Orion Discussion Thread 2

[DanClemmensen]

https://arstechnica.com/space/2024/10/for-some-reason-nasa-is-treating-orions-heat-shield-problems-as-a-secret/

For some reason, NASA is treating Orion’s heat shield problems as a secret

from the article"

Another report released by the Government Accountability Office (GAO) in June said a preliminary analysis of the heat shield problem suggested to engineers that "the permeability of the material was lower than their models had indicated."

My knowledge of heat shields is utterly superficial and comes from Wikipedia, so feel free to ridicule this idea:
    As an ablative heat shield heats up, it begins charring and the charred surface is supposed to (more or less) sublimate, carrying some heat away. But heat begins to penetrate into the body of the heat shield, and some of this internal heat converts some of the interior into gas, which carries some of the heat back to and beyond the heat shield surface. I do not know the nature of the stuff that is supposed to gassify in Avcoat.

My utterly wild and unsupported guess: The permeability of the material was too low and some of the gas was trapped. It expanded and blew chunks out of the shield.

[Eric Hedman]

https://arstechnica.com/space/2024/10/for-some-reason-nasa-is-treating-orions-heat-shield-problems-as-a-secret/

For some reason, NASA is treating Orion’s heat shield problems as a secret

from the article"

Another report released by the Government Accountability Office (GAO) in June said a preliminary analysis of the heat shield problem suggested to engineers that "the permeability of the material was lower than their models had indicated."

My knowledge of heat shields is utterly superficial and comes from Wikipedia, so feel free to ridicule this idea:
    As an ablative heat shield heats up, it begins charring and the charred surface is supposed to (more or less) sublimate, carrying some heat away. But heat begins to penetrate into the body of the heat shield, and some of this internal heat converts some of the interior into gas, which carries some of the heat back to and beyond the heat shield surface. I do not know the nature of the stuff that is supposed to gassify in Avcoat.

My utterly wild and unsupported guess: The permeability of the material was too low and some of the gas was trapped. It expanded and blew chunks out of the shield.

Sounds possible.  Hopefully, they will tell us in great detail what happened and more importantly, can they fix this.

[eeergo]

My knowledge of heat shields is utterly superficial and comes from Wikipedia, so feel free to ridicule this idea:
    As an ablative heat shield heats up, it begins charring and the charred surface is supposed to (more or less) sublimate, carrying some heat away. But heat begins to penetrate into the body of the heat shield, and some of this internal heat converts some of the interior into gas, which carries some of the heat back to and beyond the heat shield surface. I do not know the nature of the stuff that is supposed to gassify in Avcoat.

My utterly wild and unsupported guess: The permeability of the material was too low and some of the gas was trapped. It expanded and blew chunks out of the shield.

Lower permeability than expected can mean two things: what you described (low GAS permeability), causing combustion/charring gas products to be trapped inside the heat shield material, expanding and blowing the overlying (and weaker) material out.

Or it can mean low HEAT permeability, which would actually be the opposite effect: heat wouldn't be transported adequately inside the bulk, which would presumably overheat the surface material once it exhausts its share of volatile contents. If this was the case, the excessive erosion observed in Artemis I would be caused by greater fragility of the overcharred material.

No idea which of the two is more severe/benign though, although I'm guessing better-than-expected protection furnished by the TPS (having lower heat permeability), which presumably can be "worsened" in order to ameliorate the mechanical fragility situation, is a better world to live in than one with an unexpectedly popcorning TPS.

[John Santos]

My knowledge of heat shields is utterly superficial and comes from Wikipedia, so feel free to ridicule this idea:
    As an ablative heat shield heats up, it begins charring and the charred surface is supposed to (more or less) sublimate, carrying some heat away. But heat begins to penetrate into the body of the heat shield, and some of this internal heat converts some of the interior into gas, which carries some of the heat back to and beyond the heat shield surface. I do not know the nature of the stuff that is supposed to gassify in Avcoat.

My utterly wild and unsupported guess: The permeability of the material was too low and some of the gas was trapped. It expanded and blew chunks out of the shield.

Lower permeability than expected can mean two things: what you described (low GAS permeability), causing combustion/charring gas products to be trapped inside the heat shield material, expanding and blowing the overlying (and weaker) material out.

Or it can mean low HEAT permeability, which would actually be the opposite effect: heat wouldn't be transported adequately inside the bulk, which would presumably overheat the surface material once it exhausts its share of volatile contents. If this was the case, the excessive erosion observed in Artemis I would be caused by greater fragility of the overcharred material.

