SpaceX Successfully Lands Its Rocket On A Floating Drone Ship For The First Time (theverge.com) 206
An anonymous reader quotes a report from The Verge: SpaceX has finally landed its Falcon 9 rocket on a drone ship at sea, after launching the vehicle into space this afternoon. It's the first time the company has been able to pull off an ocean landing, after four previous attempts ended in failure. This is the second time SpaceX has successfully landed one of its rockets post-launch; the first time was in December, when the company's Falcon 9 rocket touched down at a ground-based landing site in Cape Canaveral, Florida, after putting a satellite into space. Now that SpaceX has demonstrated it can do both types of landings, the company can potentially recover and reuse even more rockets in the future. And that could mean much greater cost savings for SpaceX.
Dear lazy web (Score:2)
Dear lazy web, any higher quality video out there?
Congrats SpaceX, this looks really impressive.
Re:Dear lazy web (Score:5, Informative)
Dear lazy web, any higher quality video out there? Congrats SpaceX, this looks really impressive.
https://www.youtube.com/watch?... [youtube.com]
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Thanks a lot.
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Slashdot is slipping. (Score:2)
It didn't even mention that SpaceX was launching today.
Whoo-hoo... (Score:2)
Now we just order the drone ship back to port! ...
Uhh... that wasn't a story in the epic
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Video Here. Starting at 35:30 for Real Joy (Score:2)
https://www.youtube.com/watch?... [youtube.com]
That came in at a pretty steep angle (Score:5, Interesting)
Anyone know why they would come in at an angle and straighten up at the last moment? Is it actually easier to control that way, or is it to protect the landing pad in case of a list-second abort?
Re:That came in at a pretty steep angle (Score:5, Interesting)
There are two reasons that I've seen.
Because the rocket is almost out of fuel, even burning only one engine at minimum throttle, the thrust to weight ratio is more than one (ie, the rocket would fly, not land). So, they can't hover, they have to hit the ship and shut the engine off at the exact moment that the velocity is zero (or very close to it). So, to help with that problem, they come in at an angle which helps consume at least some of the thrust in a direction that isn't upward.
The second reason is, as you say, to protect the landing platform. If they run out of fuel (or the engine fails or....), the stage just drops into the ocean rather than crashing into the barge at a very high speed. That said, based on their last several failed landing attempts, that barge can take quite a hit and stay in one piece....
Re:That came in at a pretty steep angle (Score:5, Informative)
There are two reasons that I've seen.
Third reason: Wind. In the post-launch press conference, Elon mentioned that the wind was significant during landing. (And may reach up to 50mph tomorrow on the way back to port.) So the rocket had to tilt somewhat into the wind to avoid being blown sideways relative to the landing pad, and only went vertical at the last moment. It also explains why the droneship maintains a slight tilt in some of the post-landing footage; this is to cancel out the considerable force of the prevailing wind.
Re:That came in at a pretty steep angle (Score:5, Informative)
It looked like pretty rough seas, too. The next step is that someone goes on the barge and welds shoes over the landing gear to hold it to the deck. There may also be something that fastens to the "octoweb", the frame that holds the engines at the bottom of the first stage.
Believe it or not, welding something to the steel is fast, and easy to un-do. You just cut it off with the same welding equipment, and use an angle grinder to remove the bead.
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As a universal rule, on your way back down to a planet, you want to to apply maximum force for a short of a time as possible and at the last second possible. Anything you do to slow your descent before that means that you're fighting gravity for a longer time, and that wastes fuel. They don't have the resources to change their approach angle--and even if they did, shallow means it's hitting more air resistance on the way down, which means you slow down for free.
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Because they have to control vertical *and* horizontal velocity. Simple as that.
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This is a Really Big Deal, And More to Come (Score:5, Informative)
Obviously now we have to see the recovery percentage that SpaceX can achieve, especially when they start landing Falcon Heavy on three barges, the one for the center booster being much farther downrange than the others. Seeing three land, two of them simultaneously, is going to be pretty amazing. If they can recover a lot of them, this completely changes the economics of space flight beyond the 30% discount SpaceX is quoting in the short term.
