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Falcon 9 Rocket question

Falcon 9 Rocket question

Any physicists out there: If the Falcon 9 rocket was spinning like a top as it was landing, would it's angular momentum make it easier to land upright?

Näky | 2015年1月25日

Ron, ultimate goal is to land, recover and reuse. But there is multiple steps and milestones between goal and todays achievements. This landing that ended to RUD, was first test to land on hard surface by real mission stage. It wasn't flying success but a not a total failure either. They did many things right and had some miscalculations (amount of hydraulic fluid).
Landing program is still in testing phase, so equipment failures are to be expected, failing landing might be successful by other testing metrics. Beta test devices are not production units, and by failing device might do its intended function. I dont believe that todays boosters are built to last multiple missions, even if successfully recovered in testing phase, those might thought.

Grinnin'.VA | 2015年1月25日

@ Näky | January 25, 2015

Ron, ultimate goal is to land, recover and reuse. ...

Yes, indeed. And the specific goal of that mission included landing and recovering the booster.

Nothing in your post was new information to me. Before that mission, Elon said that landing the booster on the barge had about a 50% chance of success.

After that booster landing failed to achieve the goal of this test, quite a few people posted glowing congratulatory comments about its "success". I reacted to that by saying: B.S. It failed! AFIK, Elon never declared that it was a "success".

I'm greatly disappointed by several posts denouncing me for pointing out the obvious. For the record, I will not be silenced by this attempt to bully me into agreeing to a rosy interpretation of what happened. For those involved in that attempt, I suggest that you do one of two things:

1. Complain to Tesla HQ and try to get me banned from their forums, or
2. Get used to the idea that I have as much right to express my views as you do.

In case you haven't noticed, when I am subjected to demeaning responses to my posts, I tend to fight back verbally. Folks who don't like my tone after they demean me have no legitimate complaint. If you want polite, civil words from me, I expect you to earn that by using only polite, civil words directed toward me.

AtlantaCourier | 2015年1月25日

By definition, the test was a complete success. The ultimate goal of any test is to uncover shortcomings that may be present in a process, scheme, device, or whatever. It uncovered an issue with the amount of hydraulic fluid and therefore the test was a success.

Furthermore, the landing attempt itself was highly successful within the scope of the test. No reasonable person expected the rocket to make an absolute 100% perfect landing the first go-round.

Because of the Grasshopper (and later, the modified Falcon 9) tests in McGregor Texas, we know the Falcon 9 first stage can land once it is over actually over a target. Therefore, an actual landing of the stage is not a criteria for success during the first few attempts when you consider the million or so unknowns that occur while rocket is descending to 1,000 meters above the target

The real question is whether or not the rocket, beginning from 50 miles in altitude and 5,000 mile/hour, can guide itself to a point 1,000 meters above a platform in a descent profile that is reasonably close to the descent profiles of the rockets which landed in McGregor.

We only have a few frames video showing the rocket at a horrendously awkward angle. But there are three things to keep in mind.

1.) This was the first attempt
2.) Even at that extreme angle, the rocket was precisely over the target
3.) If the rocket had been at that same angle 750-1000 meters above the ship, then that would have placed it outside of the descent profile of the McGregor rockets. It would never have arrived over the ship in the first place

So from this we know that on the first try, the Falcon 9 first stage successfully intersected the descent profile of the rockets which landed in McGregor. Success.

This was the only criteria for success for a first attempt, because Thats all that remained to be proven. All other aspects of the trick are snugly in the bag!

Now, if this were the fourth or fifth attempt and it was still crashing/exploding, it still wouldn't surprise me and I wouldn't qualify those attempts as failure either.

The video conclusively shows that all the ingredients for a landing are in place and that only minor tweaks remain for the system to work as planned.

Brian H | 2015年1月25日

It was also able to take off again, too. See that thing launch over the side of the barge?? W00t!

Grinnin'.VA | 2015年1月26日

@ AtlantaCourier | January 25, 2015

By definition, the test was a complete success.

In this simple statement, the words "By definition" show that whatever the outcome of this test, you want to call it "a complete success".

IMO, that isn't compatible with the perspective of an objective observer.

AtlantaCourier | 2015年1月26日

Grinnin'

@ AtlantaCourier | January 25, 2015

"By definition, the test was a complete success."

In this simple statement, the words "By definition" show that whatever the outcome of this test, you want to call it "a complete success".

