Author Topic: SpaceX Falcon Mission Simulations  (Read 40311 times)

Offline john smith 19

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Re: SpaceX Falcon Mission Simulations
« Reply #100 on: 09/18/2017 04:45 PM »
What 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
Noted.
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Offline IainMcClatchie

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Re: SpaceX Falcon Mission Simulations
« Reply #101 on: 09/18/2017 08:15 PM »
That's some nice work.

I don't mean to look a gift horse in the mouth, but I'll note that all the zooming in and out seems less than ideal.  You might have two views simultaneously, one close up showing the spacecraft attitude, and one far away showing the trajectory.

Offline deruch

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Re: SpaceX Falcon Mission Simulations
« Reply #102 on: 09/22/2017 03:46 AM »
<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.


Not sure about the rest, but this would invalidate the launch for USAF certification as it would entail a change to "major airframe structure" of the launch vehicle which is one of the things that would require a new vehicle certification.  It's cool as an idea that could potentially achieve 2nd stage reuse, but it certainly won't be the way they attempt on the FH demo mission.  Beyond that, something like it could be done if they are willing to produce multiple vehicle variants, i.e. one upper stage for FH and one for F9.
« Last Edit: 09/22/2017 03:48 AM by deruch »
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Online OneSpeed

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Re: SpaceX Falcon Mission Simulations
« Reply #103 on: 10/28/2017 03:58 AM »
With the Falcon Heavy Demo Mission approaching, I thought a 'compari-sim' between CRS-11 and a Falcon Heavy launch to LEO might be of interest.


Online OneSpeed

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Re: SpaceX Falcon Mission Simulations
« Reply #104 on: 12/11/2017 10:37 AM »
For better or for worse, the Falcon Heavy demo mission payload will be a cherry red Tesla Roadster. I'm still assuming the ASDS will be only 342kms downrange from LC-39A. If so, this demands a very lofted profile, something like Formosat-5, which used a single S2 burn to deploy a very light payload.

Launch opportunities for such a profile are daily for most of the next year, but assuming a launch on Feb 1st 2018, the sim predicts that the two side boosters would stage at 2050 m/s, and perform a 30 second horizontal boostback burn on the way to an apogee of 285 kms. The core booster would stage at 3040 m/s, with a ballistic trajectory that unchecked would have a 485 km apogee and land about 900 kms downrange. In order for it to reduce the downrange to 342 kms, it would need to flip to retrograde for its boostback burn, which could be made more efficient if it utilised 5 rather than the usual 3 Merlin engines.

The S2 burn would commence at an altitude of 190 kms, and SECO would be at 1200 kms. The TMI ΔV requirement at this altitude would be significantly less than that from sea level, so the shutdown velocity would be 10.6 km/s. The transit to aphelion would take 238 days.


Online OneSpeed

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Re: SpaceX Falcon Mission Simulations
« Reply #105 on: 04/01/2018 12:52 AM »
Here is the latest simulation I've been working on in collaboration with NSF member Zach Lynn. This simulation shows the Falcon Heavy demo flight that took place earlier last month. This is an update from the previous video posted, as the flight profile now matches the webcast telemetry very closely. Additionally, this video shows the predicted Earth flyby in 2091. Simulating the n-body system out this many years into the future requires a more course time-step. Therefore, the exact flyby date and distances predicted by this simulation are just 'best effort'.

Special thanks to NSF member Jay DeShetler for the hi-fidelity launch audio recorded live near the LC-39A HIF.



Online OneSpeed

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Re: SpaceX Falcon Mission Simulations
« Reply #106 on: 05/14/2018 12:51 PM »
Here is a 'comparisim' between Bangabandhu-1 and BulgariaSat-1. My recent sims pointed to block 4 being 91% of block 5 thrust, but the Falcon Heavy S1 cores ran at 92% thrust. From this I've concluded the SpaceSim dry mass estimates were too low, and for Bangabandhu I've added 1% of GLOW (about 5.5 mT) to the S1 and S2 dry masses. Even with this additional mass, I've only had to run Bangabandhu at 97% thrust at lift-off, gradually throttling to 90% before reaching 4Gs of acceleration just before MECO. Perhaps SpaceX were conservative on the first block 5 flight, and more performance will be demonstrated in the near future?

Points of interest:

1. Block 5 initial acceleration was 1.43Gs, only slightly less than the Falcon Heavy demo at 1.47Gs.
2. The Bangabandhu-1 S2 ran at a constant 96% of block 4 thrust up to about 4Gs. Again, perhaps there is more performance to come.
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?

« Last Edit: 05/14/2018 12:52 PM by OneSpeed »

Offline deruch

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Re: SpaceX Falcon Mission Simulations
« Reply #107 on: 05/14/2018 03:24 PM »
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?

Bangabandhu-1's orbit inclination was ~4.5o less than BulgariaSat-1.  Not sure why they wanted it, but I'm sure it was a customer choice.
Shouldn't reality posts be in "Advanced concepts"?  --Nomadd

Offline leetdan

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Re: SpaceX Falcon Mission Simulations
« Reply #108 on: 05/14/2018 04:08 PM »
These are awesome!  Have you ever considered exporting some of these to KMZ files?  This would be useful to the general public for visualizing each path, as well as planning launch viewing and photography.

Online OneSpeed

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Re: SpaceX Falcon Mission Simulations
« Reply #109 on: 06/11/2018 12:57 PM »
Here is a 'comparisim' between Iridium NEXT 4 and Iridium / Grace FO. Iridium NEXT 4 was legless, whilst Iridium / Grace FO had a lighter payload, giving similar performance off the pad. However, Iridium Grace needed to deliver its payloads to two different orbits with a minimum of second stage restarts. By my count, three is as many as have been demonstrated (someone else may have kept better track of this).

The first Iridium NEXT 4 S2 burn placed it in a 182 x 625km orbit, and only required a circularisation burn at apogee before deployment of the 10 Iridium satellites to 625 x 625kms. They subsequently raised themselves to their 780 x 780km operational orbits.

The first Iridium GRACE S2 burn placed it directly into a 505 x 483km orbit, ready to deploy the Grace FO satellites. This required a very lofted profile, with the last few minutes of the S2 burn at a relatively high angle of attack, and hence with significant cosine losses. The losses were minimised by throttling S2 back near 60% throttle over those last few minutes of its first burn, and so extending its duration to over the T+10 minute mark of the flight. By extending the duration, the AoA required to reach the required orbit was slightly reduced, minimising losses. The second S2 burn placed Iridium GRACE in a 482 x 720km orbit, from which the 5 Iridium satellites will have had to raise and circularise themselves.