Indian Space Programme Discussion - Sept 2016

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Re: Indian Space Programme Discussion - Sept 2016

Postby abhik » 02 Jan 2018 12:25

symontk wrote:
abhik wrote:What you are saying is that they can get the same performance of pslv-3s by not only removing the 2nd liquid stage (as in the 3s) but also removing over half of the existing first stage AND not using composite casing for the middle solid - what gives? If this works then they can probably remove the 2nd stage liquid stage in the CA version and replace the 3rd stage solid with a larger solid and still get the same performance?


The proposed Second stage is a new thing and without expensive or extensive testing, it will not fly. I presume ISRO will continue with proven PS3

1 stage - S60
2 stage - PS3 - improved ??
3 stage - PS4 - improved ??

I am also skeptical about reusing PSLV lower stage in truncated form, and new 2nd stage derived from S139.

IMO ISRO should not be chasing after commertial launch market and rather concentrate on rusability, the money that the commertial launches brings is honestly penuts in the long term.

Edit: added quote

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Re: Indian Space Programme Discussion - Sept 2016

Postby Haridas » 02 Jan 2018 12:30

Indranil wrote:Well we don't have anything between the PSOMs and S139, so for a 100 ton rocket a new stage has to be built..
Is it new or modified depends on glass half full, as the booster is segmented and increasing or decreasing segments is evolutionary not revolutionary.
The 2.8 mtr dia is very interesting (if true). It allows reuse of tooling and process, but we are speaking of a very short and fat rocket. The entire rocket is as fat as the PSLV, but only as tall as its first stage!

I hope the second and third stage have a lower diameter.
What is you concern ? Controllability ? I say that is easier than slender SLV 20m long.
or drag loss? I say that is minor ISP loss in overall energy budget.

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Re: Indian Space Programme Discussion - Sept 2016

Postby Prem » 03 Jan 2018 01:10


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Re: Indian Space Programme Discussion - Sept 2016

Postby Indranil » 03 Jan 2018 06:46

Haridas wrote:What is you concern ? Controllability ? I say that is easier than slender SLV 20m long.
or drag loss? I say that is minor ISP loss in overall energy budget.

It is not a concern. SLBM/ICBMs use similar aspect ratio, so controllability is not an issue. But the atmosphere is not kind to short and stalking things trying to move very fast through it. SLBMs as I sustpect you already know often use aerospikes to overcome this limitation, and the outcome is not insignificant.

For me the bigger mystery for the smaller diameter of the upper stage diameter of PSLV, is why did not ISRO go for two S130s as booster and a single Vikas engine as the core. Or Just go for 3 S130s as the first stage. Yeah the mass fraction would be lower, but can't be by much. Atleast there is no lugging of 30 tons for 50 seconds!

I am sure there are very good reasons why ISRO is doing something. I hope that they design the S60 stage to be the first stage of the mini rocket and booster stage for other rockets. So a thrust of 2500-3000kN and burn time of 60-70 seconds would be great IMHO.

GSLV Mk3 core with S60, S139 or S200 could become our first ULV. PSLV-CA, PSLV-XL, PSLV-XXL (with 2 or 4 S60 boosters) can give us the cheaper lower end of the spectrum.

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Re: Indian Space Programme Discussion - Sept 2016

Postby Haridas » 03 Jan 2018 08:19

Indranil wrote:It is not a concern. SLBM/ICBMs use similar aspect ratio, so controllability is not an issue. But the atmosphere is not kind to short and stalking things trying to move very fast through it. SLBMs as I sustpect you already know often use aerospikes to overcome this limitation, and the outcome is not insignificant.
Sure, but this craft will sport a treaditional payload faring with non-blunt shape (unlike space constrained SLBM). Further there is no need for the palatial roomy PSLV nose cone, but one that is smaller & suitable for 700 kg payload sitting atop the smaller diameter upper stage.
For me the bigger mystery for the smaller diameter of the upper stage diameter of PSLV, is why did not ISRO go for two S130s as booster and a single Vikas engine as the core. Or Just go for 3 S130s as the first stage. Yeah the mass fraction would be lower, but can't be by much. Atleast there is no lugging of 30 tons for 50 seconds!
ISRO was on serious pressure to deliver a reasonable heavy payload to SSO, they put all stages to not ruffle the feather and have team play. My hunch was that S3 stage was for dual use purpose (before the western pressure forced ISRO to stay kosher to western definition, but by then the 2 m composite case was done and ready). The lugging issue is on GSLV :!: .
I hope that they design the S60 stage to be the first stage of the mini rocket and booster stage for other rockets. So a thrust of 2500-3000kN and burn time of 60-70 seconds would be great IMHO.
60 sec burn will only give 220 tonne avg thrust.
GSLV Mk3 core with S60, S139 or S200 could become our first ULV. PSLV-CA, PSLV-XL, PSLV-XXL (with 2 or 4 S60 boosters) can give us the cheaper lower end of the spectrum.
Reminds me of old BR-Space section page on GSLV config options :twisted: Why no worthy updates the space section page?
Last edited by Haridas on 03 Jan 2018 11:11, edited 1 time in total.

