SpaceX Falcon 9 historic landing thread (1st landing attempt & most recent missions)

Discussion in 'The Watering Hole' started by georgegassaway, Dec 11, 2014.

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  1. Jan 10, 2015 #151

    Peartree

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    The impressive thing about this landing versus the previous water landings is a roughly 1000x increase in accuracy. The previous landings were shooting for a 30km "target" area. This time, with the addition of completely new, untested, navigation components (grid fins), the target was reduced from =/-30,000 m to =/-30m. That is a HUGE change. And the result was that they did indeed "hit" the target. Sounds like they just hit it a little to fast or just a shade off center or something. From and engineering standpoint, especially for the first flight test of new, unproven navigation components, this is a HUGE win.


    As for why not just "splash down" and then recover, I would guess that any water landing would, regardless of how good or how soft, automatically require the replacement of all the wiring, all the sensors, and everything electric and electronic. It would also require a complete tear down and rebuild of all the engines, probably well beyond what would have been needed otherwise. Salt water is bad. Also, I would think that anytime a big, thin walled, tube falls over into the ocean, a lot of stuff is going to get bent all to crap.
     
  2. Jan 11, 2015 #152

    bobkrech

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    Absolutely correct, but I'm not convinced that the engines won't have to be torn down for inspection after each launch in any event... If you have to rebuild the engines after each flight, and fix a lot of other small items, when you consider the added cost of the extra lift-off mass for the recovery hardware and extra fuel, I'm not convinced that reusability is cost effective.

    Bob
     
  3. Jan 11, 2015 #153

    marcusSRG

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    Knowing SpaceX, if they're making these reuusability claims they are able to back them up to some degree. I'm sure they have considered the refurbishment of the boosters in the cost.
     
  4. Jan 11, 2015 #154

    Fontana

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    Or even build reusability into the original design.
     
  5. Jan 11, 2015 #155

    Mushtang

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    I was surprised to find out from a documentary about the Space Shuttle that they completely tore down and rebuilt every engine after every flight. They took off the recently flown engine and popped on a fresh one, and then the one they just removed was sent back to be dismantled so that every piece could be inspected.

    That was probably expensive as hell but not knowing more about those engines I could easily believe it was necessary.
     
  6. Jan 11, 2015 #156

    Zonie

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    I think this stuff is great. SpaceX is pushing the envelope, technologically and politically. Bravo! Wish I worked for them.
     
  7. Jan 11, 2015 #157

    ThirstyBarbarian

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    I had to go look this up to know what you were talking about. I agree that characterizing the landing as "botched" is completely wrong. It was a complete success. This was an experimental test, and the only way you botch an experiment is to not learn anything from it or to design the test in a way that it doesn't measure what you want to test. As an experiment, I'm sure it succeeded in returning useful data. And it almost resulted in a successful landing as well, which would have been amazing on the first try.

    If you read the article with the "botched" headline, the article is a lot more even handed and reasonable than the headline. At newspapers and magazines, often headlines are written by copy editors, not the authors of the articles, and sometimes the headlines are botched. I'm not sure if that's the case here, but the headline and the article have a definite disconnect.
     
  8. Jan 11, 2015 #158

    luke strawwalker

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    Once the engine shuts down, the stage is in "freefall" and thus the propellants can float around inside the tank all willy-nilly. To restart a liquid propellant stage main engine, the propellants must be "seated" inside the bottom of the tanks. There's a few ways to do that; generally speaking, the easiest and most effective way is to have a set of thrusters that can gently accelerate the stage by pushing it forward-- this "slings" the propellants to the back ends of the tanks due to acceleration, refilling the propellant lines and ensuring the engine has pressurized liquid propellant at the turbopump inlet face when the engine is ignited. Once the main engine reignites, the stage of course accelerates at a much higher level, which causes any remaining propellant clinging to the walls or forward dome of the tank to run down to the bottom, keeping the lines full and ensuring all the propellant can "run out" the propellant line, just as it would "run down the drain" in Earth gravity. This is how the S-IVB did it for the TLI burn to go to the Moon during Apollo. During flight, there are times when the propellants can get "slung" to the forward end of the tanks (during staging, for instance, when the lower stage engines shut down, and suddenly the stage decelerates, which slings the propellant to the far end of the tank, like coffee slung out of a cup when you hit the brakes in your car). Usually the rocket is fitted with "ullage rockets", small solid rockets that will fire as part of the staging sequence to "kick the upper stage forward" and reseat the propellants at the bottom of the tank and lines before the upper stage engines fire up. Starting a rocket engine with the propellant ducts/lines partially filled with gases is a BAD thing, because it will cause the turbopump to cavitate and a dangerous pressure spike to occur and can starve the engine of fuel, causing a shutdown or "hard start" (possibly destroying the engine) and the liquid propellant can suddenly "slam" down into the face of the turbopump and possibly overpressurize it and/or destroy it, and cause pressure spikes or "bounces" in pressure that can cause "pogo" in the engine/stage. For this reason, usually some number of ullage rockets are used during staging to ensure that the propellants are properly seated in the tanks before the engine start sequence on the second or third stage, but this DOES complicate the staging sequence, and introduces a failure mode. That's why liquid propellant missiles like Titan II used "fire in the hole" staging-- where the upper stage engine fired up while the first stage was still thrusting, thus ensuring that the rocket was accelerating and the propellants were seated in the tanks.

