SpaceX Has Pinpointed the Problem That Caused the Falcon9 to Crash Land

Indeed. They attempted to recycle a garbage rocket after it had been used already.

This crash into the ocean thing. That happens on literally every single other rocket launch in history, it's not abnormal, it's just not usually filmed or even thought about much.

> That's easy to fix, although it means some weight penalty.

It's probable that they use RP-1 as the hydraulic fuel and then dump it after use into the main RP-1 tank. In this case, assuming they don't need more high-pressure fluid than they need braking fuel, there is no weight penalty.

One of the annoying aspects of coverage of SpaceX's attempts, although fortunately it's fairly rare, is the desire to make fun of "eggheads" when they "fail" because it makes people feel superior.

Nevertheless, this work is one of the most important things going on in human civilization right now. That may seem like a bit of hyperbole, but go back and look at things like the invention of the transistor or the internet. Nobody perceived fully how impactful either of those things would be though they've transformed the lives of billions and spawned trillions of dollars in economic activity. If reusing rockets becomes feasible, and there's every reason to believe it will be, then it will lower the costs of spaceflight by one to two orders of magnitude right off the bat. And that will vastly accelerate our investment, colonization, and exploration of space and kickstart a positive feedback loop of growth in activities in space (from infrastructure like GPS and commsats to human presence) spurring investment in improving space and launch systems which then increases activity levels (due to increasing capabilities and lower costs) which then spurs improvements, and so on. Ultimately culminating in mankind becoming not just a multi-planet species but a space faring civilization no longer confined to either the Earth or even this Solar System. And all of that will have grown from the tiny kernel of spaceflight activities in the present, with SpaceX's activities being particularly relevant for that future.

Here's two more with the rocket actually visible and nearly upright - https://twitter.com/elonmusk/status/555978908554625025, https://twitter.com/elonmusk/status/555980855537975296

It's from the exchange between Carmack and Musk - https://twitter.com/ID_AA_Carmack/status/555946079175208963

Gif: http://img.gfx.no/1477/1477615/spacex2.gif (source, norwegian article: http://www.tek.no/artikler/se-spacex-raketten-kraesjlande-pa...)

It's amazing that there were able to catch the needle in the storm.

vine video of the crash https://vine.co/v/OjqeYWWpVWK

So you're complaining that they're being disingenuous by describing their mission as a partial success instead of a complete success? Really?

This is where the concept of secondary objectives comes in.

From one of his tweets:

> Hydraulics are usually closed, but that adds mass vs short acting open systems. F9 fins only work for 4 mins. We were ~10% off.

https://twitter.com/elonmusk/status/554023312033341440

You can do away with the pump, pipes, and power supply.

Since the main propulsion isn't going, closed hydraulics would have to have an independent power supply. Probably batteries. Instead, they replace all that with some compressed air. They can run out of compressed air, but can also run out of whatever powers the pumps in a closed system.

The hydraulic fluid is probably RP-1 and is probably dumped into the fuel tank, where it's available for later burning. Another 2-for-1.

Detailed speculation on Reddit: https://www.reddit.com/r/spacex/comments/2s1lq9/my_guess_abo...

An open hydraulic system is more lightweight.

You mean like in most every other launch? If this works that will end, I'll cut them a little slack.

> Why is it acceptable to leave thousands of pounds of scrap and chemicals in the ocean?

Because in the quantities caused by spaceflight, its negligible. You should be far more concerned with the bottom trawling for seafood and plastics buildup from everyday consumers.

Most of the rocket is made of metal, which sinks.

First, "hard" landing doesn't necessarily mean "high speed". It's a generic term for unsuccessful landing. It could be incorrect attitude landing (e.g. tilted) or anything else. In this case it looks like it was exactly that: landed tilted or with significant horizontal speed. If it was high vertical speed, we would've seen big scrapes on the platform's surface, and there's none.

Contrary to popular belief, the fins are _extremely_ effective even at low speeds. First, they have enormous surface area. Secondly, they have huge momentum around the center of mass, which is at the very bottom of the rocket when it's empty. So, even a small force generated by the fins generates huge momentum and can help position the rocket in the desired attitude.

It looks like the control system was commanding the fins to move and was expecting the attitude to change, but they didn't move anymore. Perhaps at the very end of the flight the gimbals on the engine didn't have enough authority to orient the rocket vertically and/or arrest its horizontal speed.

I think it's amazing achievement for the very first attempt. Congrats SpaceX and I'm jealous like hell for what you've been able to achieve.

