Here's the webcast paired with some great animations. I really like the charts showing the altitude and velocity of both stages for the duration. I didn't realize it took soooo long for the first stage to get back down to the altitude it had at MECO. https://youtube.com/watch?v=CGL2FEMxDE0
Quote from: mnelson on 02/04/2017 01:08 amHere's the webcast paired with some great animations. I really like the charts showing the altitude and velocity of both stages for the duration. I didn't realize it took soooo long for the first stage to get back down to the altitude it had at MECO. https://youtube.com/watch?v=CGL2FEMxDE0That's really interesting, especially to see the velocity changes (e.g. how much each burn slows down S1).Note how S1 resumes accelerating after the entry burn completes, but only for a few seconds and then starts decelerating again, WITHOUT engines burning, due to descending into thicker atmosphere. It's slowing down during nearly the entire atmospheric descent because it's going faster than terminal velocity.This needs to get paired with the graph (video?) that someone here produced that inferred the ACCELERATION data from the velocity data shown on the webcast screen. Although, as I recall, only S2 data was shown. SpaceX, are you listening? Give us S1 data (from telemetry) on the screen as well, and the community will produce cool graphics for you ...
My interpretation is that it is at terminal velocity very quickly, but that the terminal velocity is of course decreasing with density.It's not the same thing as being above terminal velocity. It means they are always at equilibrium, and there's no residual of the speed they've been traveling at 2 seconds ago.
Quote from: meekGee on 02/04/2017 02:57 pmMy interpretation is that it is at terminal velocity very quickly, but that the terminal velocity is of course decreasing with density.It's not the same thing as being above terminal velocity. It means they are always at equilibrium, and there's no residual of the speed they've been traveling at 2 seconds ago.If you watch this sim of the Iridium launch, you can see that the g forces peak at 4.6 at the 7:20 mark, purely due to aerodynamic forces. The rocket is travelling at 686 m/s, or about Mach 2, way in excess of terminal velocity. If it was in 'equilibrium' the g forces would be close to 1.
Quote from: OneSpeed on 02/09/2017 10:49 amQuote from: meekGee on 02/04/2017 02:57 pmMy interpretation is that it is at terminal velocity very quickly, but that the terminal velocity is of course decreasing with density.It's not the same thing as being above terminal velocity. It means they are always at equilibrium, and there's no residual of the speed they've been traveling at 2 seconds ago.If you watch this sim of the Iridium launch, you can see that the g forces peak at 4.6 at the 7:20 mark, purely due to aerodynamic forces. The rocket is travelling at 686 m/s, or about Mach 2, way in excess of terminal velocity. If it was in 'equilibrium' the g forces would be close to 1.That's the sim.If you look at this video of the real thing, you see a smooth drop in velocity from the end of the last burn, almost along a straight line(Skip forward to approx second 460, similar to your 7:20 mark)https://www.youtube.com/watch?v=NT50R2dLht8?t=459
Quote from: meekGee on 02/11/2017 05:23 amQuote from: OneSpeed on 02/09/2017 10:49 amQuote from: meekGee on 02/04/2017 02:57 pmMy interpretation is that it is at terminal velocity very quickly, but that the terminal velocity is of course decreasing with density.It's not the same thing as being above terminal velocity. It means they are always at equilibrium, and there's no residual of the speed they've been traveling at 2 seconds ago.If you watch this sim of the Iridium launch, you can see that the g forces peak at 4.6 at the 7:20 mark, purely due to aerodynamic forces. The rocket is travelling at 686 m/s, or about Mach 2, way in excess of terminal velocity. If it was in 'equilibrium' the g forces would be close to 1.That's the sim.If you look at this video of the real thing, you see a smooth drop in velocity from the end of the last burn, almost along a straight line(Skip forward to approx second 460, similar to your 7:20 mark)https://www.youtube.com/watch?v=NT50R2dLht8?t=459I'm pretty sure those first stage numbers where generated by the FightClub.io "trajectory visualizer." Space X did not provide them on the webcast. I think this is a matter of competing simulations and I'm suspicious of FightClub's smooth deceleration.
I'm pretty sure those first stage numbers where generated by the FightClub.io "trajectory visualizer." Space X did not provide them on the webcast. I think this is a matter of competing simulations and I'm suspicious of FightClub's smooth deceleration.
Well FC is a simulator, but he managed to get the timing of all events to within a few seconds, and then tweaked the sim parameters to match reality. I think that's pretty good.I'm using it to estimate trends, not nail down precise numbers.