No idea which of the two is more severe/benign though, although I'm guessing better-than-expected protection furnished by the TPS (having lower heat permeability), which presumably can be "worsened" in order to ameliorate the mechanical fragility situation, is a better world to live in than one with an unexpectedly popcorning TPS.

I know nothing about this (but please DON'T ridicule, just explain!) a third possibility that occurs to me is the "lower permeability" is permeability to water.  Artemis 1 spent a lot of time outdoors in extremely humid Florida, often getting rained on.  Over the many months, water slowly got absorbed into the Avcoat.  With the expected permeability, it would have quickly dried out in the vacuum of space, but instead it retained the water over the month it spent out there, the water heated up and boiled during reentry, and the steam popped off chunks of the heat shield.  If it had quickly dried out as expected, or had never absorbed so much water in the first place, this would not have happened.  If this is the case, the cure would be to not let it sit outside for so long, or to put a rain shield over the capsule if it has to sit on the pad for extended time, or to bring it indoors and dry it out if it gets too wet.  They would need to measure the water content of the heat shield before launch, which would be a whole new set of GSE monitoring equipment and flight rules.

This is pure speculation on my part, though.

[eeergo]

I know nothing about this (but please DON'T ridicule, just explain!) a third possibility that occurs to me is the "lower permeability" is permeability to water.  Artemis 1 spent a lot of time outdoors in extremely humid Florida, often getting rained on.  Over the many months, water slowly got absorbed into the Avcoat.  With the expected permeability, it would have quickly dried out in the vacuum of space, but instead it retained the water over the month it spent out there, the water heated up and boiled during reentry, and the steam popped off chunks of the heat shield.  If it had quickly dried out as expected, or had never absorbed so much water in the first place, this would not have happened.  If this is the case, the cure would be to not let it sit outside for so long, or to put a rain shield over the capsule if it has to sit on the pad for extended time, or to bring it indoors and dry it out if it gets too wet.  They would need to measure the water content of the heat shield before launch, which would be a whole new set of GSE monitoring equipment and flight rules.

This is pure speculation on my part, though.

They would have specified it if by "permeability" they meant water, or any specific exposure to a substance, for that matter - the problem then wouldn't be a purported low permeability, but rather permeability to water in the first place: the shield should be mostly impermeable to water (and indeed most substances it shall come into contact with), it was further waterproofed by the application of the outer reflective tape layer (see first image below), and the LAS ogive actually doesn't leave any part of the heat shield exposed (see other two images). Inside that fairing, air is conditioned to a specified humidity content - in any case, it wasn't "rained on".

[montyrmanley]

Sounds possible.  Hopefully, they will tell us in great detail what happened and more importantly, can they fix this.

I think that if the fix were straightforward, NASA would have said so already. The fact that the problem has taken this long to diagnose, and the silence surrounding the root cause, tells me that the solution will be both expensive and time-consuming and nobody wants to be the bearer of bad news -- particularly in the waning days of a fraught presidential election season.

I think there's very little chance that NASA will roll the dice on Artemis II with the current heatshield design, so I we're likely looking at a delay of between 12 and 18 months while the heatshield is redesigned. They may even want to do another test flight before putting humans aboard, which would push it out further still.

[sdsds]

NASA deserves respect for how skillfully they are obfuscating the status of Orion, and thus the Artemis II mission schedule and content. And by keeping quiet/dark on the status of several other programs they have made this the norm.

Personally I'm still hoping for the best, which would be a heat shield issue addressed by a simple change in the atmospheric entry profile and Artemis II flying on schedule. If there's evidence that can't happen I'm grateful NASA is keeping me blissfully unaware of it, preserving my naive innocence as long as possible.

[DanClemmensen]

Sounds possible.  Hopefully, they will tell us in great detail what happened and more importantly, can they fix this.

I think that if the fix were straightforward, NASA would have said so already. The fact that the problem has taken this long to diagnose, and the silence surrounding the root cause, tells me that the solution will be both expensive and time-consuming and nobody wants to be the bearer of bad news -- particularly in the waning days of a fraught presidential election season.

I think there's very little chance that NASA will roll the dice on Artemis II with the current heatshield design, so I we're likely looking at a delay of between 12 and 18 months while the heatshield is redesigned. They may even want to do another test flight before putting humans aboard, which would push it out further still.

