Edit: isn't whole stage black thanks to residues from engine burn?
Quote from: Maciej Olesinski on 08/14/2014 09:37 pmEdit: isn't whole stage black thanks to residues from engine burn?Difficult to tell from the contrast in the video. Everything looks dark compared to the sky background.
Couple of questions, can anyone tell if the legs deploy? Is the stage not plumb to the water or is that a misperception?Matthew
So is that what the grid fins are for, to help keep the stage straight as it falls?
Quote from: SVBarnard on 08/14/2014 10:06 pmSo is that what the grid fins are for, to help keep the stage straight as it falls?Actually no. Engine gimballing takes care of that during landing. The grid fins will be able to control the stage in the long flight phase when the engines are not running. They can do precision steering by forcing the stage body to a desired angle against the airflow, creating a steering force.
Regardless, they must be getting damn close if CRS-4 is going to go for a barge landing.
Quote from: guckyfan on 08/14/2014 10:11 pmQuote from: SVBarnard on 08/14/2014 10:06 pmSo is that what the grid fins are for, to help keep the stage straight as it falls?Actually no. Engine gimballing takes care of that during landing. The grid fins will be able to control the stage in the long flight phase when the engines are not running. They can do precision steering by forcing the stage body to a desired angle against the airflow, creating a steering force.OK so at first when the the engine is not lit the grid fins will allow the stage to effectively glide? And as for this gimbaling, are you saying the engine bell is able to literally move? I thought it was completely rigid?like this pic shows?
Looks like the camera ship is one of these:http://www.diamond-sensing.com/index.php?id=da42mppguardian
enhanced video:
enhanced video:[youtube]lQCWQuM6p-w[/youtube]
The way the pixels themselves expand during the rapid zoom at the end of the video leads me to believe this is a digital, not mechanical zoom that is applied to the video. It is quite possible this is an editing effect and a non overzoomed video of this landing exists. It is of course, completely up to SpaceX if they wish to release such video, much like they have not been willing to show the post landing "kabooms" of CASSIOPE and ORBCOMM.
It's a lesson to all of us not to get greedy with zoom. A moderate resolution image with the rocket in it is better than a high res image with the rocket half or fully out, particularly when it's zoomed beyond the resolution of the lens or the seeing like this.
Quote from: Comga on 08/15/2014 02:14 amIt's a lesson to all of us not to get greedy with zoom. A moderate resolution image with the rocket in it is better than a high res image with the rocket half or fully out, particularly when it's zoomed beyond the resolution of the lens or the seeing like this. A pet peeve of mine too...As for digital zoom, if it was, then did they intentionally pan out the rocket?
While it doesn't look like digital zoom to me (the grain does't move outward), if it was, it could easily be the motion stabilization (in post) trying to keep the rocket in frame.When you do motion stabilization in post, you have two options. Either you show the black borders of the original film shaking around, or you zoom in the image such that all movement of the borders is outside your new crop.If you have a video with a varying amount of shake, you would change the zoom level/position gradually during the shot to keep everything in frame without cropping more than necessary.The text in the video does say that they did motion stabilization on the video, but the youtube description also says that the operator was trying to zoom in to capture the "landing" in more detail and lost the shot:"Towards the end of the video, the camera operator attempted to zoom in and unfortunately lost sight of the stage and was unable to capture the tip over into the water."
Quote from: Helodriver on 08/15/2014 02:37 amThe way the pixels themselves expand during the rapid zoom at the end of the video leads me to believe this is a digital, not mechanical zoom that is applied to the video. It is quite possible this is an editing effect and a non overzoomed video of this landing exists. It is of course, completely up to SpaceX if they wish to release such video, much like they have not been willing to show the post landing "kabooms" of CASSIOPE and ORBCOMM.If it was digital zoom new details shouldn't emerge and image should degrade. But we only see it get better when it after zoom regains focus.
The way the pixels themselves expand during the rapid zoom at the end of the video leads me to believe this is a digital, not mechanical zoom that is applied to the video.
It is quite possible this is an editing effect and a non overzoomed video of this landing exists.
For those wondering if the legs had deployed, it kind of looks like to me that the had deployed, but the triangular white sections on the hull of the rocket is where the soot from the reentry burn covered the hull. when the legs deployed before touchdown, it left white triangles on the sides where the main hull was covered. At least that's what it looks like to me.
Optical zoom is almost always preferable to digital zoom in regards to image quality. Unfortunately it makes it much harder to keep the object framed correctly.
