Author Topic: SLS General Discussion Thread 8  (Read 150987 times)

Offline spacenut

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Re: SLS General Discussion Thread 8
« Reply #600 on: 10/01/2022 07:55 pm »
Is there anyway to send a camera inside of the solid boosters to check the condition of the solid material?  This would tell if they need to restack and repair or replace the solid material.


Offline DanClemmensen

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Re: SLS General Discussion Thread 8
« Reply #601 on: 10/01/2022 08:10 pm »
... IMO SLS/Orion is riskier. It must either fly in November or not fly for at least a year, based on rollout-rollback and SRB constraints. ...

You don't know that, unless you know more than what has been publicly revealed.
*Perhaps* a two year stack-time will be declared the maximum for those SRBs, but all we currently have from NASA is that they are tracking life-limited items and are revisiting and, where possible, reevaluating those limits as necessary.  At some point a true limit will be reached, but we've no idea just how finely they can "sharpen their pencils".
You are correct: I do not know that and I have no inside information. Furthermore, since this is an uncrewed flight they might choose to accept a larger risk of a failure than they would on a crewed flight. They risk embarrassment, not LOC. The fact that I'm concerned about synergistic effects of rollout counts plus SRB stack time does not mean that my concerns are valid.  Frankly, at this point they should probably take the risk, since the time to the next launch would probably be the the same whether they fly and RUD or scrub and de-stack, and in truth the probabitity of a failure due to exceeding one of these limits may not be excessive. Say it's 25%: that still gives a 75% chance of running the mission to see if everything else works.

You mention "the true limit". How do they determine that?

Offline kdhilliard

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Re: SLS General Discussion Thread 8
« Reply #602 on: 10/01/2022 08:19 pm »
...  Again hypothetically, what if Orion was on top of a Super Heavy Booster? 😱. That would likely be a pretty awful sight.
 
Be very careful what you wish for!
There is a guy on Twitter called 'The Cursed Rockets Guy'. He does what it says on the tin.
[Orion and ICPS on Superheavy]

Alternative rides for Orion was the subject of the most recent video from Apogee (Ken Kirtland): Are Rockets Like Legos?, with four Superheavy relate versions (Superheavy/ICPS; Superheavy/Centaur V; Superheavy/EUS; Superheavy/Simplified Expendable Starship) discussed starting at 17:12.  (Starting at 09:03 he discussed 3 Stage New Glenn; New Glenn/Centaur V; Falcon Heavy/Centaur V.)

Offline kdhilliard

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Re: SLS General Discussion Thread 8
« Reply #603 on: 10/01/2022 08:26 pm »
...
You mention "the true limit". How do they determine that?

Reporters have been trying to nail down such specifics with their questions during the various Artemis 1 related media briefings with no success to date.  (I suppose that it is simply an article of faith with me that a *some point* a nonextendable limit would be reached.  Though with as little information as NASA seems willing to share, I wouldn't be surprise if it was out of left field and not one of the main life-limited items the public is aware of.)

Offline clongton

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Re: SLS General Discussion Thread 8
« Reply #604 on: 10/02/2022 12:21 am »
Is there anyway to send a camera inside of the solid boosters to check the condition of the solid material?  This would tell if they need to restack and repair or replace the solid material.

No. Segment delamination since initial stacking that is sufficient to damage the propellant cohesion is not visible to the naked eye.
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I started my career on the Saturn-V F-1A engine

Offline clongton

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Re: SLS General Discussion Thread 8
« Reply #605 on: 10/02/2022 02:08 pm »
SpaceX would be very negative about it.
Have you ever met someone named Pollyanna at SpaceX?
Quote
No Orion, no need for SLS.
Yes as of now.  But there are other blocks for SLS.

