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Space

SpaceX Testing Landing Legs On Next Falcon9 Rocket 73

Posted by Unknown Lamer
from the crazy-enough-to-work dept.
astroengine writes with news of SpaceX's next step in experimenting with vertical landings for rocket stages. From the article: "Space Exploration Technologies is installing landing legs on its next Falcon 9 rocket, part of an ongoing quest to develop boosters that fly themselves back to the launch site for reuse. For the upcoming demonstration, scheduled for March 16, the Falcon 9's first stage will splash down, as usual, in the ocean after liftoff from Cape Canaveral Air Force Station in Florida. This time, however, SpaceX hopes to cushion the rocket's destructive impact into the Atlantic Ocean by restarting the Falcon 9's engine and extending landing legs that will be attached to the booster's aft section. The goal is a soft touchdown on the water." The test is scheduled for their ISS resupply mission on March 16th 2014 (the mission also features the launch of the crowdfunded KickSat nano nanosatellites) .
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SpaceX Testing Landing Legs On Next Falcon9 Rocket

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  • by Anonymous Coward on Monday February 24, 2014 @07:00PM (#46329357)
    Did Mork write the summary?
  • SpaceX (Score:5, Interesting)

    by beltsbear (2489652) on Monday February 24, 2014 @07:15PM (#46329495)

    Recovering the first stage (not this time but maybe this year) will make a huge difference in cost. Saving the 9 engines on the first stage alone is huge.

    Much more detail here:
    http://www.nasaspaceflight.com... [nasaspaceflight.com]

    • Re:SpaceX (Score:5, Interesting)

      by cbhacking (979169) <been_out_cruisin ... OLo.com minus la> on Monday February 24, 2014 @07:25PM (#46329587) Homepage Journal

      There will probably be a lot of reconditioning needed anyhow, but yeah, the cost saving could be enormous. The fuel is pretty cheap, really; what makes rocket launches expensive is the need to build an entire new rocket every time. Even the so-called reusable Space Shuttle had a ton (actually, many tons) of parts that were discarded with every launch and had to be built anew for the next one. If SpaceX can actually make the Falcon 9 reusable, it could reduce launch costs by at least an order of magnitude. I think their actual goal is to hit *two* orders of magnitude, and they have a much better ides of costs and feasibility than I do...

      • Re:SpaceX (Score:5, Interesting)

        by strack (1051390) on Monday February 24, 2014 @08:00PM (#46329959)
        Are you sure about that reconditioning? your comparing it to the space shuttle engine, that needed to be torn down, inspected, and rebuilt after every flight. But that was because it was built to razor thin engineering tolerances. The merlin engine is quite a bit more durable.
        • Re:SpaceX (Score:5, Interesting)

          by cbhacking (979169) <been_out_cruisin ... OLo.com minus la> on Monday February 24, 2014 @08:07PM (#46330021) Homepage Journal

          Perhaps "recertification" would be a better word. They will need to do a lot of inspection and probably at the very least unmount and closely examine many of the parts, but it's possible they will be able to re-use them without any actual modification. That would be phenomenal, in terms of cost savings. If the average life expectancy of a rocket engine could be raised even to two launches, the costs would come way down.

          • Well the engines which hit the ocean I doubt are ever going to fly again - once seawater gets into anything mechanical and high performance, the best decision you can make is to scrap it. This sounds more like it's a test of whether the soft touchdown will work, in a way which will not explode so much if it doesn't (like as would happen with a hard impact on land).

            • by strack (1051390)
              Elon Musk has stated in the past that "a little seawater" wouldnt harm the engines.
            • The salt water is less of a problem than the impact. Truax tested firing rockets underwater. It works fine if you chose the materials adequately.

