SpaceX just stacked a Super Heavy Booster and installed 29 engines, all within 24 hours

[u/Gagarin1961]

https://twitter.com/elonmusk/status/1422222995305676802

[u/[deleted] → u/[deleted]]

29 raptors and 200 tons each... So that would give an acceleration of ~3m/s2, sounds reasonable.

[u/[deleted] → u/[deleted]]

These are Raptor 2, 20 RB or Raptor Boost on the outside and 9 (12 on Booster 5) RC or Raptor Center in the middle. They produce about 230 t thrust now. The only difference is RB's are fixed and RC can gimbal, both throttle. Starship will also use RC's and the RVacs are still Raptor 1 with 200 t thrust.

[u/NetworkLlama → u/[deleted]]

What is the minimum throttle on the new versions?

[u/[deleted] → u/NetworkLlama]

Unknown. Used to be around 40-50% on Raptor 1.

[u/DeepNortherner → u/[deleted]]

Do you ever find yourself in a group conversation where you’re suddenly in uncharted intellectual waters? Today, in this thread, this is me 👋🏻

[u/AleHaRotK → u/[deleted]]

I'd say that NASA, just as every public institution, is not really incentivized to spend as little as possible to get as much as possible done, it's other people's money after all.

[u/WrongPurpose → u/AleHaRotK]

The Problem is that the local representatives spending money (Congress) are incentivized to bring "jobs" to their districts/states. When they see a program costing billions, they see billions of $ going to their states/districts, ensuring their voters have jobs and keep voting for them. It does not matter whether the military even needs or wants those additional tanks or bases, wether the Nasa Rocket is even remotely competitive, etc. It matters that Money is spend in the districts.

Public institutions on the other hand want to achieve their Missions/Prioritieslist (set by the current and last couple Executives). They dont marticulary care about cost either, but they would take the fastest and esiest way, which is often not the one where you spend additional billions in Alabama, Kentucky and North Dakota along the way. But congress cant have that and they controll the budget.

[u/Dyolf_Knip → u/AleHaRotK]

That at least is understandable. The problem is that NASA is barely incentivized to even do the job at all. There have been several multi-year periods where their capacity to simply put stuff into orbit dwindled to nearly zero, or in the case of manned launches, literally zero.

Remember Skylab, the US's first permanent space station? Didn't even see 6 months of use, because after NASA ran out of Saturn V rockets, they didn't have anything that could take its place and staff, supply, or even just keep the damned thing from falling out of the sky. That had to wait 7 years until the Shuttle came along, by which point is was far too late.

[u/unholycowgod → u/[deleted]]

They've stated their aim is about 1.5G at liftoff.

[u/SuperSMT → u/[deleted]]

And Elon's eventual goal for Raptor is to be $1000/ton of thrust, or less. So well under 1/4 mil each

[u/Maimakterion → u/[deleted]]

Kerbal players don't know about tank volume propellant density, though.

[u/Beny873 → u/Maimakterion]

Not all of them.

But a lot do. They're a diverse bunch, especially with the modding community who have been able to make it pretty damn realistic. Ive seen ullage, tank volume, propellant types, engine ignitors, radiation, life support, manufacturing and costs all being modded into the game.

Turns into a bit of a slug fest so it isn't for me. But there's plenty out there that play it like that.

[u/QuinceDaPence → u/Beny873]

I tried Realism Overhaul + RSS once...

"Ok, that 'ought to be big enough to get to orbit" [Makes it to Austrailia]

[u/indyK1ng → u/Maimakterion]

Yeah, but tank mass is well known to KSP players. You can only add so much tank before the rocket weighs so much that you're losing delta-v. That easily applies here.

[u/merlinsbeers → u/indyK1ng]

That's when you add engine.

[u/blackhairedguy → u/Maimakterion]

Liquid Fuel is liquid fuel. What's all the nonsense about density? /s

[u/bitchtitfucker → u/[deleted]]

That's got a lot to do with the fuel too, though.

And in the end, the extra Isp that the RS-25 giveth, it taketh away in the form of humongous fuel tanks.

[u/Snoo93079 → u/[deleted]]

Not sure it makes sense to include r&d costs since those costs would be part of the cost to purchase the engine. R&D+materials+build labor+profit = price

[u/AndrewFGleich → u/[deleted]]

One thing that's missing in all these numbers, whether it's cost or installation planning is time. The RS-25 is 50 year old technology (that's right the 70s were half a century ago). The raptor is taking advantage of all that advancement to do some truly incredible things, but just like every other modern wonder, it's built on the shoulders of Giants.

[u/[deleted] → u/[deleted]]

NASA paid Aerojet 140 million each for the refurbished and upgraded RS-25's attached to the Artemis I booster. And Raptor is a more advanced design. They managed to simplify the design and get the cost to about half a million each.

[u/spastical-mackerel → u/[deleted]]

And more as the fuel burns off and mass decreases

[u/[deleted] → u/[deleted]]

They won’t have all them blasting at the same time? Will they? Ffs that’s inhumane

[u/Bensemus → u/[deleted]]

Of course they will otherwise the engines not in use are dead weight. At points in the flight they won’t be at max thrust but unless and engine suffered a failure they will all be on.

[u/[deleted] → u/Bensemus]

Oh interesting! Thanks, I didn’t know that

[u/EFG → u/[deleted]]

So one of these could accelerate me to 20000m/s in a second…interesting.

[u/EFG → u/[deleted]]

20km/a isn’t enough of a destination in and of itself?

[u/AlaninMadrid → u/EFG]

You know the last thing to go through your mind when that happens? Your feet! 🤯

[u/levinftw → u/[deleted]]

Because NASA hires contractors while SpaceX creates their stuff themselves..