Somewhat different item: We notice that the rocket had a pretty much constant angle of attack to its descent in that video. That begs the questions: (1) Was this angle of attack deliberate, as a way to more precisely hit a specific target landing point?(2) If it was deliberate, then how was it maintained? The RCS doesn't have unlimited fuel. Mind you, the entire lower atmosphere descent took less than two minutes, so I suppose it is possible.(3) If it wasn't deliberate, then how did it happen? Something assymetrical about the airflow around the nozzles?(4) If it was deliberate, and was used for targeting, then why did the angle remain constant until just before the final touchdown? Was the rocket still off target for landing, and the system trying hard still to make it to target?Or was it simply crabbing into a crosswind?
Why are the legs being discussed? We do have the onboard video showing them deploying.
Quote from: JasonAW3 on 08/15/2014 02:00 pmFor those wondering if the legs had deployed, it kind of looks like to me that the had deployed, but the triangular white sections on the hull of the rocket is where the soot from the reentry burn covered the hull. when the legs deployed before touchdown, it left white triangles on the sides where the main hull was covered. At least that's what it looks like to me.Why are the legs being discussed? We do have the onboard video showing them deploying.
Quote from: guckyfan on 08/15/2014 02:35 pmQuote from: JasonAW3 on 08/15/2014 02:00 pmFor those wondering if the legs had deployed, it kind of looks like to me that the had deployed, but the triangular white sections on the hull of the rocket is where the soot from the reentry burn covered the hull. when the legs deployed before touchdown, it left white triangles on the sides where the main hull was covered. At least that's what it looks like to me.Why are the legs being discussed? We do have the onboard video showing them deploying.Someone meantioned taht the white triangle on the side of the craft made it look like the legs hadn't deployed.
Someone meantioned taht the white triangle on the side of the craft made it look like the legs hadn't deployed.
Quote from: JasonAW3 on 08/15/2014 06:53 pmSomeone meantioned taht the white triangle on the side of the craft made it look like the legs hadn't deployed.?? It is evidence of exact opposite. Legs deployed, uncovering parts of stage that didnt get dirted because legs covered this surface, protecting it during launch and reentry.
Slowing down the long shots to 1/4 of their speed makes the stage look very slow. I wonder if there's any possibility that "4x" was referring to zoom instead of speed. Then again, it was a long way awayI didn't slow down the final landing shots.Also, the 1st long shot finishes almost at the horizontal, and the 2nd long shot starts looking upwards - so either there's a shot from a boat, or they've swapped the orders.Also the mist from the long distance landing shots doesn't align with the exhaust from the side mounted cameras.So just a draft with that 1/4 speed and order change, side by side with the side mounted camera footage. I haven't cut down anything they supplied, but I'd probably agree with the creative decision to not have it too long
Quote from: guckyfan on 08/15/2014 02:35 pmWhy are the legs being discussed? We do have the onboard video showing them deploying.We have onboard video that shows 2 of the 4 legs deploying. I don't, myself, have any reason to expect the other two legs had any special problem deploying - but it's not actually demonstrated that they did deploy from the video you reference.
I think you slowed down already slowed down footage. So it went from 1/4 speed to 1/16 speed.
and then the sharks eat the stage..
without two of the legs.. or with both.. we don't know how many legs deployed
Quote from: Avron on 08/16/2014 12:20 amand then the sharks eat the stage..I don't think fate of stage was related to leg deployment, but to fact that stage "landed" in water.Quote from: Avron on 08/16/2014 12:20 amwithout two of the legs.. or with both.. we don't know how many legs deployedI will assume that all legs deployed untill proven otherwise. Do you have any evidence for this kind of failure?
here ya go:
Quote from: Elmar Moelzer on 08/15/2014 04:17 pmOptical zoom is almost always preferable to digital zoom in regards to image quality. Unfortunately it makes it much harder to keep the object framed correctly.For sure - I always viewed digital zoom as something consumer-level cameras do because people are too lazy....Unless there's a way for the camera sensor to get a higher resolution (or frame rate) by using only a portion of its area, it seems like a counter-productive practice. And if it was done, then a panned-out object can be "un-cropped" by going back to the full recording.Getting data on the sensor chip and then discarding it is just a recipe for regret.
I only later realized how much I was asking for... this is probably a result of frame-by-frame manual panning, right?