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Re: Indian Space Programme Discussion - Sept 2016

Postby sivab » 03 Jan 2018 10:17

Haridas wrote: Reminds me of old BR-Space section page on GSLV config options :twisted: Why no worthy updates the space section page?


As you should know very well, they were pulled out of nether regions just like those giga booms. They had nothing to do with GSLV or Indian space program. Good thing hakim chased those away. :rotfl:

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Re: Indian Space Programme Discussion - Sept 2016

Postby Haridas » 03 Jan 2018 10:44

Ha ha.. :lol: hakim saab eating crow with all the non existance MIRV Mijjiles configs of India coming into reality from public sources :rotfl: I also now see hakim has opened design your own nuke bum dukaan under MBBS hakim tutalege. ;) funny, but that is out of scope of this thread.
Last edited by Haridas on 03 Jan 2018 11:12, edited 1 time in total.

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Re: Indian Space Programme Discussion - Sept 2016

Postby Indranil » 03 Jan 2018 11:12

Haridas wrote:Sure, but this craft will sport a treaditional payload faring with non-blunt shape (unlike space constrained SLBM). Further there is no need for the palatial roomy PSLV nose cone, but one that is smaller & suitable for 700 kg payload sitting atop the smaller diameter upper stage.

Of course. So your view of the rocket is 10 mtr-2.8 mtr dia first stage (S-60) tapering into a ~6 mtr-2.0 dia second stage (S-24), followed by liquid / solid third stage 2.0 mtr dia, followed by a fairing with a pointed nose.
Haridas wrote:
For me the bigger mystery for the smaller diameter of the upper stage diameter of PSLV, is why did not ISRO go for two S130s as booster and a single Vikas engine as the core. Or Just go for 3 S130s as the first stage. Yeah the mass fraction would be lower, but can't be by much. Atleast there is no lugging of 30 tons for 50 seconds!
ISRO was on serious pressure to deliver a reasonable heavy payload to SSO, they put all stages to not ruffle the feather and have team play. My hunch was that S3 stage was for dual use purpose (before the western pressure forced ISRO to stay kosher to western definition, but by then the 2 m composite case was done and ready). The lugging issue is on GSLV not PSLV.

I meant the GSLV onlee.

By they way, on the PSLV-CA, they sacrifice 400 kgs of fuel in fourth stage too. Makes me wonder of a PSLV-XXL version wherein the first stage is augmented by two S60s instead of 6 PSOMs, and the diameter of the 3rd stage is increased to 2.8 mtrs.
Haridas wrote: 60 sec burn will only give 220 tonne avg thrust.

Why such low average ISP?
Haridas wrote:
GSLV Mk3 core with S60, S139 or S200 could become our first ULV. PSLV-CA, PSLV-XL, PSLV-XXL (with 2 or 4 S60 boosters) can give us the cheaper lower end of the spectrum.
Reminds me of old BR-Space section page on GSLV config options :twisted: Why no worthy updates the space section page?

Let jingoes have some fun. :wink:

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Re: Indian Space Programme Discussion - Sept 2016

Postby Haridas » 03 Jan 2018 11:30

Indranil wrote:Of course. So your view of the rocket is 10 mtr-2.8 mtr dia first stage (S-60) tapering into a ~6 mtr-2.0 dia second stage (S-24), followed by liquid / solid third stage 2.0 mtr dia, followed by a fairing with a pointed nose.
I think 2.8m dia second stage is more likely compared to 2m dia stage. Upper stage more likely 1.5 dia, same as faring. Jmt.
By they way, on the PSLV-CA, they sacrifice 400 kgs of fuel in fourth stage too.
thanks, didn't know. so kind of support my assertion.
Makes me wonder of a PSLV-XXL version wherein the first stage is augmented by two S60s of 6 PSOMs, and the diameter of the 3rd stage is increased to 2.8 mtrs.
yes quite a likely way to evolve a successful platform.
Why such low average ISP?
all isro boosters at sea level have lower ISP that improves at higher altitude.

