Frida Space Posted December 22, 2015 Share Posted December 22, 2015 Via Emily Lakdawalla (GIF) Link to comment Share on other sites More sharing options...
Red Fang Posted December 22, 2015 Share Posted December 22, 2015 That landing was magnificently uneventful. Great job SpaceX! Link to comment Share on other sites More sharing options...
Shpaget Posted December 22, 2015 Share Posted December 22, 2015 1 hour ago, PB666 said: Can i add that they landing trajectory doesn't make much sense, if you have east bound momemtum at peak altitude why reverse it to land with west bound momentum? dV in the x,y needs to be added twice then stppoed twice, this is 3 additional dV just to land (although the primary occurs after stage 2 sep), if they had chosen a pad and a landing site at different locals they wouldn'.t have had to carry this extra fuel and they have more payload cap. Most likely due to simpler FAA approval process. By launching and landing at the same place you only need to reserve one block of an already crowded airspace. Landing on a separate location needs another empty block of airspace. Also, that would require the launch to happen from some place to the west. Which place would that be? Furthermore, once the second stage separates, the low mass of the nearly empty first stage means that the necessary dv requires only a fraction of the fuel compared to what it takes to launch it. The final maneuverer, the one to stop the westward motion, likely requires even less fuel since it can be done using aerodynamics of the booster and the grid fins. Link to comment Share on other sites More sharing options...
Martian Music Posted December 22, 2015 Share Posted December 22, 2015 Feels bad to be late but.. holy hell! They really did it! Space X style, efficient and smooth. This and the NASA budget announcement totally made my day. Space science IS moving forward. #astronomy4life Link to comment Share on other sites More sharing options...
Luis Posted December 22, 2015 Share Posted December 22, 2015 1 hour ago, PB666 said: Can i add that they landing trajectory doesn't make much sense, if you have east bound momemtum at peak altitude why reverse it to land with west bound momentum? dV in the x,y needs to be added twice then stppoed twice, this is 3 additional dV just to land (although the primary occurs after stage 2 sep), if they had chosen a pad and a landing site at different locals they wouldn'.t have had to carry this extra fuel and they have more payload cap. It launches eastward from the coast of Florida, so it's flying out over the Atlantic ocean. At stage separation it is less than 100km down range. The next bit of land to the west is still thousands of km away, which would require a lot more dV to reach than simply turning around. The return trajectory is also pretty vertical. The reason it has to cancel out some westward velocity at the last minute is that it deliberately aims for the sea, in case the engines fail to relight for the final braking burn. Link to comment Share on other sites More sharing options...
Martian Music Posted December 22, 2015 Share Posted December 22, 2015 2 hours ago, Albert VDS said: This thread needs some celebratory music: https://youtu.be/XYUDQh2RSbw Hahaha that was epic, how'd you find that ;p Link to comment Share on other sites More sharing options...
rudi1291 Posted December 22, 2015 Share Posted December 22, 2015 Does anyone know how much extra fuel they had for boostback and landing? The rocket doesn´t look that much bigger as for example an Atlas V or Soyuz... Link to comment Share on other sites More sharing options...
J.Random Posted December 22, 2015 Share Posted December 22, 2015 That was one beautiful landing and a job well done. Congratulations! Bezos, on the other hand, just begs for a Pulp Fiction quote as a response. Link to comment Share on other sites More sharing options...
Nibb31 Posted December 22, 2015 Share Posted December 22, 2015 1 hour ago, PB666 said: Well if they wanted to show off they could have landed inside of the VAB. Can i add that they landing trajectory doesn't make much sense, if you have east bound momemtum at peak altitude why reverse it to land with west bound momentum? dV in the x,y needs to be added twice then stppoed twice, this is 3 additional dV just to land (although the primary occurs after stage 2 sep), if they had chosen a pad and a landing site at different locals they wouldn'.t have had to carry this extra fuel and they have more payload cap. Not sure what you mean. If they don't reverse their horizontal velocity, they land in the ocean. The whole point of the exercice is to achieve RTLS, not a barge landing. There is a dog-leg burn at the end so that if the burn fails, it crashes into the sea and doesn't destroy the pad. http://i.imgur.com/D9BdO86.png Link to comment Share on other sites More sharing options...
Nibb31 Posted December 22, 2015 Share Posted December 22, 2015 1 minute ago, rudi1291 said: Does anyone know how much extra fuel they had for boostback and landing? The rocket doesn´t look that much bigger as for example an Atlas V or Soyuz... I think it's something like 10%. The F9 is actually quite a bit bigger than Soyuz (which is a different class of launcher) and slightly shorter than Atlas V. You just sacrifice some payload fraction to compensate for the extra fuel and trajectory loss. What F9 has that the others don't is the ability to throttle down (each individual engine, plus using only 1 out of engines). That's the key capability for pulling off a vertical landing. Link to comment Share on other sites More sharing options...