Quote from: mme on 02/11/2017 05:53 amI'm pretty sure those first stage numbers where generated by the FightClub.io "trajectory visualizer." Space X did not provide them on the webcast. I think this is a matter of competing simulations and I'm suspicious of FightClub's smooth deceleration.Quote from: meekGee on 02/11/2017 06:21 amWell FC is a simulator, but he managed to get the timing of all events to within a few seconds, and then tweaked the sim parameters to match reality. I think that's pretty good.I'm using it to estimate trends, not nail down precise numbers.Flight Club is a launch and landing trajectory visualiser, not a simulator. It is replaying the velocity and altitude data gleaned from the SpaceX broadcasts, where it is available. Where it is not, they appear to be interpolating as best they can to match the video they have.SpaceSim is an n-body simulation of the solar system. The simulation takes account of all of the forces acting on the rocket, including mass, thrust, drag (including skin friction) and lift. The process of matching the broadcast data to the flight profile is extremely manual and time consuming. But when they do match, it is quite revealing. For example we know that for return to flight, the first stage must have been throttled to between 90 and 95% of the FT spec.
I thought so too initially, but he appears to be visualizing his simulation, based on some of the comments he's left in the conversation threads.However - if he has a robust simulation, and he tweaks the underlying parameters to match reality, then that's even better than just blindly reading numbers from the SpaceX feed.You can look at his results for different missions and see how well it works.
Quote from: meekGee on 02/11/2017 06:35 amI thought so too initially, but he appears to be visualizing his simulation, based on some of the comments he's left in the conversation threads.However - if he has a robust simulation, and he tweaks the underlying parameters to match reality, then that's even better than just blindly reading numbers from the SpaceX feed.You can look at his results for different missions and see how well it works.Fair enough, so I've added a couple of lines of code to SpaceSim to output Velocity, Acceleration and Altitude of just the second stage to a .csv file. The output is attached below, and is similar in many respects to the Flight Club S2 profile. One observation I would make is that the drag should drop quite suddenly as the stage goes subsonic, but only SpaceSim appears to be taking account of this.Quote from: meekGee on 02/04/2017 02:57 pmMy interpretation is that it is at terminal velocity very quickly, but that the terminal velocity is of course decreasing with density.It's not the same thing as being above terminal velocity. It means they are always at equilibrium, and there's no residual of the speed they've been traveling at 2 seconds ago.Going back to your original point though, both profiles, however they are obtained, confirm that the g forces are only in 'equilibrium' very briefly, at around the 7:03 mark, and that the stage is well above terminal velocity at the 7:20 mark.
How do you define aerodynamic equilibrium? And should that only be relevant only between the entry burn and the landing burn starts?
I'm not following. Shouldn't the acceleration be the derivative of the velocity? (Are you always doing dS - along the path?)Altitude of course is unrelated, but why is the acceleration at 0 over so much of the time?
Quote from: meekGee on 02/12/2017 05:08 amI'm not following. Shouldn't the acceleration be the derivative of the velocity? (Are you always doing dS - along the path?)Altitude of course is unrelated, but why is the acceleration at 0 over so much of the time?Drag between the initial boost and the boostback burns is nearly zero because of the altitude, and so therefore is the acceleration. Acceleration between the boostback and entry burns is also near zero for the same reason. However acceleration in the initial boost phase also appears to be zero in the plot I've posted. This is clearly not correct.
Quote from: OneSpeed on 02/12/2017 09:06 amQuote from: meekGee on 02/12/2017 05:08 amI'm not following. Shouldn't the acceleration be the derivative of the velocity? (Are you always doing dS - along the path?)Altitude of course is unrelated, but why is the acceleration at 0 over so much of the time?Drag between the initial boost and the boostback burns is nearly zero because of the altitude, and so therefore is the acceleration. Acceleration between the boostback and entry burns is also near zero for the same reason. However acceleration in the initial boost phase also appears to be zero in the plot I've posted. This is clearly not correct.I think he meant that acceleration due to gravity is missing.
Quote from: MikeAtkinson on 02/12/2017 12:13 pmI think he meant that acceleration due to gravity is missing.Well it's hard to separate out once you're in air, since the direction of motion is not known.
I think he meant that acceleration due to gravity is missing.
Quote from: meekGee on 02/12/2017 03:28 pmQuote from: MikeAtkinson on 02/12/2017 12:13 pmI think he meant that acceleration due to gravity is missing.Well it's hard to separate out once you're in air, since the direction of motion is not known.Yes, the internal term in SpaceSim is RelativeAcceleration, acceleration relative to gravity, which is calculated later. Gravity is not considered a constant because it is a n-body simulation of the solar system.
