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Old 02-07-2018, 04:14 PM   #16
barrygolden
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Hey Brian Thanks again for your work on these. We were down the hall watching the launch and I had my laptop up and running to track the mission. Again lots of comments about orbiter.

The views from Starman were awesome. I remember the TV from Apollo and it was hard to tell much so these views were out of this world . I wished a solar panel would have been added for a view of Mars months from now and a look at the car.
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Old 02-07-2018, 04:29 PM   #17
BrianJ
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Hi Barry,
have you guys stopped partying yet?
Congrats to all at SpaceX
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Old 02-07-2018, 07:36 PM   #18
llarian
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Any body have the orbital elements of the Roadster, yet?
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Old 02-07-2018, 09:14 PM   #19
Marg
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Great autopilot, etc., but I would like to note, that deflection smokes could be much longer sustained. In my multistage2015 experiments I made particles with long life times (16 secs), and FPS did not suffer on my moderate PC. Here are some my parameters...

Srcsize=12.000
Srcrate=5000.000
V0=150.000
Srcspread=0.750
Lifetime=16.000
Growthrate=2.500
Atmslowdown=0.750

Also would not say anything about exhaust (classic Orbiter look here). But after I saw Delta-IV-Heavy... there I saw something that made rethink limitations of Orbiter. They looked really impressive (though there is a cryogenic fuel, not kerosine). If I remember correctly, there was a more noticable texture component, with some particles.
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Old 02-07-2018, 10:02 PM   #20
Marijn
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Quote:
Originally Posted by llarian View Post
 Any body have the orbital elements of the Roadster, yet?
NORAD ID: 43205. Not sure if that name is going to stick..

https://www.n2yo.com/satellite/?s=43205

edit: and scroll down for the numbers.

Last edited by Marijn; 02-07-2018 at 10:04 PM.
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Old 02-08-2018, 11:09 AM   #21
boogabooga
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If it's on an escape trajectory, NORAD TLEs and sites that track them such as n2yo are not going to be relevant for long, since these are meant for earth orbit.
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Old 02-08-2018, 12:38 PM   #22
BrianJ
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Quote:
Originally Posted by Marg View Post
  I would like to note, that deflection smokes could be much longer sustained. In my multistage2015 experiments I made particles with long life times (16 secs), and FPS did not suffer on my moderate PC
Hi Marg, I'll have another go at improving the particle streams when I get some time, but my PC doesn't react well to lots of particles, so I tend to keep it minimal.

Couldn't find any orbital elements on that n2yo page - did anybody grab them?

Cheers,
Brian
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Old 02-08-2018, 03:55 PM   #23
Marijn
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Quote:
Originally Posted by BrianJ View Post
 Couldn't find any orbital elements on that n2yo page - did anybody grab them?
Check out these Twitter accounts:
https://twitter.com/planet4589
https://twitter.com/marco_langbroek

---------- Post added at 04:55 PM ---------- Previous post was at 04:45 PM ----------

Hello Brian,

The launch indeed was very memorable. I really enjoyed all the excitement leading up to it.

I did a few lauches afterwards to check how events did match up against the SpaceX webcast and I noticed that they do not sync up as good as the Falcon9 did.

Booster separation of the real FH was at 2:34 into the launch at 60km altitude. Even with less than minimal reserve fuel, the FH in Orbiter seperates the boosters 14 seconds before at 50km.

I am not sure why that is. It seems the throttle of the side-boosters was varied quite a bit during the launch. I am not sure if that explains it, because I would expect an altitude above 60km if that's the explanation. I tried correcting for this by using negative crossfeed, but that's not an option.

Any ideas on this?
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Old 02-09-2018, 09:09 AM   #24
vchamp
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Quote:
Originally Posted by Marijn View Post
 Booster separation of the real FH was at 2:34 into the launch at 60km altitude. Even with less than minimal reserve fuel, the FH in Orbiter seperates the boosters 14 seconds before at 50km.

I am not sure why that is. It seems the throttle of the side-boosters was varied quite a bit during the launch. I am not sure if that explains it, because I would expect an altitude above 60km if that's the explanation. I tried correcting for this by using negative crossfeed, but that's not an option.

Any ideas on this?
While I don't have an answer to the question why events don't sync, here are my observations (I set apogee and perigee to 250 km in the config window).

In the video engines started to ignite about 5-6 seconds before the liftoff and I'm not sure but it seems that the center core was working at less thrust than the side cores from the beginning of the ascent. In Orbiter liftoff starts almost immediately after ignition and at full thrust, and it takes less time (4 vs 6 seconds, at double speed) for the vessel to ascend past the tower. This should already give some difference in the amount of fuel burned.

