Author Topic: LIVE: SpaceX - Falcon I (Mk.II) NET March 20 (Attempt 2) (Read 265130 times)

sandrot · « **Reply #920 on:** 04/11/2007 08:35 pm »

Quote

Avron - 11/4/2007 12:19 AM

I think if you try and correct a Yaw/pitch cyclic motion, you may end up with roll, without the engine providing any roll torque to the vehicle.. "gyroscopic precession " and all that..

You can try this with a small plastic bottle, half full of water. You hold it from the neck and you shake it cyclically with a yaw/pitch motion. After a while you get a whirl spinning inside the bottle. Now put the bottle in a bath tub full of water, it will float. And the inside whirl, while winding down, will make your bottle roll.

Comga · « **Reply #921 on:** 04/12/2007 02:50 am »

Agreed. And that will happen in a bottle without any anti-slosh baffles. The rotation is transferred by the friction of the liquid sliding along the surface of the bottle. The coupling will be much stronger with even a small baffle within the volume.

JIS · « **Reply #922 on:** 04/12/2007 03:32 pm »

If only this is a problem it can be easily fixed by software update.

Analyst · « **Reply #923 on:** 04/12/2007 03:47 pm »

Whenever I read the word "easily" in connection with spaceflight I have strong doubts. You can change software easily (compared to hardware), if you fix it is completely another matter.

Analyst

axel321 · « **Reply #924 on:** 04/14/2007 10:27 am »

Quote

The stage did not only roll in the youtube clip, but it pitched/yawed so that the nozzle was pointing in the completely wrong direction, say, 90 degrees to the flight path. Everyone can see this for themself.

Sorry, no. Not true. The rotation may make you dizzy. The pitch/yaw looks stronger when camera rotates around the engine. Think 3D. Try to focus on the spot on Earth the engine is supposed to be directed at. Then you'll see it's not that bad.

Jim · « **Reply #925 on:** 04/14/2007 02:10 pm »

Quote

axel321 - 14/4/2007 6:27 AM

Quote
The stage did not only roll in the youtube clip, but it pitched/yawed so that the nozzle was pointing in the completely wrong direction, say, 90 degrees to the flight path. Everyone can see this for themself.

Sorry, no. Not true. The rotation may make you dizzy. The pitch/yaw looks stronger when camera rotates around the engine. Think 3D. Try to focus on the spot on Earth the engine is supposed to be directed at. Then you'll see it's not that bad.

Huh? It is bad

sandrot · « **Reply #926 on:** 04/14/2007 06:12 pm »

Quote

Analyst - 12/4/2007 11:47 AM

Whenever I read the word "easily" in connection with spaceflight I have strong doubts. You can change software easily (compared to hardware), if you fix it is completely another matter.

Analyst

You may be right to have strong doubts, nevertheless the fix might be easy.

I have a background in robotics, and in a robot controller you implement a bunch of control loops to keep your speed and position based on sensors inputs. At the end these control loops are another bunch of matrix operations executed in real time. Several times you "fix" a problem with the robot (most of the times some "Parkinson" effect or an overshoot reaching a position) just changing an element in the matrixes.

It can get very tough if you discover that it is not just an element in the matrix that has to be changed, but the whole algorithm.

Switching to rocket science, for a rocket as for a robot, you need to reach a point in space along a trajectory and you minimize errors in reaching the point and moving along a predefined trajectory.

From what SpaceX has indicated so far we are not in the worst case scenario for the fix (so no algorithm change).

stockman · « **Reply #927 on:** 04/14/2007 06:56 pm »

well one way to see how bad or not so bad it actually is - Lets see the whole video already! Surely that can't be too much to ask and it sure doesn't need to wait for the terabyte of data to be analyed to simply put out the video. Lets see it already!

sandrot · « **Reply #928 on:** 04/14/2007 07:24 pm »

Quote

stockman - 14/4/2007 2:56 PM

well one way to see how bad or not so bad it actually is - Lets see the whole video already! Surely that can't be too much to ask and it sure doesn't need to wait for the terabyte of data to be analyed to simply put out the video. Lets see it already!

They don't want you to see the UFO that grabbed with its robotic arm the upper stage shaking it wildly...

:laugh:

AntiKev · « **Reply #929 on:** 04/15/2007 08:52 am »

SpaceX is not NASA. They're not bound by the FOIA to disclose any of this information. Although I'm not 100% sure that NASA is either. Elon is a private investor with a privately held company doing private business. They will disclose what they want and keep what they want for whatever internal reasons. Demanding to see the video because we're curious space nuts, or engineers wanting to help solve the problem will not help. There may be proprietary information that Musk et. al. don't WANT you to see. So what? It happens, that's business. We can't expect them to disclose every little bit of information about their launch vehicle. Let the engineers who are familiar with the systems and their functions fix the problem.

This isn't meant to criticize the people offering suggestions, educated guesses or problem solving. It's meant as a commentary to those who, out of pure morbid curiosity, want to see the whole video.

meiza · « **Reply #930 on:** 04/15/2007 11:59 am »

Quote

sandrot - 14/4/2007 7:12 PM

Quote
Analyst - 12/4/2007 11:47 AM

Whenever I read the word "easily" in connection with spaceflight I have strong doubts. You can change software easily (compared to hardware), if you fix it is completely another matter.

Analyst

You may be right to have strong doubts, nevertheless the fix might be easy.

