SpaceX News

[DeltaV]

If you are not going to read at least the abstracts of the papers I post, why should I read yours?

Paper 1 reduces coherence (same as reducing thermal power over the same area)

"...the energy degeneration for partially coherent beams is only 50% of that for fully coherent beams"

How does reducing coherence (primarily phase and frequency match, not parallelness of the combined beams) reduce the cumulative energy absorption at the target if it reduces losses while getting to the target?

Paper 2 reduces time of pulse laser (natural thermal dissipation of object will be far superior to thermal energy transferred to the the target at the same "time scale" level.)

"...making possible the very-long-range guiding and distant projection of high-energy laser pulses and high-average power beams".

From the body of the paper:

If a high-power laser is pulsed for Δt
∼2 ms, consistent with the lifetime of our 10-Hz-generated
thermalwaveguides, the peak average power can be 1.3MW.
It is possible that in such environments, air heating by the
filament array itself could help dissipate the aerosols before
the high-power beam is injected, further raising the thermal
blooming threshold and also reducing aerosol scattering. An
air waveguide even more robust against thermal blooming
and capable of quasicontinuous operation may be possible
using kHz-repetition-rate filamenting laser pulses.

Paper 3 reduces time and switch to a wavelength that reduces even more the total thermal power of the laser as in paper2.

The main use of a laser like in paper 3 would be for producing a waveguide that guides a separate high average-power beam. Filamentation and self-guiding at very high pulse powers may also yield interesting beam-plasma interactions, but that is much more speculative and I'm not proposing it here.

A surprising breakthrough requires technological and theoretical advancements we simply have not reached yet. That's why I stated that the idea of a laser shooting down SpaceX latest launch is not possible at today technological and theoretical knowledge level.

Oops, I left off the question mark. Maybe you'll comprehend it now:

Should one blindly accept your statement that anything should not be believed simply on the basis of "it's false and I can prove it because it's not unclassified!"?

Anyway, it is my engineering judgement that, extrapolating into the classified realm from public domain research, a single-use laser capable of fitting into a ConEx box and covertly bringing down a soft target like a liquid fuel booster is possible under 100 km. Is that the same as saying that this is what happened with CRS-7? No.

You will be happy to know that I no longer feel that the bright spot fade above was due to a laser transient. I found a better quality video that suggests it was turbulent vapor temporarily blocking a reflection from a protuberance. Is that the same as saying a laser did not bring down CRS-7? No.

SpaceX data may be released on Friday. I'm through with this for now.

[Giorgio]

If you are not going to read at least the abstracts of the papers I post, why should I read yours?

Differently from you I do not post abstracts. I only post full readable papers.
Anyhow I do read the abstracts you supply but you can't evaluate the real content of a paper from them as they are just a summary, or recapitulation, or synopsis, or summation, or condensation, in other words they are just WORDS ABSTRACTS without the fundamental logic and mathematical steps that clarify the real meaning of those few introductory words.

Paper 1 reduces coherence (same as reducing thermal power over the same area)

"...the energy degeneration for partially coherent beams is only 50% of that for fully coherent beams"

How does reducing coherence (primarily phase and frequency match, not parallelness of the combined beams) reduce the cumulative energy absorption at the target if it reduces losses while getting to the target?

Well...... with this reply you just proved to everyone that you don't understand much about lasers and yet you are here trying to discuss about advanced laser physics..... interesting fellow you are.
I strongly suggest you get some basic knowledge about Lasers theory and physics if you wish to further discuss about them.
Even the 1992 paper I supplied to you twice, has most of the answers you need written inside.
If that paper was too difficult for you to follow than do start from the "Photonics Encyclopedia" definition pages:
http://www.rp-photonics.com/coherent_be ... ining.html

When you will be familiar with the basics you can read this:
https://www.ll.mit.edu/publications/jou ... optics.pdf
This paper does a good job at explaining the 3 basic conditions for getting a high radiance beam from a laser.
I will just quote you the first of the three:

To obtain high radiance from a laser array, three conditions must be met.
First, the lasers must be mutually coherent; that is, they must be phase and frequency locked to one another.
Without coherence, any beam emanating from the array would spread, reducing the radiance of the output.

And

Consequently, although it may provide high optical power, an incoherent array's radiance level is relatively low.

Study and, once you are done educating yourself on the subject, if you still think to have a point about high altitude laser feasibility and you want to make a real, serious and technical discussion on lasers I am here.

[DeltaV]

Differently from you I do not post abstracts. I only post full readable papers.
Anyhow I do read the abstracts you supply but you can't evaluate the real content of a paper from them as they are just a summary, or recapitulation, or synopsis, or summation, or condensation, in other words they are just WORDS ABSTRACTS without the fundamental logic and mathematical steps that clarify the real meaning of those few introductory words.

