Author Topic: ASDS OCISLY - with Thaicom-8 S1 - Return Coverage - May-June, 2016  (Read 492242 times)

Offline Herb Schaltegger

How do reconcile point 2 with the fact that the paint on Orbcomm-2 stage is no longer "charred", even though there's no paint booth at the HIF?

I should have called it "dark coloration" rather than charring. I just edited the post accordingly. I tend to think it's more like sooting. Herb may still think it's charring. But I agree it seems to have cleaned up too well to be charring.


"Charring" is an imprecise term; in my mind I'm sort of going with "thermally-induced discoloration." Call it what you will. A change in color due to exposure to heat, deposition/impregnation/surface adhesion of contaminants, chemical reaction of the surface molecules with the constituent molecules of the entry and exhaust gas flowing by ... Perhaps someday we'll know more. In the meantime, it's clear that whatever has caused the discoloration, it has been cleaned up somewhat since recovery, but cannot be totally wiped clean (as some were asserting it would be after ORB-2).
Ad astra per aspirin ...

Offline Rocket Science

  • Senior Member
  • *****
  • Posts: 10586
  • NASA Educator Astronaut Candidate Applicant 2002
  • Liked: 4548
  • Likes Given: 13523
How do reconcile point 2 with the fact that the paint on Orbcomm-2 stage is no longer "charred", even though there's no paint booth at the HIF?

I should have called it "dark coloration" rather than charring. I just edited the post accordingly. I tend to think it's more like sooting. Herb may still think it's charring. But I agree it seems to have cleaned up too well to be charring.


"Charring" is an imprecise term; in my mind I'm sort of going with "thermally-induced discoloration." Call it what you will. A change in color due to exposure to heat, deposition/impregnation/surface adhesion of contaminants, chemical reaction of the surface molecules with the constituent molecules of the entry and exhaust gas flowing by ... Perhaps someday we'll know more. In the meantime, it's clear that whatever has caused the discoloration, it has been cleaned up somewhat since recovery, but cannot be totally wiped clean (as some were asserting it would be after ORB-2).
Question Herb... Was it that grid fin that we saw something deposited on it and flared up with a flame seen on it's trailing edge? Is it a result of the burning of that material residue deposited on the stage?
« Last Edit: 06/10/2016 02:00 am by Rocket Science »
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline Wolfram66

Only here would you ever find such a conversation.

#Corkgate2016
Somebody call Albert Belle!

Offline Kabloona

  • Senior Member
  • *****
  • Posts: 4847
  • Velocitas Eradico
  • Fortress of Solitude
  • Liked: 3432
  • Likes Given: 741
How do reconcile point 2 with the fact that the paint on Orbcomm-2 stage is no longer "charred", even though there's no paint booth at the HIF?

I should have called it "dark coloration" rather than charring. I just edited the post accordingly. I tend to think it's more like sooting. Herb may still think it's charring. But I agree it seems to have cleaned up too well to be charring.


"Charring" is an imprecise term; in my mind I'm sort of going with "thermally-induced discoloration." Call it what you will. A change in color due to exposure to heat, deposition/impregnation/surface adhesion of contaminants, chemical reaction of the surface molecules with the constituent molecules of the entry and exhaust gas flowing by ...

That works for me. The strange thing about it is the apparently highly reversible nature of the discoloration on the bottom 1/3 of the stage. It's almost black after landing, unlike the reportedly "different" white paint on the forward 2/3 of the stage, and after a cleaning it's glossy (almost) white again. So it's not charring, but maybe attracting/capturing more carbon (soot) than the "regular" paint forward of it, in a way that seems readily reversible. It's like Soot Magnet(TM) paint.
« Last Edit: 06/10/2016 02:31 am by Kabloona »

Offline douglas100

  • Senior Member
  • *****
  • Posts: 2177
  • Liked: 227
  • Likes Given: 105
My opinion has flipped twice during this discussion. Now I buy cork or something similar on the interstage and legs not on the tank. But I find it strange that they would use a different finish on the RP-1 tank versus the LOX tank. Why? I think there's still a possibility that the sharp dividing line between the two tanks is caused by the temperature difference affecting soot adherence. It'll be interesting to see the cleaned stage close up. That might cast some light on the question.
Douglas Clark

Offline Alastor

  • Full Member
  • ***
  • Posts: 380
  • Liked: 306
  • Likes Given: 573
My opinion has flipped twice during this discussion. Now I buy cork or something similar on the interstage and legs not on the tank. But I find it strange that they would use a different finish on the RP-1 tank versus the LOX tank. Why? I think there's still a possibility that the sharp dividing line between the two tanks is caused by the temperature difference affecting soot adherence. It'll be interesting to see the cleaned stage close up. That might cast some light on the question.