Quote from: OneSpeed on 02/12/2017 07:32 pmQuote from: meekGee on 02/12/2017 03:28 pmQuote from: MikeAtkinson on 02/12/2017 12:13 pmI think he meant that acceleration due to gravity is missing.Well it's hard to separate out once you're in air, since the direction of motion is not known.Yes, the internal term in SpaceSim is RelativeAcceleration, acceleration relative to gravity, which is calculated later. Gravity is not considered a constant because it is a n-body simulation of the solar system.I understand that - but where is it coming from?The velocity is along the path (I assume) so if you differentiate that, you get the full acceleration. (in vector form)You can subtract 1 g in the "Z" direction, but this only makes sense when in free fall. (Is that what you did?)Once you hit the atmosphere, the aerodynamic forces can be in any direction. So you can't define "equilibrium" as just "0 g".It's trickier to tease this out than it appears at first blush.
Quote from: meekGee on 02/12/2017 09:06 pmQuote from: OneSpeed on 02/12/2017 07:32 pmQuote from: meekGee on 02/12/2017 03:28 pmQuote from: MikeAtkinson on 02/12/2017 12:13 pmI think he meant that acceleration due to gravity is missing.Well it's hard to separate out once you're in air, since the direction of motion is not known.Yes, the internal term in SpaceSim is RelativeAcceleration, acceleration relative to gravity, which is calculated later. Gravity is not considered a constant because it is a n-body simulation of the solar system.I understand that - but where is it coming from?The velocity is along the path (I assume) so if you differentiate that, you get the full acceleration. (in vector form)You can subtract 1 g in the "Z" direction, but this only makes sense when in free fall. (Is that what you did?)Once you hit the atmosphere, the aerodynamic forces can be in any direction. So you can't define "equilibrium" as just "0 g".It's trickier to tease this out than it appears at first blush.Sorry, I'm being hand wavy and should let OneSpeed explain since he really knows what he is talking about and I'm just expressing my understanding of what the graphs represent.The acceleration that is being graphed (after the initial boost and separation [1]) is in the stage's reference frame, not Earth's. There is no subtraction of the 1 g going on. The "RelativeAcceleration" is relative to free-fall in the n-body space.It's probably not right, but in my mind it is summing all the forces on the stage (gravity, thrust, drag) and expressing the resulting "g-force" that is being experienced by the stage. It is not expressing dV/dT relative to an observer on Earth. It is dV/dT relative to the stage in free-fall and what "free-fall" means is calculated in realtime (so it's not a fixed 9.8 m/s^2).[1] Before first stage separation, the calculation is done for the payload because that's how the software models the problem and since everything is connected at that point it's a reasonable simplification.
It's trickier to tease this out than it appears at first blush.
The acceleration that is being graphed (after the initial boost and separation [1]) is in the stage's reference frame, not Earth's. There is no subtraction of the 1 g going on. The "RelativeAcceleration" is relative to free-fall in the n-body space.I'm probably not right, but in my mind it is summing all the forces on the stage (gravity, thrust, drag) and expressing the resulting "g-force" that is being experienced by the stage. It is not expressing dV/dT relative to an observer on Earth. It is dV/dT relative to the stage in free-fall and what "free-fall" means is calculated in realtime (so it's not a fixed 9.8 m/s^2).[1] Before first stage separation, the calculation is done for the payload because that's how the software models the problem and since everything is connected at that point it's a reasonable simplification.
Hey folks, I'm late to the party. I'm the guy who made Flight ClubQuote from: OneSpeed on 02/11/2017 06:29 amQuote from: mme on 02/11/2017 05:53 amI'm pretty sure those first stage numbers where generated by the FightClub.io "trajectory visualizer." Space X did not provide them on the webcast. I think this is a matter of competing simulations and I'm suspicious of FightClub's smooth deceleration.Quote from: meekGee on 02/11/2017 06:21 amWell FC is a simulator, but he managed to get the timing of all events to within a few seconds, and then tweaked the sim parameters to match reality. I think that's pretty good.I'm using it to estimate trends, not nail down precise numbers.Flight Club is a launch and landing trajectory visualiser, not a simulator. It is replaying the velocity and altitude data gleaned from the SpaceX broadcasts, where it is available. Where it is not, they appear to be interpolating as best they can to match the video they have.SpaceSim is an n-body simulation of the solar system. The simulation takes account of all of the forces acting on the rocket, including mass, thrust, drag (including skin friction) and lift. The process of matching the broadcast data to the flight profile is extremely manual and time consuming. But when they do match, it is quite revealing. For example we know that for return to flight, the first stage must have been throttled to between 90 and 95% of the FT spec.Flight Club is a simulator. Myself and zlynn1990 (of SpaceSim fame) collaborated a bunch on tweaking our atmospheric models and such when we were independently building our simulators. Just wanted to clear that up. Let me know if you have any questions about how Flight Club does things - happy to help in any way.
