Author Topic: First stage = 3 SRB  (Read 55809 times)

Offline Jim

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Re: First stage = 3 SRB
« Reply #20 on: 04/14/2006 01:07 pm »
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Ventrater - 14/4/2006  8:56 AMthank you Jim,but the tittle is: "first stage = 3 SRB"this is the first question. The question about the second stage comes after.  If you think that the idea is bad, then "why"? I do not think that this first stage would be the most expensive solution.

Why is that much thrust needed?   They have a short duration, they burn out at 120 seconds.  They get you off the pad but don't provide very much impulse.  On the Shuttle, the SRB's provide less than 10% of the energy required to get to orbit

Offline Ventrater

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Re: First stage = 3 SRB
« Reply #21 on: 04/14/2006 01:16 pm »
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Jim - 14/4/2006  8:07 AM

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Ventrater - 14/4/2006  8:56 AMthank you Jim,but the tittle is: "first stage = 3 SRB"this is the first question. The question about the second stage comes after.  If you think that the idea is bad, then "why"? I do not think that this first stage would be the most expensive solution.

Why is that much thrust needed?   They have a short duration, they burn out at 120 seconds.  They get you off the pad but don't provide very much impulse.  On the Shuttle, the SRB's provide less than 10% of the energy required to get to orbit
Yes, I know about the 10% (I was thinking: 15%) but if you think about the ariane5, the vulcain2 is only 135 tons thrust.  
And SRB are not very expensive and they already exist.    

Offline Jim

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Re: First stage = 3 SRB
« Reply #22 on: 04/14/2006 01:27 pm »
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Ventrater - 14/4/2006  9:16 AM
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Jim - 14/4/2006  8:07 AM
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Ventrater - 14/4/2006  8:56 AMthank you Jim,but the tittle is: "first stage = 3 SRB"this is the first question. The question about the second stage comes after.  If you think that the idea is bad, then "why"? I do not think that this first stage would be the most expensive solution.

Why is that much thrust needed?   They have a short duration, they burn out at 120 seconds.  They get you off the pad but don't provide very much impulse.  On the Shuttle, the SRB's provide less than 10% of the energy required to get to orbit
Yes, I know about the 10% (I was thinking: 15%) but if you think about the ariane5, the vulcain2 is only 135 tons thrust.  And SRB are not very expensive and they already exist.    

SRB's are expensive.  You have replace the "vulcian2" with a SRB, which is not an adequate trade

Offline Ventrater

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Re: First stage = 3 SRB
« Reply #23 on: 04/14/2006 01:38 pm »
SRB are expensive?
3 SRB = only $100million
then you add the second stage
and you have to compare with a 60 tons class launcher...
my idea is (2 * 60 tons = 120 tons)
then you compare with the costs of a 120 tons class launcher?

Offline Ventrater

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Re: First stage = 3 SRB
« Reply #24 on: 04/14/2006 01:41 pm »
I do not replace the "vulcian2" with a SRB, not at all. In my idea the second stage is above the first stage.
Like the VEGA launcher... or the "stick".

Offline Jim

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Re: First stage = 3 SRB
« Reply #25 on: 04/14/2006 01:59 pm »
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Ventrater - 14/4/2006  9:41 AMI do not replace the "vulcian2" with a SRB, not at all. In my idea the second stage is above the first stage. Like the VEGA launcher... or the "stick".

The 3 SRB's have plenty of thrust but not enough impulse.  Too much is depending on the second stage.   The stick is using a 5 segment SRM because of this

The costs of the SRB's is a lot higher than $25-33M

Offline Ventrater

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Re: First stage = 3 SRB
« Reply #26 on: 04/14/2006 02:11 pm »
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Jim - 14/4/2006  8:59 AM

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Ventrater - 14/4/2006  9:41 AMI do not replace the "vulcian2" with a SRB, not at all. In my idea the second stage is above the first stage. Like the VEGA launcher... or the "stick".

The 3 SRB's have plenty of thrust but not enough impulse.  Too much is depending on the second stage.   The stick is using a 5 segment SRM because of this

The costs of the SRB's is a lot higher than $25-33M
First: I am sure that one EAP (ariane SRB) is around $15million... and you say that one SRB is a a lot higher than $33 million... A few months ago I read that one 4 segments SRB is around $35million.
2- if "too much is depending on the second stage"... how much is depending on a first stage without SRB?
(if you are right then you are wrong)

Offline Ventrater

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Re: First stage = 3 SRB
« Reply #27 on: 04/14/2006 03:57 pm »
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Jim - 14/4/2006  8:59 AM

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Ventrater - 14/4/2006  9:41 AMI do not replace the "vulcian2" with a SRB, not at all. In my idea the second stage is above the first stage. Like the VEGA launcher... or the "stick".

The 3 SRB's have plenty of thrust but not enough impulse.  Too much is depending on the second stage.   The stick is using a 5 segment SRM because of this

The costs of the SRB's is a lot higher than $25-33M

No, the reason why NASA consider using a 5 segment is not because of the SRB have not enough impulse but because the SSME is too much difficult to modify (air-starting)!

Offline dmc6960

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Re: First stage = 3 SRB
« Reply #28 on: 04/14/2006 05:22 pm »
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Ventrater - 14/4/2006  10:57 AM

No, the reason why NASA consider using a 5 segment is not because of the SRB have not enough impulse but because the SSME is too much difficult to modify (air-starting)!

No, the reason why NASA switched to a 5 segment is because the only other large upperstage engine they have (when the SSME was deemed impractical) is the J-2.  That does not have as much thrust as the SSME, therefore, an extra segment to (try to) make up for it.

Why do you insist on this launcher when a rocket scientist has given multiple reasons why its not possible nor practical?
-Jim

Offline Ventrater

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Re: First stage = 3 SRB
« Reply #29 on: 04/14/2006 05:49 pm »
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dmc6960 - 14/4/2006  12:22 PM

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Ventrater - 14/4/2006  10:57 AM

No, the reason why NASA consider using a 5 segment is not because of the SRB have not enough impulse but because the SSME is too much difficult to modify (air-starting)!

No, the reason why NASA switched to a 5 segment is because the only other large upperstage engine they have (when the SSME was deemed impractical) is the J-2.  That does not have as much thrust as the SSME, therefore, an extra segment to (try to) make up for it.

Why do you insist on this launcher when a rocket scientist has given multiple reasons why its not possible nor practical?

Good question! Thank you for this question!
I insist because the first answer was "a triangular" configuration does not work... and I was waiting GOOD reasons to say: ok, my idea is not a ggod idea. But I can't say, now, that it is not a good idea because I see no good reasons, yet!!!

Last exemple (among many others): you say that the reason why NASA switched to a 5 segments is because the only large upperstage engine they have is the J-2. But this reason, precisely, is not:  3 SRB is a bad idea because """Too much is depending on the second stage""". So, because i want to think clearly, I say: I see no reason (yet) to abandon my idea!
Where do you see ONE good reason to not think about a 3 SRB first stage? Show me where, please.

Offline edkyle99

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Re: First stage = 3 SRB
« Reply #30 on: 04/14/2006 05:56 pm »
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Ventrater - 13/4/2006  3:05 PM

Since a long time I think that this launcher could be very interesting:
first stage = 3 SRB
second stage = 1 RS 68
LEO: 65 tons
What do you think ?

I don't see how you can get a 65 tonne payload.  Three SRBs would produce about 4271 tonnes of liftoff thrust.  The SRBs appear to work best at a 1.7 thrust to weight ratio (i.e. STS and CLV), so your maximum launch vehicle GLOW would be 2512 tonnes, 1759 tonnes of which would be SRBs.  That leaves 753 tonnes for second stage, payload, fairing, interstage, etc.  But since the SRBs would burn out at such a low velocity, your RS-68 powered upper stage (lets assume for the sake of argument that an air-start RS-68 would be do-able) would have to have an initial thrust to weight ratio of about 1.0, or perhaps a bit less than 1.0.  That limits your upper stage and payload to about 350 tonnes.  If the upper stage has a propellant mass fraction of 0.89 (like the planned Crew Launch Vehicle upper stage), then your payload to low earth orbit would only be 35-38 tonnes.  2512 tonnes (heavier than a space shuttle stack) is a lot of launch vehicle for such a relatively small payload.  

