My question is, why did the original design of CST-100 with the stumpy adapter pass muster? They wind tunnel tested it some time back and it was made the baseline design. What changed, and why?
Quote from: edkyle99 on 10/17/2016 06:21 pmQuote from: SWGlassPit on 10/17/2016 02:52 pmYou're looking at the difference between designing a spacecraft to go on top of a pre-existing launch vehicle design that is outside of the original use concept vs contemporaneous spacecraft and launch vehicle design.My question is, why did the original design of CST-100 with the stumpy adapter pass muster? They wind tunnel tested it some time back and it was made the baseline design. What changed, and why? - Ed KyleWe don't know if it passed muster. Nothing could have changed, just more testing was done
Quote from: SWGlassPit on 10/17/2016 02:52 pmYou're looking at the difference between designing a spacecraft to go on top of a pre-existing launch vehicle design that is outside of the original use concept vs contemporaneous spacecraft and launch vehicle design.My question is, why did the original design of CST-100 with the stumpy adapter pass muster? They wind tunnel tested it some time back and it was made the baseline design. What changed, and why? - Ed Kyle
You're looking at the difference between designing a spacecraft to go on top of a pre-existing launch vehicle design that is outside of the original use concept vs contemporaneous spacecraft and launch vehicle design.
Mass issues are common in aerospace. Even Shuttle had them. When you design a new vehicle from the ground up, you estimate as best you can, and you include a growth allowance to account for things you haven't designed yet. You design a big-picture concept, you do some analysis, you refine details, you do more analysis, you add more detailed design, lather, rinse, repeat.The problem is that every little screw, every little threaded insert, every inch of wire, every wire clip, every thousandth of an inch of wall thickness has mass, and it all adds up. Now, were your estimates three years ago good enough? Was your mass growth allowance enough? What if you identified a problem late in the game that required a redesign? Is it mass neutral?Don't forget also that you have to make design trades throughout the development life cycle. A big one fighting against mass is cost. Lighter weight components are more expensive to design. They are more expensive to analyze. They are more expensive to manufacture. Decisions have to be made based on these mass-cost trades, but the information you have early in the design stage is different from the information you have later on, so which fixed budget do you blow, your fiscal budget or your mass budget?
Mass issues are common in aerospace. Even Shuttle had them. When you design a new vehicle from the ground up, you estimate as best you can, and you include a growth allowance to account for things you haven't designed yet. You design a big-picture concept, you do some analysis, you refine details, you do more analysis, you add more detailed design, lather, rinse, repeat.The problem is that every little screw, every little threaded insert, every inch of wire, every wire clip, every thousandth of an inch of wall thickness has mass, and it all adds up. Now, were your estimates three years ago good enough? Was your mass growth allowance enough? What if you identified a problem late in the game that required a redesign? Is it mass neutral?
We all know this (or most of us do) - but this is why you always design with mass margins. Clearly something out of the ordinary must have happened here to require *two* solid boosters instead of zero.And those added booster's aren't "free", they do add to the launch cost and decrease the safety by some amount. Boeing seems happy with the tradeoffs, it seems.
I can't remember CST ever being "officially" on Atlas 401/402. When those concepts were going around, they were also circulating artwork with CST on Delta IV M+ and Falcon 9.I think CST was on 412 when the ULA/Boeing partnership was formalized, and the switch to 422 came not long afterwards.
Quote from: arachnitect on 10/19/2016 01:29 amI can't remember CST ever being "officially" on Atlas 401/402. When those concepts were going around, they were also circulating artwork with CST on Delta IV M+ and Falcon 9.I think CST was on 412 when the ULA/Boeing partnership was formalized, and the switch to 422 came not long afterwards.From the complete opposite perspective, perhaps that played a big part in the choice of the Atlas. If they went with the F9, they can't increase mass past a point. You can add an extra solid or even two to a 412 & get a 422 or 432.
The Atlas V rocket currently uses the Common Centaur variant.[10] In 2014, on the NROL-35 mission, Atlas V's Common Centaur first flew in a reengined configuration with an RL10-C-1 replacing its previous RL10-A-4-2. This engine is meant to be common between Centaur and the Delta Cryogenic Second Stage to reduce costs.[11][12] RL10-A-4-2 will continue to be used on some future flights. Atlas V launches using the Dual Engine Centaur configuration must use RL10-A-4-2 because the new engine is too wide to accommodate two side-by-side.[12] To date, all Atlas V launches have used the Single Engine Centaur variant, however CST-100 Starliner and Dream Chaser missions will require the dual engine variant, because it allows a "flatter" trajectory safer for aborts.As on Titan-Centaur, Atlas V 500 launches encapsulate the upper stage inside the payload fairing, to reduce aerodynamic loads. Atlas V 400 flights carry the fairing on top of Centaur, exposing it to the air.
