totm nov 2023 SpaceX Discussion Thread

[CatastrophicFailure]

also:

And there’s also this:

It’s an older article, but it checks out. I was about to read it...

Edited August 1, 2018 by CatastrophicFailure

[Wjolcz]

I googled Iridium-7 launch date and now I'm confused because it says it's already happened. So when is that RTLS in Vandenberg happening?

Edit: August 7 no, it's not. That one is from Florida.

Edit2: I'm guessing it's delayed for now?

Edited August 1, 2018 by Wjolcz

[CatastrophicFailure]

10 minutes ago, Wjolcz said:

I googled Iridium-7 launch date and now I'm confused because it says it's already happened. So when is that RTLS in Vandenberg happening?

Edit: August 7 no, it's not. That one is from Florida.

Edit2: I'm guessing it's delayed for now?

It did already happen.  The same booster that launched it will be launching again with SAOCOM later this month, and then RTLS-ing. 

[sevenperforce]

2 hours ago, wumpus said:

From a quick look at the wikipedia explanation of "gas core", I don't think there's much difference between a 1970s NTR and anything with a pebble bed (except the 1970s designed worked better and at least had the possibility of shutting down for a second burn).

Pebble bed can be run much hotter. Melting point of uranium is rather low, all things considered, but you can do a molten pebble encapsulated in a carbide shell. A pebble-bed reactor can also be refueled much more easily than a solid core.

2 hours ago, wumpus said:

You also need to look at how Isp is defined.  The moment you switch from hydrogen to methane, you might as well be using hydrolox.  If you have any uranium in your exhaust, forget about having any Isp (you can't afford to be throwing the heavy stuff away).

A pebble-bed reactor won't have any uranium in the exhaust, but even for a solid-core reactor, uranium that gets into the exhaust is pretty much a non-issue. Specific impulse is a measure of the amount of impulse produced by each unit mass of propellant. Impulse divided by time is thrust, and mass divided by time is mass flow, so this is also a measure of the thrust produced for a given propellant flow rate. Since core erosion isn't counted as part of propellant mass flow, it actually increases isp, technically.

[Wjolcz]

31 minutes ago, CatastrophicFailure said:

It did already happen.  The same booster that launched it will be launching again with SAOCOM later this month, and then RTLS-ing. 

Ooooh, okay. I thought it wasa already standing there waiting for launch.

[CatastrophicFailure]

36 minutes ago, Wjolcz said:

Ooooh, okay. I thought it wasa already standing there waiting for launch.

Nope, that’s the booster for Telkom 4, due to be test fired today for launch on the 7th. 

[tater]

7 minutes ago, CatastrophicFailure said:

Nope, that’s the booster for Telkom 4, due to be test fired today for launch on the 7th. 

I posted a couple pages up that this looks to have slipped to Thursday (static fire).

(this from a few hours ago)

[cubinator]

4 hours ago, kerbiloid said:

  Hide contents

Not really about SpaceX, but in whole.

If a reusable heavy rocket puts into orbit hundreds tonnes, then is it really important if it is SSTO rather than TSTO?

The first stage works from 0 to 50 km, then separates and returns back to the launch field.

The second stage gets into orbit, separates the payload, performs 1-2 turns and lands on the launch field.

Yes, you have to stack them again, but anyway you have to do this with its heavy cargo.

 

I agree, the whole point of an SSTO is for it to be all-in-one for reusability. If you have a 100% reusable two-stage rocket, it's just as good at reducing cost, and you don't have to land something 90 meters tall on Mars.

[TheGuyNamedAlan]

1 hour ago, cubinator said:

I agree, the whole point of an SSTO is for it to be all-in-one for reusability. If you have a 100% reusable two-stage rocket, it's just as good at reducing cost, and you don't have to land something 90 meters tall on Mars.

you gotta consider if the second stage is even worth recovering because i'm not sure if recovering the second stage is even worth it.

2 hours ago, CatastrophicFailure said:

Nope, that’s the booster for Telkom 4, due to be test fired today for launch on the 7th. 

are they landing it?

 

[Xd the great]

Test firing is not launching. Still they will recover it during the real launch.

[IncongruousGoat]

22 minutes ago, TheGuyNamedAlan said:

you gotta consider if the second stage is even worth recovering because i'm not sure if recovering the second stage is even worth it.

