Indian Space Programme Discussion - Sept 2016

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adityadange
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Re: Indian Space Programme Discussion - Sept 2016

Postby adityadange » 23 Sep 2016 16:05

@vina, just a question.
does gravity drag remains constant for all size/shape/weight objects? reason i ask this question is, the four configs you have mentioned above will have different weight (and probably size/shape if we differentiate them as clustered and non clustered configs). If gravity drag varies based on dimensions then calculations may show wrong output. or this aspect is already taken care in your spreadsheet?

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Re: Indian Space Programme Discussion - Sept 2016

Postby nirav » 23 Sep 2016 19:07

indranilroy wrote:
Snip.



Dear Indranilroy,

I re read your post and the first impression one gets from it is that you actually called the guys at ISRO dorks.
But since you have clarified that it was not the case, Id like to apologise to you.

Having said that, i stand by my comment and observation on an equation and spreadsheet based rocketry.Since I used hindi it appears crass and crude, maybe in english it would have been less offensive.

Ive been following ISRO thread for the longest of times. And I recall repeated insults hurled at isro via the childish moniker for Vikas engines, the criticism for going semi cryo at such a later stage, the infamous "lugging" of the S139, the "inefficiency" ..

With every launch of the GSLV, this terrible cycle repeats all thanks to one poster and i kind of reached breaking point leading to an outburst. Its only now that hnair banned the usage of the ridiculous moniker for the Vikas engines, it went on for far too long.I had objected in the past too, but the gent was too arrogant back then to pay heed to a request to not use it.

Im not an ultra cyber patriot who will take umbrage at the slightest of criticism. I welcome criticism and the ensuing debate.

In this case however, theres been a 'pull numbers out of your assathon' to support ones ridiculous theories for "fixing" GSLV. The poster has himself posted varying numbers ranging from the lugging causing a few tons penalty on payload to a few hundred.
He himself isnt sure of whats the exact penalty on the payload capacity but still confidently offers his "fixes" as a quick fire way to achieve 4-6 tons to GTO by GSLV mk2.

If you see his previous posts after the launch, one can make out that he almost has an axe to grind wit the ISRO> 5 seconds between stage separation and ignition -Inefficient. Non clustered engines - inefficient. Vikas engine - banned word. Mass fraction - inefficient. ISRO - inefficient.

When theres such intense talk coming from a person about ISROs inefficiency, its only fair to question his real world experience with modern rocketry. Sivakasi rockets fired during diwali dont count as experience.

When it comes to the question of "lugging" of the S139 tank for 40 odd seconds, im with you when youd said that we need to find out why ISRO chose to go ahead with the configuration.

We could focus on why they choose to stick with the same configuration even now and for future launches. That way one could actually learn a thing or two about what goes on in the decision making in ISRO wrt selecting configurations.

Informed debate is always welcome and should be encouraged. Name calling and hurling insults on ISRO based on spreadsheet rocketry is not criticism nor debate. It is laughable and i called it out for what it actually is..

I would really appreciate a design you rocket thread so as to take all the negativity from ISRO thread.
Ive had it with the non sense post every launch.

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Re: Indian Space Programme Discussion - Sept 2016

Postby SSSalvi » 23 Sep 2016 19:45

A simulated launch sequence for next PSLV :

Image

In all viewes the s/c is moving from North to South in front of viewer.

After SCARSAT releaseat 730 kms altitude the Launcher moves towards South pole and traversing half orbit from backside of Globe appears over North Pole when the second ignition takes pl;ace ( using Svalbard station ranging and command ?? ) to reduce the altitude. .
Then after about half orbit when the launcher is over South pole at 689 kms altitude one more ignition is used ( to fine tune launch conditions ?? ) and after shutdown Dual Launch adapter is released and after half a minute remaining satellites are released ( Alsat-1N, NLS 19, Pratham, PiSAT, Alsat-1B, Alsat-2B and Pathfinder-1 .. in that order ) in about 2.3 minutes while the launcher is moving South to North behind the globe in graphic.

Notice that the Earth is moving continuously left to right.
Last edited by SSSalvi on 23 Sep 2016 21:49, edited 3 times in total.

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Re: Indian Space Programme Discussion - Sept 2016

Postby nirav » 23 Sep 2016 20:03

Think this thread could use a sonic boom.
Rumbling and grumbling of ISROs biggest bad boy.

GSLV MK3 launch of last year.


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Re: Indian Space Programme Discussion - Sept 2016

Postby Indranil » 23 Sep 2016 20:07

Nirav,

No problem. All is well.

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Re: Indian Space Programme Discussion - Sept 2016

Postby Indranil » 24 Sep 2016 05:24

Continuing with the back of the envelop calculations. Vina could you help me calculate the values of payloads x, y and z using your spreadsheets. I am trying to find the performance of a 3.2 m dia GSLV-H using S200 and CE-20. I have tried to keep the weight of stage 2 + stage 3 the same as the current GSLV MK2. Stage 1 is obviously heavier by virtue of the S200.

