Author Topic: Refurbishment of Used Stages/Vehicles  (Read 206710 times)

Offline envy887

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Re: Refurbishment of Used Stages/Vehicles
« Reply #620 on: 03/29/2017 06:04 PM »
As far as I know, Grasshopper was the first reusable VTVL demonstration of the major component of an orbital launch system - that component being the F9 v1.0 booster airframe.

The other VTVL demos did not use (most of) the first stage of an orbital system.

Offline john smith 19

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Re: Refurbishment of Used Stages/Vehicles
« Reply #621 on: 03/29/2017 09:20 PM »
Actually, I have done a disservice to the DC-X which was I believe the first to do it.

I have no problem with people 'firsting', but when the statement is clearly false, it should not be left to stand. Grasshopper was not the start of the history of first stage reuse.
In fact you could go back to the Apollo landing and takeoff simulator.

The key item you are missing from all of these  situations is the high aspect ratio  of the structures involved.

All previous examples either were relatively "squat." Grasshopper was the first (AFAIK) to tackle the issues around landing what is a (relatively) floppy structure head on. The fact it took multiple attempts and the addition of grid fins to make it work suggests a fair bit of science had to be done and that all earlier proposals would not have actually worked. Something you only discover when you do engineering, rather than writing grant proposals.   
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Offline manoweb

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Re: Refurbishment of Used Stages/Vehicles
« Reply #622 on: 03/29/2017 11:45 PM »
SO I came to this thread from the SES-10 one. There was a user concerned about the possible failure of that first stage because it survived a hot re-entry.

Maybe this has discussed before - I did not find that. An no, apparently people need to have this disclaimer, I am not trying to "second guess" SpaceX.

To the point: I am absolutely not an aluminium-lithium alloy metallurgist, but are there chances that the hot re-entry might have annealed the alloy and made it lose certain properties? For the very little I know, aluminium anneals at relatively low temperatures. I know they have tested the stages apparently with a "top" hold-down, so that the thrust generated by the engines is applied to the structural parts of the rocket. Just wondering what more experienced people think of the issue.

Offline Herb Schaltegger

Re: Refurbishment of Used Stages/Vehicles
« Reply #623 on: 03/30/2017 12:08 AM »
SO I came to this thread from the SES-10 one. There was a user concerned about the possible failure of that first stage because it survived a hot re-entry.

Maybe this has discussed before - I did not find that. An no, apparently people need to have this disclaimer, I am not trying to "second guess" SpaceX.

To the point: I am absolutely not an aluminium-lithium alloy metallurgist, but are there chances that the hot re-entry might have annealed the alloy and made it lose certain properties? For the very little I know, aluminium anneals at relatively low temperatures. I know they have tested the stages apparently with a "top" hold-down, so that the thrust generated by the engines is applied to the structural parts of the rocket. Just wondering what more experienced people think of the issue.

At risk of being labled a concern-troll again by even discussing this further, I think the answer to this one is "No." SpaceX has now had over a year to analyze a number of returned stages, and longer still to analyze crashed debris from earlier failed attempts. Metallurgical tests are absolutely the first thing the structural engineers in charge of the program would want to do, and a lot of them, from all parts of the structure from octoweb to the top of the first stage where it mates to the interstage, and any number of points in between. Visual microscopic exams, x-ray tests, dye-penetrant tests, eddy-current tests and many more whose names and details I've long since forgotten about. To the extent that thermal-related loss of strength is an issue with returned stages, I think SpaceX will by now have characterized it pretty well, at least as to the parts of the structures they've tested.
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Offline Lars-J

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Re: Refurbishment of Used Stages/Vehicles
« Reply #624 on: 03/30/2017 12:10 AM »
I would be more concerned if the structure was some relatively new alloy (or composite), but the properties of these aluminum alloys seem to be pretty well understood.

Offline cppetrie

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Re: Refurbishment of Used Stages/Vehicles
« Reply #625 on: 03/30/2017 12:30 AM »
There was a user concerned about the possible failure of that first stage because it survived a hot re-entry.
I thought this relaunch was using a booster used for CRS-8, which was not a hot re-entry inasmuch as it used a boost back burn to return to LZ1 and wasn't a high speed hoverslam landing.

As was mentioned by Herb they have likely exhaustively tested samples from returned pieces. I would also think that thermal protection is applied anywhere that heat weakening of the structure is a possibility. I couldn't find anything in a google search about the annealing temp, but Al-Li alloys tend to have melting temps on the order of 500-600 degrees C.