Quote from: meekGee on 08/17/2014 07:38 pmI only later realized how much I was asking for... this is probably a result of frame-by-frame manual panning, right?frame-by-frame but in a highly automated way, edit time was just about 10minutes
Quote from: meekGee on 08/15/2014 04:22 pmQuote from: Elmar Moelzer on 08/15/2014 04:17 pmOptical zoom is almost always preferable to digital zoom in regards to image quality. Unfortunately it makes it much harder to keep the object framed correctly.For sure - I always viewed digital zoom as something consumer-level cameras do because people are too lazy....Unless there's a way for the camera sensor to get a higher resolution (or frame rate) by using only a portion of its area, it seems like a counter-productive practice. And if it was done, then a panned-out object can be "un-cropped" by going back to the full recording.Getting data on the sensor chip and then discarding it is just a recipe for regret.There's a big difference between digital zoom for a still and digital zoom for video. Very few cameras these days record every bit that comes out of the sensor when recording video, so you usually do get some advantage from doing a digital zoom in that more of what you lose is from outside the frame and you get to keep more of what you zoomed in on.
...I kept hoping I'd see the legs, but I don't think I can....
Quote from: meekGee on 08/17/2014 07:38 pm...I kept hoping I'd see the legs, but I don't think I can....Maybe it depends on my display but around 0:07 I could see for a very short time something like the piston on the right side of the rocket...
Quote from: MTom on 08/18/2014 10:55 pmQuote from: meekGee on 08/17/2014 07:38 pm...I kept hoping I'd see the legs, but I don't think I can....Maybe it depends on my display but around 0:07 I could see for a very short time something like the piston on the right side of the rocket...At the his point if I stare at a blank wall for more than a minute, I can see legs deploying.My wife commented on that during dinner, as my gaze was fixated on the wall opposite, instead of on the TV...
Image stack of some of the frames from the YouTube video, with some extra alignment.
I'd been thinking about the attitude this stage was maintaining during freefall and if that angle was something being actively maintained by the RCS or was just how something weighted and shaped like that naturally falls through the atmosphere.I'm beginning to suspect the latter, from an artifact of a different rocket, the first stage of the UKs Black Arrow R3 rocket launched in Woomera.This stage survived reentry unpowered and freefell onto a cattle station in the outback after delivering the Prospero satellite to orbit, landing largely intact. The stage was liquid fueled with multiple engine bells much like the Falcon 9 v1.1. Upon impact the engine bells and one side of the stage's base show definite directional crushing, correlating with an impact slightly off the vertical, evidence of a Falcon like angled attitude assumed naturally without RCS guidance.
(snip)... while an "engine-first/down" entry would require much less RCS during the flight but subject the engines to full reentry heating and aerodynamic pressures. ...(snip)
Quote from: RanulfC on 09/23/2014 04:44 pm(snip)... while an "engine-first/down" entry would require much less RCS during the flight but subject the engines to full reentry heating and aerodynamic pressures. ...(snip)Well, if I were hand waving and speculating wildly about reusable orbital stages (or much higher energy stages than the first stage of a Falcon 9), I would think that an engine designed for re-entry would use some of the residual fuel (not oxidizer except maybe enough to run a pump at very low power) to cool the engine during re-entry forming a protective layer as it vaporizes and heats up. In fact I can't help but think that there was nothing inherently wrong with a variety of schemes based on that like the George Detko ATV. Some much larger scale versions of that were imagined, including ones that were not purely SSTO but disposed of fuel tanks that were side attached despite the vehicle being cone shaped (this got around the terrific volume penalty of using Hydrolox).
Quote from: nadreck on 09/23/2014 05:10 pm(snip)... hand waving and speculating wildly ... (snip) ... I would think that an engine designed for re-entry ... Quote from: RanulfC on 09/23/2014 05:47 pmROMBUS, et-al? Very et al - lots of derivatives of those ideas out there - including one I had high hopes for in the 90's - the DC-X. Quote from: RanulfC on 09/23/2014 05:47 pm(snip)... I've pointed to the report before but the wider the base the better the reentry heating and shockwaves are kept away from the upper half of the vehicle. ... (snip)Since the engine bells don't present a "unitary" surface towards the atmosphere (as a plug nozzle or plug cluster does in the above designs) they wouldn't tend to present the necessary surface to allow a stable shockwave pattern to emerge during reentry. In fact the edges of the engine bells, the thinest and hardest to cool sections of the bell would be exposed to the most heating unless the engines were actually running at a very low throttle to use the exhaust(s) as a virtual heat shield. (Before you go to far down this road recall two things; 1) The M1D/V only "throttles" to 70% so that would be the thrust level of the center engine to create the "spike" and 2) that's going to be using propellant AND decellerating the vehicle at the same time)IIRC Gary Hudson mostly used water as a heat sink in his designs, though Bono (ROMBUS et-al) and others tended to use the cryo-hydrogen, flowed through the base heat shield and then "dumped" overboard through the nozzles for reentry protection. I don't think RP1 would work as well but since F9 carries no water... (snip)I'm of the belief (and in the minority here) that eventually SpaceX is going to have to go with squater, fatter more capable stages that can reentry "engines-first" to facilitate recovery and landing operations if they every really want to reduce the operational "turn" time for reuse RandyYes, I totally agree. Lets imagine a BFR with a squat reusable first stage that puts one of the squat cones from the ATV derivative craft to an altitude where its plug nozzle based aerospike can work. I think it is a given that the current Dragon TPS is perfectly adequate without cooling for the broad area of the base that we really only have to worry about expending enough fuel through the plug nozzles to keep them safe. By eliminating 300 seconds of ISP and starting in a virtual vacuum the ROMBUS et al designs suddenly are perfectly doable with today's technology(with only a bare minimum of arm waiving).
