Author Topic: SpaceX Falcon 9 v1.1 - Dragon - CRS-4/SpX-4 - Sept 20, 2014 - DISCUSSION THREAD  (Read 268798 times)

Offline Silmfeanor

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Any word yet about the state of the dragon, ie water intrusion, experiments returned?

Offline TO

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http://en.wikipedia.org/w/index.php?title=SpaceX_reusable_launch_system_development_program

now reads:

"Test flight 4
[...]
 and the booster again obtained a zero-velocity at zero-altitude simulated landing on the sea surface.[84] "



Is this User N2e 's interpretation of [84] Morring, Frank, Jr. (2014-10-20)? "[...] and then reignit[ed] to lower the stage toward a propulsive “zero-velocity, zero-altitude” touchdown on the sea surface."
http://aviationweek.com/space/nasa-spacex-share-data-supersonic-retropropulsion

Emphasis mine; sorry I am lacking time, energy and knowhow to talk to N2e while NSF's info, including Elon Musk-SpaceX  Interview at MIT AeroAstro, Oct 2014, seemingly points otherwise, e.g.
Soft ocean landing twice thus far, so CRS-4 probably failed to do that.



Noting that soft landing was not SpaceX' advertised goal, can we rather venture that SpaceX' lack of feedback reflects their caution about interference around a combination of projects:
1.  the Propulsive Descent Technologies
2.  SpaceX challenging Blue Origin's rocket-landing patent
3.  SpaceX requesting FAA's landing permit ?
« Last Edit: 10/27/2014 04:02 PM by TO »

Offline cscott

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I tweaked the article to follow the Aviation Week wording more closely, and left a comment on the talk page pointing to the transcript of Elon's interview at MIT.

Offline kraisee

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I don't believe that Space-X even attempted a soft landing with CRS-4's first stage.

From the available evidence, I think NASA may have actually suggested they utilise the stage (which they weren't actually expecting to recover, regardless) in order to generate the very best possible data regarding high-speed re-entry in a high-altitude re-entry environment that has application towards Mars conditions -- specifically a profile that resulted in creating the thermal re-entry video that we have all enjoyed seeing.

Altering the re-entry trajectory in this fashion would likely use all the remaining propellant that would have been used in a landing attempt, so my guess is that the stage either broke-up when it hit the thicker atmo, or just crashed into the water.   Either way, no real loss, but a great way to get useful, early, data that has use for later missions.

Space-X are not discussing the lack of a landing simply because they have a multitude of detractors who may try to turn it into an "oh they failed on their third try" commentary and they would prefer not to give them any ammo.

Of course, the internet being what it is, that accusation is still going to continue to percolate in some circles, even after CRS-5 takes much of the attention off of CRS-4.   From where I sit, I think Space-X would be wise to nip it in the bud sooner, rather than later and tell everyone what they did, why they did it and explain how it meant they decided not to even try for a landing this time.

Ross.
« Last Edit: 10/27/2014 07:43 PM by kraisee »
"The meek shall inherit the Earth -- the rest of us will go to the stars"
-Robert A. Heinlein

Offline guckyfan

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Wasn't there a statement by NASA that they could not record the landing burn because of cloud cover? That implies there was a landing burn, or at least one was planned. They don't count it as landing, because there were no legs.

Offline cscott

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Wasn't there a statement by NASA that they could not record the landing burn because of cloud cover? That implies there was a landing burn, or at least one was planned. They don't count it as landing, because there were no legs.

The statement was:
Quote from: AviationWeek link=http://aviationweek.com/space/nasa-spacex-share-data-supersonic-retropropulsion
The final, single-engine touchdown was out of the cameras’ fields of view because of clouds, but the project plans to image at least one more Falcon 9 launch and may be able to capture the entire first-stage descent trajectory, if weather permits.

This was a reporter's statement, not a direct quote from either SpaceX or NASA, however, so it's possible the reporter slightly misunderstood a use of the subjunctive tense for CRS-4.  Or else that there was a landing burn, but it did not completely kill the vertical velocity due to the lack of legs.  Or else that there was a zero-velocity-at-zero-altitude landing.  It's impossible to say (although Elon's statement at MIT makes the last one unlikely).

Offline Jcc

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One of the difficulties with landing on the water is the radar used to measure distance to the ground during landing burn doesn't work as reliably over water (this was discussed a few months ago). If the measurement is off they could overshoot or come to zero v too high above the water. Second question is whether the lack of legs meant the stage spun up. No mention of this happening, but it's a question to consider.

Really, I think they have learned as much as they need to at this point about landing on water.  It results  a destroyed stage no matter how softly you land. Next up, land on a barge, and hopefully that will be 100% successful.

