SpaceX (Vol. 2)

[tight fart]

Beati Dogu said:

Seasons 1-3 are available now. Season 4 should be out in October.

In all good record shops.

My streaming planner shows series 4 available now.

[Beati Dogu]

The question was about DVD availability.

It's October 7th, 2024 for season 4 on both DVD and Blu Ray according to Amazon.

[Dog Star]

Just having another watch of this now (for those that don’t know - you can get the “proper” SpaceX twitter/X videos a few hours late from “The Space Devs”).

Watching it again - the Superheavy booster was almost flawless - I think we will see that actually work next time. Just that Raptor relight.

The “elevator music” when Starship entered its coast phase Absolutely class.

[Beati Dogu]

https://x.com/SpaceX/status/1768745027231183184?s=...

The view of the launch from a camera on top of the tower (don't use headphones, it's quite loud).

[Stan the Bat]

\there is a launch live now.

[louiechevy]

It's amazing how easy they make rocket science look!

[fasimew]

The landing always looks fake. I know it's not, but it looks like bad CGI. Every time.

[Hammersia]

Can't quite sort out in my head what the speed readout of the booster is showing, it was similar for last nights launch as for Starship last week -

The booster combo gets up to 5000km/h before separation, the booster than flips obviously but must have momentum downrange. The speed only comes down to 4000 or so then reduces gradually as air density increases, ie never negative so not groundspeed.

So what is that speed? Always airspeed? Makes it difficult to picture how much work the booster is doing so do a quick u turn back to base or nearby.

[CraigyMc]

Hammersia said:

Can't quite sort out in my head what the speed readout of the booster is showing, it was similar for last nights launch as for Starship last week -

The booster combo gets up to 5000km/h before separation, the booster than flips obviously but must have momentum downrange. The speed only comes down to 4000 or so then reduces gradually as air density increases, ie never negative so not groundspeed.

So what is that speed? Always airspeed? Makes it difficult to picture how much work the booster is doing so do a quick u turn back to base or nearby.

It's speed as if the booster was in air. It never actually stops because it's not going straight up - at the point of booster separation it's almost horizontal. The boostback burn doesn't just cancel the speed in the direction the booster is travelling, it also makes it travel upward a little.

TL;DR it's not going from forwards into reverse gear. it's doing a 180 on a roundabout. The speed never drops to 0.

[Hondashark]

It's an arc rather than a stop and return. So it keeps the momentum just changes the trajectory.

[Dog Star]

Hammersia said:

Can't quite sort out in my head what the speed readout of the booster is showing, it was similar for last nights launch as for Starship last week -

The booster combo gets up to 5000km/h before separation, the booster than flips obviously but must have momentum downrange. The speed only comes down to 4000 or so then reduces gradually as air density increases, ie never negative so not groundspeed.

So what is that speed? Always airspeed? Makes it difficult to picture how much work the booster is doing so do a quick u turn back to base or nearby.

It’s got to be airspeed, as it shows when the rocket is in its initial vertical climb, before it pitches, where ground speed is well nigh zero, but it’ll show 600kmh etc.

Incidentally there’s quite a good NASA Spaceflight video on YouTube that came out the other day about the recovery vessels, the landing barges and so on. Has some good early Falcon 9 attempted landing videos.

[Solocle]

Hammersia said:

Can't quite sort out in my head what the speed readout of the booster is showing, it was similar for last nights launch as for Starship last week -

The booster combo gets up to 5000km/h before separation, the booster than flips obviously but must have momentum downrange. The speed only comes down to 4000 or so then reduces gradually as air density increases, ie never negative so not groundspeed.

So what is that speed? Always airspeed? Makes it difficult to picture how much work the booster is doing so do a quick u turn back to base or nearby.

I had a play with a simulated superheavy in KSP. The flight profile was far from efficient, due to the constraints of only being able to fly one vessel at a time (which I still ced up). And I had far too much fuel, hence the distinct lack of a suicide burn (but on a previous attempt, I ran out of fuel at 200 m/s on an otherwise beautiful approach).

Still, it illustrates the basics. Boostback is at 2:24.

[Hammersia]

Thanks all ^^^^^^^ that's clear now, it's a u turn and reading airspeed.

Even more mind boggling really, turning a 5000km/h 200t skyscraper around in a few seconds. My brain won't accept it, hence the question.

[Solocle]

Hammersia said:

Thanks all ^^^^^^^ that's clear now, it's a u turn and reading airspeed.

Even more mind boggling really, turning a 5000km/h 200t skyscraper around in a few seconds. My brain won't accept it, hence the question.

Well, the boostback took place in space, a bit of thrust vectoring from engines able to lift that thing when it's full of fuel with a starship on top... by the time of separation it's basically an empty tin can. At 80 km altitude, the atmosphere isn't really meaningful unless you're at orbital velocities.



Note the chart centre bottom - dynamic pressure is effectively nil.

[CraigyMc]

Solocle said:

good post, nice pics, terrible hosting of pics.

As an offtopic aside, the "upload an image (beta)" function of the PH posting form isn't a beta.
It's worked for about 20 years, and is better (more reliable) than the odd hosting website you're linking to, which isn't allowing image expansion currently.

[Solocle]

CraigyMc said:

As an offtopic aside, the "upload an image (beta)" function of the PH posting form isn't a beta.
It's worked for about 20 years, and is better (more reliable) than the odd hosting website you're linking to, which isn't allowing image expansion currently.

I know it's not a beta, but it's a convenience thing. It doesn't support copy and paste, whereas imgbb does, and for multiple images too.

Going to thumbsnap directly still doesn't do it, but at least allows drag and drop. Then you have to edit /t/ to /s/

[GTO-3R]

Sounds like flight 4 could be coming round pretty soon

[CraigyMc]

GTO-3R said:

Sounds like flight 4 could be coming round pretty soon

If Musk's anything to go by, 4,5,6,7,8,9 and 10...

April or May for IFT4 seems pretty fast though, given the gap from IFT2 to IFT3.

[Dog Star]

Solocle said:

Well, the boostback took place in space, a bit of thrust vectoring from engines able to lift that thing when it's full of fuel with a starship on top... by the time of separation it's basically an empty tin can. At 80 km altitude, the atmosphere isn't really meaningful unless you're at orbital velocities.



Note the chart centre bottom - dynamic pressure is effectively nil.

The heating glow on Starship reentry seemed to start happening on exactly 100km I noticed on IFT3.

[GTO-3R]

CraigyMc said:

GTO-3R said:

Sounds like flight 4 could be coming round pretty soon

If Musk's anything to go by, 4,5,6,7,8,9 and 10...

April or May for IFT4 seems pretty fast though, given the gap from IFT2 to IFT3.

I suppose it depends on the FAA and if they need to do another report post IFT3. If there isn't much to update/change from their side and the pad is in good health then it could happen pretty quickly! Gwynne Shotwell alluded to it being the same flight profile too so no major changes on that side either