From a physicist standpoint, this does not seem strange at all.

The reentry engines first will cause compression in front of the rocket.
This will cause a shock wave and in turn, shock wave heating to the front of the stage.

This kind of effect appears for any other kind of leading edge. Including the grid fins.
Therefore, if TPS is needed, it is most needed at the bottom of the stage and the region above the grid fins, because of said shock heating.

It is much less needed on the LOX tank that is further back.
This is the same reason why TPS on the shuttle was most needed on the nose, the leading edges of the wings and the bottom part (since it was used as a lifting surface for aero breaking and maneuvering during reentry).

As you can see, no mystery there !

Offline douglas100

  • Senior Member
  • *****
  • Posts: 2177
  • Liked: 227
  • Likes Given: 105
I know about the compression shockwave in front of a reentering vehicle. What I still find mysterious is what the black stuff on the RP-1 tank is. Is it a discoloured special coating only on that part of the rocket, or is it soot, or both? If it's only soot then the cleaned Orbcomm rocket is easy to explain, but the sharp edge isn't so easy. If it's a special coating which has discoloured then the sharp edge is explained, but it's not so easy to explain how they cleaned it up. I look forward to an explanation of this (small) mystery with interest.
Douglas Clark

Offline Rocket Science

  • Senior Member
  • *****
  • Posts: 10586
  • NASA Educator Astronaut Candidate Applicant 2002
  • Liked: 4548
  • Likes Given: 13523
My opinion has flipped twice during this discussion. Now I buy cork or something similar on the interstage and legs not on the tank. But I find it strange that they would use a different finish on the RP-1 tank versus the LOX tank. Why? I think there's still a possibility that the sharp dividing line between the two tanks is caused by the temperature difference affecting soot adherence. It'll be interesting to see the cleaned stage close up. That might cast some light on the question.

From a physicist standpoint, this does not seem strange at all.

The reentry engines first will cause compression in front of the rocket.
This will cause a shock wave and in turn, shock wave heating to the front of the stage.

This kind of effect appears for any other kind of leading edge. Including the grid fins.
Therefore, if TPS is needed, it is most needed at the bottom of the stage and the region above the grid fins, because of said shock heating.

It is much less needed on the LOX tank that is further back.
This is the same reason why TPS on the shuttle was most needed on the nose, the leading edges of the wings and the bottom part (since it was used as a lifting surface for aero breaking and maneuvering during reentry).

As you can see, no mystery there !
I posted this from the first successful landing. I guess us Physics guys see the world the same way... ;D
Reply #2003
http://forum.nasaspaceflight.com/index.php?topic=38149.2000
« Last Edit: 06/10/2016 01:02 pm by Rocket Science »
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline Gliderflyer

I know about the compression shockwave in front of a reentering vehicle. What I still find mysterious is what the black stuff on the RP-1 tank is. Is it a discoloured special coating only on that part of the rocket, or is it soot, or both? If it's only soot then the cleaned Orbcomm rocket is easy to explain, but the sharp edge isn't so easy. If it's a special coating which has discoloured then the sharp edge is explained, but it's not so easy to explain how they cleaned it up. I look forward to an explanation of this (small) mystery with interest.

The edge is most likely caused by thermal reasons. The soot doesn't want to stick to the LOX tank, either due to it being really cold, or because it is covered with frost because it is really cold. Whatever the reason, the same phenomenon is happening on the fuel tank. If you look closely, there are black vertical stripes on the fuel tank that have a higher soot concentration. I would guess these stripes are caused by the stringers in the fuel tank giving that area more thermal mass, so that area of skin has a slightly different temperature.
I tried it at home

Offline Alastor

  • Full Member
  • ***
  • Posts: 380
  • Liked: 306
  • Likes Given: 573
I know about the compression shockwave in front of a reentering vehicle. What I still find mysterious is what the black stuff on the RP-1 tank is. Is it a discoloured special coating only on that part of the rocket, or is it soot, or both? If it's only soot then the cleaned Orbcomm rocket is easy to explain, but the sharp edge isn't so easy. If it's a special coating which has discoloured then the sharp edge is explained, but it's not so easy to explain how they cleaned it up. I look forward to an explanation of this (small) mystery with interest.