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Re: Indian Space Programme Discussion - Sept 2016

Postby sivab » 03 Jan 2018 21:30

Haridas wrote:Ha ha.. :lol: hakim saab eating crow with all the non existance MIRV Mijjiles configs of India coming into reality from public sources :rotfl: I also now see hakim has opened design your own nuke bum dukaan under MBBS hakim tutalege. ;) funny, but that is out of scope of this thread.


Interesting! seems something personal between you and hakim.

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Re: Indian Space Programme Discussion - Sept 2016

Postby SSridhar » 04 Jan 2018 06:56

sivab & Haridas, let's confine the discussion to matters on hand. Nothing extraneous.

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Re: Indian Space Programme Discussion - Sept 2016

Postby VickyAvinash » 04 Jan 2018 09:02

OT Alert:
Haridas sir, are you Arun S. If yes, it is great to have you back as it was always pleasure to read your knowledgeable posts. If not, kindly ignore this.

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Re: Indian Space Programme Discussion - Sept 2016

Postby abhik » 05 Jan 2018 00:00

TNIE: ISRO’s baby rocket to carry small satellites, likely to take off in 2019
Some new info (I hope)
> All Solid Stages
> 20-25m height
> The name Small Satellite Launch Vehicle (SSLV) is probably going to stick

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Re: Indian Space Programme Discussion - Sept 2016

Postby Indranil » 05 Jan 2018 00:12

Haridas ji,

You may be right. A 100 tonner of 20-25 mtr height has to have a diameter 2.5-2.8 mtrs. Whether they go ab-initio (2.5 mtrs) or S-139-- like you say has to be seen.

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Re: Indian Space Programme Discussion - Sept 2016

Postby Haridas » 05 Jan 2018 07:42

^^^ Seems to be converging. I see that fatter diameter is generally more MF efficient and scalable. As for 2.5m dia, dont see the drastic advantage, given that a nearby diameter is mastered and tooled up. Yes if dia has to change for say SLBM then all money used is good use.

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Re: Indian Space Programme Discussion - Sept 2016

Postby prasannasimha » 05 Jan 2018 09:08

It had to be all solid to decrease fueling time etc on the launch pad if they want a launch campaign of 3 days

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Re: Indian Space Programme Discussion - Sept 2016

Postby arun » 05 Jan 2018 10:41

abhik wrote:Isro's plan: A rocket that can be made in 3 days
As per this ISRO is developing a 100t launcher which will cost "1/10 of original manufacturing cost of PSLV", payload of 500-700kg and will be ready to launch by end of 2018 or early 2019. Was there reports of this earlier or did ISRO just pull a rabbit out of the hat?


abhik wrote:TNIE: ISRO’s baby rocket to carry small satellites, likely to take off in 2019
Some new info (I hope)
> All Solid Stages
> 20-25m height
> The name Small Satellite Launch Vehicle (SSLV) is probably going to stick


Comes across as an ISRO version of the Japan Aerospace eXploration Agency (JAXA) Epsilon Launch Vehicle {ELV Clicky} which is set for next launch on Jan 17 {E-3 Launch Clicky} and rumoured to be a wolf in sheep’s clothing as some believe it is the template for a Japanese ICBM { The Next-Generation Rockets That Japan Could Use To Protect Itself}.

So with that it in mind, is the SSLV also a wolf in sheep’s clothing and a template for an Indian ICBM?

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Re: Indian Space Programme Discussion - Sept 2016

Postby Haridas » 05 Jan 2018 11:37

prasannasimha wrote:It had to be all solid to decrease fueling time etc on the launch pad if they want a launch campaign of 3 days

Really depends on required precision for orbital insertion. Liquid upper stage allows for higher ISP and velocity correction due to solid fuel stages that inherently having appreciable V dispersion (just the very nature of solid stage).

The upper stage fuelling of PSLV is very different from the PS2 Vikas stage. It requires Helium pressurization and relatively less fuel. So may not contribute significantly to launch campaign duration.

