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#760
by
nacnud
on 02 Jan, 2018 16:58
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Good sleuthing!
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#761
by
gongora
on 02 Jan, 2018 17:05
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There was some discussion about this in the Merlin 1D update thread a few days ago;
https://forum.nasaspaceflight.com/index.php?topic=41014.200
It 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.
On the SpaceX web site it shows thrust at sea level of 190k lbf and thrust in vacuum of 205k lbf.
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#762
by
CyndyC
on 02 Jan, 2018 17:09
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Good sleuthing!
No kidding! That certainly explains everything! Good to know & understand!
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#763
by
Formica
on 02 Jan, 2018 17:17
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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.
1033.1, the center core, is definitely based on Block 3 tech. 1023.2 and 1025.2 started life as Block 2, and may have been upgraded to Block 3 tech in the same way that 1021.2 was for its reflight. There was an intern from KSC who posted on Reddit about upgrading 1021.2 during its refurbishment, describing the process of replacing Block 1 parts with Block 3 parts. I'm still looking for a link to that post.
Here's a community based spreadsheet, with references, that keeps track of the blocks. It is as accurate as it can be without input from SpaceX, as far as I can tell.
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#764
by
gongora
on 02 Jan, 2018 17:31
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Good sleuthing!
It's really not. The 190k lbf is the sea level thrust of Block 5, not Block 3.
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#765
by
nacnud
on 02 Jan, 2018 17:51
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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!
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#766
by
gongora
on 02 Jan, 2018 17:54
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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!
The Block 5 values as shown on the SpaceX web site are 190k/sea level, 205k/vacuum. For the
same first stage engines.
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#767
by
nacnud
on 02 Jan, 2018 18:12
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I took a look at the
falcon 9 page but couldn't determine the model of F9 it was referring to, so I assumed it was the current one, not B5.
I could be wrong though.
I also noted that Vac M1D has a thrust of 210k lbs, when I thought it had 205k, so yeah I could be getting rather confused.
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#768
by
RocketLover0119
on 02 Jan, 2018 18:20
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Chris B on the ZUMA update thread says there is a potential 2nd SF coming up, if so, that would definitely push back the FH SF this week.....
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#769
by
UKobserver
on 02 Jan, 2018 19:04
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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!
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?
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#770
by
gongora
on 02 Jan, 2018 19:11
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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?
Yes
Why 92%?
I don't know
And 92% of what?
5.1M lbf
Is 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.
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?
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.)
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#771
by
envy887
on 02 Jan, 2018 19:24
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Why 92%?
I don't know
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
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#772
by
UKobserver
on 02 Jan, 2018 19:29
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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?
Yes
Why 92%?
I don't know
And 92% of what?
5.1M lbf
Is 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.
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?
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.)
Thanks, that's useful to know re earlier models/expansion ratio. I really doubt that 92% is a co-incidence though; I can't imagine anyone picking that exact number unless it matched up with something, like the difference between maximum thrust levels of the side and core boosters, or structural limits, or something else. I also think Elon would have explicitly stated that S/L thrust was 92% of that produced in a vacuum if he meant it that way. I could be completely wrong but I interpreted his statement as meaning that at some point in flight the thrust levels will be only 92% of either, a) what these engines are actually capable of producing, or b) what the B5 engines will be capable of producing, at that same point in flight. But who knows.
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#773
by
MP99
on 02 Jan, 2018 19:32
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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.
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
Sent from my GT-N5120 using Tapatalk
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#774
by
gongora
on 02 Jan, 2018 19:41
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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.
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
The initial flight is using pre-Block 5 cores because it was meant to fly before Block 5 was ready. Block 5 was never a requirement for FH. All following flights will be Block 5 because all of the cores they'll be building will be Block 5.
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#775
by
ChrisGebhardt
on 02 Jan, 2018 21:31
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That moment when you find a poll with your name on it and you've got the most votes and you go "What?"
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?
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#776
by
OnWithTheShow
on 03 Jan, 2018 00:02
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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?
Dixie Crossroads?
Im gonna try to make it down.
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#777
by
OneSpeed
on 03 Jan, 2018 00:31
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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
Yes, most of the Block 3 and 4 sims are at 91% thrust up to and after throttle down for max-Q. What this tells me is that my mass estimate for F9 is about 1% too low, so I will be updating that figure.
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#778
by
mdeep
on 03 Jan, 2018 01:56
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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?
Always meant to go to one of these. As long as it doesn't conflict with remotes, I'll definitely try to join in.
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#779
by
Flying Beaver
on 03 Jan, 2018 02:18
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...who all wants to meet up for dinner/drinks the night before the first launch?
Well I look forward to joining everyone for every evening for a week or 2 week (plus) in that case
.
(Kinda) Just joking, i'm sure they'll fly on the first or second attempt if the static fire goes well.
Was able to eye up the OG-2 F2 launch date well enough (one day off but punted 24hrs, in line with Elon
) that i'd be confident getting plane tickets after a static fire confirmation, in line with the best estimates of launch date at that point,
plus a 5/6 day buffer.
.
) that i'd be confident getting plane tickets after a static fire confirmation, in line with the best estimates of launch date at that point, plus a 5/6 day buffer.