Emphasis mine. I couldn't help myself after seeing this.
Far too many people are enamored by SLS just because it's such a big rocket. They willfully ignore the fact that it is - in fact - about as useful as a 3-legged horse in a race horse stable. The sooner we can get rid of this gawd-awful boondoggle the better off we will all be. Then we can focus our efforts and our treasure on things that actually contribute to a human spaceflight program that makes sense, a decent ROI and actually contribute to becoming a space fairing civilization; something that SLS not only cannot do, but actually prevents because of its truly unforgivable waste of time, effort and treasure. WRT Artemis, it's designed to give the Orion/SLS something to do. It will never allow us to do anything actually useful on the moon. We should be going there once a month, with regularly scheduled flights to service a robust lunar exploration and exploitation program, not once every year or so just so we can say we did the moon. We should be building an entire economy there to create a 2-planet economic system, not peeking out thru tiny windows at the lunar landscape once in a great while. SLS/Orion cannot - ever - support such a thing. It's a guarantee that we will NEVER do anything like that.

Having said that, I am not unmindful of the hopes and aspirations of the many SLS lovers, so I hope that this "thing" actually flies at least once for them, just so they can get their *VERY long-awaited* tingles, and then let it do exactly what the J-2X did - be permanently retired so we can get on with something useful.

Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline DanClemmensen

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Re: SLS General Discussion Thread 8
« Reply #606 on: 10/02/2022 02:27 pm »
...
You mention "the true limit". How do they determine that?

Reporters have been trying to nail down such specifics with their questions during the various Artemis 1 related media briefings with no success to date.  (I suppose that it is simply an article of faith with me that a *some point* a nonextendable limit would be reached.  Though with as little information as NASA seems willing to share, I wouldn't be surprise if it was out of left field and not one of the main life-limited items the public is aware of.)
This says to me that there is no "true limit" in the engineering sense. There is only a gradual acceptance of increasing risk: a slippery slope (or pick you metaphor of choice). The thinking would be that an attempt next month is only a little bit more risky than an attempt last month, and we do not have a quantitative assessment of risk, so we may as well keep going. We can only hope that this gamble pays off and we get a successful Artemis I mission.

Offline tea monster

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Re: SLS General Discussion Thread 8
« Reply #607 on: 10/02/2022 02:30 pm »
(snip)
Then we can focus our efforts and our treasure on things that actually contribute to a human spaceflight program that makes sense, a decent ROI and actually contribute to becoming a space fairing civilization; something that SLS not only cannot do, but actually prevents because of its truly unforgivable waste of time, effort and treasure. WRT Artemis, it's designed to give the Orion/SLS something to do. It will never allow us to do anything actually useful on the moon. We should be going there once a month, with regularly scheduled flights to service a robust lunar exploration and exploitation program, not once every year or so just so we can say we did the moon. We should be building an entire economy there to create a 2-planet economic system, not peeking out thru tiny windows at the lunar landscape once in a great while. SLS/Orion cannot - ever - support such a thing. It's a guarantee that we will NEVER do anything like that.
(snip)

This 1000%. Imagine any and every science fiction future where humans live on the moon. SLS/Orion is *actively preventing this* It's a hugely expensive, inefectual vehicle designed to conduct a pathfinder mission to the moon. We had our pathfinder missions 50 years ago. Now we should be travelling back to the moon with reuseable, sustainable, affordable means that establish a human presence on the moon that can be reliably maintained and built upon.

"Apollo on steroids" is NOT going to do any of that. Spending between two and four billion to launch one mission a year is absolutely crazy.
« Last Edit: 10/02/2022 02:31 pm by tea monster »

Offline DanClemmensen

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Re: SLS General Discussion Thread 8
« Reply #608 on: 10/02/2022 02:38 pm »
Is there anyway to send a camera inside of the solid boosters to check the condition of the solid material?  This would tell if they need to restack and repair or replace the solid material.

No. Segment delamination since initial stacking that is sufficient to damage the propellant cohesion is not visible to the naked eye.
I thought the SRB age limit related to the segment joints, specifically the adhesion of the PSA and the flexibility of the J-legs. I would have thought that the bulk propellant would last a longer time, based on the lifetime of other solid rocket motors like those in SLBMs.  Based solely on the diagrams, I speculate that your main point is still valid and that it is unlikely that anything is visible to show deterioration.

