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The video is pretty cool, but make sure to read the rest of the page. Most exciting of all is this last note: "We will attempt our next water landing on flight
by Crito 12y ago
The video is pretty cool, but make sure to read the rest of the page. Most exciting of all is this last note: "We will attempt our next water landing on flight 13 of Falcon 9, but with a low probability of success. Flights 14 and 15 will attempt to land on a solid surface with an improved probability of success."
That "solid surface" will presumably be a barge. Very exciting stuff.
Edit: The "loss of hull integrity" also answers a common question of "why not use parachutes". Even if they could land the stage softly enough with a reasonable amount of parachutes, the stage has trouble surviving tipping over in the ocean after landing. It needs to land and remain upright, but using parachutes you will often get some lateral velocity that would cause a tip-over. They need more control than parachutes can provide (and that's all ignoring the problems of salt water).
- toomuchtodo 12y ago> That "solid surface" will presumably be a barge. Very exciting stuff. I get nerd chills from the level of precision needed to bring a launch vehicle from hypersonic->subsonic speeds to a target that size, and land to reuse the vehicle.
- OrwellianChild 12y agoI'm impressed with the barge concept if only from the wave action the'd have to compensate for. Anyone know wave amplitude in the area they'd be landing in? That's a flat surface that's coming up to meet you or dipping away, making for a pretty heavy drop...
- toomuchtodo 12y agoIt's apparently called "Active Heave Compensation": http://www.boschrexroth-us.com/country_units/america/united_states/en/Company/Trade_Shows_and_Events/trade_shows/otc/a_downloads/press_releases/OTC2012_Primary-Active_Heave_Compensator.pdf http://www.boschrexroth-us.com/country_units/america/united_... It's used at sea for winches, but I'm sure platforms can compensate just as well with the proper force actuators and motion reference units.
- msandford 12y agoIt's actually much cheaper and easier to sink some anchors and winch the barge down a bit than to try and do active compensation. It's one thing to compensate a crane or a winch, it's another to compensate an entire vehicle. The anchor thing is one way that they handle off-shore drilling rigs. Another is to use a semi-submersible rig. What that means is that you fill the bottom half or 2/3 of the vessel with water making it much heavier. That changes the way it rides in the waves and can dampen the effects that a wave has substantially.
- toomuchtodo 12y agoMaybe use an old oil rig? Its legs would bolted to the seabed, which I would assume is sturdy enough.
- msandford 12y agoDepends on the rig. There are plenty of rigs in 5000' feet of water and I assure you that they are not mile-high building. They are semi-submersible. http://en.wikipedia.org/wiki/Semi-submersible http://en.wikipedia.org/wiki/Semi-submersible Oil rigs are really only for drilling, not for getting the oil out of the ground and into whatever container there is. So that means they move around all the time. Like every couple of weeks. What you're thinking of is called a jack up rig. They go in water up to a few hundred feet deep. Nothing over 1000 feet for sure. That's because the entire truss has to come out of the water when the barge is being moved from one location to the other. http://en.wikipedia.org/wiki/Jackup_rig http://en.wikipedia.org/wiki/Jackup_rig
- andygates 12y agoAn old oil rig has the right level of Bond-villain-ness about it. Gets my vote.
- mrchucklepants 12y agoThe Glomar Explorer, which was custom built by the CIA to raise a sunk russian nuclear submarine (https://en.wikipedia.org/wiki/USNS_Glomar_Explorer_(T-AG-193) https://en.wikipedia.org/wiki/USNS_Glomar_Explorer_(T-AG-193...),used heave compensation for the entire crane/rig that lifted the submarine from the sea floor.
- lotsofmangos 12y agoYou could use a SWATH style ship - http://en.wikipedia.org/wiki/Small_waterplane_area_twin_hull http://en.wikipedia.org/wiki/Small_waterplane_area_twin_hull They get very little wave loading due to having semi-submersible hulls, much like an oil rig.
- cryptoz 12y ago> common question of "why not use parachutes" My typical answer to this is to mention Mars and the very thin atmosphere. There's no point in SpaceX developing technology that they can't use on Mars.