What you just said means that because one test finds what it is checking for, that all tests therefore find what they are checking for.

That makes no sense, and it is certainly not what I said.

I take the reasonable view that negative results are possible just as are the positive ones.

The test uncovered a flaw. But if, by chance, the rocket had landed as planned with the flaw remaining undetected, then the test would be considered a failure and I would call it as such.

And this almost happened.

It was a distinct possibility that I acknowledge. A few more gallons of hydraulic fluid might have allowed a dangerous rocket design to land successfully while a disastrous flaw remained hidden. The test would not have detected any of the problems that were present and therefore the test would have failed in its purpose.

Of course, no one would know it was a failure until later, when it would be too late.

SpaceX's job right now is not to successfully land rockets. SpaceX's job right now is to relentlessly weed out the flaws in the rocket design and with relevant operations without affecting their other commitments in a negative way.

And according to this job description, an actual landing was not considered the sole, crucial, must-do, gotta-have, all-important, criteria for success.

But beyond the primary goals of discovering the flaws, sorting out the unknowns, gaining calibration data, verifying what works and what doesn't, there lies the next level of success - a bonus if you achieve it early in the flight test program.

The next level of success is demonstrating that the rocket can set itself up for "final approach" if you will.

Once here, the landing itself is trivial because SpaceX has already demonstrated in McGregor that a rocket configured and situated as such can land safely and with precision.

So, IMO, the criteria for success here is the arrival of the rocket 1,000 meters above the landing platform in a controlled powered descent where the flight profile matches that of the rockets which landed at McGregor.

And we know this happened, otherwise it never could have crashed into the platform in the first place. The video shows the rocket was under power and not at in final stages of an uncontrolled ballistic free-fall.

It achieved this on the first attempt - something that perhaps wasn't expected until as many as three or four flights.

If you consider this a failure because the rocket landing was just a hair off when everybody expected to rocket to blow up anyway, then in the very strictest of terms and in the most myopic of views, you may technically correct, but the point is somewhat irrelevant.

It's irrelevant because SpaceX has demonstrated mastery in landing rockets at McGregor, and now has demonstrated they can guide a rocket descending from orbit to a point where its flight profile exactly matches the successful McGregor rockets.

After witnessing the attempt, no one doubts SpaceX has this in the bag. Google and Fidelity and God knows how many other companies literally busted down the door at SpaceX after the demonstration. They rushed through the breach with bags of money wanting a piece of this action.

Can't say for 100% sure that SpaceX will ever land a rocket from 50 miles up, but its looking pretty grim for the doubters.

And I continue to stand by my assertion: Because the test fulfilled its purpose, it was a complete success.

Grinnin'.VA | 2015年1月26日

@ AtlantaCourier | January 26, 2015

Grinnin' ...

And I continue to stand by my assertion: Because the test fulfilled its purpose, it was a complete success.

Even though before the mission, Elon described it as a 50-50% chance of success?
IMO, your interpretation is amazingly biased. But you're entitled to your opinion.

Näky | 2015年1月26日

Elon also said he just made up that 50-50 chance of success, because he couldn't know.

AtlantaCourier | 2015年1月26日

@ Grinnin'

If I am amazingly biased, you are a carnival act.

AtlantaCourier | 2015年1月26日

@Grinnin'

Sorry, that was rather uncalled for. But I have to say that everyone in this thread has been nothing but respectful to you, Grinnin', and all you have offered in return is sniping, accusations, and insults.

I'm moving on like the rest of the participants of this thread have. The spirit of constructive dialog has been fouled here and as far as I'm concerned you can rot in here by yourself.

grega | 2015年1月26日

Others have already said it but I'll add my voice :)

It was a failed landing.
It is a successful learning experience.

They want to continually push the envelope as far as they can and expect failure as an integral part of that accelerated learning process. I think this way of learning is a good process and will bring great success, provided the cost of individual failures isn't too high.

(I wonder how far they'll push this envelope on settling Mars though - because an acceptable loss that involves people will not play well to many observers.)

Grinnin'.VA | 2015年1月26日

@ AtlantaCourier | January 26, 2015

@Grinnin'

... everyone in this thread has been nothing but respectful to you

I know respectful when I read it. I have been disrespected here.

I'm moving on like the rest of the participants of this thread have. ... you can rot in here by yourself.

