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Space Technology

Longer Video Shows How Incredibly Close Falcon Stage Came To Successful Landing 342

Bruce Perens writes In the video here, the Falcon 9 first stage is shown landing with a tilt, and then a thruster keeps the rocket vertical on the barge for a few seconds before it quits, followed by Kabooom with obvious significant damage to the barge. It looks like this attempt was incredibly close to success. Given fixes, a successful first-stage recovery seems likely.
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Longer Video Shows How Incredibly Close Falcon Stage Came To Successful Landing

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  • Larger landing area (Score:5, Interesting)

    by Dan East ( 318230 ) on Wednesday April 15, 2015 @07:49PM (#49482181) Homepage Journal

    It sure seems that if a larger landing area was available, so that the rocket didn't have to lean so far to adjust to a very small target and thus could prioritize staying vertical, it would be able to land successfully. What's it going to take for NASA or the FAA or whatever to give them permission to land on, um, land.

    • by Bruce Perens ( 3872 ) <bruce@perens.com> on Wednesday April 15, 2015 @08:00PM (#49482245) Homepage Journal

      The ship is 300 feet long. It's a big rocket :-)

      The pad area they have at KSC is made for F9 Heavy, and multiple stages are supposed to land there, the neighbors are sensitive about having other rockets come down in their yard, and there's a big building you really don't want to hit :-) . So, they probably do need the precision. There was an odd tweet from Musk, later deleted, that said there was actually a process control problem and a phase delay.

      • by narf0708 ( 2751563 ) on Wednesday April 15, 2015 @08:30PM (#49482393)

        The pad area they have at KSC...

        The Kerbal Space Center?

      • by D.McG. ( 3986101 ) on Wednesday April 15, 2015 @09:46PM (#49482737)
        The full tweet was as follows:
        @elonmusk: @ID_AA_Carmack Looks like the issue was stiction in the biprop throttle valve, resulting in control system phase lag. Should be easy to fix.
        • by michelcolman ( 1208008 ) on Thursday April 16, 2015 @07:24AM (#49484145)

          Certainly looked that way to me. On the last oscillation before touchdown, with the tail end moving towards the left, the thrusters keep pointing the same way as the rocket goes through vertical and only change direction a little bit afterwards. This increased the amplitude of the oscillation rather than decreasing it. The thrusters should have changed direction before passing through vertical, not afterwards. I can't imagine them getting this wrong in software, it's basic dynamic stability 101, so a sticky valve seems likely.

          The rocket ended up landing almost perfectly vertical, but still rotating so the base was traveling sideways over the landing pad. No way they could stay upright like that.

      • by AmiMoJo ( 196126 ) *

        So can someone explain why they don't use a soft landing pad? Maybe an inflatable. It would have to be robust enough to survive the engine firing near it, but would allow the rocket to land on its side instead of having to stand upright.

        • by Isca ( 550291 )
          Think of it as a soda can. When the rocket is pressurized with all of it's fuel it's 100 tons and can withstand very heavy vertical forces. When most of it's fuel is gone it's like an aluminum can - still strong top to bottom but on the side very easy to dent and damage. 90% of the 10 tons of weight left is in the bottom 10% of the rocket so it's not as tipsy as you'd think.
    • by Megane ( 129182 )

      I had heard that a valve got stuck, causing the throttle and gymbaling to get out of sync. Now that I see the video, it looks like it was coming down really well until that last moment. It probably wanted to make a final course adjustment, but the rocket bits didn't work the way the computer bits expected them to. It even seemed a bit like the kind of crashes I would get in Gravitar [wikipedia.org] after getting a bit confused.

      A larger landing area would have just meant no bits to fall into the water after the kaboom.

      • by Bruce Perens ( 3872 ) <bruce@perens.com> on Wednesday April 15, 2015 @08:30PM (#49482389) Homepage Journal

        The tweet from Musk this morning used the word "sticktion", meaning static friction. And said it was the cause of a phase delay. And then the tweet got deleted.

        • ty for that.

        • So you're saying it wasn't hyper quantum sticktation of the flux attitude gimble during the multiphasic delay sequence?

          Damn, I should write science fiction. Or maybe I could work for the media. Both string scientific sounding words that mean absolutely nothing. :)

      • Re: (Score:3, Interesting)

        by farble1670 ( 803356 )

        Now that I see the video, it looks like it was coming down really well until that last moment.

        no way. for a gigantic fragile rocket it came in extremely hot. it was probably moving at 50+ MPH when reached 50 feet of the platform. it didn't slow down much until it was less than 10 feet away. it was also wobbling as it came in.

        as much as i'd like to say that was close, it wasn't.