    The S-II stage of the Saturn V started out with eight ullage rockets, but this was soon discovered to be unnecessary, and was scaled back to four for all the manned launches (IIRC), at least the lunar ones... the less stage weight in ullage rockets translated almost 1:1 into additional payload weight, at least to LEO. Later flights did away with the ullage rockets altogether-- probably (I would surmise) because the S-II tanks were SO huge (and SO full) that there simply wasn't time or space for the ullage gases at the top of the tanks to make their way all the way to the bottom of the tanks before the ignition sequence of the J-2's would provide positive acceleration to the stage, and force the gases back to the top of the tank anyway...

    The S-IVB, of course, had three ullage rockets on the Saturn IB flights, and two ullage rockets on the Saturn V flights. These were housed in small "triangular looking" housings sticking out the sides near the bottom of the S-IVB stage, between the pair of APU thruster packs that provided stage stability while in orbit (freefall) and which also provided the positive thrust for propellant seating before the second J-2 startup for TLI.

    Studies of stage and propellant behavior in orbit showed that an inordinately small amount of acceleration is required to actually seat the propellants... as little as 1/100 g IIRC... So some stages/systems use boiloff venting of propellants to provide this gentle acceleration and keep the propellants seated in the tanks, by venting the excessive propellant vapors through propulsive nozzles pointing backwards. This is also more efficient thermodynamically, since it keeps the propellant heating and boiloff (for cryogenic propellants like LH2/LO2) to a minimum, by minimizing the amount of surface area exposed to heating, and reducing the amount of propellant in contact with the tank walls/structures to a minimum, reducing heat soak into the propellant itself.

    Later! OL JR :)
     
  9. Jan 11, 2015 #159

    luke strawwalker

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    The Saturn team under Von Braun looked at doing this sort of thing back in the 60's... over in the scale section of the forum, I've done "study summaries" of a number of these sorts of things... complete with pics. They looked at everything from "glideback" S-IB first stages flying back to land using Rogallo flex wings deployed after staging and deceleration, to parachute landings in the ocean and subsequent recovery. At one point there was even a plan developed to potentially partially reuse Saturn V first stages (S-IC stages) via water recovery, having them parachute nose-first into the ocean, and severing the forward tank dome of the oxygen tank via linear shaped charge explosives to create a "cushion" for the water landing (the tankage was considered expendable-- they wanted to recover the F-1 engines intact, which were the most expensive and complex part of the stage anyway). They even did experiments, dunking an H-1 engine into salt water, leaving it there for IIRC about 24 hours, fishing it out, and then treating it to a wash-down, with appropriate delays built in to simulate recovery times required, rebuilt it, and then test fired it again in a test stand, quite successfully in fact. What it boiled down to in the end is that NASA neither wanted to spend the time or money to make recovery of the first stages of the Saturn V or Saturn IB a reality, thus this work never proceeded past the proposal and experimentation phase. It wasn't necessary to the overarching goal-- putting a man on the Moon before the Soviets, so it simply wasn't a priority. By the time that had been achieved, there was no money to do it and NASA organizationally was looking to move on to a "fully" reusable system in shuttle (as it was proposed at the time, with a liquid propellant flyback and landing first stage and orbiter).

