Ultimate Steve Posted March 25 Share Posted March 25 21 minutes ago, tater said: They've fired them before Hmm, looks like they did. Memory is a weird thing. Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted March 25 Share Posted March 25 13 minutes ago, Ultimate Steve said: Hmm, looks like they did. Memory is a weird thing. The RVacs are designed to have flow separation just barely starting around the very edge of the nozzle at sea level. The nozzle is reinforced at the edge which helps keeps this from causing issues. Part of this was to save weight, part of this was to make them easier to static fire at sea level. Quote Link to comment Share on other sites More sharing options...
tater Posted March 25 Share Posted March 25 Quote Link to comment Share on other sites More sharing options...
Pthigrivi Posted March 26 Share Posted March 26 Id love to hear more on thruster and maneuverability updates as that seemed the the central hurdle on IFT3. Still sticking with gas thrusters or augmenting with a separate system? Quote Link to comment Share on other sites More sharing options...
Exoscientist Posted March 26 Share Posted March 26 On 3/13/2024 at 5:58 AM, mikegarrison said: He's the CEO (and has about 80% control of the voting shares). He can call himself the "head engineer" if he wants -- nobody who works for him is going to tell him otherwise. But the higher you go in management, the less actual engineering you do, despite sometimes being the person who ultimately says yes or no about major decisions. FWIW, he has an economics degree, not an engineering degree. Not that I'm saying having a degree is necessary, but it is somewhat indicative. If you look at his history, it's not at all clear he has ever worked as an engineer. Shotwell, on the other hand, does have an engineering degree and clearly has worked as an engineer in her professional background. Elon has said when they were trying to hire a chief engineer they couldn’t get anyone good willing to come so he made himself the chief engineer. I would argue they still don’t have anyone good at that position. Sorry, Elon! Quote Link to comment Share on other sites More sharing options...
darthgently Posted March 26 Share Posted March 26 Some avatar images on this site are incredibly fitting Quote Link to comment Share on other sites More sharing options...
Exoscientist Posted March 26 Share Posted March 26 (edited) 7 hours ago, tater said: Sorry, but a 10 second burn is not “full-duration”. THIS is full-duration: Another irritation of mine is that SpaceX won’t tell you what power level their tests are operating at. 50%, 75%, 100%? Usually, the launch company tells you that in their tests to confirm to potential customers their engines can operate at the needed power levels to complete their missions. Bob Clark Edited March 26 by Exoscientist Typo Quote Link to comment Share on other sites More sharing options...
tater Posted March 26 Share Posted March 26 (edited) 20 minutes ago, Exoscientist said: Sorry, but a 10 second burn is not “full-duration”. THIS is full-duration: Yes it is. They do static fires all the time. Literally more than anyone on Earth. Also, they cannot test the ship at sea level for 1200 tons of props and get data that mirrors flight. Just fly it. 20 minutes ago, Exoscientist said: Another irritation of mine is that SpaceX won’t tell you what power level their tests are operating at. 50%, 75%, 100%? Usually, the launch company tells you that in their tests to confirm to potential customers their engines can operate at the needed power levels to complete their missions. One, this is nonsense. What's the data on RL-10? You can't even tell me what they cost (and we pay for them all the time with tax dollars). Two, they are not selling engines, and have no responsibility to tell you anything at all. Just as we have no clue about Be-4 specs, or Be-7. As for RS-25 testing, for what WE pay for them, they should send all of us a framed picture of every test. Maybe all the stupid Stennis testing is why they cost 100 MILLION dollars each? I'd rather they test less, and SLS costed $100M all up to fly—I would not care how many SLS NASA blew up if we'd get 40 launches for the cost of 1 (or even 20). Edited March 26 by tater Quote Link to comment Share on other sites More sharing options...