Offline manoweb

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Re: Refurbishment of Used Stages/Vehicles
« Reply #626 on: 03/30/2017 05:22 AM »
Hey guys - I know that SpaceX did all the theory, tests, research, and analysis, and they know the properties of the materials. It's obvious :) I'm not disputing that come on.

I guess my question should have been:
- anyone knows, assuming aluminium-lithium alloys can be annealed, what kind of preventive measures they might have taken to prevent that happening during re-entry?

In fact, being this stage from CRS-? mission makes sense as a first step, even if they will probably plan to reuse also hotter stages in the future. Sure they might have put thermal protection in some spots but we know the bulk of the "cylinder" only has paint to protect it. Maybe the simple answer is that there is no metallurgical concern :)

Offline FutureSpaceTourist

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Re: Refurbishment of Used Stages/Vehicles
« Reply #627 on: 03/30/2017 05:50 AM »
Cross-posting for reference:

Question.  Does anyone know - and I apologize if this has been answered elsewhere - if B1021 will be flying this time with its original engines?  We know that they were removed after its first flight.

 - Ed Kyle
In the Q&A with the SES CTO he stated that no engines were replaced and that the booster is essentially all the original parts. No significant part replacements occurred.

The relevant question and answer start at about 14:40.
Yesterday's SES press briefing



Edit: including reference to video

Offline rpapo

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Re: Refurbishment of Used Stages/Vehicles
« Reply #628 on: 03/30/2017 11:32 AM »
I thought this relaunch was using a booster used for CRS-8, which was not a hot re-entry inasmuch as it used a boost back burn to return to LZ1 and wasn't a high speed hoverslam landing.

As was mentioned by Herb they have likely exhaustively tested samples from returned pieces. I would also think that thermal protection is applied anywhere that heat weakening of the structure is a possibility. I couldn't find anything in a google search about the annealing temp, but Al-Li alloys tend to have melting temps on the order of 500-600 degrees C.
Actually, it was even easier.  They did use a small boostback, and a near vertical reentry burn.  But the small boostback was because CRS-8 did not land at LZ-1, but rather further downrange, on the barge.

Lightly used, indeed, in comparison with the comsat launches.
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Offline Lar

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Re: Refurbishment of Used Stages/Vehicles
« Reply #629 on: 03/30/2017 12:15 PM »
I thought this relaunch was using a booster used for CRS-8, which was not a hot re-entry inasmuch as it used a boost back burn to return to LZ1 and wasn't a high speed hoverslam landing.

As was mentioned by Herb they have likely exhaustively tested samples from returned pieces. I would also think that thermal protection is applied anywhere that heat weakening of the structure is a possibility. I couldn't find anything in a google search about the annealing temp, but Al-Li alloys tend to have melting temps on the order of 500-600 degrees C.
Actually, it was even easier.  They did use a small boostback, and a near vertical reentry burn.  But the small boostback was because CRS-8 did not land at LZ-1, but rather further downrange, on the barge.

Lightly used, indeed, in comparison with the comsat launches.

Therefore a good first reuse candidate, all else being equal, compared to stages that had a far higher heat regime.

Manoweb's question about what they might have done to prevent annealing is interesting but I suspect the answer is proprietary... I bet ULA would love to know. (maybe 10 years from now at a metallurgical society conference?)

(mod hat) Herb: I think no one could call a statement like "I am sure SpaceX thought of this and here's a long list of things they almost certainly did to alleviate it so don't worry" anything close to "concern trolling"  :) ... certainly not me. This is the sort of vigorous discussion we want.

« Last Edit: 03/30/2017 12:21 PM by Lar »
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Offline LouScheffer

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Re: Refurbishment of Used Stages/Vehicles
« Reply #630 on: 03/30/2017 12:48 PM »
but are there chances that the hot re-entry might have annealed the alloy and made it lose certain properties? For the very little I know, aluminium anneals at relatively low temperatures.
I have not seen this mentioned, and it's completely obvious, but I'm sure the very first thing SpaceX did is to measure the temperature reached by the various pieces during each re-entry.  Presumably they would plaster as many temperature sensors as practical over the stage, then use models to compute the temperature of places they could not directly measure.  Plus perhaps IR imaging during flight or other methods of recording peak temperature as well.

So for the places that did not get too hot, there should be no worry about annealing.  For the places that did get hot enough to worry about, run the battery of tests mentioned above, consider re-design or material change, etc.   Real-world temperature measurements would remove a lot of worries about potentially changed material properties.  I'd be astonished if this was not their first step to deal with this potential problem.