... I was also starting to feel like maybe we should create a simulation thread for these topics if people wanted to continue debating the implications of different simulations.
Flight Club is a simulator. Myself and zlynn1990 (of SpaceSim fame) collaborated a bunch on tweaking our atmospheric models and such when we were independently building our simulators. Just wanted to clear that up. Let me know if you have any questions about how Flight Club does things - happy to help in any way.
Thanks for clearing that up and thanks for creating FlightClub! I wonder if the apparent differences are more to do with the model or the assumptions for various inputs. I was also starting to feel like maybe we should create a simulation thread for these topics if people wanted to continue debating the implications of different simulations.
Quote from: mme on 02/20/2017 09:03 pm... I was also starting to feel like maybe we should create a simulation thread for these topics if people wanted to continue debating the implications of different simulations.Sounds like a good idea. I've got a plot for the CRS-10 first stage I'd like to post, but it makes no sense in this thread. There are Mars simulation threads, so perhaps a Falcon one would make sense?
Then my atmospheric model is sound, as it is based on interpolated NASA data. However, the vehicle-specific drag models may need some fine-tuning. I have created a drag coefficient vs Mach number curve for the F9, but it's all educated guessing. I'm sure zlynn1990 has created his own educated guess, independently of mine.
I would copy and paste over but I don't know if it's possible to do tables on this forum? Sorry, NSF noob
I'm surprised that the lift is so large during ascent. It sometimes exceeds the drag by an order of magnitude. Would Falcon Heavy actually fly at angles of attack large enough to generate such lift? I'd have thought that from pitch kick to a low dynamic pressure, FH would be flying a gravity turn.
If it were up to me, I would probably let negative perigees be shown, because it gives you a feeling for the shape of the orbit.
A couple of really minor points/questions. Somewhere in cis-lunar space, the atmospheric density rises to 0.001 kg/m3, and drag becomes postive -- a minor bug in the atmospheric model?
A couple of question: will the Dragon only get so far from the lunar surface at minimum, three or four lunar diameters? I hope for all that money the those astronauts will get to fly few km from the surface
Also: upon re-entry in Earth's atmosphere, I see that heating rate goes up to over one MW/m^2 but air density remains 0.000kg/m^3. Is this expected?
Quote from: manoweb on 03/26/2017 06:37 pmA couple of question: will the Dragon only get so far from the lunar surface at minimum, three or four lunar diameters? I hope for all that money the those astronauts will get to fly few km from the surface
Quote from: OneSpeed on 03/27/2017 11:02 amQuote from: manoweb on 03/26/2017 06:37 pmA couple of question: will the Dragon only get so far from the lunar surface at minimum, three or four lunar diameters? I hope for all that money the those astronauts will get to fly few km from the surface This whole thing really puzzles me. I'd have thought that most passengers would want to approach the moon as closely as possible, and that SpaceX would want to keep the mission profile as simple as possible, especially for the first mission. Put those two factors together, and doesn't it add up to an Apollo-style figure-of-eight free-return trajectory (an in-plane, co-rotating, circumlunar free-return trajectory, in the terminology used in the plot attached to this post)? Then the only burns needed after TLI are small course course corrections.
Quote from: Proponent on 03/27/2017 01:09 pmThis whole thing really puzzles me. I'd have thought that most passengers would want to approach the moon as closely as possible, and that SpaceX would want to keep the mission profile as simple as possible, especially for the first mission. Put those two factors together, and doesn't it add up to an Apollo-style figure-of-eight free-return trajectory (an in-plane, co-rotating, circumlunar free-return trajectory, in the terminology used in the plot attached to this post)? Then the only burns needed after TLI are small course course corrections.It makes a lot more sense if Elon meant 400,000 km when he said 400,000 miles.
This whole thing really puzzles me. I'd have thought that most passengers would want to approach the moon as closely as possible, and that SpaceX would want to keep the mission profile as simple as possible, especially for the first mission. Put those two factors together, and doesn't it add up to an Apollo-style figure-of-eight free-return trajectory (an in-plane, co-rotating, circumlunar free-return trajectory, in the terminology used in the plot attached to this post)? Then the only burns needed after TLI are small course course corrections.
