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SpaceX To Attempt Falcon 9 Landing On Autonomous Spaceport Drone Ship

Posted by Soulskill on from the good-luck dept.

An anonymous reader writes: SpaceX has announced that at the conclusion of its next rocket flight, it will attempt a precision landing of its Falcon 9 first stage onto an autonomous ocean platform. They say the odds of success aren't great, but it's the beginning of their work to make this a reality. Quoting: "At 14 stories tall and traveling upwards of 1300 m/s (nearly 1 mi/s), stabilizing the Falcon 9 first stage for reentry is like trying to balance a rubber broomstick on your hand in the middle of a wind storm. To help stabilize the stage and to reduce its speed, SpaceX relights the engines for a series of three burns.

The first burn—the boostback burn—adjusts the impact point of the vehicle and is followed by the supersonic retro propulsion burn that, along with the drag of the atmosphere, slows the vehicle's speed from 1300 m/s to about 250 m/s. The final burn is the landing burn, during which the legs deploy and the vehicle's speed is further reduced to around 2 m/s. ... To complicate matters further, the landing site is limited in size and not entirely stationary. The autonomous spaceport drone ship is 300 by 100 feet, with wings that extend its width to 170 feet. While that may sound huge at first, to a Falcon 9 first stage coming from space, it seems very small. The legspan of the Falcon 9 first stage is about 70 feet and while the ship is equipped with powerful thrusters to help it stay in place, it is not actually anchored, so finding the bullseye becomes particularly tricky."

62 of 81 comments (clear)

  1. Hmm by Rei · · Score: 4, Interesting

    Why don't more billionaires do stuff like this?

    I'm not saying do it "for the benefit of humanity", or even "for a profit". Just simply.... if you have billions of dollars, and you want to spend it on something, what can you possibly spend it on that wins in a sheer awesomeness category as "shooting a gigantic rocket up into orbit and then landing it on a robot boat in the middle of the ocean"? That's like a freaking video game, played with 1500 tonnes of aluminum and highly combustible fuel.

    --
    "We consider that six courts and an asylum claim are a rather odd way of returning to Sweden within a month."
    1. Re:Hmm by peragrin · · Score: 1

      Because they became billionaires through luck ambition and pinching penny's. Not by doing cool things.

      Also it is relative to the interests of the billionaire themselves. While most don't like Larry Ellison for oracle. Those billions are being spent on make awesome sailboats and doing major races with them for personal glory. Of course he is doing it the Larry Ellison way so some don't like him for it but the advances made in hull design over the last decade have been impressive.

      --
      i thought once I was found, but it was only a dream.
    2. Re:Hmm by Applehu+Akbar · · Score: 1

      The wealthy have ALWAYS done stuff like this, which is how they became outrageously wealthy. That's how we got railroads, power grids, and aviation.

    3. Re:Hmm by Rei · · Score: 1

      I'm not talking about ideals, or tourism, or saving the world, or finding anything "up there", or anything of that nature (did you even read what I wrote?). I'm talking about the sheer awesomeness of, at your whim, shooting up a 1500 tonne rocket into orbit then landing it on an automated oceanic platform. It's like playing Kerbal with a real-life 70-meter tall rocket. Why don't more billionaires do stuff like that if only just for the fun of it?

      But clearly you have an axe to grind against something for some reason, so I'll let you get back to that wheel.

      --
      "We consider that six courts and an asylum claim are a rather odd way of returning to Sweden within a month."
    4. Re:Hmm by killkillkill · · Score: 1

      But railroads, power grids, aviation, oil infrastructure that supports global trade and 2-day deliveries of almost anything you could want, software and hardware that revolutionized society with personal computing... All these are boring commonplace things. Billionaires are just penny-pinchers that are screwing us out of our money for nothing in return.

    5. Re:Hmm by Ryanrule · · Score: 1

      those were all govt funded and developed, then leeched off of by the wealthy.

    6. Re: Hmm by theCzechGuy · · Score: 4, Insightful

      Really? So how many space contractors can deliver payload to ISS at this moment? SpaceX isn't doing anything better than all those that can't? And how many contractors can deliver a kilogram of payload to the orbit for a comparable price to SpaceX? I get that some people may be sick all the adoration SpaceX is getting lately, but that's not a good excuse for ignoring the reality and substituting your own.

