bombay - 4/2/2007 11:24 PMWhat of the possibility of using the current Delta II 2nd and 3rd stages on Atlas V with a modified interstage adapter? Is that being considered? What am I missing in my thought process?
Kayla - 4/2/2007 7:32 PMFrom its inception WBC was freed of this limitation. Originally the assumption was that the tank would be built at Michoud where three 5.4m demonstration hoops were assembled and lap welded together to demonstrate the planned construction using thin (0.080") al-li sheet stock. With the formation of ULA, ULA now has the option of using either Michoud or Decatur for construction. Either location has the ability to friction stir weld large diameter tanks and then ship the final structures to the Cape or Vandenberg.WBC is designed to merge the extremely efficient monocoque, common bulkhead tank from the historic Centaur with modern materials and friction stir welding spear headed for space application by the external tank and Delta programs. This combination, along with increased propellant load allows the WBC to increase the mass fraction from the current Centaur's 0.91 to 0.94! The following paper provides additional information.http://www.lockheedmartin.com/data/assets/12382.pdf
bombay - 5/2/2007 9:45 PMThe common bkhd concept would utilize a delta p between the LH2 tank and LOX tank. Lets say maximum flight pressure in the tank is 50 psi (this is probably low). So here's a simple analysis using ONLY pressure loading.
Jim - 5/2/2007 8:49 PMQuotebombay - 5/2/2007 9:45 PMThe common bkhd concept would utilize a delta p between the LH2 tank and LOX tank. Lets say maximum flight pressure in the tank is 50 psi (this is probably low). So here's a simple analysis using ONLY pressure loading. That is too high
Okay to GTO, Atlas 552 with WBC is 12.9 mT. Delta Heavy is 13.1 mT. Close but Delta Heavy still has a slight 200 kg edge.
The Centaur has to be kept "in stretch" or under pressure at all times. It just means it has to be monitored. Most of the pressure monitoring is automated (use to require a tech onsite at all times).
Jim - 4/2/2007 3:16 PMQuotebombay - 4/2/2007 6:05 PMQuoteyinzer - 4/2/2007 4:52 PMQuotebombay - 4/2/2007 9:58 AMYou have to ask the question, why did Atlas V settle on 12.5 ft dia. versus going to 17 ft like the Delata IV? Existing Titan tooling and factory size pretty much dictated the choice to use a 12.5 ft. diameter Atlas V booster.I'm curious as to how existing Titan tooling lead to the 12.5 ft diameter Atlas V booster. All Titan stages (except the Centaur G, which doesn't apply in this case) were 10 ft diameter.Titan IV tooling could accomodate up to 12.5 ft diameter without significant remods.The Titan tooling is not used for the Atlas V. All new tooling was created. The domes and panels are produced by subcontractors. Welding is only done in Denver.
bombay - 4/2/2007 6:05 PMQuoteyinzer - 4/2/2007 4:52 PMQuotebombay - 4/2/2007 9:58 AMYou have to ask the question, why did Atlas V settle on 12.5 ft dia. versus going to 17 ft like the Delata IV? Existing Titan tooling and factory size pretty much dictated the choice to use a 12.5 ft. diameter Atlas V booster.I'm curious as to how existing Titan tooling lead to the 12.5 ft diameter Atlas V booster. All Titan stages (except the Centaur G, which doesn't apply in this case) were 10 ft diameter.Titan IV tooling could accomodate up to 12.5 ft diameter without significant remods.
yinzer - 4/2/2007 4:52 PMQuotebombay - 4/2/2007 9:58 AMYou have to ask the question, why did Atlas V settle on 12.5 ft dia. versus going to 17 ft like the Delata IV? Existing Titan tooling and factory size pretty much dictated the choice to use a 12.5 ft. diameter Atlas V booster.I'm curious as to how existing Titan tooling lead to the 12.5 ft diameter Atlas V booster. All Titan stages (except the Centaur G, which doesn't apply in this case) were 10 ft diameter.
bombay - 4/2/2007 9:58 AMYou have to ask the question, why did Atlas V settle on 12.5 ft dia. versus going to 17 ft like the Delata IV? Existing Titan tooling and factory size pretty much dictated the choice to use a 12.5 ft. diameter Atlas V booster.
bombay - 4/2/2007 9:02 PMQuoteKayla - 4/2/2007 7:32 PMAtlas V's 12.5' diameter was driven by the need to air lift the long booster tank.Titan Centaur was 14' dia. and air lifted, though obviously not as long as the booster.
