Great article.Why all the new tooling and techniques to build the core stage? Couldn't they have used the older Shuttle tank tooling? SLS is supposed to be a Shuttle derived vehicle. Would have save a lot of time and money.
Quote from: RonM on 05/08/2017 08:47 pmGreat article.Why all the new tooling and techniques to build the core stage? Couldn't they have used the older Shuttle tank tooling? SLS is supposed to be a Shuttle derived vehicle. Would have save a lot of time and money.No, the SLS is not "Shuttle derived". They share the same diameter, and they both use the same type of solid-rocket boosters, but otherwise the load paths and other considerations require completely different designs for the tank/stage assemblies, and they require different manufacturing methods.Kind of like comparing a Boeing 737 to a Boeing 777 - they look similar, but they are built completely different in how they are built.
Quote from: Coastal Ron on 05/08/2017 10:41 pmQuote from: RonM on 05/08/2017 08:47 pmGreat article.Why all the new tooling and techniques to build the core stage? Couldn't they have used the older Shuttle tank tooling? SLS is supposed to be a Shuttle derived vehicle. Would have save a lot of time and money.No, the SLS is not "Shuttle derived". They share the same diameter, and they both use the same type of solid-rocket boosters, but otherwise the load paths and other considerations require completely different designs for the tank/stage assemblies, and they require different manufacturing methods.Kind of like comparing a Boeing 737 to a Boeing 777 - they look similar, but they are built completely different in how they are built.The proper and more accurate way to phrase it is "Shuttle contractor derived".
Quote from: Lars-J on 05/08/2017 10:48 pmThe proper and more accurate way to phrase it is "Shuttle contractor derived".And there's the whole problem. Instead of something practical like the Direct Jupiter rocket that would have used modified Shuttle tanks, Congress served up a huge serving of pork to the contractors. We end up with the contractors using bleeding edge technology (most expensive) to build a rocket based on 40 year old engineering.
The proper and more accurate way to phrase it is "Shuttle contractor derived".
The history of STS replacement going back to the Clinton administration through today; X-33, Ares V, and SLS. Unless Boeing and friends can get their act together we're looking at another failed program. It would be funny except for the waste of billions of dollars.
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.
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...
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.
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?
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.
SLWT introduced Al-Li alloys, orthogrid structures, and (IIRC) friction stir welding.
Friction stir welding was used for SLWT beginning with ET-134, flown on STS-130. https://www.nasa.gov/centers/marshall/news/news/releases/2010/10-010.html