Offline JohnFornaro

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Re: SLS General Discussion Thread 8
« Reply #609 on: 10/02/2022 03:56 pm »
Imagine any and every science fiction future where humans live on the moon. SLS/Orion is *actively preventing this*...

SLS is effectively the same as the idea that we are being kept on planet.  Never ascribe to incompetence what should be described as intention, to put a different twist on an old saying.

Thing is, getting to the Moon is difficult.  The Chinese, with all of their IP theft, have not yet put a woman on the Moon.  What's not clear is how we could get to the Moon with the tech of half a centruy ago, but now cannot even launch.
Sometimes I just flat out don't get it.

Offline Robotbeat

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Re: SLS General Discussion Thread 8
« Reply #610 on: 10/02/2022 05:12 pm »
Too much focus on analysis and process above building and getting things done. Also, the tech we had then with rocketry was close to the optimal already (for expendables). And they had more money and wages were lower.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline oldAtlas_Eguy

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Re: SLS General Discussion Thread 8
« Reply #611 on: 10/02/2022 09:54 pm »
The only good thing I see coming from the SLS/Orion vehicles is that it can put the idea into the decision makers and funders that they can gain a place in the history books by funding the start of the population of the Moon and Mars. This is a group that is not just government but an even larger private funding source group. Some of which has already started to happen. Musk, Bezos, ...

Also there are three up and coming transport possibilities to get from Earth to the Moon: SpaceX-Starship, BO-NG/Blue Moon, ULA-Vulcan/CentaurV(distributed launch & some ACES tech)+payloads from third parties. ULA with some application of the ACES technologies they have laying on the table can develop fairly rapidly an Earth Departure Stage (EDS) developed from an upgrade to CentaurV where such is delivered as a payload to LEO. Where it loiters for up to several months possibility with low boiloff. Also with some judicious docking hardware that allows for multiple EDS to be stacked. Enables a dail a size to the Moon capability that could put payload modules of 30t+ each into NRHO. With higher launch activity and higher buid rates the cost per launch will decrease to the point of a delivery of a EDS to LEO including the cost of the EDS could be < $150M. Such that ULA could be launching Vulcans as fast as they can build them with trips of 30t of payload to Gateway every 3 months. Next is BO and NG+Jarvis+Blue Moon which would be a complete solution to the surface. Note that ULA offering delivery of 30t lots to Gateway could generate some additional landers to show up as well by third parties that hire ULA to get them there as a competition to BO. Then last is the best possible case of SpaceX and Starship but as I talked about earlier not the only one in the capabilities for high tonnage and often flight.

Alas these 3 others mentioned need to get their act together with some demonstrations as well as someone funding them at higher than current levels so that they can achieve more for less. This will take some time but likely less than what SLS/Orion will take to get to the 5th launch.

Offline sdsds

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Re: SLS General Discussion Thread 8
« Reply #612 on: 10/02/2022 10:19 pm »
SLS [is] about as useful as a 3-legged horse in a race horse stable.

I love this analogy! And I largely agree with you about why SLS and Orion are boondoggles. But to extend your analogy just a bit, the question isn't how many legs the horse has, it's whether or not she's a mare with good bloodlines.
— 𝐬𝐝𝐒𝐝𝐬 —

Offline Coastal Ron

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Re: SLS General Discussion Thread 8
« Reply #613 on: 10/02/2022 11:55 pm »
...
You mention "the true limit". How do they determine that?
Reporters have been trying to nail down such specifics with their questions during the various Artemis 1 related media briefings with no success to date.  (I suppose that it is simply an article of faith with me that a *some point* a nonextendable limit would be reached.  Though with as little information as NASA seems willing to share, I wouldn't be surprise if it was out of left field and not one of the main life-limited items the public is aware of.)
This says to me that there is no "true limit" in the engineering sense.