    7. Re: Hmm by theCzechGuy · · Score: 1

      Railroads - partly. Power grid - yes, at least in most of Europe. Aviation - not really. It all started with private entrepreneurs, the first time governments started any interest in aviation, it was WW 1.

    8. Re: Hmm by Applehu+Akbar · · Score: 1

      You raise an interesting point: if you want the government to take an interest in your idea, think of way of weaponizing it. Apollo was sold as an escalation of Cold War rivalry.

    9. Re:Hmm by pavon · · Score: 2

      Running a business like this takes a lot of work, and for it to succeed well enough to actually get working rockets off the ground you need to attract top-notch engineers who believe that working for you isn't just a waste of their time (more than a billionaire's plaything), and management that can create the right environment for them to succeed without blowing through your money for nothing. It is much less expensive, less risky and less time consuming to just pay Russia for a thrill ride than to create your own rocket company. So I can understand why most would choose to go that route, and leave the latter for those who genuinely want to shake up the market.

    10. Re: Hmm by theCzechGuy · · Score: 1

      True, but you also have to have a conflict that allows the government to justify the spending. It doesn't always have to be an open one (as was the case with Apollo and the Cold War), but it still seem as inefficient way to make any progress.

    11. Re:Hmm by Rei · · Score: 1

      So you think massive yachts, ridiculous-priced art/jewelry purchases, palatial estates, gold-plated toilets and the like are a better use of money?

      Trust me, I'd have a LOT more fun with a giant rocket than I would with a gold toilet.

      --
      "We consider that six courts and an asylum claim are a rather odd way of returning to Sweden within a month."
    12. Re:Hmm by Teancum · · Score: 2

      In fairness to Elon Musk, he actually wanted to blow about a half billion dollars on sending a greenhouse to the surface of Mars.... pretty much as a philanthropic venture or as just blowing the money for the hell of it. He even got so far as going to Russia and trying to negotiate the purchase of an ICBM to get the project to happen (where they even offered the nuclear warhead with the deal... something he turned down).

      Along the way, one of those in Russia insulted him big time and basically challenged him to try and do this himself. After a little investigating about the topic, he went to Los Angeles County to recruit a few aerospace engineers who were building rockets capable of going into orbit as a hobby, and offered them a full time job to make a clean-sheet new rocket from scratch. That company is now SpaceX. The hobby guys are still making rockets that are being launched in the Mojave desert, but a great many of those guys are getting hired by a new set of space-related companies building stuff now.

    13. Re:Hmm by Rei · · Score: 1

      That's not all that different from how he got started with Tesla. He had no intention of starting a car company (he already had SpaceX), he just wanted AC Propulsion to build him a copy of their t-zero - but they had no interest, even for a small fortune. But then they pointed him to this guy named Martin Eberhard who had this wild idea to commercialize the t-zero's tech base on a Lotus Elise body and was looking for funding... and thus Tesla was born.

      --
      "We consider that six courts and an asylum claim are a rather odd way of returning to Sweden within a month."
  2. I would love to watch this by jfdavis668 · · Score: 2

    from a safe distance.

  3. As long as they get close it's a win by trout007 · · Score: 4, Informative

    The goal isn't to land on a barge, but back at the launch site (or at least near it). If they can show over a couple attempts that they get close to the target then they can move to doing this over land. They have already proven they can do this in Texas many times. It doesn't really matter if they tip over over land too hard at sea. What you don't want is that it missed by a mile or cartwheels out of control.

    --
    I love Jesus, except for his foreign policy.
    1. Re:As long as they get close it's a win by Anonymous Coward · · Score: 1

      No... the goal is to land on the barge. Otherwise there would be no barge, just an arbitrary lat long that they aim for,

    2. Re:As long as they get close it's a win by KIngo · · Score: 1

      The center core of a falcon heavy (the triple-core version) stages too far away in order to return to the launch site. It will be landing on that barge.

    3. Re:As long as they get close it's a win by Bruce+Perens · · Score: 1

      You mean it drops off too high and downrange to boost back to the launch point and too low to achieve most of one orbit before boosting back to the launch point. Right?

      --
      Bruce Perens.
    4. Re:As long as they get close it's a win by DerekLyons · · Score: 2

      If they can show over a couple attempts that they get close to the target then they can move to doing this over land. They have already proven they can do this in Texas many times.