GSLV-H1 (H is for hypothetical, not heavy)
Synopsis:
1. S-200 as Stage 1
2. Stage 2 dia changed to 3.2 mtrs, propellant mass left unchanged
==========================================================
Height: ~48 mtrs
Diameter: 3.2 mtrs
Launch mass: 490 + x T
payload: x T

1st stage (S200)
=============
Length : 22 m
Diameter : 3.2 m
Inert Mass 31.3 T
Launch Mass : 238 T
Thrust (SL): 5,151 kN
Specific Impulse (SL): 227s
Specific Impulse (Vac): 274.5s
Stage ignition: T0 + 0 secs
Burn Time: 130s
Separation: 149.5s

Boosters 4 (current config as GSLV)
===========
Length: 19.7m
Diameter: 2.1m
Inert Mass: 5.6 k T
Launch Mass: 47.6 T
Thrust (SL): 763kN
Impulse: 293 sec
Stage ignition: T0 - 4.8 secs
Burn Time: 153.8 sec v(flight time of 149 secs)
Stage Separation: With Core Stage

2nd stage (same fuel-mass/engine as GSLV)
========================================================
Inert Mass: ~5.5 T (near identical to GSLV)
Launch Mass: 45 T (near identical to GSLV)
Length: ~ 9.64m (tank with 3.2 mtr diameter with same volume as GSLV stage 2 tank, engine length is 3.51 mtr)
Diameter: 3.2m
Propellant Mass: 39,400kg
Propulsion: 1 Vikas 4
Thrust (Vac): 799kN
Impulse: 293s
Engine Dry Weight: 900kg
Stage ignition: T0 + 149.5 secs
Burn Time: 141 sec
Stage seperation: T0 + 293 secs

3rd stage (same fuel-mass/engine as GSLV)
==============================
Inert Mass: ~2.5 T (near identical to GSLV)
Launch Mass: ~15.3 T (near identical to GSLV)
Length: ~ 7.2m (tank with 3.2 mtr diameter with same volume as GSLV stage 3 tank, engine length is 2.15 mtr)
Diameter: 3.2 m
Propellant Mass: 12.8 T
Propulsion: 1 ICE (CE-7.5)
Thrust (Vac): 73.5 to 93.1kN
Specific Impulse: (Vac): 454s
Burn Time Up to: 1,000sec

Payload fairing
=============
Length 7.8 m
Mass ~ 0.5 T (including adapters etc.)


+++++++++++++++++++++++++++++++++++++++++++++++++++++++

GSLV-H2 (H is for hypothetical, not heavy)
Synopsis: S-200 + stage 2 and stage 3 dia changed to 3.2 mtrs, propellant mass of stage 2 and stage 3 left unchanged, stage 3 is now powered by CE-20
===================================
height: ~49 mtrs
Diameter: 3.2 mtrs
launch mass: 490 + y T
payload: y T

1st stage (S200)
=============
Length : 22 m
Diameter : 3.2 m
Inert Mass 31.3 T
Launch Mass : 238 T
Thrust (SL): 5,151 kN
Specific Impulse (SL): 227s
Specific Impulse (Vac): 274.5s
Stage ignition: T0 + 0 secs
Burn Time: 130s
Separation: 149.5s

Boosters 4 (current config as GSLV)
===========
Length: 19.7m
Diameter: 2.1m
Inert Mass: 5.6 k T
Launch Mass: 47.6 T
Thrust (SL): 763kN
Impulse: 293 sec
Stage ignition: T0 - 4.8 secs
Burn Time: 153.8 sec v(flight time of 149 secs)
Stage Separation: With Core Stage

2nd stage (same fuel-mass/engine as GSLV)
============================================
Inert Mass: ~5.5 T (near identical to GSLV)
Launch Mass: 45 T (near identical to GSLV)
Length: ~ 9.64m (tank with 3.2 mtr diameter with same volume as GSLV stage 2 tank, engine length is 3.51 mtr)
Diameter: 3.2m
Propellant Mass: 39,400kg
Propulsion: 1 Vikas 4
Thrust (Vac): 799kN
Impulse: 293s
Engine Dry Weight: 900kg
Stage ignition: T0 + 149.5 secs
Burn Time: 141 sec
Stage seperation: T0 + 293 secs

3rd stage (same fuel-mass/engine as GSLV)
==============================
Inert Mass: ~2.5 T (near identical to GSLV)
Launch Mass: ~15.3 T (near identical to GSLV)
Length: ~ 8.2m (added 1 mtr extra for the CE-20 engine)
Diameter: 3.2 m
Propellant Mass: 12.8 T
Propulsion: 1 CE-20
Thrust – Vacuum: 200kN
Operational Range: 180-220kN
Specific Impulse (Vac): 443s
Burn Time: 297 secs

Payload fairing
=============
Length 7.8 m
Mass ~ 0.5 T (including adapters etc.)