And don't forget that they are getting the Dragon back too, and Dragon 2 with its eventual ground-landing capability is expected to be reusable. Currently Dragon 1 lands in sea water, and the reuse they have so far is only of the pressure vessel, the capsule is stripped down to that and rebuilt.
Recovering the second stage is possible although not currently on the SpaceX roadmap. They would need to fly it with a heat shield.
Now, consider what it would take to land a Dragon on the moon and return. Not inconceivable, given Falcon Heavy and a few launches.
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From what I've read, the side booster stages of Falcon Heavy will always be able to make ground landings; they don't go nearly as far or fast as the central stage. I'm sure it still costs some payload to go for the ground landing with the side boosters, but not nearly so much. The central stage, though... that burns for a considerable while after the side boosters detach (it spends much of the flight at low throttle, plus there's the whole propellant crossfeed thing, assuming they ever get that working), an
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SpaceX has stated that about 30% of rockets launched overall will be able to RTLS. That's why the barge is so critical. F9 Heavy will only be able to RTLS depending on the total delta-V demanded for the mission. There is a delta-V cost for RTLS, you can't just do it on the grid fins.
Big push to engine improvement too! (Score:2)
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Exactly - not throwing everything away has advantages. SpaceX deserves to be congratulated for pulling this off. There's lots to be said for incremental improvement.
Artillery versus Airplanes (Score:2)
That's the analogy to think about with this. When is it best to use the artillery approach, and when is it best to use an airplane approach. An airplane approach implies refueling and re-use. You can amortize investments to improve capabilities over time. Artillery is all about cheap getting payload up there.
If you really want to get pure mass to LEO cheaply - it's hard to beat big artillery with a rocket stage. It has a few issues though.
Your payload has to be able to handle the G's from firing. The
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A rock is a larger more masculine form of a rockette.
https://en.wikipedia.org/wiki/... [wikipedia.org]
Re:Economics of that stunt are dodgy (Score:5, Informative)
Re: Economics of that stunt are dodgy (Score:2)
Re: Economics of that stunt are dodgy (Score:4, Insightful)
Most of their launches don't require the full payload capabilities of the rocket. If they're not going to use the extra payload mass anyhow, how does that reduce revenue?
Re: Economics of that stunt are dodgy (Score:5, Informative)
That's not really how rockets work. Sometimes a launch profile is compatible with secondary payloads, and so they sometimes do that. But often they're not, and so you can only launch to the one orbit. SpaceX doesn't control the satellite manufacturers operators: if the payload doesn't need the full payload, they can't just stick another satellite in there or tell them to make it bigger. If they could be putting additional payloads in the rocket to derive additional revenue, they would be. When they do the Orbcomm launches, they're launching lots of satellites at the same time, but then, those satellites all launch into very similar orbits.
Reusability on the first stage doesn't add terribly much weight anyhow: it takes a lot less fuel to decelerate a mostly empty stage than it does to accelerate the whole thing up to speed in the first place. It's also not a 1:1 relationship: 1 kilo of extra fuel does not subtract 1 kilo of mass from the potential payload. That would be true of the second stage, but not the first stage.
Since they can't really use that extra capacity anyhow, they might as well use it for cost savings, because reducing your costs is even better than increasing your revenue.
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Second, by this particular compromise in capacity they're trying to get both lower costs per launch and higher reliability of operation. There are some very significant benefits to this, if they can get it to consistently work.
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For serious Mars travel, even unmanned, you want to get a big rocket into Earth orbit, then top-up the fuel tanks before accelerating towards Mars.
No, you wouldn't. Because now that big rocket launch is a single point of failure for your mission. Further, thrust per mass is not that important once you have a vehicle in orbit. What took a lot of thrust to lift off of Earth can be moved with a much smaller rocket engine in space, even considering the Oberth effect and crossing of the Van Allen belts.
So many payloads can be adjusted to match the max payload.
Those payloads can also be adjusted to cheapest cost per unit mass too.
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So, when you get to your car to drive to work in the morning, you load up every last pound of unused capacity with trash and dump it at the dumpster behind your office? If you don't, you have an operational problem at the outset. You should have bought a much smaller car, and kept your weight tightly controlled.
