Author Topic: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION  (Read 1041928 times)

Offline buraianto

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #2040 on: 03/08/2016 05:44 pm »
Is that a crater near the port aft corner?



Offline Thorny

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #2041 on: 03/08/2016 05:56 pm »
Is that a crater near the port aft corner?

Looks like a pile of debris to me.

Offline Jdeshetler

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #2042 on: 03/08/2016 06:08 pm »
Close up and speed up however since this video is 480P, not HD so the video quality is rather poor for close up.


Offline Kim Keller

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #2043 on: 03/08/2016 08:18 pm »
Small side note for launch visitors: Landings at LZ-1 are visible from that location (at Fishlip's) looking NE over the low white building seen in the video.

Heh, I like the certain dose of optimism, almost a matter-of-factness behind that statement after just 1 landing  ;D

I have no doubt there will be more.

Offline wolfpack

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #2044 on: 03/08/2016 09:05 pm »
Looks like a pile of debris to me.

What's the score now? Barge 5, Rocket 0?

Offline clegg78

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #2045 on: 03/08/2016 09:20 pm »
Looks like a pile of debris to me.

What's the score now? Barge 5, Rocket 0?

Yep,  someday they will succeed in sinking the barge, I have faith ;)
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Offline cscott

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #2046 on: 03/08/2016 10:21 pm »
I'd score that: Rocket 5, Barge 0.  Rockets are used to the flamey stuff.  Barges, not so much!

Offline Lar

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #2047 on: 03/08/2016 10:36 pm »
Barge is clearly winning by one metric, so far none of the damage has been more than "that'll buff right out", more or less[1]. Meanwhile rockets are reduced to piles of scrap, every time.

By another metric the rocket has only missed the barge twice now (once by hundreds of km, and it soft landed to boot... what a fail!....  and once by just a bit because the barge moved) so they're winning.

1 - not counting equipment.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline Space Ghost 1962

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #2048 on: 03/08/2016 10:59 pm »
Barge is clearly winning by one metric, so far none of the damage has been more than "that'll buff right out", more or less. Meanwhile rockets are reduced to piles of scrap, every time.
Build a barge like a rocket and it'll crumple/explode first time you bring it into port and tie up in heavy seas.

Build a rocket like a barge and no matter the propulsion it won't get off the ground ;)

Offline kevin-rf

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #2049 on: 03/08/2016 11:13 pm »
Barge is clearly winning by one metric, so far none of the damage has been more than "that'll buff right out", more or less. Meanwhile rockets are reduced to piles of scrap, every time.
Build a barge like a rocket and it'll crumple/explode first time you bring it into port and tie up in heavy seas.

Build a rocket like a barge and no matter the propulsion it won't get off the ground ;)
Well, at one point in time there was talk of Orion...
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Offline TrueBlueWitt

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #2050 on: 03/09/2016 12:43 am »

Anyone know how up to date these numbers on NY20 are?
http://www.n2yo.com/satellite/?s=41380

These look close to the insertion numbers.
Shouldn't SES 9 have already started it's transfer to GEO?
What's the typical checkout and insertion planning time for one of these prior to the first burn?

NORAD ID
: 41380
Int'l Code: 2016-013
Perigee: 335.6 km
Apogee: 41,633.9 km
Inclination: 27.9
Period: 750.5 minutes
Semi major axis: 27355 km
RCS: Unknown
Launch date: March 4, 2016
Source: United States (US)
« Last Edit: 03/09/2016 12:45 am by TrueBlueWitt »

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Anyone know how up to date these numbers on NY20 are?


They're not quite the same as the latest element set from Space-Track, but not far different either.
(Not going to post the full data, as it's a violation of the Space-Track user agreement).

Semi-major axis   27 356 km
Perigee x Apogee   328 x 41 627 km

Ad astra per aspirin ...

