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SpaceX Finally Lands Rocket on Barge


Waspie_Dwarf

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I'm watching the latest SpaceX Falcon 9 launch. The Dragon spacecraft has just successfully separated from the 2nd stage, but perhaps more spectacularly the first stage made a successful landing on a barge in the Atlantic.

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Good news. :tu:

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Absolutely amazing and just feet from the center in very rough seas. Honestly, to do this in those seas is amazing and makes this huge accomplishment even more impressive. A thrill to watch and the mission itself was absolutely flawless from start to finish. I was clapping and cheering along with the crowds in MC.

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Yes, an impressive and amazing accomplishment.

Plus there's the priceless name of the barge: Of Course I Still Love You. From the name of a spacecraft in an Iain M Banks novel.

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Plus there's the priceless name of the barge: Of Course I Still Love You. From the name of a spacecraft in an Iain M Banks novel.

Of Course I Still Love You is the second SpaceX barge. The first is now used for Pacific landings and is also named after a ship from an Iain M. Banks novel, Just Read the Instructions.

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Why in the sea?

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Why in the sea?

Because on many missions it won't have enough fuel on board, after completing it's mission, to return to land.

The landing requires fuel. On missions with a heavy payload or a high velocity at first stage separation is required (such as missions to launch geosynchronous orbit) the Falcon will use to much fuel to slow down, turn around and return to the launch site. A barge placed down range allows recovery of the first stage with less usage of fuel. Think of it as an aircraft carrier for rockets.

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Did the Falcon go into outer space or just the upper atmosphere? If from outer space, how did they keep the fuel cool during re-entry?

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Did the Falcon go into outer space or just the upper atmosphere? If from outer space, how did they keep the fuel cool during re-entry?

I want to know that answer, too.

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Did the Falcon go into outer space or just the upper atmosphere? If from outer space, how did they keep the fuel cool during re-entry?

The first thing we need to do is differentiate between reaching space and reaching orbit. Any object exceeding 100km (62 miles) in altitude has reached space. However to reach orbit you need to reach space and have a velocity of around 17,500 mph.

The next thing to understand is why re-entering spacecraft get hot. It is not because they are descending from space, it is because they are using the atmosphere to decelerate from orbital velocity. The kinetic energy of the spacecraft is converted into heat energy.

Now that those two points are made the answer will be clearer. I haven't been able to find exact figures, but it looks likely that the Falcon 9 first stage exceeds 100km altitude before descending, so it has reached space. However it is travelling at considerably below orbital velocity (it reaches around 6000mph I believe). Because it is not travelling so first their is considerably less kinetic energy involved (kinetic energy depends on the square of velocity, so if you go twice as fast you have, roughly speaking 4 times the energy). Less kinetic energy means less heat created during deceleration. That means no need for a heavy heat shield and not enough heat to boil off the precious fuel for landing.

I hope that makes sense.

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SpaceX’s Falcon 9 rocket returns to port

Riding into port aboard a floating platform before dawn, SpaceX’s Falcon 9 rocket booster arrived back at Cape Canaveral early Tuesday after sticking a historic landing at sea last week, kicking off a series of inspections and tests before engineers ready it for launch again.

A small crowd of SpaceX employees, news photographers and space enthusiasts welcomed the 15-story rocket booster to Port Canaveral around 2 a.m. EDT (0600 GMT) aboard a landing ship dubbed “Of Course I Still Love You,” a reference to giant planet-sized starships in science fiction novels by Iain Banks.

arrow3.gifRead more...

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Separation was at about 73km altitude and speed ~6500Km/h for this last launch. Momentum would carry it higher and I also think I have heard it reaches around 100km altitude.

They also flip the rocket around and fire three of the engines to slow it down with the boostback burn and the reentry burn before they hit the thicker lower parts of the atmosphere so I believe it will be going considerably slower than the speed at separation (which varies depending on type of orbit, payload weight ... ) when it reaches thick parts of the atmosphere.

Bringing a second stage back would require a heat shield as that does get up to orbital speeds. Adds too much weight so not worth doing for Falcon 9 but Musk still hopes to do it for larger rockets eg MCT.

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  • 3 weeks later...

You folks are going to love this!! 360° view of the first stage landing. Pan up with your cursor for the best view. Funny thing is that it so underwhelming as a real event that it is overwhelming emotionally. Pure, super creative science and engineering making the miraculous look common. Can't watch this just once. :tu:

Sorry but you'll have to click on the YouTube link to play with the 360° feature so I didn't embed.

Edited by Merc14
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They've done it again: http://www.abc.net.a...-launch/7391730

An unmanned SpaceX rocket has blasted off from Florida to put a communications satellite into orbit, with the launch vehicle's main-stage booster successfully landing on a floating platform at sea...

Before the launch, the company played down expectations for a successful return this time. Unlike the April mission, the rocket would have little fuel left over for engine burns to slow its descent after sending a half-tonne satellite into orbit.

I know that experts in the field have said that SpaceX are masters of publicity, but this is another pretty neat achievement.

= = = =

ETA: And dang it if they didn't land it inside the little circle!

Here's a much longer video - a bit over an hour long (

)

Useful stuff in the video: they include a ground track animation showing what the first and second stages are doing, and they explain what the rocket's doing as it heads out on a geosynchronous transfer orbit.

Interesting stuff: the first stage separated at an altitude of ~90 kilometres, and then coasted up to about 200 kilometres before coming back down, and apparently due to the nature of the mission (launching a satellite intended for geosynchronous orbit) the first stage came in at nearly twice the speed and with a lot less fuel available for the re-entry and landing burns than the last landing. And when the second stage relit to put the spacecraft onto its geosynchronous transfer orbit, the one minute burn lifted its speed by several thousand kilometres an hour, but its altitude increased by only about a dozen kilometres; it was only after the burn finished that the spacecraft really started to climb - simply a consequence of the orbital mechanics. It was also interesting to see the ground track animation change during the burn.

Funny stuff: an animation showing the spacecraft in geosynchronous orbit specified that the altitude of the orbit was "2.3 zillion kilometres". I'm not entirely sure that's correct...

Edited by Peter B
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Two is a row and this one was with little fuel left. Great job SpaceX

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Three Camera Angles | Falcon 9 First Stage Landing on Droneship

Three different views of last week's Falcon 9 first stage landing after sending JCSAT-14 satellite on to Geostationary Transfer Orbit. Hottest and fastest landing yet.

Credit: SpaceX

Source: SpaceX - YouTube Channel

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  • 3 weeks later...
On 06/05/2016 at 2:49 PM, Merc14 said:

Two is a row and this one was with little fuel left. Great job SpaceX

Make that three in a row, And another hot fast re-entry.

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First-stage landing | Onboard camera

Sped up video of the Falcon 9 first-stage landing during the THAICOM 8 mission on May 27, 2016. More info: http://www.spacex.com/news/2016/05/27/thaicom-8-mission-photos

Credit: SpaceX

Source: SpaceX You Tube Channel

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  • 3 weeks later...

Sadly SpaceX haven't been able to make it 4 in a row for the barge landing. The latest attempt crashed on the barge after one of the three engines used for landing suffered a thrust shortfall. 

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