integration if the S-139 segments were to be redesigned to make them larger, so that the fully assembled motor would be simpler, say of 2 segments ? (Or maybe even attempt to make it a single segment motor like the P-120 Europeans plan for Ariane 6 and the new Vega, though it might be far more challenging.) Apparently, they did manage to make larger segments for S-200 in any case.

Or would the added cost or the  risk of change in vehicle characteristics negate any advantages of such a move?

It's not so much the design as the tooling cost. Solids require a mold of its size, plus a die to give it the center grain (hole), and a mixed and filler that pours to very exacting standards. So it would be much more easier to make a new rocket based on the S200 than try to redo the S-139.
Please remember that the GSLV MkI/II was a kludge that maximized the use of PSLV parts. It is now (thankfully) going away with the LVM3. The next step, at least publicly, is to replace the core of the LVM3 with an SCE-200 based kerolox core. That same core, without the S200, will replace the PSLV.
The only issue I see with that plan is that they are planning to scale by having something like four different SRB. So, depending on the required performance, they could select S12, S60, S139 or S200 for the required payload capacity. Personally, I would go with the EELV approach and simply do a single S85 and use 0 to 6. With that you would have a single vehicle to replace PSLV, GSLV and VLM3.

Offline s^3

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Re: PSLV design
« Reply #18 on: 02/27/2017 01:30 PM »
A lot of inside info by this blogger in 15 days of existence.

http://www.spansen.com/2017/02/pslv-stage-separation-case-for-launch.html


Offline vineethgk

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Re: PSLV design
« Reply #19 on: 02/27/2017 03:00 PM »
ISRO's story of the week on the realization of the 50th HPS3 motor case

Quote
PSLV uses a solid motor in its third stage (PS3), which is of 2 m diameter and 4850 litre capacity. PS3 motor case weighing 325 kg was initially realised by filament winding process using Aramid/Epoxy for the construction for the shell and Carbon/Aramid/Epoxy hybrid construction for the skirt extension. Four numbers of PS3 motor cases were burst tested and gave more insight into the processing and design of composite motor case. It was observed that polar winding potential was underutilised due to non-uniform stress distribution and unequal opening, high boss opening ratio and fast-indexed multi star pattern in polar winding. Hence the design and processing parameters of PS3 motor case were optimised to augment the payload capacity of PSLV to meet the future requirements of ISRO.

High Performance motor case (HPS3) is the improved version of PS3 motor case. An optimum design for this was evolved by selecting appropriate different profiles for both the domes, introducing dome reinforcements and adopting modified helical winding with wide band in multi axis filament winding machine. 

Quite a bit of additional technical info and images on it.


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