(snip)... hand waving and speculating wildly ... (snip) ... I would think that an engine designed for re-entry ...
ROMBUS, et-al?
(snip)... I've pointed to the report before but the wider the base the better the reentry heating and shockwaves are kept away from the upper half of the vehicle. ... (snip)Since the engine bells don't present a "unitary" surface towards the atmosphere (as a plug nozzle or plug cluster does in the above designs) they wouldn't tend to present the necessary surface to allow a stable shockwave pattern to emerge during reentry. In fact the edges of the engine bells, the thinest and hardest to cool sections of the bell would be exposed to the most heating unless the engines were actually running at a very low throttle to use the exhaust(s) as a virtual heat shield. (Before you go to far down this road recall two things; 1) The M1D/V only "throttles" to 70% so that would be the thrust level of the center engine to create the "spike" and 2) that's going to be using propellant AND decellerating the vehicle at the same time)IIRC Gary Hudson mostly used water as a heat sink in his designs, though Bono (ROMBUS et-al) and others tended to use the cryo-hydrogen, flowed through the base heat shield and then "dumped" overboard through the nozzles for reentry protection. I don't think RP1 would work as well but since F9 carries no water... (snip)I'm of the belief (and in the minority here) that eventually SpaceX is going to have to go with squater, fatter more capable stages that can reentry "engines-first" to facilitate recovery and landing operations if they every really want to reduce the operational "turn" time for reuse Randy
Quote from: Helodriver on 09/11/2014 06:50 pmI'd been thinking about the attitude this stage was maintaining during freefall and if that angle was something being actively maintained by the RCS or was just how something weighted and shaped like that naturally falls through the atmosphere.I'm beginning to suspect the latter, from an artifact of a different rocket, the first stage of the UKs Black Arrow R3 rocket launched in Woomera.This stage survived reentry unpowered and freefell onto a cattle station in the outback after delivering the Prospero satellite to orbit, landing largely intact. The stage was liquid fueled with multiple engine bells much like the Falcon 9 v1.1. Upon impact the engine bells and one side of the stage's base show definite directional crushing, correlating with an impact slightly off the vertical, evidence of a Falcon like angled attitude assumed naturally without RCS guidance.With the propellant depleated (Black Arrow) or almost depleated (F9) the engines are the most mass and the vehicle "wants" to point with the most mass forward. The main "question" was how does in reenter since an "engines up/TPS covered stage interface down" angle would require active RCS through the point where the vehicle was rotated to an "engines-down" position for final retro-fire, while an "engine-first/down" entry would require much less RCS during the flight but subject the engines to full reentry heating and aerodynamic pressures.What might have been A little more propellant and the Black Arrow might have been the first reusable rocket stage in history, it was robust enough for the job Randy
Albeit at the cost of more RCS control requirements and active reentry positioning because of the unstable entry angle over the more stable engine first position.
Quote from: RanulfC on 09/23/2014 05:47 pmAlbeit at the cost of more RCS control requirements and active reentry positioning because of the unstable entry angle over the more stable engine first position.A rocket is just as stable backwards as forwards is it not? Pendulum fallacy and all that.
Ok folks, resist the temptation to post unless you are bang on topic here.From this point onwards.
Quote from: Chris Bergin on 09/24/2014 02:56 pmOk folks, resist the temptation to post unless you are bang on topic here.From this point onwards.Can we get a thread made for nose-first vs tail-first entry modes and have the off-topic material moved there? I think there's some good discussion here, it just doesn't belong here.