      There's a reason why they're flying all these attempts over water - they haven't done it in Texas even so much as once. The flights in Texas have been "take off, go a short distance up, then land more-or-less right back where you started" - which isn't the difficult part (so far as flight control is concerned, it's more of an engine control problem) as small errors have no time to propagate. The difficult part (from the flight control POV and the reason they are testing on a barge) is the boostback and retro burns, where even small errors in attitude and delta V propagate into significant errors by the time you hit your hovering gates (and is thus an engine control *and* a flight control problem). Another issue, also not tested in Texas, is the aerodynamics and flight dynamics of the returning stage (especially in the high speed regime), and indeed these issues caused a problem on the first attempt.

      So no, coming close isn't a win. They're going to have to demonstrate pinpoint recovery a number of times before anyone is going to let them even consider attempting it over land.

    5. Re:As long as they get close it's a win by trout007 · · Score: 1

      You missed quoting the important part.

      It doesn't really matter if they tip over over land too hard at sea.

      As long as they show a good landing burn over the landing zone it doesn't matter if a pitching deck causes a landing failure.

      --
      I love Jesus, except for his foreign policy.
    6. Re:As long as they get close it's a win by DerekLyons · · Score: 1

      No, I missed the quoting the part that was (more-or-less, mostly less) correct. The parts I quoted were parts that you were wildly incorrect on, as there's considerable distance between what has been tested, and what they are testing. Even so, you're still wrong. Miss the target, by even a little bit, and it's a loss. Land hard and lose the vehicle (not due to sea state) and it's a loss. Tip over and lose the vehicle and damage or lose the barge (not due to sea state), and it's a loss.

      So yes, it does matter if they miss, it does matter if they land hard or tip over - because the whole goal of the test is to demonstrate a successful pinpoint landing. You don't really seem to grasp what's being tested here and why.

    7. Re:As long as they get close it's a win by Teancum · · Score: 1

      No, the current goal is to land on the barge. Preferably they would like to land on an island down range from KSC, but that island simply doesn't exist.

      Yes, the long term end goal is landing preferably on a landing pad about a mile or so away from the launch site at KSC, where it appears to be roughly at the location of pad 39C (or rather where that pad was supposed to be built during the Apollo program.... but never happened).

      On the other hand, it may very well be that boosting back to the site at KSC is not a realistic option simply because the delta-v (change in velocity) is insufficient for a proper return given the other constraints for delivering payloads to orbit. Even now, there are payloads that SpaceX is taking that will use so much fuel that even landing on a barge is out of the question... and the 1st stage is going to simply burn up in the upper atmosphere and break up during reentry.

    8. Re:As long as they get close it's a win by Teancum · · Score: 2

      I don't think the issue is attempting a landing on land, but rather that the proposed site for landing (I think they are proposing to use the site originally designed to become 39C before NASA scrapped that location for Apollo Saturn V launches) is so close to other critical infrastructure.

      If they landed on some use spot of semi-wilderness like where Russia does landings for the Soyuz spacecraft, the Australian outback, or some other similar sized far from civilization, they wouldn't have any problem with attempting a landing on land. The problem is that the eastern coast of Florida is hardly what I would describe as unpopulated wilderness. The chance of the Falcon 9 landing in Miami or even Disney World is just too great. That is why the pinpoint accuracy is so needed, especially with the suicide burn approach that SpaceX is using for the core recovery.

    9. Re:As long as they get close it's a win by matfud · · Score: 1

      A very negative point of view.

      The stage is a loss anyway if they did not try to get it back down and land it. If not it would eventually renter and burn. I thought that was the whole point. Trying to get it back in one piece where you want it to land. If you get it back in one or a few bits then it is a win over just just chucking it up there and knowing you have lost it (as most rockets do)
      There is cost in trying to do so. And yes they do need a perfect pinpoint landing to achieve it. Missing by a bit would show yet again that they can do it but have problems wrt navigation/mobility/finding the target pad or just going boom. But showing possibly that it can be done.

      I am not exactly a fan boy but it is interesting and lots could be learned even if it fails.

    10. Re:As long as they get close it's a win by DerekLyons · · Score: 1

      A very negative point of view.

      Only in the eyes of the completely clueless or the drooling fanboy (not there's much effective difference between the two) are facts "negative".
       

      If you get it back in one or a few bits then it is a win over just just chucking it up there and knowing you have lost it (as most rockets do)

      Since the goal is to recover it whole, no, getting back in 'a few bits' is not a win. It's a failure. That things can and will be learned from such a failure does not change this.

