NASA may alter Artemis III to have no Starship landings.

RGClark · 2024-04-21 17:01:00

NASA may alter Artemis III to have Starship and Orion dock in low-Earth orbit
If it were to happen, a revised Artemis III mission could echo Apollo 9.
ERIC BERGER - 4/19/2024, 11:20 AM
https://arstechnica.com/space/2024/04/n … rth-orbit/

Note the missions proposed wouldn’t even use refuelings for Starship.

I’m suggesting the reason why NASA is proposing this now is because of the low 40 to 50 ton payload capability for the current Starship Elon announced, a number too low to perform the refueling missions of Starship:

Starship Faces Performance Shortfall for Lunar Missions
by Alex Longo
https://www.americaspace.com/2024/04/20 … -missions/

Bob Clark

Mars_B4_Moon · 2024-04-21 17:19:48

a never done before event

many potential gains, risks, hazard and benefits

there were previous discussion and these were perhaps linked before

NASA makes a significant investment in on-orbit spacecraft refueling
https://arstechnica.com/author/ericberger/
In-space fueling technologies enable a new paradigm for spaceflight.

Preliminary analyses on technical and economic viability of moon-mined propellant for on-orbit refueling
https://www.sciencedirect.com/science/a … 6523000061

pdf file
https://ntrs.nasa.gov/api/citations/202 … matted.pdf

Here's How SpaceX's Starship Will Refuel Without Landing
https://screenrant.com/spacex-moon-land … ng-system/

GW Johnson · 2024-04-22 09:36:48

NASA is rethinking what to do with Artemis 3 because it has no credible lander candidates for going to the moon's surface anytime soon. Not from SpaceX, not from Blue Origin. Nothing yet flying except highly-experimentally.

As for Starship payload capacity, it is way too premature to be drawing any conclusions about that. These prototypes being tested (and all of them lost so far) bear little resemblance to what the final product will be, once the thing becomes successful (if it does).

I don't know why Blue Origin's lander is not flying experimentally yet.

I do know why Starship is not ready yet: (1) the job is bigger and more difficult than they first thought, requiring more tests and more time to "get it right", and (2) delays getting licenses to fly early on lengthened the time considerably, because Musk acted like an idiot and had SpaceX violate the terms of its licenses. Shotwell makes good technical decisions, Musk has a history of making bad ones. They would be bankrupt and out of business without her and the staff she has.

GW

SpaceNut · 2024-04-22 17:02:15

Artemis Reference Guide

GW Johnson · 2024-04-29 09:06:24

From today's issue of "The Daily Launch", AIAA's newsletter:

-------

ARS TECHNICA

NASA still doesn’t understand root cause of Orion heat shield issue

As Artemis I streaked back into Earth's atmosphere at the end of the mission, the heat shield ablated, or burned off, in a different manner than predicted by computer models. Amit Kshatriya, who oversees development for the Artemis missions in NASA's exploration division, said Friday that the agency is still looking for the root cause of the heat shield issue. Managers want to be sure they understand the cause before proceeding with Artemis II.

------

The last sentence is code for the managers who do not want to admit they made a mistake by installing the Artemis II heat shield before it was tested on Artemis I. This is CYA manager BS.

Many of us have already guessed why the Artemis I heat shield misbehaved vs expectations: they removed the hex to make it cheaper to build, and so lost the composite strengthening effect of that hex upon the char layer of the Avcoat polymer. Test data always (ALWAYS!!!) trumps computer code predictions.

And if this did not show up in the ground arc jet tests, then they did not run the right tests. It is the sideways fluid shearing force scrubbing at the heat shield that strips poorly-supported char off in chunks. Happens all the time in solid rockets, and especially in subsonic combustion ramjets. Been there and done that, for many years.

Just in case you haven't kept up, the first Orion flight test was not classified as an Artemis mission. That one flew the Apollo-type Avcoat-in-hex heat shield, and it performed just fine, and exactly as expected. The second Orion test flight was Artemis I, with the no-hex variant of the Avcoat heat shield that eroded both erratically geometrically, and on-average significantly faster than expected, although not quite enough to truly endanger the capsule. They had already installed one of these no-hex Avcoat heat shields on the Artemis II/third Orion, before actually testing it on Artemis I (the second Orion).

