Author Topic: SpaceX Falcon Mission Simulations  (Read 25018 times)

Offline manoweb

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Re: SpaceX Falcon Mission Simulations
« Reply #80 on: 05/17/2017 07:39 PM »
Yeah so far I've done NROL-76 (first stage), Inmarsat-5, SES-10. I can do Echostar-23. I think I will do all launches in 2017 now that I have built my tool. I will include also the timestamps

Offline OneSpeed

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Re: SpaceX Falcon Mission Simulations
« Reply #81 on: 06/05/2017 01:51 PM »
Here is a sim of the CRS-11 first stage profile.

Points of interest include:
1. The booster appears to launch at slightly less than full throttle (84% of the published block 5 figures) before throttling up to 91% of block 5 after about 5 seconds.
2. What appears to be a minimum thrust single engine ullage burn starting half way through the flip at 2:40.
3. A 1:3:1 engine entry burn at 6:10.


Offline hkultala

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Re: SpaceX Falcon Mission Simulations
« Reply #82 on: 06/05/2017 02:54 PM »
Highest throttle at boostback burn.

So they do not want to risk the payload / want to maximize reliability when stage 2 and payload are attached by using it with "full throttle", and are only using full throttle for boostback. 

(but propably they would use full throttle if they would lose one engine, to compensate for the loss of thrust)

And high T/W is very important for the boostback burn, as it's flying away from the launch & landing site and the faster the boostback burn is, the shorter distance it has to travel.

« Last Edit: 06/05/2017 02:57 PM by hkultala »

Offline deruch

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Re: SpaceX Falcon Mission Simulations
« Reply #83 on: 06/08/2017 04:28 AM »
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.


I think this is related to how fast they are trying to do the flips now.  With all the authority of the burning engine, they can afford to do a higher rotational speed flip and still ensure that they can maintain enough prop at the bottom of the tanks and that they can handle any off-axis impulses from any sloshing.
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Offline OneSpeed

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Re: SpaceX Falcon Mission Simulations
« Reply #84 on: 07/01/2017 08:19 AM »
Here is a sim of BulgariaSat-1. The telemetry for this mission and the next is not complete, but there are similar missions that help fill in the gaps, in this case SES-10.

This mission was of course most notable for the first coast-to-coast re-use of a booster, but the profile had a couple of points of interest as well.

1. As per SES-10, the high AoA of the entire rocket from the 1:40 mark. Does anyone know why this manoeuvre has only been used for these particular GTO satellite missions?

2. The initial S2 orbit is about 160 x 480kms, and the GTO burn occurs at about 250kms. I've seen it suggested that ideally such a burn should occur at perigee, where velocity is highest, minimising the ΔV requirement. Does anyone have any insight into why the GTO burn was done this particular way?

3. Elon Musk: 'Rocket was suddenly slammed sideways right before landing. Heavy gust or something malfunctioned onboard. Reviewing telemetry.' I've attempted to model the effect of a heavy gust at the 8:30 mark, at about 400m altitude.


Offline Rebel44

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Re: SpaceX Falcon Mission Simulations
« Reply #85 on: 07/06/2017 08:31 PM »
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 GEO (with some reserve for sending 2nd stage to graveyard orbit)
« Last Edit: 07/06/2017 08:57 PM by Rebel44 »

Offline jpo234

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Re: SpaceX Falcon Mission Simulations
« Reply #86 on: 07/06/2017 08:32 PM »
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)
There are no available data on Block 5 right now.
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Offline Rebel44

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Re: SpaceX Falcon Mission Simulations
« Reply #87 on: 07/06/2017 08:55 PM »
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)
There are no available data on Block 5 right now.

There is posted performance on SpaceX website for LEO and GTO (and few others) which based on what we know appears to be expected block 5 (expendable) performance
22 800 kg to LEO
 8 300 kg to GTO

Even estimated GEO performance based on block 3 performance would be appreciated.
« Last Edit: 07/06/2017 08:56 PM by Rebel44 »

Online envy887

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Re: SpaceX Falcon Mission Simulations
« Reply #88 on: 07/06/2017 08:56 PM »
...
There are no available data on Block 5 right now.

The listed performance on SpaceX website is for a Block 5 launch. Block 3/4 will be retired long before anyone buying a launch right now gets to the pad.

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)

Expendable Block 3/4 mix to GTO is what you just saw yesterday: 6781 kg to GTO, slightly supersync. There's no need for a GTO graveyard orbit, the upper stages decay quickly. Expendable block 5 is supposed to ptu 8300 kg to GTO.

If you mean direct to GSO, then my my calculations Block 3/4 will put about 1200 2100kg and Block 5 about 4000 3000 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.

Edit: poor recollection of previous calculations, corrected.
« Last Edit: 07/06/2017 09:09 PM by envy887 »

Offline Rebel44

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Re: SpaceX Falcon Mission Simulations
« Reply #89 on: 07/06/2017 08:58 PM »

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)

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 GEO
Thanks for the estimate!

Online envy887

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Re: SpaceX Falcon Mission Simulations
« Reply #90 on: 07/06/2017 09:08 PM »

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)

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 GEO
Thanks for the estimate!