Cuky Posted March 26 Share Posted March 26 (edited) 4 hours ago, Exoscientist said: Sorry, but a 10 second burn is not “full-duration”. THIS is full-duration: If test parameters are "Start all 6 engines, keep them on for 10s and then shut down and have no problems during all of that" and they burn for those 10s that means that full duration of the test was performed. How is that so hard to grasp for so many static fires and pages of this thread is beyond me really. All engines are tested before they get to be mounted on SH or SS and what those static burns are are basically checks to see that all the plumbing, wiring etc. was done correctly. Same as F9, they raise it vertical on launch pad, test fire for few seconds to see that everything is in spec and prepare for launch. Edited March 26 by Cuky Quote Link to comment Share on other sites More sharing options...
darthgently Posted March 26 Share Posted March 26 6 hours ago, Exoscientist said: Another irritation of mine is that SpaceX won’t tell you what power level their tests are operating at. Perhaps you'd like SpaceX to also tell you the power levels that everyone else is testing their engines at while they are at it. I mean if you are going to hold them to a higher bar, might as well turn that bar up to 11, am I right? Quote Link to comment Share on other sites More sharing options...
magnemoe Posted March 26 Share Posted March 26 2 hours ago, Cuky said: If test parameters are "Start all 6 engines, keep them on for 10s and then shut down and have no problems during all of that" and they burn for those 10s that means that full duration of the test was performed. How is that so hard to grasp for so many static fires and pages of this thread is beyond me really. All engines are tested before they get to be mounted on SH or SS and what those static burns are are basically checks to see that all the plumbing, wiring etc. was done correctly. Same as F9, they raise it vertical on launch pad, test fire for few seconds to see that everything is in spec and prepare for launch. This, they do real full duration burns then engine is not connected to rocket but on test stands like image above. Launch pad is not designed for full duration of an large rocket. Usually the full duration burns are done horizontally to avoid heating the ground. Quote Link to comment Share on other sites More sharing options...
Exoscientist Posted March 26 Share Posted March 26 (edited) 10 hours ago, Cuky said: If test parameters are "Start all 6 engines, keep them on for 10s and then shut down and have no problems during all of that" and they burn for those 10s that means that full duration of the test was performed. How is that so hard to grasp for so many static fires and pages of this thread is beyond me really. … The problem is that is not standard usage in the industry. Commonly, you run an engine in static tests at full thrust and full fight duration to give confidence it can perform as expected during actual flights. This is also done as confirmation to potential customers that the rocket will actually deliver as expected. Blue Origin could if they wanted call their little suborbital hops with New Shepard as “flights to orbit”, but that doesn’t mean the rest of the industry would agree with that terminology. Bob Clark Edited March 26 by Exoscientist Typo Quote Link to comment Share on other sites More sharing options...
tater Posted March 26 Share Posted March 26 (edited) 6 hours ago, Exoscientist said: The problem is that is not standard usage in the industry. Commonly, you run an engine in static tests at full thrust and full fight duration to give confidence it can perform as expected during actual flights. This is also done as confirmation to potential customers that the rocket will actual deliver as expected. Blue Origin could if they wanted call their little suborbital hops with New Shepard as “flights to orbit”, but that doesn’t mean the rest of the industry would agree with that terminology. "The industry" launches how many rockets per week right now, I forget? When "the industry" does anything worth paying attention to, let me know, though I imagine I will have long since taken a dirt nap by the time that happens. Static fires for SpaceX go as long as they need to get stable combustion after start up transients. That's all they need. When it comes to knowledge about how rocket engines behave during use, I'd wager at this point no one on the planet has a better understanding than they do. They've flown I think 322 times times 10 engines, plus another 72 engines (?) for FH side boosters. A few hundred have had 4 relights (not counting S 2). All were static fired as engines first, then on the completed stage. Many static fired on the pad. Thousands of fires. 10,000? More? Every Raptor tested before flight, then static fires on the pads as well. They do a static fire—then swap an engine... because they have the data they need to make that decision. 8 hours ago, magnemoe said: This, they do real full duration burns then engine is not connected to rocket but on test stands like image above. Launch pad is not designed for full duration of an large rocket. Usually the full duration burns are done horizontally to avoid heating the ground. Or with a stand like Stennis with huge water deluge... of course they have to be concerned about wastewater from firing the pad deluge for a few seconds, but somehow they're supposed to use MORE water, and for 2.5 to 8 minutes and that's no problem? It also means the vehicle is at risk of a RUD on the ground—all while testing nothing really pertinent to flight regimes (sloshing, etc). Edited March 26 by tater Quote Link to comment Share on other sites More sharing options...