        • by Bruce Perens ( 3872 ) <bruce@perens.com> on Wednesday April 15, 2015 @09:39PM (#49482703) Homepage Journal

          That would be hot for an aircraft, but it was the planned vertical speed profile for the rocket. The grid fins need speed to work and they are the main control surfaces. The cold gas thrusters don't have infinite gas behind them and the engine burns are very short.

        • by voidptr ( 609 ) on Wednesday April 15, 2015 @10:37PM (#49482911) Homepage Journal

          The F9 is intended to land with what they call a "Hover Slam" maneuver - the engines decelerate it to zero right above the surface in as little time as possible. The Merlin engines have a limited throttle range, and with the stage empty, just one engine firing at the lowest throttle setting has a thrust-to-weight ratio somewhere around 1.8, so it can't hover. It would decelerate to zero and then start to lift off again if the engine isn't shut off, you'd need a TWR of 1.0 to just counter gravity and make it hover.

        • by pushing-robot ( 1037830 ) on Wednesday April 15, 2015 @10:53PM (#49482973)

          Rockets are capable of incredible acceleration, especially when they're low on fuel and deprived of their payload. Under those conditions, the F9 first stage could easily go from 50MPH (~22m/s) to 0 in the space of a few meters.

          Also, you *want* to land fast, because for every second you spend in the air you lose another 10m/s of your limited delta-v (fuel), and the faster you're traveling the more aerodynamic control you have.

          Yes, I know all this from playing KSP.

          • by CrimsonAvenger ( 580665 ) on Thursday April 16, 2015 @07:23AM (#49484137)

            Rockets are capable of incredible acceleration, especially when they're low on fuel and deprived of their payload. Under those conditions, the F9 first stage could easily go from 50MPH (~22m/s) to 0 in the space of a few meters.

            Specifically, from a starting height of 50 feet, and a starting velocity of 50 mph downward, it would require a net acceleration of ~16.5 m/s^2 to come to a stop at ground level.

            Since a single (much less nine) Merlin engine can manage 654 kN thrust at sealevel, and a (nearly) empty Falcon 9 first stage masses under 20000 kg, a Falcon first stage is capable of >32.7 m/s^2 acceleration (assuming only one engine burning, of course). Which is more than plenty to allow it to come to a stop on the ground from the estimated speed/height of the OP....

    • It's not all politics.

      The first stage is a good distance downrange when it is done, as in; way out in the Atlantic when launching from Cape Canaveral.

      So, to fly it back to Kennedy would take a lot more fuel than letting it come down where it is. Not to mention the 'just in case' scenarios involving Titusville, the nearby I-95, etc.

      It will benefit Elon greatly if he can pull off landing it on his ocean barge. If he can do that, he can launch from anywhere in the world, with competitive fuel/payload ratios, a

      • by Bruce Perens ( 3872 ) <bruce@perens.com> on Wednesday April 15, 2015 @09:51PM (#49482759) Homepage Journal

        I was surprised by something in the re-entry profile. They use what they call "lift" from tilting the rocket body against the air stream to control horizontal motion. I call it "falling with style". So they can go back uprange some distance without an additional fuel expenditure.

        All of their communication so far has been that they can get back to the pad with the F9 or the two outer stages of the F9 Heavy. The center stage of F9 Heavy would probably need the barge.

        • by Sardaukar86 ( 850333 ) <cam@@@todaystlc...com> on Thursday April 16, 2015 @04:46AM (#49483713) Homepage

          Thanks Bruce, it's often in these little nuances that I catch myself staring into space, contemplating the sheer enormity of what has been achieved here. The skills of these people - to do what they're doing with the budget at their disposal - almost completely wrecks my personal 'scale of difficulty'. I thought I understood what they meant by 'It really IS rocket science,' but I'm really not even close.

          We really must be living in the future: small, agile, private enterprises taking the reigns of progress from state-level actors. NASA are by no means obsolete, if anything they've adapted rather well for a bureaucracy of their size and are continuing to do amazing science.

          Budgets might be tighter than we'd like but I can't help feeling like we're entering a golden era of space exploration and related technologies.

          Ooooh.. uh, does this make me a Space Nutter?