I have a background in robotics, and in a robot controller you implement a bunch of control loops to keep your speed and position based on sensors inputs. At the end these control loops are another bunch of matrix operations executed in real time. Several times you "fix" a problem with the robot (most of the times some "Parkinson" effect or an overshoot reaching a position) just changing an element in the matrixes.

It can get very tough if you discover that it is not just an element in the matrix that has to be changed, but the whole algorithm.

Switching to rocket science, for a rocket as for a robot, you need to reach a point in space along a trajectory and you minimize errors in reaching the point and moving along a predefined trajectory.

From what SpaceX has indicated so far we are not in the worst case scenario for the fix (so no algorithm change).

But you can't test it cheaply, like you could with a robot... You have to simulate and verify and check and double-check, and that costs money and still is somewhat uncertain.
It's still cheaper and faster of course if you're flying a Falcon I in the single millions and not Saturn V.

Antares · « **Reply #931 on:** 04/16/2007 03:15 pm »

Just some comparison numbers for this launch I first found interesting when considering SpaceShip One:

Orbital energy is defined numerically as speed squared divided by 2, minus gravitational parameter mu divided by radius. Thus,

Sitting in your chair: -62.5 km^2/s^2
SpaceShip One at apogee: -61.5
Falcon I Mk.2 at apogee: -46.8
ISS in orbit: -28.5 (rounding to 17500mph at 6725km)
Escape: 0

Avron · « **Reply #932 on:** 04/17/2007 03:56 am »

Quote

AntiKev - 15/4/2007 4:52 AM

This isn't meant to criticize the people offering suggestions, educated guesses or problem solving. It's meant as a commentary to those who, out of pure morbid curiosity, want to see the whole video.

Totally agree i.r.t the private company part.. but I would still like to see the whole video

Comga · « **Reply #933 on:** 04/23/2007 02:53 am »

Quote

kevin-rf - 10/4/2007 8:24 PM
The second stage did a full roll in the extra 10 seconds on the YouTube video. SpaceX was able to and obvious did pick images that where all at the same point in the roll. Cherry picking the images mitigates the raised eyebrows from looking at rotated images. That is called media spin.

I was going to say that "cherry picking" was an unfair accusation until I saw the attached ad on the inside of the back cover of the April 16 edition of Aviation Week and Space Technology. (I assume ads can be copied and posted freely.) These "cherry picked" images would leave one with the impression that nothing at all went awry.

This is disingenuous at the very least, perhaps "media spin" as you said, dishonest at worst.

The question is why would they buy this ad? It has got to cost a good chunk of change. Anyone who cares knows what happened. Their only real customer, NASA COTS, is not going to be impressed by an ad. They can hardly fit in more flights. Who is the intended audience for this advertisement?

kevin-rf · « **Reply #934 on:** 04/23/2007 12:20 pm »

Quote

Comga - 22/4/2007 9:53 PM

The question is why would they buy this ad? It has got to cost a good chunk of change. Anyone who cares knows what happened. Their only real customer, NASA COTS, is not going to be impressed by an ad. They can hardly fit in more flights. Who is the intended audience for this advertisement?

Welcome to the logic that fueled the DOT com boom in the late 90's. You are right, If I was a potential customer I would already be aware of the falcon and that add would really raise my eyebrows.

stockman · « **Reply #935 on:** 04/23/2007 12:33 pm »

Is it my imagination or did they also do a little brush up work on the one image with the earth in the background? I seem to recall from the stills on their web site that there was a noticable wobble in the still frame of the background Earth and in this add that seems to have been cleaned up a tad.

I am a big (hopeful) believer in this industry but I have to admit this touched up add, coupled with the fact that we are now past the latest two week wait period that Elon promised some public results certainly is putting a strain on my unquestioning belief in what he is trying to accomplish here with SpaceX.

I hope he comes out this week with some results for us to digest along with the FULL and unEDITED video so we can put all this speculation to rest once and for all.

stockman · « **Reply #936 on:** 04/23/2007 12:57 pm »

I hope this post correctly. This is the image I am referring to. This is from the SpaceX web site and you can clearly see the wobble in the earth background. I notice this is NOT in the add they presented.

http://www.spacex.com/00Graphics/Images/DemoFlight2/T=7m17s.JPG

savuporo · « **Reply #937 on:** 04/23/2007 03:04 pm »

the image filters used is called deinterlace and sharpen. why are you guys complaining about properly formatted ad ? i mean, when Microsoft releases next version of windows, how often do they speak about reduced security holes, malware, crashes and code bloat ? They actually do speak about them, but not in the full-page ads ..

clongton · « **Reply #938 on:** 04/23/2007 03:23 pm »

It looks to me like the image has been cleaned up. That’s NOT the same thing as what it appears is being suggested here. The image itself has not be materially altered. Think about the focal points involved. The onboard camera was obviously focused on the nozzle. And the horizon is how far away? There is no way for a commercially available camera of the kind probably used to maintain a sharp focus on both the nozzle and the horizon which is a few thousand miles away. To me it looks like a completely NORMAL “Edit-To-Clean” job. Perfectly legal, perfectly legitimate, and completely ethical. It is industry standard practice.

kevin-rf · « **Reply #939 on:** 04/23/2007 04:06 pm »

Since an interlaced image is really two images in one it is very easy to clean. Just throw away every other line. Even lines are one image, odd lines are the second image. Technically that is not dis-honest. They are just picking one of the two images in each cherry picked video frame.

The reason you do interlaced imaging is you can get twice the resolution for the same data rate. This is assuming your imaging is not shifting fast enough to cause you issues. Some would argue a interlaced video camera is dishonest...and we should burn all our TV's