Quote from: envy887 on 03/27/2017 02:54 pmQuote from: Proponent on 03/27/2017 01:09 pmThis whole thing really puzzles me. I'd have thought that most passengers would want to approach the moon as closely as possible, and that SpaceX would want to keep the mission profile as simple as possible, especially for the first mission. Put those two factors together, and doesn't it add up to an Apollo-style figure-of-eight free-return trajectory (an in-plane, co-rotating, circumlunar free-return trajectory, in the terminology used in the plot attached to this post)? Then the only burns needed after TLI are small course course corrections.It makes a lot more sense if Elon meant 400,000 km when he said 400,000 miles.Yes, I get that, but from https://phys.org/news/2017-02-spacex-people-moon-year.html"The paying passengers would make a long loop around the moon, skimming the lunar surface then going well beyond, perhaps 300,000 or 400,000 miles distance altogether. It's about 240,000 miles distance to the moon alone, one way."There appears to be no confusion between miles and kilometers in this statement. The inconsistency I see is in the mission times quoted so far. From the sim, it will be three days to the moon, and another week to the 400k mile apogee. It would be a further week for the return to earth, nearly 17 days altogether.The Grey Dragon is going to be limited in available ΔV compared to Apollo, so I suspect this 'rollercoaster' mission profile is designed to do something spectacular (a new altitude record) with limited resources. This won't be the first Dragon 2 mission, so although certainly risky, it would be a logical incremental step.
How long does it take to get to a 300k mile apogee and back?
“This would be approximately a weeklong mission, and it would skim the surface of the moon, go quite a bit farther out into deep space and then loop back to Earth,” Musk said. “I’m guessing, probably distance wise, maybe 300,000 or 400,000 miles.” http://www.cbsnews.com/news/spacex-moon-mission-planned-for-2018/
Flight Club's recreation of SES-10 is up here: All data (plots and 3D view) are here: https://www.flightclub.io/results/?code=SS10The live replay can be watched here: https://www.flightclub.io/world/?code=SS10&w=2The big difference between my simulation and OneSpeed's above is that I'm not using the uprated Merlin 1D thrust figures - my 1D's are still at 756kN instead of 845kN. However, with this thrust figure at close to 100% (dropped to 90% for MaxQ), my trajectory has still matched the webcast data closely.So who knows what to think. Do we have a collection of Merlin thrust vs. Mission anywhere? Did this mission definitely use the 845kN version?
...10,000kg payload to 32.5deg 250km by 220km orbit with second stage burn to depletion.MECO at t+145s, 1.5km/s.First stage boostback to LZ-1, with only 99km apogee...Seems like a pretty nice time for the first stage. Are there any obvious issues with it though?
https://www.flightclub.io/results/?id=0d9a43bc-328a-481d-9cbc-22321c3f95d3&code=NONE
Seems like a pretty nice time for the first stage. Are there any obvious issues with it though?
Quote from: Flying Beaver on 04/12/2017 09:43 pmhttps://www.flightclub.io/results/?id=0d9a43bc-328a-481d-9cbc-22321c3f95d3&code=NONEIf you visit the link posted, you'll see there's a graph of throttle settings over time. The MaxQ throttle looks like 70% from T+50 to T+75. Bit extreme, I reckon, but probably explains the dV deficiency.Quote from: Flying Beaver on 04/12/2017 09:43 pmSeems like a pretty nice time for the first stage. Are there any obvious issues with it though?The main problem I have is that your landing burn lasts for almost 90s. The retropropulsion through the entire lower atmosphere is the reason why the aerodynamic pressure on descent is so low, but this is extremely inefficient! Also the landing burn is at about 50% throttle the entire time which is also very inefficient. Best to do as short a landing burn as possible to minimize gravity losses - so you wanna maximise aerobraking and burn at a high throttle setting when you do start the burn. Kudos getting to orbit on the first attempt though, that's pretty impressive
But it is still 10tons to LEO, with RTLS, no matter how inefficient the landing burn. Would the reason for SpaceX not using a profile like this be about having a buffer for second stage performance?
A preliminary S1 profile for NROL-76. Thrust still appears to be 90% of rated, so perhaps not Block 4.
I already did analysis here and here, if you want to compare and contrast.
Interesting. Did you subtract the acceleration caused by gravity? Also, what is the jump in velocity near 245s and 337s?
Quote from: Welsh Dragon on 05/02/2017 12:19 pmI already did analysis here and here, if you want to compare and contrast.Thanks, I should explain what I've done, perhaps it's slightly different. <snip>
Mine are just straight plots from the telemetry.
I literally sit there and copy the numbers off manually. Every 5 seconds for the whole flight, every second for the burns.
