BE-4 engine updates & fixes #1652
Conversation
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couple quick notes. 550000 lbf is actually SL thrust later found min thrust is 30%. http://forum.nasaspaceflight.com/index.php?topic=10685.msg1665037#msg1665037 |
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Time to bug fix the bug fix i guess! |
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Isp looks unrealistically high, are you going off of RPA's theoretical perf rather than estimated performance? Also i don't think even BO know it's real performance yet, until they do tests. maybe we should leave the Isp at spacelaunchreport's estimates. The NSF forum link also says 5 degrees of gimbal, but that's on New Glenn, presumably Vulcan will have more as it's an Atlas successor and might take uneven SRB arrangements. I think everything else is ok. |
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I went by the facts that it is a Methalox engine and one of the "requirements" for Vulcan is to have at least, if not better, Isp figures than the RD-180. The VAC figure might stretch it a bit, is that one that you refer as unrealistic? BTW, i used the Altitude Peformance values (318.42 s ASL / 354.59 s VAC). It is also difficult to get good estimates for the throat and exhaust areas. A measurement error of just 1 px translates into almost 0.0795 m (~7.95 cm) and that is why i used an expansion area ratio of 25 (as quoted by many articles and posts). Dropping the freeze value of the area ratio at 1 instead of 3 gets a more meager 309 s ASL / 345 s VAC. |
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@PhineasFreak well i think they are both unrealistic, though VAC figure is more so i guess. using your file (with a ratio of 3) i get this http://i.imgur.com/E4Pkvvr.png, (305.46 Sl / 341.63 Vac) your RPA was probably giving theoretical(ideal) performance in the altitude tab rather than estimated performance for some reason. these numbers are only a little higher than spacelaunchreport's estimate, probably reasonable. |
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@SirKeplan yes, my bad. I found out that i was looking at the wrong info after all... So, freeze the values at 305/341? |
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@PhineasFreak Yes, that should be fine. |
* As per the new calculations.
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@SirKeplan apologies for "breaking" your current review with the new TF stuff...but i forgot to include them... 😟 |
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So, are we good here? |
Change Log:
Tweak the minimum and maximum thrust value to correspond to a rated VAC thrust of 550000 lbf.Notes: