Quote from: Rocket Science on 05/09/2017 12:22 amJust a note on this joyride: recall that we were going from the ET 8.4m, then CxP proposed 10m, the SLS went with 8.4m for cost cutting and other efficiencies I'm sure...It went with 8.4m to support the claim that SLS is not Ares V redux. That and the silly black-and-white paint scheme.Additionally: an 8.4m core with two SRB's was the best option to prevent a major re-do of the LC-39B flame trench, because this configuration is exactly as wide as the shuttle configuration was.
Just a note on this joyride: recall that we were going from the ET 8.4m, then CxP proposed 10m, the SLS went with 8.4m for cost cutting and other efficiencies I'm sure...
I think this may be a symptom of the *extremely low* production rate.
Quote from: ChrisWilson68 on 05/09/2017 04:06 amIt's disturbing that they think it's OK to go ahead and use one of the bad tanks for structural testing, because it means that what they're testing is not the same as what they'll be flying.We already know that switching from pin design 1 to pin design 2 had some unintended consequences that aren't understood. We know that using pin design 2 gives certain kinds of weaknesses, and nobody knows why. So how can we be sure pin design 1 doesn't have different kinds of weaknesses that pin design 2 does not? By only doing structural testing on the tank built with pin design 2, they'll be missing any unexpected weaknesses in tanks made with pin design 1 that structural testing would have caught. But they plan to fly the tanks built with pin design 1, which will never have gone through structural testing.The only safe thing to do is throw away both of the first two H2 tanks and use the next two for structural testing and flight.Or saved them for eventual museum pieces?
It's disturbing that they think it's OK to go ahead and use one of the bad tanks for structural testing, because it means that what they're testing is not the same as what they'll be flying.We already know that switching from pin design 1 to pin design 2 had some unintended consequences that aren't understood. We know that using pin design 2 gives certain kinds of weaknesses, and nobody knows why. So how can we be sure pin design 1 doesn't have different kinds of weaknesses that pin design 2 does not? By only doing structural testing on the tank built with pin design 2, they'll be missing any unexpected weaknesses in tanks made with pin design 1 that structural testing would have caught. But they plan to fly the tanks built with pin design 1, which will never have gone through structural testing.The only safe thing to do is throw away both of the first two H2 tanks and use the next two for structural testing and flight.
Is the SLS tank significantly thicker than the ET, or is it just an unprecedented thickness for friction stir welding?
Plus the tanks are now the thrust structure between the main engines and the upper stage instead of just fuel tanks as in the ET.
I might be wrong, spacenut, but I think the problem is that the voids can only be detected through destructive testing. Consequently, the tanks are unsalvageable.
Quote from: Ben the Space Brit on 05/10/2017 02:45 pmI might be wrong, spacenut, but I think the problem is that the voids can only be detected through destructive testing. Consequently, the tanks are unsalvageable.The tank is not "unsalvageable" per se. The article on site states that evaluations are ongoing into how to save the tank. Whether or not they can "save" it in a manner that makes them confident enough to use it on a subsequent flight to EM-1 is a different matter.
NASA Watch @NASAWatch 26s26 seconds agoSources report #NASA looking at using the EM-2 SLS launch vehicle for EM-1 mission due to hydrogen tank issues on EM-1 vehicle @NASA_SLS
If the EM-3 tanks are used for EM-2 then a extra set of tank will be needed for EM-3. Extra cost.