    During the shuttle development, and in proposals for advanced boosters during the shuttle era (and other improvements) there were proposals for reusable liquid-propellant boosters, some using a cluster of four SSME's each, some using varying numbers and types of other liquid propellant rocket engines. These were to be housed in sealed "boattails" at the base of the boosters, equipped with closing, water-tight "petals" or "shutters" that would unfold and cover the base of the boattail (and the engine bells within it) so they could splash down under parachute into the ocean, and simply lay over on their sides and bob there in the swells, awaiting retrieval and towing back to KSC for refurbishment and reuse. These systems were never really tried (that I've found anyway) and were considered at best complex and potentially unreliable, to somewhat fanciful in terms of their practicality and effectiveness to stand up to real world conditions of an ocean splashdown. By that time, NASA had some experience with "reusable" components (shuttle boosters) that splashed down at sea and were immersed in salt water for extended periods, and knew the difficulties and expense of refurbishment in terms of actual costs, even for relatively "simple" systems like the APU's and nozzle vectoring hydraulics, avionics, etc. contained in the SRB boattails, as well as elsewhere on the shuttle SRB's (forward compartment). That's why "ocean splashdown reusability" wasn't really embraced as a desirable method of operation for any further 'reusable' components. It also became known after the shuttle program completion that basically, it cost SO much to recover the SRB's from the water and to refurbish its operating systems and components and test and reintegrate them into another launch-ready SRB, that it would have been cheaper to actually build ALL-NEW SRB's after each flight than to recover them, at least using the operational methods as the SRB's were designed. It's also worthwhile to consider the sheer forces acting on these things when they actually splash down... the reusability of the SRB's came to an end for Ares I/V and SLS after the SRB-X flight, where the existing shuttle casing (with a fifth "dummy segment") landed SO hard (due to the extra weight and the partial shredding of its parachute system) that the case was bent/flattened beyond repair or reuse by the water landing-- now that's a 146 inch (just over 12 feet diameter) casing made of 1.5 inch thick solid steel, in the case of the SRB... now imagine a LIQUID rocket stage plunging into the ocean under parachute, made of ALUMINUM or Aluminum-Lithium alloy that's only anywhere from maybe 1/4 inch thick (at the bottom end) to 1/16 inch thick or less (at the upper end) and 10-12 feet across or more... it's going to be hard for it not to crush like a beer can under it's own weight due to the impact forces, or fold in half... and how do you trust a structure that delicate after plopping it into the ocean under parachute (which is anything but gentle) not to fail when filled with the weight of tens to hundreds of thousands of gallons of propellants at anything from room temperature to -291 degrees F (for LO2), pressurized to 40-60 PSI (head pressure in the tank), and carrying the weight of tens of thousands of pounds of upper stage structures, interstage(s), and payload above it?? (a liquid rocket structure is, for all intents and purposes, essentially a big aired-up tire in terms of how the load bearing part works). Now imagine that load being multiplied by 3-4 times or more during ascent acceleration, with the additional pressure of thousands of pounds of force exerted on the vehicle and payload fairing during launch through max-q, vibration, effects of cryogenic temperatures on metals in the tank walls, and now throw in possible salt water corrosion... One dent, one unseen crease or kink lets go, the whole thing rips apart or blows up. THAT is why "splash down" LRB's were generally discarded as a viable reusability method... If you're talking about SRB's or PRESSURE-FED LRB's (using lower efficiency pressure-fed liquid burning booster engines, but requiring SRB-like heavy, thick-walled tanks to contain the propellant and pressurize it to hundreds or thousands of PSI to inject it into the combustion chamber of the rocket engine directly without turbopumps) then we KNOW that is *possible*, but it's not particularly beneficial or *practical*, and certainly not *desirable*.

    This is part of what shuttle manager John Shannon called "the myth of reusability" in his testimony before the Augustine Commission back in 2010 (IIRC). Shuttle cost SO MUCH to reuse due to the high amount of refurbishment work and the expense of it that was necessary, that it was basically just as cheap, if not cheaper, to simply throw everything away and build all-new parts for subsequent launches-- this was true of the SRB's and the SSME's, if not the orbiters and SRB casings themselves (which is debatable). That is why the SLS will use the existing SRB shuttle casings one final time-- and drop them back into the ocean without parachutes, where they'll smash to bits or flatten like pancakes when they impact the water at ~250 mph and sink to the bottom of the Atlantic... and once the existing supply of shuttle-era booster segments is used up, NASA will have to develop all-new EXPENDABLE rocket boosters to take their place-- either the ATK "Black Knight" carbon-filament-wound composite advanced SRB's, or the F-1B kerosene engine powered Dynetics "Pyrios" boosters... NEITHER will be reusable, and new ones will simply be built for every flight. That's why NASA even sold off one of their two SRB recovery ships, and converted the other one into a camera ship for photography of launches from out at sea...

