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Default Space Launch System News
by Urwumpe 08-06-2015, 08:09 PM

Now you got me doing this. Well, somebody has to do it.

The SLS Block 1 configuration passed its Critical Design Review, the most important final milestone between R&D and entering production.

The other configurations will still have to follow through this milestone, but since their prime payloads are also not yet past CDR, it must wait.

http://www.nasa.gov/exploration/syst...y-to-mars.html

http://www.raumfahrer.net/news/raumf...15212623.shtml
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Old 08-14-2015, 11:56 AM   #2
orb
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A video from yesterday's RS-25 firing test:
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Old 08-14-2015, 12:23 PM   #3
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The RS-25 flew for 30 years.

Is there anything different about it now to make the test firing significant?
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Old 08-14-2015, 12:27 PM   #4
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Originally Posted by boogabooga View Post
 The RS-25 flew for 30 years.

Is there anything different about it now to make the test firing significant?

Yes, a lot, a NASA info-graphic explained a lot about this question.

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Old 08-14-2015, 03:53 PM   #5
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Quote:
Originally Posted by orb View Post
 A video from yesterday's RS-25 firing test:
Countdown to Deep Space - YouTube
I forgot that these RS-25s needed to burn for something like 8+ minutes for the shuttle (and for the SLS?) and were intended to be reusable. That's one tough engine. And they're uprating it for 109%? If they could squeeze out one more percent they could say that "This engine goes to 11".
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Old 08-14-2015, 03:58 PM   #6
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Quote:
Originally Posted by Thunder Chicken View Post
 I forgot that these RS-25s needed to burn for something like 8+ minutes for the shuttle (and for the SLS?) and were intended to be reusable. That's one tough engine. And they're uprating it for 109%? If they could squeeze out one more percent they could say that "This engine goes to 11".
Actually, it was already uprated to 109% RPL. But that power level was only supposed to be used for certain abort modes and was AFAIR never used during a mission.
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Old 08-14-2015, 05:15 PM   #7
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Interesting, makes a lot of sense to push those engines further as the constraint of reusability is lifted.
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Old 08-14-2015, 05:47 PM   #8
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Quote:
Originally Posted by Urwumpe View Post
 Actually, it was already uprated to 109% RPL. But that power level was only supposed to be used for certain abort modes and was AFAIR never used during a mission.
It will be now, and if it were me, I'd shift the scale. But I'm nobody so who cares what I think.
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Old 08-14-2015, 10:04 PM   #9
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Originally Posted by Urwumpe View Post
 Actually, it was already uprated to 109% RPL. But that power level was only supposed to be used for certain abort modes and was AFAIR never used during a mission.
This is correct. The Block II SSME which this really is was designed from outset to enable routine operation at 109%. However, this never happened due to a late discovered fact that prevented any long-term 109% throttle-levels and that fact was that the flow-liners in the orbiters just couldn't take the stresses associated with the 109% throttle level.

This was discovered in the summer of 2002 when several small cracks were found in the LH2 flow-liner of each orbiter. The cracks halted all the aft engine compartment work being done on the orbiters causing delays that lasted all summer and part of early fall.

---------- Post added 08-15-15 at 12:04 AM ---------- Previous post was 08-14-15 at 07:54 PM ----------

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Old 08-14-2015, 11:18 PM   #10
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...while watching the "Enlarge your Pe...gasus size" video I wondered:
Why is that core stage so much havier than the ET? Is it mainly the (4) Engines?
136,000 lbs vs. 800,000 lbs is a huge difference!
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Old 08-14-2015, 11:53 PM   #11
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I actually wondered that myself.

In addition to the weight of the engines though, the SLS core is also stretched more than the ET, and there is a different propellant feed system AND thrust structure since the RS-25s are at the base of the tank, rather than in an orbiter's MPS.
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Old 08-15-2015, 02:00 AM   #12
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Quote:
...while watching the "Enlarge your Pe...gasus size" video I wondered:
Why is that core stage so much havier than the ET? Is it mainly the (4) Engines?
136,000 lbs vs. 800,000 lbs is a huge difference!
Well, I'd say that the "vertical" configuration also puts more stress on the first stage, so it has to be reinforced (more sensitive to stuff like pogo oscillations ?). Maybe that the max-G and max-Q will be a bit higher too ?

Last edited by N_Molson; 08-15-2015 at 02:04 AM.
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Old 08-15-2015, 03:07 AM   #13
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Quote:
Originally Posted by N_Molson View Post
 Well, I'd say that the "vertical" configuration also puts more stress on the first stage, so it has to be reinforced (more sensitive to stuff like pogo oscillations ?). Maybe that the max-G and max-Q will be a bit higher too ?

Longer/taller stages must also be made stiffer as buckling is more of a concern.
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Old 08-15-2015, 03:26 AM   #14
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That's what she said...

Anyway, don't forget all the tank internals add weight also; baffles, pipes, instrumentation, etc. It all adds up.
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Old 08-15-2015, 06:34 PM   #15
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According to Spaceflight Now, some extra ablative material has also been added on the engine nozzle outside, for thermal shielding :

Quote:
Besides the new computer and higher pressures, the engines will get much hotter on the Space Launch System because the design puts them closer to the molten exhaust plume from the launcher’s twin solid rocket boosters.

“We’re going after several specific test objectives,” Wofford said. “One of those is to check the performance of the ablative material on the nozzle. The engines are co-planar with the boosters on SLS, so they see much higher temperature conditions. We’re adding ablative (material) to the outside of the nozzle to protect against that.”
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