Re: Economics of that stunt are dodgy (Score:2)
Re:Economics of that stunt are dodgy (Score:5, Informative)
You are simplifying it to such an extent that you completely miss the point. The cost of the fuel is a small fraction of the cost of the launch - the cost of building the 1st stage dominates. When that stage is destroyed, it is an operational expense for that launch. When it is recovered, it is a capital expense with an additional smaller operational expense to refurbish and another expense to account for the reduced efficiency of the launch (some fuel held in reserve as you say).
Since converting the huge operating expense into a a huge capital expense that results in an asset that can continue delivering value minus some small additional operating expense, the net result is a more economic system.
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Since converting the huge operating expense into a a huge capital expense that results in an asset that can continue delivering value minus some small additional operating expense
And since capital equipment /always/ has a depreciation, you can write off the depreciation instead of watching it burn up in the atmosphere.
And then you can sell the capital equipment to some other sucker.
--
BMO
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And since capital equipment /always/ has a depreciation, you can write off the depreciation instead of watching it burn up in the atmosphere.
Surely the burning-up-in-the-atmosphere approach qualifies as accelerated depreciation?
Re:Economics of that stunt are dodgy (Score:5, Informative)
All rockets fly with lots of margin (read: extra fuel) in case of unexpected anomalies during flight. The difference with SpaceX is, when the flight goes as planned, they can use that extra margin to recover an immensely expensive piece of hardware. What's more, not all payloads are using every last pound of capacity in the vehicle. If you can launch 90% of the weight at half the cost thanks to reuse, you've fundamentally changed the market.
This is like getting to reuse a Boeing 747 instead of scrapping it after a single flight. If you think that's just a stunt, you don't have much of an imagination. This is a game changer.
Re: Economics of that stunt are dodgy (Score:3)
If that was the case, then why have their competitors shown interest instead of mocking it?
Re: Economics of that stunt are dodgy (Score:5, Insightful)
Blue Origin has been mocking them in the other way. "Hey, look at what we just did! What took you so long?" Sure, you had a sub-orbital launch profile (almost no horizontal velocity), popping off a tin can that came straight back down. Boy Scouts recover their Estes rockets all the time. SpaceX already did the landing thing with their Grasshopper rocket (and DC-X long before either of them), and the only reason they didn't take it higher was because they didn't have clearance to go higher at McGregor.
Falcon 9 has been on an orbital launch profile every time, sometimes even GTO, which is a lot harder to come back from. Even hitting the drone ship and falling over was harder than what Blue Origin did. A side-effect of having an actual useful launch profile is engines that can't throttle down to hover (Blue Origin can), so they have to do the much harder "hoverslam" maneuver. (zero vertical velocity at the same moment as zero altitude)
I will, however, give Blue Origin a few points for doing quick turnarounds. Their short-term objective is space tourism, and they're doing exactly what they need. It's just not nearly as hard as what SpaceX is trying to do.
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While he did not mention Blue Origin by name, Elon made a point of mentioning how difficult it is to cope with high speed horizontal velocity.
Blue Origin just isn't playing in the same league yet.
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What part of fine control did they lack? Processing? Sensors? Engines?
Re:Economics of that stunt are dodgy (Score:5, Informative)
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Quite true, although it should also be noted that the ratio you provide isn't going to be the ratio of savings they get. There are fixed costs associated with turning the stage around, so the cost of re-use isn't just the fuel, but it's also the labor to haul the stage back, pay the boat crews, re-inspect the engines, etc.
It's still a major win even considering those fixed costs. Many predictions are coming in around the 1/4 to 1/2 mark relative to a brand new stage. That's SpaceX's savings: they have th
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60M is their entire rocket..... There are 3 parts to the rocket and their original (and still current) goal was for FULL re-usability. Since 33% of the rocket = 1/3, that completely matches up what they originally stated since you have to account for recovery, refurbish/inspection, and relaunch cost.
It's a long process and even SpaceX acknowledge early on the 2nd stage was more complex to recover and may not be possible. That said, the dragon capsule is slowly on it's way to re-usability so even if they don
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Re: Economics of that stunt are dodgy (Score:2)
Re:Economics of that stunt are dodgy (Score:4, Informative)
The only accurate point in your post is that second stage landings may not prove practical, which is why there are no current plans to attempt that. Fortunately the second stage is a lot cheaper than the first stage, in this case the second stage is just one engine compared to 9 in the first stage.