++++++++++++++++++++++++++++++++++++++++++++++++++++

GSLV-H3 (H is for hypothetical, not heavy)
Synopsis: S-200 + stage 2 and stage 3 dia changed to 3.2 mtrs, propellant mass of stage 3 increased to propellant mass of LVM3, propellant mass of stage 2 decreased accordingly, total mass of propellant in Stage 2 + stage 3 is still identical GSLV -Mk2, stage 3 is powered by CE-20
===================================
height: ~52 mtrs
Diameter: 3.2 mtrs
launch mass: 490 + z T
payload: z T

1st stage (S200)
=============
Length : 22 m
Diameter : 3.2 m
Inert Mass 31.3 T
Launch Mass : 238 T
Thrust (SL): 5,151 kN
Specific Impulse (SL): 227s
Specific Impulse (Vac): 274.5s
Stage ignition: T0 + 0 secs
Burn Time: 130s
Separation: 149.5s

Boosters 4 (current config as GSLV)
===========
Length: 19.7m
Diameter: 2.1m
Inert Mass: 5.6 k T
Launch Mass: 47.6 T
Thrust (SL): 763kN
Impulse: 293 sec
Stage ignition: T0 - 4.8 secs
Burn Time: 153.8 sec v(flight time of 149 secs)
Stage Separation: With Core Stage

2nd stage (shortened to allow a longer Stage 3)
=====================================================
Inert Mass: ~5 T
Launch Mass: 31 T
Length: ~ 7.5 m
Diameter: 3.2m
Propellant Mass: 26 T
Propulsion: 1 Vikas 4
Thrust (Vac): 799kN
Impulse: 293s
Stage ignition: T0 + 149.5 secs
Burn Time: 91.5 sec
Stage seperation: T0 + 243 secs

3rd stage
==============================
Inert Mass: ~4.0 T (same mass as C25 on LVM3)
Launch Mass: ~29.0 T (same mass as C25 on LVM3)
Length: ~ 13.0m (same volume as LVM3 tank, engine length is 3.15 mtr)
Diameter: 3.2 m
Propellant Mass: 25.0 T
Propulsion: 1 CE-20
Thrust – Vacuum: 200kN
Operational Range: 180-220kN
Specific Impulse (Vac): 443s
Burn Time: 590 secs

Payload fairing
=============
Length 7.8 m
Mass ~ 0.5 T (including adapters etc.)

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Re: Indian Space Programme Discussion - Sept 2016

Postby sivab » 24 Sep 2016 07:14

^^^This thread is going down the toilet with active encouragement of moderator. What has above post got to do with Indian Space program as stated in title? If you want to indulge in this fantasy why not start a design your own rocket thread?

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Re: Indian Space Programme Discussion - Sept 2016

Postby prasannasimha » 24 Sep 2016 07:34

Also discussions are going on without considering aerodynamic and design issues which all add up to strikingly different outcomes. It is better this is taken to a different thread.
More importantly it has been 2 years now since MOI of Mars orbiter mission. Not a peep about that though here.

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Re: Indian Space Programme Discussion - Sept 2016

Postby prasannasimha » 24 Sep 2016 07:37

Mission Readiness Review (MRR) committee and Launch Authorisation Board (LAB) have cleared the 48 and half hr countdown of PSLV-35/SCATSAT-1 Mission
Mission Readiness Review (MRR) committee and Launch Authorisation Board (LAB) have cleared the 48 and half hr countdown of PSLV-35/SCATSAT-1 Mission for Saturday, September 24, 2016 starting at 08:42hr IST and the launch of PSLV-C35 / SCATSAT-1 mission for Monday, September 26, 2016 at 09:12 hr IST

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Re: Indian Space Programme Discussion - Sept 2016

Postby vina » 24 Sep 2016 08:06

sivab wrote:^^^This thread is going down the toilet with active encouragement of moderator. What has above post got to do with Indian Space program as stated in title? If you want to indulge in this fantasy why not start a design your own rocket thread?

:rotfl:
Yeah,right.. Actually doing science, building a pretty high fidelity model of the vehicle and examining the Indian Launch Vehicles and possible configurations, trying to find why possible rationale for the designs as they exist, are the future ones going to be competitive with global future launch vehicle, all with science and actual launch data , examining what can be done in terms of future designs and configs, based on what is available now and what is coming soon is "going doing the toilet", while posting some random YouTube videos of a long range range amateur video of a launch with expletives "C***u","B**", and some hare brained sophomoric talk is "uplifting" and is indeed what this thread is meant for.

Consider pearls of "wisdom", thrown by a few folks thrown here. "You cannot estimate the weight of the casing of the S139 engine from the GSLV 1 and use it in GSLV 2, though it is the same engine , why? because they filled less fuel in GSLV1"..

I have seen people saying they are glad that the talks is about numbers, but I am the ONLY one putting up numbers to back up what I say. Others said the possible payload loss is "negligible" (150 to 200 kgs), all backed by Science of course. I am all ears. Let us see numbers and math! I have seen NONE until now, except, "I think" and "I feel".

As for doing it on a spreadsheet and is somehow infradig, that is surely the absolutely DUMBEST argument I have heard. These same calculations done on a SLIDE RULE and at best a large sized rudimentary calculator that sat on a desk is what sent man to the moon and brought him back. A modern spreadsheet has absolutely everything in terms of math and scientific functions , including simulation and problem solving capabilities. Whether is done in a spreadsheet, or a package like MatLab or R or Octave or whatever is immaterial. You can give a medieval chisel and a mallet to a Michelangelo and you can get a David, you can give a precision laser carver to a ignoramus and you will get a misshapen blob!
Last edited by vina on 24 Sep 2016 08:08, edited 1 time in total.

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Re: Indian Space Programme Discussion - Sept 2016

Postby vina » 24 Sep 2016 08:07

prasannasimha wrote:Also discussions are going on without considering aerodynamic and design issues which all add up to strikingly different outcomes. It is better this is taken to a different thread.
More importantly it has been 2 years now since MOI of Mars orbiter mission. Not a peep about that though here.