Offline FutureSpaceTourist

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Re: Refurbishment of Used Stages/Vehicles
« Reply #631 on: 03/30/2017 01:21 PM »
The new thread on the CRS-8 booster refurbishment does suggest that it was as much, if not more, upgrading to current vehicle/block specs than actual refurbishment. So that could help explain both the 4 months it took and the expected large reductions in time once SpaceX get to a more stable spec (block 5?).

Online AncientU

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Re: Refurbishment of Used Stages/Vehicles
« Reply #632 on: 03/30/2017 02:34 PM »
but are there chances that the hot re-entry might have annealed the alloy and made it lose certain properties? For the very little I know, aluminium anneals at relatively low temperatures.
I have not seen this mentioned, and it's completely obvious, but I'm sure the very first thing SpaceX did is to measure the temperature reached by the various pieces during each re-entry.  Presumably they would plaster as many temperature sensors as practical over the stage, then use models to compute the temperature of places they could not directly measure.  Plus perhaps IR imaging during flight or other methods of recording peak temperature as well.

So for the places that did not get too hot, there should be no worry about annealing.  For the places that did get hot enough to worry about, run the battery of tests mentioned above, consider re-design or material change, etc.   Real-world temperature measurements would remove a lot of worries about potentially changed material properties.  I'd be astonished if this was not their first step to deal with this potential problem.

The first step is to see a stage (pressurized) re-enter in tact.  This places an upper limit on potential loss of structural integrity.

Structural testing of a returned stage (part of the reason they chose the toastiest recovered stage) would definitively identify loss of material properties when compared to pre-flight structural tests.  If this single test shows no loss of integrity, then question answered.  EM stated, after this testing was done, that stage (tankage) could handle an indefinite number of reflights -- basis of this unqualified confidence was likely structural test results.
« Last Edit: 03/30/2017 02:36 PM by AncientU »
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Offline cppetrie

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Refurbishment of Used Stages/Vehicles
« Reply #633 on: 03/30/2017 02:37 PM »
...assuming aluminium-lithium alloys can be annealed...
It definitely can be annealed. I found a NASA research poster discussing a novel method of using annealing to make it possible to form the ends of pressure tanks out of Al-Li, something that was at the time (2014) not being done due to the difficulty of forming Al-Li into dome-type shapes.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140011717.pdf

Edit: adding date and a grammar fix
« Last Edit: 03/30/2017 02:39 PM by cppetrie »

Offline Kaputnik

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Re: Refurbishment of Used Stages/Vehicles
« Reply #634 on: 03/30/2017 07:18 PM »
Essentially the whole history of first stage reuse started with the first Grasshopper landing. Everything prior to this for the reuse or reflight of high aspect ratio TSTO VTO LV's was theoretical.

I think Armadillo Aerospace and Masten might disagree with this statement. They both demonstrated Grasshopper levels of control, albeit on a smaller scale.
Neither have put a payload into orbit and brought a booster back from hypersonic velocities nor did they use boosters capable of that.  Hence the explicit mention of doing it with a "high aspect ratio TSTO VTO LV."

We (the forum) always get into a Simpsons did it first arguments. I know people sometimes make outrageous claims about SpaceX firstyness/bestyness, but this one seemed fairly explicitly constrained.

Clearly there are further hurdles to overcome when coming in from orbit, but vertical take off and landing was done well before grasshopper, which, clearly was not an orbital booster, and was the referenced craft. Please refer back to the original quote.

Actually, I have done a disservice to the DC-X which was I believe the first to do it.

I have no problem with people 'firsting', but when the statement is clearly false, it should not be left to stand. Grasshopper was not the start of the history of first stage reuse.

I think this 'who did what first' discussion is missing the most important part of the puzzle. The first F9 reflight is different to whatever happened before with DC-X, Masten, Scaled, Armadillo, even BO, because F9 is working with far tighter mass margins. If it wasn't, it wouldn't make orbit with a commercially viable payload. A lot of stuff in aerospace gets easier if you are allowed to throw mass at the problem. What makes this reflight remarkable is that SpaceX have achieved stage recovery whilst retaining high enough performance and mass fraction to make the stage a useful orbital launch vehicle.
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Offline envy887

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Re: Refurbishment of Used Stages/Vehicles
« Reply #635 on: 03/30/2017 07:28 PM »
...assuming aluminium-lithium alloys can be annealed...
It definitely can be annealed. I found a NASA research poster discussing a novel method of using annealing to make it possible to form the ends of pressure tanks out of Al-Li, something that was at the time (2014) not being done due to the difficulty of forming Al-Li into dome-type shapes.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140011717.pdf