Even if the redesign or other physical mitigation plan has already been completed, it will still take a long time (12 months?) to implement. The heat shield is fairly deep inside the spacecraft, so taking it apart and putting it back together is time-consuming. If they already have a new heat shield that can be used to replace the old one the time would be less. If they need to remove the old and modify it before re-installing, the time would be more.

[StraumliBlight]

Episode 362: Suited for the Moon, with Dustin Gohmert and Dan Green discussing the Orion Crew Survival System Suit (interviewed previously on Episode 18). [Nov 15]

[sdsds]

Even if the redesign or other physical mitigation plan has already been completed, it will still take a long time (12 months?) to implement.

This is true if the mitigation plan involves a change to the heat shield. If instead the mitigation is an operational change (like direct rather than skip re-entry) they can fly the heat shield 'as is' and there might be no additional delay. Is there any public evidence supporting one or the other of these scenarios?

[DanClemmensen]

Even if the redesign or other physical mitigation plan has already been completed, it will still take a long time (12 months?) to implement.

This is true if the mitigation plan involves a change to the heat shield. If instead the mitigation is an operational change (like direct rather than skip re-entry) they can fly the heat shield 'as is' and there might be no additional delay. Is there any public evidence supporting one or the other of these scenarios?

Agreed. That's why I specified physical mitigation. Sorry, I should have been more explicit.

[montyrmanley]

If NASA is indeed going ahead with the current heat-shield design on Orion and will alter the re-entry profile instead to reduce spalling, it's amazing to me that it took two years for NASA to come to this conclusion. I think this is probably a "make lemonade out of lemons" situation: the heat shield is indeed flawed, but NASA is worried that another two-year delay means that the whole Artemis program is likely to be canceled. The Trump administration will probably support Artemis to the extent that it produces American successes in the new space race (that is, American astronauts on the moon). From a political perspective, support is contingent upon this happening before the end of Trump's term -- the only political value Artemis has is in terms of optics and "vision". Just like Apollo before it, it's an expression of American technical and political might. Constant cost overruns, delays, and design problems signal weakness and not strength.

So I think NASA and the related SLS/Orion contractors are now on notice: deliver or get canceled. The threat at present is implicit, but the new NASA Administrator -- whomever that will be -- will probably make it explicit. In any event, NASA has heard and understood.

I do find it mordantly hilarious that it takes NASA *four months* to stack the SLS when SpaceX can stack and unstack Starship in a few hours.

[StraumliBlight]

Episode 363: Orion Parachutes [Nov 22]

Host: We’ve had a few missions to test these now, but I want to go back to Artemis I. What did your teams learn from the parachute performance on Artemis I?

Jared Daum: Yeah. We learned a lot. And also unfortunately, we may have missed out on some information. So one thing that’s super important for parachutes is learning from each mission. So this is a very good question. One of the best ways to do that is to recover the parachutes and inspect them to see what kind of damage there is. The parachutes will always tell some sort of story. So we spent a lot of time out at Yuma drop testing our parachutes. After every drop test, a thorough inspection of every square inch of that parachute marking down every nick, every burn, every little pulled fiber to try to understand what could possibly go wrong with these chutes.

Unfortunately, for Artemis I, we weren’t able to recover any of the parachutes. They sank before the recovery team was able to get to them. So it’s kind of a missed opportunity there. But two of the things that we can use from Artemis I that are super valuable is, A. Imagery, and B. Data and data analysis. So on the data analysis side, we can use data from the vehicle, the IMU to reconstruct a trajectory and then try to infer what the parachutes did. And now we have load cells for each parachute. We have knowledge of what we expect the parachutes to do. So we can use all this to reconstruct the performance, try to understand how they behaved, and try to kind of play that forward into the future to see what we expect for future missions. The other really important thing is imagery. So all kinds of imagery to assess the parachute performance. So onboard imagery, that’s cameras on the spacecraft itself. We had some in the cabin looking out the windows to see like what an astronaut would see. We had some in the forward bay, kind of on top of the vehicle looking right up at the parachutes. Beautiful, beautiful imagery of the chutes being deployed and performing. And we can learn a lot from that. We can see entanglements; we can pull out timing from that to determine when the reefing line cutter’s fired. We can look at kind of the relative timing and area, if you will, of each parachute to kind of interpret how they’re sharing the load. So in addition to the onboard imagery, WB-57 and other air assets flying around with great camera equipment to get air to air imagery and also ground air or seed air in the case of Artemis video or cameras on the ships looking up and, and viewing the descent and splashdown. So we spent a lot of time looking through that video picking apart frame by frame to pull anything we can from it.