The managers neither want to admit their mistake, nor spend the money to return to the Apollo-type Avcoat-in-hex. They want the engineers to find them some way out of the corner they painted themselves into, because it too closely resembles the same management stupidity that killed two shuttle crews.

Just how stupid is that?

GW

Last edited by GW Johnson (2024-05-01 15:11:26)

SpaceNut · 2024-04-29 17:08:50

SpaceX’s Starship lunar-landing tech passes a key in-space refueling test

https://youtu.be/QTv_r1txRZ4

GW Johnson · 2024-05-01 15:18:56

The first link in Spacenut's post #6 takes you to a magazine article. The article says the propellant transfer test was successful, but provides zero detail about how successful or how it was done. And I have seen nothing from any other sources.

It does mention that determining the "settling thrust" is crucial, which is true. It's not so much the thrust as it is the acceleration level produced by it. The globules and the film on the tank walls must have time to settle into one end where the drain is, or you cannot get suction with a pump. One possible estimate is 3 x "time constant", where "time constant" is the time it takes for a particle to fall from one end of the tank to the other, at the acceleration level induced by the ullage thrust. Lower thrust is lower acceleration is a longer "time constant". Simple as that.

One thing I notice is that nobody is talking about using spin acceleration instead of linear acceleration. This costs some additions to the plumbing, but it avoids changing the trajectory the way linear acceleration inherently does.

The second link in Spacenut's post takes you to a rather speculative youtube video that proposes to turn one-way Starships into buildings on site.

GW

Last edited by GW Johnson (2024-05-01 15:20:22)

kbd512 · 2024-05-01 21:23:08

If I was an astronaut, I'd be mortified that the Orion capsule has been in development for over a decade at this point, but they still don't know why the heat shield is not behaving as it should. Given that Avcoat is a legacy technology with thoroughly proven flight heritage behind it, that strikes me as wrong on multiple levels. Tinkering with a known working design that's done its job every single time, merely to save a buck or two, is unforgivable. Avcoat wasn't designed to be cheap, it was designed to withstand a screaming reentry. If you're that concerned about cost, then you'd never fly to space to begin with, let alone go to the moon. Whoever made that decision should be flown on the first crewed mission, whether they have astronaut training or not. Let's see how fast they make the correct design decisions when it's their rear end that gets BBQ'd.

I wonder how much time and money has been lost trying to save money while doing something that will never be cheap or easy.

GW Johnson · 2024-05-02 14:52:46

There were 2 things going here. First, some young whippersnappers believed computer predictions and told NASA managers the no-hex Avcoat heat shield would work, without it ever having been actually flown. Only arc jet tests, and if the arc only hits square on, you won't see the scrubbing action that causes this. (Anybody who had ever actually done anything would know better: test data ALWAYS trumps computer predictions, but old hands are no longer kept on staff.)

NASA managers jumped at the chance to shorten schedule and lower cost. Even after killing 2 shuttle crews by valuing cost and schedule far above safety of lives, they still have NOT learned the lesson not to do space flight that way. So they installed the no-hex heat shields one-after-the-other on Artemis 1 (second flight of Orion) and 2 (third flight of Orion and first one with a crew), expecting it to work just as well as the Apollo-style Avcoat gunned into hex cells that flew on the first Orion flight.

It didn't work. Now they have an Orion with a defective heat shield design, and a looming manned flight. They want their whippersnappers to find a way past this corner they painted themselves into, but such does NOT exist. The last thing they want to do is publicly admit they were wrong, and that their mistake has cost both money and schedule time (to take the bad heat shield off of Artemis-2(3rd Orion), build the right one, and install it, before risking a crew in it. They would rather risk the crew's lives, and they want the whippersnappers to "justify" that. But they can't, and the inspector general report confirms that, so the NASA managers bad-mouth that report.

This is the same arrogant-and-ignorant management BS that killed 2 shuttle crews, and likely played a role in the deficient Apollo design that killed the Apollo-1 crew. Management culture at NASA quite clearly did not learn a thing from either the Challenger inquiry or the Columbia inquiry, despite being publicly exposed during the Challenger inquiry for attempting a cover-up to deflect blame for bad decisions.

