[gaigalas]

> A mechanical coupling is not that difficult to design

[citation needed]

> Reignite only the second stage.

Baby delta-v. Weaker than my Uno Mille with a staircase on top.

> right orientation

Trying to re-orient a low earth orbit into a reentry-from-moon-insertion is like trying to bend the path of a bullet.

Get your shit together, play some Kerbal Space Program at least.

> The shield doesn't care what's inside the Orion - it cares about mass.

[citation needed]

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Buddy, I don't have time for Elon fantasies.

[rbanffy]

> Get your shit together, play some Kerbal Space Program at least.

I assumed you had actual knowledge of how orbital mechanics work. Please, continue playing your kideogames.

A Falcon Heavy can deliver more than 20 tons to GEO and an Orion capsule weigths about 10 tons. GTO is usually about 10 km/s at perigee of 200 km, meaning even with a full payload, a FH can place an Orion at an orbit that coasts above most of the atmosphere at about 90% of the speed of a returning Orion - and that on a stable-ish orbit - a suborbital trajectory would allow a higher apogee and a higher return speed. Now assume my mechanical design skills allow me to mount the capsule with less than 10 tons of material - this would mean we still have enough propellant on the second stage to give the ship a sizable boost if we so wanted. As for the maximum thrust, a high apogee suborbital trajectory would allow plenty of time for that - a good couple hours at least. That's way more than the longest burn the Merlin engine is rated for. I could dig up the exact numbers for these parts, but the margins seem more than ample enough.

> Buddy, I don't have time for Elon fantasies.

I'm not impressed by your insults. Bring in the math.

[gaigalas]

> I'm not impressed by your insults.

It's not an insult. You're overestimating SpaceX capabilities and I'm correcting you. There's no shame in that. I do find strange that you're insisting on it though.

> Bring in the math.

Falcon Heavy never carried anything similar to Orion. It never performed a second-stage "second burn trick" [sic]. There has never been a shield test like you described. Those things were never even hypothesized formally.

You made the claim that it can do those things with insufficient evidence. You need to back that up. I'm not going to fall for a reversal of an onus that you, and you alone, should prove.

[rbanffy]

All the evidence required is the mass of the object and the total kinetic energy the second stage can add to the object - rockets are like that: they don't care what they are pushing or in which direction - it's possible to get the required speed with a 20 ton payload. The idea was never proposed because of numerous reasons (one of them not thinking it would yield a better understanding of how the Orion heat shield works - they thought it was perfectly fine to test their theory with a crew on board, and I applaud their confidence).

There never was a shield test like this. The only other crewed capsule in operation today has had a few uncrewed flights without incident before taking astronauts on board, under much more forgiving reentry profiles. I sincerely hope the Artemis II shield shows no chipping and is well within the expected behaviors according to their current understanding, but, then, again, Artemis III will carry a new design, with changes informed by the first Artemis flight (and near failure - it was uncomfortably close to burning through the hull). And it will have astronauts on board on its first flight.

Doing a shield study on the lines I proposed would be politically complicated for NASA and would undoubtedly serve as an argument to further cut funding to Orion, as it would show they don't trust their designs, or don't completely understand them. I would also delay the next launch, which is, again, a politically charged thing.

I trust their math, but there are incentives for cutting corners here. Both Challenger and Columbia were lost because people forgot they were experimental vehicles operating under conditions we don't fully understand. They were treated like 737s.

[gaigalas]

> rockets are like that: they don't care what they are pushing or in which direction

That is just incorrect. Fuel tank design and arrangement, for example, is full of internal mass dynamics.

> would be politically complicated for NASA

Let me repeat this again: Falcon Heavy cannot carry Orion. There is no complication here.

NASA and SpaceX collaborate heavily. NASA doesn't build rockets, they're administrators. If SpaceX could be used, they would have used it (as they did with Dragon and so many other projects).

Stop trying come up with makeshift excuses for the lack of technical background you failed to provide.

> Both Challenger and Columbia were lost because people forgot they were experimental vehicles operating under conditions we don't fully understand.

Irrelevant attempt at misdirection. This has nothing to do with whether Falcon Heavy can or cannot test Artemis shields.

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You're desperately trying to pivot the discussion from a technical one (in which you demonstrated lack of basic knowledge about several important topics) to a political one (which is murky and easier to navigate into a tarpit).

[rbanffy]

> Falcon Heavy cannot carry Orion.

Why? Explain your reasoning.

[gaigalas]

I already did.

https://news.ycombinator.com/item?id=47730179

Initially, I presented it as "please elaborate" questions. A courtesy, to give you the benefit of the doubt.

So far, you were not able to answer them with the same kind of courtesy that I initially offered.

Instead, you doubled-down on answering vaguely, hoping that I would slip at some point to a defensive position in which I would offer math and numbers, which are totally YOUR responsibility to provide, since YOU MADE THE CLAIM.

I don't need to prove that something that never happened is impossible. You need to prove that what never happened is possible (because you said it is). Capisce? It's basic science communication.

I don't need to do anything here. I'm right until you're able to prove otherwise.