That is not true! The numbers are taken from launch data and reflect all the issues in real world as they exist!

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Re: Indian Space Programme Discussion - Sept 2016

Postby srin » 24 Sep 2016 09:03

Speaking for myself, I've quite enjoyed the discussion of the past couple of days. I'd always wondered about the unnecessary lugging of the first stage, but it is refreshing to see a quantitative treatment of the subject. Though I'm unable to contribute much, I'd like to see more of this than purely subjective opinions.

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Re: Indian Space Programme Discussion - Sept 2016

Postby SSSalvi » 24 Sep 2016 10:04

Mods .. It is really a good idea to start a design thread and compile these related posts there and continue discussions.

There are some harsh posts but that happens in any meetings/discussions and a reality emerges ,, e.g Atmospheric drag which was earlier ignored has been incorporated and there is a good rapport now among the warriors.

There is a whole wealth of information here which will just go down the regular Indian Space related posts. ( On Monday this discussion will hide below 3 or 4 pages pertaining to a launch !!)

Hence seriously please see if a design thread is started.

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Re: Indian Space Programme Discussion - Sept 2016

Postby shiv » 24 Sep 2016 10:17

Design your own space launch vehicle thread started
viewtopic.php?f=3&t=7254

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Re: Indian Space Programme Discussion - Sept 2016

Postby Indranil » 24 Sep 2016 12:12

All that is needed to go down the drain is discuss some rocket science 101.

All that is needed to go off topic on an Indian space rockets threads is a discussion of different stages of Indian rockets, existing and optional configs!

Moving the discussion to another thread. But as somebody who has lurked around BR for ten years, it's a sad day for me.

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Re: Indian Space Programme Discussion - Sept 2016

Postby Neela » 24 Sep 2016 13:00

srin wrote:Speaking for myself, I've quite enjoyed the discussion of the past couple of days. I'd always wondered about the unnecessary lugging of the first stage, but it is refreshing to see a quantitative treatment of the subject. Though I'm unable to contribute much, I'd like to see more of this than purely subjective opinions.


+1
IndranilRoy & Vina , please continue.
For me the difficult bridge to cross is how the lugging of ~12T for 40 odd seconds translates to extra payload.
Really would appreciate if this can be explained differntly. (or dumbed down)

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Re: Indian Space Programme Discussion - Sept 2016

Postby prasannasimha » 24 Sep 2016 17:35

During the lugging of 40 tons it is supposed to be coasting not accelerating. If anyone has a record of the flight profile it may be clearer.

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Re: Indian Space Programme Discussion - Sept 2016

Postby nirav » 24 Sep 2016 18:38

The response to the youtube video gives a peek into the negative mindset of Scientist S. (where S stands for Spreadsheet)

As per my knowledge, its the only video of GSLV Mk3 or for that matter any other ISRO rocket whenein the sonic boom is captured very clearly.That post was made in jest and for that specific purpose of the sonic boom.

Yet Scientist S chose to focus on the video shooters language instead and rant about it.

It has been observed that this thread has turned into space nukkad. I agree with it.

with such brilliance on display, what can one say ? :rotfl:
vina wrote:I will put up the spread sheet for everyone to play with in due course, I first need to reformat it,put in a lot of comments and explanatory notes and generally tidy it up before anyone else can sense of it and use it. I put that together in my spare time in less than 30 minutes. However don't hold my feet to the fire for a timeline, I will try to put it up as soon as I can, time permitting.


Credentials/experience of Scientist S are still unknown btw.

ISRO has taken a couple decades to get the GSLV working reliably in its current config.
But Sh. Scientist S has solved for 4-6 tons of GTO in his 'spare time in less than 30 minutes'. :roll:

I hope SUPARCO is reading this thread with huge interest.

Edit : I request the mods to move out all spreadsheet based flights of fancy posts to that specific thread and also clean up this thread of OT stuff. Its got no bearing on ISRO and is massively OT.
Apologies to the mods for increasing their workload.

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Re: Indian Space Programme Discussion - Sept 2016

Postby sooraj » 24 Sep 2016 18:45

Image

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Re: Indian Space Programme Discussion - Sept 2016

Postby Shankas » 24 Sep 2016 19:22

Why is there no lightning towers surrounding this launch tower?
I can see them around the other launch tower in the background.

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Re: Indian Space Programme Discussion - Sept 2016

Postby Lilo » 24 Sep 2016 19:54

This spaceflight101 profile on GSLV Mk 1/2 says the same thing about the inefficiency of lugging the 30 tonne dead weight - to avoid the risk involved in a booster separation event.

...The four boosters ignite 4.6 seconds prior to the first stage to allow the Vikas engines to reach operational conditions before the Core Stage is ignited and the rocket blasts off. In flight, the four boosters continue to burn after first stage shutdown and are separated from the vehicle with the first stage. The advantage of this simpler design is that a Booster Separation event is avoided, but it comes at the cost of performance because the four boosters have to propel the first stage once it has burned out which represents nearly 30 tonnes of dead weight.
...
http://spaceflight101.com/spacerockets/gslv-mk-ii/


GSLV MK1/2 would have been designed in the mid 90s so the risk appetite would have been quite low for a cashstrapped organisation - here one can understand the avoidance of a "booster separation event".
But no point in continuing that design into GSLVMk3 - unless its some sort of continuing CBM to the western space agencies who dominate the space launch business , and whose market share can be reduced if ISRO puts into play efficient rockets(the semicryo scandal is also linked to this issue).
Maybe there is an understanding that Indian space program will confine itself to launching Indian sats - and wont "intrude" into global launch business seriously ,so that the access tap to the off the shelf dualuse tech which ISRO necessarily needs in many of its newer missions - is kept open by the west.

