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Fourth SpaceX Rocket Successfully Landed on A Drone Ship (theverge.com)

Posted by EditorDavid on from the reusable-rockets dept.

Saturday a SpaceX rocket completed the company's fourth successful landing at sea (watched by over 100,000 viewers on YouTube and Flickr). Saturday's landing means Elon Musk's company has now recovered more than half the rockets they've launched. An anonymous Slashdot reader quotes Saturday's report from The Verge: Tonight's landing was particularly challenging for SpaceX... The Falcon 9 had to carry its onboard satellite -- called JCSAT-16 -- into...a highly elliptical orbit that takes the satellite 20,000 miles out beyond Earth's surface. Getting to GTO requires a lot of speed and uses up a lot of fuel during take off, more so than getting to lower Earth orbit. That makes things difficult for the rocket landing afterward...there's less fuel leftover for the vehicle to reignite its engines and perform the necessary landing maneuvers.

CEO Elon Musk said the company is aiming to launch its first landed rocket sometime this fall...SpaceX's president, Gwynne Shotwell, estimates that reusing these landed Falcon 9 vehicles will lead to a 30 percent reduction in launch costs.
SpaceX named their drone ship "Of Course I Still Love You."

18 of 71 comments (clear)

  1. Pushing industry forward by kaalon · · Score: 3, Insightful

    Once SpaceX starts flying those "used" cores it will push the whole industry of space flight to the same level of reuse. We are going to see some great advances in engineering coming from all over the world as others start to catch up to SpaceX.

    1. Re: Pushing industry forward by Anonymous Coward · · Score: 3, Informative

      When a commercial company pays another commercial company to build a commercial satellite and pays to have that satellite launched by yet another commercial company it involves "funny money" and there is no economic benefit?

      All three of those commercial companies are profitable.

      Space-X raced to build a better launch system because there is substantial demand for launching satellites and by building a better launch system they are able to lower costs, charge less and increase demand.

    2. Re: Pushing industry forward by Gavagai80 · · Score: 3, Insightful

      The majority of SpaceX missions, including this one, have been for communications companies. It's safe to say they're seeing economic benefits.

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    3. Re: Pushing industry forward by DanielRavenNest · · Score: 3, Informative

      Space industry amounted to $335 billion last year. Most of that is commercial satellites, which are quite profitable. Do you think AT&T bought DirecTV so they could lose money?

  2. Less fuel. by fahrbot-bot · · Score: 2

    Getting to GTO requires a lot of speed and uses up a lot of fuel during take off, more so than getting to lower Earth orbit. That makes things difficult for the rocket landing afterward...there's less fuel leftover for the vehicle to reignite its engines and perform the necessary landing maneuvers.

    Does anyone know (or can point me to doc) about how the Falcons perform their descents. Is it powered / controlled the entire time, or parachute (or para-*somehing*) and just powered / controlled near the ground. I imagine the fuel requirements would be different.

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    It must have been something you assimilated. . . .
    1. Re: Less fuel. by Anonymous Coward · · Score: 5, Informative

      They slow down mostly through aerodynamic drag. No chute or similar device. The rockets only come on in the last 20 seconds or so to do the final braking.

      During reentry the first stage uses the rocket bells as a heat shield, and during the worst part of it they burn three engines to literally push the atmosphere out of the way "entry burn" to ease the heating until it gets down into the lower atmosphere where drag can slow it. For the ship landings, those are the only two burns, total less than 60 seconds with only 3/1 engines firing.

    2. Re:Less fuel. by queazocotal · · Score: 5, Informative

      The first stage and the second stage disconnect.
      The first stage flips around end to end, and makes a burn to kill most of its velocity.
      Then as it is entering the thicker parts of the atmosphere and it would be destroyed by drag and heating otherwise, rapidly slows at high G using the engines to around mach 1, and turns the engines off.
      It is at this time steering using fins attached to the top of the rocket.
      Once it gets ~10-20 seconds before landing, it lights an engine or three (details vary) and uses the thrust from these vectored in order to precisely land on the barge (along with the fins in the initial portion).

      http://www.spacex.com/sites/sp... is a nice diagram.

    3. Re:Less fuel. by Anonymous Coward · · Score: 4, Informative

      At the top of it's trajectory, it is out of the atmosphere. As it is about to hit the atmosphere, it burns with three engines for about 20 seconds so that hitting the atmosphere doesn't shred the rocket. It then lets atmospheric drag slow the rocket the rest of the way. It controls its direction with aerodynamic surfaces called grid fins during this phase. Finally, as it approaches the landing platform, it does a one engine burn so that its velocity hits zero at the precise moment when the legs touch down.

      The idea is to use the atmosphere to do most of the work slowing down the rocket. However, it needs to not be destroyed entering the atmosphere at velocities that are too high, nor be destroyed hitting the barge at terminal velocity. So engines are used in those two phases.