            • by Delwin (599872)
              The intent (not with the Falcon but with later rockets) is for it not to splash down at all but land vertically back on a launch pad. You can then use a crane to put a new second stage on it, bolt it all back together, refuel and relaunch. ... that's the goal at least. We're still a long way from that.
          • by strack (1051390)
            Thats adorable. "a whole 2 launches!". Meanwhile the grasshopper VTVL test rocket did 7 jumps, while using a merlin D engine. This isnt your daddys shuttle main engine.
            • by cbhacking (979169)

              You kind of missed the point of my post, didn't you?

              I never stated, or even implied, that 2 launches was the goal. Nor did I claim or imply that it's all they would be able to achieve. I merely pointed out that even a single re-use would cut costs dramatically (probably by a factor of 1/3 to just shy of 1/2, the rocket being the majority cost of each flight). SpaceX are, obviously, going for far more than a twice-usable rocket. With that said, some parts probably will need to be downchecked and replaced aft

        • Are you sure about that reconditioning? your comparing it to the space shuttle engine, that needed to be torn down, inspected, and rebuilt after every flight.

          Only in the early years of the program. As they gained experience, the maintenance requirements were reduced. By the early 90's, the were removing the engines for borescoping after each flight, but only rebuilding them every fifth or sixth flight. By the late 90's they were removing them every fifth or sixth flight for borescoping and only rebuildin

      • I think the goal is to make it so they just need to test them if certain landing conditions are met. That will take a bit. First they need to inspect a few sets after they land and make sure they match expectations. Then after that with engine out capability they should just be able to test them in the end without rebuilding much at all.

      • by Immerman (2627577)

        I don't think two orders of magnitude is possible - IIRC the cost of fuel is generally at least a few percent of the entire cost of a launch. Assuming 95% of the current cost of is the cost of the rocket you could get perfect reuse and still only get twice one order of magnitude improvement (aka 20x cheaper) Two orders of magnitude would require that you get it down below 1% of the current cost, which would require much cheaper fuel as well.

        • by cbhacking (979169)

          A factor of 20-30 reduction is my guess for where it's likely to wind up in a best-case situation as well, at least with rocketry as we currently implement it. The crazy and wonderful thing is that other changes will potentially make a big difference in the future. For example, if the world ever collectively gets over its brick-shitting with regard to nuclear power, there are conceptual designs for rockets where the energy comes from nuclear sources (such as uranium-hexafluoride gas contained in a quartz "l

          • by Immerman (2627577)

            True enough, though I for one hope the brick-shitting continues until we've got some serious experience with nuclear rocketry elsewhere - lunar launches perhaps. Once we get to the point that the fuel is a major portion of the cost to orbit then other things start being worth consideration - tumbling skyhooks for example, which if used for the return trip as well can act as a momentum bank to completely eliminate 90+% of the energy cost necessary to reach orbit. (and which can easily be made with existing m

        • According to Musk, the fuel cost of a F9 1.1 is ~$300,000, or about 0.5% of the system cost.

          • by Teancum (67324)

            I like to use this analogy in terms of the fuel costs for rockets: The catering budget to feed the press corps at a Shuttle launch cost more than the fuel being used to launch the rocket.

            Even with your figure of about $300k, I would argue that SpaceX spends a comparable amount for public relations + press kits on each flight of the Falcon 9. It really is in the statistical noise level in terms of costs of the launch.

        • http://www.spacex.com/falcon9 [spacex.com]
          500 tons of rocket.
          Let's say it's all fuel (90%+ is).

          It's RP1/LOX.
          You need 2.5:1 liquid oxygen to RP1.

          1980s NASA was paying $.08/kg for LOX. Let's say $.20 now.
          And $.20 per kg for RP1 - at most 100% over spot oil price.
          $1/kg is reasonable.

          Making the average cost per launch for 150 tons of RP1 and 350 tons of LOX about $150K+$70K = $220K.
          The quoted price is $56M - or the fuel cost is under half a percent.

        • by Teancum (67324)

          I don't think two orders of magnitude is possible

          If you want to see what the actual guy who designed the Falcon 9 thinks of the reduction of launch costs, I'd suggest at least reading some of his thoughts [space.com] before pulling up random numbers of your own.