The edge is most likely caused by thermal reasons. The soot doesn't want to stick to the LOX tank, either due to it being really cold, or because it is covered with frost because it is really cold. Whatever the reason, the same phenomenon is happening on the fuel tank. If you look closely, there are black vertical stripes on the fuel tank that have a higher soot concentration. I would guess these stripes are caused by the stringers in the fuel tank giving that area more thermal mass, so that area of skin has a slightly different temperature.

I agree that there might be thermal reasons behind the sharp edge, but you also have to ask yourself where the soot comes from. It doesn't appear out of nowhere and the shockwave is a plasma and thus does not directly generate soot. So if there is soot, where does it come from ?

Surely the TPS around the bells does generate some.
Also the combustion products from the engines probably contain soot (although they probably try to generate as little as possible for efficiency reasons)

But more importantly if there is any kind of ablative TPS around the bottom of the stage (and I think the consensus is getting towards a yes on that question), it is not just there to stay intact (otherwise you wouldn't use it), but to absorb heating damage.
In that case, a second origin of this clear demarcation line must be that the TPS side is at least a little ablated.
In my opinion, that means you can't just scrub it clean. You at least have to repaint part of the stage and/or replace part of the TPS.
Of course you won't repaint all of it. Just the part that needs it, but if it is indeed TPS and it is not deemed useless, then they must have had some repainting to do !

Offline cscott

  • Senior Member
  • *****
  • Posts: 3471
  • Liked: 2867
  • Likes Given: 726

I agree that there might be thermal reasons behind the sharp edge, but you also have to ask yourself where the soot comes from. It doesn't appear out of nowhere and the shockwave is a plasma and thus does not directly generate soot. So if there is soot, where does it come from ?
[...]

But more importantly if there is any kind of ablative TPS around the bottom of the stage (and I think the consensus is getting towards a yes on that question), it is not just there to stay intact (otherwise you wouldn't use it), but to absorb heating damage.
In that case, a second origin of this clear demarcation line must be that the TPS side is at least a little ablated.
In my opinion, that means you can't just scrub it clean. You at least have to repaint part of the stage and/or replace part of the TPS.
Of course you won't repaint all of it. Just the part that needs it, but if it is indeed TPS and it is not deemed useless, then they must have had some repainting to do !
We know they didn't repaint or re-cork (then repaint) the stage, they don't have the proper equipment to do that.  That seems to invalidate the rest of your theory.

If you want to claim ablation, you need to explain what exactly SpaceX's paint spray booth in Hawthorne is used for, and why it's not needed at the Cape.

I'll help you out: "the spray booth at Hawthorne is only needed for priming the aluminum. Once the surface is primed, an ordinary hand sprayer is used to apply the white TPS overcoat".  Or, "the cork is applied prepainted and the spray booth is only used for the top half of the core".

Now: I don't think either of those is true, or have any evidence that's they are the case.   But if you believe in the replace/repaint hypothesis, you need to work on convincing us that something like the above is true.

Otherwise we're willfully ignoring evidence and going in circles.
« Last Edit: 06/10/2016 09:22 pm by cscott »

Offline Rocket Science

  • Senior Member
  • *****
  • Posts: 10586
  • NASA Educator Astronaut Candidate Applicant 2002
  • Liked: 4548
  • Likes Given: 13523
Multiple engine starts and cutoffs with the RP-1 exhaust, confined within the bow shock interactions, would add to the "soot" (called "lamp black" in the old days) we see...
« Last Edit: 06/10/2016 05:51 pm by Rocket Science »
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline llanitedave

  • Senior Member
  • *****
  • Posts: 2286
  • Nevada Desert
  • Liked: 1545
  • Likes Given: 2055
Aren't the gas generators sootier than the engines?
"I've just abducted an alien -- now what?"

Offline Rocket Science

  • Senior Member
  • *****
  • Posts: 10586
  • NASA Educator Astronaut Candidate Applicant 2002
  • Liked: 4548
  • Likes Given: 13523
Aren't the gas generators sootier than the engines?
I am considering it "all together" into the plume... I consider them pretty sooty... sshh.. you'll alert the EPA... ;D
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline intrepidpursuit

  • Full Member
  • ****
  • Posts: 721
  • Orlando, FL
  • Liked: 561
  • Likes Given: 400
We've seen in the videos that much of the stage is engulfed in flame and smoke during the reentry and landing burns. I don't see why it is so hard to believe that it is soot. I thought I'd read that they originally used cork for insulation but found that ice buildup alone worked as well, so they got rid of the insulation.