And you pretend to show me "nothing but respect".
Your "you can rot" is a strong insult, and I think you know that.

Good luck.

DTsea | 2015年1月27日

Atlanta courier correctly and eloquently understands the role of test in engineering development.

Grinnin ron does not.

Grinnin'.VA | 2015年1月29日

@ DTsea | January 27, 2015

Atlanta courier correctly and eloquently understands the role of test in engineering development.

Grinnin ron does not.

How do you know what the limits of my understanding are?
BTW, what specifically did I write that was wrong?

DTsea | 2015年1月29日

Well Ron it's about the difference between success definition between development test vs validation tests... thanks for asking, because i think i can now articulate why i reacted negatively to your earlier comments.

Finding the limits of the design is the point of DEVELOPMENT testing. In VALIDATION testing, on the other hand, your viewpoint is right on.... it must be proven to work robustly.

This was a development test, not a validation test, and was successful- wildly successful- as such.

Does that help?

As an engineer it gets tiresome to see people being critical of development hardware learnings. This is why the Russians used to keep their tests secret. In return for how open spacex is, we need to recognize the nature pf what they are doing.

cheers!

Brian H | 2015年1月29日

DT;
+1

Coming up, Feb. 8, we are about to see the fruits of that learning process! This time, the fruits of the pudding will be upright on the barge. ;)

DTsea | 2015年1月29日

The Feb 8 test is ANOTHER developmental test.... measure success by learning!

7thGate | 2015年1月29日

As an engineer, I would like to say that there is a range of success in a test. Tesla's test was, I would say, a moderate success from an engineering standpoint. Also, a test can succeed at producing the desired outcome while still be a near total failure from an engineering standpoint, although that doesn't happen a lot. I would generally classify the outcomes of testing into a couple categories:

Complete success: Everything worked and produced the outcome I expected. All of the data gathered as part of the test matches my predictions, and I understand why the system functioned correctly.

Moderate success, positive failure: The outcome is correct, but not for the reasons expected. For example, there could be a partial malfunction in one piece of the system that causes it to not respond as designed, but a modeling error makes it so that this failure leads to success by keeping another parameter in bounds so a different part of the system takes corrective action to compensate for the issue. In software development, this could be something like "This database query doesn't actually work, but the time it takes to fail happens to prevent threading issues that would crop up and it ends up working out because of error checking somewhere else anyway". This will look like a complete success to an outsider, but it is actually only a partial success because something is going on that you don't understand, and relying on a complicated system that isn't behaving the way you modeled to keep working is not really something you can count on. This is the class of bugs where "My thing works, and I don't know why". To be a moderate success, you need to have gotten back data that you can analyze to figure out why the system behaved this way.

Near total failure, positive failure: The system works, and you have no idea why. Telemetry suggests something went completely wrong; a guidance computer stopped working, software deadlocked, something didn't deploy as designed. And yet, the final output/landing/widget function was correct. These failures are scary as hell because they look good from the outside (you landed/got the right output from your program/widget functioned) and you have no idea why. It can also be hard to design future tests to figure out why your thing is working when it isn't supposed to be, and the bug might actually be in whatever is gathering the data you're analyzing. Fortunately, they are also comparatively rare, since most of the time when things fail hard they fail to produce the desired output.

Moderate success, negative failure: The system didn't work, and the outcome was not what the system was designed to produce. Negative failures are more common than positive failures, because usually when something doesn't match your models, it means you end up with something that does not work quite right. This is a moderate success if you get back data that allows you to understand exactly what did not work right, so you can apply a corrective fix. This appears to be the class I would put the SpaceX failure in, since they apparently got good data on why the rocket failed to land.

Total failure, negative failure: The system failed, and you have no idea why. It could be that all your telemetry or logging failed in some way, or all diagnostic systems report that everything is fine despite crashing and burning, but this type of failed test involves the product not working in such a way that you can't get any useful information as to why it did not work so you can apply a corrective fix.

In general, tests are successes when you get back data that explains why your predictions about what would happen do or do not match what actually occurred. Tests are failures when the data that comes back from the test does not match what you expected to happen and you are not able to figure out why. Whether the output is correct is not necessarily that relevant; it is actually much scarier when something works when the logged data suggests it wasn't supposed to that when it fails and the logged data shows exactly why.

SamO | 2015年1月29日

@DTsea,

Great articulation of a crucial engineering difference.