OCR data, chart and spreadsheet, for SpaceX's Inmarsat-5
This is the comparison between SES-10 and Inmarsat-5
Quote from: manoweb on 05/17/2017 12:42 amThis is the comparison between SES-10 and Inmarsat-5Fantastic, thank you!You can clearly see the throttle-down for trans-sonic is at around 320 m/s for each. But Inmarsat hits transsonic earlier and higher, and accelerates through it faster than SES-10. The Inmarsat booster is going higher and accelerating faster all the way to staging despite pushing a larger payload.SES-10 is known to be a v1.2 Block 1 booster, so Inmarsat definitely was upgraded. But was it upgraded from NROL-76? The first stage telemetry could show the difference. It would be awesome if you could overlay that data.Interestingly, the Mvac doesn't appear to have been upgraded. The lower acceleration of the second stage is explained by the higher payload mass.
Let's not all forget that SES 10 S1 had a lot more mass going uphill with Landing legs and Grid Fins, plus whatever other re-usability feature on First stage weren't there for Inmarsat.. Do those more than offset the heavier mass of the Satellite in terms of First Stage performance?
Quote from: TrueBlueWitt on 05/17/2017 07:12 amLet's not all forget that SES 10 S1 had a lot more mass going uphill with Landing legs and Grid Fins, plus whatever other re-usability feature on First stage weren't there for Inmarsat.. Do those more than offset the heavier mass of the Satellite in terms of First Stage performance?The landing legs and grid fins are certainly a factor, and SES-10 may not be the best point of comparison. It launched at only 87.5% of rated thrust, which makes sense when you consider it was the first ever re-use of a first stage, and SpaceX would have been very keen to give it the best chance of success. Perhaps Echostar 23 would be a better reference? Anyway, Inmarsat-5 appears to have launched at 90% of rated thrust, and although it went to 94% after Max Q, I'm not sure we've seen a block 4 yet. Interestingly, the second stage appears to have reverted from 107% to 98% of rated thrust for the first minute or so, and none of the stages have used any high AoA manoeuvres this time. Apologies for the step in velocity at 150kms.
The landing legs and grid fins are certainly a factor, and SES-10 may not be the best point of comparison. It launched at only 87.5% of rated thrust, which makes sense when you consider it was the first ever re-use of a first stage, and
I pulled 10-second intervals off the webcasts for both I5F4 and Echostar 23. The difference in burn time appears to be close to the difference in acceleration, suggesting I5F4 had about 2% additional prop load but ran at the same thrust except around transonic.
Quote from: envy887 on 05/17/2017 04:03 pmI pulled 10-second intervals off the webcasts for both I5F4 and Echostar 23. The difference in burn time appears to be close to the difference in acceleration, suggesting I5F4 had about 2% additional prop load but ran at the same thrust except around transonic. Hello Envy887, pulling values manually from the video seems a pretty boring task... If you need just point me to which mission you like and I can extract the telemetry data easily, all ~16000 points of it. In the previous posts I always provided either a CSV file or LibreOffice spreadsheet, is the format not good enough? I'd rather spend time on the telemetry extraction tool, and see you guys do the spreadsheet analysis
Points of interest include:2. What appears to be a minimum thrust single engine ullage burn starting half way through the flip at 2:40.
Can someone here please calculate from available data what is performance of expendable F9 1.2 block 3 and expendable F9 1.2 block 5 to GTO (with some reserve for sending 2nd stage to graveyard orbit)
Quote from: Rebel44 on 07/06/2017 08:31 pmCan someone here please calculate from available data what is performance of expendable F9 1.2 block 3 and expendable F9 1.2 block 5 to GTO (with some reserve for sending 2nd stage to graveyard orbit)There are no available data on Block 5 right now.
...There are no available data on Block 5 right now.
Quote from: Rebel44 on 07/06/2017 08:31 pmCan someone here please calculate from available data what is performance of expendable F9 1.2 block 3 and expendable F9 1.2 block 5 to GTO (with some reserve for sending 2nd stage to graveyard orbit)If you mean direct to GSO, then my my calculations Block 3/4 will put about 1200 kg and Block 5 about 4000 kg direct to GSO. The spacecraft RCS can probably handle the move to graveyard orbit, it's a >1 second burn on a 38% throttled MVac.
Quote from: envy887 on 07/06/2017 08:56 pmQuote from: Rebel44 on 07/06/2017 08:31 pmCan someone here please calculate from available data what is performance of expendable F9 1.2 block 3 and expendable F9 1.2 block 5 to GTO (with some reserve for sending 2nd stage to graveyard orbit)If you mean direct to GSO, then my my calculations Block 3/4 will put about 1200 kg and Block 5 about 4000 kg direct to GSO. The spacecraft RCS can probably handle the move to graveyard orbit, it's a >1 second burn on a 38% throttled MVac.Yeah, I mixed up GTO and GEOThanks for the estimate!
