Author Topic: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread (Read 480678 times)

hrissan · « **Reply #560 on:** 04/15/2015 08:46 pm »

Quote from: Chris Bergin on 04/15/2015 08:38 pm

Quote from: cartman on 04/15/2015 08:34 pm
Video went private. Too bad some of us download them as soon as we can

It will have been reuploaded by 1001 accounts already. Best someone links one of those and not eat up bandwidth here if that goes into the thousands of downloads.

Ok, I risk mine...

A12 · « **Reply #561 on:** 04/15/2015 08:53 pm »

https://app.box.com/s/2nbw5p6047ocur6ma79e4zf1xni19bfw

junk.munk82 · « **Reply #562 on:** 04/15/2015 08:55 pm »

foltster · « **Reply #563 on:** 04/15/2015 08:59 pm »

Wow. I can't stop watching this. Can't wait to see them actually pull it off. Really gives the perspective of how small the target is.

RoboGoofers · « **Reply #564 on:** 04/15/2015 09:07 pm »

The legs seem to pause at half extended.

rcoppola · « **Reply #565 on:** 04/15/2015 09:08 pm »

I love how the entire Octoweb, or at least a subsection of engines get blown off like a cork.

fthomassy · « **Reply #566 on:** 04/15/2015 09:09 pm »

Quote from: RoboGoofers on 04/15/2015 09:07 pm

The legs seem to pause at half extended.

Has from the first.

JasonAW3 · « **Reply #567 on:** 04/15/2015 09:11 pm »

So freaking CLOSE! GOT to slow down a bit more those last 150 feet or so. Would have still come in too hard it looks, even if it was dead on target. Half that velocity, and I think it would have nailed the landing.

Sohl · « **Reply #568 on:** 04/15/2015 09:17 pm »

Quote from: JasonAW3 on 04/15/2015 09:11 pm

So freaking CLOSE! GOT to slow down a bit more those last 150 feet or so. Would have still come in too hard it looks, even if it was dead on target. Half that velocity, and I think it would have nailed the landing.

It was going pretty slow vertically right there at the end. Unfortunately, it has a pretty big pitch rate that made it swing too far from vertical to stick the landing.

Need smaller pitch oscillations!

Sohl · « **Reply #569 on:** 04/15/2015 09:21 pm »

Looking at the bright side, at least the newest high-res video has lots of kaboomy goodness!

DatUser14 · « **Reply #570 on:** 04/15/2015 09:21 pm »

The file that cartman uploaded now redirects to "you are not allowed to access this section".

mme · « **Reply #571 on:** 04/15/2015 09:26 pm »

Quote from: JasonAW3 on 04/15/2015 09:11 pm

So freaking CLOSE! GOT to slow down a bit more those last 150 feet or so. Would have still come in too hard it looks, even if it was dead on target. Half that velocity, and I think it would have nailed the landing.

It may have been coming in a bit hot, but I think the main issue is the rotational momentum do to the over correction. It strained the left leg to the breaking point.

Inch-by-inch, they'll get there.

SoulWager · « **Reply #572 on:** 04/15/2015 09:30 pm »

Looks like the octoweb got pushed overboard by the explosion.

Tonioroffo · « **Reply #573 on:** 04/15/2015 09:35 pm »

The video is now public on YouTube. Hope nobody loses their jobs over this?

mme · « **Reply #574 on:** 04/15/2015 09:44 pm »

Quote from: Sohl on 04/15/2015 09:17 pm

Quote from: JasonAW3 on 04/15/2015 09:11 pm
So freaking CLOSE! GOT to slow down a bit more those last 150 feet or so. Would have still come in too hard it looks, even if it was dead on target. Half that velocity, and I think it would have nailed the landing.

It was going pretty slow vertically right there at the end. Unfortunately, it has a pretty big pitch rate that made it swing too far from vertical to stick the landing. Need smaller pitch oscillations!

I agree, but I think it's good news. Totally fixable from multiple angles (reducing lag in the system where possible, modeling the lag better where it can't be reduced, adding constraints to the size of inputs as the target is approached.)

TomH · « **Reply #575 on:** 04/15/2015 09:45 pm »

Quote from: JasonAW3 on 04/15/2015 09:11 pm

So freaking CLOSE! GOT to slow down a bit more those last 150 feet or so. Would have still come in too hard it looks, even if it was dead on target. Half that velocity, and I think it would have nailed the landing.

But that just is not possible. Even at lowest throttle on that single Merlin, the thrust is too high. If you come in slower than that, the thing will stop mid-air above the deck and then begin ascending again. The Merlin cannot throttle deeply enough to hover and land softly. They have to come screaming in at high velocity while decelerating very quickly. V = 0.00m/s and Altitude above deck = 0.000m have to occur at the exact same moment in time. The Merlin has too much thrust to hover/land gently. Grasshopper is ballasted. This is a whole other ball game. Coming in like a bat out of Hades to a perfectly timed stop is the only way to do it without modifying the Merlin to throttle far more deeply or to have a smaller landing engine in the center.

Oli · « **Reply #576 on:** 04/15/2015 09:49 pm »

Well that's a cool video.

It actually looked good until 5s into the video where something seemed to have pushed it out of balance.

aero · « **Reply #577 on:** 04/15/2015 09:53 pm »

From the one video I saw, looked to me like the stage was over the barge but still controlling for the center of the "X-marks-the-spot" when it could have set down vertically and safely(?) but a little off center. Maybe the control needs a little more logic to know when it is "good-enough." Or maybe it's just pretty hard to get it even that close.

Of course, returning to a set down on land would perhaps allow a bit larger target area.

JamesH · « **Reply #578 on:** 04/15/2015 09:55 pm »

Quote from: Oli on 04/15/2015 09:49 pm

Well that's a cool video.

It actually looked good until 5s into the video where something seemed to have pushed it out of balance.

It did seem to go off balance very quickly given trajectory looked OK, and it took somewhat longer than you might expect for the engine to gimbal and counteract the movement. I wonder if that is the stiction issue at play after a sudden aerodynamic change - either wind sheer or the effect of the legs deploying.

Rocket Science · « **Reply #579 on:** 04/15/2015 09:56 pm »

I wonder if some Soyuz style braking rockets at the top of stage might prove useful... Hmmmm...