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The only accurate point in your post is that second stage landings may not prove practical, which is why there are no current plans to attempt that. Fortunately the second stage is a lot cheaper than the first stage, in this case the second stage is just one engine compared to 9 in the first stage.
Even if they can't recover the second stage, if they can get reliable recovery/refurbishing/reuse of the first stage that'll completely change the economic equation. Say you can reduce the second stage cost by $1m by increasing the first stage cost by $1.2 million, today you won't do that because it's a net $200k loss. If you can reuse the first stage once for neglible fuel costs it becomes a (2*$1m - $1.2m)/2 = $400k profit per launch. If they can do it five or ten times, it's even more profitable. So I th
Re:Economics of that stunt are dodgy (Score:5, Insightful)
Even if they can't recover the second stage, if they can get reliable recovery/refurbishing/reuse of the first stage that'll completely change the economic equation. Say you can reduce the second stage cost by $1m by increasing the first stage cost by $1.2 million, today you won't do that because it's a net $200k loss. If you can reuse the first stage once for neglible fuel costs it becomes a (2*$1m - $1.2m)/2 = $400k profit per launch. If they can do it five or ten times, it's even more profitable. So I think there's a lot of potential improvements just redesigning to take maximum advantage of first stage reuse by making the second stage do less and cost less.
Also worth pointing out that those first-stage engines will have a limited number of flights they're good for. So on it's last flight, you stick the engine in a second stage. After all, you've got to get rid of your expired engines somewhere, so they may as well go in a second stage as a junkyard somewhere.
Each "time's up minus one" first stage yields nine expendable second stage engines, sorta kinda for free.
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Also worth pointing out that those first-stage engines will have a limited number of flights they're good for. So on it's last flight, you stick the engine in a second stage
The second stage engine has a different design, because it's optimized for operating in vacuum. I think a better plan would be to launch the first stage as disposable when the engines are getting near the end of their life, and use that disposable launch for a heavy payload.
Re:Economics of that stunt are dodgy (Score:5, Insightful)
For the Merlin 1C, the only difference with the vacuum (second stage) version is the nozzle - a much larger expansion ratio. Other than the nozzle, they're the same engine.
The Merlin 1D variant is more deeply throttleable on the second stage, but it's unclear whether this is just a configuration setting or substantive hardware differences. I would imagine the former as much as possible.
But in any event, we concur -- lots of useful things to do with engines on their last flight.
Re: Economics of that stunt are dodgy (Score:2)
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There are other goals than fuel efficiency. And really, given how dirt cheap kerolox is, optimizing for extreme fuel efficiency (especially on a first stage) is something of a fool's errand.
o.0
Reflying/reusing something is, with rare exceptions, always going to be cheaper than building a new something. The only real question is, h
Re:Economics of that stunt are dodgy (Score:5, Insightful)
. . It is not obvious that doing this risky vertical landing is going to result in any savings at all. . . This is interesting but looks like a stunt.
I'll bet on the SpaceX engineers anytime over a random commenter on /. (regardless of the UID)
Do you really think that they haven't run the sums before spending all that time and effort perfecting something that you call "a stunt"?
Do the math..... (Score:3)
The first stage costs $60 million to build.
The fuel costs $200,000 -- do the math.
I mean, if you don't mind $60 mil coming out of your pocket. The point is, re-use of the first stage enormously decreases costs per pound to orbit. If you can't figure that out, then I'm sorry, but, what are you doing on Slashdot?
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Re:Economics of that stunt are amazing (Score:5, Informative)
I was gonna mark the parent as a troll, but really it's just uninformed.
https://science.slashdot.org/s... [slashdot.org]
Elon Musk says it takes $60 million to build the Falcon 9, and $200,000 to fuel it.
Steve Poulus, a former NASA project manager, suspects final costs could be driven below a million dollars.
So it's looking like a stunt that could be worth more than 95% of the first stage's $60M. That seems like a big deal.