All solid is also possible where cartridges provide Delta-V, or use Nano-satellite bus (liquid fuelled) that provide controlled insertion of nano-sats. reverse knowledge xfr from military BM rockets.

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Re: Indian Space Programme Discussion - Sept 2016

Postby Indranil » 05 Jan 2018 12:36

Agni5++ was the direction that I was initially thinking of when I was speaking of a rocket with a two meters dia. Additionally, they had already solved the problem of precise insertion using a solid upper stage there.

But such a rocket will have a length of at least 35 mtrs or more. A 20-25 mtr rocket has to have a wider girth.

It is not just Japan, the French SLBMs are also adaptations of its booster rockets. Our first Agnis were also derived from ISRO rocket stages IIRC. But, I don’t think our SLBMs will be derived from this for two reasons:
1. Agni-6 and K-5 have already been designed and probably a specimen or two already built.
2. Our SLBM tubes have a 2 mtr dia IIRC.

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Re: Indian Space Programme Discussion - Sept 2016

Postby abhik » 05 Jan 2018 14:03

arun wrote:...
So with that it in mind, is the SSLV also a wolf in sheep’s clothing and a template for an Indian ICBM?

Might be too heavy (and inefficient?) for an ICBM but I think something like this will be useful for a higher end ASAT (whenever we decide to develop it :| )

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Re: Indian Space Programme Discussion - Sept 2016

Postby Indranil » 06 Jan 2018 01:15

Haridas ji,

Jaxa's Epsilon drove me to read a bit more about the H-IIB. Epsilon's first stage is H-IIB's booster (SRB-A3). SRB-A3 burns 66 tons of HTPB to produce a a thrust of 230 tons for 114 seconds. In our earlier discussion, you suggested that the proposed Indian equivalent would provide an equivalent thrust for 60 seconds only. I don't believe that the Indian solid rockets have half the Isp of the Japanese ones. For example, S139 uses 139 tons to provide 486 tons of thrust for 105 seconds, (i.e. off by about 8%).

I am genuinely interested to know the payload capacity of:
1. GSLV MkIII lift with 2 S139s instead of two S200s,
2. GSLV MkIII lift with 2 S60s instead of two S200s,
3. GSLV MkII with 4 S60s instead of the LH40s. Delay the ignition of the core to T0 +50 seconds.

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Re: Indian Space Programme Discussion - Sept 2016

Postby disha » 06 Jan 2018 02:37

arun wrote:
abhik wrote:Isro's plan: A rocket that can be made in 3 days
As per this ISRO is developing a 100t launcher which will cost "1/10 of original manufacturing cost of PSLV", payload of 500-700kg and will be ready to launch by end of 2018 or early 2019. Was there reports of this earlier or did ISRO just pull a rabbit out of the hat?


So with that it in mind, is the SSLV also a wolf in sheep’s clothing and a template for an Indian ICBM?


Producing the article in full:

ISRO’s baby rocket to carry small satellites, likely to take off in 2019
By Tiki Rajwi | Express News Service | Published: 02nd January 2018 01:17 AM |

Last Updated: 02nd January 2018 07:06 AM | A+A A- |

THIRUVANANTHAPURAM: The first of Indian Space Research Organisation’s (ISRO) ‘baby rockets’ in the making is likely to take to the skies in the first half of 2019, top officials of ISRO’s Vikram Sarabhai Space Centre (VSSC) said.Though a formal approval for the Small Satellite Launch Vehicle (SSLV) project is still awaited, VSSC here at Thumba — ISRO’s nodal agency for launch vehicles — has already started work on it, VSSC director K Sivan said. With the global trend of satellites getting more compact, ISRO officials believe there is space for a smaller rocket that caters exclusively to small-size satellites.

On the launchpad, the SSLV will stand half as tall as a regular Polar Satellite Launch Vehicle (PSLV) and weigh in the neighbourhood of 100 tonnes, Sivan said. “A PSLV weighs over 300 tonnes. The SSLV’s weight would be around 100 tonnes and its height, 20-25 metres,” he said. The PSLV, often dubbed the reliable workhorse of the ISRO, stands 44 metres tall in comparison.

The SSLV will place small satellites in the Low Earth Orbit — orbits with altitudes up to 2,000 km.
“We hope to have the first flight of the SSLV in the first half of 2019. Across the globe, satellites are ‘shrinking’. Now, small satellites go aboard the PSLV or GSLV as ‘piggyback’ payloads alongside bigger ones,” Sivan said.