 - Ed Kyle      


Offline Ventrater

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Re: First stage = 3 SRB
« Reply #31 on: 04/14/2006 06:10 pm »
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edkyle99 - 14/4/2006  12:56 PM

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Ventrater - 13/4/2006  3:05 PM

Since a long time I think that this launcher could be very interesting:
first stage = 3 SRB
second stage = 1 RS 68
LEO: 65 tons
What do you think ?

I don't see how you can get a 65 tonne payload.  Three SRBs would produce about 4271 tonnes of liftoff thrust.  The SRBs appear to work best at a 1.7 thrust to weight ratio (i.e. STS and CLV), so your maximum launch vehicle GLOW would be 2512 tonnes, 1759 tonnes of which would be SRBs.  That leaves 753 tonnes for second stage, payload, fairing, interstage, etc.  But since the SRBs would burn out at such a low velocity, your RS-68 powered upper stage (lets assume for the sake of argument that an air-start RS-68 would be do-able) would have to have an initial thrust to weight ratio of about 1.0, or perhaps a bit less than 1.0.  That limits your upper stage and payload to about 350 tonnes.  If the upper stage has a propellant mass fraction of 0.89 (like the planned Crew Launch Vehicle upper stage), then your payload to low earth orbit would only be 35-38 tonnes.  2512 tonnes (heavier than a space shuttle stack) is a lot of launch vehicle for such a relatively small payload.  

 - Ed Kyle      

thank you for this clear answer!
I have underestimated the low RS 68 isp (when compared whith the J-2).
(one SRB + J-2 = 25 tons... and 3 SRB + 3 J-2 = 75 tons, correct?).
So, the difference between 75 and 65 is underestimated, ok
But the question about a 3 SRB first stage is still open, no?

Offline Jim

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Re: First stage = 3 SRB
« Reply #32 on: 04/14/2006 06:23 pm »
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Ventrater - 14/4/2006  2:10 PM
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edkyle99 - 14/4/2006  12:56 PM
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Ventrater - 13/4/2006  3:05 PMSince a long time I think that this launcher could be very interesting: first stage = 3 SRB second stage = 1 RS 68 LEO: 65 tons What do you think ?
I don't see how you can get a 65 tonne payload.  Three SRBs would produce about 4271 tonnes of liftoff thrust.  The SRBs appear to work best at a 1.7 thrust to weight ratio (i.e. STS and CLV), so your maximum launch vehicle GLOW would be 2512 tonnes, 1759 tonnes of which would be SRBs.  That leaves 753 tonnes for second stage, payload, fairing, interstage, etc.  But since the SRBs would burn out at such a low velocity, your RS-68 powered upper stage (lets assume for the sake of argument that an air-start RS-68 would be do-able) would have to have an initial thrust to weight ratio of about 1.0, or perhaps a bit less than 1.0.  That limits your upper stage and payload to about 350 tonnes.  If the upper stage has a propellant mass fraction of 0.89 (like the planned Crew Launch Vehicle upper stage), then your payload to low earth orbit would only be 35-38 tonnes.  2512 tonnes (heavier than a space shuttle stack) is a lot of launch vehicle for such a relatively small payload.   - Ed Kyle      
thank you for this clear answer! I have underestimated the low RS 68 isp (when compared whith the J-2). (one SRB + J-2 = 25 tons... and 3 SRB + 3 J-2 = 75 tons, correct?). So, the difference between 75 and 65 is underestimated, okBut the question about a 3 SRB first stage is still open, no?

(one SRB + J-2 = 25 tons... and 3 SRB + 3 J-2 = 75 tons, correct?  this is not true.  Each case has to be analysed.  Thay are not additive.  Other than the "unique" stick, SRB's are for assisting liftoff and early flight.  A better first stage can be found or designed.  Plus the hardware/truss to connect the 3 SRB's would be heavy.