+1

Red Sage ca us | 2015年1月29日

7thGate: +100 UP! I love that list!

"Near total failure, positive failure: The system works, and you have no idea why."

Possible solutions: MAGIC, ALIENS, or ANGELS.

LOL!

"Moderate success, positive failure: The outcome is correct, but not for the reasons expected."

I think this is what happened with hybrid cars like the Toyota Prius...

Grinnin'.VA | 2015年1月29日

@ DTsea | January 29, 2015

Finding the limits of the design is the point of DEVELOPMENT testing. In VALIDATION testing, on the other hand, your viewpoint is right on.... it must be proven to work robustly.

This was a development test, not a validation test, and was successful- wildly successful- as such.

Does that help?

This does indeed help me understand your perspective.

However, I've seen NOTHING from SpaceX or Elon to indicate that they thought of this test in that way. Elon said prior to the test that they expected to have about a 50-50 chance of "success". After the test they did NOT declare that the test was a success. They said they thought they knew why it had failed. If you disagree with those basic "facts", please provide a link to conflicting information that I missed.

Anyway, in a couple of weeks or so we'll probably find out how the 2nd test of the SpaceX booster barge landing works out. As I said before, I hope they nail it. And if they 'fail' again, I'm confident that they will find and fix the problems. Ultimately I expect SpaceX to achieve this astounding accomplishment. I respectfully reserve my celebration until they actually land a booster on a barge in good enough condition to be refurbished and reused.

Cheers.

rlwrw | 2015年1月29日

What I find ironic about the first successful booster landing is that particular booster will never fly again because SpaceX will be tearing it apart to see what parts can be re-used, re-furbished, and re-flown again. :-P

DTsea | 2015年1月29日

Rlwrw why do you say that?

Näky | 2015年1月29日

Ron, here's link about 50-50 chance. https://www.reddit.com/r/IAmA/comments/2rgsan/i_am_elon_musk_ceocto_of_a...

I think you need to wait for refurbished booster for some time. Few first successfully landed are likely researched for stressed materials etc. They will not risk commercial launches with unsecure components. It's development in progress.

Red Sage ca us | 2015年1月29日

I learn a lot more from chess matches I lose than from those I win.

DTsea | 2015年1月30日

Red sage +100

Nice metaphor!

Grinnin'.VA | 2015年1月30日

@ Red Sage ca us | January 29, 2015

I learn a lot more from chess matches I lose than from those I win.

Just a reminder: I never, ever said or suggested that SpaceX didn't learn from the recent test attempt to land a Falcon 9 booster on a barge.

I have far too much respect for SpaceX to think such a thing.

Dalec | 2015年2月2日

I'm enjoying the back-and-forth discussions about whether or not the Falcon 9R booster landing attempt was successful.

Just to put things in perspective, the Falcon 9R mission was a complete success. It placed a Dragon capsule into orbit and docked with ISS. Everything else was gravy.

It must be nice to have your launch payload clients (NASA in this case) bankroll your R&D. Genius!

Red Planet, here we come!

Brian H | 2015年2月3日

The upgrades to the F9 booster to make it a F9R were paid out of SpaceX's general profits. They will result in SpaceX having a 100:1 cost advantage over other launchers, instead of just the 4:1 one they now have. Every other launch system will be almost immediately obsolete. Fortunately, SpaceX will be aided in meeting the huge demand by being able to re-use rockets instead of making new ones for every launch!!

;D

grega | 2015年2月3日

It's certainly a worthy goal, and I think they'll succeed.

I actually think a plane-based launch may prove to make more sense though, which will be interesting to see. An early Falcon Air design was heading that way in 2011, but I THINK that SpaceX decided that they really wanted much larger rockets, and the plane wouldn't move them towards that.

http://www.nasaspaceflight.com/2011/12/stratolaunch-rutan-designed-air-l...

A plane based launch system gets reusability by having the plane as the first stage, jet powered, and returning after launch. But this form of reuse, and this form of landing, can not work on Mars. Powered decent is the only option, and I think that's another part of SpaceX thinking.