  • One would think lifting off with all that fuel needed for the landing is inefficient compared to a splashdown parachute recovery like the shuttle's boosters. And the damage caused by landing on water with parachutes has got to be less than the explosions from the landings on the barges.

    • by DaHat ( 247651 ) on Wednesday April 15, 2015 @07:56PM (#49482209) Homepage

      And the damage caused by landing on water with parachutes has got to be less than the explosions from the landings on the barges.

      Probably not when they figure out how to land on the barge without exploding... at that point the damage from hitting the water and amount of cleaning & service required to be read for launch will be much more.

    • by Bruce Perens ( 3872 ) <bruce@perens.com> on Wednesday April 15, 2015 @08:04PM (#49482263) Homepage Journal

      They have talked about refueling on the barge and flying the booster to land! That's really difficult to do after a salt-water dip :-)

    • by dpilot ( 134227 )

      I've heard this point before, with the obvious comparison of Shuttle wings. The counter is that wings are absolutely dead weight on liftoff, plus you've added an entirely new structural mode to the airframe. It has to have the correct structural strength for both vertical ascent and horizontal landing. Both wings and bimodal structure add weight.

      Landing the F9 on it's tail, it's practically empty, a fraction of it's initial weight. I'd be interested in seeing the math between F9 and Shuttle, but I suspe

      • by AaronW ( 33736 ) on Wednesday April 15, 2015 @08:38PM (#49482429) Homepage

        A couple of months ago I was having a discussion with a fellow from Space X who designs the hydraulic systems and we spoke about a number of issues. This was right after the failed landing due to it running out of hydraulic fluid. I asked about how reusable the engines are and he said that they run test burns lasting hours. The launch is only a few minutes. According to what he said, it should just be a simple matter of refueling and adding more hydraulic fluid and probably some other simple things without having to do a major overhaul. The engines are very reliable.

        I asked about why they don't reuse the hydraulic fluid and he said that it was cheaper and lighter to not reuse it. He also said that they knew it could run out and that the next version would have more.

        • It's lighter to not reuse the hydraulic fluid.

          It's an open loop system with pressurized gas pushing the fluid out and then it's dumped in the air. Pumps and whatever powers them have weight.

          Remember that big fuel-required multiplier in getting any weight at all to 78 miles height and suborbital speed.

    • Every time there's a thread about this, someone says the same stupid thing you're saying, and it's still wrong.

      There's a huge difference in power requirement in getting a fully fuelled and loaded rocket up in the sky, and slowing the descent of a nearly-empty, lightweight fuel tank. You need very little fuel to accomplish the latter. Don't forget that parachutes have mass too and it's very hard to make a controlled descent with them (especially if you need to carry the rocket a significant distance). All in

    • They have fuel to spare on board anyway (so they can launch with eight of nine engines working)

      • If one engine fails, the fuel cross feeds from that fuel tank into the other engines. I could be wrong, but I do not believe each fuel tank automatically includes more fuel to burn that particular engine for longer just in a case another engine fails. That would be an awful lot of redundant weight for very little benefit. Being able to cross feed the fuel from a broken engine's tank into the others would make far more sense then constantly launching with a bunch of dead weight that is not going to be used.

        • The required longer burn to make up for a shut down engine does use extra fuel. It also changes the orbital injection point.

    • by halltk1983 ( 855209 ) <halltk1983@yahoo.com> on Wednesday April 15, 2015 @08:51PM (#49482497) Homepage Journal
      Hard to splash down on the moon, Mars, asteroids and just about everywhere else we want to go. We'll have to get it right eventually, might as be now. Bonus benefit: cheaper than overhauling the engines every time. You'd think with them doing this at a third the cost of anyone else, WITH A PROFIT, that people would understand that they know what they're doing. Yes, there will be early failures, but this doesn't add that much cost, especially considering long term payoff.
    • by Dunbal ( 464142 ) *
      Consider it deducted from the amount of payload/second stage you can carry. But if your first stage is engineered to be more than enough for what you need as payload anyway (ie it's already cost effective) you might as well try to recover the cost of it with a soft powered landing and make MORE profit.
    • by bill_mcgonigle ( 4333 ) * on Wednesday April 15, 2015 @10:41PM (#49482923) Homepage Journal

      fuel needed for the landing is inefficient compared to a splashdown parachute recovery

      The barge/ocean is just a temporary measure. The vision [youtube.com] is twenty rockets launching a day and returning to the launch site to prep for the next launch.