Financially, smaller can also mean smarter in the launch vehicle business. The SSLV is designed to be attractive to global customers who look to ISRO to launch their satellites.The mission cost will be roughly one-tenth that of a PSLV mission.ISRO is planning to have the SSLV flying fully on solid fuel, but the technicalities have to be worked out, Sivan said.If things go as planned, the SSLV will be ISRO’s smallest launch vehicle. At the other end of the spectrum, the space agency plans to have heavy-lift variants that will eventually replace the current generation of GSLVs.

PSLV C-40 launch postponed until January 12
ISRO has made a slight change in the flight schedule of the PSLV C-40, which will carry 31 satellites, including a Cartosat series payload. The C-40 will lift off on January 12 instead of the originally announced January 10. The reason given is that one of the smaller Indian payloads is not ready yet. According to ISRO sources, the rocket will lift off from Sriharikota at 9.28 am. The C-40 mission is a keenly awaited one as it is the first after the failed PSLV C-39 mission last August, which had sent the ISRO top brass into a tizzy.


First of all,

1. ISRO did not pull a rabbit out of its hat. This was discussed earlier.

2. The need for SSLV very emphatically underlines my take all along on this thread that increasing the payload capacity just for the sake of increasing it is useless.

3. This cannot (and must not) be used as ASAT or even ICBM and I do not think its intention is for either.

Here is what I would quote:

The SSLV will place small satellites in the Low Earth Orbit — orbits with altitudes up to 2,000 km.
“We hope to have the first flight of the SSLV in the first half of 2019. Across the globe, satellites are ‘shrinking’. Now, small satellites go aboard the PSLV or GSLV as ‘piggyback’ payloads alongside bigger ones,” Sivan said.


All the small piggyback payloads delay or complicate the main payload. PSLV is needed for the IRS/RESOURCE/CARTO class sats. India's requirements in this class is huge and basically tailoring each launch to accommodate the piggybacks to optimize the payload for financial efficiency is counter-productive.

IMHO, it is the launch window and the mission that is important. If PSLV is 80% efficient to a compared rocket but gets the job done reliably, then it is THE launch vehicle.

Again the point is that the mission is paramount and not raw efficiency. Efficiency matters, but raw efficiency without reliability is useless.

SSLV is for those "chotu" missions. Fast turn around times, low risk and a general reliable vehicle.

However I will be more impressed by ISRO if the SSLV is really turned around in a matter of days. Basically if the entire manufacture and integration chain is highly automated with significant industry participation. SSLVs should come off assembly lines, just like modern cars are manufactured. This will be the real cost savings. A cheap reliable rocket coming off the assembly line will lower the launch cost.

And that should be the focus, reliability at a lower launch cost.

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Re: Indian Space Programme Discussion - Sept 2016

Postby srin » 06 Jan 2018 08:19

I'm impressed by ISRO's agility to respond the cubesat wave and invest in cheaper and lighter solutions. If it is technologically possible, we should also go into clusters of smaller satellites (like the Planet.com's 88 satellites we launched last year) for military surveillance purposes - because they give continuous coverage and it'll be a good defence against ASATs.

BTW, what's the weight impact of the PSLV's dog leg manoeuvre around Sri Lanka ? Would it make sense to have the SSLV launched from TN where it'll be more efficient ?

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Re: Indian Space Programme Discussion - Sept 2016

Postby disha » 06 Jan 2018 09:07

srin wrote:I'm impressed by ISRO's agility to respond the cubesat wave and invest in cheaper and lighter solutions. If it is technologically possible, we should also go into clusters of smaller satellites (like the Planet.com's 88 satellites we launched last year) for military surveillance purposes - because they give continuous coverage and it'll be a good defence against ASATs.

BTW, what's the weight impact of the PSLV's dog leg manoeuvre around Sri Lanka ? Would it make sense to have the SSLV launched from TN where it'll be more efficient ?


You cannot escape the dog-leg, Sri Lanka is very much there and we cannot wish it away. And the earlier you do the dog leg maneovre the "lesser" penalty you pay.

As a rule of thumb (and a quick mental calculation and rocket purists will now scoff at this procedure), you can do a sine of the angle you have to "stray back". I would do cosine of 45 (based on this image https://commons.wikimedia.org/wiki/File:ISRO_PSLV_dogleg_maneuver.jpg) to get some 50% of the pay load. That is you could launch 1.5 tonnes instead of 1 tonne if the dog-leg maneuver were not to be done. That is a significant payload reduction.

