There was some discussion about this in the Merlin 1D update thread a few days ago;https://forum.nasaspaceflight.com/index.php?topic=41014.200It was prompted by the following Instagram post from a SpaceX employee, showing off a new Block 5 booster engine, which he claimed was rated at 205,000lbf.https://www.instagram.com/p/Bc8pqAng9rH/While there have been suggestions that these new engines may have actually been tested on the stand at thrust levels as high as 245,000lbf, presumably to establish safety margins, it looks like they will be introducing a new flight rating of 205,000lbf when these engines debut on the new block 5 booster.
Good sleuthing!
This first FH is a composite of B3 side boosters and a B4 core, whose Merlin 1Ds I believe run at 190,000lbf thrust. AncientU pointed out that 27 x 190,000lbf is 5.1Mlbf, which matches the thrust that Elon said FH would have at liftfoff.
Well the current booster engine has 190k lbf, the instagrammed booster engine has 205k lbf. One is 92% of the other. I don't think we ever got to the bottom of the instagrammed engine, but Elons 92% tweet makes me think that it really had been uprated to 205k. Which I was doubting as there could have been some confusion between booster and vacuum engines.The only info we have is from keeping a close watch on the public internet and waiting for more into from Spacex/Elon. But in reference to FH it's reasonable to think that this launch will have 190k lbf Merlin D engines while then next block 5 FH will have 205k lbf Merlin D engines. We'll have to keep trawling social media for clues!
Quote from: nacnud on 01/02/2018 05:51 pmWell the current booster engine has 190k lbf, the instagrammed booster engine has 205k lbf. One is 92% of the other. I don't think we ever got to the bottom of the instagrammed engine, but Elons 92% tweet makes me think that it really had been uprated to 205k. Which I was doubting as there could have been some confusion between booster and vacuum engines.The only info we have is from keeping a close watch on the public internet and waiting for more into from Spacex/Elon. But in reference to FH it's reasonable to think that this launch will have 190k lbf Merlin D engines while then next block 5 FH will have 205k lbf Merlin D engines. We'll have to keep trawling social media for clues! The Block 5 values as shown on the SpaceX web site are 190k/sea level, 205k/vacuum. For the same first stage engines.
I'm not disagreeing, as it's completely plausible that the SpaceX website is showing B5 stats and that the employee was referring to thrust level in a vacuum, but are you suggesting that it's just a massive co-incidence that they are running at 92% this time?
Why 92%?
And 92% of what?
Is S/L thrust also 92% of vacuum thrust for previous versions of the M1D, such as on the B2 and B3 boosters?
Is that due to the expansion ratio of the nozzle? If so, does Elon mean that they are going to gradually throttle down each engine as this FH climbs so as to keep the maximum thrust from each engine at S/L thrust levels all the way through the flight, perhaps for structural reasons?
QuoteWhy 92%?I don't know
Quote from: UKobserver on 01/02/2018 07:04 pmI'm not disagreeing, as it's completely plausible that the SpaceX website is showing B5 stats and that the employee was referring to thrust level in a vacuum, but are you suggesting that it's just a massive co-incidence that they are running at 92% this time?YesQuoteWhy 92%?I don't knowQuoteAnd 92% of what?5.1M lbfQuoteIs S/L thrust also 92% of vacuum thrust for previous versions of the M1D, such as on the B2 and B3 boosters?The previous value I see from their site is 170k lbf @ SL/185k lbf @ vacuum, so yes.QuoteIs that due to the expansion ratio of the nozzle? If so, does Elon mean that they are going to gradually throttle down each engine as this FH climbs so as to keep the maximum thrust from each engine at S/L thrust levels all the way through the flight, perhaps for structural reasons?I'm assuming Elon was talking about thrust at lift-off, period. Engines throttle to various settings during flight as needed (around Max-Q, limiting acceleration as the vehicle gets lighter, etc.)
It's safe to say that this will be only Falcon Heavy ever to use pre-Block 5 cores. After re-scoping Falcon Heavy to chase F9 iterations to v1.1 and then to FT specifications, now there's Block 5 coming. SpaceX needed to make the decision whether to bring the FH demo vehicle up to Block 5 spec with bolted octowebs etc. and accept further delays to a program already repeatedly delayed by F9 iteration churn -- or to simply launch the damn thing already even though it will end up being a one-off. This will forever be the unique "albino" FH demo vehicle.
Quote from: butters on 01/02/2018 12:22 amIt's safe to say that this will be only Falcon Heavy ever to use pre-Block 5 cores. After re-scoping Falcon Heavy to chase F9 iterations to v1.1 and then to FT specifications, now there's Block 5 coming. SpaceX needed to make the decision whether to bring the FH demo vehicle up to Block 5 spec with bolted octowebs etc. and accept further delays to a program already repeatedly delayed by F9 iteration churn -- or to simply launch the damn thing already even though it will end up being a one-off. This will forever be the unique "albino" FH demo vehicle.I believe that the initial flight is using pre-block-5 cores because there is some question whether it will reach orbit.I believe all following flights will be block 5 because they expect to learn enough from flight #1 that subsequent flights have a much better chance of succeeding.Cheers, Martin
maybe I can dust off the old Shuttle dinner gatherings I used to organize and we can see who all wants to meet up for dinner/drinks the night before the first launch?
92% of what the website lists is about what all the 2017 flights have been running at - see the sims thread. I'm guessing it's what Block 3 and 4 cores are rated for, since SpaceX used to list Merlin at 170 klbf at liftoff (89.5% of 190 klbf). This would seem to apply to all early blocks of FT/v1.2, with only Block 5 getting a thrust upgrade.https://web.archive.org/web/20160101081059/http://www.spacex.com/falcon9
But yes, I'll happily take charge of organizing something surrounding Falcon Heavy. I'll be at KSC press site for the launch, but as we'll likely have A LOT of people coming for this, maybe I can dust off the old Shuttle dinner gatherings I used to organize and we can see who all wants to meet up for dinner/drinks the night before the first launch?
...who all wants to meet up for dinner/drinks the night before the first launch?