The clear line is because of the ice that had formed on the oxygen section of the tank. Attached is a picture of the very clear ice line on an Atlas V. It isn't white so it is easier to see. Of course there is foam insulation on that tank, but it shows how defined the ice formation is. I realize it is subjected to heat on return, but that is a lot of ice and all this happens fast. It first sees heat at the reentry burn, and that is where to soot deposits seem to happen. This has been discussed at length in other threads.

It doesn't follow that there would be cork on the interstage, even if it is on the tanks. Cork is an insulator, not a TPS. There is nothing that needs insulating in the interstage. I think the brown color is just a primer layer. The interstage is aluminum honeycomb and carbon fiber, so it doesn't appear we are seeing the structure itself.

EDIT: There is obviously a coating at the bottom under the legs. Again, this seems more likely to be SPAM or some other heat protection rather than an insulator. The octaweb gets roasted on the way up before it ever comes back down due to recirculation. It seems like the octaweb and the grid fins should be the only parts that take significant reentry heating, but I'm no aerodynamics expert.
« Last Edit: 06/10/2016 09:10 pm by intrepidpursuit »

Offline Rocket Science

  • Senior Member
  • *****
  • Posts: 10586
  • NASA Educator Astronaut Candidate Applicant 2002
  • Liked: 4548
  • Likes Given: 13523
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline Kabloona

  • Senior Member
  • *****
  • Posts: 4847
  • Velocitas Eradico
  • Fortress of Solitude
  • Liked: 3432
  • Likes Given: 741
Quote
EDIT: There is obviously a coating at the bottom under the legs. Again, this seems more likely to be SPAM or some other heat protection rather than an insulator. The octaweb gets roasted on the way up before it ever comes back down due to recirculation. It seems like the octaweb and the grid fins should be the only parts that take significant reentry heating, but I'm no aerodynamics expert.

The base of the stage gets roasted both going up and coming down, and possibly worse coming down during entry retroburn and Mach 5 aero heating. As a retired (solid) propulsion/systems engineer who has worked on rockets with cork TPS, there's no question in my mind from the photos we've seen that it's cork just aft of the legs. We've seen numerous photos of that area after landing with some areas of cork torn off and the brown edges/surfaces of the cork exposed. The material looks entirely different from SPAM and there's no doubt in my mind that it's cork.

Here's picture showing the corked area aft of the legs on JCSAT-14, with a patch of cork missing showing the metal beneath. We've seen other similar pictures, but this one nicely shows the brown surface color of cork. (Another visual artifact if cork panels is the joint lines between the panels, which can be seen clearly in other photos.)

Photo credit: jardeon.  https://m.imgur.com/gallery/2BWF8#
« Last Edit: 06/10/2016 10:15 pm by Kabloona »

Offline Kabloona

  • Senior Member
  • *****
  • Posts: 4847
  • Velocitas Eradico
  • Fortress of Solitude
  • Liked: 3432
  • Likes Given: 741
Quote
It doesn't follow that there would be cork on the interstage, even if it is on the tanks. Cork is an insulator, not a TPS.

TPS, or thermal protection system, is a catch-all term for anything that protects the rocket from heating or cooling. Cork, multi-layer insulation, (MLI), ablative coatings, etc, are routinely called by the shorthand "TPS."

Quote
There is nothing that needs insulating in the interstage. I think the brown color is just a primer layer. The interstage is aluminum honeycomb and carbon fiber, so it doesn't appear we are seeing the structure itself.

I wouldn't have expected cork on the interstage either, but everything I've seen is consistent with cork on the interstage. The substrate roughness beneath the paint, the brown mottled color (not solid brown like a uniform color paint) of exposed surface beneath the paint, the joint lines between the substrate panels (and SPAM is not applied in uniformly-shaped rectangular panels).

The grid fins produce shock waves, and the cork insulation may be in part intended to protect against heating from shock wave impingement on the interstage. The brown patches show that there's clearly some serious impingement happening above the grid fins.
« Last Edit: 06/11/2016 01:32 am by Kabloona »

Online matthewkantar

  • Senior Member
  • *****
  • Posts: 2119
  • Liked: 2565
  • Likes Given: 2253
Composites are generally heat intolerant as far as I know, so TPS on the interstage.

Matthew

Offline Rocket Science

  • Senior Member
  • *****
  • Posts: 10586
  • NASA Educator Astronaut Candidate Applicant 2002
  • Liked: 4548
  • Likes Given: 13523
Composites are generally heat intolerant as far as I know, so TPS on the interstage.

Matthew
Yeah, they tend to become de-composites... ;D
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Tags:
 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
1