zolotiyeruki Posted March 26 Share Posted March 26 (edited) 29 minutes ago, Exoscientist said: The problem is that is not standard usage in the industry. Commonly, you run an engine in static tests at full thrust and full fight duration to give confidence it can perform as expected during actual flights. This is also done as confirmation to potential customers that the rocket will actual deliver as expected. C'mon, man. The whole "SpaceX isn't doing what's standard" concern has already been VERY thoroughly discussed and invalidated in this thread. Many of the constraints of 60 years ago that resulted in "standard practices" no longer exist, and it would be foolish for SpaceX to slavishly follow them. We can see the results of such uncritical thinking in the performance of the SLS program: decades late, billions over budget, and still not 100% working, even though they started with their engines and boosters already designed. Why on earth would SpaceX want to follow such a path? "Standard practice" has morphed from a solution into the problem. I'm reminded of a quote: "Contradictions do not exist. Whenever you think that you are facing a contradiction, check your premises. You will find that one of them is wrong." You have as a premise that "standard practice" is the only (or at the very least overwhelmingly most likely) way to achieve success in the space launch industry. SpaceX is not following standard practice, yet they are wildly successful, while their rivals, who are following standard practice and have decades more experience, are achieving mild success or are floundering. This appears to be a contradiction, and should prompt a reexamination of your premises. In any case, I have a more sincere question: Starship's SL raptors are there to provide sufficient TWR after MECO stage separation, and for landing. At what point during the second-stage burn would the vacuum raptors provide enough TWR that the SL raptors could be shut down? How much efficiency could be gained by doing so? Edited March 26 by zolotiyeruki Quote Link to comment Share on other sites More sharing options...
darthgently Posted March 26 Share Posted March 26 (edited) 1 hour ago, magnemoe said: This, they do real full duration burns then engine is not connected to rocket but on test stands like image above. Launch pad is not designed for full duration of an large rocket. Usually the full duration burns are done horizontally to avoid heating the ground. Deja Vu! This exact issue posed by exo has been addressed exhaustively and authoritatively over the last few months. It's like we are in a Moebius time loop! Edited March 26 by darthgently Quote Link to comment Share on other sites More sharing options...
Exoscientist Posted March 26 Share Posted March 26 5 hours ago, darthgently said: Deja Vu! This exact issue posed by exo has been addressed exhaustively and authoritatively over the last few months. It's like we are in a Moebius time loop! SpaceX repeating the same mistakes over and over again does not make those mistakes correct. Bob Clark Quote Link to comment Share on other sites More sharing options...
Piscator Posted March 26 Share Posted March 26 Repeating that something is a mistake over and over again doesn't make it a mistake though. Quote Link to comment Share on other sites More sharing options...
tater Posted March 26 Share Posted March 26 36 minutes ago, Exoscientist said: SpaceX repeating the same mistakes over and over again does not make those mistakes correct. What mistakes? When was the last 100% reusable (actually reusable, unlike Shuttle) rocket tested by anyone? ... Yeah, NEVER. What company in the US right now has more experience building, flying, and reusing any part of any rocket? Yeah, none. 322 F9/FH flights is 322 upper stages built/flown—so even Centaur, the only possible thing that might have flown as much in the US, and in existence for 62 YEARS? How many times has Centaur flown? 271 times as of Vulcan Cert). So again, "the industry" right now in terms of experience is: SpaceX and "also ran." So you claiming it's a mistake how they are prodceeding... yeah, that's irritating, tbh. How about we just stipulate that you think everything they are doing is wrong, and skip the posts? When HLS lands on the Moon, we can all simply assume that according to you it's wrong, or tested the wrong way, whatever. When they land on Mars? Same thing, making the same mistakes all over again, this time on Mars! Pikers! Quote Link to comment Share on other sites More sharing options...