No, I think that is completely wrong. I'm not a fan of the SLS, but I know there have been a couple of limits that have been made public.

The SRB limits are probably the best known and understood given how long the Shuttle program was using similar SRB's, and unfortunately the only way to know if you have exceeded the limits on the SRB is to watch it launch and fail. And no one wants to that to happen, so being cautious should be OK.

IIRC there are structural concerns with the entire SLS stack, with some (or all) of that being caused by the shaking that occurs when the SLS is moved to the pad or back to the VAB.

Quote
There is only a gradual acceptance of increasing risk: a slippery slope (or pick you metaphor of choice).

There should be a concern at NASA regarding "Go Fever", where they feel they HAVE to launch. And certainly a lot of unwanted attention would happen if they have to de-stack and replace components of the SLS stack. I think they are aware of all of that though.

Quote
We can only hope that this gamble pays off and we get a successful Artemis I mission.

Lots of drama so far, that is for sure...
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline DanClemmensen

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Re: SLS General Discussion Thread 8
« Reply #614 on: 10/03/2022 12:53 am »
...
You mention "the true limit". How do they determine that?
Reporters have been trying to nail down such specifics with their questions during the various Artemis 1 related media briefings with no success to date.  (I suppose that it is simply an article of faith with me that a *some point* a nonextendable limit would be reached.  Though with as little information as NASA seems willing to share, I wouldn't be surprise if it was out of left field and not one of the main life-limited items the public is aware of.)
This says to me that there is no "true limit" in the engineering sense.

No, I think that is completely wrong. I'm not a fan of the SLS, but I know there have been a couple of limits that have been made public.

The SRB limits are probably the best known and understood given how long the Shuttle program was using similar SRB's, and unfortunately the only way to know if you have exceeded the limits on the SRB is to watch it launch and fail. And no one wants to that to happen, so being cautious should be OK.

IIRC there are structural concerns with the entire SLS stack, with some (or all) of that being caused by the shaking that occurs when the SLS is moved to the pad or back to the VAB.

Quote
There is only a gradual acceptance of increasing risk: a slippery slope (or pick you metaphor of choice).

There should be a concern at NASA regarding "Go Fever", where they feel they HAVE to launch. And certainly a lot of unwanted attention would happen if they have to de-stack and replace components of the SLS stack. I think they are aware of all of that though.

Quote
We can only hope that this gamble pays off and we get a successful Artemis I mission.

Lots of drama so far, that is for sure...
What I was trying to say is that kdhilliard was looking for a specific quantitative "true limit": an actual specific number that can be stated and evaluated, but  we can see that there is no such number. The engineers provided their numbers: 12 months for the SRB stack limit, 20 days for the FTS batteries, some specific number of roll-outs, and probably others we don't know. The program managers then asked the engineers to change those numbers, so they clearly were not "true limits".  Each of these "true limits" is actually a curve projecting increasing risk of failure over time, not a hard stop. If SLS/Orion were not so horrifically expensive, NASA would have a reasonable amount of spare hardware and they could have declared the entire current stack to be a test article. They have now learned how to stack an SLS/Orion system, and they could start fresh and launch within a year of starting to stack. But they cannot do this, so they will attempt an increasingly risky launch.

Offline Zed_Noir

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Re: SLS General Discussion Thread 8
« Reply #615 on: 10/03/2022 03:16 am »
Is there anyway to send a camera inside of the solid boosters to check the condition of the solid material?  This would tell if they need to restack and repair or replace the solid material.

No. Segment delamination since initial stacking that is sufficient to damage the propellant cohesion is not visible to the naked eye.
I thought the SRB age limit related to the segment joints, specifically the adhesion of the PSA and the flexibility of the J-legs. I would have thought that the bulk propellant would last a longer time, based on the lifetime of other solid rocket motors like those in SLBMs.  Based solely on the diagrams, I speculate that your main point is still valid and that it is unlikely that anything is visible to show deterioration.
Will point out that the solid rocket motors in strategic ballistic missiles are monolithic. AFAIK no strategic ballistic missile use segmented solid rocket motors.

