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SpaceX Discussion Thread


Skylon

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2 hours ago, Nightside said:

what is the ratio for methalox 4:1

4:1 is stoichiometric by molar mass?

raptor uses 3.6:1 .....fuel-rich for lower temperature combustion at the cost of a few seconds of isp.

3.6kg lox 1 kg methane.

You can check the ratio against the fuel load for the BFS.....

240 tonnes methane, 860 tonnes lox.

Ratio 3.583

Raptor at 2000kN/330s is burning about 600kg of propellant per second.

Bulk methalox density is ~900kg/m3 when subcooled compared to ~1100kg/m3 for kerolox. All subcooled.

lox is ~1230 kg/m3 @ 70K and methane is ~440 kg/m3 @ 96K

tank volumes are split about 44% CH4 and 56 % LOX.

 

 

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7 hours ago, CatastrophicFailure said:

i think all the hubbub about the “radical change in materials” was just his biggest troll since... well, at least like a month or two...

I’m trying to imagine all the misguided ridicule going on right now in the hardcore anti-Musk camp.

Don’t care. I’m on this dieselpunk train.

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5 hours ago, RealKerbal3x said:

It's happening, fellas!

THE STARSHIP IS COMING!

And it's made from stainless steel!

What is this, Project Orion? (The nuclear pulse one)

Well, jokes aside, it sounds like they might get a landing test before the end of the decade. If they’re lucky.

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2 minutes ago, Bill Phil said:

What is this, Project Orion? (The nuclear pulse one)

Well, jokes aside, it sounds like they might get a landing test before the end of the decade. If they’re lucky.

They’ll be doing a landing test on their first flight.

Not like they have much choice.

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1 hour ago, NSEP said:

Does that also mean the BFR that will fly to the Moon and stuff will also be reflective and shiny (expect for the maybe black heatshield)? Cool!

No. At least, not as far as I understand. The finial, orbital+ vehicle will still be all fancy and composite, it’s the hopper(s) that will be stainless. 

Makes a lot of sense, too. Notice how quickly the thing is going together, and on an unimproved dirt lot in the middle of bloody nowhere to boot? They can build these things fast, and they can build them cheap. Relatively. I’m guessing SpaceX is expecting to lose more than one along the way, like they did with the original Grashopper, and will probably go through different versions as well (the one doesn’t have the folding fins like the end product, for example).

 

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1 hour ago, Ultimate Steve said:

Size comparison from NSF:

1535543.jpg

 

Interesting... I wonder if they’ll schlep a drone ship to the Gulf eventually specifically to do longer hops?

27 minutes ago, NSEP said:

So bassicly the Starship Grasshopper is just a big tin can, with a rocket inside of it?

The tin can is the rocket.  :D

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20 minutes ago, Mad Rocket Scientist said:

The design seems to be converging with some kind of reusable big dumb booster.

A little, but remember, its still is supposed to have 30+ engines on the first stage and would need to do propulsive landings in order for it to be reused. Big, but not exactly dumb.

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7 hours ago, NSEP said:

 

Gwynne’s engineers really outdid themselves on the “brutal simplicity” front. It’s beginning to sound like an actual workhorse.

Michail Timofeevich would be proud.

original.png

However, a possible failure mode I’m seeing is recirculated exhaust from the engines creeping up the structure and depositing soot. It’s how the first stages of either Saturn would get completely black by the end of the burn. I know, methane, but long as it’s got carbon...

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