Author Topic: SLS General Discussion Thread 5  (Read 431466 times)

Offline tater

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Re: SLS General Discussion Thread 5
« Reply #1520 on: 03/23/2021 02:05 pm »
Those are not equivalent statements.

They are, actually.

That NASA has limited SLS to flying Orion is a statement of fact, there is nothing even penciled in for SLS that is "not Orion."

This is not the same as saying "NASA will never fly non-Orion payloads," it is literally saying "they have none scheduled now."

Until some other payload is manifested for SLS, there is zero reason to assume any if they are not being paid for already, certainly not in the time horizon of what dev time would be on such a payload, so just Orion as far as we can see right now.

This whole thread explosion nitpicking costs is irrelevant, IMO. The problem with SLS/Orion (they are tied together) is it lacks the capability to do useful missions by itself. It is expensive enough at 3+B$ per flight (NOT counting whatever dev costs might be controversial for some) that it should do, you know, something useful for that price tag.

Orion is ~26.5t. SLS TLI capability is ~27t, 37-40t, and ~45t for the different blocks, right?

SLS cannot get the only payload it has manifested—and that is the only crew vehicle even discussed for it, much less built—to the Moon and back with a lander of any size. Any comparison with Apollo would need to compare the mission success of a single launch, with no other launch vehicles save SLS. Apollo was designed to complete a mission, and it did. SLS/Orion is NOT designed to complete any mission, and it achieves this by not completing any mission. Nor can it, ever.

Not because of money, or SpaceX, etc, ad nauseum. Because of the rocket equation, and the fact that the one payload they decided had to be on top every time is too massive for their rocket (or their rocket is too small for their payload, pick one).
« Last Edit: 03/23/2021 02:06 pm by tater »

Offline ncb1397

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Re: SLS General Discussion Thread 5
« Reply #1521 on: 03/23/2021 02:20 pm »

"A vehicle that can only do Lunar flybys"

This one isn't even true, Jim, and you know it.


Until EUS finishes production, it is true.

Jim is entirely correct here. Which is why EM-3, the first planned landing on the surface, is at a minimum a THREE launch mission (at least):


A lunar flyby doesn't go into orbit. So, no, what Jim said isn't correct. Obviously Orion can go into lunar orbit and doing so doesn't require the Block 1B.

Offline rakaydos

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Re: SLS General Discussion Thread 5
« Reply #1522 on: 03/23/2021 02:26 pm »

"A vehicle that can only do Lunar flybys"

This one isn't even true, Jim, and you know it.


Until EUS finishes production, it is true.

Jim is entirely correct here. Which is why EM-3, the first planned landing on the surface, is at a minimum a THREE launch mission (at least):


A lunar flyby doesn't go into orbit. So, no, what Jim said isn't correct. Obviously Orion can go into lunar orbit and doing so doesn't require the Block 1B.
This isnt the Orion section of the forum. SLS cannot put it's payload into lunar orbit, it can only send it on it's way.

Offline tater

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Re: SLS General Discussion Thread 5
« Reply #1523 on: 03/23/2021 02:36 pm »

"A vehicle that can only do Lunar flybys"

This one isn't even true, Jim, and you know it.


Until EUS finishes production, it is true.

Jim is entirely correct here. Which is why EM-3, the first planned landing on the surface, is at a minimum a THREE launch mission (at least):


A lunar flyby doesn't go into orbit. So, no, what Jim said isn't correct. Obviously Orion can go into lunar orbit and doing so doesn't require the Block 1B.

The only SLS payload, Orion, can certainly insert itself into a distant lunar orbit, then return to Earth. It cannot insert into LLO and return to Earth, however.

I realize there are separate SLS/Orion threads, but they are inextricably linked as Orion is currently the payload for SLS, and it is not in fact optimized for SLS of any block to complete useful lunar missions. SLS Block 1B would require that the payload stack (CSM and lander) mass substantially less than the Apollo CSM/LM. Block 2 would presumably allow the CSM/Lander mass to exceed Apollo era capability. The CM would have to be "not Orion," however, as the Orion capsule is simply too heavy.

Online gongora

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Re: SLS General Discussion Thread 5
« Reply #1524 on: 03/23/2021 02:45 pm »
Looks like it's about time for Thread 6 to try and get this topic back on track.  We'll start the new thread shortly.

Offline AS_501

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Re: SLS General Discussion Thread 5
« Reply #1525 on: 05/12/2021 12:07 am »
Do the SLS SRB joints use the design same as STS?  Or more generally, are the SLS SRB joints strengthened in any way to accommodate each booster's greater weight, length between the attachment points and lateral loads caused by in-flight cross winds?  (I think lateral loading is called the 'Bending Moment').  Simarly, are the SLS SRB attachment points beefed up for the same reasons?  My guess is "no", that the extra segment is not enough to force any such design changes.
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Offline Avatar2Go

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Re: SLS General Discussion Thread 5
« Reply #1526 on: 05/12/2021 06:52 am »
The basic joint design is the same J-leg adopted after the Challenger accident, with improvements made throughout the remaining shuttle program, and then again with SLS.  Main difference is the substitution of rubber insulation for asbestos.  That has affected the design of the J-leg seals as well.  The heaters added to the joints after Challenger have been removed, as testing and experience showed the low-temp O-ring materials have performed well.

The booster attach points and structures are rated for the 130-ton design payload of SLS, AFAIK.  The booster aft skirts, which attach to the core stage engine section, carry most of the launch load.  The engine section was tested to 750,000 lbs static from the underside, and 3M lbs static on each side attachment point for the boosters.  Bending moments were measured in asymmetric thrust testing, but I don't have that data.  I'm sure the boosters were similarly structurally tested to the same specs.  Also I'm sure the boosters have undergone modal testing for flight loads, including aerodynamic. 

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