The time and money trying to justify this bad decision to risk a crew's lives instead of fixing a fixable problem could have been better spent just fixing the problem. There has got to be a way to automate (at least partly) the process of gunning Avcoat into 380,000 hex cells on an Orion heat shield. But nobody at NASA seems to have thought about that.

The same arrogant/ignorant management style that values money over lives infected Boeing, too, after it took over McDonnell-Douglas. And we have all seen where that led recently.

GW

Last edited by GW Johnson (2024-05-02 14:54:21)

SpaceNut · 2024-05-02 15:12:41

NASA’s Readiness for the Artemis II Crewed Mission to Lunar Orbit

Specifically, NASA identified more than 100 locations where ablative thermal protective material from Orion’s heat shield wore away differently than expected during reentry into Earth’s atmosphere. Engineers are concurrently investigating ways to mitigate the char loss by modifying the heat shield’s design or altering Orion’s reentry trajectory.

NASA inspector general report highlights issues with Orion heat shield

RGClark · 2024-05-03 10:54:54

GW Johnson wrote:

From today's issue of "The Daily Launch", AIAA's newsletter:
-------
...
Many of us have already guessed why the Artemis I heat shield misbehaved vs expectations: they removed the hex to make it cheaper to build, and so lost the composite strengthening effect of that hex upon the char layer of the Avcoat polymer. Test data always (ALWAYS!!!) trumps computer code predictions.
And if this did not show up in the ground arc jet tests, then they did not run the right tests. It is the sideways fluid shearing force scrubbing at the heat shield that strips poorly-supported char off in chunks. Happens all the time in solid rockets, and especially in subsonic combustion ramjets. Been there and done that, for many years.
Just in case you haven't kept up, the first Orion flight test was not classified as an Artemis mission. That one flew the Apollo-type Avcoat-in-hex heat shield, and it performed just fine, and exactly as expected. The second Orion test flight was Artemis I, with the no-hex variant of the Avcoat heat shield that eroded both erratically geometrically, and on-average significantly faster than expected, although not quite enough to truly endanger the capsule. They had already installed one of these no-hex Avcoat heat shields on the Artemis II/third Orion, before actually testing it on Artemis I (the second Orion).
...
GW

Since this is a safety issue is there a way to communicate to high level managers directly your concerns?

Bob Clark

SpaceNut · 2024-05-09 19:36:14

The heat shield issue was greater than I had thought.
NASA watchdog report: 100+ cracks on heat shield biggest threat to human moon mission

https://oig.nasa.gov/wp-content/uploads … 24-011.pdf

reentry speeds coming in from a lunar trajectory reach nearly 25,000 mph, which is about 40% faster than what astronauts face when returning from low-Earth orbit in SpaceX’s Crew Dragon. The heat shield has to endure temperatures close to 5,000 degrees Fahrenheit.

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#1 2024-04-21 17:01:00

NASA may alter Artemis III to have no Starship landings.

#2 2024-04-21 17:19:48

Re: NASA may alter Artemis III to have no Starship landings.

#3 2024-04-22 09:36:48

Re: NASA may alter Artemis III to have no Starship landings.

#4 2024-04-22 17:02:15

Re: NASA may alter Artemis III to have no Starship landings.

#5 2024-04-29 09:06:24

Re: NASA may alter Artemis III to have no Starship landings.

#6 2024-04-29 17:08:50

Re: NASA may alter Artemis III to have no Starship landings.

#7 2024-05-01 15:18:56

Re: NASA may alter Artemis III to have no Starship landings.

#8 2024-05-01 21:23:08

Re: NASA may alter Artemis III to have no Starship landings.

#9 2024-05-02 14:52:46

Re: NASA may alter Artemis III to have no Starship landings.

#10 2024-05-02 15:12:41

Re: NASA may alter Artemis III to have no Starship landings.

#11 2024-05-03 10:54:54

Re: NASA may alter Artemis III to have no Starship landings.

#12 2024-05-09 19:36:14

Re: NASA may alter Artemis III to have no Starship landings.

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