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More physics than economics, and it checks out (Score:5, Interesting)
SpaceX, and the people in this thread, are comparing the vehicle cost to fuel cost, which is kinda cheating. It's not the cost of the fuel that matters, it's the cost of building the vehicle larger to hold that fuel -- and the fuel needed to launch that fuel -- that matters. So let's do the math!
Most data taken from http://spaceflight101.com/spac... [spaceflight101.com]
Basic info:
Stage 1: 23 tonnes structure, 400 tonnes fuel
Stage 2: 4 tonnes structure, 93 tonnes fuel
Payload: 13 tonnes
When launching, the first stage burns all 9 engines at full thrust for two and a half minutes. The re-entry burn and landing happen on a single engine, and from eyeballing the videos (including this one [youtube.com] that shows the re-entry burn) appear to take about 30 seconds total. Assuming all burns are near full thrust (which is the best way [wikipedia.org] to do it), that means the landing burn takes about (1/9) * (0:30 / 2:30) = 2% of the first stage fuel. Let's double that to 4% to provide a generous safety margin: that works out to about 400 * 0.04 = 16 tons more fuel.
This fuel is carried up to the moment that the second stage separates, so it subtracts from the mass of the second stage. Second stage plus payload weighs 110 tonnes: without the landing fuel, you could have scaled that up to 126 tonnes, a 15% increase.
So, landing the first stage reduces the payload SpaceX can launch, and thus the money they earn, by about 15%. In exchange, they recover about 75% [shitelonsays.com] of the cost of the launch hardware. So it's worth doing, even after you subtract off the cost of recovery and refurbishing. Maybe not the game-changer Elon Musk wants it to be, but it's a win.
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You make a very good point for, say, satellite delivery, where being in space at all is much more valuable than how many pounds the satellite weighs. But for ISS resupply, what NASA cares about for its COTS program is total tonnage reliably delivered. And SpaceX's stated goal has always been reducing the cost of bulk cargo delivery, with "dollars per pound" as the metric of success.
Re: More physics than economics, and it checks ou (Score:2)
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Actually, pulling something out of orbit takes a *lot* less fuel than putting it there in the first place - you don't have to stop, you only have to include a heat shield and slow down just enough so that the opposite side of your now-elliptical orbit intersects the Earth's atmosphere. Air resistance is your friend. After a pass or two you're pretty much at first-stage velocities, and your craft is a lot lighter than the first stage as well.
Also, reentry is pretty much already standard for orbital vehicles
Re:Drone ship (Score:5, Informative)
It's automated. No humans aboard. That fits the commonly accepted definition of drone.
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Re:Drone ship (Score:5, Informative)
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That's the term SpaceX uses.
that's history, get the details right. (Score:4, Informative)
Re:"Now that I got a strike, I can win at bowling! (Score:4, Insightful)
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They change the process after every flight, if the telemetry tells them they could have done something better. Just like they enabled the Dragon's parachutes during ascent on this flight, in case the rocket blew up. (The previous flight the 'chutes were disabled on ascent because it was assumed an explosion would be non-survivable, so when the Dragon capsude did survive the explosion, it was destroyed when it hit the water.) The odds of that making a real difference on any upcoming flight is minuscule, b
Re:"Now that I got a strike, I can win at bowling! (Score:5, Informative)
Uh... yes. They've changed the volume of on-board hydraulic fluid, they changed the leg lock-out mechanisms, they changed the landing approach angle, and probably a billion other things. Do you even follow SpaceX bro?
I'd go out on a limb and say they will probably stick 8 out of the next 10 sea landings, and no less than 9 out of 10 RTL landings.
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I'd go out on a limb and say they will probably stick 8 out of the next 10 sea landings, and no less than 9 out of 10 RTL landings.
Spoken like a pointy haired boss in training...
FWIW, I'll go out on a limb and say that that given the percentage of recovered first stages is integral to SpaceX profitability, Elon Musk probably would know better than most and he apparently has stated publicly that last time when he predicted a 50-50 chance of sticking the landing, that he pretty much made it up and he had no idea...
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First of all, they don't have to do it consistently just enough to matter. Every success is a win, every failure a cost of doing business. The real question now is, how big is the refurb effort. After all they've landed... twice. They've relaunched... zero. And if they can keep doing that, I mean once is nice but... if they can do it five times, ten times that's when you really start to spread the initial cost across lots of launches. It'll be interesting to see what's possible, also hopefully by the end of
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About half their issues have been fixable engineering problems, and the other half have been bad luck, so their success rate from here on should be about 50%.
