Author Topic: NASA defends decision to restart RS-25 production, rejects alternatives  (Read 54844 times)

Offline Jim

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FYI: It is, much cheaper and faster to develop than alternatives, uses existing knowledge-bases and infrastructure, weight is minimal, drag is reduced and it looks goooood (something engineers often forget is important).


not one of those is true.   And it certainly does not looks good. 
« Last Edit: 08/08/2017 02:05 PM by Jim »

Online Lars-J

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FYI: It is, much cheaper and faster to develop than alternatives, uses existing knowledge-bases and infrastructure, weight is minimal, drag is reduced and it looks goooood (something engineers often forget is important).


not one of those is true.   And it certainly does not looks good.

I guess I never noticed that boat tail before... This looks like a M+ (5,4) core - but this RS-68 protection doesn't seem to be used for all launches of that configuration. Was this just used for one of the early flights?
« Last Edit: 08/08/2017 05:43 PM by Lars-J »

Offline mike robel

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I know it doesn't appear on the Delta IV and it don't think it flies with a Delta without any SRMs, so only the M+,
« Last Edit: 08/08/2017 06:51 PM by mike robel »

Online Lars-J

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I know it doesn't appear on the Delta IV and it don't think it flies with a Delta without any SRMs, so only the M+,

But it doesn't appear on most M+ launches, it seems (see image with 4 SRBs), so that's why I'm wondering if it is a something that was only used for the first few launches.

(The only launch images that show the skirt/boattail appear to be from the GOES-N launch, although it could be present in some others - difficult to see in the glare of the SRBs)
« Last Edit: 08/08/2017 07:35 PM by Lars-J »

Offline Propylox

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Boattail description post; https://forum.nasaspaceflight.com/index.php?topic=38069.msg1706197#msg1706197
A.  There is no changing the 68 just for SLS.  It negates the benefit of sharing the same production line and flight history.
b.  Obviously, you didn't know that the boat tail didn't work on Delta IV so how do you know it is viable for this kludge. 
c.  There still is  radiant effect from boat tail to nozzle
d.  The large mass this huge boat tail is another strike against the "benefits" of the RS.
e. and there is the fore mentioned ISP issue that makes the core tanks too big.
a- No significant changes to 68's and certainly not any to effect their immaculate record. As mentioned the primary alterations are lengthening the GG exhaust and piping the purge lines to outside the boattail - so it doesn't explode upon ignition. A possibility is to remove, rather than simply disable roll control, and added ablative on the bottom few inches of the nozzle just in case.
b- DIV never shielded the nozzle and never introduced airflow inside the boattail as I've done. As mentioned the boattail extends below the nozzle with enough room for articulation. The space between the boattail and nozzle immediately develops a vacuum which is filled by the inlets beside the thrust structure, creating airflow.
c- Yep, the boattail will absorb (not reflect) and re-radiate heat including the thermal panels separating the engines. But this heat flux is much less than 68's get from GG exhaust recirulation, now eliminated by airflow, and what remains once out of the atmosphere is still insignificant.
d- Define "large". It's more than zero and adds to an already heavy engine, but that's irrelevant when compared to alternatives (PoR) it actually increases performance of the rocket, its safety, reliability, while reducing cost and development. Forest from the trees.
e- Love the pic and your experience actually building rockets, but a designer you're not. Reducing the core mass, propellant load and increasing the thrust increases the payload to orbit. Specific impulse is insignificant compared to a properly-design rocket with adequate thrust. I'd appreciate your input on Michoud's minor modifications necessary to build an actually functional SHLV.
6barrel core+68s+J-2X https://forum.nasaspaceflight.com/index.php?topic=38069.msg1705330#msg1705330

Offline Jim

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a- No significant changes to 68's and certainly not any to effect their immaculate record. As mentioned the primary alterations are lengthening the GG exhaust and piping the purge lines to outside the boattail - so it doesn't explode upon ignition. A possibility is to remove, rather than simply disable roll control, and added ablative on the bottom few inches of the nozzle just in case.
b- DIV never shielded the nozzle and never introduced airflow inside the boattail as I've done. As mentioned the boattail extends below the nozzle with enough room for articulation. The space between the boattail and nozzle immediately develops a vacuum which is filled by the inlets beside the thrust structure, creating airflow.