I agree that calculating the payload capacity lost to GTO by this inefficiency is a worthy endeavor and unless ISRO responds to RTI , only brochures are left to do that outside ISRO.
It would also be best if some one asks a bigwig in ISRO directly to get a corroborating figure.

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Re: Indian Space Programme Discussion - Sept 2016

Postby Indranil » 24 Sep 2016 22:23

ISRO had no other option at the time. With whatever they had, this is the best they could have done. Nobody is contending that. People are trying to understand what could have been the full potential of this launch vehicle today if we retrofit parts that are present within ISRO today.

Prasanna sir, the craft is not coasting then, it is powered by the four strapons till first stage separation.

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Re: Indian Space Programme Discussion - Sept 2016

Postby vina » 24 Sep 2016 23:08

nirav wrote:As per my knowledge, its the only video of GSLV Mk3 or for that matter any other ISRO rocket whenein the sonic boom is captured very clearly.That post was made in jest and for that specific purpose of the sonic boom.

Yet Scientist S chose to focus on the video shooters language instead and rant about it.


:rotfl: . What you are hearing is the booming sound of your farting. Sonic boom indeed! As an ignoramus who has has idea of what it is ,how it is formed, or even if someone so clearly distant from the flight path and that too of a vehicle flying away from the observer can even hear it and feel it , even in theory , you clearly missed a great opportunity to keep your mouth firmly shut.

When I saw the title of the video of sonic boom, my first thought was, OMG, did they shoot the video out at sea from close to the flight path ! Then within a few seconds I recognized it for what it was and spared myself the rest of that nonsense.

It has been observed that this thread has turned into space nukkad. I agree with it.

With garbage like this posted around and held up as an example of "sonic boom", if this thread hasn't degenerated into a Nukkad, what is it?

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Re: Indian Space Programme Discussion - Sept 2016

Postby prasannasimha » 24 Sep 2016 23:16

^ can all of you take your discussion elsewhere instead of trying to score brownie points here. Mods can we put an end to this oneupmanship.
Can the mods put a stop to this.

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Re: Indian Space Programme Discussion - Sept 2016

Postby Indranil » 24 Sep 2016 23:27

prasannasimha wrote:^ can all of you take your discussion elsewhere instead of trying to score brownie points here. Mods can we put an end to this oneupmanship.
Can the mods put a stop to this.

Agreed.

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Re: Indian Space Programme Discussion - Sept 2016

Postby nirav » 24 Sep 2016 23:29

vina wrote:
nirav wrote:As per my knowledge, its the only video of GSLV Mk3 or for that matter any other ISRO rocket whenein the sonic boom is captured very clearly.That post was made in jest and for that specific purpose of the sonic boom.

Yet Scientist S chose to focus on the video shooters language instead and rant about it.


:rotfl: . What you are hearing is the booming sound of your farting. Sonic boom indeed! As an ignoramus who has has idea of what it is ,how it is formed, or even if someone so clearly distant from the flight path and that too of a vehicle flying away from the observer can even hear it and feel it , even in theory , you clearly missed a great opportunity to keep your mouth firmly shut.

When I saw the title of the video of sonic boom, my first thought was, OMG, did they shoot the video out at sea from close to the flight path ! Then within a few seconds I recognized it for what it was and spared myself the rest of that nonsense.

It has been observed that this thread has turned into space nukkad. I agree with it.

With garbage like this posted around and held up as an example of "sonic boom", if this thread hasn't degenerated into a Nukkad, what is it?


That you cant figure out when the sonic boom happens in the vid i posted shows how utterly clueless you are about your "science".

name calling is your forte, i concede defeat.
Please continue your flights of fancy in design your rocket thread.

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Re: Indian Space Programme Discussion - Sept 2016

Postby prasannasimha » 25 Sep 2016 00:20

^ Just for clarification a vertically launched rocket will not allow a sonic boom to pass over a ground based observer as the shock wave cone will not be in that direction but the boom will be heard if it is appropriately inclined but if the rocket yaws or pitches setting up some oblique shock waves but by that time the cone would not be over the area of interest or reach you in a rocket like the GSLV. What you would be hearing is the rumble due to vibrations which are muted by the acoustic suppression system (the giant tower that discharges water to suppress acoustic vibration)
During the transonic regime what you can see - is the condensation cloud that forms when the shock wave occurs with optical tracking but not the sound. If you see any rocket launch and concentrate near the nose cone you can see the condensation cloud during tracking.
Image

Is an example of a shock collar or vapor cone

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Re: Indian Space Programme Discussion - Sept 2016

Postby nirav » 25 Sep 2016 01:55

Prasannasimha ji,

Its being said that we cant hear sonic booms on ground, by you gracefully and by Scientist S rather pompously.


I had btw posted the video to get a break from the vicious cycle.The bangs heard in the said video are what i think are sonic booms.They could be because of transonic shock waves, i wondered .. Until i found the link after a little digging.

Id like you to take a look at this.(The website is gold for those interested in research articles)

http://www.currentscience.ac.in/Volumes/102/01/0105.pdf

And i quote from the article titled - Seismic signatures of the sonic boom during the launch of Chandrayaan-1

We present the seismic signatures generated by the sonic boom during the launch of Chandrayaan-1 from the Satish Dhawan Space Centre, Sriharikota on 22 October 2008. A network of six digital broadband seismographs spread over a distance of 35 km recor-ded the air coupled seismic waves due to the sonic boom. These are recorded as first arriving waves on the seismogram with a velocity of about 338 m/s and frequency of ~ 5 Hz. Also, the amplitudes of the wave-forms indicate a high attenuation of the order of 10 in the marshy Pulicat Lake area. The lake area experienced a significant pressure of about 55 microbar due to the impact of the sonic boom.

and further
The PSLV lifted-off from SHAR with the trajectory away from the line of the seismograph network. Hence
we could record the boom carpet that hit the Pulicat Lake and produced the air-coupled seismic waves. The sonic
boom at the Pulicat Lake was experienced about 15–20 s after the zero time and continued till about 35–40 s (pers.
obs. by the authors).


In that research paper they are talking about the 'seismic impact' of sonic booms caused by the PSLV Chandrayaan on Pulicat lake and other locations.Please check the report for exact details.

Scientist S's theory goes for a toss as the stations which recorded the seismic readings due to the sonic booms are further inland than the boys probably were and not in the bay of bengal. Article has a map of the stations and the lake and launch site.

I could choose to really rub it in for Scientist S, but id rather not derail the thread.

Punching out numbers on a spreadsheet is not research work.Its just a tabulated form of "I think, I feel" blah blah,4-6 tons to GTO ..

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Re: Indian Space Programme Discussion - Sept 2016

Postby GShankar » 25 Sep 2016 05:25

Neela wrote:
srin wrote:Speaking for myself, I've quite enjoyed the discussion of the past couple of days. I'd always wondered about the unnecessary lugging of the first stage, but it is refreshing to see a quantitative treatment of the subject. Though I'm unable to contribute much, I'd like to see more of this than purely subjective opinions.


+1
IndranilRoy & Vina , please continue.
For me the difficult bridge to cross is how the lugging of ~12T for 40 odd seconds translates to extra payload.
Really would appreciate if this can be explained differntly. (or dumbed down)


Yes, please continue. This is the closest I could ever get to understand "Rocket Science" :)

On the contrary, one can also create a thread like the "ISRO achievement" thread where there are no discussions. However, I like that some of the discussions have the depth along with context. My request is to not break it up.

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Re: Indian Space Programme Discussion - Sept 2016

Postby Indranil » 25 Sep 2016 07:16

nirav wrote:Punching out numbers on a spreadsheet is not research work.Its just a tabulated form of "I think, I feel" blah blah,4-6 tons to GTO ..

The making of rocket parts requires intense research. It's multi-disciplinary and lies at the boundary of current human knowledge. However, once the parts have been manufactured and their attributes accurately known, predicting the flight path is actually simple math which can be done using log tables and an envelop, forget a modern spreadsheet.

If one goes through our discussion, one would realize that Vina and I are actually opposed to each other. He was quite convinced that ISRO could have done better and I was sure the ISRO did the very best with what they had. Unfortunately, I don't know enough physics or math to say why. In the process of trying to prove what he contends Vina mathematically came up with a rudimentary model. According to his model, it was easier to understand quantitatively, why ISRO was doing what. But, the model is still not accurate. The model considers the thrust each stage as constant, This is true only for the second stage. The thrust of the first stage increases as the rocket travels from sea level to outside the atmosphere. The third stages thrust is regulated by ISRO for best results.

The depth of enthusiasm for different people is different. Some limit it to just congratulating ISRO's on successes. Others want to go deeper, and that does not constitute questioning ISRO's wisdom. I ask anybody on this forum to answer the following question, why is the 440,000 kg GSLV only able to launch 2.5 Tons to GTO, where others do much better? Can anybody reply? Some of us are trying to understand why. And those who can't answer are asking why are you investigating? I ask these so-called fans of Indian space missions: If I went up to Dr. Kalam (or any senior scientist at ISRO) and asked the same question, what would be their reaction. Would they encourage this discussion or berate this effort to understand?

BR used to be full of Arun_Ss, n^3s , Harrys etc. who used to only discuss technical points. Today's posters have thousands of posts to their credit, and can't answer simple questions. Yet they pontificate on what others should discuss, and even how this forum should be moderated. It is a real pity.

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Re: Indian Space Programme Discussion - Sept 2016

Postby Vivek K » 25 Sep 2016 07:27

I appreciate vina's efforts in making the case from his perspective. Discussions should be welcomed. ISRO is India's most successful and admired organization and has given Indians hope and pride. However, there is still scope for improvements and we shouldn't be scared of asking them. Its all good!