SomeGuy123 Posted December 22, 2015 Share Posted December 22, 2015 Question about the super chilled propellant. Water boils at 100 C. So if the rocket were full of water at 100 C, some of the water would be in the vapor phase, creating this bubble of steam at the top of the propellant tank. Since the propellant tanks on a rocket are made as thin and light as possible, the tank can withstand very little internal pressure, so you have to continually vent the bubble of steam and you cannot pressurize the tank enough to force the steam back into the vapor phase. But if you loaded the rocket with 50 C "super chilled" water, there wouldn't be any steam phase, and you could fill the tank to the brim. A more full tank means you effectively get more mileage out of the dead weight metal you have to make your tanks out of, raising your payload fraction. Is this what they are doing, except with liquid oxygen? Link to comment Share on other sites More sharing options...
softweir Posted December 22, 2015 Share Posted December 22, 2015 37 minutes ago, SomeGuy123 said: ... Is this what they are doing, except with liquid oxygen? Exactly. Also, it makes the filling process simpler, since the LOX is so cold that it chills the tank down to below the boiling point of LOX almost as soon as they start pumping it in. There *is* a short burst of evaporation off the "hot" walls of the tank when the LOX starts to go in, but after that very little. Link to comment Share on other sites More sharing options...
razark Posted December 22, 2015 Share Posted December 22, 2015 5 hours ago, Jeanjvs said: http://www.theverge.com/2015/12/21/10642028/spacex-falcon-9-landing-elon-musk-wont-fly Ah. Thanks. I was wondering if they'd be going for a "look how quickly we can get it ready again" demonstration. Link to comment Share on other sites More sharing options...
SomeGuy123 Posted December 22, 2015 Share Posted December 22, 2015 14 minutes ago, softweir said: Exactly. Also, it makes the filling process simpler, since the LOX is so cold that it chills the tank down to below the boiling point of LOX almost as soon as they start pumping it in. There *is* a short burst of evaporation off the "hot" walls of the tank when the LOX starts to go in, but after that very little. So the catch is they have to fire up the rocket before the LOX in the tank warms to the boiling point of LOX. Once it gets that hot, any more LOX you add will just warm up to that temperature as well and you have to continually vent the lox vapor..but... OH...the BUBBLES. See, if there's a vent at the top of the tank, you can just keep adding LOX to keep the "fluid level" a millimeter below the top. But the fluid will also be full of bubbles of gas, in the process of rising to the top like bubbles of steam do in water. Might be slower in LOX, dunno, I haven't handled it but it's a lot colder albeit with weaker intermolecular bonds. Anyways, you cannot get rid of the bubbles so you permanently lose tank capacity. So the drawbacks of this method is you have to fill the rocket really fast, you need to launch soon after filling, and if you have a launch hold, you have to pump out the LOX tanks back into a holding tank in your cryogenic tank farm and rechill it back to this supercooled temperature. Link to comment Share on other sites More sharing options...
Rune Posted December 22, 2015 Share Posted December 22, 2015 1 hour ago, Nibb31 said: I think it's something like 10%. The F9 is actually quite a bit bigger than Soyuz (which is a different class of launcher) and slightly shorter than Atlas V. You just sacrifice some payload fraction to compensate for the extra fuel and trajectory loss. What F9 has that the others don't is the ability to throttle down (each individual engine, plus using only 1 out of engines). That's the key capability for pulling off a vertical landing. Actually, it also has an engine capable of multiple relights, even against a supersonic airstream. Merlin 1D is one heck of an engine! That, plus the nitrogen RCS system, the landing gear, the grid fins, the amazing landing algorithm (indicating a guiding package on the first stage), TPS on the skin of the booster, larger structural margins... Rune. But yeah, the throttling capability is key. Link to comment Share on other sites More sharing options...
Nibb31 Posted December 22, 2015 Share Posted December 22, 2015 (edited) Congratulations, you've just figured out the principle of cryo propellants. The point is that by lowering temperature, you raise density, which means that you can build smaller (and therefore lighter) tanks for the same number of molecules. Oxygen and hydrogen take up less space when they are liquid than when they are gaseous but they have to be chilled a lot to become liquid. And yes, they do need active cooling when they are on the pad, and they do have to detank when a launch is scrubbed, and tanks have a limited number of tanking cycles. This is also why they use foam insulation on cryo tanks, and why you can't easily keep cryo fuels on orbit, and long duration missions require either storable propellants or active cryo equipment. Edited December 22, 2015 by Nibb31 Link to comment Share on other sites More sharing options...
Albert VDS Posted December 22, 2015 Share Posted December 22, 2015 2 hours ago, Martian Music said: Hahaha that was epic, how'd you find that ;p It's was create by Cinesaurus and released right after CRS-6. Link to comment Share on other sites More sharing options...
PB666 Posted December 22, 2015 Share Posted December 22, 2015 3 hours ago, Shpaget said: Most likely due to simpler FAA approval process. By launching and landing at the same place you only need to reserve one block of an already crowded airspace. Landing on a separate location needs another empty block of airspace. Also, that would require the launch to happen from some place to the west. Which place would that be? Furthermore, once the second stage separates, the low mass of the nearly empty first stage means that the necessary dv requires only a fraction of the fuel compared to what it takes to launch it. The final maneuverer, the one to stop the westward motion, likely requires even less fuel since it can be done using aerodynamics of the booster and the grid fins. How about ellington field? Not saying that just because its 12 miles away either, :^). Link to comment Share on other sites More sharing options...
