totm nov 2023 SpaceX Discussion Thread

[tater]

 

 

?

 

Odd, when I first saw this page, and replied "?" the tweet shown was completely unrelated.

[CatastrophicFailure]

50 minutes ago, tater said:

Odd, when I first saw this page, and replied "?" the tweet shown was completely unrelated.

Gotta remember to hit refresh, old tweets get stuck in the cache or something and reloaded in the wrong place. 

[Beccab]

1 hour ago, tater said:

Tried a few browsers, faster on my phone by far.

A little faster on vivaldi and opera than firefox (usual browser), or safari.

Pretty epic, yes

 

 

 

 

 

 

 

Worth noting that now with 6 Rvac and 3 SL raptors Starship has a TWR > 1 even when fully fueled, making an abort possible during all of the  Superheavy flight (but not pad aborts, or at least very unlikely. You wouldn't want to fire 9 rocket engines directly on a tank full of methane)

Also:

 

[mikegarrison]

24 minutes ago, Beccab said:

You wouldn't want to fire 9 rocket engines directly on a tank full of methane

It works in KSP. (Most of the time.)

[Beccab]

This is more or less how it will look like now

[RealKerbal3x]

Successful Starlink launch and landing (the 11th for this booster).

Now just waiting on payload deploy.

[RCgothic]

These go up to 11 now.

 

 

Edited December 18, 2021 by RCgothic

[RCgothic]

So. So we think 6 vacuum engines on the upper stage is to make up a performance deficit, or is it just a:

"We've got the space - why not? It's 42 engines total (lol)  plus fewer tanker trips."

[Beccab]

28 minutes ago, RCgothic said:

So. So we think 6 vacuum engines on the upper stage is to make up a performance deficit, or is it just a:

"We've got the space - why not? It's 42 engines total (lol)  plus fewer tanker trips."

Well, there's a lot of benefits. As I said above TWR is decently above 1, which means that an abort has at least better than Shuttle RTLS chances of working; much less gravity losses on the current propellant load, or more propellant load with a little less gravity losses, or better isp using just 6 Rvacs instead of 3 Rvacs+3 SL on the way up; quite a lot of redundancy on the way to orbit, as it can still get to orbit with 2-3 engines out (although with 3 maybe not to target orbit); and maybe more I'm forgetting. The downsides is a bit higher Starship dry mass and not having the bottom of the ship available for additional cargo on lunar/martian landers, but maybe those will still have the 3+3 setup. It's possible and has more advantages than disadvantages, so it makes sense

[magnemoe]

6 minutes ago, Beccab said:

Well, there's a lot of benefits. As I said above TWR is decently above 1, which means that an abort has at least better than Shuttle RTLS chances of working; much less gravity losses on the current propellant load, or more propellant load with a little less gravity losses, or better isp using just 6 Rvacs instead of 3 Rvacs+3 SL on the way up; quite a lot of redundancy on the way to orbit, as it can still get to orbit with 2-3 engines out (although with 3 maybe not to target orbit); and maybe more I'm forgetting. The downsides is a bit higher Starship dry mass and not having the bottom of the ship available for additional cargo on lunar/martian landers, but maybe those will still have the 3+3 setup. It's possible and has more advantages than disadvantages, so it makes sense

Yes, better abort options and higher ISP and trust during the first part of the burn, who will especially help tanker or heavy payloads. For the moonship, this will be lighter than standard and would not really need them. 

[RCgothic]

With stretched tanks the TWR may not be improved.

 

Just been thinking - a few weeks ago, had a discussion about the world's most powerful rocket cores. Back then Starship was about 4th, behind only N1 Block A, Saturn SI-C, and SLS 5-segment SRB.

With 9 engines Starship by itself is a definite 3rd.

 

In terms of the world's most powerful rockets by thrust, 9-engine Starship by itself comes in at around 9th after Superheavy, N1, SLS, Saturn V, Energia, Long March 9 and Falcon Heavy.

[Nothalogh]

2 hours ago, RCgothic said:

So. So we think 6 vacuum engines on the upper stage is to make up a performance deficit, or is it just a:

"We've got the space - why not? It's 42 engines total (lol)  plus fewer tanker trips."