    11. Re:As long as they get close it's a win by matfud · · Score: 1

      Facts are facts. If you decide that they are bad then you will not have much fun in life, perhaps you should look at the upside and what you learned from those facts. Even if the rocket breaks up and plummets into the ocean there is information there that may be useful for your perfect landing criteria.

      Only one of the goals is to land perfectly. Gosh who would have thought that there may be more than one goal.

    12. Re:As long as they get close it's a win by trout007 · · Score: 1

      I'll try one more time. They have shown they can land from a stable position in Texas. If they can show they can get from second stage separation to a similar configuration over a barge in the ocean then it's a success. If they can it will show they have good enough control that range safety will allow them to fly back to try to land on land.

      --
      I love Jesus, except for his foreign policy.
  4. fuel weight by trybywrench · · Score: 3, Insightful

    I thought the main limiting factor of lifting mass to space was also having to carry the fuel with you? SpaceX hauls its fuel to get to space and even extra fuel to land. How are they able to afford to lift the extra mass? Are their engines that much more efficient? I'll stop with the questions marks ;)

    --
    I came to the datacenter drunk with a fake ID, don't you want to be just like me?
    1. Re:fuel weight by DMUTPeregrine · · Score: 2

      They're only lifting extra mass on the first stage, not the payload. So it doesn't have to move the extra mass as much.

      --
      Not a sentence!
    2. Re:fuel weight by Anonymous Coward · · Score: 1

      The Falcon 9 1.1 version is much heavier than the v1 ( and the engines better ), so it can carry over 50% more payload to space. Since that payload is not actually needed for its planned mission, they can afford to carry more fuel in the first stage to attempt recovery.

    3. Re:fuel weight by captainpanic · · Score: 1

      I surely hope that they will let the atmospheric drag slow them down a lot too, like other space vehicles.

      While they do have to carry all that extra fuel, they don't have to rebuild the rocket. They only refuel it. The savings are enormous.

    4. Re:fuel weight by drayath · · Score: 5, Informative

      First issue is economics, fuel cost is 1-3% of launch cost. If you can only get half the payload weight to orbit but get most of your rocket back for reuse (and the first stage is the most expensive bit - 9? engines vs one for second stage), cost per Kg to orbit is still (massivly) cheaper.

      Second issue is that the fuel cost for the first stage recovery is quite cheap, you only have to brake and land the engine and (almost) empty fuel tank so they are very light vs the lauch mass. From memory a while ago spaceX started using v2 of there main engine which was ~10% more efficent than the v1 engine; This gave enough increased performance that even with extra fuel to land and the extra weight from the landing legs etc. they could get the same payload to orbit plus do styage one recovery.

    5. Re:fuel weight by gonar · · Score: 1

      in theory, if you can land the rocket back on dry land, you can refurbish it and reuse it for enough less than the cost of the extra fuel/landing gear/etc to make it a net cost reduction over several launches.

      yes, you are losing some mass fraction of orbital payload, but if the cost savings are sufficient to justify the extra initial expense, then it is a win.

      --
      The difference between Theory and Practice is greater in Practice than in Theory.
    6. Re:fuel weight by Anonymous Coward · · Score: 1

      Everything is a tradeoff. Some fuel saved for landing first stage means there is less payload capability. But they definitely can afford it.

      Right now they have a rocket (Falcon 9 v1.1) that can put bit over 13 tons to low earth orbit *while* softly landing the first stage (reserving some of the fuel for it, adding weight of the grid fins that steer the stage and landing legs).

      Exact same rocket, no legs, no grid fins, no fuel margins could put a couple of tons more to LEO (as to how much is not clear as SpaceX does not market services with non-reusable performance figures. I'd imagine at least 2-3 tons more)

      So it is a tradeoff of X tons of payload capability traded for reusable (hopefully) first stage.

      If what you are sending up is less than 13 tons to LEO (or 4.8 tons to GTO), all is good. You don't need more rocket, F9v1.1 can do it even while reusing the first stage.

      Got something that is bit too heavy for that? Pay more for the launch, SpaceX will not add legs or grid fins, reserves no fuel, more payload goes to orbit, first stage ends up in bits in the ocean. In fact, this would be the smart way to "use up" a stage that has been reused X times where X is the engine design life. Last launch, take off legs & grid fins for re-use on another core, use the rest of the first stage for launch of a heavier payload and discard it.