    4. Re:Less fuel. by Anonymous Coward · · Score: 5, Informative

      It has 4 (not 8) grid fins, small cold gas thrusters, and gimbaled engines, all controlling the rocket. They experimented with parachutes (dropping in the ocean instead of of landing on a ship) but never managed to slow down enough to make them work. It's hitting the outer atmosphere at about 2km/second! The has several problems, for example the rocket spinning up in the airflow centrifuging the remaining fuel to the side of the tank, so engines would stop, the steering find moving more than expected and running out of hydraulic fluid just before landing, etc. Even when practicing powered "landing" on the ocean surface before they had a landing ship, the did not even recover small parts because the rocket would be destroyed by waves and sink before they could get to it. The nearly empty first stage is also lighter than the minimum thrust of one of the 9 engines, so if the landing burn is started too early, it will be going back up before reaching zero altitude. Too late, and it will not have stopped before reaching zero altitude. There also has been a problem with one leg not locking into place and toppling over after landing. They now cool the RP-1 (kerosene) to -6C and the liquid oxygen to 50 degrees above absolute zero to make them denser, to get more performance out of the rocket without making the tanks bigger. This makes launch timing very critical since fuel needs to be pumped into the rocket very fast just before launch, without freezing pipes and quickly heads up while in the rocket where it can't be cooled and can't fit in the tank if warmed up. (boil-off only cools it to the boiling point of oxygen which is already to warm to fit in the tank). beginning 2017 SpaceX will start testing a version with 3 of these rockets connected, with all 3 cores landing separately, 2 on land, and the middle on on the ship in the ocean. Next month, SpaceX will present there plans for an even bigger rocket, that will fly to will fly to Mars, land on Mars, re-fuel, fly back to earth and land again, and also be fully reusable.

    5. Re:Less fuel. by Gavagai80 · · Score: 4, Insightful

      More importantly, parachutes have no precision and are subject to the wind.

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  3. Numbers... by cjameshuff · · Score: 5, Insightful

    The numbers in the summary are a bit ambiguous/confused:
    This was the *sixth* rocket they've landed. They've landed four on drone ships and two on land. That's nowhere near half the rockets they've launched (this was the 28th Falcon 9), but means just over half of their landing attempts (11 total) have succeeded.

    More importantly, of the last 7 landing attempts, there were only two failures, both due to simple lack of propellant margin due to the demands of those particular launches...there weren't any failures or control problems, they just ran out of propellant. The last actual hardware failure was flight 21, the Jason-3 launch, which actually landed fine, but had an earlier version of the legs which iced up and failed to lock in the extended position. So it's looking like reliability of future landings can be expected to be quite a bit better than 50%.

    All without any nets/cables/tubes/funnels/magnets/giant catcher's mitts.

    1. Re:Numbers... by AndreiK · · Score: 2

      He's correcting the editor's comments. "Saturday's landing means Elon Musk's company has now recovered more than half the rockets they've launched."

    2. Re:Numbers... by tomhath · · Score: 5, Funny

      This was the *sixth* rocket they've landed.

      Well, they landed all of them. Some landings were harder than others.

  4. Re:Waste of money. by ewibble · · Score: 3, Insightful

    Let me see? Space is quite big, unimaginably big in fact, and it is very likely there will be insane amounts resources out there on mostly dead planets, with no ecological harm done to anyone. Not to mention we can only examine a insignificant fraction of it in any detail, i.e. not through inferring information from specs of electromagnetic radiation.

    Yes we are a long way from exploring even our solar system in any great detail or harvesting any resources, however if we do not make a start, because we keep saying whats the immediate payback? We will never get there. We also are currently benefiting space technology such as communications, GPS, and the government being able to better spy on us, oops the last one might not be a benefit.

    As for people suffering, yes there are, but it isn't through lack of resources, it is through our greed, fear and hate. In the US 40% of food produced is waste. Obesity is a problem. Obesity kills 3 times as many people as malnutrition worldwide, (http://www.telegraph.co.uk/news/health/news/9742960/Obesity-killing-three-times-as-many-as-malnutrition.html), OK the malnourished are probably more likely to young children, but still we clearly have enough resources. There are 7 billion people in the world, if a few thousand concentrate on building rockets, it is not going stop the rest of us coming up with a solution. In order to fix suffering we need social/political solution not a scientific one.

  5. Just watch it happen by jfdavis668 · · Score: 3, Insightful

    This is the view from the rocket as it descends and lands: https://www.youtube.com/watch?...

  6. Re:Propellant or Hydraulic Fluid by DanielRavenNest · · Score: 2

    It was only once that they ran out of hydraulic fluid, they fixed that the next flight. Sticky engine gimbal caused another crash. The engine pivots to help steer it for landing, but it was moving too slowly, so they landed at an angle instead of vertical. Finally, one time a landing leg failed to lock. So it landed vertical, but then fell over. They have been learning by crashing, and generally don't have the same problem twice. Since expendable rockets *always* crash, flight testing the landing system this way doesn't cost much extra.

  7. Re:Propellant or Hydraulic Fluid by cjameshuff · · Score: 2

    The very first ASDS landing attempt ran out of hydraulic fluid for the grid fins, the engine gimbaling barely managing to get it to the barge...not upright and not at zero velocity.

    The next had a sticky valve...my understanding is it was actually for throttle. The control software would command throttle changes, but the valve wouldn't respond until the commanded change was big enough to break it loose, then it'd stick at the new position. The overall effect was that the throttle was lagging behind what the control system expected, which threw things into oscillation with the rocket always overcompensating for its previous errors, always too late to fix things.

    The third failure was the Jason-3 launch, which was the last launch of the Falcon 9 v1.1 (non-Full Thrust) with the first version of the legs, and took place in particularly heavy fog. The landing looked perfect, but one leg folded up afterward.

    The remaining two failures were on flights 22 and 26, both on ASDS landings from geosynchronous launches with little margin for landing. 22 wasn't expected to make it, 26 came within meters of doing so.

    There's probably still things to learn, but they seem out of the "getting it to work" stage and well into "making it work better" stage.

  8. Re:Waste of money. by KozmoStevnNaut · · Score: 2

    The greatest scientific advances of mankind have all come from the various space programs. No, they were not "found in space", they were developed right here on earth because the space programs created a need. Were it not for the space programs pushing science forward, many of the things you take for granted either wouldn't have been developed at all, or would have been developed much later. Stuff like velcro, food preservation, insulation, all kinds of stuff that you use every single day without even thinking about it.

    Go read, and learn: https://spinoff.nasa.gov/

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