The simulated vessel is gaining speed and altitude at higher rate than the real. That should mean that side cores throttled down too while in Orbiter only the center core is throttled down. At the moment of boosters separation the speed and altitude roughly match the values in the video, but in Orbiter it occurs 15 seconds earlier.

At T + 3 minutes the simulated vehicle's speed is higher by 900 km/h and altitude is higher by 20 km.

At MECO the speed is higher by 2000 km/h, altitude by 45 km. In the sim MECO occurs 15 seconds later this time than in the video. So while side cores work less time, the center core works longer than in the real launch. Should it mean that they throttled down the center core to a lesser extent (maybe to 70%) and at the same time the rocket produced much less than the full thrust?
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Old 02-09-2018, 02:48 PM   #25
BrianJ
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Hi,
remember there isn't much info from SpaceX - most parameters I'm using for the add-on are garnered from comments dropped at presentations, and (probably quite good) guesses from people who know about this stuff.

I concur with the observations re:timing/alt/vel of booster separation.

I heard a call-out for side-boosters throttle down ~20s before sep., so that would increase the burn time/alt at separation, compared to 100% throttle all the way. Indeed, possible the side-boosters were at ~95% all the way. Or some throttle variation. Or maybe they were using less fuel-reserve than I estimate. Or some combination of above.

Core-booster may have been using more fuel-reserve than I estimate, 100000kg works well timing wise for my add-on, or may have had a higher throttle setting pre- side-booster separation.

Certainly no shortage of dV for this payload, so they could have used a lot more fuel-reserve for boostbacks.

There is a also the staggered start-up at T-5, which is different to the add-on.

It also looks to me like the FH does the initial pitch-over before it rolls out to "boosters level" attitude, difficult to tell from camera angles though.

And I still have no real idea of the actual boostback strategy - minimum energy return trajectory?(that's what I do) Minimum engine impulse to return trajectory? etc. so that impacts on how much fuel reserve you need.

And why put the ASDS where they did? Why not further down-range, so you don't need to kill ALL forward vel.?

I might have a go at implementing a side-booster throttle down for all or last part of the flight. Also, staggered start-up. And maybe do the pitch-over to roll-out sequence a bit different. Feel free to make your own tweaks to the code. Or fly it manually and see what works, etc.

Cheers,
Brian
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Old 02-09-2018, 04:40 PM   #26
BrianJ
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Quote:
Originally Posted by BrianJ View Post
 And why put the ASDS where they did? Why not further down-range, so you don't need to kill ALL forward vel.?
This image from the original webcast is useful. 30 sec post core sep. and the boostback burn is well under way, about half-way to the ASDS (so it is fairly far downrange for Spacex) Plenty to consider :-)
Click image for larger version

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Old 02-10-2018, 03:11 PM   #27
Longjap
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Thanks for this amazing add-on!
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Old 02-10-2018, 06:53 PM   #28
Flow
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Absolutely fantastic addon and I get more impressed every time I run the demo from last Tuesday.

Just having one slight problem and I'm not sure what I am doing wrong. When both boosters and the core land they sink a little into the ground/barge and lose their shadows:



Not sure if I've missed something or it's just another quirk of running in Linux.
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Old 02-10-2018, 09:34 PM   #29
BrianJ
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Thanks, hope you have some fun with it.
Quote:
Originally Posted by Flow View Post
 Just having one slight problem and I'm not sure what I am doing wrong. When both boosters and the core land they sink a little into the ground/barge and lose their shadows.
I don't think you're doing anything wrong.

The "sinking" problem I think is largely due to how the vessel's "Touchdown Points" are defined, specifically the stiffness and damping parameters. At least the boosters don't bounce around too much - best I could do.

The landing pads/ASDS are defined as vessels - Orbiter doesn't show shadows "on" them.

Cheers,
Brian
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Old 02-10-2018, 09:54 PM   #30
Flow
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Quote:
Originally Posted by BrianJ View Post
 I don't think you're doing anything wrong.

The "sinking" problem I think is largely due to how the vessel's "Touchdown Points" are defined, specifically the stiffness and damping parameters. At least the boosters don't bounce around too much - best I could do.

The landing pads/ASDS are defined as vessels - Orbiter doesn't show shadows "on" them.

Cheers,
Brian
That's great - thanks Brian.

Boosters don't bounce at all for me. It was the fact that everything else (and I mean everything) works so perfectly and replicates the actual launch so well that made me think I had something wrong.
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