NASA's Orion crew capsule had heat shield issues during Artemis 1 − an aerospace expert weighs in (op-ed)

[Admin]

Issues with the Orion spacecraft's heat shield on Artemis 1 have delayed the next mission, Artemis 2. So what happened?

NASA's Orion crew capsule had heat shield issues during Artemis 1 − an aerospace expert weighs in (op-ed) : Read more

 

[Unclear Engineer]

So, NASA is going to do an untested re-entry profile with humans aboard for Artemis II and then use an untested new manufacturing technique for the heat shield on the crewed Artemis III mission?! By untested, I mean not flight tested.

That concerns me. Just like there were unexpected effects on the heat shield in Artemis I, there could be other unexpected effects for different reentry profiles and for new manufacturing techniques.

Considering the extreme costs of one or even two more SLS launches, I understand why NASA wants to take the risk instead of canceling the program.

But, I am wondering if there is a way to use StarShip or even Falcon Heavy to do an uncrewed flight test. It does not have to go to the Moon, it just needs to be brought into the atmosphere at the desired speed and angle. So, a lot of the delta-V would go into accelerating the capsule downward.

 

[George²]

But, I am wondering if there is a way to use StarShip or even Falcon Heavy to do an uncrewed flight test.

Only for this type of flight test even ordinary Falcon 9 have enough power to send Orion. Because the ship doesn't need to be fully loaded with fuel and payload, as in an actual flight to the Moon.

 

[Unclear Engineer]

George, It is not just a matter of launching the Orion capsule into orbit. The test would need to accelerate the Orion capsule to much higher velocity and change its orbital parameters so that it looks like it is coming back from the Moon at about 25,000 mph, and on what would be a highly elliptical orbit (if the Earth was just a point of mass).

I know that SpaceX was at one time planning to send one of its Dragon capsules around the Moon, But, that is a different mass. So, I am not sure it could be done with the Orion capsule with Falcon. But, I'm not sure it couldn't be done, either.

That is why I am asking the question.

 

[George²]

George, It is not just a matter of launching the Orion capsule into orbit. The test would need to accelerate the Orion capsule to much higher velocity and change its orbital parameters so that it looks like it is coming back from the Moon at about 25,000 mph, and on what would be a highly elliptical orbit (if the Earth was just a point of mass).

I know that SpaceX was at one time planning to send one of its Dragon capsules around the Moon, But, that is a different mass. So, I am not sure it could be done with the Orion capsule with Falcon. But, I'm not sure it couldn't be done, either.

That is why I am asking the question.

I think that is possible with all stages of Falcon 9 block 5 are used in expendable regime and let me remind you that Orion does not need to be loaded with maximum payload.

 

[Unclear Engineer]

For a heat shield test, yes, Orion does need to be loaded to its maximum mass limit.

The amount of energy that needs to be removed during atmospheric reentry is directly proportional to the mass of the reentering spacecraft. So, the temperatures and heating rates that the shield must endure are strongly influenced by the total mass of the craft.

 

[George²]

For a heat shield test, yes, Orion does need to be loaded to its maximum mass limit.

The amount of energy that needs to be removed during atmospheric reentry is directly proportional to the mass of the reentering spacecraft. So, the temperatures and heating rates that the shield must endure are strongly influenced by the total mass of the craft.

This is not realistic. Orion does indeed return at high speed, but significantly lightened in fuel and cargo. Furthermore, only the crew capsule lands.

 

[Unclear Engineer]

Maybe we are talking past each other. For a proper test of the heat shield, the capsule needs to be at its maximum mass for reentry from any planned mission.

But, for purposes of getting a Falcon 9 to be able to drive it into the atmosphere at a speed and angle that simulates a return from lunar missions, none of the parts that are not attached to the capsule during reentry from the Moon need to be launched and then accelerated towards the Earth for that test.

Yes, there may be some propellant of other expendables that would not be completely filling the tanks of the Orion capsule when it returns. But, most of that gets jettisoned with the service module and is not part of the reentry configuration.

A quick Googling indicates that the launch mass of the capsule is 10,400 kg, and the landing weight of the capsule is 9,300 kg + 100 kg of "payload", which I assume is going to be lunar rocks. Presumably, both the launch weight and reentry weight includes the astronauts and all of the gear they are wearing.

So, an upper stage of a launch vehicle for such a test would need to be able to accelerate about 9.400 kg, plus itself, to about 25,000 mph (45,000 kph) back toward the Earth from some peak altitude. It would not necessarily need to go into an orbit - it could be a mostly ballistic trajectory, with some sideways velocity added to achieve the correct angle for reentry.

 

[Classical Motion]

From what I read, a shield of man made diamond dust should protect any mass at velocity to enter safely. But one knows not what to believe.

 

[Unclear Engineer]

Googllng a bit more, the Falcon 9 is rated for only 4,020 kg to Mars, which should be a roughly equivalent delta-V to an Orion reentry test mission.

The Falcon Heavy is rated for 16,800 kg payload to Mars. So, I would think that a Falcon Heavy could be used to test the Orion heat shield for a lunar return reentry - provided the staging works out for getting the second stage to the right altitude and then restarting and accelerating itself and the capsule back toward Earth at a final velocity of 25,000 mph (40,000 kph).

But, somebody would need to look at what stages need to fire for what periods of time to make that happen, to see if the current equipment could be easily configured to do that mission.

If the ESM had to be included to get the right flight parameters, that would be a problem, because that weighs 15,461 kg, and that plus a 9, 400 kg capsule would total 24,851 kg, which is more than the Falcon Heavy could seem to be able to handle for that mission.

Still, if the Falcon Heavy cansend 16,800 kg to Mars, I would think it could send the Orion capsule around the Moon, if necessary to get the proper reentry. The only hangup I see is whether the accuracy of the reentry parameters could be achieved without the service module attached to the capsule during the return. Maybe some sort of mission specific trans stage would be needed. And that could be expensive and time consuming to develop.

 

[George²]

The Falcon 9 Mars payload delivery estimate is likely to include a reusable first stage not in fully expendable regime. It also likely includes a deceleration for orbit entry and possible engine-assisted landing. This requires more fuel and oxidizer to be retained for these operations. So the vehicle will have a higher mass than payload during the intermediate stages of the flight to Mars.

 

[Unclear Engineer]

George2, I think all of those things are part of the "payload" so far as Mars trajectory insertion numbers are considered.

I think it would require Falcon Heavy.

 

[Gords]

I enjoy reading all these engineering debates and potential solutions, but nobody is really picking up on the heat shield design itself, which is quoted as being technology from the Apollo era. A spin off from the original heat shield technology has been oil + gas passive fire protection using epoxy intumescent to protect structural steel, pressure vessels, living quarters and more (an industry which I am in).

The industry has moved on greatly since the days of Apollo. Looking at the mode of failure, which seems to be caused due to rapid heating/melt of the applied system, followed by hardening on cooling, leading to a rigid outer layer of char, which on reheat cracks - this is typical of older intumescent technology, which used high concentrations of boric acid.

Boric acid is used in glass making and does strengthen the intumescent char (by making it 'glass like'), but also like glass, it can be brittle and prone to cracking. Resin + general formulation technology has moved on since the 1960's + 70's. Some of the newer technology is far more flexible and robust, so I cant help thinking there could be solutions available which might negate the reentry concerns.

I am not sure if it would or wouldn't work, but there are well established industry tests which could help screen the newer technology, prior to any real life trials. I can understand that moving away from existing technology can be deemed as risky, but there may be more viable heat shield solutions out there.