[bsilvereagle]

> “Our test facilities can’t reach the combination of heat flux, pressure, shear stresses, etc., that an actual reentering spacecraft does. We’re always having to wait for the flight test to get the final certification that our system is good to go.”—Jeremy VanderKam, deputy manager for Orion’s heat shield, speaking in 2022

This is a strange claim, considering NASA used to have 2 facilities that were capable of this - one at Johnson and one at Ames. They were consolidated (https://ntrs.nasa.gov/api/citations/20160001258/downloads/20...) but it seems like the Arc Jet Complex at Ames is still operational https://www.nasa.gov/ames/arcjet-complex/

[idlewords]

The Orion heat shield is sixteen feet across. NASA's test facilities can only test small material samples in these facilities, not capture how the entire heat shield will behave.

[sillysaurusx]

How does SpaceX test it? Have they needed to solve this problem?

[SyzygyRhythm]

There were 19 successful unmanned Dragon 1 missions before Crew Dragon, and an unmanned Crew Dragon mission before the first crewed one (actually two missions, but one didn't reenter from orbit). The heat shield material and design was essentially the same and so there was a great deal of flight heritage.

[recursivecaveat]

In particular I don't think its physically possible to test Orion components in flight very many times. It relies on SLS which chews through 4 space-shuttle engines every time, which even with unlimited money I don't think you could acquire a large supply of very quickly.

[cryptonector]

Not only that, but it has to reach much higher altitudes in order to also reach the much higher re-entry velocities that it will have IRL. That makes testing Orion very expensive. Testing Crew Dragon was much much cheaper.

[pavon]

SLS is required to get Orion to the moon, but there are other options for LEO tests. Exploration Flight Test-1 was performed on a Delta IV Heavy, and Falcon Heavy is also capable of launching Orion to LEO (and now New Glenn, although that wouldn't have been an option at the time NASA needed to start work on another Orion test).

[hvb2]

By having a much higher launch cadence and then analyzing the flight hardware afterwards.

Also, they don't have anything human rated going beyond LEO. Coming back from the moon means you're going significantly faster and thus need a better heat shield

[pas]

... so the real problem is that to get back and slow down nicely would require so much more launch mass, right?

(By slow down I mean to change to an orbit that has more drag and wouldn't take forever to return to Earth.)

[idlewords]

They do iterative flight testing. Starship is I believe on its twelfth flight test; the first one was in 2023.

[margalabargala]

SpaceX tests these in prod. Kinda like Artemis I did.

[eru]

And this is actually a decent strategy, but you can only really do this when you have lots of unmanned flights.

[randomNumber7]

Nothing stops you from doing this with manned flights except that it's not culturally accepted currently.

But maybe that changes as NASA will demonstrate with artemis 2 and 3 (which will then use another newly desiged heat shield).

[eru]

> Nothing stops you from doing this with manned flights except that it's not culturally accepted currently.

Trained astronauts are also really 'expensive'. In addition to the innate worth of a human (which you might chalk up to culture), there's also lots of opportunity costs of what the astronaut could otherwise do, and replacement cost of their training etc are pretty high, too.

> But maybe that changes as NASA will demonstrate with artemis 2 and 3 (which will then use another newly desiged heat shield).

It would arguably be better (or less worse) if they did this deliberately and designed the mission from the ground up to be pushed to failure and to learn as much as possible from that failure. Instead of just accidentally sacrificing people.

[rkagerer]

By blowing up unmanned spacecraft and letting the ones that survive catch fire?

[swiftcoder]

SpaceX has a reusable launch vehicle, so they could afford to fly a whole mess of unmanned flights before they stuck a human in there

[jccooper]

Crew Dragon flew an automated demo flight before flying with crew. It was proceeded by 20 flights of Dragon 1 over 10 years.

Starship's heatshield has already been tested full-up half a dozen times. Many changes have been made as a result.

[whywhywhywhy]

They launch rockets