    Elon and the space community at large has learned these lessons, hopefully, or at least observed them. They know that for reusability to actually be WORTH THE EXPENSE, you MUST have the rocket stage return in as GOOD A CONDITION AS POSSIBLE, requiring AS LITTLE REPAIR/REFURB POSSIBLE and the LOWEST AMOUNT OF TURNAROUND POSSIBLE in order to reliably and safely relaunch using it. That was what KILLED shuttle-- NASA *purposely* under-estimated the amount of refurbishment and turnaround required between launches of not only the orbiter and SSME's, but also the SRB's and the system as a whole, while simultaneously VASTLY underestimating the cost required to perform that refurbishment and preparation work, as well as MASSIVELY overestimating the flight rates and "demand" for shuttle launches, to spread those costs over an enormous number of launches that was never going to happen anyway. That's how the shuttle was sold-- with wild estimates of it flying up to 70 times a year with per-flight costs of only as little as $10 million dollars each (in the wildest of the 'estimates' NASA touted). Even when "reality" set in (as NASA saw it) in the later 70's, they still wildly overestimated shuttle's flight rates and underestimated its refurbishment costs... it was advertised as flying about 50 times a year (basically, weekly) at a cost of about $35 million per flight. The SSME's original design specifications called for them to be reused up to 100 times WITHOUT OVERHAUL. This was later lowered to 50 flights. In practice, EVERY SSME was TOTALLY stripped and rebuilt after every flight-- parts that could not be taken apart (welded together) had to be laboriously inspected with bore-scopes to ensure that no cracking or damage had occurred (and oftentimes damage and cracks WERE found) so in the end, every shuttle engine had to be completely rebuilt after every flight, and test-fired at Stennis Space Center before being sent to the Cape for use on future shuttle flights. This made the SSME's nearly as expensive to refurbish as to replace outright with new engines, especially if one considers the savings from mass production (SSME's were extremely expensive because they were produced only in very small batches a few engines at a time, and were extremely complex and very high performance... had they been designed simpler and cheaper and produced "in bulk orders" and thrown away, they should have been much cheaper to produce and cost much less than rebuilt reusable SSME's (which is exactly what they're planning to do on SLS... course the flight rate on SLS is going to be SO pathetically low (1 flight every 2-3 YEARS) that these 'mass production" savings may well never materialize... )

    Anyway, for reusability of the Falcon 9 to ever make sense, the thing has to land INTACT, in OPERABLE CONDITION, and require only basic service, testing, and checkout before being sent for integration into a new launch vehicle. If it requires extensive salt-water impingement mitigation (beyond a good pressure washing), large amounts of complex touch-labor inspection, refurbishment, testing, and turnaround before it can be reused, it would QUICKLY surpass the expense of simply replacing the stage with an all-new one and foregoing the expense and complexity of actually recovering the stages and refurbishing them for reuse.

    Later! OL JR :)
     
  10. Jan 11, 2015 #160

    luke strawwalker

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    I only believe half of what I read and NOTHING that I see on TV...

    Later! OL JR :)
     
  11. Jan 11, 2015 #161

    mpitfield

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    Wow that is pretty informative stuff. I am guessing you are in the Aerospace industry or a very keen follower. It's amazing at all of the small but big differences between rockets that fly within gravity and those that go into space. It just shows you how much we have learned and how pioneering this venture was/is, especially for the first astronauts. In hind sight those first astronauts must have been a bit crazy.
     
  12. Jan 11, 2015 #162

    Mushtang

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    It's amazing how much your average corn farmer knows about the space program, isn't it?
     
  13. Jan 11, 2015 #163

    georgegassaway

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    I'm replying to these two posts on another thread.

    Well, when Musk said "hard landing" he may have been obscuring things. It may have landed at about the normal speed, but landed off-center. There is damage to some of the equipment at one end of the barge. This indicates a sideways error. Unless it hit hard near center, broke a leg or collapsed, then happened to fall over onto one end of the barge. Or perhaps a combo of both, too fast and landing near one end.



