Nitpick: The first attempt ran out of hydraulic fluid (for the guidance fins), not out of propellant for the RCS thrusters.

The rest of what you say is generally true, although a larger target *would* help. The advantage of a larger target is that, while you still have to zero your horizontal velocity, you don't have to zero it anywhere terribly precise. You can pick an optimal set of thrusts that results in the correct orientation and velocities (horizontal and vertical) without worrying overmuch *where* that series of thrusts has you touching down. Both attempts so far clearly demonstrate the ability to do an excellent good job of targeting a (relatively) tiny barge, but currently, if the rocket would come down even 100' (30m) to one side of its target spot, it needs to induce a horizontal momentum (which requires leaving a vertical attitude as well, it can't just translate sideways) and then null that momentum at the right moment (and fix its attitude). That's hard.

To clarify for the person who keeps misunderstanding my posts: they should, of course, plan for the barge-level of landing precision. They should aim for a precision of inches, and within a year, they may get it... 90% of the time. Stuff goes wrong, though, and (especially early in the testing of such a system) it behooves them to use a larger landing area so that there's some margin for error. I'd say their land attempt (possibly next CRS launch, in a couple months) has a very good chance of being their first success.

The thrusters aren't even supposed to be needed there, actually. They're only supposed to fire in very short bursts, not a continuous stream like in the video. As for the legs holding up, just one of them supported the whole rocket for a few seconds; all four should have had no trouble. We know a hell of a lot more than just that it crashed. To claim otherwise is to embrace ignorance.

There is literally no point at all to living in a world where you are only concerned with the things that you absolutely know. You don't absolutely know *ANYTHING*, you could be a simulation in some advanced being's AI-run world, along with everything the program running you has ever simulated observing. The only way to achieve anything difficult is to analyze the differences between failures and successes, and a part of that analysis is to determine how close you came to success.

But then, you probably already knew that and are just a naysayer...

I'm not trying to fix the wrong problem, I'm trying to add a backup for the fix. Shit happens. Parts will fail, valves will stick, unexpected winds or waves will occur.

I thought the fact that the primary goal was to correct the problem that caused the excessive lateral velocity was so bloody obvious that it didn't need saying, but I guess I forgot I'm on the Internet. The purpose of my idea was not "fuck it, fixing a little problem is hard, let's do something much more complicated", it's "shit happens. What can we do to survive the likely error modes?"

A) You've mastered "dictionary", "bookshelf", and "somewhere", but an eight-letter word is too big for you?

B) Welcome to the Internet. You probably got here using "the blue e", right? Tip: highlight (whoops, big word) the scary word with your mouse, right-click on it, and click the option that will search or define the word for you! No need to go over to your bookshelf at all, and you get to avoid looking like a lazy ignoramus (sorry, is that one too long?) at the same time!

Seriously, I get that you're probably joking, but that is a really stupid thing to complain about. Definitions don't belong in a summary, especially not a summary delivered through the biggest inter-connected information network humanity has ever created.

Agh, bloody autocorrect and stupid failure to proofread. First paragraph:

What would it cost (presumably a matter of weight) to upgrade the nose thrusters?

You saw the part where the reaction control thruster at the top (little white plume) is trying to keep the rocket upright, didn't you? Lasts about four seconds. The rocket had already touched down (on at least one leg, with engines shut off) at that point. If the stage had been even a *little* closer to upright, or the thruster a *bit* more powerful, the rocket would have settled onto all four legs and that would be it.

Also, the stage swings through vertical in the moment before touchdown. It's that half-second of overcorrection that doomed it. It was over the barge and in the correct orientation less than 1000 millisecond before touchdown. I'd say the only reason that "seconds away from what would have been the first successful landing" is wrong is because it was more like *one* second.

So, I asked this in the last thread but the discussion there was already mostly dead: what would it cost (presumably mostly a matter of weird) to upgrade the nose thrusters? These are cold-gas (nitrogen) thrusters, and I can't imagine they have a lot of power.

The Dragon uses hydrazine-based "Draco" thrusters for its RCS system; might it be worth adding a hydrazine thruster with a few seconds of fuel in place of the cold-gas thrusters, enabling the rocket to correct its orientation in the moment of touchdown (when it can no longer use engine gimbaling)? For that matter, how does the thrust of a hydrazine thruster (I think a Draco goes to about 90 lbf) compare to a cold-gas thruster? Wouldn't want to bend the rocket with excessive pressure at the top, after all.

Alternatively, the rocket contains a bunch of compressed gases (helium is used for pressurizing the fuel/oxidizer tanks, I believe). Would it be possible, on landing, to vent some of that pressure to provide additional attitude control? It might reduce the rocket's rigidity a bit, which could be bad, and it's a high-pressure valve (of course), but when your concern is that the rocket land upright (you'd want to use this in the moment before touchdown, to avoid excessive pressure on just one leg as appears to have happened here) it might be worth it. The obviously don't have a *lot* of excess pressure - fluids cost weight, pressurized ones moreso - but they probably have some and it might be suitable for a last-second thruster.

Thoughts?