      Got something even larger? SpaceX is planning on gluing up three F9 cores for Falcon Heavy. That thing is designed to put 53 tons to LEO, 21.2 tons to GTO while reusing at least two of the three cores (center core will be tricky, stages at much higher velocity and altitude).

    7. Re:fuel weight by idji · · Score: 1

      As Elon Musk says MANY times fuel is only 10% or less of the cost of a launch, and as he says MANY times no-one would throw away a Boeing 747 after each flight as it is too expensive.
      He takes extra fuel for the landing - this means he can only launch a lighter cargo, but he can one day reuse his rocket again, so it is worth it.
      The last Falcon 9 flight http://en.wikipedia.org/wiki/S... did not attempt a landing because it took a cargo of 2,216 kilograms (4,885 lb). The last flight which attempted a landing http://en.wikipedia.org/wiki/F..., only had 1000 kg payload.
      The http://en.wikipedia.org/wiki/F... will be able to lift up to 53,000 kg and land again because it is 3 Falcon-9s strapped together.

    8. Re:fuel weight by gman003 · · Score: 2

      Rockets themselves are expensive. Rocket fuel, particularly the sort SpaceX uses, is dirt cheap in comparison - only $200K of their $56M launch cost.

      Yes, having that extra fuel decreases their payload capacity (from what it could be). But they don't need as much fuel when descending, since they no longer have a second stage and payload weighing them down, so it isn't much fuel in total.

      However, the cost of not having to rebuild the rocket every time is much more significant. Even if they can only reuse it a few times, that's a lot of production cost being saved.

    9. Re:fuel weight by rainwalker · · Score: 1

      Their lifting capacity, even with the extra fuel (really, reduced fuel available for ascent) is sufficient, and the small amount of payload reduction is vastly offset by the cost savings of re-using 9 engines plus structure. Assuming everything works, of course, but their program is looking pretty good.

    10. Re:fuel weight by queazocotal · · Score: 1

      The Falcon 9 weighs about 500000kg on launch.
      Most of this is kerosene, and liquid oxygen.
      Both of these can be purchased for under $1/l.
      This is around $400000 or so.
      A falcon 9 launch costs $60M or so - so it's more like a percent.

    11. Re:fuel weight by rufty_tufty · · Score: 2

      There is no extra fuel as such.
      All rockets have more fuel in them than needed for their base mission to account for failure modes. For example if the engines produce less thrust than planned for, it means they can simply burn for longer to still deliver the payload. The Falcon re-usable rockets will use this extra fuel for the flyback if things don't go wrong.
      In the event of an engine out on a Falcon 9 it is highly likely that this margin fuel will be used and therefore that Falcon will not be re-usable because it won't be able to fly back.
      So yes there's extra fuel, but it's extra fuel that sometimes will be needed for the main mission.

      --
      "The weirdest thing about a mind, is that every answer that you find, is the basis of a brand new cliche" -
    12. Re:fuel weight by SparkleMotion88 · · Score: 1

      The amount of extra fuel required to do this is pretty trivial. The atmosphere does most of the work of slowing down the first stage, and it will be very light (because the payload and almost all of the fuel is gone) when you are trying to land it. The value of recovering the first stage greatly exceeds the slight cost of carrying a little extra fuel weight.

    13. Re:fuel weight by matfud · · Score: 1

      Many liquid fuelled rockets never run until they run out of fuel. They are shut off at the appropriate time/place/velocity. So there tends to be fuel "left over" anyway. Now the total mass of one of these 1st stage rockets is primarily fuel/oxidiser. They do not mass much without anything in them. So trying to land it is not quite as expensive as you may think if you take into account the left overs. I presume they are going with the "If there is not enough fuel left let it burn" approach. Sort of trimming the margins to make sure it gets up but possibly it will not get down but should if it all goes well.

  5. Why not on land? by Timo_UK · · Score: 1

    Should be much easier and cheaper. Any non-technical reasons? Tax?

    --
    Timo's Audio Software http://www.esseraudio.com
    1. Re:Why not on land? by captainpanic · · Score: 2

      Probably safety... They expect it to go wrong. Even the most remote places on land have some people. And with this highly experimental flight, the exclusion zone around the expected landing site must be huge. That's only possible at sea.