The Formosat-5 mission had an unusually light payload of 475kg, and so there was a lot of excess ΔV available. A conventional mission profile would require at least two S2 burns: first to an elliptical orbit, and a second circularisation burn at apogee. But Formosat-5 was delivered to a 730km x 717km orbit with a single S2 burn. So what then was the mass penalty for this? Here is a compari-sim between Formosat-5 and a modified BulgariaSat profile, also with a 475kg payload, and polar injection to a 725km circular orbit.
The FCC STA for mission 1346 (the FH Demo mission) has the coordinates for the ASDS landing of the core booster about 340kms downrange from LC-39A. This corresponds with an extremely lofted trajectory, not unlike that used for Formosat-5. In the Formosat-5 case, a single S2 burn took the satellite to a circular orbit. What could FH achieve with a similar profile?Here is a speculative FH simulation bounded by an ASDS landing about 340kms downrange, and a 6mT payload, the same as advertised by SpaceX to GTO. By tuning the orientation towards the end of the S2 burn, it is possible to set the perigee of the orbit achieved to a suitable re-entry altitude about 5.5 hours after lift-off. Entry velocity would be about 10km/s.
What are you using as the simulator?
Quote from: john smith 19 on 09/17/2017 07:51 pmQuote from: OneSpeed on 09/16/2017 01:57 amWhat are you using as the simulator? The program is called SpaceSim. It is written in C# and you can download it and the source code here: https://github.com/zlynn1990/SpaceSim
Quote from: OneSpeed on 09/16/2017 01:57 amWhat are you using as the simulator?
<snip> But what if the Falcon S2 could be modified (as others have suggested) to have comparable dynamics to the BFS, and still support existing payloads? Here is a speculative 'Frankenstein' approach:3. Three strakes of a similar form to the BFS strakes, but containing extra nitrogen tanks and thrusters. The strakes could also have the BFS split body flaps mentioned (but not so far visualised) for additional control authority.
3. Bangabandhu-1 was not sent to a super-synchronous GTO, whilst BulgariaSat-1, a slightly heavier satellite was. Is that down to differing customer requirements?
2. Because Iridium-7s S1 burn is three seconds shorter, with higher overall throttle, its velocity is generally faster and at a lower altitude, so heating flux should be slightly greater. This is at odds with the extra TPS on GPS-III and Iridium-8, so I'm not sure what's going on there.
Quote from: OneSpeed on 01/20/2019 07:09 am2. Because Iridium-7s S1 burn is three seconds shorter, with higher overall throttle, its velocity is generally faster and at a lower altitude, so heating flux should be slightly greater. This is at odds with the extra TPS on GPS-III and Iridium-8, so I'm not sure what's going on there.I don't think that Iridium-8 used extra TPS. Note that same shape on the fairing tip is typical for any Fairing 1.0., which was used for Iridium-8 mission. Some other found Fairing 1.0. examples with this detail .. FHDemo, Intelsat35e, or SES9.In contrast with previous Iridium missions (Iridium-6 and 7), where have been used Fairing 2.0., with circular shape on the tip.The only exception is GPS-III mission, where Fairing 2.0. had black extra TPS.
Iridium 8 definitely has a cap piece on top of the fairing in the same place as the GPS-III mission, albeit in white instead of black. Different bolt-on fairing nose parts for different ascent profiles?
I don't think that Iridium-8 used extra TPS.
They had no crew and just a few hundred kg of cargo. There should have been literally tonnes of extra margin. Was it *all* used to reduce MaxQ?
Since this was a demo flight, you'd think they would have wanted to demonstrate, if not the maximum possible mass to station, at least the nominal amount of mass to station. And though crew mass simulators in the seats seems like it might be needed to demonstrate that the seats won't break, it seems odd that you'd not at least pack water in those seats.Isn't the point of Dragon-2 to eliminate the need to get rides on Soyuz? That thing is packed nearly solid on the way up. If Dragon-2 is going to replace it, it'll need to bring the same amount of stuff, at minimum, right?So how was this a demo of that capability?
Has anyone ever tried simulating how far a Starship could get without Superheavy for the purposes of Point to Point? If not how easy would this be?
It was my understanding that they were conducting the abort at Max drag, not max q. Which is typically a little after max q.
Quote from: S.Paulissen on 04/06/2019 02:46 amIt was my understanding that they were conducting the abort at Max drag, not max q. Which is typically a little after max q.Yes, the simulation predicts MaxQ at 59 seconds, and max drag at 60 seconds. Oddly, both of these events are well before the separation event range which is from 83-100 seconds.
For MaxQ to be different than max drag, the drag coefficient would have to be changing. Are you modelling that? How do you guess the drag coefficients at different speeds?