    When the grid fins ran out of hydraulic fluid, they may have "stuck" in whatever non-neutral position they were in at that moment. If so, then there were aerodynamic forces trying to steer it one way while the vectored thrust was trying to steer it another way. Also,, if the grid fins were stuck to cause a roll, that may have really screwed things up as IIRC the booster does not have any "vernier" rockets to control roll (when only the center engine is firing for landing), only cold-gas thrusters which may not have had the torque to overcome roll torque produced by the grid fins.

    Also, the guidance software may not have had any provision for what to do about the grid fins not producing the expected guidance response. Especially perhaps not what to do in the case of the grid fins producing aerodynamic forces that were fighting the vectored thrust. This make me think of something developed for fighter jets. "Adaptive flight control" IIRC, where say damage causes the left aileron to be knocked off…..or even half of the left wing, the computer running the fly-by-wire system works out how to "adapt" to such a situation and the plane is still controllable. But you would not tend to think of the potential need for such a thing for a launch vehicle, at least aerodynamically. It DOES have the ability to keep flying on launch if one of the nine engines goes out. But if one of the three goes out during the boostback and/or re-entry burn, it may not be able to handle that.. If the center engine goes out on landing, game over.

    Although, Columbia's last flight with ever-increasing problems as its left wing was damaged more and more by hot plasma entering the leading edge hole, and had a hole burring thru the top of the wing skin. That caused more and more drag on the left and less lift on the left, the flight computers managed to keep it flying "normally" right up to the moment that the left wing broke off.

    So, anyway, it would seem that the grid fins, which were critical for getting it "close" to begin with, caused too much of a problem when they quit working, likely in a non-neutral position, for the vectored thrust to be able to land it as accurately as it always had in "test hop" landings in McGregor Texas.

    And in "fighting" for control, the rocket might have ended up with a sideways drift velocity as it landed.

    This is part of why I am a BIT skeptical as to there not being any video due to darkness and fog. The barge had floodlights, and the exhaust flame would have illuminated it way more than floodlights. Of course superdense fog would have made for some really crappy video quality, but it would be possible to see the basic nature of what happened.. So I suspect they are using the darkness and fog as an excuse. Otherwise…… it was daylight 2-3 hours later…. still no pics. As the saying goes: " Pics or it didn't happen!".

    BTW - The ASDS barge is due in port in an hour or so, so there may be some photos taken by people on shore soon. Though I won' be surprised (though disappointed for sure) if SpaceX tries to sweep everything under the rug. I mean, uh, cover everything with tarps.

    Unfortunately, the F9R rocket that took over from Grasshopper for test landings, only got in one landing to test the grid fins before the next flight which developed a problem during climb and had to be self-destructed. Otherwise, some have speculated, more test flights with the grid fins may have helped to indicate more use of the hydraulic fluid than expected. But then the test hops were descents from no more than 1000 meters that only lasted 30-40 seconds or less from apogee, at a few dozen mph, not minutes-long hypersonic re-entries from 45-50 miles up, and not even representative of the free-fall speed for the last 1000 meters on a real landing from space. So the only kind of test flight that could have shown a realistic usage rate of the fluid was yesterday's flight. Musk says they'll add about 50% more fluid for the future, to make sure it does not run out (and whenever they do RTLS landings, those re-entries might last longer and if so would therefore use more from re-entry to touchdown)

    - George Gassaway
     
    Last edited: Jan 11, 2015
  14. Jan 11, 2015 #164

    Winston

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    OT, but interesting reading, the Columbia Accident Investigation report:

    http://www.nasa.gov/columbia/home/CAIB_Vol1.html

    The Crew Survival Investigation Report:

    http://history.nasa.gov/columbia/columbiacrewsurvival.pdf

    determined that crew fatalities were likely due to trauma to the head and spine due to failure of the harness inertia locks to activate.
     
  15. Jan 11, 2015 #165

    jmattingly13

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    Even with a soft landing, you're going to have lots of debris, unless you somehow manage to soft land sideways, which I'm pretty sure isn't possible with Falcon's configuration (or really any standard rocket configuration). If you somehow managed to get a tall rocket stage horizontal in the water, you still have to contend with waves that can destroy the airframe.
     
  16. Jan 12, 2015 #166

    mpitfield

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    I am with you on the skepticism, I have always been a fan of SpaceX and Elon even in the early days when alot of his current fans passed him off as naive and optimistic which is the polite version. So it dissappoints me that he is not being a bit more transparent on it, private corp and industrial espionage issues aside. I would bet that more video footage will show up in time.