Brian H | 2015年2月4日

Plane-based high altitude drop-rocket launches, whether the X15 or the Virgin version are inherently small-scale, not relevant for SpaceX.

rlwrw | 2015年2月4日

StratoLaunch is making the world's largest plane specifically for launching small to medium size rockets. Orbital Sciences will be making the rocket.
Orbital still launches their small Pegasus rocket from an L-1011
White Knight One, which air launched SpaceShip One has dropped numerous test articles for NASA. In fact, when NASA got the use of WK1, they retired their B-52.
Air launch systems do have the flexibility of launching almost anywhere in the world for very specific orbit insertions, being able to launch almost any time, and not having the overhead of a ground based launch facility.
Expect to see nano-satellites launched this way.

Red Sage ca us | 2015年2月4日

Finally! Thunderbirds are GO!

.

5fu2h

EmperorTytus | 2015年2月8日

Feb 8 launch aborted due to range radar malfunction. Try again Feb 9 at 4:08pm Eastern. Watch live on spacex.com.

EmperorTytus | 2015年2月8日

Correction: Feb 9 at 6:08pm Eastern.

grega | 2015年2月8日

@BrianH wrote: Plane-based high altitude drop-rocket launches, whether the X15 or the Virgin version are inherently small-scale, not relevant for SpaceX.

True it's more suited to smaller scale, which was the reason SpaceX gave for dropping that partnership iirc. I still think it's a worthy evolution alongside what SpaceX is doing. Old rockets will be ... old.

(For some reason, I want to see SpaceX doing a magnetic railgun launch assist.... just for the first 500m up ;-) )

Brian H | 2015年2月8日

USAF Eastern Range radar went down! Wonder how the #?(8 that happened.

Railgun projectiles at Mach 25 orbital velocity would explode or burn in dense lower atmosphere.

grega | 2015年2月8日

Yes, USAF needs a Tesla battery backup system installed pronto.

"Railgun projectiles at Mach 25 orbital velocity would explode or burn in dense lower atmosphere"

I don't see why they'd need to get to orbit from an assist though.

If it could accelerate at 4G (so the cargo would experience 5G) it'd only be doing 712km/h as it reached 500m altitude. Then it would be up to the regular rocket engine to do the rest - so the rocket would suddenly accelerate far less as it relies on engines accelerating the weight of full fuel tanks.

Their are many tonnes of fuel lost before that speed is reached now.

EmperorTytus | 2015年2月9日

Due to weather, Falcon 9 launched rescheduled: Tuesday, Feb 10 at 6:05 p.m. EST.

Brian H | 2015年2月9日

Fuel costs are trivial compared to booster costs; re-usable rockets are the future, not rail guns.

grega | 2015年2月9日

I agree Brian. You misunderstand me entirely. Forget it :)

grega | 2015年2月9日

For the record I think spacex is doing exactly the right thing.

EmperorTytus | 2015年2月11日

Falcon 9 launch attempt again today, Feb 11, at 6:03 PM EST live in 720p HD on spacex.com.

JPPTM | 2015年2月11日

Will not be able to attempt barge landing due to very rough weather/seas at barge site. Still will try 'soft' landing at sea level.

Brian H | 2015年2月11日

A soft landing on 3 storey waves should be exciting.

EmperorTytus | 2015年2月14日

From spacex.com:

"While extreme weather prevented SpaceX from attempting to recover the first stage, data shows the first stage successfully soft landed in the Atlantic Ocean within 10 meters of its target. The vehicle was nicely vertical and the data captured during this test suggests a high probability of being able to land the stage on the drone ship in better weather. "

Brian H | 2015年2月14日

Vertical despite howling winds -- apparently those fins do their job!

EmperorTytus | 2015年3月22日

Next Falcon 9 rocket vertical landing opportunity is April 10th during the ISS resupply mission. Current lauch time is 5:42PM EST. With any luck we'll have good weather, nice sunshine, smooth seas, and a heck of a show!

nikolateslas88 | 2015年3月22日

rockets do have a slight gyroscopic spin when they take off for stabilization. im sure its the same when landing. its a few degree turn so it looks like the rocket really isnt spinning, but the large mass with the slight turn gives stabilization. i think it can be seen when the shuttles taking off, its a slight slow rotation. from what i have read....... im sure its been answered already lol

Grinnin'.VA | 2015年3月22日

@ nikolateslas88 | March 22, 2015 new

rockets do have a slight gyroscopic spin when they take off for stabilization.

Yes. However, to pull off a barge landing, the rockets need to stop spinning. Otherwise, undoubtedly minor movement by the barge as the rocket 'touches down' would destabilize the spinning rocket causing it to fall down.

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