          The long term goal of SpaceX is to start selling Falcon 9 flights for about $20-$30 million with a reusable 1st stage and if they can get the 2nd stage to become reusable they want to get it down to about $5 million per flight... with a hoped-for goal to drop that down to perhaps as low as $1 million. In othe

          • by Immerman (2627577)

            I stand corrected.

            Whoa, a half-million to Mars and back? Now *that* would change things. That's not much more than it currently costs to get a person to orbit, and not even a rounding error on the current cost to get person to the Moon and back.

      • by Teancum (67324)

        At the moment what SpaceX would really love to do is simply recover the Merlin engines, tear them apart and find out what worked and what didn't work in terms of sending stuff into orbit. All of the previous launches had those engines completely fall apart or sink into the deep ocean in a state that is unrecoverable, so this kind of engineering analysis has been impossible. Even if the engines land in the water, a soft landing recovery in the ocean is going to produce some very valuable information that c

    • Recovering the first stage (not this time but maybe this year) will make a huge difference in cost. Saving the 9 engines on the first stage alone is huge.

      Maybe, maybe not. The recovery infrastructure and labor isn't free, nor is the refurbishment infrastructure and labor. In theory the cost difference should be huge, in practice... we don't know. Nobody has ever refurbished and reflown liquid engines that have been dunked in salt water. AFAIK, we don't even have enough hard data to make a proper evalua

      • by ColaMan (37550)

        If I were SpaceX, the first thing I would have done is tossed an engine in the water, recovered it, and studied it. Landing legs and cushioned landing are sexy and the whole process is very impressive on paper to the less well educated space fanboy (I.E. 99% of them)... but engine refurbishment is the key to the whole process.

        Well, the goal is to eventually land them on, er, land so that they don't get dunked. Then you end up with 9 engines and a first stage in fairly good nick with 5 minutes of flight time

        • Then you end up with 9 engines and a first stage in fairly good nick with 5 minutes of flight time on it.

          Given that they've recovered precisely zero engines after flight... that's something of an assumption.

          • Not yet, but certainly getting the space program out of exclusively governmental hands is a good first step toward cost reduction techniques like this.

            Rocket science has a successful legacy breeding technology that crosses over well. In the 60's, the Minuteman II's use of quad nand gate ICs reduced their cost to the point they could be used in commercial gadgets.

            A space vehicle becomes much more practical when it can land, refuel, and planet hop.

          • I'm pretty sure they've recovered the engine from the Grasshopper test vehicle after each of its seven flights.
          • There isn't really anything new going on here, its just never been put togther like this before.

            While NASA prefers water landings, the Soviets landed all of their equipment on the ground. So returning things to the ground isn't really that exciting. Additionally there were landing people (who are much more fragile than mechanical parts) from orbit rather than just high in the atmosphere.

            And while reusable engines didn't work out that great for the Space Shuttle for various reasons. Lots of rocket engines ha
          • by Teancum (67324)

            Then you end up with 9 engines and a first stage in fairly good nick with 5 minutes of flight time on it.

            Given that they've recovered precisely zero engines after flight... that's something of an assumption.

            I think the goal of this particular flight is to recover the engines of the 1st stage after the flight. I think that count is going to go up by a few by the end of next month. The goal is to do land recovery of the rocket eventually though, and to keep the service crew which refurbishes the rocket down to a minimum. As to if SpaceX will be able to accomplish that goal is certainly something to be skeptical about though.

  • Given the attention to video that SpaceX has given to their other activities, there's a good chance we'll get to see a video of this thing splashing down, depending on how precisely they can land it.

