... 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?