Offline Ventrater

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Re: First stage = 3 SRB
« Reply #33 on: 04/14/2006 06:36 pm »
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Jim - 14/4/2006  1:23 PM

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Ventrater - 14/4/2006  2:10 PM
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edkyle99 - 14/4/2006  12:56 PM
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Ventrater - 13/4/2006  3:05 PMSince a long time I think that this launcher could be very interesting: first stage = 3 SRB second stage = 1 RS 68 LEO: 65 tons What do you think ?
I don't see how you can get a 65 tonne payload.  Three SRBs would produce about 4271 tonnes of liftoff thrust.  The SRBs appear to work best at a 1.7 thrust to weight ratio (i.e. STS and CLV), so your maximum launch vehicle GLOW would be 2512 tonnes, 1759 tonnes of which would be SRBs.  That leaves 753 tonnes for second stage, payload, fairing, interstage, etc.  But since the SRBs would burn out at such a low velocity, your RS-68 powered upper stage (lets assume for the sake of argument that an air-start RS-68 would be do-able) would have to have an initial thrust to weight ratio of about 1.0, or perhaps a bit less than 1.0.  That limits your upper stage and payload to about 350 tonnes.  If the upper stage has a propellant mass fraction of 0.89 (like the planned Crew Launch Vehicle upper stage), then your payload to low earth orbit would only be 35-38 tonnes.  2512 tonnes (heavier than a space shuttle stack) is a lot of launch vehicle for such a relatively small payload.   - Ed Kyle      
thank you for this clear answer! I have underestimated the low RS 68 isp (when compared whith the J-2). (one SRB + J-2 = 25 tons... and 3 SRB + 3 J-2 = 75 tons, correct?). So, the difference between 75 and 65 is underestimated, okBut the question about a 3 SRB first stage is still open, no?

(one SRB + J-2 = 25 tons... and 3 SRB + 3 J-2 = 75 tons, correct?  this is not true.  Each case has to be analysed.  Thay are not additive.  Other than the "unique" stick, SRB's are for assisting liftoff and early flight.  A better first stage can be found or designed.  Plus the hardware/truss to connect the 3 SRB's would be heavy.

Interresting! Thank you.
I note the huge difference between your first answer and the last: now there is something to analyse...
If 3 SRB + 3 J-2 is not 75 but only 70 or 65 tons, then it is yet a good idea. Isent'it?

Offline Jim

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Re: First stage = 3 SRB
« Reply #34 on: 04/14/2006 06:44 pm »
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Jim - 14/4/2006  2:23 PM

A better first stage can be found or designed.  Plus the hardware/truss to connect the 3 SRB's would be heavy.


I said it above. 

Offline Ventrater

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Re: First stage = 3 SRB
« Reply #35 on: 04/14/2006 06:52 pm »
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Jim - 14/4/2006  1:44 PM

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Jim - 14/4/2006  2:23 PM

A better first stage can be found or designed.  Plus the hardware/truss to connect the 3 SRB's would be heavy.


I said it above.  
Ok, I am not a rocket scientist and I yield to your arguments: it is not a good idea. A 3 SRB first stage is not a good idea.
But a last question, please: do you think that the "stick" is not a good idea too?

Offline Jim

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Re: First stage = 3 SRB
« Reply #36 on: 04/14/2006 06:56 pm »
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Ventrater - 14/4/2006  2:52 PM
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Jim - 14/4/2006  1:44 PM
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Jim - 14/4/2006  2:23 PM

A better first stage can be found or designed.  Plus the hardware/truss to connect the 3 SRB's would be heavy.


I said it above.  
Ok, I am not a rocket scientist and I yield to your arguments: it is not a good idea. A 3 SRB first stage is not a good idea. But a last question, please: do you think that the "stick" is not a good idea too?