      There were about 120 rocket launches last year. SpaceX's mission statement is to reduce the cost of launches by 100x, and utilization rates go up as costs fall, so it's not just 100x more launches - twenty a day is probably very conservative if they hit their price targets.

      Queue the folks who can't imagine what anybody would do with more than 640 launches a year.

    • by AJWM ( 19027 )

      One would think that if they didn't know that the shuttle's boosters are made of inch-or-more-thick steel, while the Falcon's tanks are millimeter thick aluminum-lithium. And that the booster splashdown still tended to leave the boosters slightly out of round (which contributed to the problem Challenger had).

      The extra fuel almost certainly weighs less than the necessary parachutes would.

  • by MichaelSmith ( 789609 ) on Wednesday April 15, 2015 @07:57PM (#49482215) Homepage Journal

    The falcon can't throttle down enough to hover before landing so it has to approach the pad at high speed, and high acceleration. While doing this it has to rotate the entire vehicle to control lateral movement. It has to coordinate lateral and vertical acceleration to achieve near zero in all three axes at touchdown, with only one chance to get it right.

    I doubt this can be done without extra thrusters for fine control over velocity and position.

    • But we've seen Grasshopper and Falcon R9 position properly on land. Nobody's told us what the maximum wind was in those tests.

      Musk alluded to a process control issue this morning and then deleted the tweet. It will take time to find out what the deal is.

      Merlin 1D can throttle to 70% and the old 1C could go to 60%. Perhaps there's room for deeper throttling. I would expect that they'd try that before adding a new system and its weight.

      • In those tests, both Grasshopper and R9 were coming down much more slowly. But it appeared they could come down slowly. Pretty close to hover.

      • by stox ( 131684 )

        I suspect they just need to tweak some PID loops at this point. I don't think throttling is an issue. Unlike the Lunar Lander, the target of the landing is a concrete point. Hovering should not be needed. Drop it on the spot, done.

      • >Perhaps there's room for deeper throttling.

        Indeed. It might even make sense to use a different design for the central engine if deeper throttling interferes with efficiency or maximum thrust. Of course if they can get the control systems working properly with the standard engines that would be the optimal solution.

    • Came here looking for the armchair rocket scientists, left unsurprised but disappointed. Dunning-Kruger lives.

  • Try HD mode (Score:5, Informative)

    by Bruce Perens ( 3872 ) <bruce@perens.com> on Wednesday April 15, 2015 @07:57PM (#49482217) Homepage Journal

    You can see a lot more if you go to 1080 HD and full screen. There's some large piece of equipment, perhaps the motor head for one of the barge's corner thrusters, being thrust off of the barge in flames.

    It looks like they'll need to do a lot of work on the barge. The support ship Go Quest and the tug Elsbeth III seem to be back in Jacksonville according to vessel tracking sites. There is a Carnival cruise ship that parks next to the barge's dock every 4 days, so we will probably see photos from its bow netcam if we don't see them otherwise.

    Oh, check out this newscast [youtube.com]. At 2:43, CBS News uses a sequence a SpaceX fan produced with Kerbal Space Program to illustrate how the landing is supposed to work.

  • Why do it the hardest and most fuel inefficient way imaginable. Split seam the fuel tank, then swing out and rotate the elements and create a massive autogyro. Sure you have to be careful with the seal of the seams in the tank and wind could be a problem requiring on the fly change of landing zone but overall a whole lot less additional fuel required and even a bad landing will still be soft by comparison.

    • by Bruce Perens ( 3872 ) <bruce@perens.com> on Wednesday April 15, 2015 @08:06PM (#49482279) Homepage Journal

      Split seam the fuel tank, then swing out and rotate the elements and create a massive autogyro.

      They have a job for you in the ULA marketing department.

    • Re:The Hard Way (Score:5, Insightful)

      by gstoddart ( 321705 ) on Wednesday April 15, 2015 @08:09PM (#49482293) Homepage

      Split seam the fuel tank, then swing out and rotate the elements and create a massive autogyro

      Why am I not convinced your way sounds like the "easy way"?

      I can't event think of the mechanical stresses involved in opening this thing up to spin it around.

      In fact, it sounds outright crazy.

      And that's before we start considering a fuel tank designed to open up. Because, what could possibly go wrong there?

      • What's the worst thing that could happen? The fuel tank leaks and explodes shortly after takeoff, showering the ground nearby with burning wreckage, or leaking rocket fuel higher up in the atmosphere, without igniting it, coating everything around with toxic, un-burnt fuel, ready to set half a state on fire?