    • I look forward to is as well. Assuming it performs like the Grasshopper test platforms (which it really should, given that Grasshopper is basically just a Falcon 9 first-stage itself), they can bring it down, upright, to an accuracy of a few feet. Of course, that was from a much lower altitude than first-stage separation occurs at, and it probably won't have the fuel for braking thrust all the way down, but I still wouldn't be *that* surprised if they manage to make the incredible thing hover for a second before splashing. After all, without the upper stages and with the fuel mostly gone, the first stage is pretty lightweight... not a lot of inertia they need to counteract.

      The other amazing thing about all this is that it's pure experimentation. There's no risk, aside from costs, if something goes wrong with this experiment. The payload will continue on up to the ISS regardless of what the first stage does post-separation. By using a wet landing, they avoid the risk of damaging anything on the ground. This is a chance to purely try things out, and it costs almost nothing more than the launch (which NASA is paying for) already would. A fantastic opportunity to try their models in the real world!

      • by macson_g (1551397)

        The other amazing thing about all this is that it's pure experimentation. There's no risk, aside from costs, if something goes wrong with this experiment. [...]

        Well, not entirely. First: they add extra fuel for the braking burn (or reduce amount of fuel available for ascent). Second: the legs will change the aerodynamic, and maybe other characteristics of the fuselage.

        They did a braking burn before, so I assume 1. is already tested, but I wouldn't say that there is no risk.

        And that's why it's so exiting!

        • by Teancum (67324)

          There is reserve fuel that will be available if there is something like a RUD event with the engines or some other problem on the assent, so it is perfectly valid to be burning that reserve fuel supply upon descent. The main problem is that the recovery system eats into the payload part of the rocket equation (legs have mass), thus the efficiency and Isp suffer from the perspective of the rocket as a whole.

          Previous recovery systems have eaten so much of the payload that you essentially got a thimble into o

    • by Immerman (2627577)

      Indeed, and I'm looking forward to it. Finally we're approaching the towering inverted candles able to set down gently upon alien worlds that were so iconic in golden-age science fiction.

    • Speaking of cool to watch, I compete in dog agility, and the last show, a couple of weeks ago, was a couple of miles from Space X's range in Texas. They had two engine tests during the weekend, and even from that distance the noise rattled the arena we were in like an earthquake. A bunch of us would go running outside to watch the enormous cream colored clouds from the tests fill the sky near the horizon. BTW, some dogs totally freaked at the noise (and the sight of their nerd handlers bolting outdoors to s
  • How does this work? The rocket will have gone far down range before the first stage separates.

    * First stage reverses direction and comes back. Very fuel expensive, I'd be amazed if they're planning this.
    * First stage does one 'orbit' (technically it would still be 'sub-orbital') and returns to launch site from opposite direction. Requires that the stage has sufficient energy, and requires some cross-range maneuvering unless you launch from the equator.
    * Summary is incorrect, and stage landing site is not th

    • by TheSync (5291)

      First stage reverses direction and comes back. Very fuel expensive, I'd be amazed if they're planning this.

      I suspect parachute braking with fuel only used in the last few feet.

      • by Isca (550291)
        Once you've used up 80% of your fuel plus you have dropped the weight of the upper stages and the fuel/payload for them it's relatively light. Especially compared with how much thrust you can output. That 20% fuel is enough to dramatically change your direction and still leave enough fuel to steer yourself and land in an upright position.
      • A parachute doesn't solve the problem of your stage being hundreds of km downrange from the launch site. A parachute can help in any of my three proposed scenarios. (I think you'd need to jettison the parachute and drop for a bit before firing the rockets, because I don't think you want to try to land while attached to or entangled in a chute. This is what Curiosity did on Mars.)

    • Barge landing? Would have to take a lot of heat, but that's just engineering.

      • Nice idea, but they are landing something that looks like a pencil on its end. They need somewhere rock solid to put it down.

        • Bottom stage only. A stubby pencil.

          Barges go pretty large. Ballast the thing and it should be pretty stable in good weather.

          • by nojayuk (567177)

            I suggested Elon buys a second-hand aircraft carrier and uses that. It would solidify his James-Bond supervillain status and piss off Larry Ellison no end as a bonus.