I did post full paper links for 2 out of 3. The pdf download direct from China did not work for me. Maybe it will for you, since you are there and can bribe somebody. If not, here is an html link (Shields Up!).

That is a peer-reviewed paper anyway... the clear statement in the abstract should be sufficient for you. Or do you not believe in peer review?

Well...... with this reply you just proved to everyone that you don't understand much about lasers and yet you are here trying to discuss about advanced laser physics..... interesting fellow you are.
I strongly suggest you get some basic knowledge about Lasers theory and physics if you wish to further discuss about them.

Your links to 27 and 23 year old works are most impressive and are certain to capture the latest developments in laser research. Just a reminder, we are in the 21st century.

Read and learn (for a change).

High-Power Fiber Lasers for Directed-Energy Applications
http://www.nrl.navy.mil/content_images/08FA3.pdf

We compared the propagation
efficiency of coherent and incoherent combining
and found that under typical atmospheric conditions
and propagation ranges, the propagation efficiency
of incoherently combined single-mode fiber lasers is
nearly identical to the theoretical upper limit for coherent
combining. Hence, there is no inherent advantage
to coherently combining beams for tactical directed energy
scenarios.

Incoherent Combining of High-Power Fiber Lasers for Long-Range Directed Energy Applications
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA452452

This incoherent beam combining configuration is readily scalable to higher CW
powers. For example, a 500 kW HEL system would require ~ 200 fiber lasers (2.5
kW/fiber), have a beam director radius of ~ 65 cm, and the fiber lasers would occupy a
volume of ~ 150 m^3 .

Incoherent Combining of Fiber Lasers Developed for Directed Energy Applications
http://www.nrl.navy.mil/media/news-rele ... plications

Incoherent combining of fiber lasers has a number of advantages," Sprangle said. "It does not require phase locking or polarization locking of the individual lasers and can be readily scaled up to a compact and reliable directed energy system.

There are many other sources. If you are too lazy to read, that is not my problem.

[Giorgio]

Differently from you I do not post abstracts. I only post full readable papers.
Anyhow I do read the abstracts you supply but you can't evaluate the real content of a paper from them as they are just a summary, or recapitulation, or synopsis, or summation, or condensation, in other words they are just WORDS ABSTRACTS without the fundamental logic and mathematical steps that clarify the real meaning of those few introductory words.

I did post full paper links for 2 out of 3. The pdf download direct from China did not work for me. Maybe it will for you, since you are there and can bribe somebody. If not, here is an html link (Shields Up!).

I am sure you cultural sarcasm helps you a lot to overcome your lack of knowledge of physics. Yet I do not understand why you felt the need to resend this paper.
You are probably convinced that this paper support your arguments, but unfortunately it does not.

Let me help you to understand. This paper states some absolute conditions, they are:
1) "Low Power" (10 Kw the power used in the calculations of the paper)
2) "Low Range" (less than 5 Km as for Rayleight length formula )
3) "small Altitude variation"

Reason "1" is to limit the onset of Thermal Blooming effect (see Eq.16 of the paper), thus removing the biggest contributor to beam degradation.
Reason "2" is a direct consequences of the laser wavelength used (1 um, to limit water vapor absorption of laser energy and calculated according the well known Rayleight length formula)
Reason "3" is to limit the effect of Atmospheric Turbulence (that is dependent on Altitude, see Eq.13+14), and limit even more the onset of Thermal Blooming which also depends on Temperature, Altitude, Density, Refractive index, and another half dozen variables, as you can see from Eq. 17-18-19.

Let's now see the final results of the paper:
Figure 6a, gives us 4 lines for the transmitted power over distance Z and NO turbulence situation.
Two lines for Partially Coherent Laser (with and without "simplified" blooming), Line with a dot and Line with a star.
Two lines for Fully Coherent Laser (with and without "simplified" blooming), Solid Line and Segmented Line.
The two "Partially Coherent" lines are ENCLOSED by the two "Fully Coherent" lines. In physics this means that the "the partially coherent beams are less sensitive to the thermal blooming effect (under those optimistic conditions). But anyhow the best radiance level still belongs to the fully coherent Segmented line (that's the line in the top in case you got lost).
And Figure 6b gives you a glimpse of reality showing you the radiance drop for all lines if you decide to point the laser vertically and in semi realistic turbulence conditions. Your range immediately passes from a theoretical of 10 km to a ridiculous 2 Km.