[DanClemmensen]

If NASA is indeed going ahead with the current heat-shield design on Orion and will alter the re-entry profile instead to reduce spalling, it's amazing to me that it took two years for NASA to come to this conclusion.

My speculation: They probably considered this option fairly early on, and found that it has some substantial down-sides, so they shelved it while they investigated other options. When all of the other options ended up being worse (probably due to schedule) they went back to the re-entry profile option.

So, what problems might be associated with a altered re-entry profile? Surely the original profile was optimized for some parameters, so an altered profile will be sub-optimal for one or more of those parameters. What might they be?

[montyrmanley]

If NASA is indeed going ahead with the current heat-shield design on Orion and will alter the re-entry profile instead to reduce spalling, it's amazing to me that it took two years for NASA to come to this conclusion.

My speculation: They probably considered this option fairly early on, and found that it has some substantial down-sides, so they shelved it while they investigated other options. When all of the other options ended up being worse (probably due to schedule) they went back to the re-entry profile option.

So, what problems might be associated with a altered re-entry profile? Surely the original profile was optimized for some parameters, so an altered profile will be sub-optimal for one or more of those parameters. What might they be?

It could be that NASA doesn't want to make the profile any shallower due to fear of Orion simply skipping out of the envelope like a rock skipping on a pond -- but it needs to be fairly shallow to avoid the extreme heating of a steeper re-entry angle.

NASA might be able to tinker around a bit with entering the envelope a bit sooner and accepting a bigger landing ellipse (thus running a risk of having recovery vessels out of position when the capsule splashes down). Or they might try to bleed off some velocity by doing an aerobraking orbit prior to actual re-entry (I don't know if Orion would have sufficient delta-v to do this on a lunar return trajectory, however -- I'd need to go look up the specs on the service module and its propulsion margin on return).

Lots of "maybes" and "mights" here -- I'm probably wrong.

[sdsds]

[...] Or they might try to bleed off some velocity by doing an aerobraking orbit prior to actual re-entry

In theory maybe, but the latest YouTube update video from psloss makes it pretty clear this isn't an alternative being considered.

That video also touches on the connection between the landing profiles/trajectories and the launch opportunities. Can Orion do outbound trajectory correction maneuvers to change the elapsed duration from launch to landing? Even changing it 2 or 3 hours would result in the Earth's axis rotation moving the landing to a different place on the surface.

[sdsds]

[...] Or they might try to bleed off some velocity by doing an aerobraking orbit prior to actual re-entry

In theory maybe, but the latest YouTube update video from psloss makes it pretty clear this isn't an alternative being considered.

That video also touches on the connection between the landing profiles/trajectories and the launch opportunities. [...]

I'm grateful this question was asked and answered today. The new limits on the re-entry trajectory cut in half the number of days in each launch opportunity. NASA plans to accept that restriction for Artemis II. For Artemis III and following they will fix the root cause with new heat shield construction techniques. Or at least that's what I understood Amit Kshatriya to have said.

[Coastal Ron]

Moved from the "What Will A Second Trump Term Mean for Space Policy?" thread. The topic was whether a so-called "commercial" Orion was ever a possibility.

No one that understood all the extenuating factors thought that was viable. And it never got any traction. It was just PR to distract from the high cost of the program.

That is not the reason. The reason is that Boeing doesn't want a fixed price contract, so they have refused to renegotiate their SLS contract with NASA. LM on the other hand agreed to a fixed price contract after Artemis VIII. See this link for more on this:

https://www.nasa.gov/news-release/nasa-commits-to-long-term-artemis-missions-with-orion-production-contract/

Quoting NASA to show that NASA wanted to do something is NOT proof of anything. It is a self-licking ice cream cone - which ironically the phrase was created to describe NASA's relationship between the Shuttle and the ISS.

The SLS and the Orion programs are the U.S. Government using contractors to build U.S. Government assets. Boeing doesn't own the SLS design, and Lockheed Martin doesn't own the Orion MPCV design. They both may assert some IP with HOW they build the respective vehicles, but the SLS and Orion are taxpayer owned assets. Just so we are clear on that.