Certainly, but I'm afraid I recalled wrong above - I was calculating in pounds and for FH a few days ago :D

Rechecking my math, Block 3/4 gets 6800 kg to GTO, with a stage mass of 4500 kg and Isp of 348, that is about 2100 kg to GSO.
Block 5 gets 8300 kg to GTO, with same stage and Isp that is about 3000 kg to GSO.

LOX boiloff will reduce this somewhat, but I don't have a good way to estimate that.

Offline OneSpeed

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Re: SpaceX Falcon Mission Simulations
« Reply #91 on: 07/09/2017 04:52 AM »
Here is a 'compari-sim' between the Inmarsat-5 F4 and Intelsat-35e mission profiles. They are very similar in many ways, but:

1. The relative effect of the S1 throttle and shutdown profiles is interesting to view.
2. The sims generated the following post SECO-2 S2 masses, with and without a 200Kg allowance for plane change:
MissionNo plane changeWith plane change
Iridium-5 F45.5mT5.3mT
Intelsat-35e5.3mT5.1mT
I'd assumed both missions were burn to depletion, but perhaps some of the difference can be attributed to a variation in fuel densification between the missions?

« Last Edit: 07/09/2017 06:03 AM by OneSpeed »

Offline OneSpeed

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Re: SpaceX Falcon Mission Simulations
« Reply #92 on: 08/15/2017 03:06 PM »
Here is a comparison of CRS-11 and 12. Although Hans Koenigsmann suggested that the CRS-11 and 12 profiles would be very similar, there are some differences.

Edit: To summarise:
1. From launch to throttle back for Max-Q is almost identical. The small difference is accounted for by the extra 200kgs of payload.
2. CRS-12 stays throttled back for longer than CRS-11, perhaps to minimize stress on the rocket and/or the payload?
3. CRS-12 stages lower and slower, and its boostback burn results in a slightly lower S1 apogee.
4. CRS-12 compensates for the reduced uprange ballistic trajectory by using a slightly higher AoA to enhance glide after the entry burn. Although the highest AoA so far for a RTLS profile, ASDS profiles have used similar AoA in the past.
5. CRS-12 also uses a shorter and higher thrust S2 burn to compensate for the payload and ΔV differences.

« Last Edit: 08/16/2017 02:02 AM by OneSpeed »

Offline OneSpeed

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Re: SpaceX Falcon Mission Simulations
« Reply #93 on: 08/27/2017 04:17 AM »
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.


Online titusou

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Re: SpaceX Falcon Mission Simulations
« Reply #94 on: 09/10/2017 04:06 PM »
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.

This, by far, is the best explanation (and easiest) on how SpaceX pull off circular orbit with single S2 burn.

Superb work OneSpeed!

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Offline OneSpeed

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Re: SpaceX Falcon Mission Simulations
« Reply #95 on: 09/11/2017 01:30 PM »
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.


Online karki

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Re: SpaceX Falcon Mission Simulations
« Reply #96 on: 09/11/2017 11:01 PM »
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.



Are you assuming SpaceX will be testing S2 survivability at GTO reentry velocity? What's the consensus around here on a non-standard S2 being considered an adequate test of Falcon Heavy in the eyes of the customer, either official (for things like DoD requirements) or unofficial (general PR. customers "feel good" about it)?

Offline OneSpeed

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Re: SpaceX Falcon Mission Simulations
« Reply #97 on: 09/16/2017 01:57 AM »
SpaceX have indicated that they would like to recover the Falcon Heavy Demo second stage, but the difficulty of this task cannot be underestimated. Following on from the previous sim, Earth EDL at 10km/s will generate heat over 10x greater than S1 recovery. With its mass concentrated at the tail, the Falcon S2 would not inherently be passively stable, so providing sufficient control authority would be challenging. 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:

1. An overlapping clamshell nose cone that would not prevent the use of the current fairings and PAF.
2. Some ballast near the nose, (a toroid?) sufficient to make the ship passively stable.
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.
4. Additional TPS, and a shroud to protect the Merlin Vacuum engine during re-entry.
5. The sim shows that for an S2 dry mass of 6mT, the terminal velocity is well under 100m/s. This means that a parafoil (as is likely for the v2.0 fairings) would be a viable option for landing. There would then be no need for supersonic retropropulsion or a propulsive landing (which would have required additional sea level engines and fuel). The parafoil (and perhaps a drogue chute) could be housed in the dorsal strake, just above and behind the centre of gravity.

For a typical ISS mission profile, the Falcon S2 might re-enter after a single orbit and land at a large open space like Edwards Air Force base. Here then is a simulation of such an Earth EDL profile (note: I don't have a 3D model for the 'Frankenstage', so I've utilised a cargo BFS model where roll is required).


Offline john smith 19

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Re: SpaceX Falcon Mission Simulations
« Reply #98 on: 09/17/2017 07:51 PM »
What are you using as the simulator?
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Offline OneSpeed

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Re: SpaceX Falcon Mission Simulations
« Reply #99 on: 09/18/2017 02:13 AM »
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
« Last Edit: 09/18/2017 09:53 PM by OneSpeed »

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