Ultimate Steve Posted March 26 Share Posted March 26 Grammatically, full duration can be both in reference to the test duration and the mission duration. It can mean both things. Maybe there should be different terms for the two, I don't know. Simply saying full duration is shorter, and we have seen that saying in 2 places. Twitter/X and in mission control speak, both of which are places where brevity counts. I think Exoscientist might be concerned about SpaceX deliberately and maliciously using this ambiguity to mislead. Maybe a dumb investor would fall for that, but nobody in the know would see "full duration" next to a video 20 seconds long and think "gee, I should buy a mission from them because they are firing the upper stage for a full 8 minutes/their upper stage is so powerful, it can enter orbit in 20 seconds!" Now if they were specifically claiming full mission duration, that would be cause for alarm. Quote Link to comment Share on other sites More sharing options...
tater Posted March 26 Share Posted March 26 (edited) 19 minutes ago, Ultimate Steve said: I think Exoscientist might be concerned about SpaceX deliberately and maliciously using this ambiguity to mislead. Maybe a dumb investor would fall for that, but nobody in the know would see "full duration" next to a video 20 seconds long and think "gee, I should buy a mission from them because they are firing the upper stage for a full 8 minutes/their upper stage is so powerful, it can enter orbit in 20 seconds!" It's not a public company. The people who invest know what they are getting into—remember Isaacman tried to invest directly, with deep pockets, and was turned down, hence Polaris. The caliber if investors is such that they get a sit down, it's not randos on the interwebs. Edited March 26 by tater Quote Link to comment Share on other sites More sharing options...
kspbutitscursed Posted March 26 Share Posted March 26 45 minutes ago, Ultimate Steve said: Grammatically, full duration can be both in reference to the test duration and the mission duration. It can mean both things. Maybe there should be different terms for the two, I don't know. Simply saying full duration is shorter, and we have seen that saying in 2 places. Twitter/X and in mission control speak, both of which are places where brevity counts. I think Exoscientist might be concerned about SpaceX deliberately and maliciously using this ambiguity to mislead. Maybe a dumb investor would fall for that, but nobody in the know would see "full duration" next to a video 20 seconds long and think "gee, I should buy a mission from them because they are firing the upper stage for a full 8 minutes/their upper stage is so powerful, it can enter orbit in 20 seconds!" Now if they were specifically claiming full mission duration, that would be cause for alarm. Maybe they could do full flight duration at the Masseys new Static fire stand that is under construction? Quote Link to comment Share on other sites More sharing options...
darthgently Posted March 27 Share Posted March 27 30 minutes ago, kspbutitscursed said: Maybe they could do full flight duration at the Masseys new Static fire stand that is under construction? I have no way to know if every Raptor gets a full duration test in a stand, but they do routinely do full duration tests on Raptors. But individually, on a stand, and not currently at Boca Chica, but at McGregor (I think). Though the new test stand and deluge at at Masseys is probably what you mean and I'd guess you could be on to something there. Quote Link to comment Share on other sites More sharing options...
tater Posted March 27 Share Posted March 27 36 minutes ago, kspbutitscursed said: Maybe they could do full flight duration at the Masseys new Static fire stand that is under construction? Possibly, not sure what they gain. It risks a pad RUD, and out of 3 test flights, two had the ship perform nominally for the engines‚ the issue being related to flight environment for the IFT-2 failure apparently. So maybe they learn something, maybe not. Might be mostly to double test possibility on closure days with 2 sites far apart (and limited road closures). Quote Link to comment Share on other sites More sharing options...
kspbutitscursed Posted March 27 Share Posted March 27 4 minutes ago, darthgently said: I have no way to know if every Raptor gets a full duration test in a stand, but they do routinely do full duration tests on Raptors. But individually, on a stand, and not currently at Boca Chica, but at McGregor (I think). Though the new test stand and deluge at at Masseys is probably what you mean and I'd guess you could be on to something there. the new stand at Masseys not at the launch site 2 minutes ago, tater said: Possibly, not sure what they gain. It risks a pad RUD, and out of 3 test flights, two had the ship perform nominally for the engines‚ the issue being related to flight environment for the IFT-2 failure apparently. So maybe they learn something, maybe not. Might be mostly to double test possibility on closure days with 2 sites far apart (and limited road closures). test the recovered ships and still see if they perform norminal after being recovered? Quote Link to comment Share on other sites More sharing options...
darthgently Posted March 27 Share Posted March 27 1 minute ago, kspbutitscursed said: the new stand at Masseys not at the launch site Got that Quote Link to comment Share on other sites More sharing options...
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