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prasannasimha

Postby prasannasimha » 25 Sep 2016 08:16

IndraniI I think no one would say no to those discussions when attempting to be rigorous bur when it is interspersed with expletives and name calling or whatevery it just detracts. Being civil and not mocking is all that one needs to do and the same can be jolly well done and will not detract from the discussion. Incidentally even isro scientists recognize and accepted that GSLV was suboptimal but they did the design with what technology and technical knowledge they had at hand at that time. Even Mk3 was designed way back with no credible cryogenic engine. Let us not forget that the unique stacking of PSLV was what allowed MOM to be injected into Mars trajectory and with 'conventional' stacking we would not have been able to do it. As and when semicryo is achieved the lvm3 will be changed. Also you cannot just mix and match so easily at whims and fancy when you essentially have to do major design changes and validation. Understanding the limitations is one thing.Mentioning it is also OK But continuous expletives makes the whole post loose its sheen. Let that be stopped. Also when we say weshould do this or that a cogent discussion should also make a statement on why they could not do it to also keep things in perspective.. understanding the challenges is also equalling important. Simply thing like the open truss of LVM3 can cause issues on booster separation dynamics so booster separation is not as simple as one thinks (ir just doesn't drop of) but should not collide with the main stack. If you go to the LVM3 flight path did you see the deviation albeit minor from flight path around the time of separation which was corrected later. I don't lknow how many saw that but was obvious in the video. That is why we have these flights and experiments. Easy to say since components are there rocketry is plain physics but unfortunately the best CFD models in rocketry cannot still totally validate the model with the certainty that is expected in other manufacturing. That is why isro has to struggle. If all was so hunky dory wjhy haven't all other countries done it?
Just a simple thing like the lugging of extra weight. Any thought on how would booster separation with stack mismatch of the central core be easy? That is not as simple as we just did not have the data for this during design and in fact we got large booster separation data only with lvm3

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prasannasimha

Postby prasannasimha » 25 Sep 2016 08:19

Let us not forget one thing about large SRB's. Earth storing and handling is very much easier allowing preproducton that can significantly ease the launch campaign. This by itself reduces costs significantly. Also in the densw atmospheric phase the high energy density provides an advantage, simplicity and lower costs.

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Re: Indian Space Programme Discussion - Sept 2016

Postby prasannasimha » 25 Sep 2016 09:30

So the sonic boom signature indeed has been recorded out to a distance of 35 Kms around Pulicat lake from the launch sit as per the article posted.

To quote the article

The PSLV lifted-off from SHAR with the trajectory
away from the line of the seismograph network. Hence
we could record the boom carpet that hit the Pulicat Lake
and produced the air-coupled seismic waves. The sonic
boom at the Pulicat Lake was experienced about 15–20 s
after the zero time and continued till about 35–40 s (pers.
obs. by the authors).

The seismic waves produced due to the sonic boom of
Chandrayaan-1 were recorded till a distance of 35 km

So since we have the direct recordings of the boom carpet in the article in essence the sonic boom would be recorded. Also the very need for an acoustic suppression system probably indicates that the rocket plume hitting the stand during take off would probably set up significant shock waves too that need damping.

I stand corrected.
Now what do the other honorable members have to say when presented direct scientific peer reviewed data ?
Isn't this type of discussion more cogent ?

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Re: Indian Space Programme Discussion - Sept 2016

Postby prasannasimha » 25 Sep 2016 09:43

Again for SRB's while they do not provide a higher specific impulse they have one great advantage and that is they ahve a high energy density so a hugher thrust and this helpsactually to keep the net size/weight/complexity paradoxically down in the dense atmospheric phase as the large fuel tanks etc put an atmospheric drag penalty. So it is a complex combo of choices that are being made.


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Re: Indian Space Programme Discussion - Sept 2016

Postby prasannasimha » 25 Sep 2016 09:54

Also another thing regarding costing when we say we can launch this or that with a more efficent rocket can you work out the cost per Kg payload for GSLV Mk3 to say an Ariane launcher delivering 4 Tons to GTO. The cost with this so called inefficent design is however 2/3 rd less than that of Ariane.(ISRO director is on record regarding this costing). Rocket efficiency versus cost effectiveness are not one is to one. Also we just do not have a tested semicryo engine at present though the L110 will be replaced by a semicryo engine. I do not think the SRB's will be discarded because even with a weight penalty they still are cost effective.

Let us not forget that things are not so simple Space X is having things blowing up and that is with full support and significant technology transfer from NASA. It is only after things are ironed out that NASA is able to use semicryo and cryo stages "effortlessly".They also had a significant share of pain but we cannot afford it. Guess what we had to put in a high altitude testing facilty at the last stage because we could not afford it and we still ahvent got full scale semicryo testing facilities and currently ahve to outsource it tll ours is built . They are not exactly cheap and we run on a shoe string budget.

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Re: Indian Space Programme Discussion - Sept 2016

Postby Lilo » 25 Sep 2016 10:15

^
Claiming launch at 2/3rd cost by some accounting gimmickry is passe -these claims of cheapness are based on PPP economics & massive state subsidized infra which never gets amortized into a rocket launch cost.

All serious pvt players are racing ahead with a business first paradigm, with minimum accounting gimmicry in their books in the quest to claim least cost per kilo.

ISRO or whoever it outsources to should build more rockets, more efficient rockets & grab a significant chunk (say 10%) of the launch market for starters.

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Re: Indian Space Programme Discussion - Sept 2016

Postby vina » 25 Sep 2016 12:40

prasannasimha wrote:So the sonic boom signature indeed has been recorded out to a distance of 35 Kms around Pulicat lake from the launch sit as per the article posted.

