NASA's Orion spacecraft is about to face its final test:
NASA's Artemis I mission is nearly complete, and so far Orion's daring flight far beyond the Moon has gone about as well as the space agency could hope. However, to get a passing grade, the mission must still ace its final test.
This final exam will come on Sunday, when the spacecraft starts to enter Earth's atmosphere at 12:20 pm ET (17:20 UTC). During the course of the next 20 minutes, before Orion splashes down in the Pacific Ocean off of Mexico's Baja Peninsula, it will need to slow down from a velocity of Mach 32 to, essentially, zero before dropping into the water.
This is no small feat. Orion has a mass of 9 metric tons, about the same as two or three large elephants. Its base, covered with a heat shield designed to slowly char away during passage through Earth's atmosphere, must withstand temperatures near 3,000 degrees Celsius.
There are two main elements for this reentry that NASA is aiming to test—the performance of this heat shield and of its parachute system. For the mission's planners, the heat shield is the biggest concern.
"Reentry is our priority-one objective for a reason," said Mike Sarafin, who leads the Artemis I mission management team. "There is no arcjet or aerothermal facility here on Earth capable of replicating hypersonic reentry with a heat shield the size of Orion. And this is a brand-new heat shield design. It is a safety-critical piece of equipment. It is designed to protect the spacecraft and the astronauts on board. So the heat shield needs to work. We can buy down some of that risk on the ground, but not in terms of coming back at Mach 32."
NASA tested a boilerplate version of the Orion spacecraft in December 2014, launching it to an altitude of nearly 6,000 km. From that orbit Orion reentered Earth's atmosphere at a velocity of 9 km/s. For Artemis I, Orion will return at a speed of 11 km/s. That may not sound like all that big of an increase, but for reentry velocity, the increase in convective and radiative elements is exponential as velocity goes up, said Jim Geffre, Orion's vehicle integration manager.
"So the velocity effect is tremendous, and that's why the increase in heat load from a low-Earth orbit entry to lunar velocity is so much higher," he told Ars.
The Orion vehicle flown during the EFT-1 mission featured the same basic ablative material, an epoxy known as AVCOAT that was also used by the Apollo capsules during their returns from the Moon half a century ago. Like the Apollo capsule, this AVCOAT material was injected into honeycombed cells at the base of the spacecraft.
For the Artemis I flight and future missions, however, NASA has changed to a design of "molded" blocks of AVCOAT for the base of Orion. This was done, in part, to make it faster and more efficient to produce these heat shields. Unlike with the honeycomb design, these molded-block heat shields can be built in parallel with the spacecraft's base, rather than needing to be affixed afterward.
(Score: 2) by Snotnose on Sunday December 11 2022, @01:19AM
This is pretty much figured out engineering, granted proofed via a bunch of math above my head and algorithms.
as opposed to, I dunno, pretty much figured out 30 years ago this shit is stupid hard engineering. See also, fueling the damned thing via liquid hydrogen. How small are those molecules again?
I guess my point is, the odds of recovering it after dunking it into the ocean are much higher than launching, err, fueling the damned thing in the first place.
Of course I'm against DEI. Donald, Eric, and Ivanka.
(Score: 0) by Anonymous Coward on Sunday December 11 2022, @01:31AM (1 child)
I know they want to make it relatable, but people have as much intuitive feel for "9 metric tons" as they do for "two or three elephants."
(Score: 0) by Anonymous Coward on Sunday December 11 2022, @01:55AM
Well, at least they gave both.
(Score: 0) by Anonymous Coward on Sunday December 11 2022, @02:14AM (8 children)
The summary leads one to believe we've never done this before.
(Score: 1) by khallow on Sunday December 11 2022, @04:02AM
Keep in mind that the people who actually developed the Apollo heat shields probably retired decades years ago. "We" didn't have anything to do with that.
(Score: 2) by janrinok on Sunday December 11 2022, @12:46PM (6 children)
Well, we haven't. This is a new craft. The heat shield has been constructed in a different manner. It has not been possible to test it with the forces and temperatures that are expected during re-entry.
There is a reason that this craft is unmanned - you wouldn't expect them to assume that as the Apollo capsules worked then this one must be safe too, would you? Space exploration is dangerous enough when we try to manage all the risks - but nothing justifies taking unnecessary ones.
[nostyle RIP 06 May 2025]
(Score: 0) by Anonymous Coward on Sunday December 11 2022, @02:23PM (3 children)
They have tested an Orion heat shield before. Probably more importantly, the life-support system on this capsule isn't ready. That's going to be tested for the very first time when astronauts are onboard and dependent on it working correctly.
(Score: 2) by janrinok on Sunday December 11 2022, @06:53PM (2 children)
Perhaps you ought to offer your expertise to NASA - I'm sure that they will jump at the chance to take you on and for you to show them how it should be done. :^)
[nostyle RIP 06 May 2025]
(Score: 0) by Anonymous Coward on Sunday December 11 2022, @07:37PM (1 child)
Which facts are you disputing? That they have tested Orion re-entering [wikipedia.org]? Or that the life support wasn't working on this flight [space.com]?
Or are you just being an asshole?
(Score: 2) by janrinok on Monday December 12 2022, @07:45AM
Emphasis mine.
Have you read the TFS?
[nostyle RIP 06 May 2025]
(Score: 0) by Anonymous Coward on Monday December 12 2022, @01:51AM (1 child)
It's a bigger Apollo with a glass cockpit. There is no reason not to use the same heat shield, unless they forgot how to make them.
But I hope they use better wiring insulation. That was the most notable problem with Apollo
(Score: 2) by janrinok on Monday December 12 2022, @07:42AM
Yes there is. The tiles on the Apollo heat shield had to be applied as a separate function during construction. This has been changed - and it actually says why this was do in TFS:
[nostyle RIP 06 May 2025]
(Score: 4, Funny) by maggotbrain on Sunday December 11 2022, @05:22AM
I don't quite remember when I began noticing this; but, for some time now I've been amused by how reporters select objects for comparison in their articles. In this case, the reader should be able to relate to the concept of how much "two or three elephants" weigh in order to understand how heavy the Orion spacecraft is. Are these African elephants? Asian? Is that similar to one blue whale, or two baby sperm whales? How is the reader supposed to possibly relate to that comparison? "Oh, yeah, two or three elephants. Makes sense to me...."
I could very well be mis-remembering this; but, I seem to recall the full spread of the JWST mirrors described as being the size of about "two regulation size clay tennis courts"(Why clay, exactly?). We are all familiar with the size of a regulation clay court, right? Or was it two and half Olympic-sized swimming pools?
Another time, a recently observered asteroid that was passing by Earth was determined to be approximately "vending machine" sized and was obviously determined to not pose a threat to our continued existance.
This seems to happen most often when reporting on space-related news. Or, at least, that's where I notice it. Should I be more concerned when a "four school bus length" object is approaching Earth, or when it is the size of an average "family-friendly country-style buffet restaurant"?
Anywhoo. This has been my procrastinatioin rant for the evening. Cheers!
(Score: 0) by Anonymous Coward on Sunday December 11 2022, @06:15PM
Splashdown [nasa.gov]!