[Edited: I should have used cosine losses instead of sine]

If S.Lanka was wiser, it can rent out a launch port from Hambantota for all space launches. It will be a win-win situation for both India and S. Lanka.
Last edited by disha on 06 Jan 2018 09:21, edited 1 time in total.

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Re: Indian Space Programme Discussion - Sept 2016

Postby disha » 06 Jan 2018 09:10

Indranil wrote:I am genuinely interested to know the payload capacity of:
1. GSLV MkIII lift with 2 S139s instead of two S200s,
2. GSLV MkIII lift with 2 S139s instead of two S60s,
3. GSLV MkII with 4 S60s instead of the LH40s. Delay the ignition of the core to T0 +50 seconds.


Some of the above design configurations should go into "design your own rocket" category.

Why would you want to skew the boosters for both GLSV MkIII and Mk II to lower S139s and S60s? What is the design goal you are trying to solve? Efficiency?

Or are you trying to arrive at a proto-ULV?

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Re: Indian Space Programme Discussion - Sept 2016

Postby Indranil » 06 Jan 2018 10:43

Configs 1. and 2. will be higher efficiency launch vehicles than PSLV/GSLV Mk2.
Config 3 will have almost same payload as GSLV Mk2, except it will cost less.

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Re: Indian Space Programme Discussion - Sept 2016

Postby Indranil » 06 Jan 2018 11:24

Indranil wrote:Configs 1. and 2. will be higher efficiency launch vehicles than PSLV/GSLV Mk2.
Config 3 will have almost same payload as GSLV Mk2, except it will cost less.

In fact, if Sc160+2S60s+C25 was supposed to be able to lift 3 tons to GTO, wouldn’t L110+2S60s+C25 be able to lift 2.25 tons to GTO?

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Re: Indian Space Programme Discussion - Sept 2016

Postby Haridas » 06 Jan 2018 13:51

Indranil wrote:Jaxa's Epsilon drove me to read a bit more about the H-IIB. Epsilon's first stage is H-IIB's booster (SRB-A3). SRB-A3 burns 66 tons of HTPB to produce a a thrust of 230 tons for 114 seconds. In our earlier discussion, you suggested that the proposed Indian equivalent would provide an equivalent thrust for 60 seconds only. I don't believe that the Indian solid rockets have half the Isp of the Japanese ones. For example, S139 uses 139 tons to provide 486 tons of thrust for 105 seconds, (i.e. off by about 8%).

So you have all info to try calculating the effective ISP of SRB-A3.
Total impulse = 230ton x114 sec = 26,680 ton sec
ISP = 26680 ton sec /66 ton = 404.2 sec ! Does is sound feasible to you for HTPB solid fuel?

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Re: Indian Space Programme Discussion - Sept 2016

Postby Haridas » 06 Jan 2018 13:56

Indranil wrote:In fact, if Sc160+2S60s+C25 was supposed to be able to lift 3 tons to GTO, wouldn’t L110+2S60s+C25 be able to lift 2.25 tons to GTO?

Saar, calculate and thou shall know.
Zameen aasman ka fark hai SC160 aur L110 kay beech.

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Re: Indian Space Programme Discussion - Sept 2016

Postby Indranil » 06 Jan 2018 20:42

I am obviously working with half knowledge here. We cannot have an average Isp of over 400 for S139 or the SRB-A3. But, those numbers are from official brochures for SL thrust. Both brochures also say that they have constant thrust!

So, I must be missing something. Let me figure out.

Haridas Sir, I am chopping payload by nearly one third in lieu of the L110. Not enough?

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Re: Indian Space Programme Discussion - Sept 2016

Postby disha » 07 Jan 2018 01:32

Indranil'ji,

I think you got the total 230 ton thrust for 116s for JAXA's SRB-A3 wrong. It should be approximate 160 ton thrust.

Here is the link to JAXA (and I used google translate) http://www.rocket.jaxa.jp/engine/srba/

The long term combustion motor (116s burn) has a 76.6 ton overall mass with propellant mass of 66 tons. Specific thrust is 283.6 seconds. That sounds right.

===

Now if you want to design a new rocket, with a goal on improving either cost or efficiency or both, you have actually very few options.