To quote the article

The PSLV lifted-off from SHAR with the trajectory
away from the line of the seismograph network. Hence
we could record the boom carpet that hit the Pulicat Lake
and produced the air-coupled seismic waves. The sonic
boom at the Pulicat Lake was experienced about 15–20 s
after the zero time and continued till about 35–40 s
(pers.
obs. by the authors).

The seismic waves produced due to the sonic boom of
Chandrayaan-1 were recorded till a distance of 35 km

So since we have the direct recordings of the boom carpet in the article in essence the sonic boom would be recorded. Also the very need for an acoustic suppression system probably indicates that the rocket plume hitting the stand during take off would probably set up significant shock waves too that need damping.

I stand corrected.
Now what do the other honorable members have to say when presented direct scientific peer reviewed data ?
Isn't this type of discussion more cogent ?


Is it ? But why are YOU corrected? . I DIDN'T read the article, I just saw your quote from it, and I immediately knew they were wrong and didn't even have to open it. Are what the writers of the article, presenting "scientific peer reviewed data" or are they using data to shoot their mouth off on things they have no idea about .

Now, the "Sonic BOOM , YouTube" video poster will jump up and say , "How Arrogant" . He does not even open the article and disses the whole thing ! And another round of expletives and this and that!

To which I will respond, dude, at 20 odds seconds and until 45 odd seconds, when you claim that you started recording a "Sonic Boom" the Vehicle is NOT supersonic. If it is not supersonic, there can no shock wave (no Prandtl Meyer expansion), and since no shock wave, no sonic boom .

Then the "Sonic Boom YouTube" dude will furiously write back and say, how do I know that the vehicle is not supersonic ? Did an article from ISRO say that it is so ? Is there some thing that you Googled out that said it so ? To which I will respond, The Mach number / speed of sound at low altitudes is around 1300 km/h and the vehicle definitely is not that fast!

Immediately, "Sonic Boom" dude will try to pull out "data" to "prove" that the vehicle is indeed that fast. I will pull out the PSLV C11 brochure and say that at 20s, the vehicle's speed 625m/s, but for the purpose you are talking about you should subtract 425m/s , so in effect that is really 200 m/s ! He wont understand why 425m/s needs to be subtracted, hewill go into a spin again on this and that, until finally common sense will prevail .

Then the question is "are the esteemed authors of the report and their equally esteemed peer reviewers" wrong ? Are the seismometers wrong? Absolutely not. The data is right. They did measure an over pressure event and sonic waves. But where they shot their mouth off on calling it a "Sonic Boom" , which by what is commonly accepted in science is not. Now "Sonic Boom YouTube" dude will jump up and say, in our "universe", this is what I call a sonic boom. I would say, good, you can stay in your parallel universe.

Then "Sonic Boom YouTube" dude will get very clever and say, ah, but the launch video I posted was of GSLV MKIII, how do you know that I didn't record a sonic boom for that ? To which I will point back to my original post. Then he will post this PSLV/Chandrayaan article again, and it is a rinse and repeat.

I short , like I said, this thread is a "Space Nukkad" . We have people presenting some random long range launch videos with a bunch of near Yahoos, swearing in the choicest expletives and the garbage is presented as a "Sonic Boom" and THAT should be what "Indian Space" is about.

Moral : Do trust your judgement and common sense. Just because someone claims something, they could be plainly wrong, even if coming from people, with formal qualifications and even if published in a "peer reviewed journal".

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Re: Indian Space Programme Discussion - Sept 2016

Postby schinnas » 25 Sep 2016 13:27

As an interested novice in these areas, i am benefitting heavily from the recent discussions between Vina, IndranilRoy and others. Please continue.

My only request to Vina is to moderate the tone of his/her posts, which seem to provoke others and derail the discussion away from the valid points he/she raises.

Discussing possible gaps in performance of ISRO's launch vehicles and trading ideas on how those can be overcome seems totally apt for this thread. If someone does not think these discussions are scientific enough, they should provide counter data points that can elevate the discussion. Just blindly clamouring for dissenting views to be shut down in this thread is very unfortunate and smacks of crude censorship.

Prohibiting any discussion that does not always glorify ISRO will make this a mere ISRO cheerleader thread and this thread could lose most of its readership or potential. Even if someone's post seems to be less respectful to ISRO because of choice of their words, we need to understand that vast majority of us spend time on this thread because we all want India to excel in this area and are well wishers of ISRO.

Some time ago, when I posted about the need to consider privatization of some aspects of ISRO, i met with strong negative reaction. I know of the delays and indecision that happen in ISRO from my interaction with tech companies who ISRO sub contacts to. Such inefficiencies would be quickly rectified if it was privatised under goverment supervision.

If we don't have open discussions on such topics, this thread will live in a lala land where ISRO is always right but continues to lag behind other major players in the world - public or private.

Note that of all govt enterprises, ISRO is the best, by a large margin. But does it compare in efficiency and speed of decision making to the best of breed companies? I don't think so (based on informed opinions of those who have worked extensively with ISRO as it's private partners and subcontractors). Unless we have open discussions on such topics, we will limit this thread to rah rah chorus for ISRO, which will not do it any good.

Just my 2c. Take it for what it's worth.


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