So, the very same paper that you are presenting to prove your statement is showing us that you are wrong on all the points.
Point 1: Coherent laser gives a better radiance level than partially coherent laser (even if more sensible to Thermal blooming).
Point 2: Laser effective distance of a laser array is not depending on the total power of the array but on the single laser wavelength and beam spot size, according the Rayleigh range formula. In other words, using the same laser, a 500KW or 10 MW will give you the same maximum distance.
Point 3: Thermal blooming is the greatest cause of laser beam degradation, reducing effective range to a shape similar to the one on Figure 6b once its effect is accounted.
Point 4: A 27 years old paper on natural laws and related physics still hold true in 21st century! Amazing, uh?
But you see, the only difference from 27 years ago and now is that 27 years ago students was actually requested to read books and understand a subject before they was allowed to pass a course. While it seems that nowadays all what is requested from "pseudo" Engineers is to be able to use Google and Wikipedia without making any sense of what they are reading.

Luckily we have DeltaV with his axioms on "adaptable natural laws" and his "parallelness of the combined beams" to enable Mambo Jambo technologies!
Really sad times for our category.....

And I didn't bother to dissect the other 3 papers you linked as they are the same as this one, same assumptions and same results. I wonder if you did actually even read them.
Anyhow, welcome to reality.


Edited to fix spelling.

[mvanwink5]

Well, no word from SpaceX yet that I have seen. Perhaps they are putting various hypotheses to a battery of elimination tests. Also, perhaps they are inspecting tanks for construction flaws. All just guesses on my part. It does seem to underline the obscurity of the problem and / or continued trouble with laying out the timeline.

Looking forward to what SpaceX has to say, whenever they figure it out. Worse case is the failure remains unknown. Possible?

[Giorgio]

Looking forward to what SpaceX has to say, whenever they figure it out. Worse case is the failure remains unknown. Possible?

Highly possible, especially in view of Elon first statement after rocket explosion that "Data suggests counterintuitive cause."
The good news is that if they do indeed pinpoint the cause it might boost overall safety of future crafts.

[Skipjack]

Elon Musk tweeted on Friday:
Model S product call at 11 today. Rocket discussion at noon on Monday.

[Skipjack]

Todays press conference by SpaceX revealed the preliminary results of the investigation.
It seems like one of the struts holding the helium bottle in place failed due to faulty grain structure in the steel. After they had narrowed down the problem, they tested several thousands of them and found that some of them would fail way below their certified rating. This strut was designed to handle 10,000 lbs of load, but some failed at 2,000 lbs. The failure is rather rare, so it never caused any problems until now. They will move to a different supplier for the strut and will probably inconel instead of steel.
http://forum.nasaspaceflight.com/index. ... =37739.360

[Giorgio]

This strut was designed to handle 10,000 lbs of load, but some failed at 2,000 lbs. The failure is rather rare, so it never caused any problems until now. They will move to a different supplier for the strut and will probably inconel instead of steel.
http://forum.nasaspaceflight.com/index. ... =37739.360

Kudos to SpaceX teams for pinpointing the issues in such a short time.

As a Mechanical Engineer I can say that this sucks big times. If you can't trust your suppliers on such basic issues at the level of certifications that the suppliers must have to supply space industries one has to wonder what is really going on with suppliers in less strict environments.

[mvanwink5]

One point in going to 'inconel' is that it takes a significantly better welder to certify than for steel. Those welds will be better if for no other reason.

Super good news.

[Giorgio]

From the same nasaspaceflight.com thread:

Did some material analysis, problem w/ grain structure

I would love to know more about what they found out and what the original specifications was supposed to be.
This is one of the time when it sucks not to have a job in SpaceX just to satisfy my curiosity.

[Tom Ligon]

I've run into inconel parts on spacecraft before. It can achieve 300 ksi 0.02% yield strength ... remarkable stuff. It also is ridiculously difficult to work with ... give this to a machinist, tell them how you want it machined, come back a few hours later and they'll chase you out of the shop with a large wrench. They hate it worse than they hate titanium.

[paperburn1]

I really do not see the need for a jump to this grade. Considering what was there was acceptable, a QA program and looking into something designed slightly different would solve your problems. (thicker tubewall?)

[paperburn1]

What I found interesting was the dragon cargo vessel did not have self preservation built into the software model. I would have taken this for granted.

[Giorgio]

I've run into inconel parts on spacecraft before. It can achieve 300 ksi 0.02% yield strength ... remarkable stuff. It also is ridiculously difficult to work with ... give this to a machinist, tell them how you want it machined, come back a few hours later and they'll chase you out of the shop with a large wrench. They hate it worse than they hate titanium.

Ceramic inserts are making life more easy in the last years. Still not something you want an inexperienced Machinist to handle, or he will burn through your monthly stock of costly tools in few hours....