The two engine Centaur first flew in 2014. All previous launches were the single engine variant.
Quote from: muomega0 on 10/19/2016 02:28 pmThe two engine Centaur first flew in 2014. All previous launches were the single engine variant.Incorrect. The majority of Centaurs were two engine flights, starting all the way back in the 60s. The single engine model first flew on Atlas III, in 2000 (?). If you are talking about Atlas V Centaurs, all have been single engine.
Quote from: muomega0 on 10/19/2016 02:28 pmThe two engine {Atlas V reengined} Centaur first flew in 2014. All previous {Atlas V }launches were the single engine variant.Quote from: centaurwikiThe Atlas V rocket currently uses the Common Centaur variant.[10] In 2014, on the NROL-35 mission, Atlas V's Common Centaur first flew in a reengined configuration with an RL10-C-1 replacing its previous RL10-A-4-2. This engine is meant to be common between Centaur and the Delta Cryogenic Second Stage to reduce costs.[11][12] RL10-A-4-2 will continue to be used on some future flights. Atlas V launches using the Dual Engine Centaur configuration must use RL10-A-4-2 because the new engine is too wide to accommodate two side-by-side.[12] To date, all Atlas V launches have used the Single Engine Centaur variant, however CST-100 Starliner and Dream Chaser missions will require the dual engine variant, because it allows a "flatter" trajectory safer for aborts.As on Titan-Centaur, Atlas V 500 launches encapsulate the upper stage inside the payload fairing, to reduce aerodynamic loads. Atlas V 400 flights carry the fairing on top of Centaur, exposing it to the air.NASA gets shuttle derived SLS and the to be retired Atlas....Wrong like most of your postsAtlas V has yet to fly dual engines. The Common Centaur variant is a single engine. All Atlas Centaurs, Atlas I's and Atlas II's had dual engines. The single engine Centaurs were introduced during Atlas III flights and all Atlas V's are single engine to this point.And NASA does not get Atlas
The two engine {Atlas V reengined} Centaur first flew in 2014. All previous {Atlas V }launches were the single engine variant.Quote from: centaurwikiThe Atlas V rocket currently uses the Common Centaur variant.[10] In 2014, on the NROL-35 mission, Atlas V's Common Centaur first flew in a reengined configuration with an RL10-C-1 replacing its previous RL10-A-4-2. This engine is meant to be common between Centaur and the Delta Cryogenic Second Stage to reduce costs.[11][12] RL10-A-4-2 will continue to be used on some future flights. Atlas V launches using the Dual Engine Centaur configuration must use RL10-A-4-2 because the new engine is too wide to accommodate two side-by-side.[12] To date, all Atlas V launches have used the Single Engine Centaur variant, however CST-100 Starliner and Dream Chaser missions will require the dual engine variant, because it allows a "flatter" trajectory safer for aborts.As on Titan-Centaur, Atlas V 500 launches encapsulate the upper stage inside the payload fairing, to reduce aerodynamic loads. Atlas V 400 flights carry the fairing on top of Centaur, exposing it to the air.NASA gets shuttle derived SLS and the to be retired Atlas....
Atlas V has yet to fly dual engines. Got it. That's not a good thing, right? When was the last time any dual engine Atlas flew?True..NASA does not *get* Atlas (nor Vulcan) mixing solids and crew....The reason is that it would require a substantial number of flights to test all the possible flight conditions and its not worth the effort given that LOC is so small during ascent *and* the LV will be retired. Simply redesign Vulcan v0 without solids and start on the path towards reuse, and only certify Vulcan, not Atlas. My guess is that ULA would jump at the chance.., no? Oh..I see now...Vulcan has to have solids so it 'looks like' Atlas. Bravo. BTW. Corrections always welcome....
Hardware! Structural test article for #Starliner #Atlas LV adapter
QuoteHardware! Structural test article for #Starliner #Atlas LV adapterhttps://twitter.com/torybruno/status/861615045729439744
Great hardware designed by @ulalaunch engineer Ed Walton and built by our excellent Decatur facility! CC: @barbegan13
I wonder why the Atlas V lifting the Starliner is called the 422 variant, since it doesn't use any payload fairing. Wouldn't be Atlas V 022 more appropriate in this case?
Quote from: starbase on 05/29/2017 01:31 pmI wonder why the Atlas V lifting the Starliner is called the 422 variant, since it doesn't use any payload fairing. Wouldn't be Atlas V 022 more appropriate in this case?5XX means fairing that encapsulates the whole centaur, 4XX means fairing on top centaur, exposing Centaur.In the Starliner configurtion, the Centaur is not inside a failring, so 4XX.