Let's agree to the following, in general:

1. SRBs are low cost and are low efficiency compared to Cryo-engines which are high cost and high efficiency. Hypergolic motors come in between.

2. Fabrication cost of a stage significantly outweigh the propellant cost. In fact the propellant cost is miniscule compared to engine and stage fabrication.

3. An all-up integrated rocket cost is not determined just by the sum total of its engine costs, but it is determined by its "integration cost". Integration cost among other things also includes the turn around time of the launch campaign. The Delta-IV Heavy has a launch history every 1.5 years which is now attempted to be shortened to every year. This enables fabrication costs to be lowered. In fact Arianne 6 is now redesigned to be same capability as Arianne 5 but with lower fabrication and integration (or launch) costs. https://spaceflightnow.com/news/n1403/27ariane6/#.U2v3InLSW-M

4. Cost of an unreliable launcher far far exceeds the the cost of a reliable launcher, even though the later might be both inefficient (say all solid) and costly.

In effect, you have different matrices for both cost and efficiency. And then you have mission goals.

Given the above, let's see where your designs fit in. Let's take:


Design I-3 -> GSLV MkII with 4 S60s instead of the LH40s. Delay the ignition of the core to T0 +50 seconds.

Reason: Config 3 will have almost same payload as GSLV Mk2, except it will cost less.



Your proposal is to replace the 4-LH40s with 4-S60s to save on the cost. However one of the GSLV-MkII stated goal is to delay the first stage ignition until the LH40s develop the required thrust on ignition. In effect you have violated the stated first goal. Further you have introduced a variable of air-igniting the S-139 . ISRO's record on air-igniting large solid core stages is patchy (see ASLV) and the only air-ignited solid stage ISRO has is HPS-3 (PSLV 3rd stage).

An alternative will be to just replace the S-139 of GSLV-MkII with S-200 of GSLV-Mk III. An interstage that goes from 3.2 mtrs to 2.8 mtrs will suffice to stack the second and third stage. This is not a major design change and a single live test will suffice to confirm the aerodynamic loadings. It can use it on SSLV itself as a test bed. The burn time of S-200 is 128 seconds compared to 100 seconds of S-139. In fact, the S-200 can have a little longer burn time, a 20% slower burn time will align the burns appropriately. Ideally if the propellant loading is increased to 240 tons, (S-240) if you may, its SI will be similar to JAXA's SRB-A3 except approximately 4 times larger and burn time aligned with the LH40s. This will take care of the stated "inefficiency" in GSLV-MkII.

Either way, the alternative suggested is to achieve a commonality on the SRB. If ISRO can standardize on S-200 (or S-2x) series, it can go for automated fabrication of S-200. The S-200 can also be the booster for the SSLV.

With a standardized solid booster for SSLV (small sat), GSLV-Mk II (medium lift Polar and GTO) and GSLV Mk-III (Heavy-lift)., ISRO can now achieve a common fabrication and reduce costs considerably. Also ISRO will require a large reliable booster for its TSTO-RLV and will require a medium lift vehicle (Mk-II) for space sciences (chandrayaans and mangalyaans).

Options to redesign GSLV-MKIIIs and skew its payloads towards medium lift category) are a no-go since that space is already occupied by GSLV-MkII. In fact GSLV-MK III should evolve into a heavy lift vehicle like Arianne V, and with commonality in reliable stages across its small, medium, heavy and reusable launch vehicle families the cost to access the space will come down drastically. At this point, raw stage efficiency does not matter.

A cheaper, faster and reliable access to space beats a "stage efficient, but costly, slower and unreliable access" to space any time.

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Re: Indian Space Programme Discussion - Sept 2016

Postby disha » 07 Jan 2018 01:39

Note that in all of the above, L110 and L40s are unchanged.

The only reason ISRO should look into semi-cryo is to get rid of the dirty & toxic UDMH/NO4 core stages. Going semi-cryo actually eases up the stage integration. Spillage of liquid oxygen is not toxic and spilled kerosene can be mopped up without leaving a highly toxic carcinogenic residue behind.

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Re: Indian Space Programme Discussion - Sept 2016

Postby Varoon Shekhar » 07 Jan 2018 01:48

A certain dubious news channel is reporting that the GSAT-11, weighing 5725 kg, is being sent off to French Guyana for launch later this month. Any truth in that? If it is accurate, why has no other news outlet or even Spaceflight Now etc, reporting it? Perhaps that is why this channel( *D*V) is dubious? :) I don't want to provide the link or fully name the entity, because a forum moderator advised me not to a while ago, when the scramjet test was conducted!