    2. Re:Why not on land? by Anonymous Coward · · Score: 1

      Very simple - the plan is, in its final stage, to let used first stages (or booster stages on Falcon Heavy) do RTLS - Return to Launch Site. That is currently prohibited due to FAA regulations and concerns at the KSC (etc. etc.) so they are not allowed to try to land on land/the KSC. For the trials, they are using the barge, that can be parked in international waters and therefore is much less subject to laws and regulations. Also, due to the different operation mode, a barge landing will still be an option on later "production" flights if the stage is not able to RTLS due to fuel constraints (for example for GTO missions or the core stage of Falcon Heavy) - in that case, a barge landing, refuel, and flyback to the launch pad is the currently planned mission profile.

    3. Re:Why not on land? by Mysticalfruit · · Score: 1

      I agree plus it gives them flexibility. As much as Elon talks about having the first stage land back at the launch site, there's simply too much valuable infrastructure. Having a fleet of these autonomous ships gets Elon the reusability without endangering his personal and launch sites.

      --
      Yes Francis, the world has gone crazy.
    4. Re:Why not on land? by Mysticalfruit · · Score: 1

      For a falcon heavy having a fleet of these ships would allow them to recover all three first stage elements vastly reducing the cost to put really heavy things like all the elements for a mars transfer vehicle in space.

      --
      Yes Francis, the world has gone crazy.
  6. Re:Someone doesn't understand basic relativity by rdwulfe · · Score: 1

    Except there's no tower to help stabilize if winds kick up, or if you tilt slightly, there's no upward force to keep you going.. CoM is a bigger problem on descent than on launch (though still a problem in either case!!)

    Also, when you touch down, if you have any angular momentum... Bowling pins, anyone?

  7. Mars by daw1234 · · Score: 1

    Every time I read a story about the Space-X reusable rocket I can't help but wonder if they have one eye on their stated goal of going to Mars. Landing a whole rocket vertically on the surface of Mars would probably go a long way towards making a return journey feasible.

  8. Re:Someone doesn't understand basic relativity by A+nonymous+Coward · · Score: 1

    The tower drops away BEFORE liftoff.

    --
    Infuriate left and right
  9. Re:Someone doesn't understand basic relativity by A+nonymous+Coward · · Score: 1

    The mass is less, and presumably easier to control, but yes, that is a difference.

    The relative speeds are the same. Launch starts at 0 and increases to 1300. Landing starts at 1300 and ends at 0.

    Actually, that is a small difference. Launch starts at 0, but landing ends at 2 m/s, leaving shock absorbers to reduce it to the final 0.

    --
    Infuriate left and right
  10. Space is cool and all by fustakrakich · · Score: 1

    But our methods of getting there and back are downright comical...

    --
    “He’s not deformed, he’s just drunk!”
  11. TANSTAAFL by DerekLyons · · Score: 1

    However, the cost of not having to rebuild the rocket every time is much more significant. Even if they can only reuse it a few times, that's a lot of production cost being saved.

    The money saved by not having to produce a new vehicle is offset by the money spent on fixed infrastructure and on recovering and refurbishing the vehicle for the next flight. Airline travel is as a cheap as it is because they've gotten between-flights maintenance down to essentially zero (basically only emergent work) - the expensive refurbishment and refitting occurs at intervals of months to years. (And the amortized costs of the facilities for doing so are spread over a large number of aircraft and a very large number of flights.) The Shuttle was expensive as it was because between-flights maintenance costs were very high. (And the amortized costs of the infrastructure were spread over a very small number of vehicles and small number of flights.)
     
    So, if a first stage (new-in-box) costs $x million and refurbishment costs $.9x million (including the amortized portion of the fixed costs), then it'll have to fly ten times just to break even. The break even point calculation is very sensitive to flight rate, flight interval, and the number of vehicles in the fleet. The hope is, over a long time frame, to reach civil aviation levels... but there's a long way to go between here and there. (Particularly in light of the low flight rate of F9 launches that have sufficient spare payload capacity to allow them to be recovered.)

  12. Wildly premature question by q4Fry · · Score: 1

    How many times do they expect to be able to use a rocket stage before the increased risk of failure (over a brand new one) causes them to scrap it?