I think it is bad

Offline Ventrater

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Re: First stage = 3 SRB
« Reply #37 on: 04/14/2006 06:58 pm »
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Jim - 14/4/2006  1:56 PM

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Ventrater - 14/4/2006  2:52 PM
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Jim - 14/4/2006  1:44 PM
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Jim - 14/4/2006  2:23 PM

A better first stage can be found or designed.  Plus the hardware/truss to connect the 3 SRB's would be heavy.


I said it above.  
Ok, I am not a rocket scientist and I yield to your arguments: it is not a good idea. A 3 SRB first stage is not a good idea. But a last question, please: do you think that the "stick" is not a good idea too?

I think it is bad
I know someone who does not like solids too. His name is Odo.

Offline Ventrater

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Re: First stage = 3 SRB
« Reply #38 on: 04/14/2006 08:32 pm »
I know that some rocket scientists think that the "stick" is a good idea. Maybe I could ask to these scientists what they think about a 3 SRB launcher? I bet that some of them will think that this is a good idea!

Offline edkyle99

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Re: First stage = 3 SRB
« Reply #39 on: 04/15/2006 02:15 am »
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Ventrater - 14/4/2006  1:10 PM

Quote
edkyle99 - 14/4/2006  12:56 PM

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Ventrater - 13/4/2006  3:05 PM

Since a long time I think that this launcher could be very interesting:
first stage = 3 SRB
second stage = 1 RS 68
LEO: 65 tons
What do you think ?

I don't see how you can get a 65 tonne payload.  Three SRBs would produce about 4271 tonnes of liftoff thrust.  The SRBs appear to work best at a 1.7 thrust to weight ratio (i.e. STS and CLV), so your maximum launch vehicle GLOW would be 2512 tonnes, 1759 tonnes of which would be SRBs.  That leaves 753 tonnes for second stage, payload, fairing, interstage, etc.  But since the SRBs would burn out at such a low velocity, your RS-68 powered upper stage (lets assume for the sake of argument that an air-start RS-68 would be do-able) would have to have an initial thrust to weight ratio of about 1.0, or perhaps a bit less than 1.0.  That limits your upper stage and payload to about 350 tonnes.  If the upper stage has a propellant mass fraction of 0.89 (like the planned Crew Launch Vehicle upper stage), then your payload to low earth orbit would only be 35-38 tonnes.  2512 tonnes (heavier than a space shuttle stack) is a lot of launch vehicle for such a relatively small payload.  

 - Ed Kyle      

thank you for this clear answer!
I have underestimated the low RS 68 isp (when compared whith the J-2).
(one SRB + J-2 = 25 tons... and 3 SRB + 3 J-2 = 75 tons, correct?).
So, the difference between 75 and 65 is underestimated, ok
But the question about a 3 SRB first stage is still open, no?

First you must note that the 5-segment/J-2X "Stick" is not designed to
actually put 25 tonnes into a circular low earth orbit.  Its reference
insertion "orbit" is only 55.6 x 296.3 km x 28.5 degrees - actually not
a stable earth orbit but a transfer orbit that requires the CEV "payload"
to fire its engines at first apogee.  The "Stick" will really only be able
to put about 22 tonnes or less into a stable low earth orbit.  

If you tripled the launch vehicle size (three 5-seg SRB first stage with
a second stage powered by three J-2X engines), the enlarged launcher
would be able to boost about 65 tonnes into a stable low earth orbit.  
This is more reasonable than the single engine RS-68 upper stage
idea.  The launcher would weigh about 2124 tonnes at liftoff, and
so would have a liftoff mass/payload ratio of about 33, which is
roughly in the same class as Zenit 2, Proton, Saturn IB, Ariane 5,
etc.

One big problem with this design, however, would be that the upper
stage diameter would be limited by the 3.71 meter diameter of the
core SRB.  It would be difficult to figure out how to attach a stage
that could carry about 384 tonnes of LH2/LOX to such a small core.  
This would be a stage that would have to possess as much propellant
volume as *two* Delta IV CBCs.  (Each CBC is 5.1 meters in
diameter and 36.6 meters long - almost as long as an SRB).  Any
interstage attachment would have to be able to transfer the weight of
about 500 tonnes of upper stage and payload mass to the SRB.

 - Ed Kyle

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