    I am curious as to how the barge arrives, my guess is that it will be obfuscated to a degree...we will see.
     
  17. Jan 12, 2015 #167

    mpitfield

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  18. Jan 12, 2015 #168

    georgegassaway

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    Based on pics taken as the ASDS barge came back to port, it seems as though the booster hit on the corner. A composite pic posted on NASAspaceflight, modified previous image of the barge to indicate where it seems to have hit, then a view from today of that area.

    [​IMG]

    Apparently no big pieces. There are some under tarps but of course nobody knows what those are.... other than the fact there's nothing big enough to be tanks. Hopefully some of the engines, though they'd only be useful for analysis and "artifacts", not for reuse.

    - George Gassaway
     
    Last edited: Jan 12, 2015
  19. Jan 12, 2015 #169

    ThirstyBarbarian

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    So did the booster topple overboard and sink, or was the wreckage recovered too?
     
  20. Jan 12, 2015 #170

    georgegassaway

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    Seems like most of it ended up overboard. Though there are some pieces under tarps.

    There is a puzzling image, showing two holes in the side of the barge (inside yellow ovals), which were not there in previous photos of the barge. Speculation is that those were made by landing legs, which if true would tend to indicate a horizontal vector flying towards the barge.

    - George Gassaway

    [​IMG]


    http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=36326.0;attach=630937;image
     
  21. Jan 12, 2015 #171

    mpitfield

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    Great eye George, I stared at that picture and never thought to look below the gunnel.
     
  22. Jan 12, 2015 #172

    Mushtang

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  23. Jan 12, 2015 #173

    Zebedee

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    Given how biased and flat out wrong most news reporting is these days, I'm not surprised they released no video or details.

    You'd probably have some ignorant idiot yelling about how the whole thing is unsafe and should be scrapped before it crashes into peoples houses...
     
  24. Jan 12, 2015 #174

    boatgeek

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    Is it common for hydraulic fluid in spaceflight to be a consumable? In my world, you only lose hydraulic fluid if something bad happened, broken hoses being most common.

    Another possibility is that a leg or something else nailed the barge as it was either tipping over the side or while the stage was floating nearby. The lower one looks like something pointy at about 3-6' in diameter, with the upper one a little smaller. A tapered leg hitting the side a couple of times in a seaway would make sense for both, but it would have to have been an awfully hard hit. Anyone know what the weather/sea conditions were at the time?

    My totally groundless speculation is that the stage hit the barge to windward and at the end, but only got 1-3 landing legs on the barge. It then torched the containers as it was trying to hang on the the landing, then fell over into the water. The holes were from the legs hitting the side of the barge as wind and waves pushed the stage against the barge. I don't think there's enough fire or mechanical damage for the stage to have come completely apart and either blown up or spread burning fuel.
     
  25. Jan 12, 2015 #175

    georgegassaway

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    Yes it is, some rockets have done that. It weighs less overall to have the fluid be used one-shot then dumped (or collected in a non-pressurized tank) rather than recycled and repressurized by pumps. BTW - the hydraulic fluid does not necessarily need to be petroleum-based, for what I've been reading it could in theory be as simple and benign as canola oil.

    Think of it as being sort of similar, in the most basic manner, to their cold gas thrusters that are used for orienting the rocket body in vacuum before reentry, and until the grid fins were added also tried to keep the rocket body steered toward the ocean target during re-entry and all the way down till the last few seconds when the center engine lit to land. By cold-gas, it's simply a gas at high pressure in liquid form, that valves allow to escape to "fire" the desired thruster.

    On one of the landing flights after staging, the thrusters had so much trouble trying to keep it controlled that the tank ran empty. Now, they could have tried to solve that by using a bigger tank, and also perhaps using more thruster power (requiring even more RCS gas). Also, they needed to add aerodynamic steering because even when the RCS thrusters worked al the way down, they had an error of 10 kilometers from the intended ocean landing spot.

    So, they chose to go with the grid fins to get aerodynamic steering (actually due to the R&D and fabrication time, the grid fins must have been in development for a pretty long time, not something they realized "oops - we need to come up with a fix QUICK"). Actually I would not be surprised if they reduced the amount of RCs gas stored since with the grid fins steering it most of the rest of the way now after re-entry begins (plus steering by the Falcon's engines during the powered part of the re-entry), there would be less need for the RCS to do anything (once the re-entry burn has begun), unlike previously when it was trying like crazy to steer it thru the air after the engines shut down.