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After a couple hundred tries (yes, I suck), I finally got a strike! Now that I did it, I can go on to win all the bowling trophies ever!... said no sane person ever.
Yeah. Those are totally the same thing.
This is more like lining up the ball rolling thing that kids use, seeing where the ball goes, then adjusting your aim based on the result until you get a strike, at which point you screw the ball rolling thing into the floor.
Did they actually change the *process* they use
Yes. You think they just watched the others explode, shrugged, and said, "Huh. Okay, do exactly the same thing again, it might work this time"?
Or are they just getting better at the process they already had, due to practice?
Uh... I'm not sure what you think is going on here. Do you imagine there's some guy called Steve guiding
Re:"Now that I got a strike, I can win at bowling! (Score:5, Informative)
Afaict they have attempted landings* on 6 flights of those two were successful.
Flight 14, failure due to grid fins ran out of hydralic fluid.
Flight 17, failure due to stuck valve
Flight 20, successful landing at the cape
Flight 21, failure due to landing leg issue
Flight 22, failure (and was expected to fail) due to coming in too fast due to a large payload.
Flight 23, successful landing on
So basically the devil is in the details. Each time a failure happens i'm sure they put a lot of effort into working out the details of what went wrong but what is not clear is how many iterations of failure they will have to go through before they get a reliable result.
One thing I would note is that they don't need 100% reliability. They just need sufficient reliablity to make the savings from reuse greater than the cost (payload reduction, landing location operations and repairs etc) of the landing,
* Defined here as attempting to land etiher a landing pad on land or a droneship. I don't count the drop in water tests as landing attempts.
Re:"Now that I got a strike, I can win at bowling! (Score:5, Funny)
They've actually landed successfully on land prior, this was their first success on a ship at sea. The last attempt it landed, then tipped over when a support leg broke, so i'd guess they reinforced that or something. I'm sure they'll have a few more fireballs, but my money is on them getting the landing down consistently very soon.
When I first started SpaceX I wanted to land a booster in the ocean. Everyone said I was daft to try to land a booster in the ocean, but I built in all the same, just to show them. First time, it crashed into the ocean. So I built a second and third one. They sank into the ocean as well. So I built a fourth. That landed, fell over, then sank into the ocean. But the fifth one stayed up. And that's what you're going to get folks, first stages that land on autonomous barges with weird names in the middle of the ocean.
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She's got huge.... tracts of land, perfect for landing rockets.
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Are you trying to spell Cthulhu? If so, back to the drawing board.
Re:Why Better than Parachute? (Score:4, Insightful)
Ditching it in the sea and recovering it causes too much damage to make it viable to refit. This was intended for the boosters on the space shuttle, but it ended up being cheaper to make new ones than fix the old ones.
Of course they could bring them down over land, but I think the unpredictability of exactly where they would land could be marginally terrifying.
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The damage is caused by the salt in the water. Missed that out!
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Of course they could bring them down over land, but I think the unpredictability of exactly where they would land could be marginally terrifying.
They already did a landing on land back in December. The landing site (ocean or land) depends on where the rocket is going. If it needs to reach high orbit like the ISS the 1st stage does not have enough fuel to go back to shore and they do an ocean landing.
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I meant bringing them back with parachutes. A burn back is much more controlled.
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Generally correct, except that this launch was to the ISS, which happens to be in a very low orbit to make it easy to rendezvous with it. But yes, it takes a lot more fuel to launch to something like GTO, so less fuel left to turn around and get back to the cape, so they have to land on a ship in the ocean.
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I thought they did refurb the SRBs.
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Re:Why Better than Parachute? (Score:5, Informative)
Seawater and final impact speed are two good ones.
Seawater inside a booster makes refurbishing it MUCH harder. With parachutes, you can't control the attitude at which the booster hits the surface, and those rockets are designed to be very strong for vertical loading, but horizontal loading would destroy it... like a beer can, it can support a load at it's top, but not it's side.