    • by bledri (1283728) on Monday February 24, 2014 @10:15PM (#46330923)

      How does this work? The rocket will have gone far down range before the first stage separates.

      * First stage reverses direction and comes back. Very fuel expensive, I'd be amazed if they're planning this.

      That's exactly what they intend to do. They refer to it as "boost back." Fuel is cheap compared to the price of a rocket. Right now they are working on a fully reusable first stage and a capsule that lands under propulsive power. After that they'll work on the second stage returning (it can just complete an orbit instead of boosting back. Here's an animation they put out to show the concept. [youtube.com]

      Here's an article explaining the current status of the effort [nasaspaceflight.com] and what they hope to achieve with this test.

      • OK, so I'm officially amazed.

        Fuel is cheap when it is sitting in a tank on the ground. Fuel at 100 km altitude and 5km/s speed is a very different story. Fuel which you keep in stage I for 'boost back' is fuel you aren't using to put your payload into orbit, meaning you have lower maximum payload.

        • by ColaMan (37550)

          It seems that the quantity of fuel required to fly an nearly empty 1st stage is negligable. That is, the amount that they normally leave behind as reserve in case of issues getting to orbit is enough for the 1st stage to land with - you basically just fall/parachute as far as you dare and then fire the engines at the last second to steady/cushion the landing.

        • Of course you are going to have less payload with a reusable rocket. The whole idea is that the launch cost per kg will be lower and you use more launches to get the same mass up. Or build a bigger launch vehicle. The problem is if you get zero or negative payload in the process...

          • I'm not comparing non-reusable rocket to reusable rocket. I'm comparing reusable rocket which returns to launch pad with reusable rocket which lands downrange of launch pad.

        • by Anonymous Coward

          The improvements in the Merlin 1D give Space-X a higher payload fraction in the Falcon9 v1.1 or extra fuel they can use for reusing the first stage.

        • by tp1024 (2409684)

          Well, they want to sacrify about 20-30% payload (out of about 16 tons) to do the flyback. They also separate the first stage at Mach 6, or 1.8 km/s. But that's after leaving most of the atmosphere behind and overcoming a lot of the gravity losses during launch. So the actual energy budget is better than it seems to be. Still, the second stage has to do more work than it normally would - some 6km/s are left. About 5/6th of the second stage, including payload, must be fuel. But the engine weighs less than 700

  • I've watched the grasshopper videos countless times, but let me get this straight.

    This time, the landing legs will supposedly be actuated. They'll fold out just before "landing". I don't think they've done this before, or at least it didn't look like it from the videos. Cool.

    This time, they'll be "landing" on water instead of the launchpad. I wouldn't call it landing if it's not on land; they'll be ditching into the ocean. This makes sense, as this is a real mission for a paying customer, not some eng
    • by bledri (1283728)

      This time, the landing legs will supposedly be actuated. They'll fold out just before "landing". I don't think they've done this before, or at least it didn't look like it from the videos. Cool. ...

      Now, this is all awesome stuff, but I can't help but wonder... What good are landing legs when you're landing in the ocean?

      ... I just don't understand what the landing legs are for.

      They are doing this to collect data with the goal of eventually boosting back and landing near the launch pad for rapid reuse. The legs actually do help, they reduce aerodynamically induced spin and the terminal velocity. But mostly this is a test so they can gain confidence to return to land.

    • by Cytotoxic (245301)

      On the last test the stage began to spin too rapidly and the engine shut down because the fuel was slung out of reach of the fuel intake. This time they will have the legs attached which helps with stability on the way down. The water part is just for safety - if you lose control during a landing in the middle of the ocean you crash in the middle of the ocean. Losing control on the way back to Canaveral and crashing into Cocoa Beach would be bad.

      • by tibit (1762298)

        They could probably sell the scrap to collectors and recover a good chunk of the material costs at least :)

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