Offline kevin-rf

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #2052 on: 03/09/2016 01:40 am »
Could they be working on inclination first? Don't you get the most bang for the buck when apogee speed is lowest? As you raise the perigee it will go up
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Offline edkyle99

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #2053 on: 03/09/2016 01:54 am »
Looks like a pile of debris to me.

What's the score now? Barge 5, Rocket 0?
I think it is Barge 4, Rocket 0, since one attempt was waved off due to high seas shortly before the launch.  On all four of these attempts the stage has touched the barge.

 - Ed Kyle
« Last Edit: 03/09/2016 01:56 am by edkyle99 »

Offline OxCartMark

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #2054 on: 03/09/2016 03:00 am »
On all four of these attempts the stage has touched the barge.
Torched
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Offline dorkmo

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #2055 on: 03/09/2016 03:24 am »
can we assume the deck hole means that even if it were on target it was coming in too fast for a nominal landing?

Online Robotbeat

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #2056 on: 03/09/2016 04:01 am »
can we assume the deck hole means that even if it were on target it was coming in too fast for a nominal landing?
On target in what respect?

Coming in too fast doesn't mean it ran out of fuel. It may have meant the throttle-up happened too slowly so it didn't slow down in time. It could've meant drift in the (expected?) position of either the droneship or the rocket. With 3 engines blazing, 3 engines even at low-thrust is like, what, 5-7 gees? You'd have to be EXTREMELY close to on-target in the z-direction.

Let's say it's a = 50m/s^2 (with respect to the surface, not freefall), and the stage has to be within v=2m/s of zero in order to land safely.  How accurate do you have to be within the z-direction?

a = v^2/(2*d) becomes: 2*d*a = v^2 becomes d = v^2/(2*a) = (2m/s)^2/(2*50m/s^2) = 4 centimeters (!)

You have to be within 4 centimeters in the z-direction in order to stay within your landing velocity constraint when you're hoverslamming with 3 engines. If something doesn't throttle up fast enough or you start too early or late, you're toast. This isn't impossible, but it's DANG challenging.

A lot more leeway if you're doing a slight hoverslam, i.e. 2m/s^2 acceleration with respect to the ground (comparable to lift-off T/W ratio):

(2m/s)^2/(2*2m/s^2) = 1 meter. Much more realistic.

So they have to be precisely on-target in the vertical direction. At 50 gees, if you're off by just 4 meters in the vertical (due to lagging throttle or whatever), then you're going to be "landing" at 45 miles per hour... You could certainly punch a hole in steel if you have 20-25 tons of rocket at 45 mph...
« Last Edit: 03/09/2016 04:03 am by Robotbeat »
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Offline Semmel

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #2057 on: 03/09/2016 12:11 pm »
Plus, you only can correct for errors or uncertainties during the hoverslam burn if you do not burn with full thrust but have a target thrust setting well below 100% and well above the minimal thrust setting. If they didnt leave any margin, like put the target thrust at 95%, there is no way they could have corrected for any delayed startup of the engines. Even a single millisecond of delay during startup will cause a difference in landing height of about 300m/s /1000 = 0.3 m = 30cm. about 8 times the margin Robotbeat calculated! If there was any miscalculation or anything unexpected with the engines that makes them thrust below the target thrust level, the landing will be very hard. To me, the hard landing event is not surprising.

Offline cscott

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #2058 on: 03/09/2016 01:41 pm »
I don't think anyone's mentioned this yet but...
One reason SpaceX might be keen to get this three-engine landing burn to work is that their next-gen vehicle (MCT, Raptor first stage, Raptor second stage, whatever) might have a single engine with ~3x the thrust.  The more gees you can pull during the landing burn, the bigger your "smallest engine" can be.

Offline ugordan

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #2059 on: 03/09/2016 01:47 pm »
They were attempting a 3-engine landing out of necessity. They aren't trying to make an already difficult endeavor even more difficult. Repeatable landings on the ASDS with one engine first. Crawl before you walk.
« Last Edit: 03/09/2016 01:48 pm by ugordan »

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