Keep in mind that they have to fly with that fuel anyways... they need the margin in case of engine failure or other recoverable scenario. So all they've really done is add the weight of some landing legs, fins, a few other sundries, and some intelligent flight computers to relight the engine and bring it back down... it's not as inefficient as people are making it out to be.
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The payload cost of reusability is much more that you are saying. From wikipedia: [wikipedia.org]
In order to make the Falcon 9 reusable and return to the launch site, extra propellant and landing gear must be carried on the first stage, requiring around a 30 percent reduction of the maximum payload to orbit in comparison with the expendable Falcon 9."
(That is a return-to-launch-site cost, not a land-on-barge cost, which I didn't find a value for and must be a fair bit lower.)
And from here: [wikipedia.org]
SpaceX has indicated that the Falcon Heavy payload performance to geosynchronous transfer orbit (GTO) will be reduced due to the addition of the reusable technology, but would fly at much lower launch price. With full reusability on all three booster cores, GTO payload will be 7,000 kg (15,000 lb). If only the two outside cores fly as reusable cores while the center core is expendable, GTO payload would be approximately 14,000 kg (31,000 lb).[39] "Falcon 9 will do satellites up to roughly 3.5 tonnes, with full reusability of the boost stage, and Falcon Heavy will do satellites up to 7 tonnes with full reusability of the all three boost stages," [Musk] said, referring to the three Falcon 9 booster cores that will comprise the Falcon Heavy's first stage. He also said Falcon Heavy could double its payload performance to GTO "if, for example, we went expendable on the center core."
(Not clear if this is return to launch site or land on barge.)
Note that I'm not saying this makes it uneconomic. If you have a source to show that contingency fuel (e.g. to accommodate a failure of one engine during launch) is of the same order as fuel requirement to land the stage, plea
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The Shuttle SRB casings were 8mm thick steel in order to withstand crashing into the ocean. The F9 skin is in the region of 0.4 mm aluminium. The Shuttle SRB had a fuel fraction of only 80%.
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All the following is speculation.
They'll have people on the barge within perhaps 30 minutes of landing. They can hose stuff down with fresh water, then put a tarpaulin over the engines. All the delicate stuff already has to be protected from hypersonic travel through atmosphere, so is probably pretty well protected.
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Also because you cannot use parachutes on Mars. SpaceX plans to eventually land on Mars, refuel and then take off to return to Earth.
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I thought they *did* use a chute on Mars to put the rovers down? That and bouncy balls.
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The atmosphere on Mars is roughly 100 times thinner than on Earth so you can use a parachute to slow you down but only to a limited extent. The largest supersonic parachute ever used was foe the Curiosity rover mission. Good video here [wikimedia.org]. Not practical for a manned mission due to the snap of the parachute opening at that speed(9 Gs) would break necks. It only slowed the rover to 320 kph and needed a rocket to land.
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Chutes were used on all the missions for some of the deceleration but rockets were also needed after the chutes for final deceleration. Mars Pathfinder also had bouncy balls (airbags) for the very end. Mars is tough to get anything heavy onto (in one piece) because the atmosphere is too thin to use a parachute all the way down, but it is thick enough to cause problems with lighting landing rockets at supersonic entry speeds (that last, about the rockets, I was told and don't have a handy reference).
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For the Dragon capsule, they're still intending propulsive landing. To me this seems a less clear cut decision than for stage I.
When manned, the Dragon needs both parachutes and rockets whatever landing scenario you have in mind, because you need to allow for abort on launch (rockets to get away from misbehaving lower stages, parachutes to land safely.) A parachute landing is likely to have a sideways velocity component, but this is much less critical for the short Dragon than the very tall stage I.
I'd have
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I'm sure they've already thought of this and declined to try it for good reasons but nobody has explained the reasons to me why they don't use a chute for part of their decent, drop it at a certain altitude, and then use the remaining fuel for the controlled burn during the landing stage.
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Yeah once it has been in the water it has to be rebuilt, rather than fueling it up again and lighting the fuse.
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Car analogy: instead of hitting the brakes to stop before you crash into the brick wall, why not inflate an air bag and swerve into the nearby lake instead? Because the air bag doesn't really protect very sensitive parts and once you get water in the engine you can't trust it ever again.