Moar TWR is better, simple as

[Minmus Taster]

3 hours ago, Beccab said:

This is more or less how it will look like now

Not much room for gimbaling but very cool!

[Beccab]

1 hour ago, RCgothic said:

With stretched tanks the TWR may not be improved.

Let's make some calculations, and please correct me where I make an error because I probably will:

- With 6 engines each having 230 metric tons of force, taking a starship with 100 tons of payload, 120 tons dry mass and 1,200 tons of propellant, the TWR is roughly 0.97, which is already better than raptor 1 but still quite restricting in abort options (you'd need to use the engines with a TWR less than 1 until you burn the first 50 ish tons of propellant, only after which TWR is above 1. Seems more doable than Shuttle RTLS, but if you can do better than this you definitely should);

- With 9 engines and same tanks as now, that would be a TWR of 1.45, which is good;

- Finally, the tank stretches. Starship upper stage can be extended of 8 meters maximum as per insider info of a few months ago, so I'll assume the worst case of 8 more meters all of which is propellant. Current starship is made in about 26 meters of propellant tanks, and increasing that to 34 meters means the propellant mass is now 1,570 tons; dry mass increase is probably negligible, but let's add 10 tons. 100 tons of payload, 130 tons dry mass and 1,570 tons of propellant with 9 Raptor 2 give a TWR of... 1.15. Not great, not terrible, and more importantly > 1, as well as likely enough for an RTLS (after all, starship has almost 7,000 m/s of delta v without tank stretches in a vacuum and remaining above 5000 m/s at sea level)

Edit: adding this here

 

Edited December 18, 2021 by Beccab

[RCgothic]

I reckon a tanker with 9 engines in the upper stage could place substantially more than 255t into LEO (based on 150t with 6 Engines) with full reuse,  not counting additional gravity losses for Superheavy's initial TWR being reduced from ~1.45 to ~1.27.

A fully expendable version could do above 410t of pure payload to LEO, again not counting additional gravity losses during Superheavy's burn.

Edited December 18, 2021 by RCgothic

[tater]

9 hours

 

[sevenperforce]

7 hours ago, Beccab said:

Edit: adding this here

 

“The hopes and fears of all the years are met in thee tonight.”

[Brotoro]

Turksat 5B coverage has music...

And Turksat 5B coverage is live.

T minus 14 minutes

Booster’s 3rd flight. Second flight for fairing.

[Brotoro]

Liftoff

MECO. Stage 2 ignition good.

Entry burn good.

Booster landed.

Both onboard and drone ship video of landing.

[Beccab]

Raptor 1 is dead, long live Raptor 2

Next up is CRS-24 in two days

[Scotius]

Mmmm. Love me some roaring Raptors in the morning. Who else thinks that SpaceX was not pushing Starship tests as hard as they could, because they are waiting for Raptor 2's to finish testing?

[Beccab]

27 minutes ago, Scotius said:

Mmmm. Love me some roaring Raptors in the morning. Who else thinks that SpaceX was not pushing Starship tests as hard as they could, because they are waiting for Raptor 2's to finish testing?

Also for the FAA, but yeah

 

Sketches showing the working of the can crusher:

[magnemoe]

1 hour ago, Scotius said:

Mmmm. Love me some roaring Raptors in the morning. Who else thinks that SpaceX was not pushing Starship tests as hard as they could, because they are waiting for Raptor 2's to finish testing?

Think hangup has been launch pad and tank farm. perhaps the stacking tower to. Now some posts above it looks like superheavy 4 is back to getting launched?
Was lots of talk last week that 4 would not fly. Anyway no reason to not go ahead with pressure testing and static fire who don't require FAA approval. 

Now if they have an lack of raptor 2 it would make more sense to expend superheavy 4, then try to catch SH 5 or 6 so they only expend the upper stage. 
Only reason not to fly SH 4 is if they feel its unsafe for the launch infrastructure compared to SH 5 or they rather launch newer versions for more relevant data. 

[tater]

 

 

 

[StrandedonEarth]

8 hours ago, Scotius said:

Mmmm. Love me some roaring Raptors in the morning.

*ghears turn*

"I love the roar of Raptors in the morning!" - Lt-Col Launchmore, Rocketpocalypse Now