This is the BFR we're talking about, not Falcon 9. For F9, yes, trying to recover the second stage isn't worth it because the stage wasn't designed to be recovered. For BFR, though, where the second stage is designed for reusability from the outset, stage recovery is necessary to make the economics work out. Not recovering the BFS would mean throwing out 7 (!) Raptor engines, not to mention countless methane/oxygen RCS thrusters, huge carbon composite tanks, and whatever mechanisms are necessary for the payload bay.

[TheGuyNamedAlan]

3 minutes ago, IncongruousGoat said:

This is the BFR we're talking about, not Falcon 9. For F9, yes, trying to recover the second stage isn't worth it because the stage wasn't designed to be recovered. For BFR, though, where the second stage is designed for reusability from the outset, stage recovery is necessary to make the economics work out. Not recovering the BFS would mean throwing out 7 (!) Raptor engines, not to mention countless methane/oxygen RCS thrusters, huge carbon composite tanks, and whatever mechanisms are necessary for the payload bay.

well for the BFR there wouldn't be a second stage. there'd be a booster and the BFS which is a ship in itself (like the dragon) but that doesn't really matter because the BFR is so big that if they don't recover it, the cost could turn the BFR into the Apollo program where the cost of producing a new first and second stage every time it launched would overwhelm SpaceX or any company in general. 

[Xd the great]

12 hours ago, TheGuyNamedAlan said:

well for the BFR there wouldn't be a second stage. there'd be a booster and the BFS which is a ship in itself (like the dragon) but that doesn't really matter because the BFR is so big that if they don't recover it, the cost could turn the BFR into the Apollo program where the cost of producing a new first and second stage every time it launched would overwhelm SpaceX or any company in general. 

Imagine the horror of bfr landing sequence is impossible.

[tater]

 

[sevenperforce]

19 hours ago, cubinator said:

I agree, the whole point of an SSTO is for it to be all-in-one for reusability. If you have a 100% reusable two-stage rocket, it's just as good at reducing cost, and you don't have to land something 90 meters tall on Mars.

When I think about an indefinitely-reusable SSTO spaceship, I think about something like a Firefly-class ship. Dual air-turborocket engines (or RBCC engines) at the center of gravity that rotate, so you can land in a horizontal attitude for safety and loading purposes, with a big ultra-high vacuum engine for transfers.

For the present day, trying to do something like Skylon means such a low mass ratios that reusable TSTO is just way better.

[XB-70A]

Today’s static fire has just happened.

View from the North (taken with precisely 15 seconds of delay... next time, maybe)

 

From the South:

 

Edited August 2, 2018 by XB-70A

[CatastrophicFailure]

Confirmation:

Also: 

[CatastrophicFailure]

And now, this: 

 

Poop. 

[tater]

Indeed.

 

[sh1pman]

But! Crew Dragon will fly first (if nothing else slips). This I like. 

[CatastrophicFailure]

2 minutes ago, sh1pman said:

But! Crew Dragon will fly first (if nothing else slips). This I like. 

But we have a bigger risk of no NASA astronauts on the station since we’re about to run out of Soyuz seats, and then the Russians will go thru it and like, hide all the American’s toothbrushes and replace their space coffee with decaf & stuff...

[tater]

All flights from both countries will have crew from the other country. So commercial crew flights will have a cosmonaut operationally, and Soyuz flights are supposed to have an astronaut.

[CatastrophicFailure]

10 minutes ago, tater said:

All flights from both countries will have crew from the other country. So commercial crew flights will have a cosmonaut operationally, and Soyuz flights are supposed to have an astronaut.

Yeah, but this:

We haven’t purchased any additional Soyuz seats and have no plans to, since it’s probably too late anyway. After what we have runs out, I don’t think the Russian will be letting us fly for free if we don’t have an operational counterpart to trade seats with.  

[sh1pman]

40 minutes ago, CatastrophicFailure said:

Yeah, but this:

We haven’t purchased any additional Soyuz seats and have no plans to, since it’s probably too late anyway. After what we have runs out, I don’t think the Russian will be letting us fly for free if we don’t have an operational counterpart to trade seats with.  

Trade Soyuz seats for future Crew Dragon and Starliner seats? Seems fair.

Edited August 2, 2018 by sh1pman

[tater]

Operationally, they can simply hold some crew aboard for an extended stay vs their normal rotation, and they've already talked about the first crew flights being more operational in nature.