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Re: Indian Space Programme Discussion - Sept 2016

Postby Haridas » 07 Jan 2018 04:15

Disha: thank you, as always clearly explained for everyone's benefit.

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Re: Indian Space Programme Discussion - Sept 2016

Postby Indranil » 07 Jan 2018 13:36

Disha,

Thank you for the explanations.Always a pleasure when I learn something. Found a detailed write up of the SRB-A's different versions. The following chart provides a nice profile of the thrust.
Image

You have also convinced me that boosting GSLV MkII with 4 S60s instead of 4 L40s is not worth the risk (and associated costs) especially given the fact that credible launch capability in that segment exist. You and me had discussed MKII with S200 as the first stage before. You might remember that I was all for it. In fact, IIRC, I was fighting others that it is a not a very risky path. PSLV-XXL with S200 as the first stage also makes sense as a perfect stick model.

However, I am still not convinced about your arguments against the GSLV MK3 with different boosters namely S60/S-139/S-200. By the same logic of cost/risk reduction that you so aptly presented, wouldn't it sense to have 1.5 ton to 4.5 ton capacity by using the same core, but different boosters. This is the global norm and ISRO's chosen path for the future: aka ULV. Why not start with GSLV MK3?

As soon as the confidence in GSLV Mk3 is achieved, retire GSLV Mk2. Retain PSLV for sub 1.5 ton to GTO and unified GSL for 1.5-4.5 ton to GTO. When SC160 arrives, switch out the L110 and you have ULV ready.

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Re: Indian Space Programme Discussion - Sept 2016

Postby Haridas » 07 Jan 2018 22:55

disha wrote:ISRO's record on air-igniting large solid core stages is patchy (see ASLV) and the only air-ignited solid stage ISRO has is HPS-3 (PSLV 3rd stage).

Disha ji,
1. Could you please elaborate?
2. Since ASLV days (those were the days) ISRO has moved on to master more complex solid stages, so I would like to know more to understand your assertion.
3. The solid fuelled igniter subsystem has further made solid stage ignition extreamly robust. (See drdo solid stages and their igniters). So unable to digest supposed risk aversness to air-lit solid stage.

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Re: Indian Space Programme Discussion - Sept 2016

Postby prasannasimha » 08 Jan 2018 09:26

2 SRB's of PSLV are airlift.
The reason for liquid strap one on GSLVMk2 was they wanted the liquid motors to develop full thrust prior to solid rocket firing as the latter cannot be stopped once fired on the pad.

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Re: Indian Space Programme Discussion - Sept 2016

Postby Indranil » 08 Jan 2018 09:44

I have heard this logic a few times, but don't understand it.The L40s are started 4.5 seconds to check their health and build up max thrust. If even one of them don't work, the S139 is not ignited. But that cannot be the reason to go for the L40s in first place.

The reason to go for L40s seem very obvious to me. That was the only "large" liquid engine available to ISRO then. But more than one of them had to be used, if they were to be part of the first stage. ISRO did not have the tech to cluster them. So, the only option was to go for boosters.

The delta V required from the first stage could not be achieved with the L40s burning for 110 seconds. So they had to go with the compromise of lugging the inert mass of the spent S139 stage. This was the simplest and safest way in front of them then. But, is it the only way now?

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Re: Indian Space Programme Discussion - Sept 2016

Postby prasannasimha » 08 Jan 2018 14:54

It is not with the GSLVMk3 but GSLV Mk3 itself is still not fully qualified and with a working model they will be loath to change till the other stabilizes

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Re: Indian Space Programme Discussion - Sept 2016

Postby Zynda » 09 Jan 2018 20:09

Team Indus has dropped out of Space Race to place a lander on Moon. Mentioned on NDTV...sad to see another niche private venture bite the dust. Was a long shot for them anyways but somehow up until recently, they managed to stay afloat. Ideally this project could have been sponsored by a few (or one) giant Indian Engineering firm with suitable agreements to share IP, know how, methodologies employed which could be transferred to other programs etc. Or even from academic institutions...ask them engineers to share their learnings via courses or whatever (still can happen if the institutes are enterprising enough...)


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