    Anyway, in the same manner that the RCS tank has to have enough in it for the RCS to work all the way down (before the grid fins were added), same for the hydraulic fluid for the grid fins, it used a bit more than they expected so the "easy' fix is to use a bigger tank.

    Or, heck, for that matter, same for your car's gas tank if you only knew from a "drive test" in your driveway how much fuel it used, then tried a 400 mile trip without refueling (no gas stations in this theoretical case) based on the driveway fuel use rate. You might be in for a nasty surprise.

    BTW - the image I posted earlier with the yellow ovals pointing out holes in the barge side, that was not mine. I found that on the NSF forum, pointed out by others.

    - George Gassaway
     
    Last edited: Jan 13, 2015
  26. Jan 12, 2015 #176

    Winston

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  27. Jan 13, 2015 #177

    mpitfield

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    Its too bad that SpaceX couldn't find a patch of land as it seems that the whole floating barge that is not necessarily in the spot the rocket thinks it is, combined with the added heaving of the seas, seems to be contributing a lot more to the failure than the test. I wonder if there was a land based pad if these landings would of failed.

    Forget the volcano, Elon needs to buy an Island and launch/land his fleet from under his pool, like Thunderbirds "SpaceX are Go"
     
  28. Jan 13, 2015 #178

    georgegassaway

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    Nice Thunderbirds reference.

    The failure was not the barge being out of position, or heaving. If it was trying to land on…. land, the problem with the grid fins would have still made it miss the prepared landing spot by 30 meters or so. Though it probably would have landed safe (depends a LOT though on whether during the attempted landing on the barge, the vectored thrust fighting with "stuck" aerodynamic control surfaces that put the rocket out of horizontal position from where it should have been at the last few hundred feet of altitude before the engine ignited, may have caused it to have a horizontal velocity that for a landing on a solid surface would have resulted in it breaking a leg, the body to buckle, or otherwise falling over).

    It has now become more apparent that the Barge is sending GPS coordinates to the rocket so that it may actually trying to home in on the barge via GPS updates. Although the barge is still supposed to be here it is supposed to be, but if it is off by say 10 meters, that may not mean the rocket would then miss the "X" by 10 meters even if the rocket landed dead center on the original GPS coordinates. That court document to fight the Blue Origin patent includes info on a US Navy F-18 test program for an automated landing system where the F-18 "found" the aircraft carrier and landed itself automatically.

    Back to the "island" idea, that would have been something to consider if there was an island about 200-250 miles North North East (give or take) from the Cape. Because for the ISS missions, the azimuth angle of the launch trajectory requires flying in that direction. Which might be practical for the NASA missions to ISS. But would be useless for most if not all non-ISS launches of payloads which tend to be launched East South East (more or less). So, there'd be a need for a 2nd island at about 200-250 miles away.

    That is one of the big benefits of the landing barge, the put it exactly where it is optimum to put it. When they do the Falcon Heavy launches, to recover the center core which will come down many hundreds of miles downrange (SWAG-guessitmate perhaps over a thousand), they can simply tow the barge farther out. Though it will take days longer to get back to port. Otherwise, they'd need to have at least a third island to land at!

    Looking farther down the road, when the next landing attempt flight is a week or so away, should this thread be continued for that and others, or create a new thread for that flight? Prefer to hear the most from interested TRF mods say in that regard.

    There is a Falcon launch from the Cape scheduled for Jan 29th, But Musk's quote on the next landing attempt was "next month". So unless the Space Flight Now website has an outdated list, then the only Falcon-9 launch for February is for Eutelsat 115 A and B (Two satellites) around Feb 17th.

    - George Gassaway
     
    Last edited: Jan 13, 2015
  29. Jan 13, 2015 #179

    Fontana

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    Maybe he said next month, due to the delay in this launch, might push next launch passed the 29th
    I think they would like to be able to launch in quick succession, but passed try's have always been met with delays
     
    Last edited: Jan 13, 2015
  30. Jan 13, 2015 #180

    Mushtang

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    Perhaps eventually they'll get this to the point where it's safe enough to launch off the coast near Houston, TX, and land the first stage in an open area of Florida or Georgia depending on what orbit they're trying to reach.
     

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