(3 * 39% + 6 * 100%)/9 = 79.7% > 71%
Quote from: Barley on 04/11/2019 09:28 pm(3 * 39% + 6 * 100%)/9 = 79.7% > 71%My thoughts entirely. so what gives?
Quote from: Slarty1080 on 04/11/2019 11:12 pmQuote from: Barley on 04/11/2019 09:28 pm(3 * 39% + 6 * 100%)/9 = 79.7% > 71%My thoughts entirely. so what gives?Speculation on other threads is that some booster engines cut out early to limit acceleration further, there was a callout along those lines
Quote from: Barley on 04/11/2019 09:28 pm(3 * 39% + 6 * 100%)/9 = 79.7% > 71%Don't forget that the side boosters throttled down at various points as well. They were not running flat out.
Quote from: Lar on 04/11/2019 11:35 pmQuote from: Barley on 04/11/2019 09:28 pm(3 * 39% + 6 * 100%)/9 = 79.7% > 71%Don't forget that the side boosters throttled down at various points as well. They were not running flat out.Yes I heard them talk about that during the FH launch we just saw. The question is why? From a purely performance angle it would be better to leave the side boosters running flat out and throttle the core further to retain propellant in the core for later use.If only 3 engines on the core are throttle capable then they might not be able to provide sufficient throttle range, which begs the question why not make more engines throttle capable on the core stage if it would translate into a performance increase?There must be a good reason why they don't do this. It might be structural perhaps that level of thrust from the side boosters might be too much stress for the core?
For Side Shutdown 1, 2 and 3, do we have a good idea what combination of engines are disabled at these times?
Quote from: ATPTourFan on 04/15/2019 02:47 pmFor Side Shutdown 1, 2 and 3, do we have a good idea what combination of engines are disabled at these times?Judging from ground footage, my guess is for shutdowns #1 and #2 that it's engines 6 and 7 on the boosters. No idea about the sequencing and pairing (i.e. if it's 7-7 and 6-6 or 7-6 and 6-7), though.
Quote from: Slarty1080 on 04/12/2019 02:29 amQuote from: Lar on 04/11/2019 11:35 pmQuote from: Barley on 04/11/2019 09:28 pm(3 * 39% + 6 * 100%)/9 = 79.7% > 71%Don't forget that the side boosters throttled down at various points as well. They were not running flat out.Yes I heard them talk about that during the FH launch we just saw. The question is why? From a purely performance angle it would be better to leave the side boosters running flat out and throttle the core further to retain propellant in the core for later use.If only 3 engines on the core are throttle capable then they might not be able to provide sufficient throttle range, which begs the question why not make more engines throttle capable on the core stage if it would translate into a performance increase?There must be a good reason why they don't do this. It might be structural perhaps that level of thrust from the side boosters might be too much stress for the core?Has more to do with the G-Loads on the payload. G-Limits are to not damage 1) the Payload and 2) the center core. Jerry always mentions, on the broadcast, that the throttling is to reduce g-loads on the payload and the vehicle.... there is a fully fueled 2nd stage + Payload being pushed by an increasingly empty booster stages.
Here's a plot of velocity and acceleration over time for Arabsat-6A, with annotated events....
Quote from: Wolfram66 on 04/15/2019 06:53 pmQuote from: Slarty1080 on 04/12/2019 02:29 amQuote from: Lar on 04/11/2019 11:35 pmQuote from: Barley on 04/11/2019 09:28 pm(3 * 39% + 6 * 100%)/9 = 79.7% > 71%Don't forget that the side boosters throttled down at various points as well. They were not running flat out.Yes I heard them talk about that during the FH launch we just saw. The question is why? From a purely performance angle it would be better to leave the side boosters running flat out and throttle the core further to retain propellant in the core for later use.If only 3 engines on the core are throttle capable then they might not be able to provide sufficient throttle range, which begs the question why not make more engines throttle capable on the core stage if it would translate into a performance increase?There must be a good reason why they don't do this. It might be structural perhaps that level of thrust from the side boosters might be too much stress for the core?Has more to do with the G-Loads on the payload. G-Limits are to not damage 1) the Payload and 2) the center core. Jerry always mentions, on the broadcast, that the throttling is to reduce g-loads on the payload and the vehicle.... there is a fully fueled 2nd stage + Payload being pushed by an increasingly empty booster stages.Yes I think your right. The 10% extra thrust on the engines for this FH compared to the first is effectively wasted.
Quote from: OneSpeed on 04/12/2019 09:45 pmHere's a plot of velocity and acceleration over time for Arabsat-6A, with annotated events....Would you be willing to post the data behind this plot? Would you have altitude as well? Through stage 2 burn?
Why is there a step change in "velocity" and heating rate at around 225 seconds?