Edit: adding date and a grammar fix

SpaceX was spin-forming Al-Li alloy tank domes in 2013:

Quote
The fuel tanks feature a common bulkhead design for the liquid oxygen and rocket-grade kerosene. Falcon 9ís propellant tank walls and domes are both made from an aluminum-lithium alloy.

http://www.spacex.com/news/2013/09/24/production-spacex

Video of hot-spin forming a 12-ft diameter dome:
https://www.instagram.com/p/BNhYjqRgo3f/?hl=en

Offline cppetrie

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Re: Refurbishment of Used Stages/Vehicles
« Reply #636 on: 03/30/2017 07:59 PM »
...assuming aluminium-lithium alloys can be annealed...
It definitely can be annealed. I found a NASA research poster discussing a novel method of using annealing to make it possible to form the ends of pressure tanks out of Al-Li, something that was at the time (2014) not being done due to the difficulty of forming Al-Li into dome-type shapes.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140011717.pdf

Edit: adding date and a grammar fix

SpaceX was spin-forming Al-Li alloy tank domes in 2013:

Quote
The fuel tanks feature a common bulkhead design for the liquid oxygen and rocket-grade kerosene. Falcon 9ís propellant tank walls and domes are both made from an aluminum-lithium alloy.

http://www.spacex.com/news/2013/09/24/production-spacex

Video of hot-spin forming a 12-ft diameter dome:
https://www.instagram.com/p/BNhYjqRgo3f/?hl=en
The linked poster discusses spin forming and its drawbacks compared to annealing and form molding. I wasn't suggesting that tank ends couldn't be made from Al-Li but rather the linked poster suggested the annealing process used for making tank ends out of steel didn't work unmodified to make them out of Al-Li.

Offline manoweb

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Re: Refurbishment of Used Stages/Vehicles
« Reply #637 on: 03/31/2017 02:29 AM »
Today Mr. E. Musk suggested they might replace the aluminum grid find with titanium ones. Follow up metallurgical questions:

- why titanium and not inconel or tungsten, if the issue is resisting to the heat. (Yeah I know tungsten is crazy). However, and I am no titanium metallurgist, is it really good at high temperatures? I will do some research but while I am pretty sure it can easily beat aluminum, I did not know titanium was considered in high temperature applications. Now that I think about the Blackbird was made out of titanium, so my concerns here are bogus
- Mr. E. Musk apparently mentioned a forging process for such structure, and the biggest in the world for titanium. Why not machine it? (And I probably show my complete ignorance with this question)
- Titanium is much denser than Alu, and it may be that in this application, they just need large area to have enough control authority, so they won't be able to make the structure thinner - they might have to take a mass penalty for the sake of reuse. And it's totally fine, just worth noting.

Offline cppetrie

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Re: Refurbishment of Used Stages/Vehicles
« Reply #638 on: 03/31/2017 02:53 AM »
- why titanium and not inconel or tungsten, if the issue is resisting to the heat. (Yeah I know tungsten is crazy). However, and I am no titanium metallurgist, is it really good at high temperatures? I will do some research but while I am pretty sure it can easily beat aluminum, I did not know titanium was considered in high temperature applications. Now that I think about the Blackbird was made out of titanium, so my concerns here are bogus
Tungsten is super dense approaching that of lead. A piece of tungsten that large would be crazy heavy. It would definitely provide the thermal capacity though with a melting point of a few thousand degrees. I don't think the grid fins require quite that much heat tolerance, especially at that weight penalty.

Quote
- Mr. E. Musk apparently mentioned a forging process for such structure, and the biggest in the world for titanium. Why not machine it? (And I probably show my complete ignorance with this question)
Forging is likely much faster to produce and much simpler. Machining something as large as the grid fins would take a really long time and you still likely have to forge the original billet that gets machined.[/quote]
Quote
- Titanium is much denser than Alu, and it may be that in this application, they just need large area to have enough control authority, so they won't be able to make the structure thinner - they might have to take a mass penalty for the sake of reuse. And it's totally fine, just worth noting.
They may be able to alter the configuration a little to maintain the same amount of control surfaces while maintaining the same weight as those made from Al.

Offline Req

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Re: Refurbishment of Used Stages/Vehicles
« Reply #639 on: 03/31/2017 02:56 AM »
During the presser, Musk said that the new titanium alloy grid fins will be a larger design which provides enough control authority to give the stage an L/D of approximately 1, which will actually have the net effect of increasing payload to orbit by reducing the fuel needs for landing.
« Last Edit: 03/31/2017 02:57 AM by Req »

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