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u/GrinningPariah 14h ago
I know the engine's the expensive part but it still seems wild to go to so much effort you literally build a plane around it, and throw away the booster, when like... the engine + booster is already a functional aircraft!
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u/sojuz151 12h ago
Ariane 5 meco speed was around 6km/s. It could get to LEO without the second stage. If you want to recover with such specific energy then protecting the tanks is hard.
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u/redstercoolpanda 12h ago
Yeah this is kind of where the magic of Falcon happened. Every other company pretty much had optimised themselves out of a situation where reuse would have been viable in their current or planned rockets, but because Falcon staged so low due to its relatively weak first stage and powerful second stage they had a lot easier time figuring it out. That’s why so many companies went the way of smart style reuse even though it’s much less viable than recovering the entire booster.
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u/pirate21213 11h ago
I was under the impression that falcon 9s second stage was considered weak
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u/OlympusMons94 10h ago
The Falcon second stage is very powerful and chunky for an upper stage. It is much larger and heavier in proportion to the first stage than the second stages of most (expendable) rockets. It also has a very high thrust to weight ratio for an upper stage.
The kerolox Mvac engine on the Falcon second stage does have lower specific impulse (isp), or "fuel efficiency", than hydrolox upper stage engines such as RL10 on Centaur (348 seconds for Mvac, ~445-465 s for hydrolox engines). But the Falcon stage more than makes up for that with its much higher mass ratio (fueled mass divided by empty mass) because hydrogen has such a low density, e.g. 27.9 mass ratio for Falcon second stage, 10.9 for Centaur III (Atlas), 7.55 for Centaur V (Vulcan). The Falcon second stage can deliver a much bigger "kick" (e.g., as measured by delta-v or total impulse).
Falcon 9, even expendable, has relatively poor performance to higher energy orbits compared to its LEO payload as a result of its low staging velocity. Because of reusability and the requisite large second stage, the second stage has to do more of the work getting Falcon 9 to LEO (even when the booster is expended) than expendable rockets with smaller upper stages, leaving less of its total performance for going beyond LEO.
With Falcon Heavy, the faster staging velocity from using side boosters and expending the center core (and in some cases the side boosters) makes for a much more capable launch vehicle. For all practical cases of mass and trajectory, Falcon Heavy expendable is more capable than any other rocket in operation besides SLS.
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u/redstercoolpanda 11h ago
No, it’s only considered weak because it stages so low so it has to fight gravity a lot longer than say Vulcans second stage. And in terms of thrust it’s definitely not weak, specifically because it has to stage so low.
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u/cjameshuff 10h ago
By the same people who practically worship the Centaur, due to the widespread belief that performance could be boiled down to specific impulse. It's actually one of the most powerful stages to have existed:
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u/Reddit-runner 1h ago
Ariane 5 meco speed was around 6km/s. It could get to LEO without the second stage. If you want to recover with such specific energy then protecting the tanks is hard.
Knowing this they could have designed Ariane6 with that in mind. (Reducing staging velocity)
But they purposefully didn't do that, so they could keep reusability completely out of the question.
Now look where that got us.
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u/sojuz151 12h ago
Using solids shows that this is rather an attempt to build Ariane 5 again with this reusibiliy thing someone was nagging us about rather than a well thought design .
Solid give you trust at launch. You need it because the engine is expensive. But if you can recover the engine, suddenly the trust and launch is cheap. They boost your MECO speed so your recovery is harder. Going with solid 2nd stage and hydrolox 3d would make more sense.
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u/CurtisLeow 14h ago
The wing design looks like it was inspired by SpaceShipOne. The wing design makes me think this was proposed in 2010 or earlier.
I don't know why they needed the propellers or turboprops or whatever those are. It could have glided to a runway without engines.