The idea that NASA floated was that the respective companies could "buy" the right to market their respective vehicles for non-government customers. Which as never tested in Congress, and never tested from a legal basis, since neither Boeing nor Lockheed Martin ever took the effort seriously.

And why would they? They wouldn't, for a simple reason. THERE ARE NO "COMMERCIAL" CUSTOMERS THAT WOULD WANT THE SLS OR ORION!

As it is Boeing and Lockheed Martin have little risk being the prime contractors, but they get a LOT of revenue from the programs, and likely pretty good profit. Why would they risk that? They wouldn't.

Which is why the concept that NASA floated for making the Orion and SLS "commercial" was just political misdirection, intended to keep the focus off of the tremendous cost of both programs (i.e. +$25B for each at this point, with no operational flights).

[yg1968]

Moved from the "What Will A Second Trump Term Mean for Space Policy?" thread. The topic was whether a so-called "commercial" Orion was ever a possibility.

No one that understood all the extenuating factors thought that was viable. And it never got any traction. It was just PR to distract from the high cost of the program.

That is not the reason. The reason is that Boeing doesn't want a fixed price contract, so they have refused to renegotiate their SLS contract with NASA. LM on the other hand agreed to a fixed price contract after Artemis VIII. See this link for more on this:

https://www.nasa.gov/news-release/nasa-commits-to-long-term-artemis-missions-with-orion-production-contract/

Quoting NASA to show that NASA wanted to do something is NOT proof of anything. It is a self-licking ice cream cone - which ironically the phrase was created to describe NASA's relationship between the Shuttle and the ISS.

The SLS and the Orion programs are the U.S. Government using contractors to build U.S. Government assets. Boeing doesn't own the SLS design, and Lockheed Martin doesn't own the Orion MPCV design. They both may assert some IP with HOW they build the respective vehicles, but the SLS and Orion are taxpayer owned assets. Just so we are clear on that.

The idea that NASA floated was that the respective companies could "buy" the right to market their respective vehicles for non-government customers. Which as never tested in Congress, and never tested from a legal basis, since neither Boeing nor Lockheed Martin ever took the effort seriously.

And why would they? They wouldn't, for a simple reason. THERE ARE NO "COMMERCIAL" CUSTOMERS THAT WOULD WANT THE SLS OR ORION!

As it is Boeing and Lockheed Martin have little risk being the prime contractors, but they get a LOT of revenue from the programs, and likely pretty good profit. Why would they risk that? They wouldn't.

Which is why the concept that NASA floated for making the Orion and SLS "commercial" was just political misdirection, intended to keep the focus off of the tremendous cost of both programs (i.e. +$25B for each at this point, with no operational flights).

I never said that Orion would have non-NASA customers. I agree with you that they won't at such high prices. I am just saying that the intent for these revised SLS and Orion contracts was to eventually make them fixed priced. For Orion that is already going to happen after Artemis VIII. For SLS, it never happened because Boeing refused to change their contract. The prior Boeing CEO said that it would no longer enter into any fixed-price contracts. I don't know if the new CEO has a different opinion but it probably doesn't matter at this point.

Eric Berger's sources seem to think that Orion might fly on New Glenn. It's not clear to me how this would work, presumably Orion would be provided by NASA as GFE (Government Furnished Equipment). That is likely a more realistic scenario than LM winning a truly commercial contract. This entire thing is political, so predicting what makes the most sense is futile.

So how would NASA astronauts get to the Moon without the SLS rocket? Nothing is final, and the trade space is open. One possible scenario being discussed for future Artemis missions is to launch the Orion spacecraft on a New Glenn rocket into low-Earth orbit. There, it could dock with a Centaur upper stage that would launch on a Vulcan rocket. This Centaur stage would then boost Orion toward lunar orbit.

https://arstechnica.com/space/2024/12/how-did-the-ceo-of-an-online-payments-firm-become-the-nominee-to-lead-nasa/

[montyrmanley]

Eric Berger's sources seem to think that Orion might fly on New Glenn. It's not clear to me how this would work, presumably Orion would be provided by NASA as GFE (Government Furnished Equipment).

In principle and from an organizational standpoint, it seems like it would be no different than flying an NSA satellite to orbit on a commercial vehicle. The government pays vendors to fly government-owned and -built stuff into space all the time. The DoD already flies their X-37 on commercial Atlas V boosters (soon on Vulcan AFAIK).

As a technical matter, mating Orion to New Glenn shouldn't be too hard, though creating a mating adapter would take time.