Oddly, if it was a 'stupid' mistake I'm pretty sure they would own up to it.

But lets look at what the these things do. During descent they provide control authority over roll, pitch, and yaw of the lower stage. Even though the center of gravity is near the bottom the rocket, the system is trying to keep it vertical. It is travelling down range and needs to go from moving sideways, to coming straight down. Earlier versions of Grasshopper used hypergolic thrusters on the sides but they were scrapped in favor of the fins system. So once you run out of hydraulic fluid, you're limited to the ability to gimbal the Merlin engines for controlling pitch and yaw.

If you watch the video you can see that the fins are used all the way to the point where it lands.

So my guess is they knew they were going to run out of hydraulic fuel and brought the rocket in "hot" (at a higher than planned approach speed) and didn't manage to get close enough before the fins stopped working.

If that really was the only thing that didn't work correctly, then we'll know on the 29th.

If the grid fins were stuck in an unhelpful position, then the engine would have to compensate much more significantly, reducing the trust available in the 'slowing down' vector.

It's also likely that 'hit hard' just means it crashed. Looking at the pictures of the ASDS, it's clear the rocket came down off-center. Perhaps it was at the appropriate velocity, but because it landed on top of a bunch of support equipment, it fell over and exploded.

Check out the trajectory diagrams on this: http://i.imgur.com/xH53djU.png

(Not mine, but seems about right.)

The fins failing created extra work for the final burn, which it couldn't quite handle.

If you can't orient your rocket correctly you're going to have a hell of a time getting it to slow down to the correct speed while also maintaining the correct position for touchdown.

I'm not sure how the waffles help with that, but I'll believe the article if they say it's used for steering/rotating.

"Needed"? The rocket has maneuverability without them, sure. Just as your car has maneuverability without power steering, and your car has braking capability without ABS. But the grid fins increase the maneuverability a great deal at low cost, which is why they are used. They make it far more likely that the rocket can successfully hit a landing spot during a re-entry. So even though they add some weight and add some cost and add some complexity to the system they still increase the chances of recovering the multi-million dollar rocket hardware, which is a big win.

And the hydraulic fluid running out affects the impact velocity because the terminal trajectory of the rocket was controlled based on the assumption of having the grid fins working. When they stopped working they put the vehicle in a situation that was no longer controllable given the remaining capabilities of the rocket. If the power steering goes out on your car in the middle of a turn that's much worse than if you didn't have power steering at all, and could result in a crash.

> They did grasshopper landing without them right?

As someone who doesn't know the slightest bit about space technology, I was a bit confused about the fact that they successfully landed another rocket. If that's the case why is the landing of Flacon 9 so significant? Is it like a bigger rocket or something?

"full RUD (rapid unscheduled disassembly)" Love the term.

Edit: apparently comes from KSP.

Probably each of those in some order. The first few recoveries will just be for taking apart and analysing, but at some point they'll be launching them; I believe they're already asking around for a customer willing to launch something (at a heavy discount) on a second-hand rocket, but I wouldn't be surprised if the very first reuse launch was self-funded.

I'm going to disagree with most of the other replies to this.

I don't think they will keep/dismantle the first recovered stage. I'm sure they'll examine it minutely, but the whole point of this is to re-use rockets. My guess is that as long as the stage appears to be in working order they will want to actually do that as soon as possible. It's how Musk rolls.

They will likely get a call from the Smithsonian at some point. Tear it down, maybe test some parts, put it back together, and ship it to D.C. You'll be able to look at it and watch video of the launch and landing right there.

Building up a fuel depot in orbit would be a good use of used rockets at first. That way if something goes wrong all you lose is fuel.

Take it apart and examine it I would imagine.

Bad news for me. I usually write like this:

The tank filled with hydraulic fluid, powering the fins and enabling them to rotate and steer, ran out of fluid before landing.

Hopefully the above reads more clearly. It is how I parsed it on first read.

"The horse raced past the barn fell."

It's a http://en.wikipedia.org/wiki/Garden_path_sentence

I'd argue that's because it's wrong; not massively wrong, but wrong. You can have a parenthesis with commata on both sides (as siblings have suggested), or you can (just) write the same sentence with no commata at all and it would make sense, but a single comma in that position is a mistake.

Looks like a French sentence: The ideas are in an order I'm used to.

It's a badly written sentence, in part because it's written in passive voice. Lost_BiomedE's siblig comment rewrites it far more nicely.

BI isn't exactly the bastion of quality journalism.