Hasn't the future of 'open' android always looked bleak, more or less by design? At the bottom of the stack, we have SoC vendors who don't give a damn, handset OEMs who don't give a damn and/or actively prefer that older handsets remain as outdated as possible so you'll buy something new, and carriers who have largely the same incentives as handset vendors; but with their own crapware. This ensures that hardware support is spotty and typically weak for anything except whatever the device shipped with(and it's a moot point on the cryptographically locked devices). Markedly worse than the PC world in terms of vendor helpfullness or ability to do much of anything without a BSP or cobbling blobs together from vendors with slightly longer update support windows.

From the top of the stack, the 'free' parts of android are basically Google's hardware abstraction layer for google play services, and getting steadily more so.

Yep, Also, while it's (obviously) true that they didn't stick the landing vertically, they weren't far off. For that RCS thruster at the top to have held the rocket upright as long as it did, the stage must have been *barely* past its center of gravity. The thruster (and remember, these are simply compressed gas thrusters intended to impart a quick nudge; they aren't very powerful) fired for about 4 seconds continuously, which probably exhausted its propellant, but in that time the stage didn't visibly lean over any further!

A *tiny* bit closer to vertical, and the thruster would have been able to correct. A bit beyond that, and the thruster wouldn't even have been needed; if the center of gravity is inside the footprint of the landing gear then the stage would self-right as long as the legs didn't crumple (and, contrary to what the OP says, they actually had excellent control of vertical speed). Alternatively, a slightly more powerful thruster would have been able to correct the angle (I wonder how much it would cost - mostly in weight, I assume - to switch to hydrazine rockets like the Dragon's "Draco" RCS thrusters).

Compare to the first landing attempt, where the uncontrolled guidance fins meant the rocket was coming in at such a sharp angle that it basically skipped off the barge like a rock on a lake. This one was *much* closer to upright, and while it did fall over, the whole thing (achieved zero vertical velocity resting on its landing gear for a moment. That's damn impressive, and it was a very close thing.

I can't digg up the original contract to check; but some of the stories state that they are going to Apple because the deal was to purchase 'iPad+software', as a packaged product, from Apple. By all accounts Pearson was the significant weak link (not a shock, that's pretty typical for them), while Apple's stuff suffered only from the fairly pitiful state of iOS management; but the school district didn't structure the deal as 'Contract #1, buy ipads, Contract #2, buy textbook apps'; it was a package, and their claim is that half the package was rotten and the other half is of little use to them without the underdelivered component.

Given that Apple is reputed to be a brutal and efficient taskmaster of its suppliers, I'd imagine that either the school district will fail, or Apple will gouge it out of Pearson; but to the best of my understanding there is logic behind complaining to Apple, given the terms under which the devices were purchased.

If you are working on the (probably bullshit) theory that these devices improve educational outcomes, there is a civil rights interest in ensuring that students who made poor prenatal choices still have the opportunity to get a decent education.

However, that assumption is under-supported(even if they were free, it's not news that electronic gizmos are good for slacking off with, so they might have a negative effect unless the school actually has a good plan in mind; and since they aren't free, they are being chosen to the exclusion of other possible educational aids), and if it doesn't happen to be true; then there isn't much of a civil rights case for access to toys. If anything, devices for slacking off probably amplify the effects of differing qualities of home life, since parental attention will have a major effect on how much slacking you can get away with.

Irony: the rocket motor with the highest TWR in the industry (at over 150, the Merlin 1D that SpaceX uses beats any of their competition), which is normally a very good thing, has *too much* TWR, even with only one engine out of nine firing!

The superintendent at the time 'resigned' over the controversy; but depending on the outcome of the FBI's ongoing investigation into the circumstances of the bidding process, he may or may not be looking at further consequences.

Pearson is a company that brings a sort of defense contractor vibe to the educational sector. They are huge, superb at landing contracts, excellent at writing contracts that promise somewhat less than they appear to; but not so hot on delivering, much less on time or on budget.

Anyone buying a zillion ipads for school children without realizing that they'll be using them mostly to screw around on the internet within about five minutes is certainly an idiot; and Pearson certainly can't take the blame for that; but their failure to deliver some curriculum slurry and a terrible textbook app or two within the agreed upon time? That's the sort of thing they do.

It would not much fail to surprise me if it wasn't done this way; but something like those seatback location/direction displays require relatively little data transfer(you wouldn't need more than the 4800 baud NMEA spew you'd get from a standard GPS device, and you could likely get away with less) and no responses from the seatback unit; so you could do everything you'd need over an isolated, intrinsically unidirectional, link.

Put the avionics on the emitter side of an optoisolator, blindly blinking out location and heading data, the controller for the seatback entertainment system on the receiver side, listening, and you get an arrangement where there simply isn't anything to attack at the software level(you could probably hose in flight entertainment for the entire aircraft one way or another; but boredom isn't very lethal); and where physical attacks might be possible; but (by choosing an optoisolator and the location of the interface between the critical and noncritical side) can be made quite difficult.

It *has* RCS at the top of the stage. One of them fires for a good 4-5 seconds trying to hold the stage upright after the touchdown (it failed, obviously). Were you watching in really low quality or something?