d- Define "large". It's more than zero and adds to an already heavy engine, but that's irrelevant when compared to alternatives (PoR) it actually increases performance of the rocket, its safety, reliability, while reducing cost and development. Forest from the trees.
e- Love the pic and your experience actually building rockets, but a designer you're not.
F.  Reducing the core mass, 
G.I'd appreciate your input on Michoud's minor modifications necessary to build an
H. actually functional SHLV.
i. 6barrel core+68s+J-2X

a.  Those are enough changes to affect the RS-68 and separate it from the Delta IV version.
b.  You haven't done any.  Much less produce a working design
d.  Exactly, Forest from the trees. This design is irrelevant.  POR is what it is. 
e.  You are neither.
f.  You are increasing it.
g.  I have nothing to do with Michoud or SLS design/production
h.  That would be SLS.  There isn't going to be anything else related.
i. There isn't going to be another vehicle that uses RS-68's or J-2X.  Both engine programs are dead or dead ends.

Offline Propylox

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I have nothing to do with Michoud or SLS design/production
Pity, as I only have images to derive dimensions of their facility. Notably the upper gantry crane appears high enough for a 6barrel core, but the lower crane isn't. After manufacturing is complete the core is given a shower, but the tub's lip is too high for a 6barrel to step over without hitting its head. I've a wet saw and spare time if they need a hand  ;D

Exactly, Forest from the trees. This design is irrelevant.  POR is what it is.
The program of record - SLS with it's design and mission decisions - is the tree. Human exploration is the forest that needs to be addressed. If the PoR, or RS-25, or administrators, or specific specs on mass and isp become the defining arguments, we've all lost site of the forest. The PoR and RS-25 "is what it is", which means they're sidenotes easily replace toward the goal of human exploration. If something better comes along, whether it's proposals I've made or others, do it. Forest from the trees.
« Last Edit: 08/10/2017 04:59 PM by Propylox »

Offline Jim

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The program of record - SLS with it's design and mission decisions - is the tree.

no, RS-68's, J-2s or SRB's are trees.

If something better comes along,

There will be nothing that is better that will/can come along with those components. 
Actually, "nothing" is better wrt those components.
Human exploration can be addressed without them

Forest from the trees.
« Last Edit: 08/10/2017 05:13 PM by Jim »

Offline Khadgars

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Propylox, I would appreciate it if you would stop beating a dead horse.  There is no need to hash this out any further.

It is as Jim states, RS-25 or bust for SLS and RL-10 for US.  If you want to discuss this further, please create a dedicated thread for that hypothetical as it has nothing to do with the POR.

Online okan170

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I know it doesn't appear on the Delta IV and it don't think it flies with a Delta without any SRMs, so only the M+,

But it doesn't appear on most M+ launches, it seems (see image with 4 SRBs), so that's why I'm wondering if it is a something that was only used for the first few launches.

(The only launch images that show the skirt/boattail appear to be from the GOES-N launch, although it could be present in some others - difficult to see in the glare of the SRBs)

I actually noticed this a bit ago while building the CG Delta IV, and asked Tory Bruno on twitter who referred me to ULA's official account.  Apparently it was an aero skirt that was only flown three times:

https://twitter.com/ulalaunch/status/811049041534603265

It'd be interesting to know more about this skirt and the reasons for its original inclusion and eventual deletion, but thats moving kind of off-topic for this thread.

Offline Jim

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It'd be interesting to know more about this skirt and the reasons for its original inclusion and eventual deletion, but thats moving kind of off-topic for this thread.

Protect the RS-68 from SRM heating

Online Lars-J

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I know it doesn't appear on the Delta IV and it don't think it flies with a Delta without any SRMs, so only the M+,

But it doesn't appear on most M+ launches, it seems (see image with 4 SRBs), so that's why I'm wondering if it is a something that was only used for the first few launches.

(The only launch images that show the skirt/boattail appear to be from the GOES-N launch, although it could be present in some others - difficult to see in the glare of the SRBs)

I actually noticed this a bit ago while building the CG Delta IV, and asked Tory Bruno on twitter who referred me to ULA's official account.  Apparently it was an aero skirt that was only flown three times:

https://twitter.com/ulalaunch/status/811049041534603265

It'd be interesting to know more about this skirt and the reasons for its original inclusion and eventual deletion, but thats moving kind of off-topic for this thread.

Thanks! I guess either they changed the SRB exhaust angle or they realized that the RS-68 did not need the added protection.

Offline Lar

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This thread is about the RS-25. It's not about Atlas, Delta, the RS-68, SpaceX, the Proton, or cheese. Or even LEGO elements!!! Yes some argument could be made that it's related but make sure it's clear in the posts how. Or we get people reporting...
« Last Edit: 08/11/2017 02:38 AM by Lar »
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Offline Propylox

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Propylox, I would appreciate it if you would stop beating a dead horse.
It is as Jim states, RS-25 or bust for SLS and RL-10 for US.  If you want to discuss this further, please create a dedicated thread for that hypothetical as it has nothing to do with the POR.
NASA defends decision to restart RS-25 production, rejects alternatives
What thread is acceptable to reject NASA's decision to use RS-25 and propose superior alternatives that reduces the cost per rocket (at least $200million per core), of the entire program (eliminates Advanced Boosters, creates a single and less expensive US) while increasing the safety, reliability and performance of SHLV for immediate use and mission funding instead of decades of further development?

The only "dead horse" here is the assertion that the PoR is infallible, the best, set in stone, and unquestionable! without addressing why it's so bad, why better options aren't being pursued, what those better options are, and why asking these valid questions in the dedicated thread is riling feathers without providing valid answers.
(Plus the contrary, grumpy assertion that SLS and any alternative will be cancelled, so don't talk about them).

SLS Mythbuster - I reject your reality and substitute my own.
« Last Edit: 08/12/2017 06:43 AM by Propylox »

Offline Endeavour_01

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The only "dead horse" here is the assertion that the PoR is infallible, the best, set in stone, and unquestionable!

I don't think anyone here has argued any of those things. You presented your ideas and were then presented with facts about how those ideas are unrealistic to implement. RS-25 is the best engine for SLS, especially at this stage of development.
I cheer for both NASA and commercial space. For SLS, Orion, Falcon 9, Falcon Heavy, Dragon, Starliner, Cygnus and all the rest!
I was blessed to see the launch of Space Shuttle Endeavour on STS-99. The launch was beyond amazing. My 8-year old mind was blown. I remember the noise and seeing the exhaust pour out of the shuttle as it lifted off. I remember staring and watching it soar while it was visible in the clear blue sky. It was one of the greatest moments of my life and I will never forget it.

Offline Jim

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The only "dead horse" here is the assertion that the PoR is infallible, the best, set in stone, and unquestionable! without addressing why it's so bad, why better options aren't being pursued, what those better options are, and why asking these valid questions in the dedicated thread is riling feathers without providing valid answers.
(Plus the contrary, grumpy assertion that SLS and any alternative will be cancelled, so don't talk about them).

Wrong on every count.
It is none of those things. There isn't going to be any money or desire to address any those things. There isn't a reason for SLS to exist in the first place.  So there is no reason to look for better options. It is SLS or nothing.
Govt managed launch vehicles are a dead end.  Especially, ones with no real mission. 

SLS is not going to be changed or upgraded.  There isn't going to be an SLS follow on.   NASA or the US govt has no need for such vehicles.  The RS-68 is at its end.  Production is almost finished.  EUS design is nearly finalized.  There is no champion for J-2X and hence it is dead.  Large segmented SRMs will be a thing of the past after SLS since Spacex, ULA, and Blue Origin don't need them

There isn't going to be any SLS alternative.  SLS is the POR and it is already on shaky ground.  There is no need, incentive or reason for an alternative.  Nor is there any drive to do so. 

Thinking otherwise means one has no concept of reality.
« Last Edit: 08/12/2017 01:22 PM by Jim »

Offline oldAtlas_Eguy

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The basic premise put forth by Congress was NASA only had X number of years to produce a SHLV. That timeline was insufficient for an engine development program. And we are seeing that even then without an engine development program that they are still not able to meet the stipulated schedule. If NASA had said in 2012 that it would take 10 years (2022) to do a first launch of SLS, Congress might not have created the program and killed Orion as well. Remember this was in FY2012 where there was only the investigations into Commercial Crew and commercial SHLVs (50+mt) were only power points with very questionable capabilities and very questionable schedules if they even came to exist. NASA could not say no they could not do it. Many other programs could have been hurt or even cancelled that NASA wanted very much.

So there was only the one choice for engine of the core and that was the RS-25. For the US there was options but the US program was unfunded and the design delayed until only recently. In order for the SLS with an US to hit the targets they needed a high ISP and light weight engine which the J-2X was not leaving the RL-10 as the only choice. What we have now is the result of a cascade of forced decisions a certain way all due to schedule pressure.

Offline M_Puckett

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"There isn't going to be any SLS alternative."

I disagree, depending on your definition of alternative.

Offline Jim

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"There isn't going to be any SLS alternative."

I disagree, depending on your definition of alternative.

A vehicle using shuttle based SRBs and MAF built tanks

Offline M_Puckett

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I'll buy that Jim.

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