- ceejayoz 12y agoMoon landings, too. While Musk has his sight set on Mars, I can't imagine he'd turn down the opportunity to beat NASA to a lunar return.
- speeq 12y agoYeah, he said: "Loop around the moon, possibly land on the moon - just to prove the capability" - http://www.youtube.com/watch?v=thKMqN-2E4s#t=50 http://www.youtube.com/watch?v=thKMqN-2E4s#t=50
- grecy 12y ago> "We will attempt our next water landing on flight 13 of Falcon 9, but with a low probability of success." I'm wondering why the next water landing has a low probability of success?
- andrewtbham 12y agoprobably because it's another water landing
- seanflyon 12y agoThe last 2 water landings have been successful.
- ceejayoz 12y agoMight be the flight path or payload limitations.
- davidrhunt 12y agoI believe it is because of this: > However, our next couple launches are for very high velocity geostationary satellite missions, which don’t allow enough residual propellant for landing. Based on the press release they plan on using Falcon Heavy for this type of launch in the future but it sounds like that project isn't ready for primetime yet.
- grecy 12y agoI took that statement to mean they can't even attempt a landing on the next couple of launches because there will not be enough residual propellant for landing. And then the next statement, I assume, refers to the next launches where they can attempt a landing. EDIT: my assumption is confirmed here http://en.wikipedia.org/wiki/List_of_Falcon_9_launches http://en.wikipedia.org/wiki/List_of_Falcon_9_launches Next up are flights 11 and 12, which can't be landed. Then 13 has the "low probability of success".
- greglindahl 12y ago
- washedup 12y agoIt's not about the rocket tipping over. The use of parachutes would require the loss of landing accruacy. They want to be able to guide the first stage to a specific location (like a launch pad), and parachutes would not allow them to do this.
- Crito 12y agoIt all factors in. SpaceX has performed grasshopper tests on windy days that would be a problem for a parachute landing. There is also the issue that parachutes sufficient to slow down the stage to a soft land-landing would be far too heavy.
- InclinedPlane 12y agoPowered landings mean precise, highly controlled landings. You land exactly where you want with minimum damage to the vehicle and you go out and put the stage on a truck so you can bring it inside and begin processing it for reuse in a matter of hours. Parachute landings mean you have a recovery zone, you need a recovery team, you need to find the rocket and bring it back. Whether landing in the ocean or land with a parachute there's a high probability of significant damage from impact and/or seawater intrusion. So now you have a huge amount of effort just to get the rocket back, then you have to clean it up. And the parachute landing likely means much lower chance of being able to fly even one additional flight, let alone many, unless you develop some sort of cushioning system like airbags, in which case you have to add that complexity, cost, and weight to the system. And all of that is aside from having to repack the parachutes for every flight. SpaceX is planning powered landings for the same reasons that commercial airlines do powered landings. It's safer, it's more controllable, it's a smoother operational experience. It just makes sense.
- Gravityloss 12y agoThere are precisely steerable parawings. They looked at recovering Saturn stages by glidinng back to Florida with a Rogallo wing.
- jccooper 12y agoParachutes also hit a lot harder. Powered landing you can touch down with ~0m/s. Parachutes you'd get something like 10 m/s (~22mph.) Not necessarily nice on your equipment.
- fixermark 12y agoNot particularly nice on your astronauts / cosmonauts / 赵里昱 either, though they have training, preparation, and (according to an interview with Cmdr. Hadfield awhile ago) specially-poured per-backside crash seats to ameliorate it somewhat.
- Crito 12y agoYup. The Soyuz landing capsule uses solid fuel retro-rockets at the very last second to slow down, but even then it is apparently a rather unpleasant bump.
- tomswartz07 12y agoWhat's interesting here is the difference: Soyuz uses a 'suicide burn' that releases a ton of delta-V in a short amount of time. From the video, it seems that Falcon uses a progressive burn as it approaches. They also mention that they can restart it up to 3 times in atmosphere.
- rspeed 12y agoThe third burn here is also a suicide burn. The first one is to change its path and the second is to prevent it from falling too fast.