    1. Re:Wildly premature question by Bruce+Perens · · Score: 1

      If we look at jet aircraft, wear depends on the airframe and the engines, and the airframe seems to be the number of pressurize/depressurize cycles as well as the running hours. Engines get swapped out routinely but when the airframe has enough stress it's time to retire the aircraft lest it suffer catastrophic failure. Rockets are different in scale (much greater stresses) but we can expect the failure points due to age to be those two, with the addition of one main rocket-specific failure point: cryogenic tanks.

      How long each will be reliable can be established using ground-based environmental testing. Nobody has the numbers for Falcon 9R yet.

      Weight vs. reusable life will become a design decision in rocket design.

      --
      Bruce Perens.
  13. Re:Someone doesn't understand basic relativity by drerwk · · Score: 1

    Right, but the sentence you are make fun of is talking about stabilizing the rocket as it is coming back into the atmosphere, ass first in a no longer particularly aerodynamic configuration as it is missing the whole second stage and payload section. Flight stability in the nose going first direction is much better than in the engine going first direction. They are not complaining how hard it is to go that last 10m to the landing; I agree with you that stability control at that point is pretty easy. You know the first attempt they made for power re-entry failed because the axial rotation of the booster caused fuel starvation to the engine due to centrifigal force. Full tanks and no rotation at launch save you from that worry.
    And as for less mass being easier to stabilize - can you balance a pencil on your finger? How 'bout a broomstick?

  14. Fixed capacity by pavon · · Score: 1

    One important point that others above have alluded to but haven't outright stated:

    While the exponential scaling of rocket equation is an important limiting issue when building larger and larger rockets, for any given rocket (or rocket configuration) the payload capacity is fixed. If you have a payload that is too large for a Falcon 1Pegasus, but doesn't need the full capacity of a Falcon 9, all that extra capacity goes to waste. It costs essentially the same amount to launch a Falcon 9 at 60% capacity as it does to launch it at 90% capacity. You can share payload with multiple customers, but that limits which orbits they can use.

    Space X can calculate how much weight the recovery system and fuel requires and how much money they can save by reusing the first stage, and give a discount to customers who give up that additional payload capacity. If there is a market for those lower cost launches, then great. If not, then keep treating the 1st stage as disposable.

  15. splashdown by Jookey · · Score: 1

    I don't know why they just don't land the thing in the water. It seems like waterproofing and preventing corrosion is a lot easier to solve than the controll problem of landing on a barge. Unlike landing on the moon, landing on a barge you have to deal with wind gusts, currents, and waves. A splashdown would leave a larger margin of error and neglect the need for landing gear.

    1. Re:splashdown by Anonymous Coward · · Score: 2, Informative

      They tried, but even at slow speeds, the rocket will eventually land, and then belly-flop on the water surface, with causes too much damage, or at least make the structure too unpredictable to re-use. The space-shuttle boosters where also recovered in this way, and for the same reason never re-used.
      The added weight for making it strong enough to handle a belly-flop into the waves is much larger than anything needed to deal with landing on a barge, even so larger that the payload would be reduced to 0.

  16. Re:Someone doesn't understand basic relativity by jabuzz · · Score: 2

    Yes the tower backs away and the holding clamps release. However this happens literally as the rocket blasts away. Have you never watched a a video of a Saturn V launch? Try this one a high speed 500fps 16mm footage from the base of the Apollo 11 rocket. Notice how the holding clamps release to let the rocket move away, which they only do when they get the signal from the onboard systems that all five F1 engines are working properly.

    https://www.youtube.com/watch?...

  17. Re:Someone doesn't understand basic relativity by A+nonymous+Coward · · Score: 1

    The balancing act is almost exactly the same at the last moment of forward flight as it is at the first moment of retro burn, just in a different direction.

    Aerodynamics matter very little at high altitude. They matter some at lower altitude, but I doubt they make much difference when the engine is burning.

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  18. What about landing at White Sands? by El_Oscuro · · Score: 1

    White Sands Missile Range is right next to the Spaceport America and has 4,000 square miles of uninhabited desert. The Army tests rockets there all the time, and sometimes closes highway 70 (which passes through the range) when they do. Since the goal of cheaper launch costs is something the miltary would find useful, I am pretty sure Spacex could come to an agreement to do some testing using the range. Before talking to the Army, Spacex would probably want to run several real tests at sea, where they would expect the landings to fail until wthe worked out all of the bugs with the aerodynmics, winds, etc. Not so much to ensure you can land on a ship, but to ensure you can land within a few miles of where you want to. If you can do that, there are lots of places you can land.

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