    • Who cares about the fuel efficiency of landing? A Falcon 9 launch costs about 50-56 million dollars - the fuel itself only costs about 200,000, or 0.4% of the launch costs. The cost of increasing the fuel load by a few percent to allow for landing barely even qualifies as a rounding error.

      Meanwhile, all the extra mechanisms needed to turn a simple high-strength fuel tank into a transformer is almost certainly going to increase the mass so much that you'd need far more fuel to get the thing to the second-s

  • by cruff ( 171569 ) on Wednesday April 15, 2015 @08:27PM (#49482373) Homepage
    Looking at the video, it appears the booster does not come close to ever having anywhere near a true vertical orientation, and this attempt was not, in fact, "incredibly close to success". Granted, it came closer than ever in history to achieving the goal, but the thruster appeared to not have enough thrust to push the rocket to a vertical position once the booster touched down on the barge. I hope Space-X has a successful next test! The world needs a dose of rockets landing on large flames in the style of those old campy movies.
    • I was shocked at how abrupt and extreme the pitch changes were. I think so long as it needs such gross adjustments so close to landing, landings will be unreliable with a significant chance of failure. It is not at all like the tidy landings made by the Grasshopper test vehicle.

      Two engineering changes which could make a big difference are lower minimum thrust (so it can approach the landing with lower acceleration) or lateral control rockets (RCS) at the top of the stage.

      • by Michael Woodhams ( 112247 ) on Wednesday April 15, 2015 @10:31PM (#49482883) Journal

        Someone in the Youtube comments says "The flight profile veers the booster off to the side on purpose so the exhaust from the final burn isn't directed at the barge where it could do damage"

        If this was a planned manoeuvre, I'm much happier. Can anyone confirm this statement?

        • by Henriok ( 6762 )
          If this is true, I haven't seen any of their test vehicles doing this in try outs. They all hovered very controlled, and descends slowly and steadily. This landing was from what I could see the definition of "out of control", trying to regain control and desperately trying to complete the mission.
      • It *has* RCS at the top of the stage. One of them fires for a good 4-5 seconds trying to hold the stage upright after the touchdown (it failed, obviously). Were you watching in really low quality or something?

    • by Anonymous Coward on Wednesday April 15, 2015 @09:56PM (#49482775)

      They hit a barge in the middle of the ocean with a gigantic rocket that was nearing orbital velocity. I think we need to cut them some slack :)

  • by l0ungeb0y ( 442022 ) on Wednesday April 15, 2015 @08:33PM (#49482405) Homepage Journal
    With Horseshoes and Hand Grenades. We've seen what "close" gets us with rocketry, and it's not pretty.
    • In combat it's called "walking your fire". Sure, the first 30 rounds aren't close enough to matter in themselves, but they give you enough information so that the 31st round hits home.

    • I must confess that most of my programs have bugs the first time I write them. I don't start over from zero when that happens.

      The Wright Flier didn't get to San Francisco, but it started the path that led there. Actually touching down on the planned point, at the planned vertical velocity, is pretty good. They'll fix the rest.

  • by PeteJanda ( 1481299 ) on Wednesday April 15, 2015 @08:38PM (#49482425)
    Kindergarten Question for SpaceX: why not simply put the equivalent of a safety net on the barge, cut the rocket's engines at an altitude of ~10m and let the rocket fall safely into the net? Less fuel, less complexity and less cost.
    • by Overzeetop ( 214511 ) on Wednesday April 15, 2015 @08:48PM (#49482473) Journal

      The forces required are enormous, and even 10m away the rocket thrust would toast most materials. It still has to be caught in a specific orientation to minimize stresses, which means stabilization. As for stopping further, a 10m fall would probably far outstrip the capacity of the structure. (For comparison, more heavily built high power / amateur rockets are designed for touch down forces equivalent to a drop of about 2 meters). The fuel difference is near zero since the full motion of the rocket must be arrested prior to that final "fall".

      It also means that the rockets could never land on an arbitrary location, which would be a future goal. Solving it now is a Good Thing (TM).

    • While I think your idea would still leave some damage ... I'm thinking similar ... something like a safety loops that snare it at multiple heights once it touches the barge.