Offline Coastal Ron

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Re: SLS General Discussion Thread 8
« Reply #616 on: 10/03/2022 03:47 am »
What I was trying to say is that kdhilliard was looking for a specific quantitative "true limit": an actual specific number that can be stated and evaluated, but  we can see that there is no such number. The engineers provided their numbers: 12 months for the SRB stack limit, 20 days for the FTS batteries, some specific number of roll-outs, and probably others we don't know. The program managers then asked the engineers to change those numbers, so they clearly were not "true limits".

Not an SLS supporter at all, but I would not be so harsh about the "limits" we hear about.

It would make sense for the SLS team to define what their "normal" limits will be for launch operations. Those "limits" would be based on lots of analysis that tries to define what the "worst case limits" are that would still allow for a launch.

So what I see is the SLS team is trying to do everything they can to stay in the "normal" range of limits. Then it is up to management to decide, which, if any, limits can be extended towards the "worst case limits".

As for the Flight Termination System (FTS), that is not something the SLS team controls, but the range does. And they would have their own process to understand what "normal" and "worst case limits" are. And their goal is range safety, so they are supposed to be insulated from any concerns about cost, saving face, national prestige, etc.

In other words, what we are seeing overall are planned changes in what is allowed for an SLS launch that is having trouble getting off the pad.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline DanClemmensen

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Re: SLS General Discussion Thread 8
« Reply #617 on: 10/03/2022 04:12 am »

In other words, what we are seeing overall are planned changes in what is allowed for an SLS launch that is having trouble getting off the pad.
I disagree. "Planned changes" would have been evaluated before stacking began, as contingencies. They would have established and published the evaluation criteria and reviewed them. What we are seeing instead are changes in the limits being made on the fly and under pressure of the schedule.

I still think they should go ahead and try to fly, because the chance of success is probably high and the consequences of failure are about the same as the consequences of deciding not to fly. But it would be better describe the situation so the public knows that the risks are increasing, if in fact that is the situation.

Offline DanClemmensen

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Re: SLS General Discussion Thread 8
« Reply #618 on: 10/03/2022 04:18 am »
Is there anyway to send a camera inside of the solid boosters to check the condition of the solid material?  This would tell if they need to restack and repair or replace the solid material.

No. Segment delamination since initial stacking that is sufficient to damage the propellant cohesion is not visible to the naked eye.
I thought the SRB age limit related to the segment joints, specifically the adhesion of the PSA and the flexibility of the J-legs. I would have thought that the bulk propellant would last a longer time, based on the lifetime of other solid rocket motors like those in SLBMs.  Based solely on the diagrams, I speculate that your main point is still valid and that it is unlikely that anything is visible to show deterioration.
Will point out that the solid rocket motors in strategic ballistic missiles are monolithic. AFAIK no strategic ballistic missile use segmented solid rocket motors.
I am aware of this. I took clongton's comment as referring to the bulk propellant in each segment, which I thought was roughly equivalent to the propellant in an unsegmented solid booster. The J-legs and PSA are elements of the intersegment seals, and are the only parts of the SRBs that I have seen described when the age limit was being discussed.

Offline tea monster

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Re: SLS General Discussion Thread 8
« Reply #619 on: 10/03/2022 09:16 am »
Too much focus on analysis and process above building and getting things done. Also, the tech we had then with rocketry was close to the optimal already (for expendables). And they had more money and wages were lower.

We don't need to spend a significant portion of our GDP on getting back to the Moon today. Even before SpaceX started re-using boosters and lowered the cost of getting to space, we could have designed our lunar exploration system around existing boosters and saved billions and got there a lot faster. Probably more sustainable too.

 

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