Kayla - 4/2/2007 7:32 PMAtlas V's 12.5' diameter was driven by the need to air lift the long booster tank.
kevin-rf - 5/2/2007 2:28 PMOkay to GTO, Atlas 552 with WBC is 12.9 mT. Delta Heavy is 13.1 mT. Close but Delta Heavy still has a slight 200 kg edge.So for GTO missions developing Atlas 552 WBC would make more sense than developing Atlas V Heavy which gunther lists as 12.6 mT to GTO. (That is assuming five solids, a single common core, and a WBC costs less than three common core Atlas booster and a standard Centuar). Thanks
Gus - 5/2/2007 10:13 PMThe Titan weld cell in the second floor factory is used to weld barrels for Atlas V. The new tooling is some handling equipment to handle skin panels and prep joints for weld. All this will move to Decatur with an emphasis on the friction stir welded longitudinal welds. The circumferential welds are still conventional arc welds. The weld cell could accomodate up to a 13 foot diameter but constraints of C-5 and Antonov constrained the diameter to 12.5.
quark - 9/2/2007 3:37 AMQuotekevin-rf - 5/2/2007 2:28 PMOkay to GTO, Atlas 552 with WBC is 12.9 mT. Delta Heavy is 13.1 mT. Close but Delta Heavy still has a slight 200 kg edge.So for GTO missions developing Atlas 552 WBC would make more sense than developing Atlas V Heavy which gunther lists as 12.6 mT to GTO. (That is assuming five solids, a single common core, and a WBC costs less than three common core Atlas booster and a standard Centuar). ThanksThe WBC is about 4 times the cost to finish Atlas V HLV. The AV HLV is essentially developed having completed CDR and qualification testing. All that remains is buying and installing additional ground support equipment and finishing up a handful of unique components like separation motors for the LRB's.
bombay - 5/2/2007 8:45 PMQuoteKayla - 4/2/2007 7:32 PMFrom its inception WBC was freed of this limitation. Originally the assumption was that the tank would be built at Michoud where three 5.4m demonstration hoops were assembled and lap welded together to demonstrate the planned construction using thin (0.080") al-li sheet stock. With the formation of ULA, ULA now has the option of using either Michoud or Decatur for construction. Either location has the ability to friction stir weld large diameter tanks and then ship the final structures to the Cape or Vandenberg.WBC is designed to merge the extremely efficient monocoque, common bulkhead tank from the historic Centaur with modern materials and friction stir welding spear headed for space application by the external tank and Delta programs. This combination, along with increased propellant load allows the WBC to increase the mass fraction from the current Centaur's 0.91 to 0.94! The following paper provides additional information.http://www.lockheedmartin.com/data/assets/12382.pdfVery interesting! I'm surprised that lap joints are used given that they are analyzed in shear, not tension or compression where the allowables are much higher.I'm guessing that the shear allowable for Al-Li is comparable to other 2XXX series aluminums: Fsu = 35 ksi and the welded allowable: Fsu = 20 ksi. Realizing that fric. stir welding produces excellent as welded allowables, I would guess that in an analysis, 80% of 35 ksi would conservatively be used. Lets say 30 ksi is used for the as-welded shear allowable.The common bkhd concept would utilize a delta p between the LH2 tank and LOX tank. Lets say maximum flight pressure in the tank is 50 psi (this is probably low). So here's a simple analysis using ONLY pressure loading. I'll spare everybody the math, but the longitudinal line load would be 1800 lb/in and the stress would be 22.5 ksi using .080" mat'l. Using a man-rated f.s. of 1.4, the m.s. would be -0.05 (ult).Throw in S.V. bearing loads, interstage adapter, fairing, and bending loads and all other dynamic and transient axial loading, you could see where the guage thickness would need to be much thicker, which in-turn would alter mass ratio.The .94 appears to be a goal, not a given.
bombay - 9/2/2007 10:39 AMI suspect if mega funds are going to be invested in something, it will be (and should be) in the U.S. development of the RD-180 given the recent events of Sea Luanch and the potential impact on Atlas V.
In addition, the mock analysis that I did a few posts ago was incorrect, I used 12 ft as the tank diameter instead of 17.5 ft. So the m.s. would be -0.67 ultimate not -0.05. The point of this is that .080" thick wall appears to be the thickness needed to produce a .94 mass fraction rather than what is actually needed to provide structural integrity. Something in the neighborhood of .150" thick or more would be the more appropriate thickness needed to provide positive margins.