  • Watching this got me curious if there were any radical ideas that might help something like this work better. What if you fired a bunch of harpoons that latched on to the rocket as it approached to try to help guide it down? Although they would need to be on some kind of spinning track since the rocket could spin a lot, and any latches added to the rocket would almost certainly mess with the aerodynamics of it. So probably not that good of an idea. I dunno. I feel like there is room for improvement som
    • To expand on this just a bit: I feel like the landing platform itself should somehow be helping the rocket land. It is like when you toss a ball up and catch it. If you just leave your hand at a certain height, the ball smacks into it real hard. But if you move your hand down with the ball as you catch it you provide a much smoother deceleration and it lands more softly. Obviously finding equipment and mechanisms that could assist a rocket will be hard though (massive ass weight and extremely hot fuel)
      • Speed and distance are the big problems. Rockets can do both. Things that are tied to ships or the ground have trouble keeping up with the rocket.

      • by Immerman ( 2627577 ) on Wednesday April 15, 2015 @09:32PM (#49482673)

        I suppose magnetic/sticky harpoons might help (you don't want to damage it after all), sort of like guy-lines on an airship. I don't know about a shock-absorbing landing pad (your catcher's mitt) though - in the moments before landing the backwash would be subjecting it to forces exceeding those of the weight of the rocket itself - probably at least as difficult to tune any "give" to occur at the proper moment as i is to land the sucker in the first place.

        Plus, as others have mentioned, Musk seems to have his eye on Mars. Landing a colony ship can probably only be done by rocket, and there won't be any special landing pads on Mars. Plus, for more terrestrial concerns, if he can master landing on a simple barge, he can land pretty much anywhere, which dramatically improves the value of his rocket design onte international market: any bit of flat, stable land is a potential cheap spaceport that his rockets can service.

  • A bit of rotation should help to keep the thing upright. The gases being pushed into the silo will be forced towards the walls on their way back out and help center the rocket as it enters the silo. A funnel-shaped silo is easy to hit and provides a soft cushion as the pressure of the backscattered gas increases as the rocket descends into it. Finally, a rotating platform at the bottom needs to be synchronized to the rocket's own rotation. Good Thing I don't have the billions it would take to see my brillia
  • - Musk has commented that the issue has been diagnosed as some stiction that was causing a lag between computer commands getting carried out. They believe the issue will be straightforward to fix. - Musk's claim is that the barge didn't sustain any serious damage.
    • New product (Score:4, Interesting)

      by SuperKendall ( 25149 ) on Wednesday April 15, 2015 @09:25PM (#49482639)

      Musk's claim is that the barge didn't sustain any serious damage.

      Screw self-landing boosters. What I want is a house made out of whatever the barge is made of, easily shrugging off what are essentially two direct rocket hits complete with massive explosion.

  • "Droneship is fine. No hull breach and repairs are minor. Impact overpressure is closer to a fast fire than an explosion."â"Elon Musk
    • Only a billionaire can say that damage from an exploding rocket booster landing on top of something is 'minor'.

  • by sexconker ( 1179573 ) on Wednesday April 15, 2015 @08:50PM (#49482487)

    Build a large funnel, or infundibulum, on the barge.
    All you have to do is hit the wide top of the funnel at a non-clusterfuck angle.
    Then you let the structure of the funnel contain and guide the rocket as it continues on down.
    If you fuck up badly, you won't lose everything. And if you do very well for 98% of the landing but tip toward the end, damage from impacting the walls of the vertically will be incidental and minor as the rocket is still thrusting to lower its velocity (and thus the force of the impact).
    And if you do it successfully the funnel isn't touched.

    Alternatively, do the same but instead of a solid funnel, use closing arms so you can actively catch and assist the rocket if need be, or drop the arms and let the rocket fall into the ocean if you have to abort.

    You could also put 8 electromagnets in a circle with the target in the center. If the rocket leans north west, increase power to the southeast magnet and decrease power to the northwest magnet.

    Another idea would be to have a guy with a long stick on the barge ready to nudge it just a bit if it starts to tip.

  • by YrWrstNtmr ( 564987 ) on Wednesday April 15, 2015 @09:09PM (#49482573)
    You need three conditions:
    1. Hit the target location
    2. Minimal vertical velocity
    3. Vertical orientation.

    They met #1. It was coming in tilted (for varying amounts of tilt), and way too fast.
    • They planned the fast approach. Consider that the main control surfaces are the grid fins. They don't work at slow speeds. It's all about landing with the minimum use of weight (thus fuel).

    • They got #2 as well, it was just that #3 wasn't quite there.

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