J.Random Posted December 22, 2015 Share Posted December 22, 2015 Aren't they building a launch facility on another side of the gulf, near mexican border? Link to comment Share on other sites More sharing options...
Nibb31 Posted December 22, 2015 Share Posted December 22, 2015 (edited) Yes, in Boca Chica, Texas. That's still 1675 km from their landing site at Cape Canaveral, which is a bit of a stretch for coming straight down. Even for Boca Chica launches, RTLS will still be easier than flying to Florida. Rocket stages typically splashdown 200 to 400 km from their launch site. Edited December 22, 2015 by Nibb31 Link to comment Share on other sites More sharing options...
Kerbart Posted December 22, 2015 Share Posted December 22, 2015 8 hours ago, CatastrophicFailure said: Scorch marks? Crisp? As in "burned to a..." Badum-tish. Right? Right? No? I'll show myself out... IT may simply be case of "Ok we've got the engine in vacuum with nothing much else to do with it, let's test the re-light simply because we can at zero additional cost. Also, because SCIENCE!" That or they had a “Test the Merlin engine while in Earth Orbit” contract. Link to comment Share on other sites More sharing options...
mark7 Posted December 22, 2015 Share Posted December 22, 2015 9 minutes ago, Kerbart said: That or they had a “Test the Merlin engine while in Earth Orbit” contract. hhh only the career guys will understand what u mean! I guess here are the conditions: Activity the engine through staging above 600km. DO NOT hit ISS or ANY OTHER SATELLITE!!!!! Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted December 22, 2015 Share Posted December 22, 2015 7 hours ago, Jeanjvs said: http://www.theverge.com/2015/12/21/10642028/spacex-falcon-9-landing-elon-musk-wont-fly Makes sense. They'll probably disassemble it down to its tiniest bits and study the heck out of EVERYTHING first, then display it as the piece of history is it. Like the first Dragon capsule that's hanging up in their headquarters, they're meant to be re-used too, right? Link to comment Share on other sites More sharing options...
Kerbol Macrosystems Posted December 22, 2015 Share Posted December 22, 2015 13 hours ago, cubinator said: "The goal is Mars, because no one wants to go back to Jakku." *facepalm* Did anyone else catch that? Where was that? I missed it. 10 hours ago, Kerbart said: To be honest I'm clueless, given that they're the same (Merlin) engines using the same fuel. The only thing I can think of is that the stakes are a lot higher for the second stage. Failure to reignite means the mission is lost. Failure to reignite on the first stage... Meh. At this stage, landing is still the icing on the cake; putting the payload into orbit is in the end what really counts. So I'd be a lot more nervous about the second stage doing it's job (just like you're watching a superhero movie and you know he's going to prevail—the fights can still be nailbiters) than the first stage landing safely. RP-1 and LOX aren't hypergolic, which means they won't just light by mixing them together. You need an ignitor sitting in a cloud of RP-1 and oxygen at the same time to start the engine fire. When you're on the ground you have a little bit of leeway because even if you get bad mixing the RP-1 will light against air, then when the LOX finds the flame it will join in and you get full thrust. In vacuum you must get a good RP-1/LOX Cloud around the ignitor to start the engine. Otherwise you're just venting unburnt gases. To complicate this further getting a good flow of liquids in microgravity is tricky, and it's tougher on a near empty tank . There's a lot that has go right to re-light a rocket in space. 10 hours ago, Zucal said: Helicopter view of the landing. Nice. https://www.youtube.com/watch?v=ZCBE8ocOkAQ&feature=youtu.be&app=desktop Awesome! 6 hours ago, PB666 said: Well if they wanted to show off they could have landed inside of the VAB. Can i add that their landing trajectory doesn't make much sense, if you have east bound momemtum at peak altitude why reverse it to land with west bound momentum? dV in the x,y needs to be added twice then stppoed twice, this is 3 additional dV just to land (although the primary occurs after stage 2 sep), if they had chosen a pad and a landing site at different locals they wouldn'.t have had to carry this extra fuel and they have more payload cap. Air Force Space and Missile History Center https://goo.gl/maps/XJsZwWjnutT2 You can see on Google maps that there isn't any land to the east, and there aren't any launch complexes to the west. There's also a lot of population to the west that we don't want to launch over. Link to comment Share on other sites More sharing options...
AngelLestat Posted December 22, 2015 Share Posted December 22, 2015 20 minutes ago, CatastrophicFailure said: Makes sense. They'll probably disassemble it down to its tiniest bits and study the heck out of EVERYTHING first, then display it as the piece of history is it. Like the first Dragon capsule that's hanging up in their headquarters, they're meant to be re-used too, right? Why disassemble? If the static fire works.. and they test that sensors and circuits work. Is enough. Just the fact that it landed, is the best proof that it works. I will like to see this booster in a special location as a monument for the first recovered stage. Link to comment Share on other sites More sharing options...
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