Offline cscott

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Really, I think they have learned as much as they need to at this point about landing on water.  It results  a destroyed stage no matter how softly you land. Next up, land on a barge, and hopefully that will be 100% successful.

We don't have the telemetry, but they do.  From Elon's statements it appears that they have been steadily improving their landing accuracy, but that they aren't quite where they want to be yet.  I think there are a lot more non-land landings coming up in 2015, and I don't think they've learned everything there is to learn yet.

Offline Jarnis

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I predict once they have wheeled in 2-3 intact stages in a row from a barge, they'll have a permit to try on land. Probably in 2015.


Offline guckyfan

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Really, I think they have learned as much as they need to at this point about landing on water.  It results  a destroyed stage no matter how softly you land. Next up, land on a barge, and hopefully that will be 100% successful.

We don't have the telemetry, but they do.  From Elon's statements it appears that they have been steadily improving their landing accuracy, but that they aren't quite where they want to be yet.  I think there are a lot more non-land landings coming up in 2015, and I don't think they've learned everything there is to learn yet.

They did not have a stage coming down equipped with grid fins. They will need that for precision landing and may need one landing with them to get all the data they need to succed on second try. That's likely IMO where the 50% success chance comes from, that Elon Musk mentioned.

Or he was just cautios. He gave a low chance of success to the Cassiope stage as well.


Offline Robotbeat

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I predict once they have wheeled in 2-3 intact stages in a row from a barge, they'll have a permit to try on land. Probably in 2015.
That's actually really lame if true. FAA or whoever expects them to violate Blue Origin's patent before being cleared to land?
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline woods170

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I predict once they have wheeled in 2-3 intact stages in a row from a barge, they'll have a permit to try on land. Probably in 2015.
That's actually really lame if true. FAA or whoever expects them to violate Blue Origin's patent before being cleared to land?
That patent is in the process of going away.

Offline RonM

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I predict once they have wheeled in 2-3 intact stages in a row from a barge, they'll have a permit to try on land. Probably in 2015.
That's actually really lame if true. FAA or whoever expects them to violate Blue Origin's patent before being cleared to land?
That patent is in the process of going away.

That is not a given. The process has to go through the courts and could easily end up in appeals. It could take years to be resolved.

Offline Type2

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Patents are only enforced to recoup commercial damages. If Spacex decides to land on a barge as part of a self funded development project (and dont get any payment associated with the landing) then there is no harm to the patent holder. If Spacex started to sell barge landings, then it would be very different.

Offline mheney

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The commercial damage is failure to collect licensing fees for use of the patent.  SpaceX is using the patent to develop and market an (arguably) commercial capability that will (arguably) lead to increased profits once placed into service.  Assuming the patent is valid, the patent-holder has the right to protect their invention, either through exclusive use or licensing.

Offline woods170

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The commercial damage is failure to collect licensing fees for use of the patent.  SpaceX is using the patent to develop and market an (arguably) commercial capability that will (arguably) lead to increased profits once placed into service.  Assuming the patent is valid, the patent-holder has the right to protect their invention, either through exclusive use or licensing.
Yes, but only if the patent is specific enough and held up in court under challenge. However, there is substantial doubt that BO's patent is specific enough. A very similar 'barge landing' method was published at least twice in open literature before BO issued the patent. BO failed to cite these public sources and that could be reason to overturn the patent.
IMO the patent will go away. It's not specific enough. And yes, I think SpaceX will take the risk of performing a barge landing before the BO patent is overturned.
« Last Edit: 10/28/2014 02:01 PM by woods170 »

Offline Robotbeat

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Right, so as things stand, FAA is either already taking a side in the BO patent dispute or they basically expect SpaceX to have to violate the patent... IF it's true that they demand SpaceX land on the barge first before on land. And I don't think that's true.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Online abaddon

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Right, so as things stand, FAA is either already taking a side in the BO patent dispute or they basically expect SpaceX to have to violate the patent... IF it's true that they demand SpaceX land on the barge first before on land. And I don't think that's true.

The FAA (and USAF, let's not forget) have a right to determine what capabilities must be demonstrated before they will allow an attempt to land the stage near the launch site.  It's not their fault that the BO patent exists, and they should not and cannot allow their requirements to be compromised because it exists.

And as you say, we have no insight into what the requirements are, so this is speculative anyway.
« Last Edit: 10/28/2014 02:10 PM by abaddon »

Offline Jim

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The FAA (and USAF, let's not forget) have a right to determine what capabilities must be demonstrated before they will allow an attempt to land the stage near the launch site.  It's not their fault that the BO patent exists, and they should not and cannot allow their requirements to be compromised because it exists.


It is only the USAF.

Offline baldusi

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BTW, the patent includes a beacon on the landing platform as part of the claims. No beacon on platform, no patent infringement.

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